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\begin{document}

\title{The Learning Curve of Robotic Coronary Arterial Bypass Surgery: A Report
From The STS Database}



\author[1]{William Patrick}%
\author[1]{Amit Iyengar}%
\author[2]{Jason Han}%
\author[1]{Jarvis Mays}%
\author[1]{Mark Helmers}%
\author[1]{John Kelly}%
\author[1]{Xingmei Wang}%
\author[3]{Mehrdad Ghoreishi}%
\author[3]{Bradley Taylor}%
\author[1]{Pavan Atluri}%
\author[1]{Nimesh Desai}%
\author[1]{Matthew Williams}%
\affil[1]{University of Pennsylvania}%
\affil[2]{Hospital of the University of Pennsylvania}%
\affil[3]{University of Maryland School of Medicine}%


\vspace{-1em}



  
  \date{May 07, 2024}


\begingroup
\let\center\flushleft
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\maketitle
\endgroup





\selectlanguage{english}
\begin{abstract}
Background: There is limited data to inform minimum case requirements
for training in robotically-assisted coronary artery bypass grafting
(RA-CABG). Current recommendations rely on non-clinical endpoints and
expert opinion. Objectives: To determine the minimum number of RA-CABG
procedures required to achieve stable clinical outcomes. Methods: We
included isolated RA-CABG in The Society of Thoracic Surgeons (STS)
registry performed between 2014 and 2019 by surgeons without prior
RA-CABG experience. Outcomes were approach conversion, reoperation,
major morbidity or mortality, and procedural success. Case sequence
number was used as a continuous variable in logistic regression with
restricted cubic splines with fixed effects. Outcomes were compared
between operations performed earlier versus later in case sequences
using unadjusted and adjusted metrics. Results: There were 1195 cases
performed by 114 surgeons. A visual inflection point occurs by a
surgeon's 10th procedure for approach conversion, major morbidity or
mortality, and overall procedural success after which outcomes
stabilize. There was a significant decrease in the rate of approach
conversion (7.7\% and 2.5\%), reoperation (18.9\% and 10.8\%), and major
morbidity or mortality (21.7\% and 12.9\%), as well as an increase in
rate of procedural success (72.9\% and 85.3\%) with increasing
experience between groups. In a multivariable logistic regression model
case sequences of \textgreater{}10 was an independent predictor of
decreased approach conversion (OR 0.27, 95\% CI 0.09 to 0.84) and
increased rate procedural success (OR 1.96, 95\% CI 1.00 to 3.84).%
\end{abstract}%



\sloppy


\textbf{The Learning Curve of Robotic Coronary Arterial Bypass Surgery:
A Report From The STS Database}

Brief title: Achieving clinical proficiency with robotic coronary
revascularization

William L. Patrick, MD \textsuperscript{a,b,c}, Amit Iyengar,
MD\textsuperscript{a}, Jason J. Han, MD\textsuperscript{a}, Jarvis C.
Mays, BA\textsuperscript{d} , Mark Helmers\textsuperscript{a}, MD, John
J. Kelly MD\textsuperscript{a}, Xingmei Wang, MS\textsuperscript{e},
Mehrdad Ghoreishi, MD\textsuperscript{f}, Bradley S. Taylor,
MD\textsuperscript{f}, Pavan Atluri, MD\textsuperscript{a}, Nimesh D.
Desai MD PhD\textsuperscript{a,b}, Matthew L. Williams,
MD\textsuperscript{a}

\textsuperscript{a} Division of Cardiovascular Surgery, University of
Pennsylvania

\textsuperscript{b} Leonard Davis Institute, University of Pennsylvania,
Philadelphia, Pennsylvania

\textsuperscript{c} Penn Cardiovascular Outcomes, Quality, \& Evaluative
Research Center, Philadelphia, Pennsylvania

\textsuperscript{d} Perelman School of Medicine, University of
Pennsylvania

\textsuperscript{e} Biostatistics Analysis Center, Perelman School of
Medicine, University of Pennsylvania

\textsuperscript{f} Division of Cardiac Surgery, University of Maryland
School of Medicine, Baltimore, MD

This work was partially funded by a National Institutes of Health T32
Training Grant (T32HL007843)

\textbf{Word Count:} 2,870

\textbf{Disclosures:} The authors have no financial disclosures

\textbf{This work was presented at the Annual Meeting of The Society of
Thoracic Surgeons, Virtual, Texas January 30 - February 2, 2021
(Virtual)}

\textbf{Address for Correspondence:}

William L. Patrick, MD

Division of Cardiothoracic Surgery

University of Pennsylvania

3400 Spruce Street

Philadelphia, PA, 19104

Phone 215-662-4000

Email: william.patrick@pennmedicine.upenn.edu

@williamlpatrick

\textbf{Acknowledgments:} None

\textbf{ABSTRACT}

\emph{Background:}

There is limited data to inform minimum case requirements for training
in robotically-assisted coronary artery bypass grafting (RA-CABG).
Current recommendations rely on non-clinical endpoints and expert
opinion.

\emph{Objectives:}

To determine the minimum number of RA-CABG procedures required to
achieve stable clinical outcomes.

\emph{Methods:}

We included isolated RA-CABG in The Society of Thoracic Surgeons (STS)
registry performed between 2014 and 2019 by surgeons without prior
RA-CABG experience. Outcomes were approach conversion, reoperation,
major morbidity or mortality, and procedural success. Case sequence
number was used as a continuous variable in logistic regression with
restricted cubic splines with fixed effects. Outcomes were compared
between operations performed earlier versus later in case sequences
using unadjusted and adjusted metrics.

\emph{Results:}

There were 1195 cases performed by 114 surgeons. A visual inflection
point occurs by a surgeon's 10th procedure for approach conversion,
major morbidity or mortality, and overall procedural success after which
outcomes stabilize. There was a significant decrease in the rate of
approach conversion (7.7\% and 2.5\%), reoperation (18.9\% and 10.8\%),
and major morbidity or mortality (21.7\% and 12.9\%), as well as an
increase in rate of procedural success (72.9\% and 85.3\%) with
increasing experience between groups. In a multivariable logistic
regression model case sequences of \textgreater{}10 was an independent
predictor of decreased approach conversion (OR 0.27, 95\% CI 0.09 to
0.84) and increased rate procedural success (OR 1.96, 95\% CI 1.00 to
3.84).

\emph{Conclusions:}

The learning curve for RA-CABG is initially steep, but stable clinical
outcomes are achieved after the 10\textsuperscript{th} procedure.

\emph{Word count:} 249

\textbf{Key words:} coronary artery disease, coronary artery
revascularization, coronary artery bypass grafting, robot, robotic,
minimally invasive, learning, learning curve, skill acquisition

\textbf{Abbreviations:}

RA-CABG, robotically-assisted coronary artery bypass grafting

AATS, American Association for Thoracic Surgery

STS, Society of Thoracic Surgeons

ACSD, Adult Cardiac Surgery Database

LIMA, left internal mammary artery

MIDCAB, minimally invasive direct CABG

TECAB, totally endoscopic robotic CABG

\textbf{INTRODUCTION}

Robotically-assisted coronary artery bypass procedures (RA-CABG) can
potentially offer numerous advantages over traditional
sternotomy.\textsuperscript{1,2} Despite this, RA-CABG represents
roughly 1\% of total CABG procedures performed in the United States and
Europe and its volume has been in decline.\textsuperscript{3} Reasons
for slow adoption might include cost, lack of institutional support,
technical demand, and lack of a formalized training regime.

In 2016, a joint Society of Thoracic Surgeons (STS) and American
Association for Thoracic Surgery (AATS) task force was created to
address the gaps in RA-CABG utilization and implementation. Optimal
surgeon training has been identified as a critical component of
procedural development across various domains. remains central to their
tasks; however, their recommendations to-date rely mostly on expert
opinion and single-institution analyses of component-specific operative
times.\textsuperscript{4} The purpose of this study is to quantify the
learning curve associated with RA CABG. As a corollary, we sought to
define how surgeon experience is related to clinical outcomes following
RA-CABG using a large national database. Understanding this learning
curve will help our community better understand how to train cardiac
surgeons to perform robotic procedures.

\textbf{METHODS}

\emph{CASE SELECTION}

We studied outcomes from all isolated RA-CABG procedures in the STS
Adult Cardiac Surgery Database (ACSD) performed between July 2014 and
June 2018 (data versions 2.81 and 2.9). Earlier versions of the ACSD do
not include a variable for operative approach conversion and were
excluded.

\emph{DETERMINATION OF CASE SEQUENCE NUMBER}

Each procedure was assigned a case sequence number that represents the
order of its occurrence within each surgeon's experience. Although
outcomes were limited to data from versions 2.81 and 2.9, operations
performed between July 2011 and July 2014 (data version 2.73) were
permitted to count towards a surgeon's case sequence number for
operations performed between July 2014 and July 2018. This was done in
order to maximize the number of eligible surgeons contributing who could
be included in the study. We eliminated all surgeons who performed [?]1
RA-CABG procedures in the four years prior to July 2011 to insure the
accuracy of case sequence numbers for the study participants (Figure 1).

For example, suppose a surgeon performed 2 RA-CABG procedures in 2007.
This surgeon would be excluded from the study because there is no way to
determine if the 2 RA-CABG procedures performed in 2007 were his/her
first and second or ninety-ninth and one-hundredth due to lack of data
prior to 2007. The ACSD does not capture the entire operative experience
surgeons in practice prior to 2007. As another example, suppose a
surgeon did not perform any RA-CABGs prior to 2011, but performed 20
RA-CABGs between July 2011 and June 2014. Unfortunately, key outcome
variables are not available in the ACSD for these 20 procedures, but
he/she has still accrued the experience 20 RA-CABG procedures. Instead
of excluding this surgeon from the study, we credited this experience
towards cases performed after July 2014, for which we had outcome data.
Therefore, if this same surgeon performed their next RA-CABG on July
4\textsuperscript{th}, 2011, this would be considered RA-CABG number 21
and the outcome of the procedure would be associated with the
21\textsuperscript{st} case sequence number, even though it was the
first of the surgeon's case series to contribute outcome data. As a
final example to illustrate the concept of case sequence, if there were
14 additional surgeons who had also performed at least 21 RA-CABG
procedures by July 4\textsuperscript{th}, 2011, then there would be a
total of 15 patients at this time who were contributing outcome data to
the 21\textsuperscript{st} case sequence.

\emph{DETERMINATION OF PROCEEDURE AND OUTCOMES}

Isolated CABG was defined in accordance with the STS. A procedure was
considered robot assisted if a robot was used during any part. Baseline
patient characteristics included in the STS 2008 CABG risk model were
used (Appendix Table 1).\textsuperscript{5} Primary outcomes were rate
of unanticipated approach conversion, reoperation, composite major
morbidity or mortality, and procedural success. Procedural success is an
inverse composite of the other three primary outcomes. Secondary
outcomes were operative mortality and prolonged length of
hospitalization. All outcomes except for procedural success are defined
in accordance with the STS (Appendix Table 2).

\emph{STATISTICAL ANALYSIS: CASE SEQUENCE AND THE VOLUME-OUTCOME
RELATIONSHIP}

Case sequence number was used as a continuous variable in univariable
logistic regression with restricted cubic splines with fixed effects.
Splines were truncated after case sequence number 25 because too few
surgeons performed more than 25 cases. The results of a type III test
with fixed effects is reported with each.

This methodology allows the ``learning curve'' associated with each
outcome to be visually represented. The slope at any given point
represents the log odds of the outcome occurring. Therefore, a point at
which the slope is steep indicates rapid change in the outcome whereas a
point at which the slope is flat indicates stability in the rate of the
outcome. Curves are visually analyzed to determine points the case
number at which stability is reached.

\emph{STATISTICAL ANALYSIS: DICHOTOMIZED CASE SEQUENCE AND THE
VOLUME-OUTCOME RELATIONSHIP}

Next, each case was categorized into two groups by surgeon case sequence
number. Group 1 is composed of patients whose procedure occurred within
a surgeon's first 10 cases and group 2 is composed of patients whose
procedure occurred after a surgeon's first 10 cases. The case number 10
was chosen based on a visually-evident inflection point in the spline
for procedural success, as described in the previous section. The rate
of each outcome was described using the appropriate descriptive
statistic and compared between groups 1 and 2 using a Chi-squared test
or t-test.

Multivariable logistic regression with case sequence number dichotomized
as [?]10 or \textgreater{}10 and surgeon as a fixed effect was performed
for each primary outcome. Variables included in the model were chosen
using stepwise selection. Statistical analysis was performed using SAS
version 9.4 (Cary, N.C.).

This project was deemed exempt from Institutional Review Board approval.
The data for this research were provided by The Society of Thoracic
Surgeons' National Database Participant User File Research Program. Data
analysis was performed at the investigators' institution(s). The results
were reviewed and approved by the STS Participant User File Adult
Cardiac Committee.

\textbf{RESULTS}

\emph{PATIENT AND SURGEON CHARACTERISTICS}

During the study period, 1,195 RA-CABGs were performed by 114 surgeons
with known sequence counts across 98 institutions. This cohort
represents 18\% (1195/6815) of RA-CABG procedures, 19\% of surgeons
(114/587), and 19\% (98/525) institutions performing RA-CABG in the ACSD
during the same time period (Appendix Figure 1). Surgeons performed a
median of 2 procedures (IQR 1 to 149). Nine surgeons performed
\textgreater{}25 procedures and 74 surgeons performed \textless{}5
(Figure 2). Baseline characteristics are shown (Table 1). Patients were
relatively young (65 \selectlanguage{ngerman}± 11 years) and predominantly male (76\%). Overall,
this cohort was healthier than usual with relatively low STS predicted
major morbidity or mortality (10\%); however, the prevalence of
comorbidities, such as chronic lung disease (25\%), peripheral vascular
disease (13\%), congestive heart failure (18\%), recent myocardial
infarction (8\%) and diabetes (59\%) was comparable to that of the
national average for a traditional CABG.\textsuperscript{5} No patients
were in cardiogenic shock prior to the operation and 19 (2\%) required a
pre-operative intra-aortic balloon pump, a rate that is less than a
third of the national average for a traditional CABG
(7\%).\textsuperscript{5} The majority of cases were performed
electively (75\%), which is a higher rate than in traditional CABG
(55\%). Emergent or salvage procedures were rare (1\%).

\emph{CLINICAL OUTCOMES}

There is a visually evident inflection point for rate of approach
conversion at approximately 8 cases, after which the learning curve
begins to flatten, but not completely (F\textsubscript{2, 691} = 3.70, p
= 0.0251) (Figure 3A). For reoperation, the inflection point is less
apparent, likely around case 8, but has not flattened by case 25
(F\textsubscript{2, 691} = 4.29, p = 0.0140) (Figure 3B). The inflection
point for composite morbidity or mortality occurs at approximately 8
cases (F\textsubscript{2,691} = 4.55, p = 0.0109) (Figure 3C). For the
composite endpoint of procedural success an inflection point is evident
around 10 cases (F\textsubscript{2,691} = 7.25, p = 0.0008) (Figure 3D).
For procedural success, major morbidity or mortality, and approach
conversion there continues to be gradual learning out to 25 cases, but
is this slow.

Cases were categorized into two groups based on surgeon case sequence
number \selectlanguage{english}[?]10 (group 1) or \textgreater{}10 (group 2). Baseline
characteristics were similar between groups with the exceptions that
Group 1 contains fewer patients and has a significantly higher rate of
chronic lung disease, insulin-dependent diabetes, hypertension, liver
disease, and is more likely to have been done urgently (Table 1).
Patients in group 1 were less likely to be completed off-pump, had
longer durations of cardiopulmonary bypass utilization, and were more
likely to receive multiple grafts than those in group 2 (Table 2).

There was a significant association between the primary outcomes and
surgeon experience group. The rate of approach conversion was 7.7\% and
2.5\% (p \textless{} 0.0001), reoperation 18.9\% and 10.8\% (p =
0.0001), and major morbidity or mortality 21.7\% and 12.9\% (p = 0.0001)
in groups 1 and 2, respectively. Correspondingly, the rate of procedural
success was 72.9\% for group 1 and 85.3\% for group 2 (p \textless{}
0.0001) (Figure 4). The overall rate operative mortality was 0.8\% and
there was no significant difference between groups. There was also no
significant difference in prolonged length of stay (Table 3).

Multivariable logistic regression with stepwise selection demonstrates
that experience of \textgreater{}10 cases is an independent predictor of
less frequent approach conversion (OR 0.27, 95\% CI 0.09 to 0.84) and
increased procedural success (OR 1.96, 95\% CI 1.00 to 3.84). Experience
group was not found to be an independent predictor of reoperation or
composite morbidity or mortality (Table 4).

\textbf{DISCUSSION}

The primary findings of this study are:

Surgeon experience is an independent predictor of RA-CABG procedural
success.

The learning curve for RA-CABG is initially steep, but consistently
flattens after a surgeon's 10\textsuperscript{th} case.

The relationship between experience and performance is natural. Its
study in the context of RA-CABG has been mostly limited to small,
single-institution, single-surgeon case-series evaluating the effect of
experience on the efficiency of procedural components. Robotic takedown
of the left internal mammary artery (LIMA) can initially take a lengthy
time, however, a period of rapid learning universally occurs with an
inflection point between 5-15 cases with stabilization
thereafter.\textsuperscript{6-9} Efficiency of port placement, speed of
LIMA to coronary artery anastomosis, and total operative times show a
similar trend.\textsuperscript{7-10} Learning curves for similar
endpoints have been observed in other fields such as robotic cystectomy,
prostatectomy, and transoral surgery. \textsuperscript{11-13}

This study demonstrates that the learning curve has significant
implications for clinical outcomes in addition to procedural efficiency.
We found clear inflection points for rates of approach conversion, major
morbidity and mortality, and procedural success (Figure 3A, 3C, 3D). For
each, stability is achieved after about the 10\textsuperscript{th} case,
with slow improvement beyond case 25. In contrast, an inflection point
for reoperation is less evident and the curve is not stable by case 25
(Figure 3B).

This finding was reinforced when outcomes were dichotomized as within
the first 10 cases or beyond the first 10. Rate of adverse outcomes
declined and that of procedural success increased with experience
(Figure 4). The rate of adverse events in the less experienced group was
high, but consistent with other reports of early experience. Our rate of
approach conversion was consistent with the rates reported in other
series of 0-11.5\%, although definitions vary in the
literature.\textsuperscript{8,10,14,15}

We report a relatively high rate of reoperation in both experience
groups; however, our definition is inclusive not only of reoperation for
hemorrhage but also of graft occlusion, myocardial ischemia, and valve
or aortic issues. The rate of major morbidity or mortality observed in
the experienced surgeon group (12.9\%) is similar to the overall rate
previously reported in the STS ACSD for nearly 10,000 RA-CABG procedures
(10.2\%). Finally, a procedural success rate of 85.3\% is disappointing,
even for more experienced surgeons, but has precedent. In a 500-case
series of totally endoscopic RA-CABG procedural success (similarly
defined as no conversion or major adverse cardiac or cerebral events)
was achieved in only 80\% of cases.\textsuperscript{16}

Notably, surgeon experience in multivariable analysis was not an
independent predictor of major morbidity or mortality. This may be due
to the higher incidence of some comorbidities among patients in the
lower experience group (Table 1). It may also be due to successful
rescue by conversion to open, which was higher in earlier sequence
numbers.

Because most surgeons are comfortable with traditional approaches to
CABG, learned and practice during traditional training curriculums, the
learning curve for RA-CABG consists gaining competence with the robotic
interface and set-up. For this reason, experience with other
non-traditional approaches, for instance robotically-assisted mitral
valve procedures, is likely to expedite the learning curve for RA-CABG.
Additionally, the experience of other team members including bedside
assistants, anesthesiologists, perfusionists, and nursing staff also
contributes to clinical outcomes. Finally, the higher comorbidity burden
observed in the lower experience group may hint at the possibility that
patient selection, though non-procedural, is an important aspect of the
learning curve.

This study has several limitations. Only variables captured in the ACSD
can be adjusted for in multivariable analyses, so it is possible that
uncaptured variables could be confounding the association between
surgeon experience and outcomes. Importantly, the extent of robotic
utilization was not able to be determined from the STS ACSD, making
distinctions between minimally invasive direct CABG (MIDCAB), totally
endoscopic robotic CABG (TECAB), or hybrid procedures unreliable.
Furthermore, we do not know if cases were proctored. The effect of
hospital experience could not be accounted for as a fixed effect because
of non-convergence.

\emph{CONCLUSION}

The potential advantages of RA-CABG to the patient include shorter
length of hospitalization, less post-operative pain and higher quality
of life, and improved cosmesis.\textsuperscript{1,16} Given outcomes
equivalent to non-RA-CABG, RA-CABG will continue to be an enticing
strategy.\textsuperscript{1,17} Robotic technology will continue to
improve, incorporating haptic feedback, visualization coregistration,
remote proctoring, and more. Market forces are an incentive for
increased robot utilization in coronary surgery. Despite this
opportunity the number of RA-CABG and surgeons performing them has been
in almost constant decline since 2011 (Appendix Figure). We show that
the learning curve is steep, but flattens after approximately 10 cases.
With informed guidance and a standardized curriculum it is likely that
cardiac surgeons can become safely trained in RA-CABG. We have
demonstrated that in the current environment, negotiation of the
learning curve is associated with an increase in adverse outcomes in
RA-CABG.

\textbf{REFERENCES}

1. Whellan DJ, McCarey MM, Taylor BS, et al. Trends in Robotic-Assisted
Coronary Artery Bypass Grafts: A Study of The Society of Thoracic
Surgeons Adult Cardiac Surgery Database, 2006 to 2012. Ann Thorac Surg
2016;102:140-6.

2. Bonaros N, Schachner T, Wiedemann D, et al. Quality of life
improvement after robotically assisted coronary artery bypass grafting.
Cardiology 2009;114:59-66.

3. Pettinari M, Navarra E, Noirhomme P, Gutermann H. The state of
robotic cardiac surgery in Europe. Ann Cardiothorac Surg 2017;6:1-8.

4. Rodriguez E, Nifong LW, Bonatti J, et al. Pathway for surgeons and
programs to establish and maintain a successful robot-assisted adult
cardiac surgery program. J Thorac Cardiovasc Surg 2016;152:9-13.

5. Shahian DM, O'Brien SM, Filardo G, et al. The Society of Thoracic
Surgeons 2008 cardiac surgery risk models: part 1--coronary artery
bypass grafting surgery. Ann Thorac Surg 2009;88:S2-22.

6. Oehlinger A, Bonaros N, Schachner T, et al. Robotic endoscopic left
internal mammary artery harvesting: what have we learned after 100
cases? Ann Thorac Surg 2007;83:1030-4.

7. Bonatti J, Schachner T, Bernecker O, et al. Robotic totally
endoscopic coronary artery bypass: program development and learning
curve issues. J Thorac Cardiovasc Surg 2004;127:504-10.

8. Hemli JM, Henn LW, Panetta CR, et al. Defining the learning curve for
robotic-assisted endoscopic harvesting of the left internal mammary
artery. Innovations (Phila) 2013;8:353-8.

9. Cheng N, Gao C, Yang M, Wu Y, Wang G, Xiao C. Analysis of the
learning curve for beating heart, totally endoscopic, coronary artery
bypass grafting. J Thorac Cardiovasc Surg 2014;148:1832-6.

10. Argenziano M, Katz M, Bonatti J, et al. Results of the prospective
multicenter trial of robotically assisted totally endoscopic coronary
artery bypass grafting. Ann Thorac Surg 2006;81:1666-74; discussion
74-5.

11. Hayn MH, Hussain A, Mansour AM, et al. The learning curve of
robot-assisted radical cystectomy: results from the International
Robotic Cystectomy Consortium. Eur Urol 2010;58:197-202.

12. Kaul S, Shah NL, Menon M. Learning curve using robotic surgery. Curr
Urol Rep 2006;7:125-9.

13. White HN, Frederick J, Zimmerman T, Carroll WR, Magnuson JS.
Learning curve for transoral robotic surgery: a 4-year analysis. JAMA
Otolaryngol Head Neck Surg 2013;139:564-7.

14. Gobolos L, Ramahi J, Obeso A, et al. Robotic Totally Endoscopic
Coronary Artery Bypass Grafting: Systematic Review of Clinical Outcomes
from the Past two Decades. Innovations (Phila) 2019;14:5-16.

15. Kappert U, Cichon R, Schneider J, et al. Robotic coronary artery
surgery--the evolution of a new minimally invasive approach in coronary
artery surgery. Thorac Cardiovasc Surg 2000;48:193-7.

16. Bonaros N, Schachner T, Lehr E, et al. Five hundred cases of robotic
totally endoscopic coronary artery bypass grafting: predictors of
success and safety. Ann Thorac Surg 2013;95:803-12.

17. Yanagawa F, Perez M, Bell T, Grim R, Martin J, Ahuja V. Critical
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2015;150:771-7.

\textbf{FIGURES}

\textbf{Figure 1.} Methodology for determining surgeon case-sequence
number and cases analyzed.

\textbf{Figure 2.} Total number of robotically-assisted CABG performed
by each surgeon.

\textbf{Figure 3.} Learning curves for robotically-assisted CABG for
each clinical endpoint.

\textbf{Figure 4.} Rate of clinical endpoint for robotically-assisted
CABG performed later in a sequence (\textgreater{}10 cases) versus
earlier (\selectlanguage{english}[?]10 cases).

\textbf{TABLES}

\textbf{Table 1.} Baseline characteristics of the study population\selectlanguage{english}
\begin{longtable}[]{@{}lllll@{}}
\toprule
\begin{minipage}[b]{0.19\columnwidth}\raggedright\strut
\textbf{Characteristic}\strut
\end{minipage} & \begin{minipage}[b]{0.19\columnwidth}\raggedright\strut
\textbf{All n = 1195}\strut
\end{minipage} & \begin{minipage}[b]{0.19\columnwidth}\raggedright\strut
\textbf{Group 1 ([?]10)} \textbf{n = 465}\strut
\end{minipage} & \begin{minipage}[b]{0.19\columnwidth}\raggedright\strut
\textbf{Group 2} \textbf{(\textgreater{}10) n = 730}\strut
\end{minipage} & \begin{minipage}[b]{0.19\columnwidth}\raggedright\strut
\textbf{p-value}\strut
\end{minipage}\tabularnewline
\midrule
\endhead
\begin{minipage}[t]{0.17\columnwidth}\raggedright\strut
Age - yr\strut
\end{minipage} & \begin{minipage}[t]{0.17\columnwidth}\raggedright\strut
64.7 +/- 11.0\strut
\end{minipage} & \begin{minipage}[t]{0.17\columnwidth}\raggedright\strut
64.6 +/- 11.1\strut
\end{minipage} & \begin{minipage}[t]{0.17\columnwidth}\raggedright\strut
64.8 +/- 10.9\strut
\end{minipage} & \begin{minipage}[t]{0.17\columnwidth}\raggedright\strut
0.7417\strut
\end{minipage}\tabularnewline
\begin{minipage}[t]{0.17\columnwidth}\raggedright\strut
Male - no. (\%)\strut
\end{minipage} & \begin{minipage}[t]{0.17\columnwidth}\raggedright\strut
913 (76.4)\strut
\end{minipage} & \begin{minipage}[t]{0.17\columnwidth}\raggedright\strut
356 (76.6)\strut
\end{minipage} & \begin{minipage}[t]{0.17\columnwidth}\raggedright\strut
557 (76.3)\strut
\end{minipage} & \begin{minipage}[t]{0.17\columnwidth}\raggedright\strut
0.9185\strut
\end{minipage}\tabularnewline
\begin{minipage}[t]{0.17\columnwidth}\raggedright\strut
Ejection fraction - fraction\strut
\end{minipage} & \begin{minipage}[t]{0.17\columnwidth}\raggedright\strut
52.5 +/- 11.9\strut
\end{minipage} & \begin{minipage}[t]{0.17\columnwidth}\raggedright\strut
51.5 +/- 13.7\strut
\end{minipage} & \begin{minipage}[t]{0.17\columnwidth}\raggedright\strut
52.9 +/- 10.9\strut
\end{minipage} & \begin{minipage}[t]{0.17\columnwidth}\raggedright\strut
0.2977\strut
\end{minipage}\tabularnewline
\begin{minipage}[t]{0.17\columnwidth}\raggedright\strut
Body surface area - m\textsuperscript{2}\strut
\end{minipage} & \begin{minipage}[t]{0.17\columnwidth}\raggedright\strut
2.0 +/- 0.2\strut
\end{minipage} & \begin{minipage}[t]{0.17\columnwidth}\raggedright\strut
2.0 +/- 0.2\strut
\end{minipage} & \begin{minipage}[t]{0.17\columnwidth}\raggedright\strut
2.0 +/- 0.3\strut
\end{minipage} & \begin{minipage}[t]{0.17\columnwidth}\raggedright\strut
0.2549\strut
\end{minipage}\tabularnewline
\begin{minipage}[t]{0.17\columnwidth}\raggedright\strut
Creatinine - mg/dL\strut
\end{minipage} & \begin{minipage}[t]{0.17\columnwidth}\raggedright\strut
1.1 +/- 0.7\strut
\end{minipage} & \begin{minipage}[t]{0.17\columnwidth}\raggedright\strut
1.1 +/- 0.6\strut
\end{minipage} & \begin{minipage}[t]{0.17\columnwidth}\raggedright\strut
1.1 +/- 0.8\strut
\end{minipage} & \begin{minipage}[t]{0.17\columnwidth}\raggedright\strut
0.9144\strut
\end{minipage}\tabularnewline
\begin{minipage}[t]{0.17\columnwidth}\raggedright\strut
Dialysis - no. (\%)\strut
\end{minipage} & \begin{minipage}[t]{0.17\columnwidth}\raggedright\strut
13 (1.1)\strut
\end{minipage} & \begin{minipage}[t]{0.17\columnwidth}\raggedright\strut
6 (1.3)\strut
\end{minipage} & \begin{minipage}[t]{0.17\columnwidth}\raggedright\strut
7 (1.0)\strut
\end{minipage} & \begin{minipage}[t]{0.17\columnwidth}\raggedright\strut
0.5903\strut
\end{minipage}\tabularnewline
\begin{minipage}[t]{0.17\columnwidth}\raggedright\strut
Arrythmia - no. (\%)\strut
\end{minipage} & \begin{minipage}[t]{0.17\columnwidth}\raggedright\strut
155 (13.0)\strut
\end{minipage} & \begin{minipage}[t]{0.17\columnwidth}\raggedright\strut
62 (13.3)\strut
\end{minipage} & \begin{minipage}[t]{0.17\columnwidth}\raggedright\strut
93 (12.7)\strut
\end{minipage} & \begin{minipage}[t]{0.17\columnwidth}\raggedright\strut
0.7659\strut
\end{minipage}\tabularnewline
\begin{minipage}[t]{0.17\columnwidth}\raggedright\strut
Shock - no. (\%)\strut
\end{minipage} & \begin{minipage}[t]{0.17\columnwidth}\raggedright\strut
0.0 (0.0)\strut
\end{minipage} & \begin{minipage}[t]{0.17\columnwidth}\raggedright\strut
0.0 (0.0)\strut
\end{minipage} & \begin{minipage}[t]{0.17\columnwidth}\raggedright\strut
0.0 (0.0)\strut
\end{minipage} & \begin{minipage}[t]{0.17\columnwidth}\raggedright\strut
NA\strut
\end{minipage}\tabularnewline
\begin{minipage}[t]{0.17\columnwidth}\raggedright\strut
Pre-operative IABP\strut
\end{minipage} & \begin{minipage}[t]{0.17\columnwidth}\raggedright\strut
19 (1.6)\strut
\end{minipage} & \begin{minipage}[t]{0.17\columnwidth}\raggedright\strut
11 (2.4)\strut
\end{minipage} & \begin{minipage}[t]{0.17\columnwidth}\raggedright\strut
8 (1.1)\strut
\end{minipage} & \begin{minipage}[t]{0.17\columnwidth}\raggedright\strut
0.0871\strut
\end{minipage}\tabularnewline
\begin{minipage}[t]{0.17\columnwidth}\raggedright\strut
Hypertension - no. (\%)\strut
\end{minipage} & \begin{minipage}[t]{0.17\columnwidth}\raggedright\strut
1045 (87.4)\strut
\end{minipage} & \begin{minipage}[t]{0.17\columnwidth}\raggedright\strut
388 (83.4)\strut
\end{minipage} & \begin{minipage}[t]{0.17\columnwidth}\raggedright\strut
657 (90.0)\strut
\end{minipage} & \begin{minipage}[t]{0.17\columnwidth}\raggedright\strut
0.0009\strut
\end{minipage}\tabularnewline
\begin{minipage}[t]{0.17\columnwidth}\raggedright\strut
Immunosuppression - no. (\%)\strut
\end{minipage} & \begin{minipage}[t]{0.17\columnwidth}\raggedright\strut
39 (3.3)\strut
\end{minipage} & \begin{minipage}[t]{0.17\columnwidth}\raggedright\strut
18 (3.9)\strut
\end{minipage} & \begin{minipage}[t]{0.17\columnwidth}\raggedright\strut
21 (2.9\%)\strut
\end{minipage} & \begin{minipage}[t]{0.17\columnwidth}\raggedright\strut
0.3456\strut
\end{minipage}\tabularnewline
\begin{minipage}[t]{0.17\columnwidth}\raggedright\strut
Prior PCI - no. (\%)\strut
\end{minipage} & \begin{minipage}[t]{0.17\columnwidth}\raggedright\strut
505 (42.3)\strut
\end{minipage} & \begin{minipage}[t]{0.17\columnwidth}\raggedright\strut
192 (41.3)\strut
\end{minipage} & \begin{minipage}[t]{0.17\columnwidth}\raggedright\strut
313 (42.9)\strut
\end{minipage} & \begin{minipage}[t]{0.17\columnwidth}\raggedright\strut
0.5883\strut
\end{minipage}\tabularnewline
\begin{minipage}[t]{0.17\columnwidth}\raggedright\strut
PVD - no. (\%)\strut
\end{minipage} & \begin{minipage}[t]{0.17\columnwidth}\raggedright\strut
149 (12.5)\strut
\end{minipage} & \begin{minipage}[t]{0.17\columnwidth}\raggedright\strut
54 (11.6)\strut
\end{minipage} & \begin{minipage}[t]{0.17\columnwidth}\raggedright\strut
95 (13.0)\strut
\end{minipage} & \begin{minipage}[t]{0.17\columnwidth}\raggedright\strut
0.4748\strut
\end{minipage}\tabularnewline
\begin{minipage}[t]{0.17\columnwidth}\raggedright\strut
Left main CAD - no. (\%)\strut
\end{minipage} & \begin{minipage}[t]{0.17\columnwidth}\raggedright\strut
85 (7.1)\strut
\end{minipage} & \begin{minipage}[t]{0.17\columnwidth}\raggedright\strut
35 (7.5)\strut
\end{minipage} & \begin{minipage}[t]{0.17\columnwidth}\raggedright\strut
50 (6.8)\strut
\end{minipage} & \begin{minipage}[t]{0.17\columnwidth}\raggedright\strut
0.6568\strut
\end{minipage}\tabularnewline
\begin{minipage}[t]{0.17\columnwidth}\raggedright\strut
Aortic stenosis - no. (\%)\strut
\end{minipage} & \begin{minipage}[t]{0.17\columnwidth}\raggedright\strut
36 (3.0)\strut
\end{minipage} & \begin{minipage}[t]{0.17\columnwidth}\raggedright\strut
14 (3.0)\strut
\end{minipage} & \begin{minipage}[t]{0.17\columnwidth}\raggedright\strut
22 (3.0)\strut
\end{minipage} & \begin{minipage}[t]{0.17\columnwidth}\raggedright\strut
0.9977\strut
\end{minipage}\tabularnewline
\begin{minipage}[t]{0.17\columnwidth}\raggedright\strut
Aortic insufficiency - no. (\%)\strut
\end{minipage} & \begin{minipage}[t]{0.17\columnwidth}\raggedright\strut
127 (10.6)\strut
\end{minipage} & \begin{minipage}[t]{0.17\columnwidth}\raggedright\strut
63 (13.5)\strut
\end{minipage} & \begin{minipage}[t]{0.17\columnwidth}\raggedright\strut
64 (8.8)\strut
\end{minipage} & \begin{minipage}[t]{0.17\columnwidth}\raggedright\strut
0.0089\strut
\end{minipage}\tabularnewline
\begin{minipage}[t]{0.17\columnwidth}\raggedright\strut
Mitral insufficiency - no. (\%)\strut
\end{minipage} & \begin{minipage}[t]{0.17\columnwidth}\raggedright\strut
331 (27.7)\strut
\end{minipage} & \begin{minipage}[t]{0.17\columnwidth}\raggedright\strut
128 (27.5)\strut
\end{minipage} & \begin{minipage}[t]{0.17\columnwidth}\raggedright\strut
203 (27.8)\strut
\end{minipage} & \begin{minipage}[t]{0.17\columnwidth}\raggedright\strut
0.9156\strut
\end{minipage}\tabularnewline
\begin{minipage}[t]{0.17\columnwidth}\raggedright\strut
Tricuspid insufficiency - no. (\%)\strut
\end{minipage} & \begin{minipage}[t]{0.17\columnwidth}\raggedright\strut
933 (78.1)\strut
\end{minipage} & \begin{minipage}[t]{0.17\columnwidth}\raggedright\strut
361 (77.6)\strut
\end{minipage} & \begin{minipage}[t]{0.17\columnwidth}\raggedright\strut
572 (78.4)\strut
\end{minipage} & \begin{minipage}[t]{0.17\columnwidth}\raggedright\strut
0.7688\strut
\end{minipage}\tabularnewline
\begin{minipage}[t]{0.17\columnwidth}\raggedright\strut
Chronic lung disease - no. (\%)\strut
\end{minipage} & \begin{minipage}[t]{0.17\columnwidth}\raggedright\strut
\strut
\end{minipage} & \begin{minipage}[t]{0.17\columnwidth}\raggedright\strut
\strut
\end{minipage} & \begin{minipage}[t]{0.17\columnwidth}\raggedright\strut
\strut
\end{minipage} & \begin{minipage}[t]{0.17\columnwidth}\raggedright\strut
0.0106\strut
\end{minipage}\tabularnewline
\begin{minipage}[t]{0.17\columnwidth}\raggedright\strut
none\strut
\end{minipage} & \begin{minipage}[t]{0.17\columnwidth}\raggedright\strut
112 (9.4)\strut
\end{minipage} & \begin{minipage}[t]{0.17\columnwidth}\raggedright\strut
36 (7.7)\strut
\end{minipage} & \begin{minipage}[t]{0.17\columnwidth}\raggedright\strut
76 (10.4)\strut
\end{minipage} & \begin{minipage}[t]{0.17\columnwidth}\raggedright\strut
-\strut
\end{minipage}\tabularnewline
\begin{minipage}[t]{0.17\columnwidth}\raggedright\strut
mild\strut
\end{minipage} & \begin{minipage}[t]{0.17\columnwidth}\raggedright\strut
37 (3.1)\strut
\end{minipage} & \begin{minipage}[t]{0.17\columnwidth}\raggedright\strut
23 (4.9)\strut
\end{minipage} & \begin{minipage}[t]{0.17\columnwidth}\raggedright\strut
14 (1.9)\strut
\end{minipage} & \begin{minipage}[t]{0.17\columnwidth}\raggedright\strut
-\strut
\end{minipage}\tabularnewline
\begin{minipage}[t]{0.17\columnwidth}\raggedright\strut
moderate\strut
\end{minipage} & \begin{minipage}[t]{0.17\columnwidth}\raggedright\strut
28 (2.3)\strut
\end{minipage} & \begin{minipage}[t]{0.17\columnwidth}\raggedright\strut
9 (1.9)\strut
\end{minipage} & \begin{minipage}[t]{0.17\columnwidth}\raggedright\strut
19 (2.6)\strut
\end{minipage} & \begin{minipage}[t]{0.17\columnwidth}\raggedright\strut
-\strut
\end{minipage}\tabularnewline
\begin{minipage}[t]{0.17\columnwidth}\raggedright\strut
severe\strut
\end{minipage} & \begin{minipage}[t]{0.17\columnwidth}\raggedright\strut
229 (19.2)\strut
\end{minipage} & \begin{minipage}[t]{0.17\columnwidth}\raggedright\strut
93 (20.0)\strut
\end{minipage} & \begin{minipage}[t]{0.17\columnwidth}\raggedright\strut
136 (18.6)\strut
\end{minipage} & \begin{minipage}[t]{0.17\columnwidth}\raggedright\strut
-\strut
\end{minipage}\tabularnewline
\begin{minipage}[t]{0.17\columnwidth}\raggedright\strut
CVD/CVA - no. (\%)\strut
\end{minipage} & \begin{minipage}[t]{0.17\columnwidth}\raggedright\strut
\strut
\end{minipage} & \begin{minipage}[t]{0.17\columnwidth}\raggedright\strut
\strut
\end{minipage} & \begin{minipage}[t]{0.17\columnwidth}\raggedright\strut
\strut
\end{minipage} & \begin{minipage}[t]{0.17\columnwidth}\raggedright\strut
0.6113\strut
\end{minipage}\tabularnewline
\begin{minipage}[t]{0.17\columnwidth}\raggedright\strut
no CVD\strut
\end{minipage} & \begin{minipage}[t]{0.17\columnwidth}\raggedright\strut
975 (81.6)\strut
\end{minipage} & \begin{minipage}[t]{0.17\columnwidth}\raggedright\strut
384 (82.6)\strut
\end{minipage} & \begin{minipage}[t]{0.17\columnwidth}\raggedright\strut
591 (81.0)\strut
\end{minipage} & \begin{minipage}[t]{0.17\columnwidth}\raggedright\strut
-\strut
\end{minipage}\tabularnewline
\begin{minipage}[t]{0.17\columnwidth}\raggedright\strut
CVD without CVA\strut
\end{minipage} & \begin{minipage}[t]{0.17\columnwidth}\raggedright\strut
139 (11.6)\strut
\end{minipage} & \begin{minipage}[t]{0.17\columnwidth}\raggedright\strut
50 (10.8)\strut
\end{minipage} & \begin{minipage}[t]{0.17\columnwidth}\raggedright\strut
89 (12.2)\strut
\end{minipage} & \begin{minipage}[t]{0.17\columnwidth}\raggedright\strut
-\strut
\end{minipage}\tabularnewline
\begin{minipage}[t]{0.17\columnwidth}\raggedright\strut
CVD with CVA\strut
\end{minipage} & \begin{minipage}[t]{0.17\columnwidth}\raggedright\strut
81 (6.8)\strut
\end{minipage} & \begin{minipage}[t]{0.17\columnwidth}\raggedright\strut
31 (6.7)\strut
\end{minipage} & \begin{minipage}[t]{0.17\columnwidth}\raggedright\strut
50 (6.8)\strut
\end{minipage} & \begin{minipage}[t]{0.17\columnwidth}\raggedright\strut
-\strut
\end{minipage}\tabularnewline
\begin{minipage}[t]{0.17\columnwidth}\raggedright\strut
Diabetes mellitus - no. (\%)\strut
\end{minipage} & \begin{minipage}[t]{0.17\columnwidth}\raggedright\strut
\strut
\end{minipage} & \begin{minipage}[t]{0.17\columnwidth}\raggedright\strut
\strut
\end{minipage} & \begin{minipage}[t]{0.17\columnwidth}\raggedright\strut
\strut
\end{minipage} & \begin{minipage}[t]{0.17\columnwidth}\raggedright\strut
0.0126\strut
\end{minipage}\tabularnewline
\begin{minipage}[t]{0.17\columnwidth}\raggedright\strut
no diabetes\strut
\end{minipage} & \begin{minipage}[t]{0.17\columnwidth}\raggedright\strut
484 (40.5)\strut
\end{minipage} & \begin{minipage}[t]{0.17\columnwidth}\raggedright\strut
167 (35.9)\strut
\end{minipage} & \begin{minipage}[t]{0.17\columnwidth}\raggedright\strut
317 (43.4)\strut
\end{minipage} & \begin{minipage}[t]{0.17\columnwidth}\raggedright\strut
-\strut
\end{minipage}\tabularnewline
\begin{minipage}[t]{0.17\columnwidth}\raggedright\strut
diabetes not insulin dependent\strut
\end{minipage} & \begin{minipage}[t]{0.17\columnwidth}\raggedright\strut
514 (43.0)\strut
\end{minipage} & \begin{minipage}[t]{0.17\columnwidth}\raggedright\strut
207 (44.5)\strut
\end{minipage} & \begin{minipage}[t]{0.17\columnwidth}\raggedright\strut
307 (42.1)\strut
\end{minipage} & \begin{minipage}[t]{0.17\columnwidth}\raggedright\strut
-\strut
\end{minipage}\tabularnewline
\begin{minipage}[t]{0.17\columnwidth}\raggedright\strut
diabetes insulin dependent\strut
\end{minipage} & \begin{minipage}[t]{0.17\columnwidth}\raggedright\strut
197 (16.5)\strut
\end{minipage} & \begin{minipage}[t]{0.17\columnwidth}\raggedright\strut
91 (19.6)\strut
\end{minipage} & \begin{minipage}[t]{0.17\columnwidth}\raggedright\strut
106 (14.5)\strut
\end{minipage} & \begin{minipage}[t]{0.17\columnwidth}\raggedright\strut
-\strut
\end{minipage}\tabularnewline
\begin{minipage}[t]{0.17\columnwidth}\raggedright\strut
Myocardial infarction - no. (\%)\strut
\end{minipage} & \begin{minipage}[t]{0.17\columnwidth}\raggedright\strut
\strut
\end{minipage} & \begin{minipage}[t]{0.17\columnwidth}\raggedright\strut
\strut
\end{minipage} & \begin{minipage}[t]{0.17\columnwidth}\raggedright\strut
\strut
\end{minipage} & \begin{minipage}[t]{0.17\columnwidth}\raggedright\strut
0.5464\strut
\end{minipage}\tabularnewline
\begin{minipage}[t]{0.17\columnwidth}\raggedright\strut
MI [?] 6 hours\strut
\end{minipage} & \begin{minipage}[t]{0.17\columnwidth}\raggedright\strut
2 (0.2)\strut
\end{minipage} & \begin{minipage}[t]{0.17\columnwidth}\raggedright\strut
2 (0.4)\strut
\end{minipage} & \begin{minipage}[t]{0.17\columnwidth}\raggedright\strut
0.0 (0.0)\strut
\end{minipage} & \begin{minipage}[t]{0.17\columnwidth}\raggedright\strut
-\strut
\end{minipage}\tabularnewline
\begin{minipage}[t]{0.17\columnwidth}\raggedright\strut
MI \textgreater{}6 or \textless{}24 hours\strut
\end{minipage} & \begin{minipage}[t]{0.17\columnwidth}\raggedright\strut
2 (0.2)\strut
\end{minipage} & \begin{minipage}[t]{0.17\columnwidth}\raggedright\strut
0.0 (0.0)\strut
\end{minipage} & \begin{minipage}[t]{0.17\columnwidth}\raggedright\strut
2 (0.3)\strut
\end{minipage} & \begin{minipage}[t]{0.17\columnwidth}\raggedright\strut
-\strut
\end{minipage}\tabularnewline
\begin{minipage}[t]{0.17\columnwidth}\raggedright\strut
MI 1 to 21 days\strut
\end{minipage} & \begin{minipage}[t]{0.17\columnwidth}\raggedright\strut
95 (7.9)\strut
\end{minipage} & \begin{minipage}[t]{0.17\columnwidth}\raggedright\strut
34 (7.3)\strut
\end{minipage} & \begin{minipage}[t]{0.17\columnwidth}\raggedright\strut
61 (8.4)\strut
\end{minipage} & \begin{minipage}[t]{0.17\columnwidth}\raggedright\strut
-\strut
\end{minipage}\tabularnewline
\begin{minipage}[t]{0.17\columnwidth}\raggedright\strut
Race - no. (\%)\strut
\end{minipage} & \begin{minipage}[t]{0.17\columnwidth}\raggedright\strut
\strut
\end{minipage} & \begin{minipage}[t]{0.17\columnwidth}\raggedright\strut
\strut
\end{minipage} & \begin{minipage}[t]{0.17\columnwidth}\raggedright\strut
\strut
\end{minipage} & \begin{minipage}[t]{0.17\columnwidth}\raggedright\strut
0.4649\strut
\end{minipage}\tabularnewline
\begin{minipage}[t]{0.17\columnwidth}\raggedright\strut
black\strut
\end{minipage} & \begin{minipage}[t]{0.17\columnwidth}\raggedright\strut
86 (7.2)\strut
\end{minipage} & \begin{minipage}[t]{0.17\columnwidth}\raggedright\strut
31 (6.7)\strut
\end{minipage} & \begin{minipage}[t]{0.17\columnwidth}\raggedright\strut
55 (7.5)\strut
\end{minipage} & \begin{minipage}[t]{0.17\columnwidth}\raggedright\strut
-\strut
\end{minipage}\tabularnewline
\begin{minipage}[t]{0.17\columnwidth}\raggedright\strut
asian\strut
\end{minipage} & \begin{minipage}[t]{0.17\columnwidth}\raggedright\strut
39 (3.3)\strut
\end{minipage} & \begin{minipage}[t]{0.17\columnwidth}\raggedright\strut
18 (3.9)\strut
\end{minipage} & \begin{minipage}[t]{0.17\columnwidth}\raggedright\strut
21 (2.9)\strut
\end{minipage} & \begin{minipage}[t]{0.17\columnwidth}\raggedright\strut
-\strut
\end{minipage}\tabularnewline
\begin{minipage}[t]{0.17\columnwidth}\raggedright\strut
white\strut
\end{minipage} & \begin{minipage}[t]{0.17\columnwidth}\raggedright\strut
1012 (84.7)\strut
\end{minipage} & \begin{minipage}[t]{0.17\columnwidth}\raggedright\strut
390 (83.9)\strut
\end{minipage} & \begin{minipage}[t]{0.17\columnwidth}\raggedright\strut
622 (85.2)\strut
\end{minipage} & \begin{minipage}[t]{0.17\columnwidth}\raggedright\strut
-\strut
\end{minipage}\tabularnewline
\begin{minipage}[t]{0.17\columnwidth}\raggedright\strut
hispanic\strut
\end{minipage} & \begin{minipage}[t]{0.17\columnwidth}\raggedright\strut
27 (2.3)\strut
\end{minipage} & \begin{minipage}[t]{0.17\columnwidth}\raggedright\strut
7 (1.5)\strut
\end{minipage} & \begin{minipage}[t]{0.17\columnwidth}\raggedright\strut
20 (2.7)\strut
\end{minipage} & \begin{minipage}[t]{0.17\columnwidth}\raggedright\strut
-\strut
\end{minipage}\tabularnewline
\begin{minipage}[t]{0.17\columnwidth}\raggedright\strut
other\strut
\end{minipage} & \begin{minipage}[t]{0.17\columnwidth}\raggedright\strut
31 (2.6)\strut
\end{minipage} & \begin{minipage}[t]{0.17\columnwidth}\raggedright\strut
19 (4.1)\strut
\end{minipage} & \begin{minipage}[t]{0.17\columnwidth}\raggedright\strut
12 (1.6)\strut
\end{minipage} & \begin{minipage}[t]{0.17\columnwidth}\raggedright\strut
-\strut
\end{minipage}\tabularnewline
\begin{minipage}[t]{0.17\columnwidth}\raggedright\strut
Status - no. (\%)\strut
\end{minipage} & \begin{minipage}[t]{0.17\columnwidth}\raggedright\strut
\strut
\end{minipage} & \begin{minipage}[t]{0.17\columnwidth}\raggedright\strut
\strut
\end{minipage} & \begin{minipage}[t]{0.17\columnwidth}\raggedright\strut
\strut
\end{minipage} & \begin{minipage}[t]{0.17\columnwidth}\raggedright\strut
0.0102\strut
\end{minipage}\tabularnewline
\begin{minipage}[t]{0.17\columnwidth}\raggedright\strut
elective\strut
\end{minipage} & \begin{minipage}[t]{0.17\columnwidth}\raggedright\strut
893 (74.7)\strut
\end{minipage} & \begin{minipage}[t]{0.17\columnwidth}\raggedright\strut
328 (70.5)\strut
\end{minipage} & \begin{minipage}[t]{0.17\columnwidth}\raggedright\strut
565 (77.4)\strut
\end{minipage} & \begin{minipage}[t]{0.17\columnwidth}\raggedright\strut
-\strut
\end{minipage}\tabularnewline
\begin{minipage}[t]{0.17\columnwidth}\raggedright\strut
urgent\strut
\end{minipage} & \begin{minipage}[t]{0.17\columnwidth}\raggedright\strut
286 (23.9)\strut
\end{minipage} & \begin{minipage}[t]{0.17\columnwidth}\raggedright\strut
127 (27.3)\strut
\end{minipage} & \begin{minipage}[t]{0.17\columnwidth}\raggedright\strut
159 (21.8)\strut
\end{minipage} & \begin{minipage}[t]{0.17\columnwidth}\raggedright\strut
-\strut
\end{minipage}\tabularnewline
\begin{minipage}[t]{0.17\columnwidth}\raggedright\strut
emergent\strut
\end{minipage} & \begin{minipage}[t]{0.17\columnwidth}\raggedright\strut
16 (1.3)\strut
\end{minipage} & \begin{minipage}[t]{0.17\columnwidth}\raggedright\strut
10 (2.2)\strut
\end{minipage} & \begin{minipage}[t]{0.17\columnwidth}\raggedright\strut
6 (0.8)\strut
\end{minipage} & \begin{minipage}[t]{0.17\columnwidth}\raggedright\strut
-\strut
\end{minipage}\tabularnewline
\begin{minipage}[t]{0.17\columnwidth}\raggedright\strut
salvage\strut
\end{minipage} & \begin{minipage}[t]{0.17\columnwidth}\raggedright\strut
0.0 (0.0)\strut
\end{minipage} & \begin{minipage}[t]{0.17\columnwidth}\raggedright\strut
0.0 (0.0)\strut
\end{minipage} & \begin{minipage}[t]{0.17\columnwidth}\raggedright\strut
0.0 (0.0)\strut
\end{minipage} & \begin{minipage}[t]{0.17\columnwidth}\raggedright\strut
-\strut
\end{minipage}\tabularnewline
\begin{minipage}[t]{0.17\columnwidth}\raggedright\strut
CHF and NYHA class - no. (\%)\strut
\end{minipage} & \begin{minipage}[t]{0.17\columnwidth}\raggedright\strut
\strut
\end{minipage} & \begin{minipage}[t]{0.17\columnwidth}\raggedright\strut
\strut
\end{minipage} & \begin{minipage}[t]{0.17\columnwidth}\raggedright\strut
\strut
\end{minipage} & \begin{minipage}[t]{0.17\columnwidth}\raggedright\strut
0.5112\strut
\end{minipage}\tabularnewline
\begin{minipage}[t]{0.17\columnwidth}\raggedright\strut
no CHF\strut
\end{minipage} & \begin{minipage}[t]{0.17\columnwidth}\raggedright\strut
983 (82.3)\strut
\end{minipage} & \begin{minipage}[t]{0.17\columnwidth}\raggedright\strut
388 (83.4)\strut
\end{minipage} & \begin{minipage}[t]{0.17\columnwidth}\raggedright\strut
595 (81.5)\strut
\end{minipage} & \begin{minipage}[t]{0.17\columnwidth}\raggedright\strut
-\strut
\end{minipage}\tabularnewline
\begin{minipage}[t]{0.17\columnwidth}\raggedright\strut
CHF not NYHA IV\strut
\end{minipage} & \begin{minipage}[t]{0.17\columnwidth}\raggedright\strut
166 (13.9)\strut
\end{minipage} & \begin{minipage}[t]{0.17\columnwidth}\raggedright\strut
58 (12.5)\strut
\end{minipage} & \begin{minipage}[t]{0.17\columnwidth}\raggedright\strut
108 (14.8)\strut
\end{minipage} & \begin{minipage}[t]{0.17\columnwidth}\raggedright\strut
-\strut
\end{minipage}\tabularnewline
\begin{minipage}[t]{0.17\columnwidth}\raggedright\strut
CHF with NYHA IV\strut
\end{minipage} & \begin{minipage}[t]{0.17\columnwidth}\raggedright\strut
46 (3.8)\strut
\end{minipage} & \begin{minipage}[t]{0.17\columnwidth}\raggedright\strut
19 (4.1)\strut
\end{minipage} & \begin{minipage}[t]{0.17\columnwidth}\raggedright\strut
27 (3.7)\strut
\end{minipage} & \begin{minipage}[t]{0.17\columnwidth}\raggedright\strut
-\strut
\end{minipage}\tabularnewline
\begin{minipage}[t]{0.17\columnwidth}\raggedright\strut
Endocarditis - no. (\%)\strut
\end{minipage} & \begin{minipage}[t]{0.17\columnwidth}\raggedright\strut
0.0 (0.0)\strut
\end{minipage} & \begin{minipage}[t]{0.17\columnwidth}\raggedright\strut
0.0 (0.0)\strut
\end{minipage} & \begin{minipage}[t]{0.17\columnwidth}\raggedright\strut
0.0 (0.0)\strut
\end{minipage} & \begin{minipage}[t]{0.17\columnwidth}\raggedright\strut
NA\strut
\end{minipage}\tabularnewline
\begin{minipage}[t]{0.17\columnwidth}\raggedright\strut
Carotid stenosis - no. (\%)\strut
\end{minipage} & \begin{minipage}[t]{0.17\columnwidth}\raggedright\strut
103 (8.6)\strut
\end{minipage} & \begin{minipage}[t]{0.17\columnwidth}\raggedright\strut
32 (6.9)\strut
\end{minipage} & \begin{minipage}[t]{0.17\columnwidth}\raggedright\strut
71 (9.7)\strut
\end{minipage} & \begin{minipage}[t]{0.17\columnwidth}\raggedright\strut
0.0876\strut
\end{minipage}\tabularnewline
\begin{minipage}[t]{0.17\columnwidth}\raggedright\strut
Cancer within five years - no. (\%)\strut
\end{minipage} & \begin{minipage}[t]{0.17\columnwidth}\raggedright\strut
53 (4.4)\strut
\end{minipage} & \begin{minipage}[t]{0.17\columnwidth}\raggedright\strut
24 (5.2)\strut
\end{minipage} & \begin{minipage}[t]{0.17\columnwidth}\raggedright\strut
29 (4.0)\strut
\end{minipage} & \begin{minipage}[t]{0.17\columnwidth}\raggedright\strut
0.3305\strut
\end{minipage}\tabularnewline
\begin{minipage}[t]{0.17\columnwidth}\raggedright\strut
Tobacco use - no. (\%)\strut
\end{minipage} & \begin{minipage}[t]{0.17\columnwidth}\raggedright\strut
678 (56.7)\strut
\end{minipage} & \begin{minipage}[t]{0.17\columnwidth}\raggedright\strut
262 (56.3)\strut
\end{minipage} & \begin{minipage}[t]{0.17\columnwidth}\raggedright\strut
416 (57.0)\strut
\end{minipage} & \begin{minipage}[t]{0.17\columnwidth}\raggedright\strut
0.8271\strut
\end{minipage}\tabularnewline
\begin{minipage}[t]{0.17\columnwidth}\raggedright\strut
Liver disease - no. (\%)\strut
\end{minipage} & \begin{minipage}[t]{0.17\columnwidth}\raggedright\strut
30 (2.5)\strut
\end{minipage} & \begin{minipage}[t]{0.17\columnwidth}\raggedright\strut
18 (3.9)\strut
\end{minipage} & \begin{minipage}[t]{0.17\columnwidth}\raggedright\strut
12 (1.6)\strut
\end{minipage} & \begin{minipage}[t]{0.17\columnwidth}\raggedright\strut
0.0164\strut
\end{minipage}\tabularnewline
\begin{minipage}[t]{0.17\columnwidth}\raggedright\strut
PROMM - fraction\strut
\end{minipage} & \begin{minipage}[t]{0.17\columnwidth}\raggedright\strut
10.1 +/- 8.7\strut
\end{minipage} & \begin{minipage}[t]{0.17\columnwidth}\raggedright\strut
10.5 +/- 10.3\strut
\end{minipage} & \begin{minipage}[t]{0.17\columnwidth}\raggedright\strut
9.9 +/- 7.5\strut
\end{minipage} & \begin{minipage}[t]{0.17\columnwidth}\raggedright\strut
0.2208\strut
\end{minipage}\tabularnewline
\bottomrule
\end{longtable}

IABP, intra-aortic balloon pump; PCI, percutaneous coronary
intervention; PVD, peripheral vascular disease; CAD, coronary artery
disease; CVD, cerebral vascular disease; CVA, cerebrovascular accident;
MI, myocardial infarction; CHF, congestive heart failure; NYHA, New York
Heart Association; PROMM, predicted rate of major morbidity or
mortality.

Plus-minus values are means +/- standard deviation

\textbf{Table 2.}\selectlanguage{english}
\begin{longtable}[]{@{}llll@{}}
\toprule
\textbf{Characteristic} & \textbf{Group 1 ([?]10) n = 465} & \textbf{Group
2 (\textgreater{}10) n = 730} & \textbf{p-value}\tabularnewline
\midrule
\endhead
Off-pump - n (\%) & 361 (77.6) & 709 (97.1) &
\textless{}0.0001\tabularnewline
CPB time (min) - mean (SD) & 91.8 (31.6) & 84.1 (49.4) &
0.0028\tabularnewline
Total grafts - mean (SD) & 1.7 (1.2) & 1.1 (0.4) &
\textless{}0.0001\tabularnewline
CPB, cardiopulmonary bypass & CPB, cardiopulmonary bypass & CPB,
cardiopulmonary bypass & CPB, cardiopulmonary bypass\tabularnewline
\bottomrule
\end{longtable}

\textbf{Table 3.} Rate of clinical outcomes for the entire study
population and for inexperienced and experienced surgeons.\selectlanguage{english}
\begin{longtable}[]{@{}lllll@{}}
\toprule
\begin{minipage}[b]{0.19\columnwidth}\raggedright\strut
\textbf{Endpoint}\strut
\end{minipage} & \begin{minipage}[b]{0.19\columnwidth}\raggedright\strut
\textbf{All n = 1195}\strut
\end{minipage} & \begin{minipage}[b]{0.19\columnwidth}\raggedright\strut
\textbf{Group 1 ([?]10)} \textbf{n = 465}\strut
\end{minipage} & \begin{minipage}[b]{0.19\columnwidth}\raggedright\strut
\textbf{Group 2 (\textgreater{}10) n = 730}\strut
\end{minipage} & \begin{minipage}[b]{0.19\columnwidth}\raggedright\strut
\textbf{p-value}\strut
\end{minipage}\tabularnewline
\midrule
\endhead
\begin{minipage}[t]{0.17\columnwidth}\raggedright\strut
\emph{Primary}\strut
\end{minipage} & \begin{minipage}[t]{0.17\columnwidth}\raggedright\strut
\strut
\end{minipage} & \begin{minipage}[t]{0.17\columnwidth}\raggedright\strut
\strut
\end{minipage} & \begin{minipage}[t]{0.17\columnwidth}\raggedright\strut
\strut
\end{minipage} & \begin{minipage}[t]{0.17\columnwidth}\raggedright\strut
\strut
\end{minipage}\tabularnewline
\begin{minipage}[t]{0.17\columnwidth}\raggedright\strut
Approach conversion - no. (\%)\strut
\end{minipage} & \begin{minipage}[t]{0.17\columnwidth}\raggedright\strut
54 (4.5)\strut
\end{minipage} & \begin{minipage}[t]{0.17\columnwidth}\raggedright\strut
36 (7.7)\strut
\end{minipage} & \begin{minipage}[t]{0.17\columnwidth}\raggedright\strut
18 (2.5)\strut
\end{minipage} & \begin{minipage}[t]{0.17\columnwidth}\raggedright\strut
\textless{}0.0001\strut
\end{minipage}\tabularnewline
\begin{minipage}[t]{0.17\columnwidth}\raggedright\strut
Reoperation - no. (\%)\strut
\end{minipage} & \begin{minipage}[t]{0.17\columnwidth}\raggedright\strut
167 (14.0)\strut
\end{minipage} & \begin{minipage}[t]{0.17\columnwidth}\raggedright\strut
88 (18.9)\strut
\end{minipage} & \begin{minipage}[t]{0.17\columnwidth}\raggedright\strut
79 (10.8)\strut
\end{minipage} & \begin{minipage}[t]{0.17\columnwidth}\raggedright\strut
\textless{}0.0001\strut
\end{minipage}\tabularnewline
\begin{minipage}[t]{0.17\columnwidth}\raggedright\strut
Composite major morbidity or mortality - no. (\%)\strut
\end{minipage} & \begin{minipage}[t]{0.17\columnwidth}\raggedright\strut
195 (16.3)\strut
\end{minipage} & \begin{minipage}[t]{0.17\columnwidth}\raggedright\strut
101 (21.7)\strut
\end{minipage} & \begin{minipage}[t]{0.17\columnwidth}\raggedright\strut
94 (12.9)\strut
\end{minipage} & \begin{minipage}[t]{0.17\columnwidth}\raggedright\strut
\textless{}0.0001\strut
\end{minipage}\tabularnewline
\begin{minipage}[t]{0.17\columnwidth}\raggedright\strut
Procedural success - no. (\%)\strut
\end{minipage} & \begin{minipage}[t]{0.17\columnwidth}\raggedright\strut
962 (80.5)\strut
\end{minipage} & \begin{minipage}[t]{0.17\columnwidth}\raggedright\strut
339 (72.9)\strut
\end{minipage} & \begin{minipage}[t]{0.17\columnwidth}\raggedright\strut
623 (85.3)\strut
\end{minipage} & \begin{minipage}[t]{0.17\columnwidth}\raggedright\strut
\textless{}0.0001\strut
\end{minipage}\tabularnewline
\begin{minipage}[t]{0.17\columnwidth}\raggedright\strut
\emph{Secondary}\strut
\end{minipage} & \begin{minipage}[t]{0.17\columnwidth}\raggedright\strut
\strut
\end{minipage} & \begin{minipage}[t]{0.17\columnwidth}\raggedright\strut
\strut
\end{minipage} & \begin{minipage}[t]{0.17\columnwidth}\raggedright\strut
\strut
\end{minipage} & \begin{minipage}[t]{0.17\columnwidth}\raggedright\strut
\strut
\end{minipage}\tabularnewline
\begin{minipage}[t]{0.17\columnwidth}\raggedright\strut
Operative mortality - no. (\%)\strut
\end{minipage} & \begin{minipage}[t]{0.17\columnwidth}\raggedright\strut
10 (0.8)\strut
\end{minipage} & \begin{minipage}[t]{0.17\columnwidth}\raggedright\strut
5 (1.1)\strut
\end{minipage} & \begin{minipage}[t]{0.17\columnwidth}\raggedright\strut
5 (0.7)\strut
\end{minipage} & \begin{minipage}[t]{0.17\columnwidth}\raggedright\strut
0.4702\strut
\end{minipage}\tabularnewline
\begin{minipage}[t]{0.17\columnwidth}\raggedright\strut
Prolonged length of hospitalization - no. (\%)\strut
\end{minipage} & \begin{minipage}[t]{0.17\columnwidth}\raggedright\strut
2 (0.2)\strut
\end{minipage} & \begin{minipage}[t]{0.17\columnwidth}\raggedright\strut
1 (0.2)\strut
\end{minipage} & \begin{minipage}[t]{0.17\columnwidth}\raggedright\strut
1 (0.1)\strut
\end{minipage} & \begin{minipage}[t]{0.17\columnwidth}\raggedright\strut
0.7475\strut
\end{minipage}\tabularnewline
\bottomrule
\end{longtable}

\textbf{Table 4.} Results of multivariable regression analysis
demonstrating adjusted associations between predictors and primary
clinical outcomes.\selectlanguage{english}
\begin{longtable}[]{@{}llll@{}}
\toprule
\textbf{Endpoint} & \textbf{Predictor} & \textbf{OR (95\% CI)} &
\textbf{p-values}\tabularnewline
\midrule
\endhead
Approach conversion & \textbf{Experience group 2 (\textgreater{}10
cases)} & \textbf{0.27 (0.09 - 0.84)} & \textbf{0.0233}\tabularnewline
& Insulin-dependent diabetes & 0.24 (0.06 - 0.90) &
0.0341\tabularnewline
& Female gender & 5.61 (1.83 - 17.2) & 0.0026\tabularnewline
Procedural success & \textbf{Experience group 2 (\textgreater{}10
cases)} & \textbf{1.96 (1.00 - 3.84)} & \textbf{0.0499}\tabularnewline
& Myocardial infarction between 1 to 21 days & 0.43 (0.19 - 0.95) &
0.0358\tabularnewline
Composite major morbidity or mortality & Age & 1.06 (1.02 - 1.10) &
0.0029\tabularnewline
& Myocardial infarction between 1 to 21 days & 4.80 (1.88 - 12.2) &
0.001\tabularnewline
& Aortic insufficiency & 3.15 (1.03 - 9.62) & 0.0443\tabularnewline
& Hispanic race & 3.99 (1.27 - 12.5) & 0.0181\tabularnewline
Reoperation & Mitral valve insufficiency & 3.92 (1.38 - 11.1) &
0.0104\tabularnewline
OR, odds ratio; CI, confidence interval & & &\tabularnewline
\bottomrule
\end{longtable}\selectlanguage{english}
\begin{figure}[H]
\begin{center}
\includegraphics[width=0.70\columnwidth]{figures/Figure-1/Figure-1}

\end{center}
\end{figure}\selectlanguage{english}
\begin{figure}[H]
\begin{center}
\includegraphics[width=0.70\columnwidth]{figures/Figure-2/Figure-2}

\end{center}
\end{figure}\selectlanguage{english}
\begin{figure}[H]
\begin{center}
\includegraphics[width=0.70\columnwidth]{figures/Figure-3/Figure-3}

\end{center}
\end{figure}\selectlanguage{english}
\begin{figure}[H]
\begin{center}
\includegraphics[width=0.70\columnwidth]{figures/Figure-4/Figure-4}

\end{center}
\end{figure}

\selectlanguage{english}
\FloatBarrier
\end{document}

