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\begin{document}

\title{Normal range of intraoperative three-dimensional derived right
ventricular strain in coronary artery bypass surgery patients}



\author[1]{Jens Fassl}%
\author[1]{Jakob Labus}%
\author[1]{Johan Winata}%
\author[1]{Torsten Schmidt}%
\author[1]{Joachim Nicolai}%
\author[1]{Stanislaw Vander Zwaag}%
\author[1]{Kunislav Sveric}%
\author[1]{Manuel Wilbring}%
\author[2]{Markus Scholz}%
\affil[1]{Herzzentrum Dresden GmbH Universitatsklinik an der Technischen Universitat Dresden}%
\affil[2]{Universitat Leipzig Medizinische Fakultat}%


\vspace{-1em}



  
  \date{June 07, 2024}


\begingroup
\let\center\flushleft
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\endgroup





\selectlanguage{english}
\begin{abstract}
\emph{Objectives:} Data on intraoperative three-dimensional derived
right ventricular free-wall strain (3D-RV FWS) is sparse. We sought to
evaluate the normal range of intraoperative 3D-RV FWS in patients
scheduled for coronary artery bypass graft (CABG) surgery and compare to
conventional echocardiographic parameters. \emph{Design:} Prospective
observational study. \emph{Setting:} Single university hospital.
\emph{Participants:} 150 patients with preserved left and right
ventricular function and sinus rhythm, without significant heart valve
disease or pulmonary hypertension undergoing isolated onpump CABG
surgery, with an uneventful, complication-free intraoperative course.
\emph{Interventions:} 3D-RV FWS analysis and conventional
echocardiographic assessment of right ventricular function were
performed intraoperatively in anesthetized and ventilated patients using
transesophageal echocardiography (TEE). All echocardiographic
measurements were performed under stable hemodynamic conditions and
predefined fluid management without any vasoactive support or pacing.
\emph{Measurements and Main Results:} We used TomTec 4D RV-Function 2.0
software for assessment of 3D-RV FWS and three-dimensional right
ventricular ejection fraction (3D-RV EF). Philips QLAB 10.8 was used to
evaluate tissue velocity of the tricuspid annulus (RV S\selectlanguage{ngerman}´), tricuspid
annular systolic excursion (TAPSE), and RV fractional area change (FAC).
Assessment of 3D-RV FWS was feasible in 95\% of patients. No included
patient experienced a serious perioperative complication. In our group
of patients, median values with interquartile range (IQR) for 3D-RV FWS
and 3D-RV EF were - 25.2 (IQR -29.9 - -21.8) and 46.3\% (IQR 41.0 -
50.1\%), respectively. RV FAC, RV S´ and TAPSE accounted for 39.7\% (IQR
34.5 - 44.4\%), 14.8cm/s (IQR 11.8 - 19.0cm/s) and 22 mm (IQR 20-25mm).
Normal range (2.5\% to 97.5\% percentile) for 3D-RV FWS was -37.1 to
-12.8. There was no relevant correlation of 3D-RV FWS to postoperative
outcome in this group of CABG patients. \emph{Conclusion:} We present
distribution values for intraoperative 3D-RV FWS and conventional
parameters of RV function assessment in a healthy on-pump CABG patient
population without serious perioperative complications. We observed no
correlations of these parameters with any of the outcome parameters
considered. Therefore, we consider these values to be intraoperative
TEE-assessed \emph{normal} values that can be expected in onpump CABG
patients.%
\end{abstract}\selectlanguage{ngerman}%



\sloppy


\textbf{Normal range of intraoperative three-dimensional derived right
ventricular strain in coronary artery bypass surgery patients}

Jakob Labus, MD\textsuperscript{*\#}, Johan Winata,
MD\textsuperscript{*}, Torsten Schmidt, MD\textsuperscript{*}, Joachim
Nicolai, MD\textsuperscript{*}, Stanislaw Vander Zwaag,
MD\textsuperscript{*}, Kunislav Sveric, MD\textsuperscript{+}, Manuel
Wilbring, MD, PhD\textsuperscript{++}, Markus Scholz, PhD', Jens Fassl,
MD, PhD, FASE\textsuperscript{*}

* Department of Cardiac Anesthesiology, Heart Center Dresden, University
Hospital, Fetscherstra\selectlanguage{ngerman}ße 76, 01307 Dresden, Germany

\selectlanguage{english}\textsuperscript{+} Department of Cardiology and Internal Medicine,
Heart Center Dresden, University Hospital, Fetscherstrasse 76, 01307
Dresden, Germany

\selectlanguage{english}\textsuperscript{++} Department of Heart Surgery, Heart Center Dresden,
University Hospital, Fetscherstrasse 76, 01307 Dresden, Germany

' Institute for Medical Informatics, Statistics and Epidemiology,
Medical Faculty, Leipzig University,

Haertelstrasse 16-18, 04107 Leipzig, Germany

\textsuperscript{\#} Department of Anesthesiology and Intensive Care
Medicine, University Hospital of Cologne, and Faculty of Medicine,
University of Cologne, Cologne, Germany

\textbf{Corresponding Author}Jens Fassl, MD, PhD, FASE Department of
Cardiac Anesthesiology, Heart Center Dresden, University Hospital

Fetscherstrasse 76, 01307 Dresden, Germany

Email: jens.fassl@herzzentrum-dresden.com

Phone: +493514501603

\textbf{Conflict of Interest}

The authors declare there are no conflicts of interest.

\textbf{Statement of Funding}

This research did not receive any specific grant from funding agencies
in the public, commercial, or not-for- profit sector.

\textbf{Ethics Approval Statement}

The institutional review board of the medical faculty of the Technical
University of Dresden, Germany, approved this prospective observational
study.

\textbf{Patient Consensus Statement}

All patients were enrolled between January 2019 and April 2020 after
written informed consent.

\emph{Objectives:} Data on intraoperative three-dimensional derived
right ventricular free-wall strain (3D-RV FWS) is sparse. We sought to
evaluate the normal range of intraoperative 3D-RV FWS in patients
scheduled for coronary artery bypass graft (CABG) surgery and compare to
conventional echocardiographic parameters.

\emph{Design:} Prospective observational study.

\emph{Setting:} Single university hospital.

\emph{Participants:} 150 patients with preserved left and right
ventricular function and sinus rhythm, without significant heart valve
disease or pulmonary hypertension undergoing isolated onpump CABG
surgery, with an uneventful, complication-free intraoperative course.

\emph{Interventions:} 3D-RV FWS analysis and conventional
echocardiographic assessment of right ventricular function were
performed intraoperatively in anesthetized and ventilated patients using
transesophageal echocardiography (TEE). All echocardiographic
measurements were performed under stable hemodynamic conditions and
predefined fluid management without any vasoactive support or pacing.

\emph{Measurements and Main Results:} We used TomTec 4D RV-Function 2.0
software for assessment of 3D-RV FWS and three-dimensional right
ventricular ejection fraction (3D-RV EF). Philips QLAB 10.8 was used to
evaluate tissue velocity of the tricuspid annulus (RV S'), tricuspid
annular systolic excursion (TAPSE), and RV fractional area change (FAC).
Assessment of 3D-RV FWS was feasible in 95\% of patients. No included
patient experienced a serious perioperative complication.

In our group of patients, median values with interquartile range (IQR)
for 3D-RV FWS and 3D-RV EF were - 25.2 (IQR -29.9 - -21.8) and 46.3\%
(IQR 41.0 - 50.1\%), respectively. RV FAC, RV S' and TAPSE accounted for
39.7\% (IQR 34.5 - 44.4\%), 14.8cm/s (IQR 11.8 - 19.0cm/s) and 22 mm
(IQR 20-25mm). Normal range (2.5\% to 97.5\% percentile) for 3D-RV FWS
was -37.1 to -12.8.

There was no relevant correlation of 3D-RV FWS to postoperative outcome
in this group of CABG patients.

\emph{Conclusion:} We present distribution values for intraoperative
3D-RV FWS and conventional parameters of RV function assessment in a
healthy on-pump CABG patient population without serious perioperative
complications. We observed no correlations of these parameters with any
of the outcome parameters considered. Therefore, we consider these
values to be intraoperative TEE-assessed \emph{normal} values that can
be expected in onpump CABG patients.

\emph{Key Words:} three-dimensional echocardiography; strain analysis;
right ventricle; free wall strain; cardiac surgery; reference values

\textbf{Introduction}

Right ventricular (RV) function strongly predicts outcome after cardiac
surgery.\textsuperscript{1, 2} Echocardiography remains a cornerstone in
detecting perioperative RV dysfunction, but the complex geometry of the
right ventricle makes echocardiographic assessment still
challenging.\textsuperscript{3, 4} Conventional echocardiographic
parameters for RV function assessment have numerous limitations
including incomplete imaging of the complex crescent-shaped right
ventricle and angle dependency of Doppler and M-mode
technique.\textsuperscript{5} Strain analysis with speckle-tracking
echocardiography (STE) becomes an advancing technique to measure
myocardial function. Myocardial strain analysis is less dependent on
loading conditions, does not rely on geometric assumptions, has a
smaller interobserver variability, is largely angle-independent and is
an independent predictor of RV function.\textsuperscript{6-8} Therefore,
strain analysis seems particularly suitable for the perioperative
assessment of the right ventricle. Most data on RV strain analysis,
however, comes from the evaluation of awake spontaneously breathing
patients using transthoracic echocardiography (TTE).\textsuperscript{5,
9} Intraoperative evaluation of RV strain in anesthetized and ventilated
patients using transesophageal echocardiography (TEE) is feasible and
supports perioperative decision making, but there is only limited
data.\textsuperscript{7, 10} In particular, this is true for
three-dimensional derived right ventricular strain
analysis.\textsuperscript{11, 12} Regardless of the possible benefit of
three-dimensional derived RV strain, this technique is quite novel and
is not well described in the intraoperative period. Evaluation is
challenging by the fact that there are no established normal or
reference values for the intraoperative setting. Therefore, by the
present study we aim to close this gap by providing intraoperative
values for three-dimensional derived right ventricular free-wall strain
(3D-RV FWS) that can be expected in onpump coronary artery bypass
grafting (CABG) patients with a complication-free, unremarkable
intraoperative course.

\textbf{Methods}

\textbf{Study Population}

The institutional review board of the medical faculty of the Technical
University of Dresden, Germany, approved this prospective observational
study. 150 adult patients were enrolled between January 2019 and April
2020 after written informed consent. All patients had preoperative sinus
rhythm and preserved LV and RV function. We excluded patients with
contraindications to TEE, redo cardiac surgery, more than mild valvular
heart disease, pulmonary hypertension (mean pulmonary artery pressure
\textgreater{}25 mmHg), or insufficient quality of echocardiographic
assessment preventing the analysis of three-dimensional data sets.

\textbf{Anesthesia Management}

Following our institutional protocol, anesthesia was induced with
fentanyl, propofol, and rocuronium and was maintained with sevoflurane
and fentanyl. Lungs were ventilated mechanically with a tidal volume of
6 to 8 mL/kg with a positive end-expiratory pressure of \selectlanguage{english}[?] 5 mbar,
maintaining normoxia and normocapnia. Patients were restricted to a
maximum of 500 mL of balanced crystalloid infusion till intraoperative
echocardiography. All echocardiographic measurements were performed
without any influence of inotropic or vasopressor support and pacing.
All echocardiographic studies were performed under stable hemodynamics
and in sinus rhythm. Following the standards of our institutional
hemodynamics protocol mean arterial blood pressure (MAP) and central
venous pressure (CVP) were maintained establishing stable hemodynamics
(MAP 60-80 mmHg, CVP 4-12 mmHg).

\textbf{Surgical Management}

Onpump CABG surgery was performed under normothermic conditions via
median sternotomy. Full myocardial revascularization was achieved using
single internal thoracic artery grafting and/or aortocoronary vein
grafts, according to the clinical demands. After aortic cross-clamping
cardiac arrest was achieved by blood cardioplegia. In all patients the
pericardium was closed at the end of surgery.

\textbf{Echocardiographic Assessment}

We performed TEE after induction of anesthesia before sternotomy and any
canulation of the patient. All measurements were done with Philips Epic
7 echocardiography machines and X8-2T-TEE probes. Examinations were
performed by a board certified echocardiographer according to recent
recommendations for TEE examination.\textsuperscript{13, 14}

Real-time three-dimensional full-volume datasets, including the entire
RV, were acquired from a mid-esophageal RV-focused four-chamber-view.
Four-beat acquisition during apnea was performed. The settings of the
ultrasound machine were adapted to a high temporal resolution. TomTec
4D-RV-Function-2.0 (TomTec Imaging Systems GmbH, Unterschleissheim,
Germany) was used for estimation of three-dimensional derived
RV-free-wall strain (3D-RV FWS) and RV ejection fraction (3D-RV EF).
This software is based on speckle-tracking technology and provides a
semi-automated quantification of RV size and
function.\textsuperscript{15, 16} Therefore, RV borders needs mandatory
adjustment by the operator after automatic extraction and tracking of
the right ventricle out of the full-volume data
set.\textsuperscript{16}Figure 1 shows the assessment of 3D-RV EF and
3D-RV FWS by TEE.

For the evaluation of tissue velocity of the tricuspid annulus (RV S'),
tricuspid annular systolic excursion (TAPSE), and RV fraction area
change (RV FAC) we used Philips QLAB 10.8 software. TAPSE was assessed
in the midesophageal RV-focused four-chamber-view by measuring the
displacement of the tricuspid annulus in anatomic M-mode. Anatomic
M-mode is an angle independent M-mode that allows the operator to
position the cursor freely on the two-dimensional image. Therefore, the
cursor was directed towards the RV apex. RV FAC was evaluated from
midesophageal RV-focused four-chamber view. The change of RV area in
relation to diastolic RV area was calculated and is shown in percent. RV
S' was assessed from the midesophageal RV-focused four-chamber view
measuring the peak positive tissue velocity using pulsed wave
tissue-Doppler imaging during ejection period in an angle-independent
manner. Therefore, the cursor of the Doppler was directed towards the RV
apex, which is available on all our Philips Epic 7 echocardiography
machines. Settings of the ultrasound machine were adapted to high
temporal resolution with a frame rate \textgreater{}100 frames/s. The
sample volume of the pulsed-wave Doppler was set to 5-7 mm following
recent suggestions of the European Association of Cardiovascular Imaging
(EACVI).\textsuperscript{17}

\textbf{Outcome measures}

We assessed the postoperative outcome measures of MACE (Major Adverse
Cardiac Events as composite of stroke, cardiovascular death, instable
angina pectoris, heart failure), stroke, transitory ischemic attack,
shock, pneumonia, atrial fibrillation, renal replacement therapy,
postoperative mechanical circulatory support, Redo CABG surgery or
percutaneous revascularization. Moreover, we evaluated the duration of
mechanical ventilation, duration of intensive care therapy, hospital
stay and in-hospital death.

\textbf{Statistical Methods}

Statistical analyses of data were performed using MS Excel (Microsoft,
Redmond, Washington), XLSTAT (Addinsoft, New York, New York) and the
statistical software package R. Data was checked for normal distribution
by visual assessment of histograms, Q-Q plots and additionally
Shapiro-Wilk-test. Normally distributed data is presented as mean +-
standard deviation, not normally distributed data as median with
interquartile range (IQR). Percentiles were estimated using the
function\emph{quantile} of the statistical software package R with
standard settings. Associations between 3D-RV FWS and patient outcomes
was evaluated by linear (for continuous outcomes) or logistic (for
binary outcomes) regression analysis. We adjusted for age and sex.

\textbf{Results}

3D-RV FWS analysis was feasible in 142 (95\%) patients. All patients had
a complete myocardial revascularization at the end of surgery and
pericardial closure. None of the patients was pacemaker dependent or on
inotropic or vasopressor support during echocardiographic evaluation.
Baseline characteristics are presented in Table 1. Essential
perioperative data are presented in Table 2.

No patient required intraoperatively inotropic or mechanical circulatory
support after bypass, experienced shock or had a second run on CPB after
termination of extracorporal circulation.

There were no postoperative complications in this patient population
such as MACE, stroke, transitory ischemic attack, shock, pneumonia, or
in-hospital death. No patient needed postoperatively renal replacement
therapy, mechanical circulatory support, or redo CABG or percutaneous
revascularization. Two patients (1.4\%) had a ventilation time of more
than 24 hours (34 and 39 hours, respectively) and ten patients (7.0\%)
developed atrial fibrillation postoperatively.

In our group of patients, median values with interquartile range (IQR)
for 3D-RV FWS and 3D-RV EF were - 25.2 (IQR -29.9 - -21.8) and 46.3\%
(IQR 41.0 - 50.1\%), respectively. RV FAC, RV S' and TAPSE accounted for
39.7\% (IQR 34.5 - 44.4\%), 14.8cm/s (IQR 11.8 - 19.0cm/s) and 22 mm
(IQR 20-25mm). There was no correlation of 3D-RV FWS and patient
outcome, beside a small and clinically irrelevant correlation to
prolonged in-hospital duration (r\textsuperscript{2}=0.03, p=0.02), in
our group of patients. Normal values (2.5\% to 97.5\% percentile) for
3D-RV FWS and 3D-RV EF were -37.1 to -12.8 and for 34.9\% to 58.2\%,
respectively, and amounted 24.6\% to 52.1\% for RV FAC, 5.7cm/s to
34.3cm/s for RV S` and 15.6mm to 31.5mm for TAPSE.

In 22 patients (15\%) 3D-RV FWS was more impaired than -20, as suggested
cut-off value for two-dimensional-derived (2D) RV FWS by recent
guidelines on chamber quantification\textsuperscript{5}. Considering
only patients with 3D-RV EF \selectlanguage{english}[?]45\%, regarded as \emph{normal} for
TTE-assessed 3D-RV EF by same guidelines\emph{,\textsuperscript{5}} we
observed median values for 3D-RV FWS of -27.7 (IQR -31.5; -24.5) and a
2.5\% to 97.5\% - percentile of -38.5 to -17.1 in this subgroup of 86
patients.

Intraoperative values of 3D-RV FWS and the conventional
echocardiographic parameters of RV function are presented in Table 3 and
Figure 2 and 3.

\textbf{Discussion}

3D-RV FWS analysis is an innovative instrument for assessment of
longitudinal RV function. In the present study we described
intraoperativ \emph{normal} values for 3D-RV FWS that can be expected in
onpump CABG patient with preoperative preserved LV and RV function and
an uneventful perioperative course, and compared them to conventional
parameters of RV function assessment. Although, 3D-RV FWS assessment was
already described as feasible, intraoperativ data are
sparse.\textsuperscript{11, 12, 18} Intraoperative evaluation RV strain
and decision making is ambitious since there are no established
reference values for anesthetized and ventilated cardiac surgery
patients as there are for awake, spontaneously breathing patients in the
non-operative setting.\textsuperscript{5, 9} Therefore, our study has
important findings.

In our group of CABG patients, with preserves LV and RV function and an
uneventful intraoperative course we were able to measure 3D-RV FWS after
induction of anesthesia, under stable hemodynamics, a predefined fluid
management and without the influence of vasoactive support or pacing, in
about 95\% of our patients. These measured values for RV FWS are
not\emph{normal values} as it would be expected for healthy volunteers
without cardiac disease, but \emph{normal values} that can be expected
in CABG patients with preserved LV and RV function, and a
complication-free intraoperative course. In our opinion \emph{normal
values} from individuals without cardiac disease are not helpful in
intraoperative decision making in cardiac surgery patients with
different cardiac states (e.g., ischemia or subclinical myocardial
dysfunction beside normal conventional parameters). Regarding existing
literature, we are unaware of published reports on 3D-RV FWS in onpump
CABG patients, beside our own pilot study.\textsuperscript{12} Other
authors report about 3D-RV FWS in different patient populations and
clinical scenarios. Keller et al.\textsuperscript{18} reported in a
retrospective chart review about left-sided cardiac valve surgery
patients with different grades of LV and RV function and different
pulmonary pressure profiles. They described prebypass values of 3D-RV
FWS of -19.4 +- 6 (95\%-CI -20.9; -17.9) in 59 patients with normal
pulmonary artery pressure profiles, but heterogenous LV function, and of
-20.5 +- 7.3 (95\%-CI -22.4; -18.6) in 60 patients with normal LV
function, but different pulmonary pressure profiles. Patients in this
group were treated with norepinephrine as clinical necessary. In another
retrospective study Keller and colleagues\textsuperscript{11} observed
presternotomy TEE-assessed 3D-RV FWS values of -19.6 +- 6.9 in
twenty-three off-pump CABG patients and -20.1 +- 7.1 in twenty mitral
valve surgery patients, both groups again treated with vasoactive
therapy as clinical necessary. In a huge retrospective study including
496 patients, Keller et al.\textsuperscript{19} report about a
heterogenous cardiac surgery patient population with different LV and RV
function constellations including CABG and/or valve surgery procedure
and even left ventricular assist device (LVAD) implantations in elective
and urgent scenarios. Using a custom-made 3D mesh-derived software they
were able to measure three-dimensional RV FWS. In their report they
present values of this 3D mesh-derived RV FWS of -17.7 +- 6.9, assessed
after induction of anesthesia and before sternotomy by TEE. Their
patient population was supported by vasopressors and/or inotropes as
clinically necessary. The presented data for 3D-RV FWS of our study
patients could be considered as \emph{normal} because our patient
collection was less heterogeneous than the above-mentioned studies, not
supported by vasopressor and/or inotropes and had no serious
perioperative complications. However, 3D-RV FWS in our study was more
declined than the \emph{normal} values of TTE-assessed 2D-RV FWS
reported by ASE / EACVI guidelines on chamber
quantification\textsuperscript{5} of -29+-4.5, or normal values of 2D-RV
FWS from World Alliance of Societies of Echocardiography
Study\textsuperscript{20} of -28.3+-4.3, or from a metanalysis from Fine
et al.\textsuperscript{9} of -27+-2, described for all ages and genders
in healthy individuals. Although all of our patients were preoperatively
evaluated having preserved RV function by conventional parameters, 3D-RV
EF was reduced (\textless{}45\%) in 56 patients. Therefore, we evaluated
3D-RV-FWS also in a subgroup of our patients with 3D-RV EF \selectlanguage{english}[?]45\%.

Differences in the altered described \emph{normal} values might be
explained by the more declined RV function in heart valve surgery and
mixed populations of the retrospective studies from Keller and
colleagues compared to our relatively healthy CABG population with
preserved LV and RV function and without more than mild heart valve
disease and without elevated pulmonary pressure. Our data are comparable
to observed values for 2D-RV FWS measured by TTE after induction of
anesthesia in non-cardiac surgery patients without myocardial disease
reported by Dalla\textsuperscript{21} et al. (-26.5+-3.9). Prospective
observations of 2D-RV FWS by Donauer et al.\textsuperscript{22} and
Gronlykke et al.,\textsuperscript{23} each with 30 CABG patients
included, revealed higher mean values, which means a more declined RV
function, in their patient populations of -22+-4 and -19.9+-7.2,
respectively. This may be explained by differences in used assessment
technique, different vendors of echo machines and probes, or by
initially more declined RV function beside stated normal or preserved RV
function, as evaluated preoperatively by conventional echocardiographic
parameters. Our own pilot trial\textsuperscript{12} showed a median
3D-RV FWS of -24.35 with an interquartile range (IQR) of -29.8 to -20.6.
The fact that we measured RV function under stable hemodynamic
conditions after induction of anesthesia, without influence of
vasopressors or any other intravenous vasoactive therapy and in the
absence of rhythm disorder may help to explain our data.

We have strengthened our trial in choosing a homogenous group of
patients with preserved LV and RV function, homogenous procedures
without influence of vasoactive support on echocardiographic evaluation,
a predefined infusion regime and sinus rhythm, used only one vendor and
type of echo machine and probes and used three-dimensional full-volume
multi-beat acquisition that captures all essential structures through
the entire cardiac cycle.

Our study has limitations. It is a single-center observational study
including 150 patients. Evaluation of 3D-RV FWS is an ``offline''
analysis and mostly not incorporated in the echo machines at the moment.
However, we suppose that this novel parameter will be included on the
echo machines in the near future and become available for intraoperative
``online'' evaluation. We did not analyze regional differences of 3D-RV
FWS and did not evaluate for a correlation with localization of coronary
heart disease. But most of our patients had triple vessel disease. Most
of our patients were men older than 60 years, which might influence
generalization of the results. Finally, we did not evaluate intra- or
interobserver variability. Since our trial is a prospective single
center observational study, the results need to be confirmed in further
well-designed multicenter trials. Our data might help in to find
reference values for intraoperative decision making in on-pump CABG
surgery patients and could serve as a basis for further research.

\textbf{Conclusion}

We report \emph{normal} values for intraoperative 3D-RV FWS considering
a relatively healthy group of onpump CABG patients with an uneventful
perioperative course, without the influence of vasoactive therapy or
pacing, and without serious complications. Our data demonstrate that
TEE-assessed values in anesthetized, and ventilated CABG surgery
patients differ compared to reported TTE-assessed values in healthy,
awake and spontaneously breathing patients without cardiac disease, but
not the large extent as suspected in view of the mixture of procedures
and heterogeneity of patient populations considered in other
perioperative trials.



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