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\begin{document}

\title{Evaluation of right ventricular diastolic dysfunction after Coronary
Artery Bypass Grafting (CABG) surgery}



\author[1]{Maryam Faghani}%
\author[1]{Nakisa Khansari}%
\author[1]{Ali Fathi Jouzdani}%
\author[1]{Shahram Homayounfar}%
\author[1]{BABAK  manafi}%
\author[1]{Seyed Kianoosh Hosseini}%
\author[1]{Mohammad Ali Seif Rabiee}%
\author[1]{Fahimeh Ghasemi}%
\affil[1]{Hamadan University of Medical Sciences Medical School}%


\vspace{-1em}



  
  \date{May 22, 2024}


\begingroup
\let\center\flushleft
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\selectlanguage{english}
\begin{abstract}
\textbf{Background}: Coronary artery bypass grafting (CABG) is a
surgical procedure used in the treatment of coronary artery disease and
to improve heart function. Right ventricular (RV) function is unclear
based on myocardial velocities before and after coronary artery bypass
graft surgery. RV dysfunction is a known cause of hypotension in early
CABG surgery. The diastolic function has been shown to be a significant
contributor to mortality and cardiac morbidity in recent years. Our
study aimed to assess RV diastolic dysfunction after CABG surgery.
\textbf{Methods:} Forty-four patients with the two-vessel disease (2
VD), small vessel disease (SVD) and three-vessel disease (3 VD) facial
ischemia candidates for CABG surgery were studied. All patients
underwent colour Doppler and RV strain echocardiography before and one
month after CABG surgery, and patients' RV function indices were
calculated. Data analysis was performed using SPSS 21 software and a
value of P\textless{}0.05 was considered statistically significant.
\textbf{Results:} Out of forty patients, the male to female ratio was
32:8 and their mean age was 65.17 \selectlanguage{ngerman}± 7.87 years and their mean body mass
index was 25.59± 3.20. Four patients were operated on without pumps. One
month after CABG, systolic pulmonary artery pressure (SPAP), left
ventricular ejection fraction (LVEF) and RV Diameter indexes increased
significantly. Fractional area change (FAC), RV global longitudinal
strain (GLS), Tissue Doppler imaging systolic wave (SM), RV myocardial
perfusion imaging (MPI) and Tricuspid annular plane systolic excursion
(TAPSE) decreased, which was less in the 3VD group than in the 1VD/2VD
group (P \textless{}0.001). There was no significant difference between
RV diastolic diameter (RVDD) and left ventricular diastolic diameter
(LVDD) before and one month after CABG (P \textless{}0.05).
Additionally, no significant correlation was detected between changes in
RV strain and pump connection time. \textbf{Conclusion:} RV diastolic
function is significantly reduced after CABG surgery. Surgery without
the pump can certainly not eliminate this dysfunction and be effective
in reducing its severity.%
\end{abstract}\selectlanguage{ngerman}%



\sloppy


\textbf{Introduction}

The incidence of coronary heart disease has increased in developing
countries. Genetics, lifestyle, and diet play an essential role in
developing diseases, especially cardiovascular diseases (1). These
diseases are still the leading cause of death from cardiovascular
disease; despite significant advances in reducing mortality, they are
the leading cause of death in many countries (2). Studies from developed
countries show that about 1-2 of every five deaths in these countries
result from coronary artery disease (3, 4). The incidence of
cardiovascular disease is on the rise in the Eastern Mediterranean and
the Middle East, including Iran. Based on sporadic studies, Iran has a
mortality rate from cardiovascular disease ranging from 25 to 45\% (5).
Coronary artery bypass graft (CABG) surgery is the low blood pressure is
a typical result of RV dysfunction early after CABG surgery. RV
dysfunction may develop during surgery and be stable in the early
postoperative phase. The most common open-heart procedure is to treat
advanced coronary artery disease patients. CABG is performed when at
least 54\% of the lumen of one or more coronary arteries is narrowed by
stenosis, and also the angiographic image shows an artery. The number of
CABGs performed to treat coronary artery disease has increased more than
fivefold since 1980 (6, 7). In patients with chronic heart failure, the
right ventricular (RV) function is a significant indicator of symptoms
and activity capacity and one of the most significant predictors of
morbidity and mortality (8). The RV dysfunction is a known cause of low
blood pressure after CABG surgery. RV dysfunction may develop during
surgery and be stable in the early postoperative stages (9). To preserve
hemodynamic stability and cardiac function in the early postoperative
stage and determine the prognosis of the next stage, it is essential to
properly diagnose and manage RV dysfunction after CABG (10). RVs have
complicated structural and physiological characteristics due to their
unfavourable position in the thoracic cavity, making them difficult to
evaluate (11). Tissue Doppler Imaging is a new method of
echocardiography to assess ventricular functions (12). Several factors
can cause ventricular diastolic dysfunction, including hypertension,
which triggers systolic and diastolic ventricular dysfunction, resulting
from increased afterload (13). In this study, we evaluate RV diastolic
disorders following CABG surgery.

\textbf{Methods}

This cross-sectional study was performed from 2018 to 2019 on forty
patients (32 males and 8 females) with small vessel disease (SVD),
two-vessel disease (2VD) and three-vessel disease (3VD) that were
referred to the cardiac surgery ward of Farshchian Hospital in Hamadan,
Iran as CABG candidates. The protocol of the present study was evaluated
and approved by the Ethics Committee of Hamadan University of Medical
Sciences (IR.UMSHA.REC.1399.293). All participants provided their
informed consent.

Color Doppler Echocardiography and RV Strain examinations were performed
on all patients before and one month after surgery. Also, LVDD, RVDD, RV
Diameter, TAPSE, FAC, PAP, LVEF, MPI, TDI indices were measured for all
patients. A checklist was used to gather demographic data regarding the
patients, including age, gender, diabetes history, blood pressure,
smoking history, Vascular Grafts, and Pump Time.

Thirty-six patients underwent CABG using the cardiopulmonary pump
(on-pump) and four patients did not use the pump (off-pump). Among 40
patients, 20 SVD and 2VD patients without severe stenosis in the right
coronary artery (RCA) territory and 20 3VD patients with severe stenosis
in the RCA territory were examined. Figure 1 shows the frequency
distribution of graft types used in RCA territory. Paired t-test and
Friedman test were used in data analysis. SPSS software version 21 was
used for all statistical analyses and P\textless{}0.05 was considered
statistically significant.

\textbf{Results}

In accordance with Table 1, the mean age of patients was 67.15\selectlanguage{ngerman}±7.87
years, and the mean body mass index was 25.59±3.20. Twenty-eight (70\%)
patients had a history of hypertension and twenty-six (65\%) had a
history of diabetes and twenty-eight (70\%) had a history of smoking.
The distribution of graft types performed in RCA patients can be seen in
Figure 1.

\textbf{Table 1. Basic characteristics of patients.}\selectlanguage{english}
\begin{longtable}[]{@{}ll@{}}
\toprule
Age & 67.15\selectlanguage{ngerman}±7.87\tabularnewline
\midrule
\endhead
Average body mass index (BMI) & 25.59\selectlanguage{ngerman}±3.20\tabularnewline
Sex (Male: Female) & 32:8\tabularnewline
Hypertension & 28 (70\%)\tabularnewline
Diabetes & 26 (65\%)\tabularnewline
Smoking & 28 (70\%)\tabularnewline
Hyperlipidemia & 18 (45\%)\tabularnewline
\bottomrule
\end{longtable}

The mean connection time to the pump during surgery was totally
49.87\selectlanguage{ngerman}±5.2 in the SVD group and 49.00±4.47 minutes in the 2VD group and
50.75±5.64 minutes in the 3VD group (P =0.296). (Figure 1)\selectlanguage{english}
\begin{figure}[H]
\begin{center}
\includegraphics[width=0.70\columnwidth]{figures/image1/image1}

\end{center}
\end{figure}

\textbf{Figure 1: Graft types in patients in the 3VD group}\selectlanguage{english}
\begin{figure}[H]
\begin{center}
\includegraphics[width=0.70\columnwidth]{figures/image2/image2}

\end{center}
\end{figure}

\textbf{Figure 2: Connection times of pumps vary with the number of
vessels in patients during coronary artery surgery}

As shown in Table 2, A significant difference can be seen between the
first and second groups in terms of the number of RV strain changes (P
\textless{}0.001) and RV function in the second group (3 VD) decreased
than the first group.

\textbf{Table 2:} \textbf{The rate of RV Strain change in patients
undergoing coronary artery surgery based on the number of vessels
involved.}\selectlanguage{english}
\begin{longtable}[]{@{}llll@{}}
\toprule
Number of vessels involved & Mean & Standard deviation &
P-value\tabularnewline
\midrule
\endhead
SVD, 2 VD & -7.62 & 0.93 & P\textless{}0.0001\tabularnewline
3 VD & -6.33 & 0.76 & P\textless{}0.0001\tabularnewline
\bottomrule
\end{longtable}

2 VD: Two-vessel disease, SVD: small vessel disease, 3 VD: Three-vessel
disease. Paired t-test was used for comparison between groups.

As shown in Table 3, there was no significant difference in RVDD or LVDD
indices between SVD, 2 VD, and 3 VD patients before and after surgery (P
\textless{}0.05). Moreover, RVDD and LVDD index changes were not
significantly different before and after CABG in all patients (P
\textless{}0.05).

\textbf{Table 3:} \textbf{Comparison of RVDD and LVDD indices before and
one month after surgery between the groups.}\selectlanguage{english}
\begin{longtable}[]{@{}lllll@{}}
\toprule
Evaluation time & Grade & SVD \& 2VD & 3VD & P-value\tabularnewline
\midrule
\endhead
RVDD before surgery & Normal & 4 & 5 & 0.846\tabularnewline
& Mild & 12 & 10 &\tabularnewline
& Moderate & 4 & 5 &\tabularnewline
& Severe & 0 & 0 &\tabularnewline
& Total & 20 & 20 &\tabularnewline
RVDD after surgery & Normal & 3 & 5 & 0.231\tabularnewline
& Mild & 11 & 12 &\tabularnewline
& Moderate & 6 & 3 &\tabularnewline
& Severe & 0 & 0 &\tabularnewline
& Total & 20 & 20 &\tabularnewline
LVDD before surgery & Normal & 5 & 3 & 0.475\tabularnewline
& Mild & 11 & 12 &\tabularnewline
& Moderate & 4 & 5 &\tabularnewline
& Severe & 0 & 0 &\tabularnewline
& Total & 20 & 20 &\tabularnewline
LVDD after surgery & Normal & 4 & 5 & 0.820\tabularnewline
& Mild & 13 & 10 &\tabularnewline
& Moderate & 3 & 5 &\tabularnewline
& Severe & 0 & 0 &\tabularnewline
& Total & 20 & 20 &\tabularnewline
\bottomrule
\end{longtable}

2 VD: Two-vessel disease, SVD: small vessel disease, 3 VD: Three-vessel
disease. RVDD: Right ventricular diastolic dysfunction, LVDD: Left
ventricular diastolic dysfunction. Friedman test was used for comparison
between groups.

\textbf{Discussion}

The RV dysfunction following heart surgery is a well-known phenomenon
that occurs immediately following CABG. The RV contraction and filling
are impaired after surgery, but the exact mechanism remains unknown. All
patients undergoing heart surgery are likely to experience RV
dysfunction regardless of a cardiopulmonary pump, the duration of aortic
clamping, or the method used for cardioplegia or myocardial protection
(14). Although most studies have reported decreased RV function after
CABG surgery or during the immediate recovery period, long-term results
have not been studied. A significant reduction in the systolic
displacement of the tricuspid annulus has been observed immediately
after CABG that have indicated RV dysfunction, and the reduction
persists for up to 6 months after surgery. Tissue doppler velocity is a
relatively new way of evaluating myocardial function. The diastolic and
systolic velocities of the tricuspid annulus are recorded by tissue
Doppler velocity. They reveal RV systolic and diastolic function,
respectively, which decreases following RV infarction or cardiomyopathy
(14, 15). Charlie J et al. examined the effects of pericardial incision
on RV systolic function in twenty-four patients who underwent elective
on-pump CABG. At three times during surgery after sternotomy immediately
before pericardiotomy, after pericardiotomy and placement of pericardial
sutures, and after chest closure at a follow-up visit for
cardiopulmonary bypass, color tissue Doppler-derived isovolumic
acceleration (IVA), Speckle tracking-derived TAPSE, S', free wall
systolic strain, RV outflow tract strain, and two-dimensional RV
dimensions and fractional area change (FAC) were measured. As a final
result of this study, the evidence suggested that pericardial opening
does not influence RV systolic function indexes from speckle tracking or
tissue color Doppler. All RV systolic functions, including RV free wall
strain TAPSE, and RV SM were significantly reduced post-pericardiotomy,
compared with pre-pericardiotomy, while RVOT Strain and RV Diameter
remained unchanged (16). We obtained similar results in RVSM, TAPSE, and
RV Strain in this study, but our study was conducted after one month
following CABG, and the RV diameter changes were not the same as in our
study. Gozdzik et al. reported that after CABG surgery, Global
longitudinal strain echocardiographic parameters in the left ventricle
were reduced significantly six months after surgery in 63 patients (17).
Our follow-up period was three months instead of 6 months. We had a
smaller sample size than Gozdzik et al. and also the strain method was
not used to estimate LVEF in the present study. LVEF values were
measured globally, which increased significantly after surgery, and
there was no difference between LVDD and RVDD between patients before
and after CABG. Lue et al. demonstrated that the index of LVDD indexes
before and after CABG did not differ significantly, which is compatible
with the results of this study (18). On the other hand, in a study by
Bord et al that looked at changes in RV function after off-pump CABG,
patients' RVDD grade was normal before surgery but significantly
different after surgery (19). The reason for the discrepancy between the
results can be because, in the present study, most patients underwent
on-pump surgery; on the other hand, the second evaluation of patients
was done one month after surgery, while in this study, the second
evaluation was performed when patients were transferred to the ward.

The study had limitations because there was no access to a larger sample
size because of the COVID-19 pandemic and the reduction in surgical
candidates because of the current pandemic.

\textbf{Conclusion}

The RV diastolic function is significantly reduced after CABG surgery.
It is certain that without the pump, surgery cannot compensate for this
disorder and can't reduce its severity. Doppler tissue can be used to
evaluate RV function after surgery in a simple and non-invasive
procedure.

\textbf{Acknowledgement}

The present study was funded by Hamadan University of Medical Science
(No: 9606073688). The authors acknowledge the Vice Chancellor for
Research and Technology of Hamadan University of Medical Sciences and
the Clinical Research Development Unit of Farshchian Hospital in
Hamadan, Iran. In addition, the authors state there were no conflicts of
interest with the study's results.

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