Acute myocardial infarction (AMI) is a major cause of coronary heart disease, in spite of breakthrough advancements in percutaneous coronary interventions (PCI) over the past few years. Right ventricular (RV) dysfunction after AMI has emerged as a potent predictor for increased events of mortality and morbidity.[2,3] The prevalence of RV dysfunction has been reported in 50% of patients with inferior wall myocardial infarction (IWMI) and 10% of patients with anterior wall MI.[4,5] Furthermore, severe RV dysfunction is associated with right coronary artery (RCA) occlusion proximal to the major RV branches.[6,7] Of note, RV dysfunction affects left ventricular function by limiting left ventricle preload. It also causes an adverse effect on systolic and diastolic interactions through the intraventricular septum and the pericardium (ventricular coupling). Thus, the diagnosis of RV dysfunction is of utmost importance. Although several studies have assessed the role of left ventricular function in the prognosis of AMI patients, little attention has been paid to the role of systolic and diastolic RV functions. This can be due to diagnostic limitations of the electrocardiogram and echocardiography of the irregular-shaped right ventricle.[9,10] Toward this end, the aim of this study is to examine the effect of RCA revascularization on systolic and diastolic functions of the right ventricle following acute IWMI. It also analyses the response of RV function in each RCA segment following PCI.
SUBJECTS AND METHODS
This was a single-center, prospective interventional study that comprised 59 adult patients (age >18 years), who were referred to a tertiary health-care center between April 2018 and January 2020. Patients who were diagnosed with acute IWMI with an angiographic diagnosis of isolated RCA lesion following PCI were included, irrespective of the thrombolysis status. The exclusion criteria in the study were: (1) stable ischemic heart disease, (2) angiographic evidence of significant lesion in arterial territory other than RCA, (3) history of chronic obstructive pulmonary disease or any other chronic respiratory conditions, (4) history of coronary artery bypass grafting or valvular surgery or previous PCI, (5) history of renal or hepatic failure, or (6) history of cardiomyopathy. Data regarding demographic, lesion characteristics, and echocardiographic parameters were noted. The endpoint of the study was improvement of RV dysfunction following PCI. The study complied with the Declaration of Helsinki and was approved by the Institutional Ethics Committee. All patients had provided written informed consent.
Before PCI, the patients were evaluated by two-dimensional (2D) echocardiography using the Esaote MyLab™X7 machine system. Primary PCI was performed using ultrathin (60 mm) Supralimus Grace™ sirolimus-eluting stent (Sahajanand Medical Technologies, Surat, Gujarat) within 24 h of 2D echocardiography. After PCI, 2D echocardiography was performed with Esaote MyLab™X7 machine system within 24–48 h. Left ventricular functions were assessed as the percentage of change in the ventricular cavity area from end-diastole to end-systole and left ventricular ejection fraction (LVEF) was evaluated.
The following parameters were measured to assess the RV functions in the RV-focused apical four-chamber view: (1) tricuspid annular plane systolic excursion (TAPSE) was measured using M-mode echocardiography with the cursor optimally aligned along the direction of the lateral tricuspid annulus, (2) RV fractional area change (RVFAC) was calculated using the following formula: (end-diastolic area × end-systolic area)/end-diastolic area, (3) pulsed Doppler S wave (cm/sec) and color tissue Doppler S wave (cm/sec) measured peak systolic velocity (S’ velocity) of tricuspid annulus, (4) Doppler velocities of tricuspid early RV filling velocity (E) and late RV filling velocity (A) were evaluated, and (5) tissue Doppler imaging (TDI) study measured early diastolic tricuspid annulus velocity (e’) and late diastolic tricuspid annulus velocity (a’), thus evaluated E/e’ ratio. The reference limits of all the echocardiographic parameters were adopted from recommendations established by the joint venture of the American Society of Echocardiography and the European Association of Cardiovascular Imaging. As per these guidelines, the abnormality threshold criteria for RV systolic dysfunction parameters were TAPSE <17 mm, RVFAC <35%, and S’ velocity <10 cm/s. On the other hand, the abnormality threshold criteria for RV diastolic dysfunction parameters were E/A <0.8 and E/e’ ≥4.0.
Quantitative data are presented as mean ± standard deviation, and qualitative data are presented as frequencies. For categorical variables, comparisons between pre- and post-PCI were performed using McNemar’s test. A P < 0.05 was considered statistically significant. The statistical analyses were performed using the Statistical Package for the Social Sciences (SPSS) statistical software, version 15 (SPSS, Inc., Chicago, Illinois, USA).
Out of 59 patients, 41 (69.5%) were male and 18 (30.5%) were female. The mean age of the population was 54 ± 8.2 years. No serious periprocedural complication was noted in any of the patients after successful PCI. Baseline demographics and lesion characteristics of the study population are shown in Table 1. The mean LVEF of the study population was 58.6 ± 6.0%.
A comparison of the echocardiographic systolic parameters of the right ventricle before and after PCI is delineated in Table 2. Of total patients, RV function based on TAPSE improved statistically in proximal (P = 0.031) and mid RCA (P = 0.004) following PCI. There was a significant difference in RV function after PCI in mid RCA (P = 0.008) based on S’ velocity. As per RVFAC, the improvement of RV function was found significant in proximal (P = 0.004) and mid RCA (P = 0.016) following PCI.
The echocardiographic diastolic parameters of the right ventricle before and after PCI are highlighted in Table 3. The RV function improved significantly based on the E/A ratio in proximal (P = 0.039) and mid RCA (P = 0.016) following PCI, whereas the RV function was found significant only in proximal RCA (P = 0.021) based on E/e’ ratio after PCI.
The overall changes in the echocardiographic systolic parameters in patients with RV dysfunction following PCI are presented in Table 4. RV function was improved in 81.82% of patients for TAPSE <17 mm, in 68.18% of patients for S’ velocity ≤10 cm/s, in 90% of patients for RVFAC <35%. There was an overall improvement of RV function in echocardiographic diastolic parameters in 75% of patients for E/A <0.8 following PCI, whereas 14.29% of patients were unremarkably improved for E/e’ ≥0.4 as demonstrated in Table 5.
In the present study, systolic and diastolic echocardiographic parameters of RV function following RCA revascularization were significantly improved. However, this improvement was found in the proximal and mid part of RCA in TAPSE, RVFAC, and E/A. Significant improvement was found in the proximal part of RCA for E/e’ and mid part of RCA for S’ velocity. Nonetheless, the improvement was not found in the distal part of RCA for all parameters. Similarly, Nikdoust et al. and Hsu et al. reported significant improvement in the proximal RCA revascularization.[11,12] Furthermore, our study showed rapid recovery in RV function of AMI patients, which was also reported by previous investigations.[5,13,14] This shows the importance of revascularization of the affected RCA.
The right ventricle is different from the left ventricle with relevance to various anatomic and physiologic characteristics, yet they are related to each other. The shape, size, and conformity of one ventricle influence the hemodynamic features of the other ventricle, which is termed ventricular coupling. Being a part of the right ventricle, the interventricular septum is influenced more by the left ventricle compared to the right ventricle, irrespective of advanced RV dysfunction, or severe pulmonary hypertension. Moreover, the involvement of the interventricular septum in the evaluation of global RV function is of great challenge. Approximately 66% of the right ventricle is perfused with blood by the RCA in 85% of the world’s population through the posterolateral artery, atrioventricular nodal artery, and posterior descending artery. The inferior wall of the right ventricle is easily affected by ischemia, whereas the infundibulum and anterior wall are unaffected segments. Owing to the fact that the severity of RV dysfunction is based on the region of RCA occlusion, data pertaining to the lesion sites, collateral vessels, and dominancy or codominancy is of paramount importance.
Previously, Hsu et al. have also stated that the region of coronary artery involvement may have a significant impact on RV function. Patients who were suffering from inferior infarction and without concomitant RV infarction, major echocardiographic parameters of RV function were identical in healthy individuals except for RV diastolic function. On the other hand, the variation in global RV function has been more prominent in patients with anterior wall infarction.
In the present study, the majority of patients with RV dysfunction had a proximal RCA lesion (69.2%), followed by a mid RCA lesion (29.4%), and a distal RCA lesion (25%). Similarly, Nikdoust et al. found that patients with proximal RCA involvement experienced RV dysfunction. Bowers et al. also identified a higher prevalence of RV dysfunction in 125 patients with IWMI and RV dysfunction in the proximal RCA (71%) than in the mid RCA (23%) or the distal RCA (6%). This study also found that the state of RV branch perfusion was a major factor in the determination of RV performance. The occlusion in the proximal RCA lesion usually affected the RV branch perfusion which leads to RV ischemic dysfunction. On the other hand, distal RCA occlusions seldomly affected RV branch perfusion. In a study of 67 patients with the first episode of acute IWMI, Rajesh et al. demonstrated that RV function indices such as TAPSE, myocardial performance index-TDI, and S′ velocity were found to be useful in prognosticating proximal RCA stenosis in the first episode of acute IWMI. In line with previous studies,[11,17,18] it can be postulated that the higher the incidence of proximal RCA critical lesion, the higher the likelihood of developing the RV dysfunction.
Many previous studies showed a significant association between echocardiographic parameters of RV function and LVEF.[19–22] Conversely, the present study has not investigated any correlation between echocardiographic parameters of RV function and LVEF. Furthermore, the recovery of RV function found significant following revascularization in all echocardiographic parameters. These parameters contribute as independent predictors for RV function.
The present study has several limitations that need to be acknowledged. First, it was a single-center study with small sample size, so this study’s outcome may not be extrapolated to the general population. Second, the patients with single vessel (i.e., RCA) coronary artery disease were included in this study. Presumably, patients with multivessel coronary artery disease may adversely affect the RV function. Finally, no investigation was done on the size and length of the stents used during RCA revascularization.
The findings of this study have shown significant improvement in systolic and diastolic RV functions after the RCA revascularization in proximal and mid RCA. Further studies with large sample sizes along with multivessel coronary artery disease are needed to be performed. In addition, the stent profile and the anatomical features of the stenotic artery should be taken into consideration.
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Conflicts of interest
There are no conflicts of interest.
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