Echocardiographic assessment of the right ventricular function in acute myocardial infarction

Abstract

BACKGROUND: 

Assessment of the right chamber function has not given much importance; this could be due to complex structure, asymmetric shape, and difficulty in visualization, and resulted in poor understanding of the impact of the right ventricular (RV) function on prognosis. Echocardiography commonly used and most readily available investigation modality for the assessment of the right ventricular function.

AIMS AND OBJECTIVES: 

The aim of this study was to evaluate the relation between RV function and left ventricle (LV) dysfunction and Killip class in acute myocardial infarction (AMI) exclusive of RV infarction.

MATERIAL AND METHODS: 

A total of 21 consecutive patients admitted to the coronary care unit with AMI were included and echocardiography was performed within 24 h of admission to assess RV and LV functions. RV function was quantified with a tricuspid annular plane systolic excursion (TAPSE), RV fractional area change (RVFAC), RV longitudinal strain, RV myocardial performance index (RVMPI), and compared with the LV ejection fraction and Killip class.

RESULTS: 

Statistical analysis revealed that the majority of patients were male (90.5%) and only 9.5% of patients were female with a mean age of 50.9 years. Anterior wall MI was more common (58%) than inferior wall MI (42%). The study findings revealed that the RV longitudinal strain had a significant negative correlation (r2 = 0.803, P = 0.001) with Killip class and LV ejection fraction, whereas TAPSE, RVMPI, and RVFAC were poorly correlated with RV dysfunction.

CONCLUSION: 

From the study findings, we concluded that echocardiographic assessment of RV functions demonstrated that larger infarcts correlated with RV dysfunction. RV involvement was more pronounced in anterior MI than inferior MI. Hence, the earliest recognition of RV dysfunction is warranted. Keywords: Acute myocardial infarction, echocardiograph, right ventricular function.

Introduction

Acute myocardial infarction (AMI) is characterized by a loss of contractile tissue and a change in ventricle geometry that causes a substantial impairment of the right ventricular (RV) and left ventricle (LV) systolic and diastolic functions.

Two-dimensional (2D) echocardiography is an indispensable and integral part of the clinical evaluation of patients with various cardiac diseases. However, most of the parameters derived from cardiac ultrasound examination mainly focus on the left chamber function, and less attention has been paid to the study and interpretation of the right chamber function, namely, the right ventricular (RV) systolic function. This may be due to the knowledge of RV function lagged behind the left ventricular (LV) function and less is understood about the physiologic and prognostic roles of the RV. Indeed, the inherent challenges in the accurate assessment of irregular-shaped RV cavities have hindered such progress.

Echocardiographic RV functional parameters have independent and additive prognostic value in patients with LV dysfunction.[¹] RV function is an important prognostic factor for clinical outcomes in patients with AMI of LV. Moreover, RV involvement occurs in a percentage of patients suffering an anterior wall MI (AWMI) and increases in-hospital death rates.[²]

Therefore, the aim of the present study was to investigate the relation between RV function and also to understand adverse events in post-AMI patients admitted to the coronary care unit. Hence, we investigated not only traditional measurements that are recommended to quantify RV function with 2D echocardiography, but also RV strain was assessed. This novel method enables direct quantification of myocardial deformation and is a sensitive tool to detect RV dysfunction. The present study aimed to identify the robust echocardiographic marker of right ventricular dysfunction in AMI.

Methodology

A total of 21 consecutive patients admitted to the coronary care unit with AMI were screened based on inclusion and exclusion criteria and were selected and enrolled in the study. The study procedures were well-explained, and written consent was obtained. For ethical clearance was obtained from St John's National Academy of Health Sciences Institutional Ethical Committee with Ref no IEC/1/570/2015 dated 22/6/2015. Echocardiography was performed within 24 h of admission to assess RV and LV functions.

All patients were treated according to the institutional AMI protocol, which is driven by the most current guidelines.[³] This protocol was designed to improve care around AMI and included structured medical therapy and outpatient follow-up. In addition, 2D echocardiography was also performed within 24 h of admission. This echocardiogram was used to assess LV and RV functions. All patients were followed prospectively and the occurrence of adverse events was noted.

Images were obtained with patients in the left lateral decubitus position using a commercially available system (Vivid E9, software beamformer platform – cSound™ 3.0, USA).

Data acquisition was performed at a depth of 16 cm in the parasternal and apical views using a 3.5-MHz transducer. During breath hold, M-mode and 2D images were obtained and three consecutive beats were saved in cineloop format. Analysis was performed offline by two independent observers using dedicated software (software beamformer platform – cSound™ 3.0). The reference limits of all echocardiographic parameters were defined according to the American Society of Echocardiography Guidelines.[⁴]

Left ventricle function analysis

The LV end-systolic volume and end-diastolic volume were assessed and LV ejection fraction (LVEF) was calculated using the biplane Simpson's method.[⁴]

Right ventricular function analysis

RV fractional area change (RVFAC) was analyzed by tracing the RV end-diastolic area (RVDA) and end-systolic area (RVSA) in the apical 4-chamber view using the formula (RVDA-RVSA)/RVDAX 100.[⁴]

Tricuspid annular plane systolic excursion (TAPSE) was calculated in the RV-free wall. In the 4-chamber view, the M-mode cursor was placed through the tricuspid annulus in a way that the annulus moved along the M-mode cursor and the total displacement of the RV base from end-diastole to end-systole was measured.[⁵]

Peak systolic longitudinal strain of the RV-free wall was measured in the 4-chamber view using speckle tracking analysis.[⁶] This is a novel software that analyzes motion by tracking frame-to-frame movement of natural acoustic markers in two dimensions. Every image was recorded with a frame rate of >40 fps for reliable analysis.

Manually, RV endocardial border was traced at end-systole and the automatically created region of interest was adjusted to the thickness of the myocardium. Peak systolic longitudinal strain was determined in the three segments of the RV-free wall (basal, mid, and apical), and RV strain was calculated as the mean value of all segments. Segments were discarded if tracking was of poor quality. Strain analysis was feasible in 85% of segments.

RV functions quantified with TAPSE, RVFAC, RV longitudinal strain, and RV myocardial performance index (RVMPI) were compared with the LV ejection fraction and Killip class. This study was approved by the ethics committee.

Inclusion criteria

• Patients with the first episode of acute ST-elevation myocardial
• Infarction excluding RVMI.

Exclusion criteria

• Patients with previous documented myocardial infarction
• Patients with previous documented right ventricular dysfunction.

Statistical analysis

Study data were collected and processed using Microsoft Excel – 365. Descriptive statistics were reported using mean and continuous variables using standard deviation. An Independent t-test was used to compare the mean RV strain and Killip groups. The correlation coefficient was used to assess the relationship between RV strain and ejection fraction. SPSS Version 22 IBM, USA was used to analyze the data.

Results

A total of 21 patients having AMI who underwent echocardiographic assessment were included in the study. Out of 21 patients, 19 (90.5%) were male and 2 (9.5%) were female. The mean age of the patients was 50.9 years.

Statistical analysis revealed that AWMI was more common (58%) than inferior wall MI, i.e., 42%. Among patients presenting with AMI, 5 (23.8%) patients were having a history of diabetics, 9 (42.9%) were having hypertension, 5 (23.8%) were dyslipidemic, and 7 (30.8%) were smokers. In the present study, Killip classes 2, 3, and 4 were clubbed into one group. There were 11 (52.4%) patients in Killip class 1 and 10 (47.6%) patients in Killip group 2. The mean RV longitudinal strain was − 24.8 + 3.0 in Killip class 1 and − 12 + 6.2 in Killip group 2.

Study findings revealed that the RV longitudinal strain had a significant negative correlation (r² = 0.803, P = 0.001) with Killip class and LV ejection fraction. TAPSE, RVMPI, and RVFAC are poorly correlated with RV dysfunction [Figures 1 and 2].

Figure 1: Correlation between RV strain and Killip class

Figure 2: Correlation between RV strain and LV ejection fraction. LV: Left ventricle

Discussion

The assessment of left ventricular (LV) function using 2D echocardiography shortly after AMI is essential and one of the most important prognostic parameters. However, the association between right ventricular (RV) function and adverse events after AMI is poorly known, especially in patients with mild LV dysfunction.[²] Due to therapeutic implications, there has been growing interest in the early recognition of RV infarction with noninvasive techniques. Zornoff et al. demonstrated that in patients with LVEF ≤40%, RV function was a significant independent predictor of death and development of heart failure after an AMI.[⁷] Thus, quantitative assessment of RV function after MI should be noted.

The results of the current study demonstrated that both anterior and inferior infarctions had marked effects on RV function. RV systolic and diastolic function indices were clearly impaired in a large number of participants with MI. Considering RV involvement in MI and its high mortality, more attention should be paid to the detection of RV function in AMI.[⁸] The results of a study suggested that RV function provided important information for prognosis after MI in patients.

Besides, another study on 423 patients with normal LV function revealed that reduced RVEF had a mild relationship with 1-year mortality.[⁹] In contrast, in a study on 416 patients with LV dysfunction, RV function independently predicted cardiovascular mortality.[⁷] These results show that changes in RV function subsequent to MI are closely related to LV alterations. However, in a meta-analysis conducted by Mehta et al., RV dysfunction in inferior infarction was not correlated to the extent of LV myocardial damage.[⁹] In addition to RVEF, RV Tei index, and systolic and diastolic tricuspid annular velocities are other indices used in the assessment of RV function. RV Tei index is important in the assessment of global RV performance and estimates RVEF with good accuracy.[⁹]

In another study, the tricuspid E/E' ratio and diastolic strain rate have been commonly used to evaluate RV diastolic function. These studies indicated a strong relationship between the tricuspid E/E' ratio and RA volume, and hemodynamic parameters.[¹⁰] Akdemir et al. also demonstrated that TAPSE, as an indicator of RV function, was lower in patients with acute anterior MI than in the control group in the absence of apparent systolic dysfunction. This was attributed to RV diastolic dysfunction.[¹¹] However, the results of our study particularly for this parameter were in contrast to the reported findings.

In the past, the clinical significance of RV function has been underestimated. Even though RV dysfunction was reported to recover to some extent after AMI, recently the value of RV function for the prediction of long-term outcomes has been well-documented in patients with inferior AMI and LV dysfunction.[^12,13] In a study done by Mehta et al.[¹⁴] showed in a meta-analysis that patients with RV involvement in inferior AMI were at a bigger risk of adverse events and established that RV involvement is not due to more extensive infarction of the LV. In post-AMI patients with LV dysfunction, studies by Anavekar et al.[¹⁵] and Zornoff et al.[⁷] confirmed that RV function is weakly correlated with LV function and demonstrated that RV function quantified with RVFAC was independently associated with an increased risk of mortality and HF.

Conclusion

Echocardiography provides a readily accessible tool for the evaluation of the right ventricular function and remains the first-line investigation due to its ability to provide comprehensive information on the right ventricular size, structure, and function. The early identification of a transient or permanent impairment of RV function is of pivotal importance in patients with an AMI not only for prognostic reasons but also for the specific management of these patients. RV assessment with these imaging modalities will have an increased value during treatment and quantitative assessment of RV function with RV strain may improve the risk stratification of patients after AMI.

Financial support and sponsorship

Nil.

Conflicts of interest

There are no conflicts of interest.