CARDIOVASCULAR JOURNAL OF AFRICA • Volume 34, No 4, September/October 2023 AFRICA 219 including those with known chronic interstitial lung disease, chronic obstructive pulmonary disease, bronchial asthma, primary pulmonary arterial hypertension and congenital heart disease. Applying a prevalence of RVSD of 19.7% among HF patients and a 5% margin of error, a minimum sample size requirement of 244 patients was estimated.8 Clinical and demographic data, including co-morbidities, medication use and clinical features of HF were collected. Each participant had a 12-lead electrocardiogram (ECG) performed and interpreted using standard criteria.9 All participants had standard two-dimensional (2D), M-mode, and Doppler TTE studies performed using a commercially available ultrasound machine (Vivid T8 dimension ultrasound imaging system, GE Healthcare Bio-sciences Corp, Piscataway, NJ, USA) equipped with a 3.5-MHz phased array probe with the patient in the left lateral decubitus position. Measurements were taken in accordance with the recommendations of the American Society of Echocardiography.10 Each echocardiogram was analysed for pericardial disease, chamber size and wall dimension, wall motion abnormalities, ventricular function, valve morphology and function, intramural thrombi and congenital defects. For patients in atrial fibrillation, all measurements were averaged over five cardiac cycles, based on the guideline.11 RV systolic function was assessed using the tricuspid annular plane systolic excursion (TAPSE), the peak velocity of the tricuspid annulus in systole (RV S′), the 2D right ventricular fractional area change (RV FAC) and the right ventricular myocardial performance index (RV MPI).12 The presence of RVSD was suggested by the detection of at least one abnormal measurement of these parameters. TAPSE was measured in the standard apical four-chamber view by placing the M-mode cursor through the lateral tricuspid annulus under 2D echocardiographic guidance and measuring the maximum systolic excursion of the lateral tricuspid annulus during held end-expiration. A TAPSE value of < 1.6 cm was considered evidence of impaired RV systolic function. The RV S′ was obtained using pulsed tissue Doppler by placing the sample volume on the lateral tricuspid annulus in the apical four-chamber view during held end-expiration with minimal angulation. The highest systolic velocity (RV S′) was recorded and values < 10 cm/s represented evidence of impaired RV systolic function. From the same pulsed tissue Doppler signal, the tricuspid closure–opening time (TCOT) and the tricuspid valve ejection time (TV ET) were measured and the RV MPI was calculated as the ratio: RV MPI = (TCOT–TV ET)/TV ET. An RV MPI of > 0.55 represented evidence of RV dysfunction.12 The RV FAC was obtained by tracing the RV endocardium in the apical four-chamber view with a focus on the right ventricle at end-diastole and end-systole. Two-dimensional RV FAC was calculated as follows: RV FAC = [(RV end-diastolic area – RV end-systolic area)/ end-diastolic area] × 100. A value < 35%was taken as evidence of RV systolic dysfunction.12 Participants with a left ventricular ejection fraction (LVEF) of at least 50% and evidence of LV diastolic dysfunction were classified as HF with preserved ejection fraction (HFpEF). Those with a LVEF < 40% were classified as HF with reduced ejection fraction (HFrEF), while those with a LVEF in the range of 40–49% were classified as HF with mildly reduced ejection fraction (HFmrEF). The aetiology of the left HF was decided on the basis of the history, physical examination, ECG and echocardiography, as well as a review of relevant investigations, according to the guidelines of the European Society of Cardiology on the diagnosis and treatment of HF.13 The study complied with the principles outlined in the Declaration of Helsinki on the ethical principles for medical research involving human subjects. The study protocol was approved by the KBTH Institutional Review Board (protocol number KBTH-IRB/000121/2019). Statistical analysis Categorical variables, presented as counts and percentages, were compared using the chi-squared (χ2) or Fisher’s exact test, as appropriate. Continuous variables are summarised as their means with standard deviation or as medians with interquartile ranges. The means of two groups of continuous variables were compared with the independent samples Student’s t-test for normally distributed data or the Mann–Whitney U-test for skewed data. The associations between continuous variables were assessed by the Pearson’s correlation coefficient. Multivariate regression models were constructed to assess the relationship of RVSD and other variables that showed a statistically significant correlation with RV FAC, TAPSE, RV S′ and RV MPI in the univariate analyses at an alpha level of 0.05. The variables tested include those hypothesised to contribute to RV dysfunction, including heart failure aetiology, heart rhythm, LV function, pulmonary pressure and HF therapy. Receiver operating characteristic (ROC) curve analysis was employed as appropriate to evaluate the discriminatory value of echocardiographic variables that showed a significant independent predictive value for RVSD. The optimal cut-off value was chosen as the value maximising sensitivity plus specificity. All tests were two-tailed and a p-value < 0.05 was regarded as statistically significant. Data transformations and analysis were performed with the Statistical Package for the Social Sciences version 20.0 software (SPSS, IBM Corporation, Armonk, NY, USA). Results A total of 270 participants were recruited for the study, of whom 132 (48.9%) were female. Among those with HFrEF, 53.3% were taking a renin–angiotensin system inhibitor, 35.6% were on beta-blockers and 28.1% took mineralocorticoid receptor antagonists. The median duration of treatment received before enrolment was 2.0 weeks (0.0–24.0). Table 1 compares the baseline characteristic of the participants based on the presence or absence of RVSD. The rhythm was sinus in 90.7% of the participants and 7.0% had atrial fibrillation or flutter. Repolarisation abnormality, comprising abnormal ST-segment deviation and/or T-wave abnormalities, was a common finding (93.0%) and was present in a significantly higher proportion of those with RVSD (p < 0.001). Overall, 94.0% of those without RVSD and 99.0% of those with RVSD were judged to have abnormal ECGs (p = 0.035).
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