Cardiovascular Journal of Africa: Vol 32 No 5 (SEPTEMBER/OCTOBER 2021)

CARDIOVASCULAR JOURNAL OF AFRICA • Volume 32, No 5, September/October 2021 AFRICA 249 recordings; PVC frequency: the number of PVCs in 24 hours; PVC morphology: defined as right bundle branch block pattern if the QRS complex was positive in lead V1 or left bundle branch block pattern for negative QRS in V1. • echocardiographic assessment. A conventional echocardio- graphic study was performed using the standard parasternal long-axis, short-axis, and apical two- and four-chamber views at rest using a commercially available system (General Electric Healthcare Company, Vivid seven Dimensions Vingmed and Horten, Norway) with a 2.5-MHz phased-array probe. Two independent experts in echocardiography interpreted all echocardiographic data. LV size was routinely assessed on two-dimensional echocardiography (2D) by calculating volumes using the biplane method of disk-summation. LV size and volume measurements were reported indexed to body surface area. Global LV function was usually assessed by measuring the difference between the end-diastolic volume (EDV) and end-systolic volume (ESV). LVEF is calculated from EDV and ESV estimates, using the following formula: LVEF = ​ (EDV – ESV) ___________ EDV ​ The biplane method of disks (modified Simpson’s rule) is the currently recommended 2D method to assess LVEF. Diastolic function was also evaluated using Doppler flow on the mitral valve. The E/A ratio was calculated from the difference between the peak mitral inflow velocity in early diastole (E wave) and the peak mitral inflow velocity in late diastole (A wave). Pulsed tissue Doppler imaging (TDI) is a technique that allows the recording of instantaneous maximal velocities within a predefined volume-sampling region in real-time by selecting a single sample volume in TDI. High temporal resolution is achieved. Among all the parameters that could be measured, peak annular velocity (Sm) is the most commonly used for estimating the global LV long-axis systolic function. The filling pressure (E/E ′ ) is calculated from the ratio of E ′ wave detected by tissue Doppler early diastolic relaxation velocity and peak mitral inflow velocity in early diastole, determined from tissue Doppler early diastolic relaxation velocity. This studywas conductedwith the approval of the institutional review board of the Suez Canal University. Statistical analysis An Excel spreadsheet was created for the entry of data. We used validation checks on numerical variables and an option-based data-entry method for categorical variables to reduce potential errors. The analyses were carried out with SPSS software (Statistical Package for the Social Sciences, version 24, SSPS Inc, Chicago, IL, USA). Frequency tables with percentages are used for categorical variables, and descriptive statistics [median and interquartile range (IQR)] are used for numerical variables. The independent Student t -test, paired t -test or Mann– Whitney test were used to compare quantitative variables, while the chi-squared or McNemar–Bowker tests were used to analyse categorical variables. Pearson’s correlation coefficient was used to measure the strength and direction of the linear relationship between two continuous variables. A p -value < 0.05 was considered statistically significant. Results Our study included a control group (100 subjects) with PVC burden ≤ 1% and a study group (100 patients) with PVC burden > 1%. Both groups were age and gender matched and had nearly equal risk factors such as diabetes mellitus, hypertension, dyslipidaemia and coronary artery disease. Table 1 shows the differences in basic data between the groups. The highest PVC burden was 29% while the mean PVC burden was 7.0 ± 6.4% in the study group and 0.6 ± 0.2% in the control group ( p < 0.001). Otherwise, there were no significant differences between the two groups regarding the rest of their basic data. Table 2 shows that although mean LVEDV was in the normal range, it was significantly higher in the cases (80.8 ± 29.7 ml) than the controls (67.7 ± 24.8 ml) ( p = 0.019). Mean LVESV was also in the normal range but was higher in the cases (37.9 ± 18.9 ml) than the controls (30.0 ± 14.8 ml) ( p = 0.023), reflecting significant LV volumetric difference. Mean E ′ was significantly higher in the controls (7.9 ± 3.1) than the cases (6.4 ± 1.9) ( p = 0.010) while mean E/E ′ was significantly higher in the cases (12.5 ± 5.3) than the controls (10.9 ± 5.7) ( p = 0.044), reflecting significant LV diastolic functional difference. However, LVEF by M-mode and biplane imaging showed no significant difference between the groups. Table 3 shows that a statistically significant correlation was detected between PVC burden and each of LV end-diastolic diameter (LVEDD) ( r = 0.242, p = 0.015), LVEDV ( r = 0.287, p = 0.004) and LVESV ( r = 0.275, p = 0.006), which reflects a significant LV volumetric effect of PVC. There was a statistically significant inverse correlation between PVC burden and LVEF by M-mode ( r = –0.235, p = 0.019) and biplane imaging ( r = –0.367, p < 0.001) and S ′ ( r = –0.327, p = 0.001) (Fig. 1). There was a statistically significant inverse correlation between PVC burden and E ′ (r = –0.328, p = 0.001). E/E ′ showed a direct correlation with percentage PVC that was also statistically significant ( r = 0.313, p = 0.002) (Fig. 2). All of them reflected the significant LV systolic and diastolic functional effects of PVC burden. Table 1. Basic data of the study groups Parameters Cases ( n = 100) Controls ( n = 100) p- value Age (years) 58.6 ± 7.5 57.4 ± 7.5 0.124 a Gender, n (%) Male 52 (52) 50 (50) 0.317 ¶ Female 48 (48) 50 (50) Height (cm) 163.5 ± 7.9 160.9 ± 8.8 0.122 a Weight (kg) 85.2 ± 16.5 85.2 ± 16.5 0.385 a BMI (kg/m 2 ) 31.6 ± 6.5 31.8 ± 6.2 0.854 a DM, n (%) 44 (44) 58 (58) 0.161 b IHD, n (%) 58 (58) 52 (52) 0.564 b HTN, n (%) 58 (58) 50 (50) 0.422 b PVC% 7.0 ± 6.4 0.6 ± 0.2 < 0.001 c * Morphology, n (%) LBBB 74 (74) 82 (82) RBBB 26 (26) 18 (18) BMI, body mass index; DM, diabetes mellitus; IHD, ischaemic heart disease; HTN, hypertension; PVC, premature ventricular complex; LBBB, left bundle branch block; RBBB, right bundle branch block. a Student’s t -test; b chi-squared test; c Mann–Whitney test; *statistically significant at p < 0.05.