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

CARDIOVASCULAR JOURNAL OF AFRICA • Volume 32, No 5, September/October 2021 250 AFRICA Discussion In the majority of cases, PVCs have no known cause and occur spontaneously. Common known aetiologies include excess caffeine consumption, excess catecholamine levels, 5 high levels of anxiety, and electrolyte abnormalities. Specific electrolyte changes found in those who experience PVCs are low blood potassium and magnesium and high blood calcium levels. Alcohol, tobacco and illicit drugs are also associated with PVCs, as are stimulant-based medications. Patients suffering from sleep deprivation also experience PVCs. There are numerous cardiac and non-cardiac pathologies that are causative of PVCs. Examples include cardiomyopathy, mitral valve prolapse and myocardial infarction. Any structural heart disease that alters conduction pathways due to tissue alterations can cause PVCs. Non-cardiac examples are hyperthyroidism, anaemia and even hypertension. Patient populations with higher risks of cardiovascular disease and clinically poor cardiovascular markers have a higher occurrence of PVCs. 5 One pathophysiological reason for the occurrence of PVCs is ectopic nodal automaticity. This suggests that ectopic pacemaker cells carry a sub-threshold potential for firing. If the threshold is reached via the heart’s electrical activity, an ectopic beat occurs. A second pathophysiological explanation is re-entrant signalling. If one pathway of the Purkinje fibres is blocked and another pathway is experiencing slower conduction, this can trigger an ectopic beat on the post-block pathway. The final explanation for PVCs is that triggered beats occur due to after-depolarisations. 6 S ′ 4.0 6.0 8.0 10.0 12.0 PVC (%) 30.0 25.0 20.0 15.0 10.0 5.0 0 Fig. 1. Correlation between PVC% and S ′ . E/E ′ 0.0 10.0 20.0 30.0 40.0 PVC (%) 30.0 25.0 20.0 15.0 10.0 5.0 0 Fig. 2. Correlation between PVC% and E/E ′ . Table 2. Echocardiographic left ventricular parameters of the study groups Parameters Cases ( n = 100) Controls ( n = 100) p- value LVEDD (mm) 52.7 ± 9.1 49.9 ± 6.7 0.086 ¥ LVESD (mm) 35.3 ± 10.4 33.3 ± 7.0 0.576 § IVS (mm) 9.7 ± 2.3 8.8 ± 1.7 0.078 § PW (mm) 9.7 ± 2.2 9.2 ± 2.0 0.341 § LVEDV (ml) 80.8 ± 29.7 67.7 ± 24.8 0.019* ¥ LVESV (ml) 37.9 ± 18.9 30.0 ± 14.8 0.023* ¥ LVEF by M-mode (%) 56.4 ± 11.6 60.3 ± 9.5 0.099 c LVEF by biplane (%) 53.7 ± 10.7 56.0 ± 8.0 0.227 a MAPSE 10.5 ± 2.3 10.8 ± 1.9 0.632 c S ′ 7.9 ± 2.0 8.0 ± 1.9 0.711 a E ′ 6.4 ± 1.9 7.9 ± 3.1 0.010 c * E 75.1 ± 26.7 73.8 ± 23.3 0.689 c A 72.5 ± 15.5 69.6 ± 17.2 0.324 c E/A 1.1 ± 0.4 1.5 ± 2.9 0.337 c E/E ′ 12.5 ± 5.3 10.9 ± 5.7 0.044 c * LVEDD, left ventricular end-diastolic diameter; LVESD, left ventricular end- systolic diameter; IVS, interventricular septum; PW, posterior wall; LVEDV, left ventricular end-diastolic volume; LVESV, left ventricular end-systolic volume; LVEF, left ventricular ejection fraction; MAPSE, mitral annular plane systolic excursion. a Student’s t -test; c Mann–Whitney test; *statistically significant at p < 0.05. Table 3. Correlation between PVC% and basic data and echocardiographic parameters of the study subjects (cases = 100) Parameters PVC % Correlation coefficient p- value Age (years) 0.200 0.046 a * Height (cm) 0.102 0.312 b Weight (kg) 0.077 0.444 b BMI (kg/m 2 ) –0.016 0.876 b LVEDD (mm) 0.242 0.015 b * LVESD (mm) 0.116 0.251 b IVS (mm) 0.138 0.171 b PW (mm) 0.116 0.250 b LVEDV (ml) 0.287 0.004 b * LVESV (ml) 0.275 0.006 b * LVEF by M-mode (%) –0.235 0.019 b * LVEF by biplane (%) –0.367 < 0.001 a * MAPSE –0.129 0.201 b S ′ –0.327 0.001 a * E ′ –0.328 0.001 b * E 0.005 0.962 b A 0.080 0.426 b E/A –0.050 0.624 b E/E ′ 0.313 0.002 b * PVC, premature ventricular complex; BMI, body mass index; LVEDD, left ventricular end-diastolic diameter; LVESD, left ventricular end-systolic diam- eter; IVS, interventricular septum; PW, posterior wall; LVEDV, left ventricular end-diastolic volume; LVESV, left ventricular end-systolic volume; LVEF, left ventricular ejection fraction; MAPSE, mitral annular plane systolic excursion. a Pearson’s correlation; b Spearman’s correlation; *statistically significant at p < 0.05