QT Interval prolongation and dispersion: Epidemiology and clinical correlates in subjects with newly diagnosed systemic hypertension in Nigeria

BACKGROUND The use of easily obtainable clinical and laboratory parameters to identify hypertensive patients with increased cardiovascular risk in resource limited settings cannot be overemphasized. Prolongation of QT intervals and increased dispersion has been associated with increased risk of cardiovascular death. The study aimed at describing the epidemiology of QT interval abnormalities among newly diagnosed hypertensive subjects and associated clinical correlates. MATERIALS AND METHODS One hundred and forty newly diagnosed hypertensive subjects and 70 controls were used for this study. Clinical and sociodemographic characteristics were obtained. Twelve lead resting electrocardiography, QT dispersion, heart rate corrected minimum and maximum QT intervals were determined manually. Increased QTcmax was defined at QTcmax >440msec. QT parameters were compared between various groups. SPSS 16.0 was used for data analysis. RESULTS The hypertensive subjects were well matched in age and gender distribution with controls. QTmax and QTcmax were significantly higher among hypertensive subjects than controls (379.7±45.1 vs. 356.7±35.6, 447.5± 49.0 vs. 414.5 ±34.7 ms, respectively, P<0.05). QTd and QTcd were also significantly higher among hypertensive subjects than controls (62.64±25.65 vs. 46.1±17.2, 73.8 ±30.0 vs. 52.5±18.8, respectively, P<0.05). Seventy three (52.14%) of the hypertensive subjects had QTcmax >440ms compared to 21.43% of controls, P=0.01. Increased QTc dispersion was present in 36.4% of hypertensive subjects. Hypertensive subjects with QT abnormalities had significantly higher mean waist hip ratio, mean body mass index and a higher proportion of smoking than controls. CONCLUSION QT prolongation and increased QTc dispersion are common among newly diagnosed hypertensive Nigerians and seem to be significantly associated with obesity. Effective antihypertensive therapy and control of obesity are important management modality for newly diagnosed hypertensive patients.