Prevalence of QTc prolongation in adult Nigerians with chronic heart failure

The heart rate corrected QT interval (QTc) on the electrocardiogram (ECG) has been proposed as a risk factor for ventricular arrhythmias and death in apparently healthy populations, patients with myocardial infarction and diabetes mellitus. However, data on the significance of QTc prolongation in heart failure are scarce.

Our objective was to examine the prevalence of QTc prolongation in adult Nigerians with heart failure and its association with arrhythmias.

Ninety consecutive patients with heart failure were recruited along with 90 age-and sex-matched controls. All the subjects had a 12-lead ECG and a rhythm strip (lead II). The latter was used to calculate the QTc using the Bazett's formula. Left ventricular systolic and diastolic functions were assessed using a 2D guided m-mode and Doppler echocardiogram respectively.

The mean age of the patients was 51.9 (16) years compared with 50.3 (15.2) years for the control group, p = 0.47. Mean left ventricular ejection fraction was significantly lower in the patients than in the controls (38.9 (11)% versus 72.2 (8)%), p = 0.001. The mean QTc was significantly prolonged in the patients than in the controls (0.472 (0.036) versus 0.390(0.032) respectively), p = 0.001. The prevalence of QTc prolongation was 63% in the patients against 4.4% in the controls. There was a significant association between ventricular arrhythmias and QTc prolongation.

The results of this study shows that there is a high prevalence of QTc prolongation in adult Nigerians with heart failure and this may be harbinger for ventricular arrhythmias and sudden death.