QT interval dispersion as a predictor of arrhythmic events in congestive heart failure. Importance of aetiology

Abstract

Aims: Identification of patients with congestive heart failure at risk of sudden death remains problematic and few data are available on the prognostic implications of QT dispersion. We sought to assess the predictive value of QT dispersion for arrhythmic events in heart failure secondary to dilated cardiomyopathy or ischaemic heart disease.

Methods and results: Twelve-lead ECGs calculated for QT dispersion, 24 h Holter ECGs and signal-averaged ECGs were prospectively recorded in 205 heart failure patients in sinus rhythm. The 86 patients with ischaemic heart disease and the 119 with dilated cardiomyopathy were not significantly different as regards NYHA grades (51 vs 49% in grades III-i.v.), cardiothoracic ratio (57 +/- 7 vs 57 +/- 6%) and ejection fraction (28 +/- 8 vs 29 +/- 9%). The mean QT dispersion (66 +/- 29 vs 65 +/- 27 ms), the frequency of non-sustained ventricular tachycardia (37 vs 38%) and ventricular late potentials (41 vs 40%) were not significantly different in patients with ischaemic or dilated cardiomyopathy. QT dispersion was significantly related to other arrhythmogenic markers. During follow-up (24 +/- 16 months), 66 patients died, 22 of them died suddenly and seven presented a spontaneous sustained ventricular tachycardia. In patients with dilated cardiomyopathy, in multivariate analysis, only a QT dispersion > 80 ms was an independent predictor of sudden death (RR: 4.9, 95% CI 1.4-16.8, P < 0.02) and arrhythmic events (RR: 4.5, 95% CI 1.5-13.5, P < 0.01). In patients with ischaemic heart disease, no studied parameter was found significantly related to sudden death or arrhythmic events.

Conclusions: In congestive heart failure, abnormal QT dispersion can identify patients with dilated cardiomyopathy who are at high risk of arrhythmic events.