Effect of bisoprolol on QT dispersion in patients with congestive heart failure — The etiology-dependent response

Aims: To evaluate the effect of β1-selective blocker bisoprolol on the QT and QTc dispersion in patients with chronic heart failure and to compare the responses to bisoprolol in patients with different etiologies. Methods and results: Eighty-one patients with heart failure secondary to ischemic heart disease (n=47) or idiopathic dilated cardiomyopathy (n=34) were stratified by etiology and then randomly assigned to the bisoprolol and control group (no tablet) on top of the conventional treatment. QT dispersion was calculated by subtracting the shortest QT from the longest QT, in absolute value (Qtmax−Qtmin). It was also corrected with Bazett’s formula (QTc dispersion). After 6 weeks of treatment, QT and QTc dispersion were significantly decreased in the bisoprolol group (QT dispersion: 66.5±13.4 ms vs. 49.1±16.8 ms for ischemic heart disease (P<0.01); 67.5±12.4 ms vs. 59.4±14.4 ms for dilated cardiomyopathy (P<0.05); QTc dispersion: 78.3±15.2 ms vs. 53.3±18.1 ms for ischemic heart disease (P<0.01); 79.1±14.2 ms vs. 69.0±17.9 ms for dilated cardiomyopathy (P<0.05)), but there was no significant decrease of QT and QTc dispersion in the control group. Linear regression analysis showed that patients with ischemic heart disease tend to have lower 6-week QT dispersion than patients with dilated cardiomyopathy (coefficient β=−0.283, P=0.009) after controlling for their baseline values in the bisoprolol group. Conclusion: These findings suggested that bisoprolol reduces QT and QTc dispersion in patients with chronic heart failure, but the etiology of heart failure affects the response of patients to bisoprolol.