Relation of B-type natriuretic peptide level in heart failure to sudden cardiac death in patients with and without QT interval prolongation

Abstract

Increased levels of B-type natriuretic peptide (BNP) are associated with prolongation of the action potential in ventricular myocardium. We investigated the relation of a BNP increase, QT interval, and sudden cardiac death (SCD) in the presence of heart failure (HF). We enrolled 398 patients with HF, New York Heart Association class III or IV, and left ventricular ejection fraction <40%. At baseline and after 3 months, we measured BNP and the QT interval. A BNP increase was defined as a change in BNP of ≥+10%. The QTc interval was calculated using the Bazett formula. QTc interval prolongation was defined as a change in QTc of ≥+10%. The patients were followed up for 1 year. During a 3-month period, BNP increased significantly in 53% of the patients (group 1) and did not in 47% (group 2). During the same period, the QTc interval was more prolonged in group 1 (+44 ± 12 ms) than in group 2 (+7 ± 6 ms; p = 0.01). During 1 year of follow-up, 20 patients died suddenly (SCD), 16 from pump failure. Although the SCD rates did not differ between the 2 groups (5.7% in group 1 vs 4.2% in group 2, p = 0.53), they were significantly greater in the patients in group 1 with QTc interval prolongation ≥+10% (13.8%, p <0.001). The Kaplan-Meier-derived SCD-free survival rates were 2.9 times greater in patients without QTc interval prolongation than in those with prolonged QTc (p <0.001). QTc interval prolongation was an independent correlate of SCD (p = 0.006), but BNP increase was not (p = 0.32). In conclusion, a BNP increase in patients with HF was associated with an increased risk of SCD only in patients with QTc interval prolongation.