Persistent tachycardia in clozapine treated patients: A 24-hour ambulatory electrocardiogram study

Tachycardia is associated with cardiovascular mortality. Tachycardia is also a known clozapine adverse effect. However, whether clozapine-associated tachycardia is persistent is not known. Thirty clozapine-treated patients with clinical tachycardia were investigated with 24-hour ambulatory electrocardiography (ECG). Baseline peripheral heart rate (HR) was 106.7 ± 7.8. The ambulatory ECG 24-hour-HR was 98.7 ± 9.7. Baseline HR and 24-hour-HR correlated strongly (r = 0.74, p = 0.000003). Daytime HR was 106.4 ± 9.9 and nighttime HR 89.2 ± 12.0. Low dose bisoprolol reduced HR significantly. The high 24-hour-HR indicates a persistent tachycardia. Tachycardia should not discourage from clozapine use but the findings indicate a need of guidelines for detection and treatment of clozapine-associated tachycardia.