QT dispersion and risk factors for sudden cardiac death in patients with hypertrophic cardiomyopathy

This study examines the relation of QT dispersion (QTd) on a surface electrocardiogram (ECG) to clinical features and established risk factors of sudden cardiac death (SCD) in patients with hypertrophic cardiomyopathy (HC). One hundred fifty-six consecutive patients with HC (91 men, mean age 41 ± 15 years, range 7 to 79) and 72 normal subjects (41 men, mean age 39 ± 9 years, range 20 to 60) were studied. Standard 12-lead ECGs were recorded from each subject using a MAC VU electrocardiograph. Patients with nonsinus rhythm, atrioventricular conduction block, QRS duration >120 ms, age <15 years, and low amplitude T waves were excluded from the analysis (n = 51). Another 22 patients who were receiving amiodarone and/or sotalol therapy were also excluded. QT interval and QTd were measured using automated analysis in the remaining 83 patients (46 men, age 40 ± 14 years, range 16 to 76). QT interval (406 ± 38 ms), QTc interval (432 ± 27 ms), and QTd (43 ± 25 ms) were significantly greater in patients with HC than in normal controls (386 ± 31 ms, 404 ± 16 ms, 26 ± 16 ms, respectively) (p <0.0001). QTd was significantly greater in patients with HC with chest pain compared with asymptomatic or mildly symptomatic patients (50 ± 28 ms vs 37 ± 20 ms, p = 0.02). Increased QTd was found in patients with dyspnea New York Heart Association functional classes II/III than in those with dyspnea New York Heart Association functional class I (50 ± 27 ms vs 38 ± 22 ms, p = 0.04). QTd was weakly correlated with maximum left ventricular wall thickness (r = 0.228, p = 0.038). No significant association was found between QTd and any risk factors for SCD. Thus, patients with HC have increased QTd. The QTd correlates with symptomatic status. Assessment of QTd might provide complementary clinical characterization of patients with HC but its relation to SCD remains uncertain.