[The QTc interval and its dispersion in hypertrophic myocardiopathy--its relation to complex ventricular arrhythmias and the effect of anti-arrhythmia agents].

UNLABELLED

The aim of the present study was to evaluate, in patients with hypertrophic cardiomyopathy (HCM): 1. The relation of rate corrected QT interval (QTc) and of QTc interlead variability (QTc dispersion) to complex ventricular arrhythmias (CVA); 2. The effects of amiodarone (Am), beta-blockers (beta B) and calcium antagonists (CA) on QTc and on QTc dispersion. Surface 12 leads ECG was analysed in 55 patients with HCM (39 +/- 12 years, 32 males). All patients were in sinus rhythm, without bundle branch block. Maximum (max), minimum (min) and mean QTc values were considered. QTc dispersion was calculated as: a) max QTc - min QTc (max-min); b) dispersion index (DI) = standard deviation of QTc/mean QTcx100. Patients groups were defined accordingly to: 1--the absence (group A1-35 patients) or the presence (group A2-20 patients) of CVA on 24 hours Holter monitoring; II--absence of cardioactive medication (group B1-20 patients) versus monotherapy with Am (group B3-10 patients), or beta B (group B4-15 patients), or CA (group B5-10 patients). Age, gender, type of HCM (asymmetric versus concentric) and echocardiographic fractional shortening were not different in the studied groups.

RESULTS

[table: see text]

CONCLUSIONS

1. Maximum QTc interlead QTc dispersion are increased in patients with HCM that show CVA on Holter monitoring; 2. Amiodarone prolongs QTc but reduces QTc dispersion, while beta-blockers and calcium antagonists do not significantly change neither the duration nor the dispersion of ventricular repolarization.