Patients (pts) with idiopathic hypertrophic cardiomyopathy (HCM) are thought to be at increased risk of sudden cardiac death. Recently, QT dispersion has been suggested to reflect dispersion in cardiac repolarisation (DCR) which is responsible for occurrence of malignant ventricular arrhythmias. The present study was performed to assess extent of DCR in patients with HCM. In addition, DCR was assessed in the group of patients with hypertensive left ventricular hypertrophy (LVH). Study group consisted of 34 pts: 15 consecutive pts without cardiac diseases and hypertension (control group), 11 pts with LVH and 8 pts with HCM. To assess DCR in each patient in drug free condition duration of QT interval was measured in 12 leads. Following parametres were calculated: QT dispersion as a difference between maximal and minimal QT interval (QT diff.), standard deviation of QT intervals length (QTSD), QTc dispersion as a difference between maximal and minimal QTc and QT interval ratio (QT dispersion/cycle length x 100%). Only patients with sinus rhythm and absence of bundle branch block were included to study. All measurements were performed by three investigators in a blind mode. QTdiff was significantly greater in the LVH group when compared to control (58+/-21ms vs 32+/-2.3ms, p<0.01) and in the HCM group when compared with the LVH group (77+/-26ms vs 58+/-21ms, p<0.01). Similar relations were observed when QTSD was analyzed: (21+/-8ms vs 12+/-7ms, p<0.03) and (27+/-8ms vs 21+/-8ms, p<0,05) respectively. The QT interval ratio and QTc dispersion were greater in the LVH group when compared to control (7+/-3% and 65+/-23 vs 4+/-3% and 36+/-28 respectively, p<0.01) and greater in the HCM group than in LVH group: 8+/-3% vs 7+/-3%, p<0.05 and 77+/-26 vs 65+/-23, p=0.07, respectivelly. Thus hypertrophy of the left ventricle leads to an increased dispersion of repolarisation. More pronounced dispersion of repolarisation in HCM compared to LVH may reflect structural abnormalities due to underlying disease, may indicate additional risk of ventricular tachyarrhythmias in patients with HCM.
