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Objective: To evaluate the relation between QT variables and disproportion of left ventricular wall hypertrophy in patients with hypertrophic cardiomyopathy. Design: Retrospective analysis of the results of echocardiography and electrocardiography. Setting: University hospital (tertiary referral centre). Patients: 70 patients with hypertrophic cardiomyopathy were divided into four groups according to the distribution of left ventricular wall hypertrophy on cross sectional echocardiography: group A-hypertrophy confined to the interventricular septum; group B-hypertrophy confined to the interventricular septum and left ventricular anterior wall; group C-hypertrophy confined to the interventricular septum, left ventricular anterior wall, and lateral free wall; group D-hypertrophy involving all portions of the left ventricle. Main outcome measures: QT intervals and QT dispersion in precordial six lead ECGs. Results: There were no significant differences in the maximum left ventricular wall thickness among the four groups, and maximum and minimum QTc intervals also did not differ. QTc dispersion was increased significantly in groups A and B compared with groups C and D. Dispersions of the interval from the J point to the end of the T wave (JTc dispersions) in groups A and B were also increased significantly compared with groups C and D. By linear regression analysis, QTc and JTc dispersions correlated with the ratio of the interventricular septal thickness to left ventricular posterior wall thickness (p = 0.0152 and p = 0.0075, respectively). Conclusions: QT dispersion may be affected by not only electrical inhomogeneity but also by morphological inhomogeneity of the left ventricle in patients with hypertrophic cardiomyopathy. [ABSTRACT FROM AUTHOR]