Apical hypertrophic cardiomyopathy is characterized by primary hypertrophy of the myocardium which is localized exclusively at the apex of the left ventricle. Previous studies have indicated that apical hypertrophic cardiomyopathy is characterized by a unique combination of cross-sectional echocardiographic and ECG findings ("giant" T wave inversion and high R wave voltage in the precordial leads). The aim of this study was to evaluate the possible relation between apical hypertrophy, quantitatively defined by cross-sectional echocardiography, and ECG findings in patients with apical hypertrophic cardiomyopathy. We studied 13 pts with apical hypertrophic cardiomyopathy, 10 men and 3 women (aged between 11 and 73 years, mean age 47). Apical hypertrophy was assessed quantitatively by determinating the muscle cross-sectional area in the apical region. From the end-diastolic apical 4 chamber view, endocardial and epicardial contours were digitized in order to obtain the muscle cross-sectional area of the left ventricle. The walls of the left ventricle were then divided into 3 regions (basal, mid-ventricular, apical). Final values of planimetered muscle areas are given as the average of the calculations obtained blindly and independently by 4 observers. The comparison between cross-sectional echocardiographic and electrocardiographic findings showed that patients with giant T wave inversion (T wave greater than 10 mm) and high R wave voltages (R greater than wave 25 mm) had a more severe degree of apical hypertrophy. However there was no complete agreement between cross-sectional echocardiographic and electrocardiographic findings. This study in fact demonstrates a wide variation in the degree of severity of apical hypertrophy among patients with apical hypertrophic cardiomyopathy.(ABSTRACT TRUNCATED AT 250 WORDS)