Objectives: This study was designed to establish the cause of electrocardiographic (ECG) pattern differences between genders.
Background: The male and female patterns of early ventricular repolarization in normal ECGs differ from each other. The male pattern displays a higher J-point amplitude and increased ST angle. The distribution of these patterns between genders has not been studied.
Methods: Normal ECGs of 529 males and 544 females, age 5 to 96 years, were subdivided into nine age groups in each gender. We designated the pattern as female if the J point was <0.1 mV in each of the leads V(1) to V(4), and as male if the J point was > or =0.1 mV and the ST angle > or =20 degrees in at least one of the V(1) to V(4) leads; the pattern was indeterminate if the J point was > or =0.1 mV and the ST angle was <20 degrees.
Results: Distribution of patterns was significantly different between genders (p < 0.001). In females, the patterns were distributed similarly from puberty to advanced age with about 80% prevalence of the female pattern. In males, the male pattern prevalence increased at puberty, reached 91% in the age group of 17 to 24 years and declined gradually with advancing age to 14% in the oldest males. The prevalence of indeterminate pattern was about 10% in both genders. Patterns were unchanged in 95% of 493 subjects who had ECGs recorded at separate times or at different heart rates.
Conclusions: Gender differences in early ventricular repolarization were caused by age-dependent changes in prevalence of the male pattern.