Relation of electrocardiographic abnormalities to evolving left ventricular hypertrophy in hypertrophic cardiomyopathy during childhood.

Patients with hypertrophic cardiomyopathy (HC) often show substantial increases in left ventricular (LV) wall thickness or even de novo development of LV hypertrophy during childhood. To determine the utility of the electrocardiogram in reflecting such changes in LV mass, serial 12-lead electrocardiograms and 2-dimensional echocardiograms were analyzed in 38 children with HC. The period of evaluation ranged from 3 to 8 years (mean 5.5). Between the initial and most recent clinical evaluations, precordial and standard lead voltages did not change significantly in the study patients, including those showing evolution of LV hypertrophy by 2-dimensional echocardiography; furthermore, only 9 of the 38 patients (23%) showed any substantial change in the overall electrocardiographic pattern. However, the magnitude of electrocardiographic voltages at initial evaluation (age 11 +/- 4 years) showed a significant correlation with the extent of LV hypertrophy at the most recent evaluation as assessed by echocardiography (at age 16 +/- 4 years) (r = 0.65, p less than 0.001). Of note, each of the 7 patients who developed LV hypertrophy during the period of observation had distinct electrocardiographic abnormalities at the initial evaluation that preceded the appearance of LV hypertrophy on the echocardiogram. In conclusion, in children with HC and evolving LV hypertrophy, the electrocardiogram showed little change during the period of observation. However, electrocardiographic abnormalities may be the initial manifestation of HC, appearing even before LV hypertrophy is detectable by echocardiography. Hence, in patients with HC the electrocardiogram may provide advance evidence of morphologic changes that will subsequently occur and may describe the magnitude of LV hypertrophy ultimately achieved an average of 5 years later.(ABSTRACT TRUNCATED AT 250 WORDS)