Electrocardiograms continue to be part of screening programs for athletes and familial hypertrophic cardiomyopathy (HC). Whether electrocardiographic (ECG) findings of left ventricular (LV) hypertrophy can distinguish between healthy populations and those with HC remains unclear. We sought to (1) analyze the relation between ECG voltage and LV mass in patients with HC and (2) evaluate ECG characteristics of patients with phenotypical HC. Retrospective cohort of patients with HC aged 13 to 18 years. Relation between ECG voltages (RV6, SV1, and RV6 + SV1) and echocardiogram measurements of LV mass was investigated using smoothing splines to display relations and compared with those in a prospectively obtained population of adolescents. Frequency of abnormal LV voltages and nonvoltage ECG changes (Q waves, T-wave changes, and ST changes) were analyzed for association with HC. Fifty-three patients with HC (72% men) were age and gender matched to 104 control patients. Smoothing splines demonstrated that parabolic rather than linear relations existed between LV mass and SV1, RV6, and RV6 + SV1 in patients with HC and not the control cohort. LV hypertrophy by ECG voltage criteria was present in 34% of patients with HC and associated with poor sensitivity (29%). In patients with HC, 56% demonstrated nonvoltage ECG abnormalities and were associated with improved sensitivity (68%) and high specificity (94%). In conclusion, there is a parabolic relation between LV voltages and LV mass in adolescents with HC that may lead to "pseudonormalization." Voltage abnormalities were associated with poor sensitivity, whereas nonvoltage criteria were associated with improved sensitivity with high specificity.
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