Clinical, electrocardiographic, and histologic correlations in children with dilated cardiomyopathy

Objective. To determine whether presenting electrocardiography is related to histologic findings and clinical outcomes in children with dilated cardiomyopathy.BackgroundLymphocytic myocarditis is an important cause of childhood dilated cardiomyopathy, the outcome of which is unclear. The results of non-invasive investigations are often used to infer the presence or absence of lymphocytic myocarditis. Methods. Thirty-four children, presenting acutely with dilated cardiomyopathy, underwent both early electrocardiography and endomyocardial biopsy. The parameters examined included heart rate, PR, QRS, and corrected QT intervals, R-wave voltages in Leads V₁ and V₆, S-wave voltages in Leads V₁ and V₆, and sum of SV₁ and RV₆. We expressed measurements as Z scores, based on published normal values for age and gender. Results. A total of 15 patients had lymphocytic myocarditis on endomyocardial biopsy (Group I), and 19 had non-specific histologic findings (Group II). We did not distinguish the 2 groups by age, time to endomyocardial biopsy, or duration of follow-up. Group I patients had significantly smaller R-wave Z scores in Leads V₁ and V₆, and combined S in V₁ and R in V₆ Z scores (p < 0.02 for each). The positive and negative predictive values of an R-wave amplitude in V₆ < 5th percentile were 75% and 65%, respectively, for the diagnosis of lymphocytic myocarditis. An R-wave amplitude in V₆ > 95th percentile had a positive and negative predictive value of 80% and 63%, respectively, for the diagnosis of idiopathic dilated cardiomyopathy. Survival and freedom from late cardiac dysfunction were more common among Group I patients compared with Group II (p ≤ 0.02 for both). Conclusion. Myocardial histology cannot reliably be inferred from the presenting electrocardiogram. Survival and outcome for children with lymphocytic myocarditis is better than for those with non-specific histology.