Abstract 1892: Electrocardiographic Manifestations of Sarcomere Mutations in Hypertrophic Cardiomyopathy: Incremental Value in the Prediction of Genetic Risk
Background: The diagnosis of hypertrophic cardiomyopathy (HCM) typically rests on identifying unexplained left ventricular hypertrophy (LVH) by cardiac imaging. Genetic testing can identify carriers of pathogenic sarcomere mutations (G+) prior to the development of LVH (G+/LVH−, preclinical HCM). Previous echocardiographic studies utilizing tissue Doppler imaging (TDI) have demonstrated impaired myocardial relaxation in this population; however electrocardiographic (ECG) findings, especially in relation to diastolic function, have not been well described in preclinical HCM. In the current study we describe the ECG features of sarcomeric HCM in the absence and presence of left ventricular hypertrophy (LVH).
Methods: A genotyped cohort (n=217) consisting of 59 overt HCM (G+/LVH+), 77 preclinical HCM (G+/LVH−) and 81 normal control (G−/LVH−) subjects were studied with echocardiography and ECG. A subset also underwent cardiac magnetic resonance imaging (CMR). Comprehensive ECG analysis was performed blinded to genotype, clinical status and echocardiographic features.
Results: ECG changes were common in overt HCM (85%), although the minority (< 25%) had LVH by commonly used voltage criteria. ECG findings in preclinical HCM did not differ significantly from controls with the exception of an increased prevalence of abnormal Q waves (Qw) (18% versus 2%, P= 0.001). Qw remained predictive of carrying a gene mutation (OR 4.98, p= 0.047) in LVH negative subjects after controlling for age and TDI. In 31 preclinical HCM subjects who underwent CMR, none had late gadolinium enhancement to suggest myocardial scar as the anatomic substrate for Qw.
Conclusions: Conventional ECG voltage criteria for LVH are insensitive for identifying overt HCM. The presence of Qw had 18% sensitivity but 98% specificity for discriminating preclinical HCM from normal controls, providing incremental information to TDI. Assessing Qw and impaired relaxation may assist in identifying family members at genetic risk for developing HCM, particularly in situations where genotype cannot be determined.