Abstract 11981: ECG-Derived Vectorcardiography Identifies Disease and Genotype Status in Hypertrophic Cardiomyopathy

Abstract

Introduction: Vectorcardiography (VCG) has clinical prognostic and diagnostic value in various disease states. Hypertrophic cardiomyopathy is a disease state which can lead to sudden cardiac death, where genotype status has been shown to predict worse outcomes.. Hypothesis: We set out to determine the utility of vectorcardiographic parameters in one of the largest genotyped cohorts of patients with hypertrophic cardiomyopathy (HCM) and to determine whether they can identify genotype status. Methods: Between 1997 and 2007, research based genetic testing was performed on 1053 patients with HCM (60% males; mean age at diagnosis 44.4 years); yield of genetic testing was 34%. Of these, 967 had ECG’s appropriate for computerized derivation of VCG parameters including the spatial mean and peaks QRS-T angles, spatial ventricular gradient and the spatial QRS, QT, and Tpeak-Tend (TpTe) intervals. Results were compared against those from a group of healthy control subjects (N=418).Subsequent genotype positive versus negative comparisons were performed using paired student T-tests or Mann-Whitney U-tests as appropriate. Results: Spatial peaks and spatial mean QRS-T angles were significantly higher in HCM patients (129.3±26.4 and 121.8±38.6 degrees, respectively) than in controls (25.0±15.0 and 43.0±-21.0 degrees, respectively, p<0.001). Sensitivities for HCM, based on cutoff values of 2 standard deviations above the mean values reported for control patients, were 84.5% and 81.5% for spatial peaks and spatial mean QRS-T angles, respectively. VCG predicted genotype status as genotype positive patients had significantly higher spatial peaks (132.4±-29.2 vs. 127.9±24.8 degrees; p = 0.02) and spatial mean (129.7±33.8 vs. 117.6±40.3 degrees; p<0.001) QRS-T angles, spatial TpTe (118.0±40.8 vs. 107.9±48.7 ms; p<0.001) as well as significantly lower spatial ventricular gradients (0.059±0.044 vs. 0.067±0.04; p<0.001). Conclusions: Patients with HCM can be distinguished from normal subjects through the study of the spatial QRS-T angle. Whether incorporation of spatial peaks QRS-T angle to pre-existing genetic test prediction tools will further improve prediction of genotype status remains to be determined.