Abstract 18098: Prolonged Filtered QRS Duration on Signal Averaged Electrocardiogram is Associated With Structural Remodeling in Hypertrophic Cardiomyopathy

Background: Hypertrophic cardiomyopathy (HCM) is characterized by myocyte hypertrophy, electrical remodeling and fibrosis that lead to inhomogeneous ventricular depolarization and arrhythmias. Signal averaged ECG (SAECG) is useful for non-invasive risk stratification in ischemic cardiomyopathy. However, the association between SAECG and structural remodeling in HCM has not been investigated.

Methods: We retrospectively studied 594 HCM patients from the Johns Hopkins HCM Registry, who underwent echocardiography and cardiac magnetic resonance (CMR) imaging within 12 months of SAECG or 12-lead ECG. Seventy-three patients underwent SAECG and were divided into 2 groups (Normal-SAECG, Abnormal-SAECG) based on filtered QRS duration and/or presence of late potentials .

Results: Abnormal SAECG was seen in 50% of HCM patients (37/73). Of the 37 HCM patients with abnormal SAECG, 29 patients only had prolonged filtered QRS duration ( fQRS> 114ms ), and 8 patients had prolonged fQRS duration as well as late potentials ( LAS40 >38ms; RMS40 <20μV). Mean fQRS and LAS40 were significantly higher in the Abnormal-SAECG group ( fQRS : 125.7 vs 107msec, p<0.0001; LAS40 : 31.2 vs 22.9msec; p=0.002; RMS40 : 40 vs 54μV; p=0.07). HCM patients with abnormal SAECG also had 1) larger left atrial size (p=0.03), lower global LV peak systolic strain (p=0.04), systolic strain rate (p=0.008), early diastolic strain rate (p=0.01) by ECHO; 2) greater LV mass index (p=0.004) 3) Higher prevalence and amount of late gadolinium enhancement (LGE) reflecting LV-scar (p=0.045 and 0.01) by CMR; 4) higher prevalence of repolarization abnormalities on 12-lead ECG (p=0.02). Adverse outcomes (sustained-VT/VF, heart failure, death) were similar in the 2 groups. Filtered QRS duration (SAECG) was positively correlated with LV mass index (r=0.43, p=0.0002), QRS duration on 12-lead ECG (r=0.67, p=0.000), and negatively correlated with global LV early diastolic strain rate (r= -0.34, p=0.009) in our HCM cohort.

Conclusion: In HCM, prolonged filtered QRS on SAECG reflects a greater degree of structural remodeling characterized by more LV hypertrophy, larger LA size, worse cardiac mechanics, and higher prevalence and amount of fibrosis.