Abstract 12168: Signal-Averaged Electrocardiogram and Histologic Evaluation of the Myocardial Substrate in Right Ventricular Outflow Tract Arrhythmias
Introduction. The differential diagnosis between idiopathic and cardiomyopathy-related right ventricular outflow tract ventricular arrhythmias (RVOT-VAs) is crucial. Signal-averaged electrocardiogram (SAECG) abnormalities are frequent in cardiomyopathy-related RVOT-VAs, although their pathophysiologic basis and diagnostic value in this setting are undefined. We tested the association between SAECG and the myocardial substrate underlying RVOT-VAs.
Methods. 24 consecutive patients (age 50±13 years, 12 men) with RVOT-VAs (10 with frequent [>1000/24h] premature ventricular contractions [PVCs], 14 with ventricular tachycardia [VT]) underwent SAECG with 40 Hz filtering and electroanatomic mapping (EAM) with EAM-guided biopsy for characterization of the RVOT-VAs substrate. A filtered averaged QRS (fQRS) was obtained and analyzed for fQRS duration, low amplitude signal duration below 40 mV (LAS40) and root mean square voltage in last 40 ms of the QRS (RMS40). Standard definition of EAM scar was used.
Results. EAM-guided biopsy diagnosed arrhythmogenic right ventricular cardiomyopathy in 11 (46%), myocarditis in 8 (33%), and idiopathic RVOT-VAs in 5 (21%) patients. Patients with cardiomyopathy-related RVOT-VAs had ≥1 EAM scar (mean 2.1±0.9, all with RVOT scar). EAM of patients with idiopathic RVOT-VAs was normal. Patients with cardiomyopathy-related RVOT-VAs had significantly longer fQRS (109±19 ms vs. 85±7 ms, P=0.01) and LAS40 (46±19 ms vs. 23±9 ms, P=0.02), and lower RMS40 (19±12 μV vs. 31±6 μV, P=0.04). A significant correlation was found between the extension (cm2) of the RVOT scar and all three SAECG parameters (R=0.71, P<0.001 for the fQRSd; R=0.60, P=0.002 for the LAS40; and R=-0.54, P=0.007 for the RMS40). Using the established 2 of 3 criteria (i.e., late potentials) SAECG diagnosed cardiomyopathy-related RVOT-VAs with high positive (100%) but low negative (38%) predictive values, and missed 7/9 (78%) patients with RVOT scar <8 cm2.
Conclusion. In patients with RVOT-VAs, abnormal SAECG parameters reflect the presence of extensive cardiomyopathic involvement of the RVOT. A negative SAECG does not reliably rule out cardiomyopathy-related RVOT-VAs with small RVOT scars.
- © 2011 by American Heart Association, Inc.