BACKGROUND: Both 2-D echocardiography and signal-averaged ECG (SAECG) are important diagnostic modalities of arrhythmogenic right ventricular cardiomyopathy (ARVC). However, the correlation between these two studies was not known well. OBJECTIVES: The purpose of this study was to compare SAECG variables with echocardiographic abnormalities, especially focused on right ventricular outflow tract (RVOT) diameter, because previous study showed that RVOT diameter have higer sensitivity and specificity than other quantitative measurements of right ventricle. METHODS: We studied 18 patients of ARVC who met Task force criteria of ARVC. Two-dimensional echocardiogram was performed in all patients. RV regional function, RVOT diameter, and the presence of morphologic abnormalities were assessed. SAECG was performed using a MAC 15 system with high gain amplification and bi-directional Butterworth filters (40-250 Hz). One patient was excluded from further analysis as we could not obtain a noise level <0.3 關V. Finally 17 patients were included in this study. RESULTS: The RV morphologic abnormalities were present in 12 patients (trabecular derangement in 50%, aneurysmal change or sacculations in 39%, and hyper-reflective moderator band in 11%). Mean RVOT diameter was 32짹3mm. RVOT diameter >30mm occurred in 72% of patients. The SAECG was abnormal in 6 patients. There was a consistent correlation between all SAECG variables (fQRS, LAS40, and RMS40) and the RVOT diameter (p<0.05). There was no statistical correlation between morphologic abnormalities and SAECG variables. CONCLUSIONS: The majority of patients with ARVC have abnormal 2-D echocardiographic findings. The RVOT diameter was correlated with the SAECG variables.