Incremental value of the signal-averaged ECG for diagnosing arrhythmogenic cardiomyopathy

BACKGROUND Arrhythmogenic right ventricular cardiomyopa-thy (ARVC) is currently diagnosed using a combination of clin-ical features, imaging, electrocardiography, and genetic investigations. An abnormal signal-averaged electrocardiogram (SAECG) is defined as a minor diagnostic criterion by the 2010 Task Force Criteria, but doubts remain about the value of this investigation. OBJECTIVE We evaluated the utility of the SAECG in diagnosing ARVC using the Canadian Arrhythmogenic Right Ventricular Cardio-myopathy Registry, a population representative registry of pro-bands with ARVC and relatives, less influenced by referral bias.METHODS Probands with ARVC and family members from the Cana-dian Arrhythmogenic Right Ventricular Cardiomyopathy Registry un-derwent phenotype review. SAECG parameters were compared individually and in combination between those with varying degrees of ARVC severity and healthy controls (family members of probands with ARVC and unexplained sudden death, free of evidence of car-diac disease).RESULTS A total of 196 patients with ARVC and 205 controls were included (mean age 44 & PLUSMN; 15 years; 186 of 401 men [46%]). SAECG abnormalities were seen in 83 of 205 controls (40%), 33 of 68 pa-tients with ARVC and mild disease (51%), and 31 of 42 with severe disease (74%). The SAECG associated strongly with imaging abnor-malities (major: odds ratio 3.0, 95% confidence interval 1.3-6.9; minor: odds ratio 3.5, 95% confidence interval 0.7-16.5) but not with other aspects of phenotype. Patients carrying pathogenic var-iants but with minimal phenotype had similar SAECGs to healthy controls (filtered QRS duration 111.2 & PLUSMN; 11.2 ms vs 111 & PLUSMN; 7.6 ms, P = .93; duration of low amplitude signals < 40 mV 32.3 & PLUSMN; 8.9 ms vs 34.2 & PLUSMN; 7.2 ms, P = .32; root mean square of the terminal 40 ms of the filtered QRS complex 43.1 & PLUSMN; 25.2 ms vs 38.2 & PLUSMN; 20.2 ms, P = .38). CONCLUSION The SAECG appears to be a surrogate marker for structural abnormalities seen on imaging in those with ARVC. Great caution is required in interpreting SAECG findings in those without other corroborating evidence of an ARVC phenotype.