Correlation of signal averaged electrocardiography findings with fibrosis on cardiac magnetic resonance imaging

Background Signal averaged electrocardiogram (SAECG) is a non invasive test to record delayed depolarization of myocardium with slow conduction that can potentially be the substrate for monomorphic ventricular tachycardia in high risk patients. Cardiac magnetic resonance imaging (cMRI) techniques for fibrosis imaging using late gadolinium enhancement (LGE) and T1 mapping remain the gold standard for characterization of myocardial tissue and triaging patients for risk of ventricular arrhythmias. However, cMRI remains unavailable in some areas, is time consuming, expensive and impossible for some patients to obtain due to claustrophobia, renal impairment or implanted hardware. To date, data is lacking with regards to correlation of findings between these two modalities. Purpose To investigate whether late potentials identified by SAECG correlate with the presence of fibrosis seen with cMRI. If correlation is established, SAECG could potentially be used as a non-invasive, cheaper, more convenient and readily available tool for risk stratification in patients at high risk for ventricular arrhythmias. Methods SAECGs were obtained in 25 consecutive patients undergoing cMRI. Patients with wide QRS (>120 ms) on ECG were excluded. Positive SAECG was defined as at least 1/3 abnormal criteria. Standard criteria were used. Results of the 2 modalities were compared. Sensitivity and specificity of SAECG for diagnosing fibrosis on cMRI were calculated. Results The mean age of the patients was 50.3±5.8 years and the mean ejection fraction was 48.9±5.8% as determined by cMRI. Forty-eight percent of the patients had fibrosis on cMRI by either LGE, T1 mapping or both. The sensitivity and specificity of SAECG were 75% and 100%, respectively. Seven patients had history of ventricular tachycardia and 6 patients had dilated cardiomyopathy. Conclusion SAECG is extremely specific in identifying patients with myocardial fibrosis on cMRI. A positive test may confer a lesser indication to pursue cMRI solely for purposes of risk stratification, and may correlate with risk of ventricular arrhythmia. FUNDunding Acknowledgement Type of funding sources: None.