Objective: Isolated ventricular noncompaction is a rare primary genetic cardiomyopathy characterized by persistent embryonic myocardial morphology without any other cardiac anomalies. Arrhythmias are frequently present, including both tachyarrhythmia and conduction disturbance. Our study aimed to describe the electrocardiographic findings and to correlate them with the clinical presentation and cardiac magnetic resonance imaging findings. Methods: We retrospectively reviewed 24 patients diagnosed with isolated ventricular noncompaction (IVNC) by cardiac magnetic resonance imaging. Correlations were investigated between arrhythmias and the site of ventricular noncompaction, number of noncompacted segments, presence of fibrosis, and left ventricular dysfunction. Results: The mean age was 42.7 +/- 13.1 years. Patients were first presented with heart failure in 41.7% and arrhythmia in 45.8%. Electrocardiogram was abnormal in 91.6% of patients; the most common anomaly was left bundle branch block (LBBB) (41.7%), followed by supraventricular arrhythmias (29.1%), repolarization abnormalities (29.1%), and ventricular tachycardia (20.8%). A normal left ventricular systolic function was frequently observed in patients who first presented with rhythm disorders than heart failure (p=0.008). There was also a delayed diagnosis of IVNC when presented with arrhythmia versus heart failure (p=0.02). We found no correlation between arrhythmias and the noncompaction site or fibrosis, except for LBBB, which was associated to left ventricle lateral wall involvement (p=0.028). No correlation between systolic dysfunction and the number of noncompacted segments, fibrosis, or arrhythmia was demonstrated. Conclusion: While electrocardiographic abnormalities are frequent in isolated ventricular noncompaction, no specific patterns were identified. More large studies are needed for stratification of arrhythmic risk of this highly arrhythmogenic substrate.
