Non-compaction cardiomyopathy and incessant supraventricular tachycardia: an unusual first presentation

A 36-year-old woman without previous history of cardiac disease was referred to our electrophysiology department for emergency catheter ablation of an incessant supraventricular tachycardia refractory to multiple antiarrhythmic drugs. The 12-lead electrocardiogram showed a fast and regular narrow QRS-complex tachycardia with short-RP interval and inverted P-waves in the inferior leads (Panel A) which proved to be an orthodromic atrioventricular reciprocating tachycardia using an anteroseptal accessory pathway for retrograde conduction. Degeneration into atrial fibrillation unmasked intermittent anterograde conduction over the same pathway (Panel B). Cardiovascular magnetic resonance (CMR) imaging performed after successful ablation revealed a normal-sized left ventricle with mildly reduced systolic function. However, prominent intraventricular trabeculations separated by deep intertrabecular recessus were detected which fulfilled the diagnostic criteria of a left-ventricular non-compaction (LVNC) cardiomyopathy (ratio of non-compacted and compacted myocardial layer >2.3, Panel C). Most notably, a prominent trabecula mimicking an accessory left-ventricular chamber together with extreme thinning of the basal septum were present but on late gadolinium enhancement imaging intramyocardial fibrosis or the presence of left ventricular thrombus could be excluded (Panel D, see Supplementary material online, Video S 1).