Title: Atrioventricular Node Reentrant Tachycardia as a Cause of Recurrent Syncope in a Patient With Non-obstructive Hypertrophic Cardiomyopathy
Abstract: A 60-year-old male patient was admitted to our hospital for recurrent syncope. On arrival at our hospital, the patient was totally oriented. Blood pressure was 180/104mmHg, with a heart rate of 100bpm. ECG showed high voltage of precordial leads and minor ST-segment depression in lateral leads. Echocardiography demonstrated preserved left ventricular (LV) systolic function and asymmetrical ventricular wall hypertrophy. LV outflow obstruction was undetectable. Cardiac MRI demonstrated late gadolinium enhancement in the hypertrophied anteroseptal wall. Together, the patient was diagnosed as non-obstructive hypertrophic cardiomyopathy (HCM). During the hospital stay, 24-h Holter monitoring was conducted, demonstrating no pauses and no ventricular tachy-arrhythmias. Both head-up-tilt test and head MRI showed no abnormal findings. On electrophysiological studies, ventricular tachycardia was not induced by extra-stimuli and basic drives from the right ventricle. However, atrioventricular node reentrant tachycardia (AVNRT) was induced by extra-stimuli of the right atrium, which resulted in sudden decrease of systolic blood pressure from 120mmHg to 50mmHg and presyncope. Subsequently, catheter ablation to the slow pathway was successfully performed, after which the patient have not suffered from syncope. HCM patients with one or more recent episodes of unexplained syncope meet indications for ICD (class IIa). Unnecessary ICD implantation in this patient was avoided by a prompt diagnosis of AVNRT, which is an uncommon cause of syncope in non-obstructive HCM.