B-PO05-031 AETIOLOGY OF ATRIOVENTRICULAR HEART BLOCK IN YOUNG AND MIDDLE AGED ADULTS FROM SOUTH AFRICA

Abstract

There is a paucity of data regarding the aetiology of atrioventricular (AV) heart block in young and middle-aged patients particularly from the from low and middle income countries. To determine the aetiology of AV heart block in patients ≤ 55 years who were treated with a transvenous pacemaker from a middle income country. We performed a retrospective review of all patients who received a transvenous pacemaker for newly diagnosed AV block from 1 January 2013 to 31 December 2020 at Groote Schuur Hospital, Cape Town, South Africa. The cohort of patients ≤ 55 years were the focus of this study. During the study period, 1101 consecutive patients received a permanent transvenous pacemaker for AV block. 136 patients (12.4%) were ≤55 years. The mean (standard deviation) age of the study patients was 41 (11) years and 48.5% were female. Third degree AV block was diagnosed in 73.5% and 2:1 AV block in 8.1%. The aetiology of heart block could be determined in 97 (71.3%) patients. 43 (31.6%) patients were post-surgical, predominantly for isolated mitral valve (MVR) replacement (27.9%) and isolated aortic valve (AVR) replacement (20.9%). 16 had developed complete heart block from an acute myocardial infarction; inferior myocardial infarction in 9/16 and anterior myocardial infarction in 7/16 patients. Congenital complete heart block was diagnosed in 15 (11%) cases. Cardiac Magnetic Resonance (CMR) imaging was performed in 26 patients: cardiac sarcoidosis was diagnosed in 7/26 patients, prior myocarditis in 3/26, left ventricular non-compaction in 3/26, interatrial cardiac tumour in 1 patient, cardiac amyloid in patient with multiple myeloma in 1 patient and hypertrophic cardiomyopathy in 1 patient. No pathology could be identified 10/26 patients who had CMR. The aetiology of AV block remained unknown in 39 patients (28.7%). Prior valve surgery is the leading cause of AV block treated with transvenous pacemaker in patients ≤ 55 years at our institution. Cardiac magnetic resonance imaging identifies disease processes that require further management in a significant proportion of cases.