CARDIOVASCULAR JOURNAL OF AFRICA • Volume 34, No 3, July/August 2023 AFRICA 151 determine the profile and outcomes of patients younger than 35 years of age implanted with ICDs in a South African referral centre. Methods This study was designed as a retrospective review of patients, aged 35 years or younger, implanted with ICDs at Groote Schuur Hospital from 1 January 1998 to 31 December 2020. Groote Schuur Hospital is a 900-bed tertiary- and quaternarycare centre located in the in the Western Cape province of South Africa and affiliated to the University of Cape Town. This study was approved by the University of Cape Town Human Research Ethics Committee, HREC ref no: 505/2019. Patients implanted with ICDs are followed up in our device clinic at six weeks post implantation with a clinical review, chest radiograph, electrocardiogram and device interrogation. The clinical review, ECG and device interrogation are then repeated every six months. Patients with cardiac resynchronisation therapy plus a defibrillator (CRT-D) perform a six-minute walk on each visit. Patients are advised to immediately come into hospital when they experience an ICD shock. Clinical notes, ICD device information and follow-up data were reviewed. A standardised data-collection form was used to collect baseline demographic data, information on clinical presentation and ICD follow-up data for a history of ICD shock therapies. Device-stored electrograms were reviewed to determine whether the delivered shock therapy was appropriate or inappropriate. Statistical analysis Normally distributed continuous variables are reported as means ± standard deviations (SD), and as medians and interquartile ranges (IQR) when skewed. Discrete data are presented as numbers and percentages. The chi-squared test and Student’s t-test were used to calculate differences between the primary- and the secondary-prevention groups, accordingly. The Kaplan– Meier and log rank tests were used to assess the cumulative survival differences between the primary-prevention versus secondary-prevention group, any ICD shock therapy versus no ICD shocks and appropriate ICD shocks versus no ICD shocks. A p-value < 0.05 represents a statistically significant difference. Statistical analyses were performed using SPSS Statistics for Macintosh version 24.0 (IBM, USA). Results A total of 260 patients were implanted with ICDs at Groote Schuur Hospital during the study period. After excluding seven patients with missing records and 215 patients older than 35 years of age, 38 patients were analysed (Fig. 1). The patient characteristics are presented in Table 1. The mean (SD) age at ICD implantation was 25.1 (7.6) years and 63.2% were male. At presentation, the ejection fraction on echocardiography was 42.8% (22.1%). A secondary-prevention ICD was implanted in 22/38 (57.9%) of the patient population and primary-prevention ICD in the remaining 16/38 (42.1%) (Table 2). Patients with secondaryprevention ICDs presented with VT [13/22 (59.1%)], VF [7/22 (31.8%)] and confirmation of cardiopulmonary resuscitation, but no recorded electrocardiograms in 2/22 (9.1%). A singlechamber ICD was implanted in 24/38 (63.2%), dual-chamber ICD in 8/38 (21.1%) and CRT-D in 6/38 (15.8%). An upgrade 01/01/1998 to 31/12/2020 260 ICD implantations 38 patients ≤ 35 years of age Excluded patients 7 missing records 215 patients ≥ 35 years of age Fig. 1. Study flow chart. Primary prevention Secondary prevention 5.3% 2.6% 2.6% 10.5% 13.2% 7.9% 5.3% 2.6% 2.6% 21.1% 21.1% 5.3% 30 25 20 15 10 5 0 Percentage Myocarditis Cardiac sarcoidosis Peripartum cardiomyopathy Past surgery for congenital heart defects Long QT No primary diagnosis Hypertrophic cardiomyopathy Arrhythmogenic right ventricular cardiomyopathy Dilated cardiomyopathy Fig. 2. Identified substrate for arrhythmia or possible SCD; patient number 38.
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