CARDIOVASCULAR JOURNAL OF AFRICA • Volume 34, No 3, July/August 2023 154 AFRICA tachycardia (CPVT) and long-QT syndrome, which accounted for six and 4%, respectively.24 This is important, as these findings have implications on family screening and management.2,25 For example, evaluation of families of SADS victims identifies inheritable disease in 40 to 50% of families.26,27 Although access to advanced cardiac imaging, such as cardiac magnetic resonance imaging, in addition to echocardiography is available in our centre and therefore the diagnosis of structural overt arrhythmogenic cardiomyopathies such as hypertrophic cardiomyopathies, arrhythmogenic right ventricular cardiomyopathy and so forth is not curtailed, we do not perform genetic testing or provocation testing to unmask possible concealed channelopathies. Furthermore, we do not have the processes and protocols of assessing non-surviving SCD victims and their families. Therefore, this presents a major limitation in our hospital and region in assessing and managing survivors of SCD, non-surviving victims and their families. Real-world data indicate that the one- and five-year incidence of appropriate ICD shock is eight and 23% respectively.28 This therapy is often directed to monomorphic VT, polymorphic VT/ VF, or a combination of the two.28 Appropriate ICD shocks are a marker of severe cardiovascular disease and haemodynamic progression and are associated with increased mortality rates. For example, recipients of appropriate ICD shocks in the MADIT-II trial had a three-fold increase in hazard ratio for mortality after an appropriate ICD shock.29 Furthermore, in the SCD-HeFT trial, patients who suffered appropriate ICD shocks had a five-fold increase in mortality rate. Additional appropriate shocks resulted in an eight-fold increase in the risk of death.30 A meta-analysis assessing the association of appropriate ICD shock and mortality, involving 10 studies, found a strong association between appropriate ICD shocks and mortality; the hazard ratio for cardiac death was 2.95 (95% CI: 2.12–4.11; p < 0.001).31 In our study, 16/38 (42%) of the overall patient population, 12/22 (54%) in the secondary-prevention patient group and 4/16 (25%) in the primary-prevention group received appropriate ICD shocks. Furthermore, there was a trend towards increased mortality rates in patients who received appropriate ICD shocks (log rank p = 0.06). Considering this finding on the backdrop of larger studies, appropriate shocks portend worse outcomes and these data suggest that patients receiving appropriate ICD shocks should be followed up closely and carefully to optimise appropriate medical therapies. Implantation of ICDs in young patients as part of primary or secondary prevention has become a common practice with global trends on an upwards trajectory.32 Young recipients of ICDs are often confronted with psychological stress from inappropriate ICD shocks, a lifetime of generator changes and prohibition in sport participation and/or intensive exercise.2,25,33,34 In landmark ICD trials, the rates of inappropriate ICD shocks ranged between 11 and 20%.35 However, the rates of inappropriate ICD shocks in young adults and children vary between 25 and 45%.34 In the current study, the overall rate of inappropriate ICD shocks was 18.4% (7/38). This was higher in the secondary-prevention (6/22) than the primary-prevention group (1/16) (27.3 vs 6.3%, p = 0.10). Similarly to previous reports, supraventricular tachycardia (SVT), including atrial fibrillation and sinus tachycardia were the common causes of inappropriate shocks in this young cohort.35 This is particularly important as both sinus tachycardia and SVT tend to have higher rates in young patients, predisposing them to device misdiagnoses as a ventricular arrhythmia.37 Clinical trials studying ICDalgorithms to reduce inappropriate shocks either included patients implanted with dual-chamber ICDs or CRT-D or excluded patients with channelopathies or previous surgery for congenital heart diseases.38-41 Therefore, the strategies we use to minimise ICD shocks in this patient population are extrapolated from studies mainly enrolling adult patients with ischaemic heart disease. Our study did not detect any mortality difference between patients receiving inappropriate ICD shocks and those who did not. Although the association between inappropriate shock and mortality has been contradictory, these are associated with important psychological stress, anxiety, depression and physical pain.33,34 These incur significant costs to health systems by resulting in early battery depletion and the need for box change and frequent hospitalisations.37 Our study has several limitations. This was a small, singlecentre study, with a selection bias of survivors of SCD (secondary-prevention group) and our assessment of SCD was NO ICD shocks Appropriate ICD shocks No ICD shocks-censored Appropriate ICD shockscensored Months since ICD implantation Cumulative survival 0 25 50 75 100 125 100 80 60 40 20 0 Log rank p = 0.06 No inappropriate ICD shocks Inappropriate ICD shocks No appropriate shockscensored Inappropriate shockscensored Months since ICD implantation Cumulative survival 0 20 40 60 85 100 120 140 100 80 60 40 20 0 Log rank p = 0.26 Fig. 5. A: Kaplan–Meier curves depicting the cumulative survival difference between patients who received appropriate ICD shock therapies and those who did not get appropriate ICD shocks. B: Kaplan–Meier curves depicting the cumulative survival difference between patients who received inappropriate ICD shock therapies and those who did not get inappropriate ICD shocks. A B
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