Implantable defibrillators in primary prevention of genetic arrhythmias. A shocking choice?

Abstract

Many previously unexplained life-threatening ventricular arrhythmias and sudden cardiac deaths (SCDs) in young individuals are now recognized to be genetic in nature and are ascribed to a growing number of distinct inherited arrhythmogenic diseases. These include hypertrophic cardiomyopathy, arrhythmogenic cardiomyopathy, long QT syndrome, Brugada syndrome, catecholaminergic polymorphic ventricular tachycardia (VT), and short QT syndrome. Because of their lower frequency compared to coronary disease, risk factors for SCD are not very precise in patients with inherited arrhythmogenic diseases. As randomized studies are generally non-feasible and may even be ethically unjustifiable, especially in the presence of effective therapies, the risk assessment of malignant arrhythmic events such as SCD, cardiac arrest due to ventricular fibrillation (VF), appropriate implantable cardioverter defibrillator (ICD) interventions, or ICD therapy on fast VT/VF to guide ICD implantation is based on observational data and expert consensus. In this document, we review risk factors for SCD and indications for ICD implantation and additional therapies. What emerges is that, allowing for some important differences between cardiomyopathies and channelopathies, there is a growing and disquieting trend to create, and then use, semi-automated systems (risk scores, risk calculators, and, to some extent, even guidelines) which then dictate therapeutic choices. Their common denominator is a tendency to favour ICD implantation, sometime with reason, sometime without it. This contrasts with the time-honoured approach of selecting, among the available therapies, the best option (ICDs included) based on the clinical judgement for the specific patient and after having assessed the protection provided by optimal medical treatment.

State‐of‐the‐art document on optimal contemporary management of cardiomyopathies

“…221,222 Risk assessment models have been proposed for predicting the risk of life-threatening ventricular arrhythmias (including SCD), 223,224 however their practical use requires further validation. 225 Recently, a risk prediction model to estimates the 5-year risk of incident ventricular arrhythmias in ARVC has been developed (ARVCrisk. com) and validated.…”

“…RV fractional area change <23%), male sex, T‐wave inversion, QRS dispersion, non‐sustained VT and LV dysfunction have been associated with an increased risk of life‐threatening ventricular arrhythmias and SCD 221,222 . Risk assessment models have been proposed for predicting the risk of life‐threatening ventricular arrhythmias (including SCD), 223,224 however their practical use requires further validation 225 . Recently, a risk prediction model to estimates the 5‐year risk of incident ventricular arrhythmias in ARVC has been developed (http://arvcrisk.com) and validated 224,226 .…”

Scarring/arrhythmogenic cardiomyopathy

“…Before these calculators can be recommended for clinical use, rigorous validation studies are needed to assess their superiority in the prediction of SCD (rather than appropriate ICD discharges) in comparison with the traditional ‘single risk factor’ approach. 20 …”

“…In these patients, the decision to implant an ICD should be made on individual basis, by assessing the overall clinical profile, the age, the strength of the risk factor(s) identified, the level of SCD risk that is acceptable to the patient, and, most important, the potential high risk of serious complications over time. 20 Implantation of an ICD is not generally indicated in asymptomatic patients with no risk factors and healthy mutation carriers who have a low risk of malignant VAs. The performance of the 2015 TF consensus algorithm to guide ICD implantation in patients with S/ACM was validated by clinical studies which demonstrated that the algorithm accurately differentiated survival from any sustained VT or VF among the different ICD class indications.…”

“…Accordingly, in the absence of indication to ventricular pacing all efforts should be made to implant a life-saving device which reduces the risk of electrode and device-related side-effects, including intravascular lead failure or infection requiring surgical intervention, which significantly impact the quality of life of young patients and may increase morbidity and mortality because of their many decades of life expectancy. 20 For patients who developed heart failure, standard pharmacological treatment with angiotensin-converting-enzyme inhibitors, angiotensin II receptor blockers, beta-blockers, aldosterone antagonists and diuretics is indicated. The use of sacubitril/valsartan and SGLT2 inhibitors to improve cardiovascular outcomes, including hospitalization and death for heart failure require validation in patients with S/ACM.…”