Incremental value of implantable loop recorders in arrhythmia detection and management in cardiomyopathies: Prospective study

Introdução e Objetivos: As recomendações para a implantação do cardioversor-desfibrilhador implantável (CDI) para prevenção da morte súbita cardíaca (MSC) na cardiomiopatia hipertrófica (CMH) evoluíram ao longo do tempo, tendo o realce tardio (RT) emergido como um marcador de risco. Este estudo teve como objetivo avaliar a evolução da precisão e do desempenho discriminativo das guidelines internacionais para as recomendações de implantação de CDI e determinar se o RT pode melhorar esta estratificação de risco. Métodos: Foi realizado um estudo observacional retrospetivo e multicêntrico de doentes com CMH submetidos a ressonância magnética cardíaca (RMC) para diagnóstico ou avaliação de risco. A elegibilidade para CDI foi determinada de acordo com as orientações da ESC (2014, 2022, 2023) e da ACC (2011, 2020, 2024). O outcome primário foi um composto de MSC, descarga apropriada do CDI ou taquicardia ventricular (TV) sustentada. Resultados: Foram incluídos no estudo um total de 531 doentes (idade mediana de 49 anos; 57% do sexo masculino). Durante um seguimento mediano de 49 meses, ocorreram 28 eventos (15 MSCs, 6 descargas apropriadas de CDI, 7 TVs sustentadas). Com o tempo, as guidelines europeias e americanas demonstraram uma melhoria na sensibilidade, no valor preditivo positivo e na capacidade discriminativa, mantendo um elevado valor preditivo negativo. A concordância entre as mais recentes guidelines da ESC e da ACC foi moderada (κ ≈ 0,6, p < 0,001). Foi detetado realce tardio (RT) em 80% dos doentes, e a percentagem de RT foi um preditor independente de eventos arrítmicos (aHR 1,09 por aumento de 1%; p < 0,001). Uma carga ≥8% foi o melhor preditor de eventos, enquanto a ausência de RT identificou doentes sem desfechos arrítmicos. Conclusões: A carga de RT refina a estratificação do risco de morte súbita cardíaca, sendo que a ausência completa de RT identifica um subgrupo de risco muito baixo. Os limiares de RT devem ser individualizados, integrando os dados de imagem, os fatores clínicos e o contexto do doente. Introduction and objectives: Implantable loop recorders (ILR) are increasingly being used for the detection of infrequent arrhythmias in patients with cardiomyopathies, especially in the presence of risk markers. The role of these devices in improving the detection of significant arrhythmias requiring a change in clinical management remains to be determined. Our purpose was to evaluate the diagnostic yield, types of arrhythmias, and subsequent management in cardiomyopathy patients receiving an ILR. Methods: Prospective single-center study in cardiomyopathy patients considered at borderline risk for ventricular arrhythmias, who had received an ILR. The primary endpoint was a meaningful arrhythmic event detection leading to a change in clinical management. Results: A total of 45 patients were included, 51% were male, median age was 62 (48–71) years. The underlying disease was hypertrophic cardiomyopathy (HCM) in 31 patients (69%), dilated and non-dilated left ventricle cardiomyopathy (DCM/NDLVC) in 12 patients (26%) and transthyretin amyloid cardiomyopathy (ATTR-CM) in two patients (4%). The most frequent risk markers were brief run of non-sustained ventricular tachycardia in 42%, unexplained syncope/presyncope in 36%, family history of premature sudden cardiac death (SCD) in a first-degree relative in 36%, and palpitations suspicious of arrhythmic origin in 18% of patients. In the HCM cohort, median HCM Risk-SCD score was 3.07 (2.68 – 3.76)%, with 19% of patients having an estimated 5-year risk of SCD ≥4%. Mean maximum wall thickness was 20±4mm, mean left atrial diameter was 43±7mm, 23% of patients had obstructive HCM, late gadolinium enhancement (LGE) was present in 74% - with 52% of patients presenting extensive LGE-, and left ventricle apical aneurysm in 3%. A sarcomeric pathogenic variant was identified in 26%. Among the DCM/NDLVC patients, 58% had left ventricular ejection <50%, 25% carried pathogenic/likely pathogenic variants on genetic testing and 25% exhibited an extensive ring-like scar pattern on cardiac magnetic resonance (CMR). During a mean follow-up of 19±13 months, 44% of patients had, at least, one ILR-guided diagnosis. De novo atrial fibrillation was diagnosed in 24% of patients and was the main detected event. Due to ILR-guided diagnosis, 20% (9 patients) received an implantable cardioverter-defibrillator (ICD), one of which with subsequent appropriate ICD therapies. Conclusion: This study provides insight into the possible role of ILR in this population, not only for the diagnosis of ventricular arrhythmias, but also for detection of atrial fibrillation, which can lead to different clinical management.