The role of cardiac magnetic resonance in cardiac arrest without initial underlying cause

The primary cause of sudden cardiac death is ischemic heart disease, but often we evaluate patients where this is excluded. Initial evaluation with echocardiogram may overlook certain morphological or functional alterations. Cardiac magnetic resonance (CMR) is recommended for survivors of cardiac arrest (CA) without a clear underlying cause (class I, level B). There is a lack of data from multicenter studies. Our aim is to assess whether CMR helps to clarify the aetiology of CA in our setting.

Retrospective observational study of survivors of CA with good neurological outcome with suspected cardiac cause admitted to Cardiology from October 2016 to April 2024. The patients did not show significant coronary lesions or those considered to be responsible for the arrest. CMR was performed for aetiological study and, on an individual basis, electrophysiology study, provocation test and/or genetics. Baseline characteristics and results of complementary tests were recorded.

Thirty-two patients were included (figure 1). The average age was 50±9 years, over half were men (62,5%), and the majority had a shockable rhythm (87.5%). Genetic testing revealed a variant of uncertain significance or pathogenic in 40.6%. CMR found left ventricular (LV) systolic dysfunction in 31.3%, dilation in 18.8%, hypertrophy in 9.4%, and nonspecific morphological alterations in 9.4%. Similarly, right ventricular (RV) systolic dysfunction was observed in 9.4%, dilation in 6.3%, and morphological alterations in 6.3%. Diffuse fibrosis or interstitial disease was noted in 21.9%, edema in 18.8%, and late gadolinium enhancement in LV and/or RV in 40.6%. Figure 2 shows CMR diagnosis and final diagnosis based on initial suspicion. CMR reclassified 37.5% of patients and provided the diagnosis in 62.5% of patients.

CMR is a non-invasive test that constitutes a valuable tool in the context of initially non-ischemic CA, providing a comprehensive evaluation of cardiac structure, function, and tissue characterization. Routine use of CMR after CA decreases the percentage of patients classified as idiopathic ventricular fibrillation and reclassifies the diagnosis in more than a third, with consequences for the management and prognosis of the patient and their families.

Demographic data and complementary tests