Prolonged follow-up after apparently unexplained sudden cardiac arrest: A retrospective study

We hypothesized that a prolonged follow-up of survivors of unexplained sudden cardiac arrest (USCA) would subsequently unmask electrical heart disorders in a significant proportion of cases.

We retrospectively analyzed all out-of-hospital cardiac arrest (OHCA) admitted alive in our cardiac arrest center over 20-years (2002-2022). The diagnosis of USCA was made when no etiology was found after thorough initial hospital investigations. We identified all the new diagnoses established during follow-up, and compared outcomes according to underlying heart diseases.

Out of the 2482 OHCA patients, 68 (2.7%) were initially classified as USCA and 30 (1.2%) with electrical heart disorders. Compared to other cardiac etiologies of OHCA, both USCA and electrical heart disorders patients were younger (mean age 48.5 and 43.5 year-old respectively, versus 62.5 year-old; p < 0.0001), with a higher rate of family history of SCA (17.6 and 23.3% respectively versus 9.2%; p = 0.003). Six patients in each group were lost to follow-up at discharge (6/68, 8.8% in the USCA group, 6/30 20% in the electrical heart disorders group). During a mean follow-up of 8.1 ± 6.3 years, a diagnosis was eventually established in 24.3% of USCA patients (9/35), most of them as electrical heart disorders (55.6%, 5/9). No post-discharge death occurred in both USCA and electrical heart disorders groups, with approximately 10% of appropriate therapy delivered by the implantable cardioverter defibrillator.

Our findings emphasized that approximately a quarter of patients who had been initially considered as having apparently USCA after index hospital stay actually reveal heart conditions, especially electrical heart disorders.