AimsRecent studies have shown that in more than half of apparently unexplained sudden cardiac arrests (SCA), a specific aetiology can be unmasked by a careful evaluation. The characteristics and the extent to which such cases undergo a systematic thorough investigation in real-life practice are unknown.Methods and resultsData were analysed from an ongoing study, collecting all cases of out-of-hospital cardiac arrest in Paris area. Investigations performed during the index hospitalization or planned after discharge were gathered to evaluate the completeness of assessment of unexplained SCA. Between 2011 and 2016, among the 18 622 out-of-hospital cardiac arrests, 717 survivors (at hospital discharge) fulfilled the definition of cardiac SCA. Of those, 88 (12.3%) remained unexplained after electrocardiogram, echocardiography, and coronary angiography. Cardiac magnetic resonance imaging yielded the diagnosis in 25 (3.5%) cases, other investigations accounted for 14 (2.4%) additional diagnoses, and 49 (6.8%) patients were labelled as idiopathic ventricular fibrillation (IVF) (48.7 ± 15 years, 69.4% male). Among those labelled IVF, only 8 (16.3%) cases benefited from a complete workup (including pharmacological testing). Younger patients [odds ratio (OR) 6.00, 95% confidence interval (CI) 1.80–22.26] and those admitted to university centres (OR 3.60, 95% CI 1.12–12.45) were more thoroughly investigated. Genetic testing and family screening were initiated in only 9 (18.4%) and 12 (24.5%) cases, respectively.ConclusionOur findings suggest that complete investigations are carried out in a very low proportion of unexplained SCA. Standardized, systematic approaches need to be implemented to ensure that opportunities for specific therapies and preventive strategies (including relatives) are not missed.

BackgroundThere are limited data describing sex specificities regarding implantable cardioverter defibrillators (ICDs) in the real‐world European setting.Methods and ResultsUsing a large multicenter cohort of consecutive patients referred for ICD implantation for primary prevention (2002–2012), in ischemic and nonischemic cardiomyopathy, we examined the sex differences in subjects' characteristics and outcomes. Of 5539 patients, only 837 (15.1%) were women and 53.8% received cardiac resynchronization therapy. Compared to men, women presented a significantly higher proportion of nonischemic cardiomyopathy (60.2% versus 36.2%, P<0.001), wider QRS complex width (QRS >120 ms: 74.6% versus 68.5%, P=0.003), higher New York Heart Association functional class (≥III in 54.2%♀ versus 47.8%♂, P=0.014), and lower prevalence of atrial fibrillation (18.7% versus 24.9%, P<0.001). During a 16 786 patient‐years follow‐up, overall, fewer appropriate therapies were observed in women (hazard ratio=0.59, 95% CI 0.45–0.76; P<0.001). By contrast, no sex‐specific interaction was observed for inappropriate shocks (odds ratio ♀=0.84, 95% CI 0.50–1.39, P=0.492), early complications (odds ratio=1.00, 95% CI 0.75–1.32, P=0.992), and all‐cause mortality (hazard ratio=0.87 95% CI 0.66–1.15, P=0.324). Analysis of sex‐by‐ cardiac resynchronization therapy interaction shows than female cardiac resynchronization therapy recipients experienced fewer appropriate therapies than men (hazard ratio=0.62, 95% CI 0.50–0.77; P<0.001) and lower mortality (hazard ratio=0.68, 95% CI 0.47–0.97; P=0.034).ConclusionsIn our real‐life registry, women account for the minority of ICD recipients and presented with a different clinical profile. Whereas female cardiac resynchronization therapy recipients had a lower incidence of appropriate ICD therapies and all‐cause death than their male counterparts, the observed rates of inappropriate shocks and early complications in all ICD recipients were comparable.Clinical Trial RegistrationURL: https://www.clinicaltrials.gov/. Unique identifier: NCT01992458.

Background: Tetralogy of Fallot (TOF) is the most common cyanotic congenital heart disease, and sudden cardiac death represents an important mode of death in these patients. Data evaluating the implantable cardioverter defibrillator (ICD) in this patient population remain scarce. Methods: Nationwide French Registry including all TOF patients with an ICD initiated in 2010 by the French Institute of Health and Medical Research. The primary time to event endpoint was the time from ICD implantation to first appropriate ICD therapy. Secondary outcomes included ICD-related complications, heart transplantation, and death. Clinical events were centrally adjudicated by a blinded committee. Results: A total of 165 patients (mean age 42.2±13.3 years, 70.1% males) were included from 40 centers, including 104 (63.0%) in secondary prevention. During a median (IQR) follow-up of 6.8 (2.5-11.4) years, 78 (47.3%) patients received at least one appropriate ICD therapy. The annual incidence of the primary outcome was 10.5% (7.1% and 12.5% in primary and secondary prevention, respectively, p=0.03). Overall, 71 (43.0%) patients presented with at least one ICD complication, including inappropriate shocks in 42 (25.5%) patients and lead dysfunction in 36 (21.8%) patients. Among 61 (37.0%) primary prevention patients, the annual rate of appropriate ICD therapies was 4.1%, 5.3%, 9.5%, and 13.3% in patients with respectively no, one, two, or ≥ three guideline-recommended risk factors. QRS fragmentation was the only independent predictor of appropriate ICD therapies (HR 3.47, 95% CI 1.19-10.11), and its integration in a model with current criteria increased the 5-year time-dependent area under the curve from 0.68 to 0.81 (p=0.006). Patients with congestive heart failure and/or reduced LVEF had a higher risk of non-arrhythmic death or heart transplantation (HR=11.01, 95% CI: 2.96-40.95). Conclusions: Patients with TOF and an ICD experience high rates of appropriate therapies, including those implanted in primary prevention. The considerable long-term burden of ICD-related complications, however, underlines the need for careful candidate selection. A combination of easy-to-use criteria including QRS fragmentation might improve risk stratification. Clinical Trial Registration: URL: https://clinicaltrials.gov Unique Identifier: NCT03837574

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