Sudden Prehospital Deaths From Brain Arteriovenous Malformations: A Population-Based Study.

BACKGROUND AND OBJECTIVES The number of unexpected prehospital deaths from brain arteriovenous malformations (AVMs) is unknown because existing mortality data are derived from hospital-based cohorts. In this study, we aimed to determine the rate and causes of AVM-related deaths in a large population-based cohort, both in and outside hospitals. We hypothesized that AVMs infrequently cause unexpected prehospital deaths, and when they do, it is typically due to hemorrhages rather than epileptic seizures. METHODS In this population-based cross-sectional study, we examined the AVM-related deaths within the Helsinki University Hospital (HUH) region during 1998-2015, including both diagnosed patients and undiagnosed individuals with prehospital deaths identified at autopsy. Autopsies are legally mandatory in Finland for all unexpected and sudden deaths. Prehospital deaths were identified through autopsy reports, which were obtained from the National Cause of Death Register (using the ICD-10 codes I60.8, I61.0-I61.9, or Q28.0-Q28.3), and the patients who were already diagnosed were identified from the Helsinki AVM Register. Age-standardized detection rates were calculated using the 2013 European Standard Population (ESP)-derived age-specific weights, with 95% CIs derived from the normal approximation of binomial distribution. RESULTS Between 1998 and 2015, we identified 4 unexpected prehospital AVM deaths in undiagnosed individuals (median age 41 years, 50% female) in the HUH region from the National Cause of Death Register data. For the same period, the HUH AVM database revealed 284 newly diagnosed patients with AVM (mean age at diagnosis 41.1 years [SD 18.0 years], 48% female). Altogether, there were 6 AVM-related prehospital deaths, 2 in previously diagnosed patients. Four of the 6 prehospital deaths were caused by AVM-related epileptic seizures and 2 by AVM hemorrhage. Among individuals experiencing their first AVM-related hemorrhage (n = 168), 1.2% experienced prehospital deaths due to hemorrhage. Similarly, of those diagnosed with AVM-related epileptic seizures (n = 69), 5.8% experienced prehospital deaths from seizures. For people with unruptured and ruptured AVMs, 6-month case fatality rates (CIs) from detection were 5.8% (1.7%-10.8%) and 11.9% (7.1%-17.3%), respectively. The crude and ESP-standardized detection rates of AVMs (including prehospital deaths) were 0.80 (0.71-0.89) and 0.78 (0.69-0.87) per 100,000 person-years. DISCUSSION AVM-related prehospital deaths are rare and often caused by epileptic seizures. Most AVM-related deaths occur in hospitals.