Clinical and pathologic features of out-of-hospital cardiac arrest in pregnancy: insights from a state-wide registry

Abstract

Abstract Background Cardiovascular disease is the most common cause of indirect maternal mortality worldwide, and cardiac arrest occurs in up to 1 in 12,000 pregnancies. Objective To define rates, clinical and pathologic factors of out-of-hospital cardiac arrest (OHCA) in pregnant and post-partum females. Methods A prospective state-wide cardiac arrest registry combining ambulance, hospital and forensic data captured all OHCAs from 2019–2021. Clinical and pathological details for pregnant patients were identified. Results 1,482 OHCAs occurred, including 376 females of child-bearing age of whom eight were pregnant or post-partum. OHCA incidence was lower in pregnant females compared to non-pregnant females of child-bearing age (5.2 OHCAs per 100,000 pregnant females vs 23.1 per 100,000 females of child-bearing age, p<0.0001). Seven patients (87.5%) died, with five (62.5%) having a cardiac cause of OHCA (unascertained = 2, cardiomyopathy = 2 (1 hypertrophic), ischemic heart disease = 1). Two patients had pre-existing cardiac risk factors, but none had a cardiac diagnosis pre-arrest. Compared to in-hospital cardiac arrests (IHCAs) in pregnancy, OHCAs are more likely to have a cardiac cause (odds ratio 3.81) and lower maternal survival (odds ratio 0.09). Conclusion Maternal OHCA affects approximately 1 in 20,000 pregnancies with high maternal mortality rates. OHCA occurs at one-quarter the rate in non-pregnant females of child-bearing age. Approximately two-thirds of maternal OHCAs had an underlying cardiac cause, but low rates of cardiac diagnosis pre-arrest. OHCAs differ markedly from IHCAs in pregnant females, requiring ongoing evaluation as to specific causes and preventability. Funding Acknowledgement Type of funding sources: Public Institution(s). Main funding source(s): NHMRC, NHF