Syncope and risk of sudden cardiac arrest in coronary artery disease

Background Syncope has been associated with increased risk of sudden cardiac arrest (SCA) in specific patient populations, such as hypertrophic cardiomyopathy, heart failure, and long QT syndrome, but data are lacking on the risk of SCA associated with syncope among patients with coronary artery disease (CAD), the most common cause of SCA. We investigated this association among CAD patients in the community. Methods All cases of SCA due to CAD were prospectively identified in Portland, Oregon (population approximately 1 million) as part of the Oregon Sudden Unexpected Death Study 2002–2015, and compared to geographical controls. Detailed clinical information including history of syncope and cardiac investigations was obtained from medical records. Results 2119 SCA cases (68.4±13.8years, 66.9% male) and 746 controls (66.7±11.7years, 67.0% male) were included in the analysis. 143 (6.8%) of cases had documented syncope prior to the SCA. SCA cases with syncope were >5years older and had more comorbidities than other SCA cases. After adjusting for clinical factors and left ventricular ejection fraction (LVEF), syncope was associated with increased risk of SCA (OR 2.8; 95%CI 1.68–4.85). When analysis was restricted to subjects with LVEF ≥50%, the risk of SCA associated with syncope remained significantly elevated (adjusted OR 3.1; 95%CI 1.68–5.79). Conclusions Syncope was associated with increased risk of SCA in CAD patients even with preserved LV function. These findings suggest a role for this clinical marker among patients with CAD and normal LVEF, a large sub-group without any current means of SCA risk stratification.