Accessory papillary muscles and papillary muscle hypertrophy are associated with sudden cardiac arrest of unknown cause

Background The present study was performed for elucidating the associations between the morphology of the papillary muscles (PMs) and sudden cardiac arrest (SCA). Methods We retrospectively reviewed history, laboratory data, electrocardiography, echocardiography, coronary angiography, and cardiac CT/MRI for 190 patients with SCA. The prevalence of accessory PMs and PM hypertrophy in patients with SCA of unknown cause was compared with that in patients with SCA of known causes and 98 age- and sex-matched patients without SCA. An accessory PM was defined as a PM with origins separated from the anterolateral and posteromedial PMs, or a PM that branched into two or three bellies at the base of the anterolateral or posteromedial PM. PM hypertrophy was defined as at least one of the two PMs having a diameter of ≥ 1.1 cm. Results In 49 patients (age 49.9 ± 15.9 years; 38 men) the cause of SCA was unknown, whereas 141 (age 54.2 ± 16.6 years; 121 men) had a known cause. The prevalence of accessory PMs was significantly higher in the unknown-cause group than in the known-cause group (24.5% and 7.8%, respectively; p = 0.002) or the no-SCA group (7.1%, p = 0.003). The same was true for PM hypertrophy (unknown-cause 12.2%, known-cause 2.1%, p = 0.010; no SCA group 1.0%, p = 0.006). By logistic regression, accessory PM and PM hypertrophy were independently associated with sudden cardiac arrest of unknown cause. Conclusions An accessory PM and PM hypertrophy are associated with SCA of unknown cause.