Association of Polycythemia with Outcomes of Acute Coronary Syndrome

Background: Polycythemia has not been extensively studied for its impact on acute coronary syndrome (ACS) outcomes. A previous study reported only 30-day outcomes to be worse in these patients. Methods: Data from the ACS Israeli survey between 2000 and 2018 were utilized to compare between 3 groups of patients with ACS: anemic group (hemoglobin <12 g/dL for women and <12.5 g/dL for men), normal hemoglobin group, and polycythemic group (>16 g/dL and >16.5 g/dL, respectively). Measured outcomes included 30-day major adverse cardiac events (MACE comprising all-cause mortality, recurrent ACS, need for urgent revascularization, and stroke) and 1- and 5-year all-cause mortality. Results: Of 14,746 ACS patients, 10,752 (72.9%) had normal hemoglobin levels, 3,492 (23.7%) were anemic, and 502 (3.4%) were polycythemic. In comparison with normal and anemic patients, polycythemic patients were younger (55.9 ± 10.5 vs. 61.9 ± 12.4 and 71.1 ± 12.2 for anemic, respectively, p < 0.001 for both), more frequently men (93.8% vs. 81.3% and 63.1%, respectively, p < 0.001), and less likely diabetic or hypertensive. Upon adjustment to baseline characteristics, compared with normal hemoglobin, polycythemia was not independently associated with 30-day MACE or 1-year mortality, but it was independently associated with higher risk for 5-year mortality (HR 1.76, 95% CI: 1.19-2.59, p = 0.005). Similar results were observed after propensity score matching. Conclusions: Although younger and with fewer comorbidities, polycythemic ACS patients are at increased risk for long-term all-cause mortality. Further study of this association is warranted to understand the causes and possibly to improve the outcomes of these patients.