Platelet dysfunction after Out of Hospital Cardiac Arrest. Results from POHCAR: A prospective observational, cohort study

AIM: Coagulation and platelet function following out of hospital cardiac arrest (OHCA) at admission to a UK cardiology centre were investigated prospectively in this observational feasibility study, and compared to that of patients receiving percutaneous coronary intervention (PCI) for ST segment elevation myocardial infarction (STEMI).

METHOD: Blood samples taken immediately at emergency department admission from patients after OHCA of probable cardiac origin were analysed using near-patient thromboelastometry and a platelet function analyser. Physiological parameters, demographic information, bleeding rates and 30-day survival were recorded, and compared to that of patients undergoing PCI for STEMI.

RESULTS: Thirty patients were enrolled into each group. Platelet activation with thrombin receptor stimulation was reduced in OHCA patients compared to STEMI patients; mean TRAP AUC OHCA 79.3 (95% CI 63.7-94.9) vs STEMI 101.6 (95% CI 87.4-115.8), p = 0.03. The maximum clot firmness time was prolonged in the OHCA group compared to the STEMI group; 1718s (1545s-1906s) vs 1544s (1387s-1709s), p = 0.01. Other measures of clot formation and strength were comparable between groups. Hyperfibrinolysis (maximum lysis > = 15%) was common in both groups (57% in STEMI; 50% in OHCA) but did not increase 30-day bleeding risk.

CONCLUSION: OHCA patients demonstrated reduced thrombin receptor function at hospital admission but overall clot formation dynamics comparable to STEMI patients, indicating no gross coagulopathy post OHCA in our cohort. Hyperfibrinolysis was common both post OHCA and after STEMI. The results of this small feasibility study cannot draw clinical conclusions but will inform power calculations for future studies.