Introduction: Heart failure (HF) affects platelet acti-vation, function, as well as the production of platelets from megakaryocytes. Low platelet counts have been described in HF patients, however without clear dis-tinction whether this is a consequence of HF severity or an independent comorbidity contributing to worse outcomes.

Objective: Our purpose was to assess the prognostic role of thrombocytopenia (TCP) in HF patients.

Methods: Patients with HF admitted to our Cardiology Department were included in this study, after excluding acute coronary syndromes, pulmonary embolisms, in-fections, malignancy and hepatic cirrhosis. TCP was defined as a platelet number below 150.000/uL and clas-sified as severe below 50.000/uL and moderate between 50.000-100.000/uL. Patients with a left ventricular ejection fraction (LVEF) <40% were classified as HF with reduced EF (HFrEF), those with a LVEF between 40 and 49% as HF with mid-range EF (HFmrEF) and the rest as HF with preserved EF (HFpEF). All-cause mor-tality was assessed after a mean follow-up of 5.5 years.

Results: We included 1142 patients, with a mean age of 72.45 ± 10.53 years. 51.6% were female. 121 had TCP, of which 3 had severe and 21 had moderate TCP. All-ca-use long-term mortality was 43.8%. Patients with TCP had a higher risk ratio for mortality compared to pati-ents with normal platelet counts (RR 1.35, 95%CI 1.14-1.60, p=0.002). Patients with severe TCP had a risk ra-tio of 2.29 (95%CI 2.14-2.45, p=0.049), those with mo-derate TCP had a risk ratio of 1.80 (95%CI 1.39-2.33, p=0.006) and those with mild TCP had a risk ratio of 1.23 (95%CI 1.01-1.51, p=0.06) of mortality, compared to patients with normal platelet counts. Patients with TCP and HFpEF (RR 1.66, 95%CI 1.16-2.37, p=0.021) or HFrEF (RR 1.35, 95%CI 1.09-1.68, p=0.03) had hi-gher risk of mortality, but not those with HFmrEF and TCP (RR 1.09, 95%CI 0.67-1.76, p=0.73), possibly due to the predominance of mild TCP (80.9%). In multi-ple regression analysis, after adjusting for age and sex, alongside NT-proBNP levels and LVEF, moderate TCP (p=0.031) was an independent predictor of mortality, but not mild TCP (p=0.415). Due to the very low num-ber of patients, no multiple regression analysis could be computed with severe TCP.

Conclusions: T hrombocytopenia is an independent predictor of mortality in HF patients, especially platelet counts below 100.000/uL. In both patients with HFrEF and HFpEF this easily available biomarker could be a useful tool for prognosis assessment.