The platelet to lymphocyte ratio in heart failure: a comprehensive review.

Introduction: At the crossroads of heart failure (HF) and systemic inflammation, platelets and lymphocytes are both influenced as well as actively participating in the bidirectional relationship. The platelet to lymphocyte ratio (PLR) could therefore be a marker of severity. This review aimed to assess the role of PLR in HF. Methods: We searched the PubMed (MEDLINE) database using the keywords "platelet", "thrombocyte", "lymphocyte", "heart failure", "cardiomyopathy", "implantable cardioverter defibrillator", "cardiac resynchronization therapy" and "heart transplant". Results: We identified 320 records. 21 studies were included in this review, with a total of 17,060 patients. PLR was associated with age, HF severity, and comorbidity burden. Most studies reported the predictive power for all-cause mortality. Higher PLR was associated with in-hospital and short-term mortality in univariable analysis, however, it was not consistently an independent predictor for this outcome. PLR > 272.9 associated an adjusted HR of 3.22 (95%CI 1.56 - 5.68, p<0.001) for 30-day fatality. During long-term follow-up from 6 months to 5 years, PLR was an independent predictor of mortality in most studies, with cut-off values ranging from > 150 to > 194.97 and adjusted HR from 1.47 (95%CI 1.06 - 2.03, p=0.019) to 5.65 (95%CI 2.47-12.96, p<0.001). PLR > 173.09 had an adjusted OR 2.89 (95%CI 1.17-7.09, p=0.021) for predicting response to cardiac resynchronization therapy. PLR was not associated with outcomes after cardiac transplant or implantable cardioverter-defibrillator. Conclusion: Increased PLR could be an auxiliary biomarker of severity and survival prognosis in HF patients.