Hematological parameters in atrial fibrillation: A literature review

Table 1 The pathophysiological aspects of hematological parameters in atrial fibrillation

Hematological parameters	Pathophysiological aspects
Haemoglobin	Undetermined
Hematocrit	Undetermined
Platelet	(1) A specific reduction in platelet aggregation in response to thrombin receptor activating peptide, which activates the thrombin receptor protease-activated receptor-1, was observed in all AF patients; (2) Acute episodes of AF results in a decrease in MPs-associated tissue factor activity, possibly corresponding to consumption, which in turn favors coagulation and the local production of thrombin; and (3) A decreased platelet basal aggregation to thrombin receptor activating peptide may result from protease-activated receptor-1 desensitization, whereas the improved response after an induced episode of AF suggests activation of coagulation and protease-activated receptor-1 re-sensitization
WBC count	Only consistent inflammatory marker associated with postoperative new-onset AF
Lymphocytes	(1) CD4+ CD28null T lymphocytes play a crucial role in the development and progression of AF; and (2) Notably, these cells are believed to be a key player in a T-cell-mediated autoimmune reaction against myocardial tissue
Neutrophils	(1) Inflammation and in particular leukocyte activation predisposes to AF; (2) CD11b-integrin mediated atrial polymorphonuclear neutrophils infiltration to the formation of fibrosis, which promotes the initiation and propagation of AF; (3) Neutrophil extracellular traps were increased significantly in AF patients and positively correlated with Spontaneous echo contrast grades; and (4) Neutrophil extracellular trap levels increased significantly in the left atrial appendage and promoted thrombosis
Monocytes	(1) High monocyte counts independently predict the occurrence of MACE, major bleeding and mortality, but not SSE; (2) A higher number of CCR2-positive monocytes/macrophages in the left atrial appendages in the enlarged left atrium group; (3) Enhanced migratory activity in circulating and local monocytes may play a pivotal role in the pathogenesis of progression in atrial remodeling in AF patients; (4) An elevated preablation monocyte/high-density lipoprotein ratio was associated with an increased risk of the postoperative recurrence of AF; (5) Intermediate CD14++ CD16+ monocytes are associated with incident atrial fibrillation independently of other common risk factors in the general population, supporting the role of inflammatory cells in AF; (6) Elevated pre-ablation monocyte-to-high-density lipoprotein high-density lipoprotein ratio was associated with an increased recurrence of AF after cryoballoon-based catheter ablation; (7) The monocyte-to-high-density lipoprotein ratio was found to be associated with the occurrence of atrial high-rate episodes in patients with cardiac implantable electronic devices; (8) Increased monocyte count in subjects with heart failure is related to the development of AF; (9) The chemokine receptor CXCR-2 is a critical regulator of monocyte mobilization in hypertension and cardiac remodeling; (10) CXCR-2 in driving monocyte infiltration of the atria, which accelerates atrial remodeling and AF after hypertension; and (11) The intermediate monocytes and toll-like receptor 4 expressions positively correlated with the expansion of low-voltage zones in AF patients
Lymphocyte-to-monocyte ratio	Undetermined
Eosinophils	Especially, the peripheral eosinophil and left atrial diameter may play important roles in mediating inflammation and atrial remodeling in AF
Neutrophil to lymphocyte ratio	(1) Independent predictors of AF recurrence; (2) In PAF patients, high NLR indicates thrombogenesis with a high degree of certainty and is associated with reduced left atrial appendage contraction rather than with left atrial body function; (3) NLR increases in diabetic patients with AF when compared to diabetic patients without atrial fibrillation; and (4) NLR might be associated with thrombosis and bleeding risk scores and might predict cardio-embolic risk in nonvalvular atrial fibrillation patients within the therapeutic international normalized ratio
Platelet to lymphocyte ratio	(1) Elevated PLR is a marker of increased inflammation and may serve as a practical and inexpensive predictor for recurrence during 6 months of follow-up in patients with non-valvular persistent AF who had restoration of the sinus rhythm after successful ECV; (2) Patients with an elevated preoperative PLR were at higher risk of AF after coronary artery bypass graft surgery; (3) The PLR was lower in patients with nonvalvular atrial fibrillation and with a decreased left atrial appendage flow velocity; (4) Its correlation with left atrial strain might indicate the role of inflammation in the progression of atrial remodeling and the prothrombotic state; and (5) PLR may be an independent risk factor for left atrial appendage thrombogenic milieu in nonvalvular AF patients
Monocyte to lymphocyte ratio	(1) Indicators of systemic inflammatory response because systemic inflammation is associated with the alternation in peripheral blood leukocytes; and (2) NLR and MLR changes are associated with early recurrence of atrial fibrillation, and NLR change is related to late recurrence of AF after pulmonary vein isolation
Red blood cell distribution width	(1) Reflects the heterogeneity of the volume and size of red blood cells; (2) RDW and left atrial dimension were the only independent risk factors associated with AF; (3) Red blood cell distribution width was associated with the incidence of AF independently of several cardiovascular, nutritional and hematological factors; (4) Elevated RDW levels may be an independent risk marker for nonvalvular AF, affected by the type of AF and altitude; and (5) Red cell distribution width is directly associated with the risk of stroke regardless of anemia status and improves the predictive accuracy for stroke in patients with AF

WBC: White blood cell; AF: Atrial fibrillation; MPs: Microparticles; CD: Cluster of differentiation; MACE: Major adverse cardiovascular event; SSE: Systemic embolisms; CCR2: CC chemokine receptor 2; PAF: Paroxysmal atrial fibrillation; NLR: Neutrophil-to-lymphocyte ratio; PLR: Platelet-to-lymphocyte ratio; MLR: Monocyte-to-lymphocyte ratio; ECV: Electrical cardioversion; RDW: Red cell distribution width.