Blood count in new onset atrial fibrillation after acute myocardial infarction – A hypothesis generating study

BACKGROUND & OBJECTIVES Atrial fibrillation (AF) is a common complication after acute myocardial infarction (AMI) and associated with increased morbidity and mortality. Previous studies identified high white and red blood cell count as potential risk factors for new onset AF. The objective of this retrospective, nested case-control study was to examine the association of different parameters of the blood count with the development of new onset of AF after AMI. METHODS A total of 66 consecutive patients with new onset AF after AMI and 132 sex and age matched controls were enrolled into the study and analyzed whether parameters of the blood count, including leukocytes, platelets, haemoglobin, haematocrit or erythrocyte count, are associated with the occurrence of AF after AMI. All AMI patients had undergone coronary angiography. RESULTS Patients with post-AMI AF displayed significantly higher levels of haemoglobin (14.2 g/dl, IQR 12.4-15 vs. 12.9 g/dl, IQR 11.7-13.8; P< 0.001), haematocrit (41.7 %, IQR 36.6-44.3 vs. 38.7 %, IQR 34.7-41.5; P 0.0015), and erythrocyte count (4.6 T/l, IQR 4.1-5 vs. 4.2 T/l, IQR 3.9-4.65; P< 0.001). In the unadjusted and adjusted logistic regression analysis, the blood parameters most strongly associated with the outcome were serum haemoglobin (crude OR 2.20, 95% CI 1.40- 3.47, P 0.001; adjusted OR 3.82, 95% CI 1.71- 8.54, P 0.001) and erythrocyte count (crude OR 2.10, 95% CI 1.36-3.22, P 0.001; adjusted OR 3.79, 95% CI 1.73- 8.33, P 0.001), whereas haematocrit did not reach statistical significance. INTERPRETATION & CONCLUSIONS This study shows a significant independent association between serum haemoglobin, haematocrit, erythrocyte count and occurrence of AF after AMI. However, the pathophysiologic mechanism underlying these associations and its potential clinical applicability need to be further elucidated.