cardiac arrhythmias.

It is well-known that Atrial Fibrillation (AF) is the commonest type of cardiac arrhythmias. The risk factors for AF have been investigated for years however, lone AF is idiopathic which means that there is no definite cause or risk factors for it. It usually affects young age groups; and because all the risk factors have been overlooked, the link between ABO system and cardiac arrhythmias in general has not been investigated yet. Based on that, we decided to set this study to figure out the link between ABO blood group and lone AF.This case series study was conducted over a period of one year (September 2016 to September 2017). A consecutive non random sampling technique was adopted by pooling all the patients with AF attended the emergency department in two main teaching hospitals (Al-Yarmouk Teaching hospital and Baghdad Medical City Teaching Hospital) during the total year data collection period. A total of 100 patient (52 females and 48 males) was collected, all were diagnosed by the cardiologist to have lone AF, their ages ranged between (20-60) years. The mean age of the study group was (40.36 +10.90) years, means of Blood parameters were as follow: for blood group A; glucose was (5.20+0.98) mmol/L, creatinine (1.15+0.28) md/dl, Sodium (146.02+4.47) meq/L and potassium (4.45+0.41)meq /L, P value <0.1. For blood group B: (4.73+0.82) mmol/L, (0.85+0.12) md/dl, (141.33+6.03) meq/L, (4.36+0.52) meq/L, P <0.2. Blood group AB: (5.14+0.96) mmol/L, (0.97+0.29) mg/dl, (145.57+5.34) meq/L, (4.17+0.51) meq/L and P <0.1. Finally blood group O results: (5.2+1.07) mmol/L, (0.99+0.29) mg/dl, (142.52+6.28) meq/L, (3.88+0.70) meq/L, P <0.1. No statistical significance was found in any of these groups.People of blood group A are at a relatively higher risk to develop lone AF than O blood group and other non O blood groups. Key words: Lone Atrial Fibrillation, ABO blood groups, cardiac arrhythmias.