Risk assessment in the development of atrial fibrillation at patients with associate thyroid dysfunctions

Thyroid hormones are an important regulator of cardiac function and vascular system. Atrial fibrillation is a common cardiac arrhythmia and an important risk factor for the ischemic cerebral vascular accident and heart failure.

The examination of the risk to develop atrial fibrillation in relation to the whole spectrum of thyroid dysfunctions.

All participants to our study were selected from among subjects with cardiovascular disorders whose hormonal thyroid status had been controlled previously and who hadn't been treated for thyroid functional disorders. Based on these criteria we defined a study lot made up of 791 subjects, 700 women and 91 men, aged between 22 to 86, with a mean age of approximately 60 years old, divided into five groups, based on the level of thyroid hormones. Once the lot was constituted, evaluations were made of the cardiovascular and thyroid condition at 6 and 12 months.

During monitoring, most patients who developed atrial fibrillation were registered in the groups with manifest clinical hyperthyroidism, 34,62% and respectively with subclinical hypothyroidism, 38,6%. The main risk factors at the patients with manifest clinical hyperthyroidism were: female gender (RR=1.97) and age above 60 (RR=1.33), as well as the presence of coronary disease in the personal pathological record (RR=3.31), HBP (RR=1.46) and cardiac frequency in excess of 80 beats/min (RR=1.38). The main risk factors that led to atrial fibrillation among the patients with subclinical hypothyroidism, were: obesity (RR=2.21), the presence in the personal record of heart disease (RR=2,0), age over 60 (RR=1.90) and female sex (RR=1.30). At the patients who had been administered beta blockers prior to admission (RR=0.99), ACEI (RR=0.85) and/or antiarrythmic drugs (RR=0.54), the medication represented a protective factor against developing atrial fibrillation.

Thyroid dysfunctions are associated with an increased risk to develop atrial fibrillation, both in the case of clinically manifest and the subclinical manifest forms. These results support long term screening for thyroid dysfunctions for patients with atrial fibrillation.