ARRHYTHMIAS IN THYROID DYSFUNCTIONS
Background: Hyperthyroidism is associated with supraventricular rhythm disturbancies due to excess of thyroid hormone, while hypothyroidism is accompanied by sinus bradicardia, ventricular ectopic activity and dysfunctions of conduction tissue.
Our aim was to determine the incidence and characteristics of arrhythmias in thyroid dysfunctions and their possible correlations with the severity of the disease.
Material and method: We studied 192 patients with hypo- and 203 with hyperthyroidism, admitted between October 2009 and October 2012 in the Endocrinology Clinic of County Hospital Timisoara and evaluated by the cardiologist. In order to asses the presence of rhythm disturbances, related to thyroid disfunctions, we performed 24 hours ECG Holter monitoring in a subgroup of 42 hypothyroid and 54 hyperthyroid patients, without former cardiovascular pathology. We used GraphPad Instat for the statistic analyse.
Results: Referring to hypothyroid patients with overt and subclinical forms, we found an increased incidence of sinus bradycardia, (39.06, respective 78.57%) on the ECG and Holter monitoring. 18, 22% of the patients had conduction disturbances. Although the incidence of ventricular ectopic activity was reduced on the ECG (4.68%), on the Holter monitoring, we found in 26.19% of the patients premature ventricular beats, or even nonsustained ventricular tachycardia.
In the group of hyperthyroid patients we found on the ECG and Holter monitoring an increased incidence of sinus tachycardia (54.18%, respective 61,11%) in direct relation with the severity of the thyroid dysfunction (p=0.02, Fisher”s Exact Test). Although increased, the incidence of ectopic supraventricular activity (51.85% in overt and 38.76% in subclinical forms) and of paroxysmal atrial fibrillation (24.07% in overt and 15.38% in subclinical forms), there was no significant statistic difference between the groups.
Conclusions: In hypothyroidism prevailed sinus bradycardia, supraventricular and ventricular ectopic activity and intraventricular conduction disturbances, while in hyperthyroidism there was an increased incidence of sinus tachycardia and supraventricular arrhythmias.