Simple electrocardiographic markers for the prediction of paroxysmal atrial fibrillation in hyperthyroidism

Background: Hyperthyroidism is a major cause of paroxysmal atrial fibrillation (AF). The purpose of this study was to evaluate the predictors of AF in the patients with clinical and subclinical hyperthyroidism.Methods and Results: The study population consisted of four groups: group I (57 euthyroid healthy persons), group II (33 patients with subclinical hyperthyroidism), group III (69 patients with overt hyperthyroidism) and group IV (31 patients with overt hyperthyroidism and documented paroxysmal AF). The maximum P wave duration (P maximum) in group IV (114±8 ms) was significantly higher than group I (102±7 ms, p<0.001), group II (106±7 ms, p<0,001) and group III (108±9 ms, p0.005). The P wave dispersion (PWD) was measured as 46±9 ms in group IV and this was significantly higher than group I (29±8 ms, p< 0.001), group II (36±9 ms, p<0.001) and grup III (38±8 ms, p=0.001). The P maximum and PWD were higher in the patients with subclinical hyperthyroidism compared to healthy individuals. Univariate regression analysis revealed that age, P maximum and PWD, multivariate analysis showed that P maximum and PWD were significant predictors of paroxysmal AF. A PWD value of 37.5 ms separated group IV from others with a sensitivity of 90%, specificity of 85%, and positive predictive accuracy of 77%. Conclusion: Simply measuring P maximum and PWD values, we could identify the patients with high risk for the development of AF and these simple ECG parameters may help in clinical judgement to determine the requirement for treatment in the patients with subclinical hyperthyroidism.