Effects of Short-Term Propylthiouracil Treatment on P Wave Duration and P Wave Dispersion in Patients with Overt Hypertyroidism

Abstract

P-wave duration is defined as the time measured from the onset to the offset of the P-wave in surface electrocardiogram (ECG). Prolonged P wave duration and increased P wave dispersion (PWD) have been reported to carry an increased risk for atrial fibrillation. Our aim was to evaluate the role of hyperthyroidism on P wave duration and dispersion, to investigate the effect of anti-thyroid therapy on P wave duration and dispersion. A total of 44 consecutive subjects (22 patients with newly diagnosed overt hyperthyroidism and 22 randomly selected euthyroid healthy subjects) were enrolled in the study. Transthoracic echocardiography, 12 lead surface ECG and thyroid hormone levels were studied at the time of enrollment, in the first and third months of the 6-8 mg/kg/day propylthiouracil therapy. Patients were followed-up for 3 months. Patient and control groups were consisted of age and sex matched subjects. Baseline left atrial diameter was similar between the patient and control groups (3.4+/-0.3 cm and 3.4+/-0.3 cm respectively, p=0.813). The maximum P-wave duration (P maximum) was 113.1+/-6.6 and 105.7+/-4.1 ms in patient and control groups (p=0.001). PWD was 31.5+/-9.5 and 25.2+/-5.9 ms in patient and control groups respectively (p=0.015). At the third month of propylthiouracil treatment P maximum and PWD were decreased in the patient group at statistically significant level and returned back in normal limits (p<0.001 and p=0.001). P wave duration and PWD are found prolonged in hyperthyroid patients and propylthiouracil treatment decreased them effectively. This mechanism may establish how the anti-thyroid treatment may prevent the development of atrial fibrillation in hyperthyroid patients.