P wave duration and dispersion in patients with hyperthyroidism and the short-term effects of antithyroid treatment

Prolonged P wave duration and P wave dispersion (PWD) have been associated with an increased risk for atrial fibrillation (AF). Hyperthytodism is a frequent cause of atrial fibrillation (AF).

Forty-two patients with newly diagnosed overt hyperthyroidism and 20 healthy people were enrolled in the study. Transthoracic echocardiography, 12 lead surface ECG and thyroid hormone levels were studied at the time of enrollment and after achievement of euthyroid state with propylthiouracil treatment.

Maximum P wave duration (Pmax) (97.4+/-14.6 vs. 84.2+/-9.5 msec, p<0.001), PWD (42.9+/-10.7 vs. 31.0+/-6.2 msec, p<0.001), deceleration (DT) (190.7+/-22.6 vs. 177.0+/-10.2 msec, p=0.013) and isovolumetric relaxation times (IVRT) (90.9+/-11.2 vs. 79.6+/-10.5 msec, p<0.001) were significantly higher in hyperthyroid patients compared to control group. Pmax and PWD were significantly correlated with the presence of hyperthyroidism. Pmax (97.4+/-14.6 to 84.3+/-8.6 msec, p<0,001) Pmin (54.1+/-8.6 to 48.1+/-8.5 msec, p=0.002), PWD (42.9+/-10.7 to 35.9+/-8.1 msec, p=0.002) and DT (190.7+/-22.6 to 185.5+/-18.3, p=0.036) were significantly decreased after achievement of euthyroid state in patients with hyperthyroidism. Diastolic dyfunction was seen in 5 patients at hyperthroid state but only in one patient at euthyroid state.

Hyperthyroidism is associated with prolonged P wave duration and dispersion. Achievement of euthyroid state with propylthiouracil treatment results in shortening of P wave variables. Diastolic function may have a partial effect for the increased Pmax and PWD. Shortening of Pmax and PWD may be a marker for the prevention of AF with the anti-thyroid treatment.