title: QTc dispersion in hyperthyroidism and its association with pulmonary hypertension.
abstract: BACKGROUND
  Several studies have reported that hyperthyroidism is associated with prolonged QT interval corrected by the heart rate (QTc) and pulmonary hypertension (PHT).
  
  
  METHODS
  Forty-seven patients with newly diagnosed overt hyperthyroidism and 20 healthy people were enrolled in the study. Transthoracic echocardiography, 12-lead surface electrocardiogram, and thyroid hormone levels were studied at the time of enrollment and after achievement of euthyroid state with propylthiouracil treatment.
  
  
  RESULTS
  Baseline clinical characteristics were similar. However, heart rate (90.5+/-19.6 vs 79.2+/-13.7 bpm, P = 0.024), pulmonary artery systolic pressure (PASP) (26.0+/-12.0 vs 10.6+/-4.0 mmHg, P < 0.001), E deceleration time (DT) (191.8+/-25.6 vs 177.0+/-10.7 ms, P = 0.016), isovolumetric relaxation time (IVRT) (91.38+/-12.3 vs 79.6+/-10.5 ms, P < 0.001), and QTc dispersion (QTcD) (50.3+/-17.2 vs 38.9+/-11.6 ms, P = 0.009) were significantly higher in hyperthyroid patients compared to control group. Heart rate (to 74.1+/-13.8, P < 0.001), QTcD (to 37.3+/-10.1 ms, P < 0.001), DT (to 185.3+/-19.7 ms, P = 0.008), IVRT (to 88.6+/-10.3 ms, P = 0.056), and PASP (23.1+/-10.1 mmHg P < 0.001) were significantly decreased after achievement of euthyroid state. Although PHT was present in 16 patients before treatment only six patients still had PHT during euyhyroid state. Compared to patients with normal PASP, QTcD was significantly longer in patients with PHT (56.5+/-15.8 vs 37.9+/-12.8 mmHg P < 0.001). There were also significant correlations between QTcD and presence of PHT (r = 0.516, P < 0.001) and PASP (r = 0.401, P = 0.009).
  
  
  CONCLUSIONS
  Hyperthyroidism is a reversible cause of PHT and diastolic dysfunction. Increased QTcD observed in hyperthyroidism may be associated with PHT and diastolic dysfunction. These abnormal findings in hyperthyroidism often normalize with the achievement of euthyroid state.
authors.affiliation: Yuzuncu Yil University, Faculty of Medicine, Cardiology Department, Van, Turkey. guntekinunal@hotmail.com
authors.forename: Unal
authors.initials: U
authors.lastname: Guntekin
authors.forename: Yilmaz
authors.initials: Y
authors.lastname: Gunes
authors.forename: Mustafa
authors.initials: M
authors.lastname: Tuncer
authors.forename: Hakki
authors.initials: H
authors.lastname: Simsek
authors.forename: Hasan Ali
authors.initials: HA
authors.lastname: Gumrukcuoglu
authors.forename: Sevket
authors.initials: S
authors.lastname: Arslan
authors.forename: Ahmet
authors.initials: A
authors.lastname: Gunes