Study objectives: QT dispersion (QTd) is the maximal interlead difference in QT interval on surface 12-lead ECG. An increase in QTd is found in various cardiac diseases. Sarcoidosis augments inhomogeneity in ventricular repolarization by sarcoid granuloma, which significantly correlates with ventricular fibrillation. Changes in QTd in the course of sarcoidosis have not been investigated previously.
Design: The study included 35 patients with systemic sarcoidosis. The diagnosis of systemic sarcoidosis was made by biopsy. Thallium scintigraphy was performed in all patients with systemic sarcoidosis. Cardiac sarcoidosis was diagnosed in 16 patients based on abnormal thallium scintigraphy and normal coronary arteriography results. QTd, corrected QTd (cQTd), maximum QT (QTmax), maximum corrected QT (cQTmax), minimum QT, and minimum corrected QT intervals were measured. Twenty-four healthy subjects represented the control group for QT interval analysis.
Measurements and results: In the cardiac sarcoidosis group, mean QTd (± SD) was significantly greater than in the noncardiac sarcoidosis group and control group (49.50 ± 10.86 ms, 28.14 ± 11.02 ms, and 27.08 ± 10.41 ms, respectively; p < 0.001). cQTd was significantly greater in the cardiac sarcoidosis group than in the noncardiac sarcoidosis group and control group (53.17 ± 10.44 ms, 30.61 ± 10.94 ms, and 29.01 ± 10.52 ms, respectively; p < 0.001). QTmax (440 ± 15.01 ms, 409 ± 14.86 ms, and 410 ± 13.21 ms; p < 0.001) and cQTmax (449 ± 16.31 ms, 417 ± 12.51 ms, and 418 ± 11.76, respectively; p < 0.001) were also significantly greater in patients with cardiac sarcoidosis. In a limited follow-up group (11 cardiac and 9 noncardiac sarcoidosis patients), the incidence of premature ventricular contraction (PVC) on ECG was greater in the cardiac sarcoidosis group than in the noncardiac sarcoidosis group (36% and 0%, respectively; p < 0.05). A medium correlation existed between QTd and PVC (r = 0.331, p < 0.05).
Conclusions: QTd, cQTd, QTmax, and cQTmax are prolonged in patients with cardiac sarcoidosis compared to the patients with noncardiac sarcoidosis and control subjects. The incidence of PVC on ECG was greater in the cardiac sarcoidosis group than in the noncardiac sarcoidosis group.