Noninvasive diagnosis of cardiac sarcoidosis using microvolt T-wave alternans.

Sarcoidosis is a systemic granulomatous disorder whose prognosis worsens when the heart is involved, and early diagnosis is important. Endomyocardial biopsy is the most helpful diagnostic examination, but suffers from low sensitivity and low specificity. Microvolt T wave alternans (MVTWA) is utilized in noninvasive examinations to detect beat-to-beat changes in the shape of the T wave at the microvolt level. Such beat-to-beat T wave changes arise from beat-to-beat changes in the transmural gradient of action potential duration. We speculate that the granulomatous changes of cardiac sarcoidosis produce cell-to-cell uncoupling and augment the transmural gradients of action potential duration. To examine the clinical significance of MVTWA in the prediction of cardiac involvement in sarcoidosis patients, we obtained MVTWA in a total of 35 sarcoidosis patients with and without cardiac involvement. All patients underwent electrocardiography (ECG), ambulatory electrocardiography, chest radiography, transthoracic echocardiography, and MVTWA examination using a CH 2000 system. We diagnosed cardiac sarcoidosis in 7 patients according to the accepted diagnostic criteria. MVTWA was detected in 6 out of 7 cardiac sarcoidosis patients (85.7%) as opposed to in 2 out of 28 patients without cardiac involvement (7.1%). The difference between the two groups was statistically significant (P < 0.001). The sensitivity and specificity of MVTWA in cardiac sarcoidosis detection were 85.7% and 92.8%, respectively. The positive and negative predictive values were 75% and 96.3%, respectively, with an overall accuracy of 91.4%. Noninvasive examination of MVTWA using a CH 2000 is a useful diagnostic tool for detecting cardiac involvement in patients with sarcoidosis.