QT dispersion in the risk stratification of patients with unstable angina

OBJECTIVE This study sought to evaluate the potential prognostic usefulness of QT dispersion (QTd) in patients with unstable angina. METHODS AND RESULTS QTd was calculated and plasma troponin T (TnT) level was measured and rest perfusion imaging with Tc-99m sestamibi was performed in 62 patients admitted with chest pain at rest. All patients had a follow-up during one month in order to assess cardiac events. Cardiac events occurred in 41 patients (no deaths, 11 myocardial infarctions (MI), 4 urgent and 26 planned revascularizations). The mean QTd in patients with cardiac events was significantly higher than in those without cardiac events (68 +/- 28 vs. 54 +/- 14 ms; p = 0.01). When patients were divided into subgroups according to the cardiac events, the mean QTd in MI and revascularization were 90 +/- 25 ms and 60 +/- 25 ms, respectively. QTd in patients with MI was higher than in patients without cardiac events (p = 0.001). There was no significant difference in QTd between the revascularization subgroup and patients without cardiac events. Nineteen patients with elevated TnT had a greater QTd compared to patients with normal TnT (74 +/- 29 vs. 56 +/- 20 ms; p = 0.008). Additionally, the mean QTd in 46 patients with perfusion defects was slightly higher than in patients without (66 +/- 27 vs. 53 +/- 17 ms; p = 0.03). There was also a moderate correlation between QTd and the number of perfusion defects (r = 0.31, p = 0.01). On the other hand, most of the patients who had a MI or urgent revascularization had a QTd greater than 75 ms. CONCLUSION The measurement of QTd in patients with unstable angina may help to stratify patients at high risk for cardiac events, in particular MI and urgent revascularization.