QT Dispersion in the Risk Stratification of Patients with Unstable Angina: Correlations with Clinical Course, Troponin-T and Scintigraphy

This study sought to evaluate the potential prognostie usefulness of QT dispersion (Qtd) in patients hospitalized with a presumed diagnosis of uns table ang ina. QTd was ealculated at the admission ECG of 62 patients presenting to the emergency department with chest pain at rest. Blood sample w as collected for troponin-T (TnT) measurement and all patients had 25-30 mCi of Tc- 99m sestamibi injeetion. SPECT acquisition was performed within 1-6 hours after the injection. SPECT images were scored using 20 segments on a 5-point seale (O=normal, 4=no uptake) and a segment with a seore ~2 was eonsidered to have a perfusion defect. The cut-off value of ~0.1 ng/ml was used to definc an elevated TnT. All patients had one month follow-up in order to assess cardiac events. Cardiae events oeeurred in 41 patients (no death, 1 ı myocardial infarction, 4 urgent and 26 planned revaseularization dittering follow-up. The mean QTd in patients with eardiae events was signifieantly higher than in those without eardiae events (68±28 vs. 54± 1.14 m s; p=O.O ı ). When patients were divided into subgroups according to the cardiae events, the mean QTd in myoeardial infaretion and in revascularization were 90±25 ms and 60±25 ms, respeetively. QTd in patients with myoeardial infaretion was higher than in patients without eardiae events (p=O.OO 1 ). There w as no s ignifieant differenee in QTd between revaseularization subgroup and patients without eardiac events. ı 9 patients w ith elevated TnT indicaling high risk in unstable angina had greater QTd eompared 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 those (66±27 vs. 53±ı7 ms; p=0.03). There was also a moderate eorrelation between QTd and the number of perfusion defects (r=0.3 ı , p=O.O 1 ). On the other hand, most of the high-risk patients who had myocardial infaretion or urgent revaseularization had QTd greater than the value of 75 ms. In eonclusion, the measurement of QTd in patients w ith unstable angina may be of heıp in the stratifieation of patients at high risk for adverse eardiae vents, in partieular myoeardial infaretion.