QT Dispersion Ratio in Patients with Unstable Angina Pectoris (A New Risk Factor?) V.G. CIN, M.D.,M. CEI.JK,M.D., S. ULUCAN,M.D. Selquk University, School of Medicine, Cardiac Department, Konya, Turkey Summary Background: QT dispersion has been shown to be associated with fatal arrhythmias and sudden death in coronary artery disease. A recent study indicated that marked QT dispersion in electrocardiograms (ECGs) obtained during acute ischemia demonstrated a significant correlation with ventricular tibrillation. Hypothesis: This study investigated the ECG parameters for repolarization (QT dispersion, corrected QT, corrected QT dispersion, and QT dispersion ratio) and their interrelation with acute ischemia. Merh0d.s: QT parameters as well as a newly developed repolarization index, QT dispersion ratio [(QT dispersion/RR interva1)X 1001 were calculated digitally during rest and ischemia in 32 patients with coronary artery disease (rest angina, Braunwald class III). Results were correlated with clinical consequences, mainly arrhythmias, within a follow-up period of 5 k 2 days. RPSM~LSS: While most patients had an increase in all four parameters, only the QT dispersion ratio showed a significant difference when correlated with ventricular arrhythmias (p < 0.001, Fratio=38). Conclusion: QT dispersion ratio appears to be a new and promising parameter in predicting ventricular arrhythmias in patients with acute ischemia. Key words: QT dispersion, unstable angina, acute ischemia Address for reprints: V.G. Cin. M.D. Selquk Universitesi Tip fakiiltesi Kardiyoloji A.B.D. 42080 Konya, Turkey Received: December 19, 19% Accepted with revision: March 3, 1997 Introduction Repolarization abnormalities have been shown to play an active role in leading to secondary arrhythmias in patients with coronary artery disease. Id A recent study indicated that marked QT dispersion in electrocardiograms (ECGs) obtained during acute ischemia demonstrated a signi ficant correlation with ventricular fibrillation.6 In this study a similar interrelation and its possible effect on prognosis in patients with unstable angina pectori\ was investigated. Method Standard 12-lead surface ECGs were obtained during acute anginal episodes and uneventful periods in 32 patients (21 women, 9 men; mean age 64 k 10 years) with coronary ruteiy disease (Braunwald class 111 rest angina). The diagnosis of coronary artery disease was confirmed by observation of at least 1 mm of reversible horizontal ST depression on any two surface ECG leads with simultaneous typical rest angina. RR interval, maximum QT duration (from onset of QRS complex to the end of the T wave), minimum QT duration, QT dispersion (QT max-QT min), QTc (QTRR; QT duration in ms divided by the square root of RR interval: Bazzet’s formula), QTc dispersion (QTc max-QTc min), and QT dispersion ratio [(QTd/RR)X 1001 were calculated in each patient. All calculations were made by computer, using the Quinton 5000 digitalized system, entering manually measured QT intervals. Patients were followed up for a period of 5 rt 2 days with respect to rhythm and conduction disturbances. Continuous ECG monitoring and 24-h Holter recordings were obtained as well. All measurements were made with the patients free ofmedication, except for nitrates (either intravenous or p.0.) and heparin (20000 U/24 h), to avoid interference from adverse electrophysiologic effects. Statistics All figures are expressed as mean k standard deviation. Student’s t-test was used to explain the statistical difference of continuous variables of ECG in Table I. chi-square testing was 534 Clin. Cardiol. Vol. 20, June 1997 TABLE I iQT parameters in ventricular anhythmias (n = 8) iQTd ratio iQTcd iQTd iQTC Angina 8 3 4 3 Rest 0 5 4 5 p Value <0.001 NS NS NS Ahhrcviation.v: NS = not significant, i =increased. applied for discrete variables in Table 11, a p value of < 0.05 was considered significant. Sensitivity was defined by the number of patients with ventricular arrhythmias involving related parameters divided by the total number of ventricular arrhythmias, and specificity was defined by the total number of patients without events that involved related parameters divided by total number of patients without events. The predictive accuracy was calculated by dividing the sum of true positives and true negatives by the total number of patients studied. A stepwise logistic regresion analysis was performed to compare the predictive values of increased QT parameters. Results QT parameters, derived from ECGs during both rest and acute ischemia, are displayed in Table 11. Despite the fact that a nonsignificant difference was observed in average RR intervals, all other average parameters increased during angina (p