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Usefulness of automatic QT dispersion measurement for detecting exercise-induced myocardial ischemia [Anatol J Cardiol]
Anatol J Cardiol. 2009; 9(3): 189-195

Usefulness of automatic QT dispersion measurement for detecting exercise-induced myocardial ischemia

Bonpei Takase1, Nobuyuki Masaki2, Hidemi Hattori3, Masayuki Ishihara4, Akira Kurita5
1Department of Intensive Care Medicine Self Defense Forces Central Hospital Saitama, Japa
2Department of Intensive Care Medicine, National Defense Medical College, Saitama, Japan
3Division of Biomedical Engineering National Defense Medical College Research Institute, Saitama, Japan
4Division of Biomedical Engineering, National Defense Medical College Research Institute, Saitama, Japan
5Department of Intensive Care Medicine Self Defense Forces Central Hospital Saitama, Japan

Objective: The electrocardiographic index of QT dispersion (QTd) is related to the occurrence of arrhythmia. In patients with suspected or known coronary artery disease, QTd may be affected by exercise. We investigated whether QTd that is automatically calculated by a newly developed computer system could be used as a marker of exercise-induced myocardial ischemia. Methods: The design of this study was prospective and observational. Eighty-three consecutive patients were enrolled in this study. Their QTd was measured at rest and after 3 min of exercise during exercise-stress Thallium-201 scintigraphy and compared with conventional ST-segment changes. The patients were classified into 4 groups (normal group, redistribution group, fixed defect group, redistribution with fixed defect group) based on the result of single photon emission computed tomography. As statistical analysis, one-way ANOVA with post-hoc Scheffe’s method, receiver-operating characteristics (ROC) and multiple logistic regression analysis were performed. Results: At rest, QTd was significantly greater (p<0.05) in the fixed defect group (52±21 ms) and the redistribution with fixed defect group (53±20 ms) than in the normal group (32±14 ms) and the redistribution group (31±16 ms). However, QTd tended to increase after exercise in the redistribution group, while QTd tended to decrease in the normal group, the fixed defect group, and the redistribution with fixed defect group (QTd after exercise, normal group, 28±17 ms, redistribution group, 35±19 ms, fixed defect group, 43±25 ms, redistribution with fixed defect group, 49±27 ms). Exercise significantly increased QTcd (RR interval-corrected QT dispersion) in the redistribution group. The best cut-off values of QTd and QTcd obtained from ROC curves for exercise-induced myocardial ischemia were 41.6 ms and 40.4 ms, respectively (Qtd - AUC 0.68, 95%CI 0.53- 0.83 and QTcd – AUC 0.67, 95%CI 0.55-0.80). Using these values as cut-off ones, QTd, QTcd, and conventional ST-segment change had comparable sensitivities and specificities for detecting exercise-induced myocardial ischemia (sensitivity - 60%, 58% and 49%, respectively; specificity - 78%, 80% and 83%, respectively). In addition, multiple logistic regression analysis showed that QTd (OR=2.01, 95%CI 1.15-4.10, p<0.05), QTcd (OR=2.12, 95% CI 1.02-4.30, p<0.05) and ST-segment change (OR=1.89, 95%CI 1.03-3.40, p<0.05), were the significantly associated with exercise-induced myocardial ischemia. Conclusion: QT dispersion and/or QTcd after exercise could be a useful marker for exercise-induced myocardial ischemia in routine clinical practice.

Keywords: QT interval, coronary artery disease, myocardial ischemia, Thallium-201 scintigraphy, logistic regression analysis, predictive values of tests


Bonpei Takase, Nobuyuki Masaki, Hidemi Hattori, Masayuki Ishihara, Akira Kurita. Usefulness of automatic QT dispersion measurement for detecting exercise-induced myocardial ischemia. Anatol J Cardiol. 2009; 9(3): 189-195


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