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Chronotropic response to exercise. Improved performance of ST-segment depression criteria after adjustment for heart
P M Okin1, M S Lauer, P Kligfield
1Division of Cardiology, New York Hospital-Cornell Medical Center, New York 10021, USA. pokin@mail.med.cornell.edu
Insights
Adjusting exercise electrocardiogram (ECG) ST-segment depression for heart rate (HR) reserve significantly improves coronary artery disease (CAD) detection. This enhanced method, particularly the ST/HR index and slope, offers superior sensitivity for identifying CAD.
Area of Science:
- Cardiology
- Exercise Physiology
Background:
- Heart rate (HR) response during exercise is crucial for diagnosing coronary artery disease (CAD).
- Chronotropic incompetence, an attenuated HR response, may independently indicate CAD.
Purpose of the Study:
- To evaluate the diagnostic value of adjusting ST-segment depression for exercise-induced HR changes in CAD detection.
- To assess the efficacy of the ST/HR index and ST/HR slope, corrected for HR reserve, in identifying CAD.
Main Methods:
- The study analyzed 283 controls and 337 CAD patients, calculating ST-segment depression, ST/HR index, and ST/HR slope adjusted for HR reserve.
- Sensitivity and specificity were compared between standard and adjusted measurements at 96% specificity.
Main Results:
- Adjusting for HR reserve significantly improved the sensitivity of ST-segment depression, ST/HR index, and ST/HR slope.
- The adjusted ST/HR index (94% sensitivity) and ST/HR slope (93% sensitivity) demonstrated significantly higher accuracy than adjusted ST-segment depression (87% sensitivity).
Conclusions:
- Correcting for attenuated HR response enhances the diagnostic performance of exercise ECG criteria for CAD.
- Routine assessment of chronotropic reserve is recommended for comprehensive CAD evaluation using exercise ECG.
Background:
Heart rate (HR) response to exercise plays an important role in the diagnosis of coronary artery disease (CAD). Adjustment of ST-segment depression for the change in HR with exercise increases the accuracy of the exercise ECG in the detection of CAD. In addition, an attenuated HR response to exercise, a manifestation of chronotropic incompetence, may have independent diagnostic value for CAD.
Methods And Results:
The diagnostic value of adjusting the magnitude of ST-segment depression, the ST-segment (ST)/HR index, and the ST/HR slope for chronotropic response to exercise was assessed in 283 control subjects and 337 patients with CAD by dividing each ST measurement by the fraction of HR reserve achieved. At a matched specificity of 96%, ST-segment depression of > 160 microV identified CAD with a sensitivity of 52%, an ST/HR index of > 1.69 microV/bpm identified CAD with a sensitivity of 90%, and an ST/HR slope of > 2.96 microV/bpm identified CAD with a sensitivity of 88%. Adjustment for HR reserve improved the sensitivity of each method: adjusted ST-segment depression of > 176 had a sensitivity of 87% (P < .0001), an adjusted ST/HR index of > 2.14 had a sensitivity of 94% (P = .005), and an adjusted ST/HR slope of > 3.47 had a sensitivity of 93% (P = .0001). In addition, the 94% and 93% sensitivities of the adjusted ST/HR index and ST/HR slope were significantly greater than the 87% sensitivity of adjusted ST-segment depression (P < .0001).
Conclusions:
Correction for an attenuated HR response to exercise improves performance of the simple and HR-adjusted ST-segment depression criteria for the identification of CAD. These findings support assessment of the degree of chronotropic reserve in routine evaluation of the exercise ECG.