High-frequency QRS analysis improves the specificity of exercise ECG testing in women referred for angiography
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BACKGROUND: Exercise ECG testing in women for the diagnosis of coronary artery disease (CAD) has a higher false-positive rate compared to men. Consequently, women referred for coronary angiography following a positive exercise test often have normal coronary arteries or non-obstructive lesions. Analysis of the high-frequency components of the QRS complexes (HFQRS) has been reported to provide a sensitive means of detecting myocardial ischemia, independent of gender. The aim of the present study was to prospectively test the diagnostic performance of HFQRS and conventional exercise ECG in detecting stress-induced ischemia in women referred for coronary angiography. METHODS: The study included 113 female patients (age 64 ± 9 years) referred for non-urgent angiography. Patients performed a symptom-limited treadmill exercise test prior to angiography. High-resolution ECG was acquired during the test and used for both HFQRS and conventional ST-segment analyses. HFQRS diagnosis was determined by computerized analysis, measuring the stress-induced reduction in HFQRS intensity. The diagnostic performance of HFQRS, ST-segment analysis and clinical interpretation of the exercise test were compared, using angiography as a gold standard. RESULTS: HFQRS provided sensitivity of 70% and specificity of 80% for detection of angiographically significant coronary obstruction (≥ 70% stenosis in a single vessel or ≥ 50% in the left main artery). HFQRS was more specific than exercise ECG test (80% vs. 55%, P<.005), as well as more accurate (76% vs. 62%, P<.01). The number of ECG leads with ischemic HFQRS response correlated with the severity of CAD. HFQRS was highly specific (93%) in patients who achieved their age-predicted target heart rate, and retained its diagnostic accuracy in subgroups of patients with resting ECG abnormalities or inconclusive exercise ECG. CONCLUSIONS: HFQRS analysis, as an adjunct technology to exercise stress testing, may improve the diagnostic value of the ECG, and reduce the number of unnecessary imaging and invasive procedures.
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