Abstract 16611: High Frequency QRS Analysis Improves the Diagnostic Accuracy of Exercise Stress Electrocardiography Compared to ST-Analysis for the Detection of Myocardial Ischemia
Background: The utilization of myocardial perfusion imaging (MPI) for ischemia identification leads to increased expense and radiation exposure but is driven by the limited diagnostic accuracy of exercise stress electrocardiography. We tested the hypothesis that a novel marker of ischemia identified in the high frequency portion of the QRS signal (HF-QRS) during stress testing improves diagnostic accuracy compared to exercise ST-depression.
Methods: We analyzed 62 consecutive patients undergoing exercise MPI and HF-QRS analysis to assess myocardial ischemia. The HF-QRS was determined within a bandwidth of 150 -250 Hz. A 50% relative reduction and ≥ 1 µV drop in the HF-QRS signal in ≥3 leads and ≥1mm ST-depression were the criteria for HF-QRS and stress ECG positivity, respectively. Quantitative, gated-SPECT MPI was performed according to standard protocols. Sensitivities, specificities and overall diagnostic accuracy were compared using McNemar's test and the area under the ROC curve.
Results: Eight patients were excluded due to a noisy HF-QRS signal, leaving 54 evaluable patients. The mean cohort age was 57.9 +/− 11.7 years and 70.4% were male. This population represented a typical SPECT MPI referral cohort with 72.2% hypertension, 68.5% hyperlipidemia, 20.4% diabetes mellitus, 33.3% prior MI and 35.2% prior revascularization. On SPECT MPI, 8 patients had myocardial ischemia (14.8%). The sensitivity of the HF-QRS to detect ischemia was 75 %, and the specificity was 89.1% vs. 25% and 84.8% respectively for ST-depression (p <001). The diagnostic accuracies were 0.82 (95% CI 0.69-0.91) for HF-QRS and 0.55 (95% CI 0.41-0.69) for ST-depression (P= 0.008).
Conclusion: In our cohort, HF-QRS analysis had a significantly improved diagnostic accuracy to detect ischemia when compared to ST-depression. HF-QRS analysis may enhance the reliability of CAD diagnosis without more expensive diagnostic imaging. Studies in larger populations are warranted.
- © 2011 by American Heart Association, Inc.