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Reclassification of cardiovascular risk in patients with normal myocardial perfusion imaging using heart rate
Fahad M Iqbal1, Wael Al Jaroudi, Kumar Sanam
1Tulane University Heart and Vascular Institute, Tulane University, New Orleans, Louisiana, USA. fiqbal1@tulane.edu
Insights
A blunted heart rate response (HRR) to vasodilator stress indicates higher cardiac event risk in patients with normal myocardial perfusion imaging (MPI). Adding HRR to traditional risk scores improves patient reclassification for better cardiac event prediction.
Area of Science:
- Cardiology
- Nuclear Cardiology
- Preventive Cardiology
Background:
- Patients with normal vasodilator myocardial perfusion imaging (MPI) findings still face risks of future cardiac events.
- Traditional risk stratification models may not fully capture residual risk in these patients.
Purpose of the Study:
- To evaluate if heart rate response (HRR) to vasodilator stress improves risk classification in patients with normal vasodilator MPI.
- To assess the added value of HRR to the Adult Treatment Panel III (ATP III) framework for predicting cardiac events.
Main Methods:
- Retrospective analysis of 2,000 patients with normal regadenoson or adenosine MPI.
- Risk stratification using ATP III framework and patient stratification by HRR tertiles.
- All-cause mortality and cardiac death/nonfatal myocardial infarction (MI) were recorded up to 2 years post-MPI.
Main Results:
- Lower HRR was significantly associated with increased risk of mortality (HR 2.1) and cardiac death/nonfatal MI (HR 2.9).
- Patients in the highest HRR tertile demonstrated a low risk of events, regardless of ATP III category.
- HRR addition to ATP III categories yielded a net reclassification improvement of 18% for mortality and 22% for cardiac death/MI.
Conclusions:
- A blunted HRR to vasodilator stress is an independent predictor of adverse cardiac events and mortality in patients with normal vasodilator MPI.
- HRR significantly reclassifies patients, identifying those at truly low risk and those needing closer monitoring.
- HRR provides valuable prognostic information beyond traditional risk factors in patients with normal vasodilator MPI.
Abstract:
Previous studies have shown that patients with normal vasodilator myocardial perfusion imaging (MPI) findings remain at a greater risk of future cardiac events than patients with normal exercise MPI findings. The aim was to assess improvement in risk classification provided by the heart rate response (HRR) in patients with normal vasodilator MPI findings when added to traditional risk stratification. We retrospectively studied 2,000 patients with normal regadenoson or adenosine MPI findings. Risk stratification was performed using Adult Treatment Panel III framework. Patients were stratified by HRR (percentage of increase from baseline) into tertiles specific to each vasodilator. All-cause mortality and cardiac death/nonfatal myocardial infarction (MI) ≤2 years from the index MPI were recorded. During follow-up, 11.8% patients died and 2.7% patients experienced cardiac death/nonfatal MI in the adenosine and regadenoson groups, respectively. The patients who died had a greater Framingham risk score (12 ± 4 vs 11 ± 4, p = 0.009) and lower HRR (22 ± 16 vs 32 ± 21, p <0.0001). In an adjusted Cox model, the lowest tertile HRR was associated with an increased risk of mortality (hazard ratio 2.1) and cardiac death/nonfatal MI (hazard ratio 2.9; p <0.01). Patients in the highest HRR tertile, irrespective of the Adult Treatment Panel III category, were at low risk. When added to the Adult Treatment Panel III categories, the HRR resulted in net reclassification improvement in mortality of 18% and cardiac death/nonfatal MI of 22%. In conclusion, a blunted HRR to vasodilator stress was independently associated with an increased risk of cardiac events and overall mortality in patients with normal vasodilator MPI findings. The HRR correctly reclassified a substantial proportion of these patients in addition to the traditional risk classification models and identified patients with normal vasodilator MPI findings, who had a truly low risk of events.
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