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Utility of myocardial perfusion imaging in patients with low-risk treadmill scores
Indu G Poornima1, Todd D Miller, Timothy F Christian
1Division of Cardiovascular Diseases and Department of Internal Medicine, Mayo Clinic and Mayo Foundation, Rochester, Minnesota, USA
Insights
A clinical score (CS) can identify patients with low-risk Duke treadmill scores who need myocardial perfusion imaging for risk stratification. High CS in low-risk Duke treadmill score patients indicates higher cardiac mortality risk.
Area of Science:
- Cardiology
- Diagnostic Imaging
- Risk Stratification
Background:
- Current guidelines recommend exercise tests without imaging for initial cardiac risk assessment.
- Myocardial perfusion imaging (MPI) is considered for patients with higher risk.
- The utility of MPI in low-risk Duke treadmill score patients needs further clarification.
Purpose of the Study:
- To evaluate if a clinical score (CS) can identify low-risk Duke treadmill score patients who benefit from MPI.
- To determine the prognostic value of MPI in this patient group.
Main Methods:
- 1,461 symptomatic patients with low-risk Duke treadmill scores underwent MPI.
- A clinical score (CS) was calculated based on typical angina, prior myocardial infarction, diabetes, insulin use, male gender, and age.
- Patients were categorized into high-risk (CS ≥5) or low-risk (CS <5) groups.
Main Results:
- High-risk scans were more frequent in patients with a high CS (26.4% vs. 9.5%).
- Both CS and global stress score (GSS) independently predicted cardiac death.
- In low CS patients, 7-year cardiac survival was excellent (99%) regardless of GSS; high CS patients had lower survival (92%), varying with GSS.
Conclusions:
- MPI has limited prognostic value in low-risk Duke treadmill score patients with low clinical risk.
- MPI provides independent prognostic value in low-risk Duke treadmill score patients with high clinical risk, who have significant annual cardiac mortality (>1%).
Objectives:
The purpose of this study was to determine whether a previously validated clinical score (CS) could identify patients with a low-risk Duke treadmill score who had a higher risk of adverse events and, therefore, in whom myocardial perfusion imaging would be valuable for risk stratification.
Background:
Current American College of Cardiology/American Heart Association guidelines recommend using a standard exercise test without imaging as the initial test in patients who have an interpretable electrocardiogram and are able to exercise.
Method:
We studied 1,461 symptomatic patients with low-risk Duke treadmill scores (> or =5) who underwent myocardial perfusion imaging. The CS was derived by assigning one point to each of the following variables: typical angina, history of myocardial infarction, diabetes, insulin use, male gender, and each decade of age over 40 years. A CS cutoff > or =5 or <5 was used to categorize patients as high risk (n = 303 [21%]) or low risk (n = 1,158 [79%]). Perfusion scans were categorized as low, intermediate, or high risk on the basis of the global stress score (GSS).
Results:
High-risk scans were more common in patients with a high-risk CS (26.4% vs. 9.5%, p < 0.0001). The CS and GSS were significant independent predictors of cardiac death. However, in patients with a low CS, seven-year cardiac survival was excellent, regardless of the GSS (99% for normal scans, 99% for mildly abnormal scans, and 99% for severely abnormal scans). In contrast, patients with a high CS had a lower seven-year survival rate (92%), which varied with GSS (94% for normal scans, 94% for mildly abnormal scans, and 84% for severely abnormal scans; p < 0.001).
Conclusions:
In symptomatic patients with low-risk Duke treadmill scores and low clinical risk, myocardial perfusion imaging is of limited prognostic value. In patients with low-risk Duke treadmill scores and high clinical risk, annual cardiac mortality (>1%) is not low, and myocardial perfusion imaging has independent prognostic value.
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