Should a patient with an abnormal exercise stress test but a normal perfusion scan undergo a coronary computed tomography (CT) with heart flow?

Management of Abnormal Exercise Stress Test with Normal Perfusion Scan

Patients with abnormal exercise stress test but normal perfusion scan do not require coronary CT angiography with heart flow assessment as additional testing is unlikely to change management or improve outcomes. 1

Understanding the Discordant Results

When faced with an abnormal exercise stress test (EST) but normal myocardial perfusion scan, it's important to understand what this combination of findings means:

• A normal perfusion scan has excellent prognostic value, with subsequent cardiac death and myocardial infarction rates of <1% per year 1
• Normal results on stress myocardial perfusion scanning indicate such a low likelihood of significant coronary artery disease (CAD) that coronary arteriography is usually not indicated 1

Evidence-Based Approach

The American College of Physicians guidelines provide clear direction on this scenario:

1. Normal perfusion imaging results are highly predictive of excellent prognosis, even in patients with known coronary disease 1
2. Based on a synthesis of 16 studies involving 3594 patients, normal results on stress myocardial perfusion scanning indicate such a low likelihood of significant CAD that additional testing is not warranted 1

Exception to Consider

There is one important exception to note:

• Patients with high-risk treadmill scores and normal perfusion images may warrant additional evaluation 1
• In these specific cases, the high-risk exercise parameters may outweigh the reassurance of the normal perfusion study

Appropriate Next Steps

For most patients with this discordant finding:

• Reassure the patient about their excellent prognosis based on the normal perfusion scan
• Focus on cardiovascular risk factor modification
• Consider non-cardiac causes for exercise-related symptoms
• Clinical follow-up rather than additional cardiac imaging is appropriate

When Additional Testing Might Be Considered

Additional testing with coronary CT angiography might be considered only in very specific circumstances:

• Patients with high-risk Duke treadmill scores despite normal perfusion imaging 1
• Patients with persistent, concerning symptoms despite normal perfusion imaging
• Patients with strong clinical suspicion of CAD where the perfusion study may have had technical limitations

Avoiding Common Pitfalls

1. Overreliance on EST abnormalities: Exercise ECG has lower specificity than perfusion imaging and can produce false positives
2. Defensive testing cascade: Pursuing additional testing despite normal perfusion imaging often leads to unnecessary procedures without improving outcomes
3. Ignoring the strong negative predictive value: Normal perfusion studies have excellent negative predictive value for significant CAD and future cardiac events 1

The 2012 ACP/ACCF/AHA guidelines specifically recommend against using additional cardiac imaging modalities when initial appropriate testing has been performed and results are normal or low-risk 1.