What is the next step in management for a patient with an abnormal stress test and symptoms of shortness of breath?

Management Following Abnormal Stress Test with Normal Myocardial Perfusion Scan

Direct Recommendation

This patient requires no further cardiac testing or invasive evaluation, and management should focus on optimizing guideline-directed medical therapy for coronary artery disease risk factors, with reassurance that the normal myocardial perfusion scan effectively rules out obstructive coronary disease as the cause of her symptoms. 1, 2

Clinical Reasoning and Evidence Synthesis

The Diagnostic Sequence is Complete

The patient underwent an appropriate diagnostic cascade that has now reached a definitive conclusion:

• Initial abnormal stress test showed ST-segment depression suggestive of ischemia, prompting appropriate concern and further evaluation 1
• Emergency department evaluation appropriately ruled out acute coronary syndrome (unstable angina/NSTEMI) 1
• Nuclear myocardial perfusion imaging definitively showed no evidence of scar or ischemia, with normal left ventricular function (LVEF 64%) 1, 2

The normal perfusion scan is the decisive study here. The high negative predictive value of myocardial perfusion imaging means that obstructive coronary artery disease causing her symptoms is effectively excluded 1, 2. The ST-segment changes on the initial stress test represent a false positive result, which occurs in approximately 10-30% of stress ECGs, particularly in women 2.

Why No Further Cardiac Testing is Needed

According to ACC/AHA guidelines, when a patient undergoes stress testing as part of a conservative strategy and the imaging study (in this case, nuclear perfusion scan) is normal, the patient is classified as low risk and no further cardiac evaluation is warranted 1, 2. The guidelines explicitly state that if after stress testing the patient is classified as low risk, preparation for discharge with medical therapy should proceed 1.

Alternative Explanations for Symptoms

The patient's shortness of breath episodes were associated with sinus rhythm and borderline sinus tachycardia on the ZIO monitor, not with ischemia 3. This pattern suggests alternative etiologies that should now be considered:

• Pulmonary causes: Undiagnosed COPD or other pulmonary disease is highly prevalent (up to 81% in one study) among patients with shortness of breath referred for cardiac stress testing who have normal cardiac evaluations 4
• Diastolic dysfunction/HFpEF: Although her LVEF is normal at 64%, heart failure with preserved ejection fraction can present with exertional dyspnea 5
• Deconditioning or chronotropic insufficiency: The ZIO showed sinus rates ranging 50-129 bpm, which may indicate inadequate heart rate response to exertion 3
• Anxiety/hyperventilation: Should be considered after excluding organic causes 1

Specific Management Plan

Immediate actions:

• Continue aspirin indefinitely for cardiovascular risk reduction 1
• Optimize management of cardiovascular risk factors (hypertension, hyperlipidemia, diabetes if present) 1
• Discontinue any anticoagulation that was started during the acute evaluation 1

Further evaluation for dyspnea:

• Pulmonary function testing (spirometry) should be the next diagnostic step, given the high prevalence of undiagnosed COPD in this population 4
• Consider chest X-ray if not recently performed to evaluate for pulmonary pathology 3
• If pulmonary workup is negative, consider exercise stress echocardiography with diastolic parameters (E/e' ratio) to evaluate for HFpEF, which can cause exertional dyspnea with normal systolic function 3, 5

Regarding the arrhythmias on ZIO monitor:

• The rare PACs, PVCs (<1% burden), and brief runs of SVT (maximum 8 beats) are clinically insignificant and do not require specific treatment or further evaluation 1
• These findings are common in the general population and are not associated with adverse outcomes at this frequency 1

Critical Pitfalls to Avoid

Do not proceed to coronary angiography. The normal myocardial perfusion scan has definitively excluded obstructive coronary disease, and invasive testing would expose the patient to unnecessary risk without benefit 1, 2. Guidelines explicitly recommend against further cardiac testing when imaging stress tests are normal in this clinical scenario 2.

Do not attribute all symptoms to cardiac causes. The temporal association of her shortness of breath with sinus rhythm (not ischemia) on the ZIO monitor strongly suggests a non-cardiac etiology 3. Failing to pursue alternative diagnoses, particularly pulmonary disease, would be a significant oversight 4.

Do not dismiss the patient without addressing her symptoms. While cardiac disease is excluded, her dyspnea requires explanation and management. A systematic evaluation for pulmonary disease, HFpEF, and deconditioning should follow 3, 4, 5.

Do not continue dual antiplatelet therapy or anticoagulation. Since acute coronary syndrome was ruled out and no intervention was performed, continuing these medications beyond aspirin alone would increase bleeding risk without benefit 1.