Is a reduction in ejection fraction (EF) during the stress part of a stress test considered normal?

Reduction in Ejection Fraction During Stress Testing: Clinical Significance

A reduction in ejection fraction (EF) during the stress portion of a stress test can be abnormal and often indicates stress-induced myocardial ischemia, particularly when the decrease is 5% or greater from baseline. This finding should prompt further evaluation for coronary artery disease.

Physiological Basis and Normal Response

During normal exercise or pharmacological stress:

• Healthy myocardium typically demonstrates increased contractility
• EF should maintain or increase from baseline
• Wall motion and thickening should improve

Abnormal EF Response Patterns

Significant EF Reduction (≥5% decrease)

A decrease in EF during stress can occur due to several mechanisms:

• Stress-induced ischemia: The European Association of Nuclear Medicine and European Association of Cardiovascular Imaging guidelines specifically note that a decrease in EF during stress is associated with myocardial ischemia 1. In their example of an abnormal myocardial perfusion imaging (MPI) report, they highlight a case where "EF decreased significantly after exercise, and regional systolic function was reduced after exercise" as indicative of severe stress-induced ischemia.

• Afterload mismatch: In patients with left ventricular dysfunction, increased afterload during stress can cause EF to decrease even without ischemia 2. This is particularly relevant in cardiomyopathy patients, where an inverse relationship between changes in LV ejection fraction and systolic blood pressure during stress has been demonstrated.

• Extensive coronary disease: A stress-induced EF drop is often associated with severe or extensive coronary artery disease, especially when accompanied by regional wall motion abnormalities.

Clinical Significance by Magnitude

• 5% or greater decrease: Generally considered clinically significant and abnormal 3
• 10% or greater decrease: Strongly suggestive of severe coronary artery disease

Prognostic Implications

The prognostic significance of a stress-induced EF drop varies by patient population:

• Diabetic patients: A post-stress LVEF drop ≥5% is associated with lower event-free survival (hazard ratio 1.52) even after adjusting for clinical and perfusion data 3

• Normal baseline EF: In patients with normal baseline EF, lower peak stress cardiac power (which incorporates EF) is associated with increased mortality and heart failure risk 4

• Post-myocardial infarction: Patients who fail to recover EF by 3 months post-MI (remaining ≤35%) typically show lower EF during both baseline and stress echocardiography before discharge 5

Important Considerations

1. Context matters: The significance of EF drop depends on:

   • Baseline cardiac function
   • Type of stress (exercise vs. pharmacological)
   • Presence of other abnormal findings (perfusion defects, wall motion abnormalities)

2. Pharmacological stress differences: With regadenoson stress, a decrease in LVEF may be less predictive of severe coronary disease or adverse outcomes compared to exercise stress 6

3. Reporting standards: According to European guidelines, stress test reports should specifically document changes in EF from rest to stress, particularly when there is a significant decrease 1

Clinical Approach

When a stress-induced EF drop is observed:

1. Evaluate for accompanying perfusion defects or wall motion abnormalities
2. Consider the magnitude of the drop (≥5% is significant)
3. Assess the patient's baseline cardiac function and risk factors
4. In appropriate clinical contexts, consider coronary angiography for definitive evaluation

In summary, while some decrease in EF may occur in certain patient populations (like those with cardiomyopathy) due to afterload effects, a significant drop in EF during stress testing generally represents an abnormal finding that warrants further investigation.