What does a moderately to severely dilated left ventricular (LV) cavity under stress in a myocardial perfusion study indicate?

Moderately to Severely Dilated Left Ventricular Cavity Under Stress: Implications and Management

A moderately to severely dilated left ventricular (LV) cavity during stress in a myocardial perfusion study is a high-risk finding that strongly suggests severe and extensive coronary artery disease, carrying a significant risk of adverse cardiac events including death and myocardial infarction.

Understanding LV Cavity Dilation During Stress

Transient ischemic dilation (TID) of the left ventricle during stress testing is a critical finding that requires prompt evaluation:

• Definition: Enlargement of the LV cavity during stress compared to rest images
• Mechanism: Occurs due to subendocardial ischemia causing reduced contractility and apparent cavity enlargement
• Significance: Listed as a high-risk finding in major cardiovascular guidelines 1

Clinical Significance

According to the ACC/AHA guidelines, stress-induced LV dilation is classified as a high-risk finding that carries >3% annual risk of death or myocardial infarction 1. This finding is particularly concerning because:

• It suggests diffuse subendocardial ischemia, often indicating multivessel coronary artery disease
• It correlates with severe and extensive coronary artery disease 2
• It predicts adverse cardiac outcomes with a high event rate (19.7% per year) 2
• It may occur even when perfusion defects appear relatively modest 3

Associated Findings to Evaluate

When LV cavity appears moderately to severely dilated during stress, look for other high-risk markers:

• Perfusion abnormalities: Assess for stress-induced perfusion defects in multiple coronary territories 1
• Wall motion abnormalities: Check for stress-induced wall motion abnormalities in ≥2 segments 1
• LV function: Evaluate for severe stress-induced LV dysfunction (peak exercise LVEF <45%) 1
• Other high-risk markers: Look for increased lung uptake of tracer and ST-segment depression 3

Management Recommendations

Based on the high-risk nature of this finding:

1. Urgent cardiology consultation is warranted
2. Coronary angiography should be considered to define coronary anatomy 1
3. Risk stratification should be completed promptly
4. Aggressive medical therapy should be initiated while awaiting further evaluation

Risk Stratification Algorithm

1. Confirm finding: Ensure technical factors aren't causing apparent dilation
2. Assess for other high-risk features:
   • Multiple perfusion defects
   • Wall motion abnormalities
   • Reduced LVEF
   • Clinical symptoms during stress
3. Determine risk level:
   • High risk: Multiple high-risk features present
   • Very high risk: Symptoms plus multiple high-risk features

Pitfalls and Caveats

• Technical factors: Ensure the finding isn't due to technical artifacts or patient positioning
• False positives: Can occur with certain medications, left bundle branch block, or cardiomyopathies
• Don't miss subtle signs: Even with minimal perfusion defects, TID remains a high-risk marker 3
• Women: May have smaller ventricles at baseline; relative changes may be more important than absolute measurements

Conclusion

Moderately to severely dilated LV cavity during stress represents a serious finding that warrants prompt evaluation. The European Association of Nuclear Medicine and European Association of Cardiovascular Imaging emphasize the importance of reporting LV cavity dimensions during stress testing 1. This finding should trigger a cardiology referral for consideration of coronary angiography due to its strong association with severe coronary artery disease and adverse outcomes.