What is the interpretation of a stress test showing a transient ischemic dilation (TID) ratio of 1.0, rest ejection fraction 57 %, peak stress ejection fraction 63 %, stress end‑diastolic volume 135 mL, stress end‑systolic volume 50 mL, rest end‑diastolic volume 118 mL, rest end‑systolic volume 51 mL, and a low myocardial blood‑flow stress‑rest reserve ratio?

Stress Test Interpretation: Reassuring Findings Despite TID Ratio of 1.0

This stress test demonstrates overall low-risk features with normal perfusion, preserved ejection fraction reserve, and a TID ratio of 1.0 that falls well within normal limits, indicating no significant transient ischemic dilation. The low myocardial blood flow reserve ratio is the primary concerning finding that warrants attention.

Key Findings Analysis

Transient Ischemic Dilation (TID) Assessment

• Your TID ratio of 1.0 is normal. The established threshold for abnormal TID in PET imaging is >1.13 1, and your value falls significantly below this cutoff
• Normal TID ratios range from 0.98 ± 0.06 in reference populations 1
• TID ratios ≥1.13-1.19 are associated with severe coronary disease, extensive ischemia, and worse outcomes 2, 1, 3
• Your TID ratio of 1.0 effectively excludes transient ischemic dilation as a high-risk marker

Ventricular Volume Changes

Your volume data reveals:

• Stress EDV (135 mL) vs Rest EDV (118 mL) = +17 mL increase
• Stress ESV (50 mL) vs Rest ESV (51 mL) = -1 mL (essentially unchanged)
• The modest EDV increase with stable ESV does not constitute pathologic transient dilation
• Normal stress response typically shows ΔEDV of 10.8 ± 11.5 mL 1, and your 17 mL increase is within expected range

Ejection Fraction Reserve

• Rest EF 57% → Stress EF 63% = +6% augmentation
• This represents preserved and appropriate EF reserve
• Normal EF reserve is approximately 5.0 ± 6.4% 1
• The ability to augment EF by ≥5% is reassuring and argues against severe ischemia 4
• Failure to augment EF by ≥10 percentage points is associated with ≥70% coronary stenosis 4, which you do not demonstrate

Primary Concern: Low Myocardial Blood Flow Reserve

The reduced myocardial blood flow stress-rest reserve ratio is the most significant abnormal finding and requires clinical correlation:

• Abnormal flow reserve can indicate:

  • Microvascular dysfunction (most common in absence of perfusion defects)
  • Balanced ischemia from multivessel disease
  • Diffuse atherosclerotic burden
  • Endothelial dysfunction

• Patients with abnormal TID typically show global myocardial flow reserve of 1.7 ± 0.6 compared to 2.1 ± 0.8 in normal TID patients 1

Risk Stratification

Overall risk profile: Low-to-intermediate based on:

✓ Favorable markers:

• Normal TID ratio (1.0)
• Preserved EF reserve (+6%)
• Adequate resting EF (57%)
• Appropriate stress EF response (63%)

✗ Concerning marker:

• Reduced myocardial blood flow reserve

Clinical Implications

The combination of normal perfusion parameters with reduced flow reserve suggests:

1. If perfusion imaging shows no defects: This pattern is consistent with microvascular dysfunction rather than obstructive coronary disease. TID in the absence of perfusion defects should be interpreted cautiously 5, and your normal TID ratio further supports this interpretation.

2. Prognostic considerations: Even with normal perfusion, reduced flow reserve may indicate increased cardiovascular risk requiring aggressive risk factor modification 2

3. Need for correlation: The interpretation must account for:

   • Clinical presentation and symptoms
   • Cardiovascular risk factors (diabetes, hypertension, hyperlipidemia)
   • Known coronary disease history
   • Presence/absence of regional perfusion defects

Recommended Clinical Approach

Immediate management:

• Optimize medical therapy for coronary risk factors
• Aggressive lipid management
• Blood pressure control
• Diabetes management if present

Further evaluation considerations:

• If symptomatic or high-risk features present: Consider coronary angiography to exclude balanced multivessel disease 6
• If asymptomatic with low clinical risk: Intensive medical management with surveillance
• Correlation with any available coronary CT angiography if performed

Critical Pitfalls to Avoid

⚠️ Do not over-interpret the TID ratio of 1.0 - this is definitively normal and should not drive aggressive intervention

⚠️ Do not dismiss the reduced flow reserve - this represents true pathophysiology requiring attention even without perfusion defects

⚠️ Consider balanced ischemia - in multivessel disease, perfusion may appear relatively normal while flow reserve is globally reduced 6

⚠️ Account for heart rate differences - though less relevant with your normal TID, significant heart rate differences between rest and stress can create apparent volume changes 5

The preserved ejection fraction reserve and normal TID ratio are reassuring markers that argue against high-grade obstructive disease, but the reduced flow reserve warrants aggressive medical management and clinical correlation with symptoms and risk factors.