What do coronary catheterization results indicating a coronary flow reserve (CFR) of 1.6, renal resistive reserve (RRR) of 1.5, and index of microvascular resistance (IMR) of 17, with acetylcholine (ACh)-stimulated CFR of 1.1 and ACh-stimulated IMR of 29, signify for a patient's coronary artery disease management?

Coronary Catheterization Results Interpretation: Microvascular Dysfunction with Vasospastic Component

These results indicate coronary microvascular dysfunction (CMD) with a significant vasospastic component, requiring medical therapy with beta-blockers or ivabradine as first-line agents, combined with ACE inhibitors/ARBs and high-intensity statins, while absolutely avoiding calcium channel blockers due to the vasospastic features. 1, 2

Understanding Your Specific Values

Baseline Adenosine Testing (Endothelium-Independent)

• CFR 1.6: This is abnormal, as normal CFR should be ≥2.0-2.7 3. Your value indicates impaired coronary flow reserve affecting both epicardial and microvascular circulation 3
• RRR 1.5: This confirms microvascular dysfunction, as the European Society of Cardiology defines abnormal RRR as <2.0 1
• IMR 17: This is normal (abnormal is ≥25 units), suggesting the microvascular dysfunction is primarily functional rather than structural 1

Acetylcholine Testing (Endothelium-Dependent)

• ACh-CFR 1.1: This is severely abnormal (optimal threshold is ≥1.5) and indicates significant endothelial dysfunction 4
• ACh-IMR 29: This increased from 17 to 29 with acetylcholine, indicating microvascular spasm or vasospastic dysfunction 4, 5

Clinical Significance and Prognosis

The combination of reduced CFR and abnormal acetylcholine response places you at increased cardiovascular risk:

• Patients with CMD have a 9.4% rate of death or myocardial infarction by 4 years, even without obstructive coronary disease 1
• The severely reduced ACh-CFR of 1.1 (below the 1.5 threshold) combined with elevated ACh-IMR suggests an 83% likelihood of myocardial ischemia 4
• Impaired coronary flow reserve is associated with elevated hazard for major coronary events at 10-year follow-up 1

Diagnostic Algorithm Interpretation

Your results follow this diagnostic pattern:

1. Abnormal CFR (1.6 < 2.0) prompted acetylcholine testing 4
2. Severely abnormal ACh-CFR (1.1 < 1.5) confirms endothelial dysfunction 4
3. Rising IMR with acetylcholine (17→29) indicates vasospastic component 4, 5
4. Normal baseline IMR (<25) suggests functional rather than structural microvascular disease 1

Specific Treatment Recommendations

First-Line Antianginal Therapy

Beta-blockers are the recommended first-line treatment:

• Target resting heart rate of 55-60 bpm with bisoprolol or nebivolol 1, 2
• Ivabradine may be superior to bisoprolol for coronary collateral flow and coronary flow reserve 1
• Beta-blockers work by slowing heart rate, increasing diastolic time and coronary perfusion, which is particularly important given your microvascular dysfunction 2

Critical Contraindication Warning

Calcium channel blockers are absolutely contraindicated in your case:

• The rising IMR with acetylcholine (17→29) indicates vasospastic features 4, 5
• Beta-blockers could theoretically worsen vasospasm by leaving α-mediated vasoconstriction unopposed, but the American Heart Association and European Society of Cardiology still recommend them as first-line for CMD with your pattern 2
• Non-dihydropyridine calcium channel blockers (diltiazem, verapamil) should be avoided due to additive negative chronotropic effects if combined with beta-blockers 2

Baseline Cardiovascular Protection

All patients with your RRR of 1.5 require:

• ACE inhibitors or ARBs to improve endothelium-dependent vasodilation 1, 2
• High-intensity statin therapy 1
• Aspirin 1

Refractory Symptoms Management

If symptoms persist despite beta-blocker therapy:

• Add ranolazine or nicorandil for refractory microvascular spasm symptoms 2
• These can be combined with ACE inhibitors safely 2

Key Clinical Pitfalls to Avoid

Common errors in interpreting these results:

• Do not assume normal epicardial arteries mean no ischemia—your severely reduced ACh-CFR indicates 83% likelihood of ischemia despite nonobstructive disease 4
• Do not rely on CFR alone (1.6) without acetylcholine testing—53% of patients with normal CFR still have abnormal ACh-CFR, and you fall into the category with both abnormal 4
• Do not dismiss the rising IMR with acetylcholine (17→29) as insignificant—this indicates active vasospastic dysfunction requiring specific management 4, 5
• CFR is influenced by hemodynamics: tachycardia reduces CFR by 10% for each 15-beat increase in heart rate, so rate control is essential 3