What is the recommended diagnostic and therapeutic approach for a patient with confirmed ischemia with no obstructive coronary arteries (INOCA)?

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INOCA: Diagnostic and Therapeutic Approach

For patients with confirmed INOCA, perform invasive coronary function testing (CFT) to identify the underlying mechanism, then initiate mechanism-specific medical therapy guided by CFT results to improve symptoms and quality of life. 1

Diagnostic Strategy

Initial Recognition

INOCA occurs in approximately 50% of patients undergoing coronary angiography for chest pain, more commonly in women. 1 The condition encompasses several distinct mechanisms:

  • Coronary microvascular dysfunction (CMD)
  • Epicardial coronary vasospasm
  • Myocardial bridging
  • Diffuse atherosclerosis
  • Combination of above disorders 1

Invasive Coronary Function Testing (Class I Recommendation)

The 2024 ESC guidelines provide a Class I recommendation for availability of invasive CFT at the time of initial coronary angiography when mechanisms are uncertain. 1 This represents a paradigm shift from previous approaches.

CFT should include:

  • Adenosine testing to assess coronary flow reserve (CFR) and index of microcirculatory resistance (IMR)
  • Acetylcholine provocation testing to identify endothelial dysfunction and vasospasm 2

This comprehensive assessment is critical because non-invasive alternatives have limited diagnostic accuracy for identifying coronary vascular dysfunction, and standard angiography cannot establish the diagnosis. 2

Mechanism-Specific Treatment Approach

Universal Recommendations for All INOCA Patients

Medical therapy should be chosen based on invasive CFT results (Class IIa, Level A). 1 Additionally, all patients require:

  • Cardiovascular risk factor management (hypertension, dyslipidemia, diabetes)
  • Lifestyle modifications: healthy diet, exercise, stress management, weight management, smoking cessation
  • Goal: Improve symptoms and quality of life 1

CMD with Reduced CFR and/or Elevated IMR

First-line options (Class IIa, Level B):

  • Beta-blockers (strongest recommendation)
  • Calcium channel blockers
  • Ranolazine
  • Trimetazidine
  • Ivabradine

ACE inhibitors are also recommended based on data showing symptom improvement in ANOCA due to CMD with reduced CFR. 1

Critical caveat: Avoid combining ivabradine with diltiazem or verapamil. 1

Endothelial Dysfunction

ACE inhibition (Class IIa, Level B) for symptom control. 1

Vasospastic Angina

This requires the most aggressive approach given risk of potentially fatal complications:

Primary therapy (Class I, Level A):

  • Calcium channel blockers - may require combination of dihydropyridine and non-dihydropyridine CCBs
  • Unusually high doses may be necessary: up to 400-960 mg/day of diltiazem for symptom relief 1

Additional options (Class IIa, Level B):

  • Nitrates
  • Nicorandil

Combination medical therapy (Class IIb, Level B) may be required for refractory cases. 1

Goals: Symptom control, prevention of ischemia, and prevention of potentially fatal complications. 1

When to Pursue CFT

Invasive CFT is indicated in three scenarios:

  1. At time of initial coronary angiography when mechanisms are uncertain after non-invasive testing
  2. In patients with established INOCA/ANOCA who have persistent symptoms despite medical therapy
  3. In patients with poor quality of life despite treatment 1

The safety profile of CFT is comparable to regular coronary angiography with physiological measurements. 2

Prognostic Implications

INOCA is not a benign condition. Despite absence of obstructive CAD, these patients have:

  • Increased risk of all-cause mortality
  • Increased adverse cardiovascular events
  • Recurrent angina
  • Healthcare costs rivaling obstructive CAD due to repeat testing and catheterizations 3

Invasive CFT allows for risk stratification and guides therapy that improves both symptoms and quality of life. 4

Critical Pitfalls to Avoid

  1. Do not dismiss patients as having "non-cardiac chest pain" without comprehensive evaluation - up to 89% have identifiable coronary vascular dysfunction 2

  2. Do not rely solely on non-invasive testing - it has limited diagnostic accuracy for CMD 2

  3. Do not use empiric therapy without mechanism identification - targeted therapy based on CFT results is superior 1

  4. Do not underestimate medication dosing requirements - vasospastic angina may require unusually high CCB doses 1

Adjunctive Therapies

Cardiac rehabilitation should be considered - small studies demonstrate improvements in endothelial function, myocardial perfusion, exercise capacity, and quality of life. 5 Programs may need tailoring for INOCA patients, who are predominantly women with non-atherosclerotic mechanisms.

Emerging therapies (Rho-kinase inhibitors, endothelin receptor antagonists, anti-inflammatory agents) require further study before routine use. 1, 6

References

2
Research

Diagnostic approach in patients with angina and no obstructive coronary artery disease: emphasising the role of the coronary function test.

Netherlands heart journal : monthly journal of the Netherlands Society of Cardiology and the Netherlands Heart Foundation, 2021

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