Diagnostic Testing for Microvascular Dysfunction

Non-Invasive Testing

The European Society of Cardiology recommends non-invasive testing for patients with suspected microvascular dysfunction, starting with quantitative assessment of coronary flow reserve (CFR) using PET, cardiac MRI perfusion imaging, or transthoracic Doppler echocardiography of the left anterior descending artery 1, 2
PET imaging is the preferred non-invasive reference standard for measuring myocardial blood flow reserve (MBFR), with a threshold of <2.5 indicating microvascular dysfunction 1, 2
Stress CMR perfusion imaging is recommended in patients with moderate to high pre-test likelihood of obstructive CAD to diagnose and quantify myocardial ischemia and estimate risk of major adverse cardiovascular events 1

Guidewire-based invasive coronary functional testing should be considered in patients with persistent symptoms but angiographically normal coronary arteries or moderate stenoses with preserved FFR/iFR, according to the European Heart Journal 3, 2
The standardized invasive assessment combines three components: basic coronary hemodynamic assessment, endothelial function testing, and microvascular resistance measurement 5
Coronary flow reserve (CFR) measured by thermodilution or Doppler flow velocity, with CFR <2.0-2.5 indicating microvascular dysfunction 3, 2, 5

CFR <2.0-2.5 (varies by measurement technique) indicates microvascular dysfunction 3, 2, 5
IMR ≥25 units indicates structural microvascular disease 3, 2, 5
HMR >2.5 mmHg/cm/s by Doppler assessment indicates microvascular dysfunction 5
PET MBFR <2.32 is associated with elevated hazard for major coronary events at 10-year follow-up, according to the European Heart Journal 6

Perform coronary CTA or invasive coronary angiography to exclude epicardial stenoses before non-invasive functional assessment 3, 4, 2
If high-quality PET is available, measure MBFR as reference standard 2
If CMR expertise is available, stress perfusion CMR for combined ischemia detection and CFR assessment 1

Microvascular dysfunction is more common in women than men, with overall prevalence of 41% in selected patients without obstructive CAD 1
The presence of microvascular dysfunction confers worse prognosis than originally recognized, with increased morbidity, mortality, and impaired quality of life 3, 2

Referral to a specialist with expertise in coronary microvascular disease and invasive coronary function testing is recommended because specialist-guided testing changes management in approximately 20% of patients and enables stratified medical therapy that significantly improves angina severity and quality of life, according to the European Heart Journal 6