Detecting Microvascular Dysfunction with Stress Echocardiography

Limitations of Standard Stress Echocardiography

Stress echocardiography has limited ability to detect microvascular dysfunction using standard wall motion analysis alone, but can assess microvascular function when enhanced with specific techniques, particularly Doppler coronary flow reserve measurement of the left anterior descending artery or contrast-enhanced myocardial perfusion imaging 1, 2
Regional wall thickening abnormalities (RWTA) as markers of ischemia may underestimate ischemia in patients with microvascular disease because RWTA only develops when perfusion abnormalities affect ≥10% of myocardium 2
Microvascular dysfunction often produces diffuse, subendocardial perfusion defects that don't reach the threshold required for RWTA to develop 2
Wall motion abnormalities require significant transmural ischemia, while microvascular disease primarily affects the subendocardium 2

The European Society of Cardiology (ESC) states that Doppler left anterior descending coronary artery flow reserve may be considered during stress echocardiography to improve risk stratification beyond wall motion and to assess microvascular function (Class IIb, Level B) 1, 3
Coronary flow velocity reserve (CFVR) provides independent prognostic value beyond wall motion abnormalities 4
The ESC recommends that myocardial perfusion using commercially available intravenous ultrasound contrast agents (microbubbles) is recommended during stress echocardiography to improve diagnostic accuracy and refine risk stratification beyond wall motion (Class I, Level B) 1, 3, 5
Contrast perfusion imaging improves sensitivity for detecting single-vessel and microvascular disease 4
The American Society of Echocardiography (ASE) gives contrast perfusion imaging a Class IIa recommendation 4

For patients with suspected coronary artery disease (CAD) and moderate-to-high pre-test probability (>15%-85%) of obstructive CAD, standard stress echo is appropriate for detecting epicardial disease 1, 3
If microvascular dysfunction is specifically suspected, stress echo with Doppler CFVR of LAD can be used to improve detection of microvascular dysfunction 1
The absence of wall motion abnormalities on standard stress echo does not exclude functionally significant microvascular disease, especially in diabetic and hypertensive patients who may have diffuse subendocardial ischemia below the detection threshold of wall motion analysis 2

The American College of Cardiology and the European Society of Cardiology recommend stress PET with myocardial blood flow reserve (MBFR) measurement as the preferred noninvasive test for detecting microvascular dysfunction, followed by stress CMR with MBFR, in patients with persistent chest pain and nonobstructive CAD 6, 7
The European Society of Cardiology notes that PET-CT myocardial perfusion imaging outperformed other functional imaging modalities in head-to-head comparisons, with a Class 2a recommendation 8, 9
PET provides quantitative absolute myocardial blood flow measurements during both rest and stress without increasing radiation exposure or imaging time, according to the European Heart Journal 8
MBFR <2.0 indicates microvascular dysfunction and independently predicts major adverse cardiovascular events, as reported by the Journal of the American College of Cardiology 10, 11
PET measurement of MBFR improves risk stratification particularly in women with suspected coronary microvascular dysfunction, with a moderate level of evidence 10, 11

The American Heart Association and the American College of Cardiology define microvascular dysfunction as MBFR <2.0, with a Class 2a recommendation 6, 10, 12
Impaired coronary flow reserve is defined as CFR <2.0 or <2.5, depending on the study, with a moderate level of evidence 6, 10
Structural microvascular dysfunction is defined as IMR ≥25, with a high level of evidence 6, 10

The American College of Cardiology recommends that patient populations at highest risk for coronary microvascular dysfunction, including women, those with diabetes, hypertension, and other insulin-resistant states, undergo stress testing with MBFR measurement, with a Class 2a recommendation 6, 13
The American Heart Association and the American College of Cardiology specifically note that PET measurement of MBFR improves risk stratification especially for women with nonobstructive CAD, with a moderate level of evidence 10, 11

The Journal of the American College of Cardiology recommends that test choice be guided by local availability and expertise, with a Class 2a recommendation 6, 10
When quantitative flow measurements are available, stress PET with MBFR is the first choice, followed by stress CMR with quantitative MBFR, and then stress echocardiography with CFVR, with a moderate level of evidence 6, 8, 10