Understanding Mild Decrease in MBFR on RCA Territory on PET CT

Introduction to MBFR and Its Clinical Significance

The American College of Cardiology states that MBFR (Myocardial Blood Flow Reserve) is a quantitative measure obtained during PET imaging that reflects the ratio of stress to rest absolute myocardial blood flow, providing information about coronary vasodilatory capacity 1, 2
Normal MBFR is generally considered to be ≥2.0, while values <2.0 suggest impaired coronary flow reserve 1, 2
Reduced MBFR reflects abnormalities of flow within the epicardial coronary arteries, microvasculature, or both, and independently predicts risk of major coronary artery disease events 1, 3

A mild decrease in MBFR specifically in the RCA territory suggests potential disease in the distal segments of the RCA that may not be visible on conventional angiography 1
Possible early coronary microvascular dysfunction in the territory supplied by the RCA is indicated by a mild decrease in MBFR in the RCA territory 4, 5
The American Heart Association and American College of Cardiology guidelines recommend incorporating MBFR information into risk assessment for patients with chronic coronary disease 6, 2

The American College of Cardiology recommends optimization of guideline-directed medical therapy for patients with mild reductions in MBFR (between 1.8-2.0) 6, 2
Clinical correlation with symptoms is essential, as the significance of reduced MBFR should be interpreted in the context of the patient's clinical presentation 1, 7
The American College of Cardiology suggests that patients with reduced MBFR (<2.0) have higher risk of adverse cardiovascular events compared to those with normal MBFR, although this specific fact is not directly cited, the general concept is supported by 6, 2

The finding should be interpreted in the context of patient symptoms (presence/absence of angina) and other cardiac risk factors 1, 6, 2
When MBFR is mildly reduced but perfusion appears normal, it may represent early disease that has not yet progressed to cause visible perfusion defects 5
Microvascular dysfunction, especially in women, may be indicated by a mild decrease in MBFR in the RCA territory 1, 5

Clinical correlation with symptoms and risk factors is necessary 6, 1
Consider invasive coronary angiography if patient has significant symptoms despite medical therapy or if there are other high-risk features present 6, 7
If angiography is performed, consider assessment of fractional flow reserve (FFR) for intermediate lesions 1, 4
Optimize medical therapy for coronary artery disease 6, 2