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Relation among stenosis severity, myocardial blood flow, and flow reserve in patients with coronary artery disease
M Di Carli1, J Czernin, C K Hoh
1Department of Molecular and Medical Pharmacology, UCLA School of Medicine.
Insights
Positron emission tomography (PET) can non-invasively assess coronary artery disease by measuring myocardial blood flow and flow reserve. This technique accurately correlates with stenosis severity, helping define the functional significance of intermediate coronary lesions.
Area of Science:
- Cardiology
- Nuclear Medicine
- Medical Imaging
Background:
- Coronary arteriography is the standard for evaluating coronary stenosis severity.
- Determining the functional significance of intermediate-grade lesions from angiography alone is challenging.
- This study investigates the relationship between myocardial blood flow/flow reserve (measured by PET) and angiographic stenosis severity.
Purpose of the Study:
- To determine the correlation between myocardial blood flow and flow reserve measured by PET and percent area stenosis on quantitative coronary arteriography.
- To assess the utility of PET in differentiating the physiological significance of intermediate coronary lesions.
Main Methods:
- 28 subjects (18 with coronary artery disease, 10 healthy volunteers) underwent dynamic N-13 ammonia PET imaging at rest and after dipyridamole.
- Coronary arteriograms were analyzed for percent cross-sectional area stenosis.
- Quantitative PET measurements of myocardial blood flow and flow reserve were obtained.
Main Results:
- Myocardial blood flow and flow reserve were similar between patients and controls at rest and after dipyridamole.
- PET-derived hyperemic blood flow, flow reserve, and minimal coronary resistance were inversely and nonlinearly correlated with percent area stenosis.
- PET successfully differentiated the flow reserve of intermediate coronary lesions (50%-70% vs. 70%-90% stenosis).
Conclusions:
- Non-invasive PET measurements of myocardial blood flow and flow reserve are inversely related to stenosis severity in coronary artery disease.
- PET can detect differential flow reserve in intermediate coronary lesions, aiding in the assessment of functional importance.
- PET offers a valuable tool for defining the physiological significance of coronary stenosis.
Background:
Coronary arteriography is considered the "gold standard" for evaluating the severity of a coronary stenosis. Because the resistance to blood flow through a stenotic lesion depends on a number of lesion characteristics, the physiological significance of coronary lesions of intermediate severity is often difficult to determine from angiography alone. This study of patients with coronary artery disease seeks to determine the relation between myocardial blood flow and flow reserve measured by positron emission tomography (PET) and the percent area stenosis on quantitative coronary arteriography.
Methods And Results:
We studied 28 subjects: 18 patients with coronary artery disease (66 +/- 8 years) and 10 age-matched healthy volunteers (64 +/- 13 years) with dynamic N-13 ammonia PET imaging at rest and after dipyridamole (0.56 mg/kg). The percent cross-sectional area stenosis was quantified on the coronary arteriograms as described by Brown et al. In the 18 patients, a total of 41 non-infarct-related coronary vessels were analyzed. Myocardial blood flows in normal regions of patients with coronary artery disease were not different than those in healthy volunteers, both at rest and after dipyridamole. As a result, the myocardial flow reserve was also similar in both groups (2.4 +/- 0.4 versus 2.6 +/- 0.7, respectively; P = NS). Quantitative PET estimates of hyperemic blood flow (r = .81, P < .00001), flow reserve (r = .78, P < .00001), and an index of the "minimal coronary resistance" (r = .78, P < .00001) were inversely and nonlinearly correlated with the percent area stenosis on angiography. Of note, PET estimates of myocardial flow reserve successfully differentiated coronary lesions of intermediate severity (50% to 70% and 70% to 90%; 2.4 +/- 0.4 versus 1.8 +/- 0.5, respectively; P = .04).
Conclusions:
In patients with coronary artery disease, non-invasive measurements of myocardial blood flow and flow reserve by PET are inversely and nonlinearly related to stenosis severity as defined by quantitative angiography. Importantly, coronary lesions of intermediate severity have a differential flow reserve that decreases as stenosis increases that can be detected noninvasively by PET, thus allowing better definition of the functional importance of known coronary stenosis.