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Updated: Jun 23, 2026
In Vivo Quantitative Assessment of Myocardial Structure, Function, Perfusion and Viability Using Cardiac Micro-computed Tomography
Published on: February 16, 2016
Vasodilator reserve in collateral-dependent myocardium as measured by positron emission tomography
E O McFalls1, L I Araujo, A Lammertsma
1Department of Cardiology, VA Hospital, University of Minnesota, Minneapolis 55417.
Insights
This study quantifies myocardial blood flow using positron emission tomography. It found that vasodilator reserve in collateral-dependent regions may not fully compensate for reduced blood flow, correlating with ischemia severity.
Area of Science:
- Cardiology
- Nuclear Medicine
- Physiology
Background:
- Myocardial blood flow (MBF) is crucial for cardiac function.
- Positron emission tomography (PET) with oxygen-15 labelled water allows accurate MBF quantification.
- Intramyocardial collateral blood flow plays a role in supplying blood to ischemic regions.
Purpose of the Study:
- To determine the vasodilator reserve in myocardium perfused solely by collateral blood flow.
- To investigate the correlation between relative flow reserve in collateral-dependent regions and exercise-induced ischemia.
Main Methods:
- Utilized PET with carbon-15 labelled carbon monoxide (C15O2) to trace water (H2(15)O).
- Employed rapid dynamic scanning and a two-compartment kinetic model for MBF quantification.
- Measured MBF at rest and during dipyridamole infusion in patients with occluded arteries and collateral flow, compared to normal volunteers.
Main Results:
- Resting MBF in collateral-dependent myocardium was comparable to normally perfused myocardium in patients and controls.
- Following dipyridamole, MBF increased significantly in controls but showed a blunted response in collateral-dependent regions of patients.
- Normal myocardial regions in patients also showed a slightly reduced hyperemic response compared to controls.
Conclusions:
- Vasodilator reserve in collateral-dependent myocardium is reduced compared to normal myocardium.
- This reduced vasodilator reserve may contribute to the degree of ischemia observed during exercise.
- PET imaging provides a valuable tool for assessing myocardial perfusion reserve in patients with coronary artery disease.
Abstract:
Myocardial blood flow can be accurately quantitated in patients using positron emission tomography and oxygen-15 labelled water. The purpose of this study was to determine the vasodilator reserve in myocardium completely perfused by intramyocardial collateral blood flow. We hypothesized that altered relative flow reserve in such regions would correlate with the degree of ischaemia observed in these patients during exercise. The technique involves the inhalation of the positron emitting tracer C15O2 which is converted to freely diffusible H2(15)O by the lung. With rapid dynamic scanning, arterial and regional myocardial tissue concentrations can be obtained and time activity curves generated. With a two-compartment kinetic model, myocardial blood flow can be accurately quantitated over a wide range of blood flows. Five patients with stable exertional angina and normal ventricular function studies and who had an occluded major epicardial artery which completely opacified via intramyocardial collateral blood flow were studied. Myocardial blood flow (MBF) was measured both at rest and following an infusion of intravenous dipyridamole (0.56 mg.kg-1) and the results were compared with measurements obtained from a group of eight normal volunteers. During resting conditions, MBF in the control group was 0.86 +/- 0.10 ml.g-1.min-1 and in the patient group was 0.99 +/- 0.10 ml.g-1.min-1 in normally perfused myocardium (ns) and 0.86 +/- 0.14 ml.g-1.min-1 in collateral-dependent myocardium (ns). Following dipyridamole, MBF increased to 3.58 +/- 0.89 ml.g-1.min-1 in the control group and to 2.97 +/- 0.94 ml.g-1.min-1 in the normal regions of the patients (ns).(ABSTRACT TRUNCATED AT 250 WORDS)
