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Updated: Aug 12, 2026
In Vivo Quantitative Assessment of Myocardial Structure, Function, Perfusion and Viability Using Cardiac Micro-computed Tomography
Published on: February 16, 2016
Relation between myocardial oxygen consumption and myocardial blood volume: a study using myocardial contrast
D Elizabeth Le1, Jian-Ping Bin, Matthew P Coggins
1Cardiovascular Imaging Center, Cardiovascular Division, School of Medicine, University of Virginia Medical Center, Charlottesville, VA 22908, USA.
Insights
Myocardial blood volume (MBV) increases with coronary blood flow (CBF) only when myocardial oxygen consumption (MVO2) rises, indicating capillary recruitment in regulating blood flow. Lack of MBV increase during dobutamine stress may signal coronary issues.
Area of Science:
- Cardiovascular Physiology
- Echocardiography
- Myocardial Perfusion Imaging
Background:
- Myocardial blood volume (MBV) represents blood in the heart's vessels, primarily capillaries.
- Myocardial contrast echocardiography (MCE) is a method for in vivo MBV measurement.
- Previous studies suggest MBV doesn't increase with coronary blood flow (CBF) if myocardial oxygen consumption (MVO2) remains constant.
Purpose of the Study:
- To test the hypothesis that MBV increases when elevated CBF is coupled with increased MVO2.
- To investigate the role of capillary recruitment in regulating myocardial blood flow under varying physiological conditions.
Main Methods:
- Eighteen dogs underwent atrioventricular node ablation and dual-chamber pacing.
- Group 1: Heart rate varied from 50-150 bpm.
- Group 2: Dobutamine infusion (5-40 microg/kg/min) at constant heart rate; MVO2, CBF, and MCE were measured throughout.
Main Results:
- Inotropic stimulation (dobutamine) increased MVO2 more significantly than chronotropic stimulation (heart rate changes).
- MBV fraction and MCE-derived myocardial blood flow significantly increased with MVO2 during dobutamine infusion (P < .05 and P < .001).
- MBV and MCE-derived myocardial blood flow remained unchanged when only heart rate was increased.
Conclusions:
- Increased MVO2, when substantial, leads to increased CBF and myocardial blood flow partly through MBV elevation.
- Capillary recruitment is crucial for the physiological regulation of CBF.
- A failure of MBV to increase during dobutamine stress may indicate coronary stenosis or microvascular disease.
Abstract:
Myocardial blood volume (MBV) is the volume of blood residing in myocardial vessels, 90% of which is in capillaries. MBV can be measured in vivo using myocardial contrast echocardiography (MCE). It has been shown that when increases in coronary blood flow (CBF) are not associated with increase in myocardial oxygen consumption (MVO(2)), MBV does not increase. We hypothesized that MBV would increase when increases in CBF are associated with an increase in MVO(2). The atrioventricular node was ablated in 18 dogs and dual-chamber pacing was instituted. In group 1 dogs (n = 9), heart rate was altered from 50 to 150 bpm(-1) in increments of 20 bpm(-1) in random order. In group 2 dogs (n = 9), heart rate was kept constant, and dobutamine was infused at doses of 5, 10, 20, 30, and 40 microg/kg(-1)/min(-1). During each intervention, hemodynamic parameters and MVO(2) were measured, and MCE was performed. MVO(2) increased more (P <.01) with inotropic compared with chronotropic stimulation, resulting in a parallel increase in CBF. MBV fraction and MCE-derived myocardial blood flow increased significantly with increases in MVO(2) (P <.05 and P <.001, respectively) when dobutamine was infused, but remained unchanged when heart rate alone was increased. We conclude that when MVO(2) is increased substantially, the resulting increase in CBF and MCE-derived myocardial blood flow is mediated, in part, by an increase in MBV. Thus, capillary recruitment plays an important role in the physiologic regulation of CBF. Lack of increase in MBV during dobutamine stress may indicate the presence of coronary stenosis or microvascular disease.
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