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A method for measuring systolic and diastolic microcirculatory red cell flux within the canine myocardium
K D Barclay1, G A Klassen, R W Wong
1Department of Physiology and Biophysics, Dalhousie University, Halifax, NS, Canada.
Insights
Laser Doppler velocimetry reveals complex red blood cell movement patterns in the canine myocardium. These microcirculatory dynamics differ significantly from macrocirculatory coronary blood flow.
Area of Science:
- Cardiovascular Physiology
- Microcirculation Research
- Biomedical Optics
Background:
- Understanding red blood cell (RBC) movement within the contracting myocardium during the cardiac cycle is limited.
- Current knowledge gaps exist regarding microcirculatory dynamics in the heart muscle.
Purpose of the Study:
- To develop and apply a novel method for measuring RBC movement in the beating canine myocardium.
- To investigate regional patterns of microcirculatory flux during the cardiac cycle.
Main Methods:
- Utilized laser Doppler velocimetry (LDV) with a lensed fiber-optic probe inserted into the canine myocardium.
- Employed heterodyning techniques for stable, high-quality measurements of RBC movement in microvessels.
Main Results:
- Observed distinct regional patterns: continuous epicardial flux with peaks and predominantly diastolic endocardial flux.
- Demonstrated continued microcirculatory RBC movement with reactive hyperemia following temporary arterial flow occlusion.
- Modeling indicated a significant role of small coronary veins in regulating microcirculatory RBC movement.
Conclusions:
- Laser Doppler velocimetry is effective for measuring RBC flux in the beating canine myocardium.
- Myocardial microcirculation exhibits complex dynamics not apparent in epicardial or large coronary vessel flow.
Background:
Knowledge of the patterns of movement of red cells during the cardiac cycle in the microcirculation within the contracting myocardium is largely unknown. We describe a method of making such measurements in the canine myocardium using the technique of laser Doppler velocimetry.
Methods:
A lensed 100 microm fiber-optic probe was inserted into the beating myocardium at various sites. Using an ultra-stable laser and achieving measurement stability by heterodyning the laser light and reflected light from the tissue, it was possible to obtain a stable high quality measurement of predominately red cell movement in the microcirculation.
Results:
Unique regional patterns of red cell movement within the myocardium were observed. Epicardial flux was continuous with peaks while endocardial flux was predominately diastolic. Stopping flow in the epicardial artery for 5-6 s demonstrated that red cell movement continues in the microcirculation with some reduction followed by a delayed reactive hyperemia. Modeling demonstrates an important role for the small coronary veins in control of microcirculatory red cell movement.
Conclusions:
It is possible using laser Doppler velocimetry to measure red blood cell flux in the beating canine myocardium. Such measurements demonstrate a high degree of complexity which is not reflected in epicardial coronary arterial or venous flow.
