Related Experiment Videos
The diastolic hyperemic flow versus pressure relation. A new index of coronary stenosis severity and flow reserve
G B Mancini1, M J McGillem, S F DeBoe
1Department of Internal Medicine, University of Michigan Medical School, Ann Arbor.
Insights
Measuring coronary flow reserve is challenging due to hemodynamic fluctuations. A new index, the diastolic hyperemic flow versus pressure slope, reliably indicates coronary artery stenosis severity, offering clinical potential.
Area of Science:
- Cardiovascular Physiology
- Hemodynamics
- Coronary Artery Disease
Background:
- Traditional coronary flow reserve (CFR) calculation is sensitive to hemodynamic variations, complicating serial assessments.
- Accurate measurement of coronary vascular reserve is crucial for diagnosing and managing coronary artery disease.
Purpose of the Study:
- To evaluate the impact of hemodynamic variability on CFR measurements.
- To identify and validate alternative indices for assessing coronary vascular reserve, particularly in the presence of subcritical stenosis.
Main Methods:
- Utilized an animal model (10 dogs) with instrumentation for measuring coronary flow, aortic pressure, and left ventricular pressure.
- Induced maximal hyperemia using adenosine infusion and created controlled subcritical coronary stenoses.
- Assessed multiple vascular reserve parameters, including traditional CFR and the diastolic hyperemic flow versus pressure slope.
Main Results:
- All tested vascular reserve indices, including traditional CFR, were significantly influenced by hemodynamic parameters like heart rate and mean aortic pressure.
- The diastolic hyperemic flow versus pressure slope demonstrated minimal dependence on heart rate and effectively differentiated between normal and stenotic conditions.
- This novel index proved reliable even when coronary flow and myocardial work were not independently controlled.
Conclusions:
- The diastolic hyperemic flow versus pressure slope is a robust and sensitive index for assessing subcritical coronary stenosis severity.
- This index offers a more reliable alternative to traditional CFR measurements, with potential clinical applications in diagnosing coronary artery disease.
Abstract:
The measurement of coronary flow reserve, traditionally calculated as the ratio of maximal hyperemic blood flow divided by basal flow, is difficult to interpret in serial studies because fluctuating hemodynamic parameters may affect either basal or hyperemic flow measurements. To determine the magnitude of this problem and to develop alternative approaches for measuring vascular reserve, 10 anesthetized dogs were instrumented with aortic and inferior vena cava occluders, electromagnetic coronary flow probes, and high-fidelity micromanometers in the left ventricle and aortic root. Coronary flow was measured in the basal state and during maximal hyperemia induced by a steady-state adenosine infusion. Observations were made in the absence of a stenosis and in the presence of two incremental degrees of subcritical stenosis produced by a rigid, external screw occluder. Several parameters of vascular reserve were determined: 1) coronary flow reserve (defined above), 2) mean hyperemic flow divided by mean aortic pressure, 3) mean hyperemic flow divided by the difference between mean aortic pressure and left ventricular end-diastolic pressure, and 4) the slope of the instantaneous relation between diastolic hyperemic flow versus pressure. Each parameter was measured during five steady-state pressure levels achieved by partial occlusion of either the inferior vena cava or the aorta and the levels ranged from 82 +/- 8 mm Hg (mean +/- SD) to 127 +/- 9 mm Hg during hyperemia. All measures of vascular reserve were found to be dependent on hemodynamic parameters such as heart rate and mean aortic pressure. The slope of the instantaneous relation between diastolic hyperemic flow and pressure, however, showed only minimal dependence on heart rate and, in contrast to coronary flow reserve measurements, distinguished between the normal and the two stenotic states. Further, this optimal performance of the hyperemic flow versus pressure slope index was shown in a model in which coronary flow and myocardial work were not independently controlled. This index provides a sensitive and reliable indication of subcritical stenosis severity that may have clinical applications.