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Coronary microvascular resistance in hypertensive cats
H Kanatsuka1, K G Lamping, C L Eastham
1Department of Internal Medicine, College of Medicine, University of Iowa, Iowa City 52242.
Circulation Research
|March 1, 1991
Summary
Chronic systemic hypertension increases coronary vascular resistance in cats, particularly in larger coronary microvessels. This study investigated the impact of hypertension on coronary microcirculation pressure distribution.
Area of Science:
- Cardiovascular Physiology
- Hypertension Research
- Microcirculation Studies
Background:
- Chronic systemic hypertension is known to affect vascular resistance in various microvascular beds.
- Understanding these alterations is crucial for managing cardiovascular complications.
Purpose of the Study:
- To assess the impact of chronic systemic hypertension on pressure distribution within the coronary microcirculation.
- To identify the specific microvascular site responsible for increased coronary vascular resistance in hypertension.
Main Methods:
- Utilized a one-kidney, one-wrap (Page model) in cats to induce chronic hypertension.
- Employed a servonulling system for direct measurement of epimyocardial microvessel pressures in the beating left ventricle.
- Measured myocardial perfusion using radiolabeled microspheres and categorized microvessels by size (<200, 200-300, ≥300 microns).
Main Results:
- Hypertensive cats exhibited significantly higher mean arterial pressure (153 ± 5 mmHg) and increased left ventricular mass (34%) compared to normotensive controls.
- Despite no difference in overall myocardial perfusion, coronary vascular resistance of the left ventricle was elevated in hypertensive cats.
- Mean microvascular pressures in large (≥300 microns), medium (200-300 microns), and small (<200 microns) arterial microvessels of hypertensive cats were 144±8, 127±6, and 115±7 mmHg, respectively.
Conclusions:
- Chronic systemic hypertension leads to increased coronary vascular resistance in the left ventricle.
- The pressure drop occurs predominantly in the larger arterial microvessels of the coronary circulation.
- These findings highlight a specific site of resistance increase in the coronary microcirculation due to hypertension.