Coronary microvascular resistance in hypertensive cats
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H Kanatsuka1, K G Lamping, C L Eastham
1Department of Internal Medicine, College of Medicine, University of Iowa, Iowa City 52242.
Insights
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.
Abstract:
Chronic systemic hypertension has been shown to alter the distribution of vascular resistance in many microvascular beds. The purposes of this study were to assess the effects of chronic systemic hypertension on the pressure distribution in the coronary microcirculation and to determine the microvascular site where coronary vascular resistance is increased. Cats were made hypertensive using a one-kidney, one-wrap model (Page model). A servonulling system was used to directly measure pressures in the epimyocardial microvessels of the beating left ventricle in normotensive and hypertensive cats. In chronically hypertensive cats, mean arterial pressure was 153 +/- 5 mm Hg compared with 98 +/- 3 mm Hg in normotensive cats (p less than 0.05). Left ventricular mass was increased approximately 34% in hypertensive cats (9.4 +/- 0.3 versus 7.0 +/- 0.3 g, p less than 0.05). Myocardial perfusion measured using radiolabeled microspheres was not different between hypertensive and normal cats. Coronary vascular resistance of the left ventricle was increased in hypertensive cats (0.90 +/- 0.08 versus 0.66 +/- 0.05 mm Hg x min x 100 g/ml, p less than 0.05). Microvascular pressures were measured in three groups of microvessels: small, less than 200 microns; medium, 200-300 microns; and large, greater than or equal to 300 microns. Mean microvascular pressures of large, medium, and small arterial microvessels in hypertensive cats were 144 +/- 8, 127 +/- 6, and 115 +/- 7 mm Hg, respectively.(ABSTRACT TRUNCATED AT 250 WORDS)