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Chronically decreased aortic distensibility causes deterioration of coronary perfusion during increased left
S Ohtsuka1, M Kakihana, H Watanabe
1Department of Internal Medicine, University of Tsukuba, Japan.
Insights
Chronically decreased aortic distensibility impairs heart blood flow during high demand, potentially causing subendocardial ischemia without coronary stenosis. This affects coronary flow reserve and endocardial perfusion.
Area of Science:
- Cardiovascular Physiology
- Biomedical Engineering
Background:
- Aortic distensibility reduction is common in atherosclerosis, hypertension, and aging.
- Long-term impacts of reduced aortic distensibility on coronary perfusion remain under-investigated.
Purpose of the Study:
- To investigate the long-term effects of decreased aortic distensibility on cardiac function and coronary perfusion.
- To assess the relationship between aortic distensibility and coronary blood flow under varying ventricular contractility.
Main Methods:
- Twelve dogs were divided into a control group and a group with experimentally reduced aortic distensibility (aortic banding).
- Coronary artery flow and transmural flow distribution were measured after 4-6 weeks.
- Measurements were taken at baseline and during induced increased ventricular contraction (isoproterenol infusion).
Main Results:
- Reduced aortic distensibility did not alter baseline hemodynamics or coronary flow.
- During isoproterenol infusion, dogs with reduced aortic distensibility showed a greater increase in coronary flow but a reduced coronary flow reserve ratio.
- Endocardial blood flow and the endocardial/epicardial flow ratio decreased significantly in the group with reduced aortic distensibility, with evidence of subendocardial ischemia (ST elevation).
Conclusions:
- Chronically decreased aortic distensibility exacerbates reductions in coronary flow reserve during increased cardiac demand.
- Impaired endocardial blood flow and potential subendocardial ischemia can occur due to reduced aortic distensibility, even without coronary artery stenosis.
Objectives:
This study investigated the long-term effects of decreased aortic distensibility on the heart in relation to coronary perfusion.
Background:
Aortic distensibility is decreased in patients with atherosclerosis and hypertension and in the elderly. However, the effect of a long-term decrease in aortic distensibility on coronary perfusion has not been fully investigated.
Methods:
Twelve anesthetized dogs underwent thoracotomy and were allocated to two groups: Group I included six control dogs with a normal aorta; Group II included six dogs with decreased aortic distensibility produced by banding the descending aorta. After 4 to 6 weeks, the dogs had a second operation to measure coronary artery flow and transmural flow distribution. Because the effect of decreased aortic distensibility on coronary perfusion may be affected by ventricular contractility, measurements were performed at baseline and during increased ventricular contraction induced by isoproterenol infusion.
Results:
At baseline, arterial compliance was reduced by 35% in Group II, but there was no change in total mean arterial resistance. Hemodynamic variables, regional wall motion and coronary flow were also similar in both groups. However, during isoproterenol infusion, coronary flow increased more in Group II than in Group I (p < 0.01), and the coronary flow reserve ratio (maximal peak hyperemic flow divided by rest flow) decreased more in Group II than in Group I (mean [+/- SD] 1.9 +/- 0.4 vs. 2.4 +/- 0.3, p < 0.05). Moreover, although the transmural flow distribution was similar in the two groups at baseline, during isoproterenol infusion the endocardial flow increased less in Group II than in Group I (p < 0.05), and the endocardial/epicardial flow ratio was significantly decreased in Group II compared with Group I (mean [+/- SD] 0.70 +/- 0.18 vs. 0.99 +/- 0.22, p < 0.05). The subendocardial electrocardiogram showed ST segment elevation during isoproterenol infusion in Group II (p < 0.05) but not in Group I.
Conclusions:
These results demonstrate that during increased ventricular contraction, chronically decreased aortic distensibility contributes to a further decrease in the coronary flow reserve ratio, impairs endocardial blood flow and may induce subendocardial ischemia even in the absence of coronary artery stenosis.