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The coronary circulation in cardiac hypertrophy
D J Sheridan1, A McAinsh, D J O'Gorman
1Academic Cardiology Unit, St. Mary's Hospital Medical School, London, England.
Insights
Left ventricular hypertrophy impairs coronary blood flow, increasing cardiac risks. This condition affects coronary perfusion due to hypertension and altered coronary physiology, potentially leading to myocardial ischemia.
Area of Science:
- Cardiovascular Physiology
- Cardiac Pathophysiology
Background:
- Left ventricular hypertrophy (LVH) is a significant risk factor for cardiac mortality and morbidity.
- LVH adversely affects coronary perfusion, often linked to hypertension and coronary disease.
- Cardiac hypertrophy can cause myocardial ischemia due to disturbed coronary physiology, even without coronary atherosclerosis.
Purpose of the Study:
- To investigate the mechanisms of impaired coronary reserve in cardiac hypertrophy.
- To explore the impact of altered coronary physiology and myocardial mechanics on coronary blood flow.
- To examine the regional distribution of coronary reserve reduction in hypertrophied hearts.
Main Methods:
- Review of existing studies on coronary flow and cardiac hypertrophy.
- Analysis of factors affecting coronary autoregulation in hypertrophied hearts, including pressure and diastolic/systolic pressures.
- Assessment of coronary vascular resistance during maximal vasodilation and morphological studies.
Main Results:
- Coronary flow autoregulation is disturbed in cardiac hypertrophy due to increased pressures and altered physiology.
- Increased minimal coronary vascular resistance suggests reduced arteriolar lumenal cross-sectional area.
- Systolic impairment of coronary flow may be greater in hypertrophied myocardium, with endocardial regions more affected.
Conclusions:
- Cardiac hypertrophy significantly impairs coronary reserve through multiple mechanisms.
- Understanding these impairments is crucial for managing patients with LVH and associated cardiovascular risks.
- Future research should focus on the effects of therapeutic interventions on coronary perfusion in LVH.
Abstract:
Left ventricular hypertrophy is a common and important risk factor for cardiac mortality and morbidity. Cardiac hypertrophy adversely affects coronary perfusion because hypertension, its most frequent cause, is a major risk factor for coronary disease, and because cardiac hypertrophy may be associated with myocardial ischemia even in the absence of atheromatous coronary disease due to disturbances in coronary physiology. Several studies have demonstrated impairment of coronary reserve in human and experimental cardiac hypertrophy. Normal autoregulation of coronary flow may be disturbed in cardiac hypertrophy for many reasons, including (a) increased perfusion pressure in hypertension, (b) increased diastolic and systolic left ventricular pressures, in addition to disturbed coronary physiology. Studies undertake in the presence of maximal coronary vasodilatation indicate an increased minimal coronary vascular resistance in hypertrophied hearts. Because such measurements were determined in the presence of maximal coronary vasodilation, they are likely to indicate a reduced arteriolar lumenal cross-sectional area per unit mass of tissue. Studies of cardiac and coronary morphology support an imbalance in myocardial and coronary growth in cardiac hypertrophy, but further evidence is needed to confirm this. Myocardial contraction impairs coronary flow, and available evidence suggests that this systolic impairment may be greater in hypertrophied myocardium, and that this may be an additional factor in limiting coronary flow in hypertrophy. A further important feature of impaired coronary reserve in cardiac hypertrophy is its distribution. Studies using radiolabeled microspheres indicate that coronary reserve is reduced in endocardial regions to a much greater extent than epicardial regions. Previously, treatment of conditions such as hypertension, which are commonly associated with hypertrophy, have concentrated on correction of the main defect. It is important to bear in mind, however, that such treatments may have direct and indirect effects on the coronary circulation, which may have an important bearing on preserving myocardial function. An important aspect of future research will be to determine the effects of treatment on coronary perfusion.