Related Experiment Videos
Cardiac hypertrophy impairs recovery from ischaemia because there is a reduced reactive hyperaemic response
A M McAinsh1, M A Turner, D O'Hare
1Academic Cardiology Unit, St. Mary's Hospital Medical School, London, UK.
Insights
Cardiac hypertrophy impairs reactive hyperemia, limiting flow debt repayment and prolonging myocardial ischemia. This makes the hypertrophied heart more vulnerable to brief ischemic episodes, potentially increasing associated morbidity.
Area of Science:
- Cardiovascular Physiology
- Myocardial Metabolism
- Cardiac Pathophysiology
Background:
- Cardiac hypertrophy, often caused by pressure overload, can alter coronary flow reserve.
- Impaired coronary flow reserve may affect the heart's ability to recover from ischemia.
Purpose of the Study:
- To investigate if impaired coronary flow reserve in cardiac hypertrophy limits flow debt repayment.
- To determine if this limitation exacerbates or prolongs myocardial ischemia.
Main Methods:
- Left ventricular hypertrophy was induced in guinea pigs via aortic constriction.
- Isolated hearts underwent Langendorff perfusion with varying occlusion lengths.
- Reactive hyperemia and metabolic recovery (aerobic/anaerobic) were assessed.
Main Results:
- Hypertrophied hearts showed impaired reactive hyperemia in magnitude and duration.
- Flow debt repayment was significantly reduced, indicating inadequate myocardial recovery.
- Aerobic metabolism decreased, while anaerobic metabolism increased in hypertrophied hearts.
Conclusions:
- The hypertrophied heart is more susceptible to brief ischemia due to impaired reactive hyperemia.
- Delayed metabolic recovery contributes to increased vulnerability.
- These findings may explain increased morbidity in cardiac hypertrophy.
Objective:
The aim was to investigate whether impaired coronary flow reserve associated with cardiac hypertrophy could significantly limit the flow debt repayment following short periods of coronary occlusion and exacerbate or prolong episodes of myocardial ischaemia.
Methods:
Left ventricular hypertrophy was induced in guinea pigs by aortic constriction and the hearts were isolated six weeks later for Langendorff perfusion. Sham operated animals served as controls. The reactive hyperaemic response was studied following various lengths of occlusion of flow and the extent of aerobic and anaerobic metabolism was assessed in each group.
Results:
Heart weight/body weight ratio was increased by approximately 25% (P < 0.001) with aortic constriction. The reactive hyperaemic flow response in isolated hearts was impaired by hypertrophy in both magnitude (P < 0.05) and duration. The repayment of flow debt was also significantly reduced, suggesting an inadequate recovery of the myocardium following the occlusion. The total amount of O2 consumed by the heart throughout the duration of hyperaemia was less in hypertrophy than in sham operated controls, suggesting a decrease in aerobic metabolism. Total lactate discharge expressed as a ratio of O2 consumed, which provides an estimation of the degree of anaerobic in relation to aerobic metabolism, was greater in hypertrophy than in sham operated controls.
Conclusions:
The hypertrophied heart is more vulnerable to brief periods of ischaemia because of an impaired reactive hyperaemic response which results in delayed metabolic recovery. These abnormalities may contribute to the increased morbidity associated with cardiac hypertrophy.