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Coronary vascular mechanisms involved in decompensation from hypertrophy to heart failure
1Department of Medicine, Harvard Medical School, Brigham & Women's Hospital, Boston, Massachusetts.
Insights
Impaired coronary reserve in ventricular hypertrophy can lead to heart failure. Reduced blood flow during stress, like exercise, may cause damage and worsen heart function over time.
Area of Science:
- Cardiology
- Physiology
Background:
- Ventricular hypertrophy is characterized by reduced coronary reserve.
- This reduction may not impact baseline function but is critical during stress.
Purpose of the Study:
- To explore the role of impaired coronary reserve in the progression of compensated left ventricular hypertrophy to failure.
Main Methods:
- The study hypothesizes mechanisms involving hemodynamic changes and subendocardial wall stress.
- It considers the impact of exercise and other stressors on coronary perfusion.
Main Results:
- Impaired subendocardial coronary reserve is linked to hypertrophy and increased wall stress during exercise.
- Reduced coronary perfusion during stress can lead to myocyte necrosis and fibrosis.
Conclusions:
- Myocardial ischemia and fibrosis, along with altered loading conditions, impair both systolic and diastolic function.
- These factors accelerate the transition from compensated hypertrophy to heart failure.
Abstract:
One potential mechanism for the eventual failure of the hypertrophied ventricle to maintain compensation may involve impaired coronary reserve. Reduced coronary reserve is one of the hallmarks of ventricular hypertrophy. Although this reduced coronary reserve may not affect baseline left ventricular function, it could be of greater importance during periods of stress, such as occur during exercise, where increased metabolic demands induced by the stress may not be fully met by an increase in coronary blood flow. The impaired subendocardial coronary reserve is caused not only by the hypertrophy but also by the hemodynamic changes (for example, the left ventricular subendocardial wall stress that increases markedly on exercise). In the severely hypertrophied heart, there are impaired subendocardial wall function and reduced subendocardial coronary perfusion in response to exercise. It is hypothesized that these episodes occur frequently under normal activity (for example, in response to exercise, excitement, eating) and that they become severe enough to induce myocyte necrosis and replacement fibrosis. This in turn will impair left ventricular systolic function. Furthermore, myocardial ischemia and left ventricular fibrosis as well as the altered loading conditions result in impaired diastolic function, which in turn diminishes systolic function. All of these mechanisms working in concert act to further impair systolic function and accelerate the progression of compensated left ventricular hypertrophy to failure.