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Elastic properties of normal and hypertrophied cardiac muscle
Insights
Cardiac muscle stiffness changes with hypertrophy, with pressure overload increasing stiffness and volume overload often showing normal stiffness. Prognostic indicators for hypertrophy reversibility include wall stress and chamber size ratios.
Area of Science:
- Cardiology
- Biomedical Engineering
- Physiology
Background:
- Cardiac hypertrophy, an increase in heart muscle mass, can result from pressure or volume overload.
- Understanding the mechanical properties of hypertrophied cardiac muscle is crucial for diagnosing and managing heart conditions.
- Age and disease severity can influence cardiac muscle mechanics.
Purpose of the Study:
- To review changes in mechanical properties of cardiac muscle during pressure and volume overload hypertrophy.
- To identify preoperative predictors of irreversible hypertrophy and chamber enlargement.
- To compare the effects of age and hypertrophy on muscle stiffness.
- To explore relationships between diastolic properties and systolic function.
Main Methods:
- Analysis of elastic properties of cardiac muscle.
- Review of animal and clinical studies on cardiac hypertrophy.
- Examination of parameters like wall stress, volume:mass, and radius:thickness ratios.
Main Results:
- Muscle stiffness is elevated in pressure overload hypertrophy and typically normal in volume overload hypertrophy.
- Clinical studies suggest normal stiffness in mild/moderate valvular disease, elevated in severe cases.
- Wall stress, volume:mass, and radius:thickness ratios are useful prognostic indicators for hypertrophy reversibility.
- Age and hypertrophy have similar effects on muscle stiffness in rats.
- Increased muscle stiffness correlates with decreased shortening velocity, but force development may be preserved.
Conclusions:
- Cardiac muscle stiffness varies depending on the type and severity of overload and disease.
- Specific ratios and wall stress can predict the reversibility of cardiac hypertrophy.
- Age does not significantly alter the relationship between hypertrophy and muscle stiffness.
- While stiffness impacts velocity, contractile function may remain intact.
Abstract:
This brief review addresses itself to the following questions on normal and hypertrophied muscle. 1) What changes, if any, take place in the mechanical properties of cardiac muscle during pressure and volume overload hypertrophy? 2) What parameters may signal preoperatively irreversibility of hypertrophy and chamber enlargement? 3) Are the effects of age and hypertrophy on muscle stiffness similar? 4) What relationships exist between diastolic properties and systolic function? The analyses of the elastic properties of cardiac muscle based on several animal and clinical studies indicate that: a) Muscle stiffness in pressure overload is elevated and is normal in volume overload in the majority of the animal studies. However, the clinical studies support the hypothesis that muscle stiffness remains normal in mild to moderate degrees of valvular disease and is elevated in severe valvular disease. b) Wall stress, volume:mass, and radius:thickness ratios are useful prognostic indicators regarding reversibility of wall hypertrophy and/or chamber enlargement. c) Effects of age and hypertrophy on muscle stiffness are similar for the age range of young adult (6 mo) to old (90 wk) SHR and WKY rats. d) Increased muscle stiffness is invariably accompanied by decreased muscle shortening velocity but rate of force development and peak force may not be impaired.