Related Experiment Videos
Native beta-adrenergic support for left ventricular dysfunction in experimental mitral regurgitation normalizes
M Nagatsu1, M R Zile, H Tsutsui
1Department of Medicine, Gazes Cardiac Research Institute, Medical University of South Carolina, Charleston 29425-2221.
Circulation
|February 1, 1994
Summary
The adrenergic nervous system supports heart function, maintaining normal contractile indexes even with underlying myocardial depression. This study shows that without beta-blockade, significant heart dysfunction can be masked by this natural support.
Area of Science:
- Cardiology
- Physiology
- Pharmacology
Background:
- The adrenergic nervous system is known to support failing heart function.
- The extent of this adrenergic support has not been extensively quantified.
- This study investigates the capacity of the adrenergic system to maintain cardiac function during myocardial depression.
Purpose of the Study:
- To test the hypothesis that the adrenergic nervous system can maintain normal cardiac pump and contractile function indexes despite significant innate myocardial depression.
- To quantify the magnitude of adrenergic support in a model of heart failure.
Main Methods:
- A canine model of chronic mitral regurgitation was used to induce left ventricular dysfunction.
- Cardiac function indexes were measured on and off beta-blockade at baseline and after 3 months of induced heart failure.
- Myocardial contractile function was assessed using indexes such as end-ejection stress-volume relation (EESVR), end-systolic stiffness, ejection fraction-stress, and velocity of circumferential fiber shortening (VCF)-stress relations.
Main Results:
- After 3 months of mitral regurgitation, most contractile function indexes were normal without beta-blockade, except for a mildly reduced VCF-stress relation.
- Acute beta-blockade significantly reduced EESVR and end-systolic stiffness in dogs with chronic mitral regurgitation.
- Beta-blockade also significantly worsened the ejection fraction-stress and VCF-stress relations, indicating substantial underlying contractile depression.
Conclusions:
- The adrenergic nervous system effectively maintains cardiac function indexes in the normal range despite significant innate myocardial depression.
- In the absence of beta-blockade, the contribution of adrenergic support can mask considerable underlying heart dysfunction.
- These findings highlight the critical role of adrenergic support in maintaining cardiac performance in heart failure.