Related Experiment Videos
Inotropic effects of ejection are myocardial properties
1Department of Internal Medicine, Bowman Gray School of Medicine, Wake Forest University, Winston-Salem, North Carolina 27157-1045.
The American Journal of Physiology
|March 1, 1994
Summary
Ejection in heart muscle has both positive and negative effects on pressure, influencing myocardial contractility. These ejection effects are fundamental properties of the heart muscle itself, not just the chamber.
Area of Science:
- Cardiovascular Physiology
- Muscle Mechanics
- Cardiac Electrophysiology
Background:
- Studies suggest left ventricular end-systolic pressure (LVPes) results from ejection effects.
- It remains unclear if these effects are chamber-specific or fundamental myocardial properties.
Purpose of the Study:
- To investigate the effects of ejection on myocardial contractility at the sarcomere level.
- To determine if ejection effects are basic myocardial properties.
Main Methods:
- Isolated rat cardiac trabeculae were used to simulate in situ sarcomere shortening patterns.
- An iterative computer loading system approximated ejection and isovolumic contractions.
- Experiments were conducted using solutions with Ca2+ or Sr2+ plus Ca2+.
Main Results:
- Simulated LVPes was lower with ejection in Ca2+ but higher in Sr2+ solutions compared to isovolumic contractions.
- Ejection prolonged contraction duration and time to end systole.
- Comparing pressure at equivalent time and volume revealed only a positive ejection effect in both solutions.
Conclusions:
- Both positive and negative ejection effects are fundamental myocardial properties.
- Ejection influences myocardial contractility at the sarcomere level.