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Left ventricular volume and function changes during beta-blockade and accompanying atrial pacing
I C Dormehl1, N Hugo, A L van Gelder
1AEC Institute for Life Sciences, Faculty of Medicine, University of Pretoria, South Africa.
American Journal of Physiologic Imaging
|January 1, 1989
Summary
Increasing heart rate decreases cardiac function, especially with beta-blockers. Septic shock involves more than just tachycardia, suggesting other depressant factors influence cardiac performance.
Area of Science:
- Cardiovascular Physiology
- Pharmacology
Background:
- Tachycardia is a common feature of early septic shock.
- Understanding the impact of heart rate on cardiac function is crucial for managing shock.
Purpose of the Study:
- To investigate the effects of increasing heart rate on left ventricular function in baboons.
- To assess the role of beta-blockade in modulating these effects.
- To compare these findings with cardiac function changes during septic shock.
Main Methods:
- Radionuclide ventriculography was used to measure left ventricular volumes, cardiac output, and ejection fraction.
- Experiments were conducted at rest and during transoesophageal pacing in anesthetized baboons.
- The study involved conditions with and without beta-blocker administration.
Main Results:
- Increasing heart rate led to a decrease in end-diastolic, end-systolic, and stroke volumes.
- This decrease was significantly more pronounced when beta-blockers were administered.
- Cardiac output and ejection fraction remained relatively stable, with a tendency to increase without beta-blockade.
Conclusions:
- Tachycardia alone does not fully explain cardiac function changes in early septic shock.
- Other depressant factors likely contribute to cardiac dysfunction during shock.
- Beta-blockade exacerbates the negative impact of increased heart rate on cardiac volumes.