A new apex-ejecting perfused rat heart preparation: relation between coronary flow and loading conditions

Area of Science:

• Cardiovascular Physiology
• Experimental Cardiology
• Myocardial Performance Studies

Background:

• The isolated perfused rat heart is crucial for mechanical and biochemical research.
• Understanding coronary flow regulation under varying loading conditions is vital.

Purpose of the Study:

• To develop and evaluate a new isolated perfused rat heart preparation enabling independent control of aortic perfusion pressure and left ventricular afterload.
• To compare the coronary flow dynamics and autoregulation of this novel apex-ejecting model with a standard aortic ejecting model.

Main Methods:

• Developed an apex-ejecting isolated perfused rat heart model with separate control of aortic perfusion pressure and apex afterload.
• Compared this preparation with a standard aortic perfused and ejecting model.
• Conducted experiments at low calcium concentration (1.6 mmol/L) and assessed coronary flow, autoregulation, and oxygen extraction.

Main Results:

• Coronary flow showed pressure dependence in the standard model within specific pressure ranges (6.0-9.3 kPa).
• The apex-ejecting preparation demonstrated coronary autoregulation across varying afterloads.
• Adenosine induced vasodilation, making flow pressure-dependent in all preparations; the apex-ejecting model maintained flow and increased oxygen extraction with workload, mitigating hypoxia.

Conclusions:

• The apex-ejecting isolated perfused rat heart preparation offers improved control over loading conditions and better preservation of coronary autoregulation.
• This model is advantageous for studying myocardial oxygen consumption and reducing the risk of transient hypoxia during altered afterload conditions.