Evaluation of a lumped parameter model for isolated working rat hearts

Area of Science:

• Cardiovascular physiology
• Biomechanical engineering
• Pharmacology

Background:

• The input impedance of the rat aorta is crucial for understanding cardiac load.
• Mechanical models are used to simulate aortic impedance but may not fully replicate physiological conditions.

Purpose of the Study:

• To evaluate whether a mechanical model of rat aortic input impedance provides a constant load for an isolated rat heart.
• To investigate the influence of flow rate and coronary impedance on the mechanical model's load characteristics.

Main Methods:

• A mechanical model of rat aortic input impedance was perfused with a pulsatile pump and an isolated rat heart.
• Impedance components were computed under varying flow rates.
• Changes in coronary impedance induced by adenosine triphosphate were assessed.

Main Results:

• Mechanical model impedance components varied linearly with flow rate and were interactive.
• The isolated heart's total load comprised parallel model and coronary impedances.
• Adenosine triphosphate altered coronary impedance, causing flow redistribution and affecting model impedance.

Conclusions:

• The mechanical model of rat aortic input impedance does not present a constant load to the isolated heart.
• Variations in both model and coronary impedances contribute to a dynamic and non-constant cardiac load.