Coupling between the heart and arterial system in heart failure

Area of Science:

• Cardiovascular Physiology
• Biomedical Engineering
• Heart Mechanics

Background:

• Optimal coupling between the ventricle and arterial load is crucial for cardiac function.
• Physiologic and pathologic states influence ventriculoarterial coupling.
• Previous studies demonstrated optimal coupling for maximal stroke work.

Purpose of the Study:

• To investigate the matching between ventricular and arterial load properties.
• To quantify ventricular and arterial elastance in different states of cardiac function.
• To determine the impact of coupling on mechanical efficiency and stroke work.

Main Methods:

• Quantified ventricular properties using the slope of the end-systolic pressure-volume relationship (ventricular elastance).
• Expressed arterial load properties using the slope of the end-systolic pressure-stroke volume relationship (arterial elastance).
• Compared elastance ratios in normal subjects and patients with moderate and severe heart failure.

Main Results:

• In normal subjects (ejection fraction ≥60%), ventricular elastance was twice arterial elastance, optimizing mechanical efficiency.
• In moderate heart failure (ejection fraction 40-59%), ventricular elastance equaled arterial elastance, maximizing stroke work.
• In severe heart failure (ejection fraction <40%), ventricular elastance was less than half of arterial elastance, reducing efficiency and work output.

Conclusions:

• Normal ventriculoarterial coupling prioritizes left ventricular work efficiency.
• Moderate cardiac dysfunction involves matching ventricular and arterial properties to maximize stroke work, compromising efficiency.
• Severe cardiac dysfunction results in suboptimal coupling, with neither stroke work nor efficiency near maximum.