Estimation of left ventricular elastance without altering preload or afterload in the conscious dog

Area of Science:

• Cardiovascular Physiology
• Cardiac Mechanics
• Hemodynamics

Background:

• The end-systolic pressure-volume line (ESPVL) slope, or end-systolic elastance (EES), is a key index of left ventricular contractility.
• Accurate determination of EES is crucial for understanding cardiac function.
• Traditional methods for EES assessment often require altering preload or afterload, which can complicate interpretation.

Purpose of the Study:

• To determine the slope of the left ventricular end-systolic pressure-volume line (EES) without altering preload or afterload in conscious dogs.
• To validate a novel single-beat method for calculating EES.
• To assess the responsiveness of EES to inotropic agents.

Main Methods:

• Left ventricular pressure and volume were measured in instrumented conscious dogs (n=10).
• Pressure-volume loops were generated using vena caval occlusion.
• End-systolic elastance (EES) was calculated using a single beat and compared to values derived from variably loaded loops.
• Inotropic state was modulated using dobutamine and verapamil after autonomic blockade.

Main Results:

• EES significantly increased after dobutamine administration (from 8.9 to 12.5 mm Hg/mL) and decreased after verapamil administration (from 11.1 to 6.3 mm Hg/mL).
• The single-beat EES calculation showed similar trends, increasing with dobutamine (9.1 to 12.0 mm Hg/mL) and decreasing with verapamil (9.6 to 7.3 mm Hg/mL).
• Both methods demonstrated appropriate responses to positive and negative inotropic stimuli.

Conclusions:

• A single-beat method provides a reliable estimation of left ventricular end-systolic elastance (EES).
• This technique allows for EES assessment without the need to alter preload or afterload.
• The validated method is suitable for evaluating cardiac contractility in conscious animals.