Left atrial relaxation and left ventricular systolic function determine left atrial reservoir function

Area of Science:

• Cardiovascular Physiology
• Cardiac Mechanics
• Echocardiography

Background:

• The determinants of left atrial (LA) reservoir function and its impact on left ventricular (LV) function remain incompletely understood.
• Quantifying these relationships is crucial for understanding cardiac performance.

Purpose of the Study:

• To quantify the determinants of LA reservoir function and its influence on LV function.
• To investigate the impact of acute LV regional ischemia on LA reservoir function and mechanics.

Main Methods:

• Utilized an open-pericardium pig model with induced LV regional ischemia.
• Employed high-fidelity pressure recordings (LV, LA, RV) and 2D echocardiography for LA area assessment.
• Calculated LA pressure-area loops, Doppler transmitral flow, LV tau, LA relaxation, and LA stiffness.

Main Results:

• Identified two distinct LA reservoir phases: early (dependent on LA ejection rate and relaxation) and late (dependent on LV base descent).
• Acute LV ischemia significantly decreased LA reservoir area change and increased LA stiffness.
• LA reservoir filling was the strongest predictor of cardiac output.

Conclusions:

• LA reservoir function comprises early and late phases influenced by atrial dynamics and LV base movement.
• Acute LV regional ischemia adversely affects LA reservoir function by increasing LA stiffness and reducing LV base descent.