Blood flow structure and dynamics, and ejection mechanism in the left ventricle: analysis using echo-dynamography

Area of Science:

• Cardiovascular Physiology
• Biomedical Engineering
• Medical Imaging

Background:

• Understanding ventricular blood flow dynamics is crucial for assessing cardiac function.
• Previous methods lacked the resolution to detail flow structures during systole.
• Novel imaging technologies are needed to explore the relationship between wall motion and intracardiac flow.

Purpose of the Study:

• To investigate blood flow structure and dynamics during ventricular systole using echo-dynamography.
• To correlate observed flow patterns with specific cardiac wall motion events.
• To analyze the impact of these dynamics on the heart's pump function.

Main Methods:

• Utilized "echo-dynamography", a novel high-speed scanning echo-tomography technique.
• Measured velocity vector distribution and strain rate distribution via phase tracking.
• Analyzed flow structure, flow axis lines, and acceleration patterns during cardiac phases in 10 normal volunteers.

Main Results:

• Demonstrated laminar blood flow along the ventricular septum during ejection.
• Identified characteristic flow structures in early, mid-, and late systole.
• Correlated flow structures with specific wall dynamic events (peristaltic squeezing, mitral ring movement, bellows action, basal ventricle changes).
• Described three distinct acceleration modes (A, B, C) generated by wall dynamics.
• Observed macroscopic and microscopic myocardial asynchrony influencing flow and pump function.

Conclusions:

• Echo-dynamography effectively visualizes intricate blood flow structures during ventricular systole.
• Cardiac wall motion events are primary drivers of intracardiac flow dynamics.
• Understanding flow patterns and their generation by wall dynamics aids in evaluating cardiac pump efficiency.