Flow transport and not ejection fraction determines blood stasis in patients with impaired left ventricular systolic...

Area of Science:

• Cardiovascular Physiology
• Biomedical Engineering
• Medical Imaging Analysis

Background:

• Impaired left ventricular (LV) systolic function increases risk of intraventricular thrombosis and cardioembolism.
• Left ventricular ejection fraction (EF) has limitations in predicting these thrombotic events below certain thresholds.
• Additional factors beyond EF contribute to variability in thrombosis risk.

Purpose of the Study:

• To introduce and validate queue models for analyzing LV blood transit.
• To connect flow component analysis with residence time (RT) mapping.
• To elucidate the relationship between EF, direct flow (DF), residual volume (RV), and LV blood RT.

Main Methods:

• Development of queue models providing closed-form expressions for average LV blood RT.
• Validation of models against RT data from vector flow mapping in 332 subjects.
• Inclusion of controls and patients with acute myocardial infarction (AMI), hypertrophic cardiomyopathy (HCM), and dilated cardiomyopathy (DCM).

Main Results:

• LV blood RT becomes more sensitive to DF as EF decreases.
• RT is minimized with first-in-first-out (FIFO) blood transit.
• Direct flow (DF) disrupts FIFO patterns, prolonging RT and increasing blood stasis, especially at low EF.
• FIFO models demonstrated good performance in assessing RT.

Conclusions:

• Large direct flows (DF) exacerbate blood stasis in the LV when EF is low.
• Queue models explain the limitations of EF as a sole predictor of intraventricular thrombosis risk.
• These models offer a novel framework for understanding LV hemodynamics and thrombosis formation.