Image-Based Simulations Show Important Flow Fluctuations in a Normal Left Ventricle: What Could be the Implications?

Area of Science:

• Cardiovascular Physiology
• Biomedical Engineering
• Fluid Dynamics

Background:

• Intra-cardiac flow dynamics in healthy individuals remain debated.
• The presence of flow instabilities in the healthy left ventricle (LV) has significant physiological and clinical implications.
• Existing hypotheses on cardiac flow often assume smooth, non-turbulent patterns.

Purpose of the Study:

• To investigate the existence of flow instabilities within a healthy left ventricle (LV).
• To utilize patient-specific computational fluid dynamics (CFD) to analyze intra-cardiac flow patterns.
• To challenge conventional assumptions regarding normal cardiac flow.

Main Methods:

• Simulated 35 cardiac cycles using a patient-specific left heart model derived from cardiovascular magnetic resonance (CMR).
• Incorporated anatomical details including valves, atrium, ventricle, papillary muscles, and ascending aorta.
• Computed phase-averaged flow patterns, fluctuating kinetic energy (FKE), and frequency components.

Main Results:

• Disturbed intra-ventricular flow observed during diastole with notable cycle-to-cycle variations.
• Phase-averaged velocity fields align with typical CMR measurements and prior CFD studies.
• Peak fluctuating kinetic energy (FKE) reached 25% of maximum flow kinetic energy during E-wave deceleration.
• High FKE values, exceeding 200 Hz, were localized in the basal region of the LV.

Conclusions:

• High-frequency flow fluctuations appear common in normal left ventricles (LV).
• Current assumptions in cardiac flow computation may be insufficient.
• Standard methods for deriving quantities from CMR velocity fields might introduce biases.