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Background: Current characterization of ventricular state and timing of potential intervention in patients with aortic regurgitation (AR) use simple indices with limited predictive value. The dynamics of left ventricle (LV) diastolic vortex blood flow and its impact on energy consumption is emerging as a new means of defining structural heart disease. We now apply such analysis to provide greater fidelity to characterization of AR severity.
Hypothesis: The extent to which diastolic collision of the two opposing jets, the mitral inflow and the aortic regurgitant jets, distort ventricular blood flow kinematics and viscous energy loss, can delineate ventricular state in AR.
Methods: In vitro experiments were performed by generating pulsatile flow through prosthetic valves placed in a custom elastic left heart model. The heart rate was held at 70 bpm, peak aortic pressure and mitral flow rate at 120 mmHg and 6.9 L/m respectively. Four degrees of AR were induced by modulating closure of a 25 mm porcine valve, creating a central regurgitant jet (regurgitant orifice areas of 0, 0.09, 0.17, and 0.96 cm2). Velocity measurements were acquired using time-resolved 2D particle image velocimetry. Vorticity and viscous energy loss were calculated from the raw velocity field data.
Results: The AR jet significantly altered diastolic flow dynamics. With increasing severity of AR, mean vorticity at mid-diastole (t ∼ 0.55 s) fluctuated in magnitude and eventually demonstrated a reversed swirl direction (-0.24, -0.38, -0.002, 2.53 rad/s). At mid-diastole, a secondary early peak in energy loss arose and increased progressively with AR severity (1.68, 6.31, 7.58, 9.43 mW/m). The ratio of mid-diastolic to end-diastolic energy loss peak approaches 1 with increasing severity of AR (0.29, 0.58, 0.64, 0.92).
Conclusions: AR significantly impacts diastolic flow dynamics causing reversal of diastolic vortex with subsequent effect on LV energetics. Data from selected patients is being extracted from 4D flow MRI and used to validate these concepts and clinical implications.
Poster Hall, Hall C
Saturday, March 18, 2017, 9:45 a.m.-10:30 a.m.
Session Title: Valvular Heart Disease: Aortic Regurgitation
Abstract Category: 36. Valvular Heart Disease: Clinical
Presentation Number: 1184-026
- 2017 American College of Cardiology Foundation