Abstract 1779: Impact of Acute Moderate Right Ventricular Overload on Diastolic Transmitral Flow Efficiency: Analysis by Vortex Formation Time
Background: The right ventricle (RV) and left ventricle (LV) share interventricular septum (IVS), which mechanically transmits pressure gradients. In RV overload, IVS straightens and impairs LV filling. Early diastolic flow forms a vortex, which supports transmitral flow efficiency. Hemodynamic conditions for vortex formation are characterized by Vortex Formation Time (VFT) with values from 3.3 to 4.5. VFT is calculated from LV geometry, the fraction of a stroke volume contributed by the atrial component of LV filling, and from ejection fraction (EF). We hypothesized that LV diastolic filling efficiency, represented by VFT, is suboptimal in acute moderate RV overload.
Methods: In 11 open-chest pigs (age 3–4 months, weight 43±4 kg) with preserved pericardium, an acute moderate (45–60 mmHg) RV pressure overload was induced by constricting the pulmonary artery with an external balloon cuff. We studied transmitral flow and vortex formation at baseline and during increased afterload. Transmitral flow and other parameters (Table⇓) were characterized by Doppler and 2D echocardiography. All data are expressed as mean±SD and compared between baseline and intervention by a paired student t-test. A P-value <0.05 was considered statistically significant.
Results: Table⇓. Decreases in EF, LV end-diastolic pressure (LVEDP), and Tau were not significant. The experimentally-induced increase in the RV systolic pressure (RVSP) was statistically significant and was associated with a significant decrease in mean arterial pressure (MAP), cardiac output (CO), −dP/dt, LV end-diastolic volume (LVEDV) and VFT.
Conclusion: VFT is sensitive to a moderately increased RV afterload by a significant decrease and shift of its value outside of the optimal range suggesting alteration in LV filling rheology. VFT is a novel hemodynamic parameter that could lead to detection of hemodynamic changes associated with early stages of RV dysfunction.