Abstract 2689: Physiological Vortex Change After Acute Increase Afterload
Background: The flow of blood from the left atrium to the left ventricle (LV) during early diastolic filling forms a rotating fluid mass called a vortex ring. It has been demonstrated that fluid transport by vortex ring formation is more efficient than by a straight jet. The vortex ring can be characterized by a Vortex Formation Time (VFT), which can be expressed as a unitless length-to-diameter ratio of an ejected fluid column. VFT can be calculated from echocardiography measurements of LV geometry, the fraction of a stroke volume contributed by the atrial component of LV filling, and from ejection fraction (EF).
Methods: In 6 open-chest pigs, we studied transmitral flow and vortex formation at baseline and during increased afterload (induced by aortic constriction with a tourniquet). Transmitral flow and other parameters (Table⇓) were characterized by Doppler and 2D echocardiography. Vortex formation was tracked by diluted contrast microbubbles and harmonic contrast echocardiography. All data are expressed as mean±SD and compared between baseline and intervention by a nonparametric Wilcoxon test. A P-value of <0.05 was considered statistically significant.
Results: See Table⇓. Changes in LV diastolic volume (LVD) and heart rate (HR) were not significant; decreases in EF and SV were borderline or significant, respectively. Although the experimentally-induced increase in the mean aortic pressure (MAP) was not statistically significant, vascular resistance (VR) of the constricted aorta increased significantly and was associated with a significant decrease in VFT.
Conclusion: VFT is a sensitive, noninvasively measurable indicator of a mildly increased afterload. The decreased in VFT suggests alteration in transmitral rheology. VFT is a novel hemodynamic parameter that could lead to detection of hemodynamic changes in early stages of cardiac diseases.