Publicación: Intraventricular vortex properties in nonischemic dilated cardiomyopathy
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2014-03-01
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Prologuista
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Atribución-NoComercial-SinDerivadas 4.0 Internacional
info:eu-repo/semantics/openAccess
info:eu-repo/semantics/openAccess
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American Physiological Society
Resumen
Vortices may have a role in optimizing the mechanical efficiency and blood mixing of the left ventricle (LV). We aimed to characterize the size, position, circulation, and kinetic energy (KE) of LV main vortex cores in patients with nonischemic dilated cardiomyopathy (NIDCM) and analyze their physiological correlates. We used digital processing of color-Doppler images to study flow evolution in 61 patients with NIDCM and 61 age-matched control subjects. Vortex features showed a characteristic biphasic temporal course during diastole. Because late filling contributed significantly to flow entrainment, vortex KE reached its maximum at the time of the peak A wave, storing 26 ± 20% of total KE delivered by inflow (range: 1–74%). Patients with NIDCM showed larger and stronger vortices than control subjects (circulation: 0.008 ± 0.007 vs. 0.006 ± 0.005 m2/s, respectively, P = 0.02; KE: 7 ± 8 vs. 5 ± 5 mJ/m, P = 0.04), even when corrected for LV size. This helped confining the filling jet in the dilated ventricle. The vortex Reynolds number was also higher in the NIDCM group. By multivariate analysis, vortex KE was related to the KE generated by inflow and to chamber short-axis diameter. In 21 patients studied head to head, Doppler measurements of circulation and KE closely correlated with phase-contract magnetic resonance values (intraclass correlation coefficient = 0.82 and 0.76, respectively). Thus, the biphasic nature of filling determines normal vortex physiology. Vortex formation is exaggerated in patients with NIDCM due to chamber remodeling, and enlarged vortices are helpful for ameliorating convective pressure losses and facilitating transport. These findings can be accurately studied using ultrasound. intraventricular vortex dynamics may have an important role in cardiac hemodynamics. During early filling and atrial contraction, strong jets entering the left ventricle (LV) lead to the formation of vortex rings near the tips of the mitral valve leaflets. Due to the chiral configuration formed by the LV inflow tract, main chamber, and LV outflow tract (LVOT), these vortex rings evolve into large rotational flow structures that occupy a large fraction of the ventricle. Recent clinical data in patients with diastolic dysfunction indicate that LV vortices may facilitate flow from the left atrium to the LV apex (6). Also, vortical structures may increase ejection efficiency by conserving the momentum of blood built up during filling (1). Finally, vortices may contribute to blood mixing inside the ventricle, avoiding stasis (6, 19, 30, 32, 33, 40). Because impaired diastolic function, reduced mechanical efficiency, and risk of thrombosis characteristically concur in patients with nonischemic dilated cardiomyopathy (NIDCM), addressing the physical properties of intraventricular vortices is particularly relevant in this condition. Recent ultrasound (1, 19, 29), computational (28), and phase-contrast magnetic resonance (PC-MR) (3, 6, 11–13) studies have described intraventricular flow characteristics in small numbers of patients with normal and dilated hearts. We hypothesized that significant physiological insights can be gained by comprehensively studying the temporal dynamics and correlates of intraventricular vortex development. We also hypothesized that impaired chamber properties in patients with NIDCM may be associated with modified vortex physiology. Therefore, the present study was designed to characterize the dynamics of vortex position, size, and strength along the cardiac cycle in patients with NIDCM and age-matched healthy control subjects. The physiological relevance of vortices relative to the global LV kinetic energy (KE) balance was also analyzed in detail. We used a custom-developed method that allowed us to measure two-dimensional (2-D) flow using conventional color-Doppler ultrasound (17). Because most previous evidence in this field has been reported using PC-MR, the ultrasound-based method was compared in vivo against this technique in a subset of NIDCM patients.
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Categorías UNESCO
Palabras clave
diastolic function, doppler echocardiography, fluid dynamics
Citación
Centro
Facultad de Ciencias
Departamento
Física Matemática y de Fluídos