Abstract
Background: Intracardiac flow homeostasis requires avoiding blood stasis and platelet activation during its transit through the cardiac chambers. However, the foundations of intraventricular blood washout and its exposure to shear stresses have been poorly addressed. We aimed to characterize and quantify these features in a wide population of healthy subjects and assess the relationships of these indices with age.Methods: We used color-Doppler echocardiography and custom post-processing methods to study 149 healthy volunteers from 26 days to 80 years old. From the intraventricular flow-velocity fields we obtained personalized maps of (1) the residence time of blood in the LV, and (2) the shear index, a metric accounting for the strongest occurrence of shear stresses inside the chamber. From these maps we derived quantitative indices of the overall intraventricular blood washout and shear exposure. We addressed the age-dependence of these indices and analyzed their relationship with age-related changes in filling-flow.Results: The entire intraventricular blood pool was replaced before 8 cycles. Average residence time of blood inside the LV was <3 cycles in all subjects and followed an inverse U-shape relationship with age, increasing from median (IQR) of 1.0 (0.7 to 1.2) cycles in the 1st year of life to 1.8 (1.4–2.2) cycles in young adults (17–30 years old), becoming shorter again thereafter. Shear index showed no relation with age and was bounded around 20 dyn·s/cm2. Regions with the longest residence time and highest shear index were identified near the apex. Differences in the degree of apical penetration of the filling waves and the duration of the late-filling phase explained the age-dependence of residence time ( = 0.48, p < 0.001).Conclusions: In average, blood spends 1 to 3 beats inside the LV with very low shear stress rates. The apical region is the most prone to blood stasis, particularly in mid-aged adults. The washout of blood in the normal LV is age-dependent due to physiological changes in the degree of apical penetration of the filling waves.
Highlights
Cardioembolic stroke is a major source of mortality and disability worldwide and blood stasis one of its major determinants (Adams et al, 1986)
Avoiding stasis and shear stress is a major requirement for the design of Left ventricular (LV) assistance devices and valvular prostheses (Alemu and Bluestein, 2007; Steinlechner et al, 2009), the reference values of these indices have never been reported in the normal heart
We show that blood crosses the normal LV experiencing low shear stresses, being naturally protected against platelet activation
Summary
Cardioembolic stroke is a major source of mortality and disability worldwide and blood stasis one of its major determinants (Adams et al, 1986). An additional requirement of blood flow homeostasis is avoiding the risk of thrombosis inside cardiac chambers. Blood does not transit the LV following a first-in-first-out rule; even in normal hearts, a significant fraction of the blood entering the LV is not ejected during the ensuing systole (Bolger et al, 2007; Eriksson et al, 2011) This fraction increases in diseased hearts, potentially resulting in blood stagnation and eventually thrombosis inside the chamber (Eriksson et al, 2011; Hendabadi et al, 2013; Rossini et al, 2017). Avoiding stasis and shear stress is a major requirement for the design of LV assistance devices and valvular prostheses (Alemu and Bluestein, 2007; Steinlechner et al, 2009), the reference values of these indices have never been reported in the normal heart. We aimed to characterize and quantify these features in a wide population of healthy subjects and assess the relationships of these indices with age
Sign-in/Register to view highlights & summary Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
