In Vitro Evaluation of Ventricular Cannulation for Rotodynamic Cardiac Assist Devices

Abstract

The influence of positioning and geometry of ventricular cannulas for contemporary continuous flow Left Ventricular Assist Devices (LVADs) was evaluated in a non-beating isolated heart preparation with borescopic visualization. Preload and LVAD flow were varied to evaluate degrees of ventricular decompression up to the point of ventricular collapse. The performance of a flanged cannula was compared to a conventional bevel-tipped cannula: quantitatively by the maximal flow attainable, and qualitatively by visualization of fluid tracer particles within the ventricular chamber. Three forms of ventricular suck-down occurred: concentric collapse, gradual entrainment and instantaneous entrainment. In some circumstances, unstable oscillations of the ventricle were observed prior to complete collapse. Under conditions of low preload, the flanged cannula demonstrated less positional sensitivity, provided greater flow, and exhibited fewer areas of stagnation than the beveled cannula. These observations warrant further consideration of a flanged ventricular cannula to mitigate complications encountered with conventional cannulae.

Numerical Simulation of LVAD Inflow Cannulas with Different Tip

“…The effective numerical prediction of mechanical hemolysis has been built [13][14][15]. In vitro and in vivo mechanical hemolysis tests have been studied previously [16][17][18]. To obtain a good performance in blood compatibility, the tip shape is the crucial factor to reduce static and vortical flow area in an inflow cannula design.…”

Ex Vivo Assessment of a Parabolic-Tip Inflow Cannula for Pediatric Continuous-Flow VADs

“…The ability to visualize and quantify ventricular ‘suck-down’ makes this a reasonably simple and accurate method for assessing cannula performance, but there are several limitations to this ex vivo isolated heart setup described in detail by Bachman et al 17 Most notably, it is impossible to replicate directly on the benchtop the thrombogenic, thromboembolic, or pannus potential that in vivo assessment could provide. The addition of the new solenoid pinch valve cycling at 1.0 Hz (60 beats/min) to control LV preload induced measurable pulsatility (unsteady flow) and led to visible contraction of LV chamber.…”

“…Both protocols were executed in normal and misaligned positions to assess positional sensitivity, with misalignment created by fixing the cannula posteriorly approximately 45 degrees. 17 …”

“…The percent change in flow rate caused by misalignment, termed as the positional sensitivity index (I ps ) was calculated using the following equation: $$\text{italicIps}=\frac{Q-Q\prime }{Q}\ast 100\%$$ for the maximum flows attained in the over-pumping protocol and flows at certain LAPs in the hypovolemic protocol for each cannula, where Q is the flow rate of a normally aligned cannula and Q’ is the flow rate when misaligned. 17 Statistical analysis was performed by one-way and repeated measures ANOVA with Bonferroni post hoc tests using SPSS® v23.0 (IBM® Corp, Armonk, NY), with significance assumed at p<0.05.…”

“…17 Equal reduction of the LV wall around the cannula was categorized as “Concentric Collapse”, while entrainment was defined in three categories: partial, gradual, and severe. “Partial Entrainment” is defined as the blocking of only a portion of the cannula orifice, while the remaining is unrestricted to flow.…”