Left Ventricular Assist Device Thrombosis Is Associated With an Increase in the Systolic-to-Diastolic Velocity Ratio Measured at the Inflow and Outflow Cannulae

Echocardiography for left ventricular assist device implantation and evaluation: an indispensable tool

Echocardiography is an indispensable tool in the evaluation, placement, management and follow-up of patients with left ventricular assist devices (LVAD). While transoesophageal echocardiography is the ideal tool in guiding the implantation procedure, transthoracic echocardiography is essential during the initial evaluation, patient selection and in the post-operative follow-up. This review attempts to summarize which parameters the echocardiographic assessment should focused on during each step. In particular, during the pre-operative assessment, it is of paramount importance to assess the presence of aortic regurgitation and most importantly to evaluate right ventricular function, since it is one of the strongest predictor of post-implant right ventricular failure. During the procedure, through transoesophageal echocardiography, it is possible to confirm the correct placement of the inflow cannula, to assess right ventricular function and to guide the choice of the right pump speed. Transthoracic echocardiographic is an essential part in the patient's follow-up once the LVAD has been implanted, in order to attest the onset of possible complications.

The Effect of Inflow Cannula Angle on the Intraventricular Flow Field of the Left Ventricular Assist Device-Assisted Heart: An In Vitro Flow Visualization Study

Previous studies have identified left ventricular assist device (LVAD) inflow cannula (IC) malposition as a significant risk for pump thrombosis. Thrombus development is a consequence of altered flow dynamics, which can produce areas of flow stasis or high shear that promote coagulation. The goal of this study was to measure the effect of IC orientation on the left ventricle (LV) flow field using a mock circulatory loop, and identify flow-based indices that are sensitive measures of cannula malposition. Experimental studies were performed with a customized silicone model of the dilated LV and the EVAHEART Centrifugal LVAS (Evaheart, Inc.; Houston TX). The velocity field of the LV midplane was measured for a transparent IC oriented parallel to and rotated 15° toward the septum under matched hemodynamic conditions. Vortex structures were analyzed and localized stasis calculated within the IC and combined with a map of normalized pulsatile velocity. The velocity fields revealed increased apical stasis and lower pulsatility with a small angulation of the IC. A significant change in vortex dynamics with the angled IC was observed, doubling the size of the counterclockwise (CCW) vortex while reducing the kinetic energy provided by LVAD support. A significant decrease in average and systolic velocities within the IC was found with cannula angulation, suggesting an increased resistance that affects primarily systolic flow and is worsened with increased LVAD support. These common echocardiographic indices offer the opportunity for immediate clinical application during ramp study assessment. Optimized IC positioning may be determined preoperatively using imaging techniques to develop patient-specific surgical recommendations.

A Comprehensive Imaging Approach to Guide the Management of Patients with Continuous-Flow Left Ventricular Assist Devices

Recent advances in mechanical circulatory support have allowed patients with end-stage heart failure to be successfully bridged to heart transplantation or live for many years on continuous-flow left ventricular assist devices (CF-LVADs) as destination therapy. As survival and quality of life continue to improve and the number of patients supported by CF-LVADs continues to grow, utilization of different imaging modalities in the care for these patients has become an integral part of many heart failure centers. We review currently available imaging modalities, with a focus on echocardiography, that aid to diagnose and manage common adverse events associated with CF-LVADs.

Looking inside the third generation left ventricular assist device using color doppler transesophageal echocardiography

HeartWare is a third-generation continuous flow left ventricular assist device (LVAD) and generates centrifugal pattern of blood flow. In the perioperative setting, interrogating the HeartWare devices is very difficult due to the interference of the Doppler by the impeller frequency and generation of the waterfall artifact. We present a case where using color Doppler a view "inside" the impeller can be seen which corresponds to the centrifugal flow of blood. With time, these images can be looked into in pathological states such as pump thrombosis, to come to a more meaningful conclusion regarding the flow of blood within the centrifugal chamber. Newer technologies are constantly evolving to give us more meaningful insights into the flow of blood within the heart chambers. We believe similar technologies can be applied to see the flow of blood inside the LVAD devices.