Conventional and alternative sites for left ventricular assist device inflow and outflow cannula placement

Planned Combo Strategy for LVAD Implantation in ECMO Patients: A Proof of Concept to Face Right Ventricular Failure

We propose a patient-tailored strategy that considers the risk for postoperative right heart failure, utilizing the percutaneous ProtekDuo cannula (Livanova, London, UK) in an innovative way to perform cardiopulmonary bypass during LVAD implantation in ECMO patients. Our novel protocol is based on the early intra-operative use of the ProtekDuo cannula, adopting the distal lumen as the pulmonary vent and the proximal lumen as the venous inflow cannula during cardiopulmonary bypass. This configuration is rapidly switched to the standard fashion to provide planned postoperative temporary right ventricular support, in selected patients at high risk of right ventricular failure. From September 2020 to June 2022, six patients were supported with the ProtekDuo cannula during and after an intracorporeal LVAD implantation (five of which were minimally invasive): four HeartMate III (Abbott, U.S.A.) and two HVAD (Medtronic Inc, MN). In all cases, the ProtekDuo cannula was correctly positioned and removed without complications after a median period of 8 days. Non-fatal bleeding (bronchial hemorrhage) occurred in one patient (17%) during biventricular support. Thirty-day mortality was 0%. From this preliminary work, our novel strategy demonstrated to be a feasible solution for planned minimally invasive right ventricular support in ECMO patients scheduled for a durable LVAD implantation.

Left subclavian artery as an alternative site for left ventricular assist device outflow graft in challenging situations

Left ventricular assist device (LVAD) has emerged as an effective surgical therapy for end-stage heart failure. In an attempt to reduce invasiveness and avoid difficult sternal re-entries, alternative surgical approaches have been adopted. In particular, when the thoracic aorta is severely diseased or difficult to expose, subclavian arteries could serve as site for outflow graft anastomosis. However, major concerns regarding the utilization of subclavian arteries are the small caliber of these vessels that could lead to inadequate LVAD flow, arm complications related to excessive blood flow, and possible outflow graft compression. In the present case series, we describe an innovative technique for LVAD implantation, in which the left subclavian artery was employed as an outflow graft anastomosis site, and the left ventricular apex was approached through a mini-thoracotomy. Technical issues were considered to prevent possible complications: the adequacy of left subclavian artery diameter, the banding of the artery distal to the anastomosis site to limit left arm overflow, and the outflow graft covering with a reinforced vascular graft to avoid any external compression. During follow-up, the technique reported was found to be effective in ensuring good LVAD function and flow, and no complications related to the procedure were reported.

Flow assessment as a function of pump timing of tubular pulsatile pump for use as a ventricular assist device in a left heart simulator

INTRODUCTION

Although mechanical circulatory support saved many lives during the last decade, clinical observations have shown that the continuous flow pumps are associated with a much higher incidence of gastrointestinal bleeding and kidney problems, among others, compared with the earlier generation pulsatile pumps. However, the presence of several moving mechanical components made pulsatile pumps less durable, bulky, and prone to malfunction, ultimately leading to bias in favor of continuous flow designs.

OBJECTIVE

The aim of the current work is to create a prototype tubular pulsatile pump and to test the timing of the pump in a left heart simulator.

METHODS

A left heart simulator to mimic pumping from a failing heart was created. This was used to experimentally test the output of a prototype ventricular assist device relative to a failing heart in the form of flow and pressure. The effect of pulsation timing was quantified.

RESULTS

A failing heart was simulated with an average flow rate of 1.1 L/min and a systolic pressure of 47 mmHg. With the pump, the flow rate increases to 4.8 L/min and a systolic pressure of 110mmHg, in a copulsation mode, while activating for 300-400 ms. If the activation time is reduced, or increased, the pump becomes less effective. Load on the heart is reduced when the pump operates in a counterpulsation mode.

CONCLUSION

A pulsatile pump, like the one proposed, provides adequate output for mechanical circulatory support, while minimizing the number of moving parts that could otherwise lead to tribological wear.