Use of Pulmonary Arteriovenous Extracorporeal Membrane Oxygenation in Conjunction with the Total Artificial Heart

Abstract

The temporary total artificial heart (TAH-t) is approved for destination therapy or bridge to transplant and is associated with improved survival rates before and after transplantation [1]. Postoperatively, patients with the TAH-t may experience acute respiratory failure requiring significant respiratory support. Pulmonary arteriovenous extracorporeal membrane oxygenation (ECMO) has the capabilities to provide this support while minimizing the risks of barotrauma or oxygen toxicity [2]. This report presents a novel cannulation technique for ECMO to provide support for patients after the placement of the TAH-t.

Introduction

The temporary total artificial heart (TAH-t) is approved as a bridge to cardiac transplant and destination therapy for end-stage heart failure in patients with severe biventricular dysfunction [1]. Implantation of the TAH-t has been shown to improve the rate of survival to cardiac transplantation along with survival rates after transplantation [2]. However, after implanting the TAH-t the patient may develop pulmonary edema with acute respiratory failure and require increased respiratory support. Airway pressures and oxygen concentrations required to support patients with severe respiratory failure may result in barotrauma and oxygen toxicity which may prevent lung recovery [2]. Extracorporeal membrane oxygenation (ECMO) can serve as an alternative in providing temporary pulmonary support for TAH-t patients in respiratory distress. This case describes a unique form of ECMO cannulation to provide support after the placement of the TAH-t to treat a patient with acute respiratory failure.

Case History

A 54 year-old male presented with angina, renal failure and hemolysis related to thrombosis of a left ventricular assist device (LVAD). His history was significant for ischemic cardiomyopathy, NYHA III systolic heart failure treated with placement of a Heartmate II LVAD, and two LVAD exchanges related to microthrombi. Implantation of a TAH-t was recommended as a bridge to transplantation. Preoperative catheterization demonstrated normal pulmonary vascular resistance. He underwent TAH-t implantation and was subsequently removed from cardiopulmonary support without immediate hemodynamic compromise, but quickly developed florid pulmonary edema leading to respiratory decompensation. The patient became profoundly hypercarbic and hypoxic despite paralysis, 100% FiO₂ and PEEP 12. The left-sided filling of the TAH-t became compromised due to decreased blood flow through the pulmonary circuit with central venous pressures as high as 24.

After marginal efficacy of inhaled nitric oxide, ECMO was recommended to provide respiratory support. A 24F EOPA arterial cannula (Medtronic, Minneapolis, MN) was placed in the patient’s pulmonary artery for venous drainage and blood was returned via an 18F DLP single-stage venous cannula (Medtronic, Minneapolis, MN) to the right superior pulmonary vein which resulted in pulmonary arteriovenous ECMO, bypassing the lungs (Figure 1). The sternum was left open for the duration of ECMO support. ECMO sweep was initiated at 3 L/min and pump flow was 5 L/min using a Rotaflow pump with an in-line Quadrox-I oxygenator (both Maquet, Bridgewater, NJ). Anticoagulation was maintained on heparin with activated clotting time (ACT) targets of 160-180 seconds initially, and then liberalized to 180-200 seconds once bleeding was controlled. The patient remained intubated, but the ventilator was weaned to 30% FiO₂ and PEEP 8 for pulmonary rest.

Figure 1.

Chest radiograph showing position of the ECMO cannulas. A) 18F DLP single stage venous cannula in the right superior pulmonary vein. B) 24F EOPA arterial cannula in the pulmonary artery. Arrows depict directionality of blood flow through the cannulas.

The patient was hemodynamically stable and supported with a combination of pulmonary arteriovenous ECMO and the TAH-t for five days. ECMO sweep was maintained between 2.5 and 4.7 L/min and pump flow between 2.5 and 3.5 L/min. On ECMO day 5, the patient tolerated a trial off ECMO for 90 minutes. He was decannulated in the intensive care unit and well-supported by the TAH-t and mechanical ventilation. Heparin infusion (goal ACT 180-200 seconds) was continued while still ventilated, until transition to coumadin was possible. After six months, the patient successfully underwent cardiac transplantation and has since been discharged from the hospital.

Discussion

The use of ECMO with TAH-t has previously been described. In 2009, a patient experiencing pulmonary edema after the placement of TAH-t was cannulated via aorta and right atrium and placed on venoarterial ECMO [2]. Venovenous (VV) ECMO in conjunction with the TAH-t has also been reported in a patient with respiratory failure after TAH-t placement [4]. The treatment of our patient demonstrates a new cannulation technique in which pulmonary arteriovenous ECMO can be used as temporary therapy for acute respiratory failure after TAH-t implantation. This form of ECMO enables adequate filling of the left-sided TAH-t while simultaneously allowing for lung rest in the face of elevated pulmonary vascular resistance (PVR).

Our patient required 5L pump flow to maintain proper TAH-t filling pressures. We were concerned that use of VV ECMO with such high pump flows may increase the risk of recirculation, although, this was not the case with 4L pump flow in the report by Spiliopoulos et al [4]. Our technique allowed blood to return directly into the right superior pulmonary vein, which effectively increasing volume available to the left side of the TAH-t for ejection and avoiding recirculation.

This case illustrates the benefit of combining TAH-t with pulmonary arteriovenous ECMO to safely support patients after TAH-t implantation. By using this form of ECMO, the patient was able to receive the pulmonary support required, while minimizing recirculation, barotrauma and oxygen toxicity. Most importantly, pulmonary arteriovenous ECMO in patients with the TAH-t provides a means to bypass the lungs in cases of high PVR and limit their exposure to high flows from the right side of the TAH-t.