Long-term outcomes after continuous-flow left ventricular assist device (LVAD) implantation continue to improve, providing alternatives for patients with advanced heart failure as bridge to transplant or destination therapy in patients who are ineligible for transplantation. However, LVAD implantation may be complicated by early postoperative right heart dysfunction, which is associated with increased morbidity and mortality.1,2 Early postoperative right heart failure may require urgent institution of mechanical right ventricular support. This is conventionally achieved by cannulation of the femoral vein or right atrial appendage for the inflow and the pulmonary artery for the outflow. However, this requires resternotomy with increased risk of wound and device infection, as well as excessive bleeding. We describe the use of peripheral venoarterial extracorporeal membrane oxygenation (ECMO) as short-time right ventricular support after HeartWare (HeartWare Inc., Framingham, MA) LVAD implantation.
A 64-year-old woman with idiopathic-dilated cardiomyopathy was admitted to the cardiothoracic intensive care unit (ICU) due to deterioration of heart failure. Invasive hemodynamic monitoring confirmed biventricular heart failure with cardiogenic shock. Transthoracic echocardiography (TTE) showed impaired left ventricular ejection fraction (LVEF) and mild-to-moderate mitral and tricuspid regurgitation. Laboratory testing was consistent with renal and hepatic impairment. Hemodynamic, echocardiographic, laboratory, and mechanical support parameters are presented in Table 1. Due to borderline age and social factors, LVAD was implanted as a bridge to decision. Preoperative echocardiographic parameters (tricuspid annular plane systolic excursion, right atrial pressure [RAP], and the right ventricle short/long axis ratio) did not demonstrate a high risk of postoperative right ventricular dysfunction3; hence, prophylactic right ventricular support was not implanted.
HeartWare LVAD was implanted through a median sternotomy using cardiopulmonary bypass. The inflow cannula of the pump was inserted into the left ventricular apex and the outflow graft anastomosed to the ascending aorta. Before implantation, medical therapy was successful in reducing RAP to normal levels, and a decision was made not to implant prophylactic mechanical right ventricular support. After weaning from cardiopulmonary bypass, LVAD speed was set at 2,140 revolutions per minute (rpm), which yielded an estimated flow of 4 L/min. Hemodialysis was initiated in the ICU due to oliguria. The patient was extubated 12 hours after surgery. During the hour after extubation, right heart function deteriorated; RAP increased to 25 mm Hg and mixed venous oxygen saturation (ScvO2) decreased to 40%. Intensified inotropic support with increased infusion rates of adrenaline, noradrenaline, and milrinone was ineffective, and the patient was accepted for urgent institution of ECMO as a right ventricular support. During the procedure, the patient developed profound cardiogenic shock with a mean arterial pressure (MAP) of 30 mm Hg.
After a bolus of 7,500 U of heparin was administered intravenously, peripheral venoarterial ECMO with the CentriMag magnetically levitated centrifugal pump (Levitronix, Waltham, MA) was established using the Seldinger technique and direct visualization of the femoral vessels. An 18Fr arterial cannula and a 23Fr venous cannula were used. After establishment of full ECMO support, the LVAD speed was reduced to 1,800 rpm. To reduce the risk of LVAD thrombosis and suction events, we gradually decreased the ECMO flow to allow for sufficient filling of the left ventricle. At the same time, we stepwise increased the LVAD speed to reach a minimum LVAD-estimated flow of 2 L/min. Balance between the two systems was achieved by aiming for an RAP of 10 mm Hg with a maintained adequate filling of the left ventricle, keeping the interventricular septum in a midline position. This was assessed by transesophageal echocardiography. In our patient, these conditions were fulfilled at ECMO flow of 2.3 L/min and LVAD speed of 1960 rpm generating a flow of 2 L/min. Using this setup, there were no suction events during the support and opening of the aortic valve occurred at a 1:2 ratio. During the ICU stay, TTE was performed once daily to examine the filling of the ventricles and thereby to guide ECMO and LVAD configurations. Activated partial thromboplastin time (APTT) was maintained between 50 and 55 seconds during ECMO support.
The need for ECMO support was assessed daily by transthoracic echocardiographic evaluation of the right ventricular function during reduction of ECMO flow. Four days after implantation, we initiated weaning of the ECMO system. Under transesophageal echocardiographic and hemodynamic monitoring, ECMO flow was initially decreased to 1 L/min and then completely clamped for 50 minutes with no changes in MAP, RAP, pulmonary arterial pressure (PAP), ScvO2, or visual right ventricular function. Left ventricular assist device speed was increased to 2,200 rpm, estimated flow increased from 2 to 3.1 L/min, and the ECMO cannulas surgically removed without complications. There were no groin complications during or after ECMO support. Both RAP and PAP were unchanged after ECMO removal. Renal and hepatic function normalized during ECMO support according to laboratory testing. During the remaining hospital stay, LVAD speed was increased to 2,440 rpm, which yielded an estimated flow of 4–4.8 L/min. The patient was transferred from the ICU after 42 days and discharged after another 3 weeks. Transthoracic echocardiography at discharge showed LVEF 15% and a slightly improved right heart function with decreased right ventricular dilatation and improved estimated right ventricular ejection fraction.
Development of right heart failure after LVAD implantation is multifactorial.1 After LVAD implantation, cardiac output and right ventricular preload increase and unloading of the left ventricle contributes to leftward shift of the interventricular septum, thereby reducing the contractile capacity of the right ventricle. These effects together with factors associated with concealed right ventricular failure such as impaired right ventricular geometry and moderate tricuspid valve regurgitation might coalesce into overt postoperative right heart failure, despite inotropes and pulmonary vasodilators.
Standard treatment is currently cannulation of the femoral vein or right atrial appendage for the inflow and the pulmonary artery for the outflow.4 This strategy has been further improved by subxiphoid tunneling of the outflow graft, which allows for no resternotomy when right ventricular support is removed.5 However, both these strategies require resternotomy for implantation with subsequent increased risk of wound and device infection, as well as excessive bleeding. Peripheral venoarterial ECMO using femoral cannulation is an alternative, less-invasive approach, which can be easily instituted and removed without requiring resternotomy. In addition, this strategy allows for urgent bedside implantation and oxygenation in case of hypoxemia.
However, a major potential drawback is competing flows between the ECMO and LVAD circuits, which is a risk factor for ECMO and LVAD thrombosis and thromboembolism. Left ventricular assist device thrombosis is a severe complication associated with high mortality and requires systemic thrombolysis or pump exchange.6 To lower the risk of these complications, LVAD-estimated flow was maintained above 2 L/min and APTT within the interval 50–55 seconds.
Peripheral ECMO has earlier been used as a perioperative right heart support in patients undergoing LVAD implantation.7,8 In these reports, peripheral ECMO was instituted before or during LVAD implantation to prevent postoperative right heart dysfunction, with no reported complications related to competing flows. The use of peripheral ECMO as urgent treatment of overt right heart failure after LVAD implantation has previously been described.9 However, in this previous case, it was not described how circulatory support competing flows were managed during ECMO support.
In summary, peripheral venoarterial ECMO could be used as treatment of acute right heart failure after HeartWare LVAD implantation. The strategy is less invasive than cannulation of the pulmonary artery, and therefore, the risk of wound and device infection and excessive bleeding is lowered. However, the strategy requires careful monitoring of LVAD flows and APTT to prevent LVAD thrombosis.
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