The HeartMate II left ventricular assist device (LVAD) is a small next-generation blood pump. Blood is propelled through this continuous-flow VAD by a turbine-like axial flow rotor spinning at approximately 9000 rpm, eliminating the need for valves during normal operation.
The HeartMate II has been extensively studied since 2004 and has been approved by the Food and Drug Administration for use in bridge-to-transplant (BTT) indication while undergoing ongoing evaluation for use in destination therapy (DT).1 More than 3000 individuals worldwide have been implanted with the HeartMate II. Overall outcomes have been quite good with 80% of patients surviving 180 days with their pump, to transplant, or to recovery, and there are individuals who have survived for more than 4 years on a single implanted device.2,3
Overall freedom from device failure with the HeartMate II has been quite good. However, the management of abrupt stoppage of the LVAD when it does occur remains problematic because of acute regurgitation of blood (analogous to severe aortic valve insufficiency, possibly at a rate of 1–1.5 L/min) passing retrograde from the aorta through the stopped, valveless rotor-driven VAD, acutely overloading a chronically failed LV. We briefly report two cases of acute failure of a HeartMate II LVAD in which percutaneous interruption of regurgitant blood flow through the stopped VADs was used for stabilization allowing elective LVAD exchange.
The first case involved a 44-year-old man with an ischemic cardiomyopathy who was implanted successfully with a HeartMate II as a BTT in November 2008. He did well as an outpatient, except for worsened obesity, gaining 35 pounds. Five months after implantation, he experienced sudden onset of red heart alarms from his HeartMate II LVAD system controller associated with pump stoppage (confirmed with a power base unit), and the HeartMate II could not be restarted. In retrospect, intermittent alarms increasing in frequency in the days preceding this event may have been an early indicator of impending failure.
The patient was transferred emergently via air transport from a rural facility to the implanting center with cardiogenic shock. He was experiencing progressive hypotension, shortness of breath, and severe unrelenting chest pain. Evaluation of the percutaneous lead by x-ray demonstrated acute angulation at the point of insertion into the body of the pump, raising concern about fractured internal wire leads (Figure 1).
Because of unavailability of surgical services for immediate, emergent VAD replacement and progressive hemodynamic deterioration, a decision was made to emergently stabilize the patient by percutaneous, endovascular means with the intention of interrupting acute regurgitation of blood through the VAD. An approach to occlude the outflow graft of the LVAD with a large peripheral balloon was planned.
Vascular access was secured and hemodynamic monitoring established with a continuous output pulmonary artery catheter. Through an 8F sheath in the right femoral artery, a 300-cm Supra Core 0.035-inch wire (Abbott Vascular, Santa Clara, CA) was navigated into the outflow graft without difficulty. The 15-mm Dacron outflow graft of the LVAD had been anastamosed to the right anterolateral aspect of the proximal ascending aorta approximately 3–5 cm above the aortic valve in an end-to-side fashion analogous to a right coronary bypass graft. Over this wire, a 14 × 40 mm Maxi LD balloon (Cordis Corporation, Warren, NJ) was seated deeply into the outflow graft just distal to the junction of the graft to the LVAD and inflated to nominal pressure (Figure 2). A 6F multipurpose catheter (MPA) passed through a 7F sheath over a standard 0.035 J-tipped guidewire into the aorta for the performance of an aortogram. Near total occlusion of the graft with only a trace of contrast around the balloon was noted. The balloon was left inflated and the balloon, wire, and insufflation device were secured in place. Hemodynamic stabilization was supported with an intra-aortic balloon pump initially and percutaneous cardiopulmonary support subsequently. Four days after presentation, the patient was taken to the operating room electively where the HeartMate II with a failed percutaneous lead was successfully replaced with another HeartMate II. The patient was successfully discharged from the hospital at 3 weeks postoperatively. His outpatient course has been unremarkable.
The second case involves a 51-year-old man who was implanted with the HeartMate II in a BTT indication in November 2008 for severe ischemic cardiomyopathy with an ejection fraction of 10–15% and dependent on inotropic support. His postoperative course was notable for right heart failure requiring prolonged support with milrinone that was eventually successfully weaned. He required a limited midline abdominal wound revision for dehiscence without infection in January 2009. He enjoyed an extremely active lifestyle as an outpatient. Despite an increased activity level and advice to the contrary, he gained 31 kg (68 lbs) of body weight over approximately 6 months.
Six months after implantation, the patient experienced sudden alarms from his HeartMate II system controller. This occurred immediately after rolling over in bed. He described a “shuddering” feeling in his abdomen over the location of the pump. He was already connected to the power base unit (PBU), which reported pump stoppage. He immediately contacted coordinators and emergency medical services (EMS) personnel and was airlifted to the implant center. On arrival, he was conscious but complaining of breathlessness of moderate severity. Abdominal films revealed a percutaneous lead fracture at the insertion into the body of the pump. Continuity testing of the lead demonstrated discontinuity of all three leads contained within the driveline.
Again, because of the unavailability of surgeons with LVAD experience, the decision was made to proceed with emergent endovascular stabilization. The procedure details are similar to the first case with the following exceptions. First, the second patient had a known 100% occlusion of the right common femoral artery by computed tomography angiography. Second, a 10F sheath was placed in the left femoral artery and a 16 × 40 mm Maxi LD balloon was used to achieve complete occlusion of the graft. This was secured in similar fashion; however, before securing the balloon, a 5F sheath was placed antegrade in the left superficial artery to prevent arterial insufficiency to the left lower extremity. The last major difference in cases is that the patient was taken to the operating room for surgical stapling of the graft through a limited right anterior thoracotomy. This was necessary because of the unavailability of dual femoral artery access sites to accommodate the balloon and the percutaneous cardiopulmonary support. Three days after presentation, his HeartMate II LVAD was successfully replaced. He was successfully discharged approximately 3 weeks after his operation and has had an unremarkable outpatient course.
These two cases represent the first reported cases of abrupt stoppage of HeartMate II LVADs where emergent stabilization through endovascular means was used. From a technical standpoint, the stabilization procedure is fairly simple. A 14–16 mm peripheral balloon taken over a stiff wire through the aorta into the graft is basically all that is required to reduce the acute, severe aortic insufficiency. Bilateral femoral access is needed to have the balloon secured in one femoral artery site and the contralateral femoral artery site available for a cardiopulmonary circuit if needed. We recognize that the ideal therapeutic strategy is to take the patient directly to the operating room for emergent replacement; however, in many instances this is not possible. In some cases, a short course of hemodynamic stabilization with the opportunity for increased organ perfusion before LVAD replacement may be helpful.
As LVADs continue to proliferate, there will be an ever- increasing population of LVAD patients. Many of these patients will not live in the same city as the implant center; therefore, interventional cardiologists in facilities with a catheterization laboratory but without LVAD services may come into contact with acutely ill patients whose device may have stopped. Communication with the implanting center followed by initial stabilization will be of paramount importance in the patient's survival. Once the patient is stabilized, they can be safely transported to the implant center for definitive surgical replacement therapy.
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