HeartMate XVE malfunction caused by fluid aspiration into the vent port

Abstract

therapy in patients with advanced heart failure. 1 Malfunction of the LVAD, however, might significantly reduce the survival benefit it incurs. Seven of 41 deaths in patients with LVADs in the REMATCH trial (Randomized Evaluation of Mechanical Assistance for the Treatment of Congestive Heart Failure) were attributed to device malfunction. 1 We present the case of a patient who had an unusual device complication. Fluid was aspirated into the vent port, resulting in the malfunction of the device and a clinical emergency. A treatment algorithm for this challenging problem is described. Clinical Summary A 55-year-old man (6'5, 183 lb) with idiopathic dilated cardiomyopathy had a HeartMate XVE (Thoratec Corp, Pleasanton, Calif) LVAD system implanted. He was convalescing on a stepdown ward 3 weeks postoperatively, with stable LVAD flows of between 5 and 6 L/min. The patient was incontinent of urine at 5 AM on the day of the event. Urine was aspirated into the LVAD vent port. The low flow and power limit advisory alarms of the LVAD activated. The low flow persisted, and the patient became hemodynamically unstable. The vent filter was immediately removed, and the patient was placed on his right side, enabling fluid drainage from the vent port. A dry towel was also used to absorb the remaining fluid at the vent port. After several minutes in this position, the alarms stopped, and the LVAD flow returned to previous levels. A new vent filter was placed, and the patient’ s condition remained stable. The patient experienced the same malfunction again at 9 AM. The device then stopped, and hand pumping was initiated. Electrical activation was not possible. The patient was systemically anticoagulated. He was transferred to the intensive care unit, and arterial line and pulmonary artery catheters were placed for monitoring. The system controller and power source were removed, and the LVAD was successfully activated with the older pneumatic HeartMate driver. This driver was used with a pressurelimiting device on the pneumatic driveline to avoid injury to the electric pump, as recommended by the company. The pneumatic driver rate was increased to 90 beats/min. The patient, however, remained in shock, and respiratory distress ensued. He was mechanically ventilated, and inotropic infusions were initiated to enhance native ventricular function. Despite these maneuvers, the patient was hypotensive, with a central venous pressure of 22 mm Hg and a cardiac output of 2.3 L/min, as measured with the pulmonary artery catheter and the thermodilution method. Metabolic acidosis was present on the arterial blood gases. The arterial pressure tracing suggested poor LVAD stroke volume, and native ventricular ejection confirmed incomplete ventricular unloading by the pneumatically driven HeartMate LVAD. A decision was made to replace the LVAD surgically at 11 AM given the patient’ s persistent shock state. At this point, a final attempt was made to reactivate the pump electrically. Fortunately, the pump could be electrically activated and subsequently functioned without alarms. The patient’ s hemodynamics rapidly normalized: central venous pressure was 8 mm Hg, and cardiac output increased to 5.3 L/min. The need to surgically replace the pump was averted. The device continued to function electrically without