Tolerance of Sustained Ventricular Fibrillation During Continuous-Flow Left Ventricular Assist Device Support.

The widespread use of continuous-flow left ventricular assist devices for mechanical circulatory support has shown that long-term hemodynamic support is possible, even when a clinical "pulse" cannot be detected. We present the incidental discovery of ventricular fibrillation in 6 alert, hemodynamically stable patients supported only by a continuous-flow device (HeartMate II, n=5; Jarvik 2000, n=1). Ventricular fibrillation was found in 3 patients during routine outpatient follow-up visits and in 3 awaiting discharge from the hospital after device placement. Diagnosis was confirmed by electrocardiographic and echocardiographic studies. The average duration of mechanical circulatory support before ventricular fibrillation occurred was 221 ± 362 days (range, 5-864 d). All patients were conscious and ambulatory at the time of the arrhythmia. Three patients reported symptoms-primarily fatigue, nausea, and exertional dyspnea-that prompted evaluation. Serum chemistry analysis of blood drawn immediately after diagnosis showed no changes that suggested end-organ dysfunction. Three patients died of unrelated complications an average of 3.9 yr (range, 360-2,270 d) after the event. Two of the remaining 3 patients eventually underwent successful pump explantation, and one is on ongoing support. Our experience shows that it is possible for patients with continuous-flow left ventricular assist devices to remain hemodynamically stable while in ventricular fibrillation. Additional investigation is needed to determine whether defibrillator settings for these patients should be adjusted to limit delivery of shock therapy.

Nonidentical Continuous-Flow Devices For Biventricular Support.

Although biventricular heart failure has been successfully managed with dual continuous-flow ventricular assist devices, the long-term use of 2 mechanically dissimilar pumps has traditionally been discouraged. We present the case of a 52-year-old man whose treatment with a HeartMate II left ventricular assist device was complicated by right ventricular failure, necessitating the implantation of a long-term right ventricular assist device. A HeartWare left ventricular assist device was placed along the right ventricular base to avoid interference with the HeartMate II housing. The patient was discharged from the hospital after routine postoperative care and dual-device training. This case shows that, despite logistical complexities, nonidentical continuous-flow device pairings can successfully provide long-term biventricular support.

State of the art of mechanical circulatory support.

Mechanical circulatory support of the failing heart has become an important means of treating end-stage heart disease. This rapidly growing therapeutic field has produced impressive clinical outcomes and has great potential to help thousands of otherwise terminal patients worldwide. In this review, we examine the state of the art of mechanical circulatory support: current practice, totally implantable systems of the future, evolving biventricular support mechanisms, the potential for myocardial recovery and adjunctive treatment methods, and miniaturized devices with expanded indications for therapy.

Clinical experience with the TandemHeart percutaneous ventricular assist device as a bridge to cardiac transplantation.

Cardiac support with a ventricular assist device is among the few treatments for heart-failure patients who have profound cardiogenic shock unresponsive to vasopressors and intra-aortic balloon pumps. The TandemHeart percutaneous ventricular assist device can provide temporary support until another device can be placed or a donor heart becomes available. We examined the TandemHeart's effect on cardiac index, central venous pressure, mixed venous oxygen saturation, creatinine, mean arterial pressure, urine output, and 30-day mortality rate in 5 heart-failure patients (2 with nonischemic and 3 with ischemic cardiomyopathy; mean preoperative left ventricular ejection fraction, 0.17 +/- 0.056). Two patients were undergoing cardiopulmonary resuscitation when the device was inserted. The average duration of TandemHeart support was 7.6 +/- 3.2 days; all patients were successfully bridged to transplantation. The TandemHeart improved the cardiac index (1.9 +/- 0.3 vs 3.5 +/- 0.8 L/[min.m2], P= 0.01), mean arterial pressure (69 +/- 12.5 vs 91 +/- 4.3 mmHg, P=0.009), mixed venous oxygen saturation (45.4 +/- 14.3 vs 71.4 +/- 7.5, P=0.009), and urine output (1,861 +/- 988 vs 4,314 +/- 1,346 mL/hr, P=0.01). The device decreased central venous pressure (21.2 +/- 7.4 vs 12.8 +/- 5.9 mmHg, P=0.02) and pressor requirements (2.4 +/- 1.1 vs 1.0 +/- 0.7 agents, P=0.02). Average long-term follow-up after heart transplantation was 8.4 +/- 9.9 months, with no deaths. We conclude that the TandemHeart can provide hemodynamic support for patients with profound, refractory cardiogenic shock. Furthermore, the device can bridge patients to cardiac transplantation and can be placed percutaneously, without invasive surgery.

In vivo evaluation of the HeartWare centrifugal ventricular assist device.

In this study, long-term (90-day) hemocompatibility and end-organ effects of a centrifugal left ventricular assist device (the Heartware HVAD) were evaluated in 6 healthy sheep. The device was implanted into the left ventricular apex on beating hearts. The outflow graft of each device was anastomosed to the descending aorta. None of the sheep received anticoagulation or antiaggregation medication during the study. Hematologic and biochemical tests of liver and kidney function were performed pre-operatively (baseline) and throughout the study. Data associated with pump function were collected continuously until 90 +/- 1 days of support, at which time the sheep were humanely killed, and the end-organs were examined macroscopically and histopathologically. Hematologic and biochemical test results were within normal limits during the study period. There were no significant complications. Postmortem examination of the explanted organs revealed no evidence of ischemia or infarction, except in 2 sheep, in which small foci of infarction were detected in each of their left kidneys. There was no significant device failure. In all sheep, the pump's inflow and outflow conduits were free of thrombus. During the 90-day study, the HeartWare HVAD showed exceptional hemocompatibility and reliability, both of which are crucial to the clinical success of any implantable left ventricular assist device.