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Ann Thorac Surg 2001;71:S121-S124
© 2001 The Society of Thoracic Surgeons
a Allegheny General Hospital, Pittsburgh, Pennsylvania, USA
b Johannesburg General Hospital, Johannesburg, South Africa
c The Ohio State University Medical Center, Columbus, Ohio, USA
d the John Radcliffe Hospital, Oxford, England, United Kingdom
Address reprint requests to Dr Magovern, Department of Cardiothoracic Surgery, Allegheny General Hospital, 320 E North Ave, Pittsburgh, PA 15212
e-mail: jmagover{at}wpahs.org
Presented at the Fifth International Conference on Circulatory Support Devices for Severe Cardiac Failure, New York, NY, Sept 15–17, 2000.
Abstract
Background. This report reviews the initial clinical experience with the AB-180 ventricular assist device.
Methods. Between Dec 1997 and July 2000, the AB-180 was implanted in 17 patients at five institutions. The mean age was 52 years (range 21 to 68 years) and 14 of 17 were male. The indications for implantation were postcardiotomy shock (12 of 17, 70%), decompensated cardiomyopathy (2 of 17, 12%), viral myocarditis (2 of 17, 12%), and acute myocardial infarction (1 of 17, 6%).
Results. The mean duration of support was 8.5 days (range 1 to 28 days). In the group of 17 patients, 8 were weaned from the device and 2 underwent transplantation. Four of the weaned patients (4 of 8, 50%) and 1 of the transplant patients (1 of 2, 50%) survived. The overall weaning and survival rates were 58% (10 of 17) and 29% (5 of 17). There were no major device-related complications and no major device malfunctions.
Conclusions. The AB-180 provides reliable circulatory support for reversible forms of heart failure.
The AB-180 is an implantable, centrifugal flow left ventricular assist device (LVAD) for treatment of reversible forms of acute or chronic heart failure. The intended uses are for treatment of patients with inadequate hemodynamics after heart surgery, acute fulminant myocarditis, or shock after myocardial infarction. Previous reports have outlined the technical details of the pump and reported the preliminary experimental animal data [1, 2]. This report summarizes the worldwide clinical experience as of July 1, 2000 with the device.
Material and methods
Description of the device
The AB-180 (Cardiac Assist Technologies, Inc, Pittsburgh, PA) is a centrifugal flow ventricular assist device that weighs approximately 280 g and has a priming volume of 7 mL (Fig 1). The pump is powered by a stationary electromagnetic motor that drives a magnetic rotor and an impeller, which rotates at 2,700 to 4,700 rpm. Pump inflow is provided by a plastic cannula that enters the pump at 180° from the impeller. Outflow leaves the pump at 90° from the inflow. A 10-mm thin-walled polytetrafluoroethylene (PTFE) graft connects to an outflow port and is anastomosed to the aorta. The device can pump up to 6 L/min at a mean arterial pressure of 60 to 90 mm Hg provided there is adequate left atrial pressure (> 5 mm Hg) to fill the pump.
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The pump controller is contained in an external console, which is located adjacent to the patient (Fig 2). The controller is a microprocessor based unit that regulates pump speed (rpm), alarm function, the lubrication system, and the occluder. It is compact and lightweight, which facilitates patient transport and physical access for nursing care.
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Patient population
The pump has been used as an LVAD in a total of 17 patients between December 1997 and April 2000. Seven patients at two US centers (Allegheny General Hospital, Pittsburgh, PA and Ohio State University, Columbus, OH) were done with an investigational device exemption from the Food and Drug Administration (FDA) and the approval of the institutional review boards at each hospital. The other 10 patients were done at three institutions outside the US (Johannesburg General Hospital and Milpark Hospital, Johannesburg, South Africa, and John Radcliffe Hospital, Oxford, England).
The indications for pump implantation were postcardiotomy cardiogenic shock (12 of 17, 70%), decompensated cardiomyopathy (2 of 17, 12%), viral myocarditis (2 of 17, 12%), and acute myocardial infarction (1 of 17, 6%). The mean duration of ventricular assist was 8 days (range 1 to 28 days). The mean age was 52 (range 21 to 68 years). The gender distribution was 14 males and 3 females. This information is presented in more detail in Tables 1 and 2.
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The AB-180 ventricular assist device provided satisfactory circulatory support in all patients, as evidenced by increased cardiac index (1.4 ± 0.3 vs 2.3 ± 0.2, p 
0.01) and mean blood pressure (66 ± 8 vs 79 ± 19, p = NS) and decreased mean pulmonary artery pressure (29 ± 5 vs 20 ± 5, p 0.01) (Fig 3). The mean duration of circulatory support was 8.5 days (range 1 to 28 days). In the total group of 17 patients, 8 patients were weaned from the device and 2 patients received a heart transplant. Four weaned patients (4 of 8, 50%) and 1 of the transplant patients (1 of 2, 50%) were subsequently discharged from the hospital. Thus, the overall results showed 58% (10 of 17) were weaned or transplanted and 29% (5 of 17) survived.
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There were no major device-related complications and no documented thromboembolic events. A total of 11 minor device malfunctions occurred, which were caused by alarm and sensing problems. None of these had any clinical impact or significance. One patient required reoperation for bleeding at the aortic anastomosis. Five patients required reoperation for excessive chest tube drainage, which was found to be from serous leakage from the PTFE graft. The graft has subsequently been changed from a thin-walled to a thick-walled PTFE graft. One patient developed a transient neurologic deficit from compression of the superior vena cava by the pump, which resolved after surgical repositioning of the pump. There was one instance of electromechanical failure, due to a faulty electrical extension cable, which was replaced without further problems. The occluder device inflated properly, normal pump operation was restored promptly, and no adverse sequlae developed as a consequence.
Comment
This paper presents the initial clinical experience with an implantable centrifugal assist device, which has been used for treatment of reversible heart failure. The data show that the AB-180 provides reliable circulatory support in a variety of clinical situations, including postcardiotomy shock, viral myocarditis, acute myocardial infarction, and dilated cardiomyopathy with mitral regurgitation. There were no major device-related complications, such as thromboembolism, stroke, or coagulopathic bleeding, and no instance of device failure other than a brief interruption due to a faulty electrical extension cable.
The pump is intended for use in relatively short-term situations (< 10 days), but was successfully used in 1 patient in this study for 28 days until a donor heart for transplant was obtained. The device was weaned in nearly 60% of the patients and 29% of the entire group ultimately survived. These rates are comparable with those achieved with other means of support, such as pulsatile LVADs, centrifugal pumps, and extracorporeal membrane oxygenation (ECMO).
Clinical and experimental data on the AB-180 have been published recently by several centers. Savage and associates summarized the developmental work in experimental animals, which demonstrated the mechanical reliability of the device and confirmed the safety of operating the pump without systemic anticoagulation [1]. Westaby and associates published a case report in which the AB-180 provided complete circulatory support in a young woman with acute, fulminant viral myocarditis complicated by shock [3]. The AB-180 served as a bridge-to-recovery, as the patient recovered within 1 week, allowing device removal. The patient has normal cardiac function at nearly 2 years after this episode. This report contains the data on this patient as well as 16 others in whom the pump was used as an LVAD.
The next question is: Where does the AB-180 fit in the spectrum of circulatory support as we go forward? The intended market for the device was for postcardiotomy cardiogenic shock. Presently, many centers use ECMO or an external centrifugal pump for this group of patients, although this is an off-label use for these technologies [4, 5]. The ABIOMED BVS 5000 and the Thoratec pump are approved by the FDA and available for this indication, but they are not universally used. Presently, the AB-180 is still investigational. The potential advantages it has in comparison with other options are ease of use, the absence of systemic anticoagulation, and lower cost. Nonetheless, postcardiotomy cardiogenic shock comprises a relatively small group of patients, comprising less than 1% of heart operations, and is a particularly difficult group to manage, resulting in a poor outcome in the majority of circumstances.
The largest group of patients with potentially reversible heart failure are those with acute myocardial infarction and unstable hemodynamics. It is estimated that 7% to 10% of all infarctions are complicated by shock, which translates into an annual incidence in the US of 70,000 to 100,000 patients [6]. Current treatment consists of emergency angioplasty, inotropic support, and the intraaortic balloon pump (IABP), but the clinical outcome remains poor, with early and late mortality reported at 60% to 90% in recent studies [7, 8].
Clinical trials are now in progress using the AB-180 in this group of patients. The device is inserted in the catheterization laboratory to stabilize the deteriorating patient with an acute infarction, which facilitates subsequent angioplasty and stenting of the culprit lesion. The technique involves percutaneous transeptal cannulation of the left atrium with a needle, guidewire, and a dilator before placement of a 22F venous cannula from the femoral vein to the left atrium. Pump outflow returns to the femoral artery by means of percutaneous access or with a surgical cut-down on the vessel. Feasibility studies in animals have been completed, and a clinical pilot study is now in progress. This is an exciting new development and results will be available in the coming year. The percutaneous transeptal approach may also become the preferred method for management of surgical patients with postcardiotomy cardiogenic shock, which is a group that continues to have a poor prognosis. This approach would allow sternal closure, reversal of heparin, stabilization of hemodynamics, and removal of the device without the need for reopening the sternum.
References
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