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Ann Thorac Surg 2005;80:309-312
© 2005 The Society of Thoracic Surgeons

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New technology

Initial Experience With the Abiomed AB5000 Ventricular Assist Device System

^a Department of Cardiothoracic Surgery, Lankenau Hospital, Wynnewood, Pennsylvania, USA
^b Perfusion Services, Lankenau Hospital, Wynnewood, Pennsylvania

Accepted for publication July 14, 2004.

^_* Address reprint requests to Dr Samuels, Lankenau Hospital, Medical Science Bldg, Suite 280, 100 Lancaster Ave, Wynnewood, PA19096 (Email: samuelsle{at}aol.com).

	Abstract

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PURPOSE: We describe our initial experience with the Abiomed AB5000 ventricular assist device (VAD).

DESCRIPTION: The Abiomed AB5000 VAD is a system recently approved by the Food and Drug Administration that consists of a fully automatic, vacuum-assisted console and a paracorporeal, pneumatically driven blood pump. The VAD is designed for short or intermediate term use. The console is designed to support the BVS5000 or AB5000 blood pumps. The cannulas and implantation are similar to the BVS5000 system.

EVALUATION: Four cases are described in which two AB5000 systems were placed de novo and two were transitioned from previously placed BVS5000 units. Hemolysis was observed in 2 cases. The AB5000 VAD flows were generally 4.0 to 4.5 L/min, approximately 0.5 L/min less than the BVS5000. Echocardiography demonstrated high-velocity jets from the inflow cannula in the 2 hemolysis cases. One patient died of multiorgan system failure while on support, 2 were successfully weaned from support and transferred to long-term care facilities, and 1 was weaned from support and successfully discharged to home.

CONCLUSIONS: The AB5000 VAD is a versatile paracorporeal pneumatic VAD that can be placed de novo or transitioned from a previously placed BVS5000 unit without the need for additional surgery. Lower outputs, high-velocity jets, and hemolysis were observed in 2 of 4 cases. Modifications in cannulas design and placement as well as console reconfigurations may be necessary to optimize performance.

	Introduction

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Doctor Samuels discloses that he has a financial relationship with Abiomed, Inc.

 

The Abiomed AB5000 (Abiomed Inc, Danvers, MA) is a product recently approved by the Food and Drug Administration that serves as a short- and intermediate-term mechanical support system (Fig 1). It consists of a fully automatic, vacuum-assisted console with a paracorporeal, pneumatically driven pulsatile pump. Like its predecessor, the BVS5000, cannulation is performed with 32F, 36F, or 42F inflow conduits from the atrial or ventricular chambers. Outflow cannulas choices include 10-mm or 12-mm grafts to the aorta or pulmonary artery. Application of the AB5000 can be performed de novo or transitioned from the BVS5000 system by exchanging the blood pumps at the cannulas exit sites without the need for additional surgery. Our initial experience with 4 patients suggests that cannula selection and position are important factors to optimize performance.

View larger version (67K): [in this window] [in a new window]   Fig 1. Abiomed AB5000 System: (A) console, (B) blood pump, and (C) clinical application.

	Clinical Summary

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	Case Reports

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Case 1
A 58-year-old morbidly obese woman presented to an outlying hospital in cardiogenic shock after an acute myocardial infarction with multiple organ system failure. She was transferred to the Lankenau Hospital where an Abiomed AB5000 left VAD (LVAD) and right VAD (RVAD) were placed. The LVAD circuit was established with a 36F inflow cannulas from the LV apex and a 10-mm outflow graft to the ascending aorta. The RVAD circuit consisted of a 32F inflow cannula from the right atrium and a 10-mm outflow graft to the main pulmonary artery. The BIVAD flows were approximately 4 L/min.

Postoperatively, the urine output turned port wine in color. Measurement of plasma free hemoglobin, haptoglobin, lactate dehydrogenase, and bilirubin were consistent with hemolysis. A transesophageal echocardiogram showed a high velocity jet at the tip of the LV apical inflow cannula. The patient went on to die of multiple organ system failure. There were no signs of sepsis.

Case 2
A 74-year-old woman underwent aortic valve replacement, septal myomectomy, and coronary artery bypass grafting at an outlying institution. She had postcardiotomy shock develop that was not reversed with inotropic drug and intraaortic balloon pump therapies. An Abiomed BVS5000 LVAD was placed with a 36F left atrial inflow cannula and a 12-mm outflow graft to the aorta. The patient was transferred to the Lankenau Hospital for further management. The LVAD flows were approximately 5 L/min.

On the fourth postoperative day, significant thrombus developed under the sinuses of the lower BVS blood pump valve. The BVS blood pump was changed to the AB5000 ventricle. This exchange took place at the bedside under sterile conditions with the operating room team and perfusionist. After priming the AB5000 ventricle, the cannulas were clamped and the blood pumps exchanged with no significant hemodynamic deterioration. The AB5000 LVAD flows were approximately 4 L/min. Three days later, native heart recovery was demonstrated on the arterial pressure tracing as well as on transesophageal echocardiogram. The patient was taken to the operating room where the LVAD was successfully explanted. The patient was transferred to a long-term ventilator weaning facility.

Case 3
A 47-year-old man presented to an outlying hospital with cardiogenic shock after a massive posterior wall myocardial infarction. He was taken to the catheterization suite where he underwent complex angioplasty and stenting of the left circumflex coronary artery. During the procedure, the left anterior descending artery became occluded, resulting in hemodynamic compromise requiring cardiopulmonary resuscitation. That artery was reopened, an intraaortic balloon pump was placed, and multiple inotropic drugs, vasoconstrictors, and antiarrhythmic agents were instituted. The patient was transferred to the Lankenau Hospital where an Abiomed AB5000 LVAD was placed. Cannulation was achieved with 36F LA inflow through the right superior pulmonary vein and a 10-mm outflow graft to the ascending aorta. The LVAD flows were approximately 4 L/min. Postoperatively, the urine output was marginal and discolored. Measurements of plasma free hemoglobin, haptoglobin, lactate dehydrogenase, and bilirubin were consistent with hemolysis. Conversion of the AB5000 LVAD to the BVS5000 LVAD was performed at the bedside. Serial measurements of blood chemistries showed resolution of the hemolysis (Table 1). Myocardial recovery improved with successful LVAD removal on the eighth postoperative day. The patient was transferred to a long-term care facility.

Over the course of the next week, the BVS LVAD blood pump showed thrombus formation on multiple separate occasions despite anticoagulation with heparin or argatroban, aspirin, plavix, and dipyridamole. The BVS blood pumps were changed four times. Because of the concern for thromboembolism, the BVS blood pump was changed on the fifth occasion to an AB5000 unit. The AB5000 VAD flows were in the 2.5 L/min range. An echocardiogram was performed showing near collapse of the left atrium. In an effort to resolve this finding, the pneumatic driveline was switched from the higher vacuum (negative 100 mm Hg) port to the lower vacuum (negative 35 mm Hg) port. Continuous echocardiographic monitoring during this maneuver showed resolution of the left atrial collapse. Measurement of the plasma-free hemoglobin during BVS support ranged from 10 to 30 mg/dL. Similar plasma-free hemoglobin levels were observed on the AB5000 VAD with the lower vacuum setting. The LVAD was successfully explanted and the patient discharged.

	Comment

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The AB5000 VAD was designed to serve as an improvement over the BVS5000 system. Limitations in patient mobility, frequency of thrombotic complications, and the suboptimal role as a bridge to transplant device are among the disadvantages of the BVS5000. Yet, the BVS5000 is the most frequently used VAD in the world for acute cardiogenic shock because of its simplicity and relatively low cost. The AB5000, which shares some features of the BVS5000 and the AbioCor, is engineered to meet the needs of recovery or bridging. The features of the AB5000 include its compatibility with the BVS5000 cannulas, a fully automatic console, and a paracorporeal blood pump. As such, it resembles the Thoratec pVAD (Thoratec Laboratories, Pleasonton, CA). Among the differences are that the Abiomed cannulas are smaller than their Thoratec counterparts and there is no adjustable vacuum or adjustable drive-pressure. Instead, the AB5000 console was designed with two ports of fixed vacuum—a low vacuum port for use with the BVS5000 and a high vacuum port for use with the AB5000—and fixed drive-pressures of 420 mmHg (LVAD) and 300 mmHg (RVAD). Although laboratory animal studies have shown that the configuration of the AB5000 to the high vacuum port was satisfactory with respect to hemodynamic support and hemolysis, the combination of high vacuum and small cannula size may be problematic in the clinical setting.

Although hemolysis is a known phenomenon with VADs, the extent of hemolysis, the clinical manifestations, and the management of it varies. Several bioengineering studies have examined the extent of hemolysis in rotary pumps [2], centrifugal pumps [3], axial flow pumps [4], and total artificial hearts [5]. In addition to the mechanics of the flow by the VAD, reports by Billy and colleagues [6] and Luckraz and colleagues [7] showed that hemolysis may be related to the type of artificial valve within the VAD or the addition of hemofiltration to VAD support. The rate of hemolysis of commercially available VADs vary and depend upon the definition of hemolysis. In the Thoratec instructions-for-use manual, the definition is plasma-free hemoglobin that is greater than 3 times the high normal value—after 2 weeks of pumping, the average plasma-free hemoglobin was 18 ± 9 mg/dL. However, a more commonly used definition is a plasma-free hemoglobin of greater than 40 mg/dL. As such, Farrar and colleagues [8] reported a hemolysis rate of 19%. In an 11-year experience with the Pierce-Donarchy VAD, Pennington and associates [9] reported hemolysis in 20% of the patients, but only clinically significant in 1 patient—this patient’s hemolysis was observed on a Sarns pneumatic LVAD and resolved when switched to the Thoratec LVAD. In comparison, Abiomed’s BVS5000 hemolysis rate was reported at 17% during their clinical trial [10]. Although an exact incidence of hemolysis for the AB5000 system is not reported, personal communication with the company suggests a rate of 17%—10 of 60 patients with plasma-free hemoglobin greater than 40 mg/dL (personal communication, Robert Kung, Abiomed).

The issue at hand is the nature of the hemolysis observed and the slightly lower VAD flows with the new system. Although a limited number of AB5000 devices have been implanted to date, we have observed two findings at our center: (1) the VAD output appears to be approximately 0.5 L less than with the BVS5000, and (2) hemolysis has been observed in 2 of the 4 patients. In our cases, and in another elsewhere [11], a high-velocity jet was observed at the level of the inflow cannula resulting in high sheer rates. In these instances, the tip of the cannula appeared to be partially and intermittently obstructed by surrounding tissue. It is our opinion that the high velocity jets, the inflow chamber collapse, the reduction in VAD flow, and the appearance of hemolysis are interconnected. Although it may be unfair to assign the mechanics of the VAD as the sole cause for the hemolysis, these associations seem compelling. Furthermore, we immediately observed relief of inflow chamber collapse, improvement in VAD flow, and improvement in the laboratory chemistries once the level of the vacuum drainage was reduced or the AB 5000 system switched to a gravity drainage unit such as the BVS5000.

As a result of these findings, we recommend the following studies and procedures after placement of the AB5000 system: (1) mandatory echocardiographic confirmation of inflow cannula tip position with absence of high velocity jet and absence of inflow chamber collapse; (2) serial monitoring of laboratory chemistries, including plasma-free hemoglobin, haptoglobin, lactate dehydrogenase, and bilirubin; (3) use of larger inflow (eg, 42F) cannulas; and (4) conversion to the low vacuum port or gravity drainage system if inflow chamber collapse, high velocity jets, or hemolysis is observed. It is necessary, however, to bear in mind that conversion to the low vacuum setting while on the AB5000 ventricle results in falsely elevated flows owing to the console’s flow calculation algorithms.

In conclusion, the Abiomed AB5000 was designed to be an upgrade to the BVS5000 in terms of patient mobility, blood pump durability, and overall versatility. Further experience with the AB5000 is necessary to address the issues observed in the early stages of its experience. Console and cannula modifications may be necessary to optimize the AB5000 performance.

	Disclosures and Freedom of Investigation

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The authors had full control of the design of the study, methods used, outcome parameters, analysis of data, and production of the written report. The tested technology was purchased, and the evaluation was not funded.

	Disclaimer

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The Society of Thoracic Surgeons, the Southern Thoracic Surgical Association, and The Annals of Thoracic Surgery neither endorse nor discourage use of the new technology described in this article.

	References

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1. Samuels LE, Thomas MP, Morris RJ, Wechsler AS. Surgical options for placement of the Abiomed BVS 5000 left ventricular assist device J Congest Heart Fail Circ Support 1999;1:85-89.
2. Mitamura Y, Nakamura H, Sekine K, et al. Prediction of hemolysis in rotary blood pumps with computational fluid dynamics analysis J Congest Heart Fail Circ Support 2001;4:331-336.
3. Song X, Throckmorton AL, Wood HF, et al. Computational fluid dynamics prediction of blood damage in a centrifugal pump Artif Organs 2003;27:938-941.[Medline]
4. Yano T, Sekine K, Mitoh A, et al. An estimation method of hemolysis within an axial flow blood pump by computational fluid dynamics analysis Artif Organs 2003;27:920-925.[Medline]
5. Ohashi Y, de Andrade A, Nose Y. Hemolysis in an electromechanical driven pulsatile total artificial heart Artif Organs 2003;27:1089-1093.[Medline]
6. Billy GG, Miller CA, Pallone MN, Donarchy JH, Pierce WS. Hemolytic differences among artificial cardiac valves used in a ventricular assist pump Artif Organs 1995;19:339-343.[Medline]
7. Luckraz H, Woods M, Large SR, Papworth VAD Group And hemolysis goes onventricular assist device in combination with veno-venous hemofiltration. Ann Thorac Surg 2002;73:546-548.[Abstract/Free Full Text]
8. Farrar DJ, Hill JD. Univentricular and biventricular Thoratec VAD support as a bridge to transplantation Ann Thorac Surg 1993;55:276-282.[Abstract]
9. Pennington DG, McBride LR, Miller LW, et al. Eleven years’ experience with the Pierce-Donarchy ventricular assist device J Heart Lung Transplant 1994;13:803-810.[Medline]
10. Guyton RA, Schonberger JP, Everts PA, et al. Postcardiotomy shockclinical evaluation of the BVS 5000 biventricular support system. Ann Thorac Surg 1993;56:346-356.[Abstract]
11. Bogaev RC, Schnitzler RN, O’Tero C. Hemolysis due to high sheer rate at the inflow cannula site of the AB5000 ventricle device[Abstract] ASAIO J 2004;50:134.

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This Article Abstract Full Text (PDF) Alert me when this article is cited Alert me if a correction is posted Citation Map Services Email this article to a friend Similar articles in this journal Similar articles in PubMed Alert me to new issues of the journal Add to Personal Folders Download to citation manager Author home page(s): Louis E. Samuels Francis Ferdinand Permission Requests Citing Articles Citing Articles via HighWire Citing Articles via Google Scholar Google Scholar Articles by Samuels, L. E. Articles by Ferdinand, F. Search for Related Content PubMed PubMed Citation Articles by Samuels, L. E. Articles by Ferdinand, F. Related Collections Mechanical Circulatory Assistance