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Ann Thorac Surg 1999;68:646-649
© 1999 The Society of Thoracic Surgeons
a Division of Cardiac Surgery, Brigham and Women’s Hospital, Harvard Medical School, Boston, Massachusetts, USA
Address reprint requests to Dr. Couper, Division of Cardiac Surgery, Brigham and Women’s Hospital, 75 Francis St, Boston, MA 02115
Presented at the Fourth International Conference on Circulatory Support Devices for Severe Cardiac Failure, Houston, TX, Oct 3–5, 1997.
Abstract
Background. In 1994, the ABIOMED BVS 5000 was incorporated into our acute cardiac assist armamentarium. This report is a general overview of our experience. A hypothetical cost analysis focusing on specific devices and device-related personnel contrasted the BVS 5000 with our prior model of centrifugal pump use.
Methods. In 3 years, 22 patients were supported with the BVS 5000, as a biventricular assist device in 40%, right ventricular assist device in 27%, and left ventricular assist device in 32%. Indications were postcardiotomy support in 12, acute myocarditis in 2, bridge to transplant in 4, and failed heart transplant in 4. The cost analysis was performed retrospectively. The actual cost of disposable blood pumps, including replacement pumps, and cannulae constituted the BVS cost. The hypothetical centrifugal costs included the disposables, replacement cones, as well as the labor costs of the continuous perfusionist coverage.
Results. Of the 22 patients, 10 (45%) were weaned and 13 (59%) were successfully discharged. Five patients were transplanted while on BVS 5000 support, accounting for a higher rate of discharge. Comparison of "actual" BVS costs with "projected" centrifugal costs revealed differences based upon the intended application of the BVS. In bridge-to-transplant patients with long duration of support, the daily cost of support was dramatically lower with the BVS 5000. For short-term postcardiotomy support, acute myocarditis, or failed transplant, the differences were small.
Conclusions. Because the BVS 5000 was readily managed by the intensive care unit nursing staff, this system displaced centrifugal systems in our program. Outcome measures of weaning and successful discharge were improved relative to our prior experience with centrifugal pumps. Even without taking indirect costs into account, the hypothetical cost analysis supported continued use of the BVS system for acute cardiac assistance.
Despite substantial improvements in myocardial protection and other technical advances, postoperative ventricular dysfunction persists as a complication in 2%–6% of all patients undergoing cardiac or thoracic aortic surgery [1, 2]. Despite maximal inotropic therapy, in conjunction with intraaortic balloon pump (IABP) support, 0.5% to 1.0% cannot be weaned readily from cardiopulmonary bypass and would require some form of mechanical cardiac assistance to achieve adequate systemic pressure and perfusion [3, 4]. Over the years, mechanical cardiac assistance has become a more successful and acceptable approach for this difficult problem. Over the last several years, a number of cardiac assist devices have been approved for indications beyond postcardiotomy failure, including applications in acutely failed heart transplant, acute myocarditis causing shock, and bridging to transplantation. The ABIOMED BVS 5000 (ABIOMED Inc, Danvers, MA) has achieved FDA approval as a temporary circulatory support device for: (1) postcardiotomy shock; (2) right ventricular (RV) failure after an implantable left ventricular assist device (LVAD); (3) failed heart transplant; and (4) any cause of reversible ventricular failure. This report describes our experience with the ABIOMED BVS 5000 with particular emphasis on the logistics and cost-effectiveness of a circulatory support program in a busy academic cardiac surgery service.
Material and methods
The ABIOMED BVS 5000 is a pneumatically driven extracorporeal pulsatile ventricular assist device, capable of providing univentricular or biventricular support (Fig 1). The configuration and function of the blood pump have been described in detail previously [4–7].
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L/min/m2) were typical in those patients actually weaned from cardiopulmonary bypass (CPB). Some patients could not be weaned long enough to satisfy the above criteria, either due to intractable arrhythmia or profound heart failure. Whenever feasible and appropriate, all patients had a trial of maximal pharmacologic support and IABP support. The indications for support were widely accepted classifications as follows: (1) postcardiotomy, including immediate failure to wean CPB or delayed postoperative heart failure due to arrhythmias, infarction, or ischemia; (2) acute fulminant myocarditis; (3) failed heart transplant; and (4) bridging to heart transplant.
Clinical experience
From the inception of our ABIOMED BVS 5000 program in September 1994 through the end of September 1997, we have supported 22 cardiac surgical patients with this device. Over this time, 4,360 cardiac surgical procedures were carried out at the Brigham and Women’s Hospital. The utilization rate of ventricular assist device (VAD) in 0.5% of the caseload is relatively low and is reflective of philosophic differences between surgeons and a conservative age policy with exclusion of patients with a "physiologic age profile" over 70 years.
All but one of our patients were supported with the standard flow console, achieving maximal flows around 5.5 L/min. This provided sufficient hemodynamic support to stabilize patients throughout most of their course. Clinical limitations occurred in two settings: (1) high-output septic states, and (2) arterial vasoplegia due to neurologic injury or an ill-defined cause such as systemic inflammatory response. In these settings, the need for intensive vasopressor support frequently resulted in worse tissue malperfusion and concomitant multiple organ failure.
All VAD insertions were performed via sternotomy with right or left atrial cannulation, although seven left ventricular (LV) apex cannulations were carried out in the latter half of the series. Patient mobility was limited; only 1 patient became well enough to ambulate within his intensive care unit (ICU) room.
The mode of circulatory support, univentricular or biventricular, was largely a function of the specific indication for support or the presence of intractable ventricular tachyarrhythmias (Table 1). Overall, the ABIOMED BVS was implanted as an LVAD in 32%, right ventricular assist device (RVAD) in 27%, and biventricular assist device (BIVAD) in 41%. The bridge-to-transplant group consisted of hybrid VAD implantations. The ABIOMED RVADs were placed in conjunction with TCI HeartMate LVADs (Thermo Cardiosystems Inc, Woburn, MA). The two ABIOMED BIVADs were inserted in patients suffering from ongoing cardiac arrest ventricular fibrillation (VF) in the setting of preexisting chronic heart failure and intractable ventricular arrhythmia. In 1 of these patients, the ABIOMED LVAD was replaced 5 days later by a TCI HeartMate LVAD. Unfortunately, uncontrollable polymorphic ventricular tachycardia and ventricular fibrillation precluded subsequent ABIOMED RVAD explantation. Transplantation was successfully carried out at 50 days of BIVAD support.
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In the patients undergoing support with primary intention to bridge to transplant, a patient with post-TCI LVAD placement of a BVS RVAD was able to undergo RVAD explantation after 38 days. The patient remains a long-term survivor after transplantation after 7 months of TCI LVAD support. The 3 remaining patients underwent successful transplantation; however, 1 died of sepsis unrelated to the VAD 6 weeks after the transplant.
Logistics of a support program
Previously, our service utilized centrifugal pumps either as VADs or extracorporeal membrane oxygenation (ECMO) for temporary cardiac support. Given the complexity of these systems and the lack of familiarity on the part of the ICU nurses, we staffed all supports with the full-time presence of a perfusionist. Because of the fully automatic operation of the ABIOMED BVS 5000, we converted to comprehensive management of the patient and the pump by our ICU nurses, as it has typically been done at most centers. During full support in the automatic mode, ICU nurses may modulate VAD flow by changing pump height relative to the patient. They ensure adequate filling of the VAD and maintain effective decompression of the native heart. They carry out changes in VAD flows during weaning trials.
Routine anticoagulation protocols are administered by the ICU nursing staff. To ensure timely and accurate activated clotting time (ACT) results while monitoring heparin therapy, the ICU nurses assumed the task of performing ACT testing at the bedside. Federal regulations (Clinical Lab Information Act [CLIA]) have added some onerous but necessary documentation and quality control measures to the otherwise simple ACT test.
As a consequence of shifting management to the ICU nursing staff, the need for support from the perfusion service has been confined to the replacement of blood pumps when thrombus has been detected. These pump change outs have been performed at the bedside in the ICU by the surgeons with ICU nurse and perfusionist assistance.
Cost analysis
Increasing concerns over the rising costs of medical care, especially advanced medical technology, are forcing clinicians and manufacturers to closely examine mechanical assist devices. In 1995, Mehta and colleagues [8] stated, "currently there is considerable need to define clearly the costs associated with mechanical assistance to allow more accurate assessment of the clinical and financial implications of implanting these devices." To address these concerns in our program, we carried out a retrospective analysis of all 22 patients supported with the ABIOMED BVS 5000 and compared these "actual" costs to a hypothetical cost of a perfusionist-managed centrifugal VAD (Biomedicus; Medtronic, Eden Prarie, MN) support in these same patients.
Methods
Several assumptions were made to compare costs between the two groups. First, we assumed the duration of support in days to be equal. Second, we equalized the actual number of BVS blood pump changes with Biopump cone changes, a reasonable assumption given that we had previously abandoned prophylactic cone changes as unnecessary. Lastly, the capital investment in drive consoles for the BVS and for the Biopump were depreciated over many years and felt to be comparable in the short term. Thus, only the cost of disposables and labor were taken into account.
For the actual ABIOMED BVS costs, we totaled the cost of the original blood pump(s), with cannulae, and added in the cost of the subsequent replacement blood pumps. For the hypothetical centrifugal pump (Biomedicus) costs, we added the cost of blood pumps, cannulae, and an equal incidence of replacement pumps, and the labor charges for the perfusionist. Our perfusionists operate on a 12-h/day shift, with double time mandated for overtime stays beyond 12 hours. An average wage would be $34/h for the first 12 hours and $68/h for the second 12 hours of a day. Given the limited number of and lack of superfluous perfusionists, along with the desire to run the usual OR schedule, the centrifugal VAD/ECMO support had historically generated large amounts of overtime for the perfusionists. Also included in the centrifugal costs is a charge of $620 for an intraaortic balloon for LVAD or BIVAD patients, as this was routinely done to maintain pulsatility. For RVAD patients (n = 6), an IABP cost was not included, as it was not an integral part of the VAD support. In reality, virtually all patients had an IABP in place at some point in time during their entire hospital course.
The amalgamated cost data are shown in Table 3 and are expressed as an average daily cost. The patients were grouped by the primary indications for device implantation. The longer-duration patients in each of the first three groups were those who had failed to recover and wean. Some of these had crossed over into the realm of bridge to transplant. The groups associated with the higher costs for the BVS were acute myocarditis and failed transplant groups, in which the majority required BIVADs, and because of more prolonged support required more frequent pump replacements. In the bridge-to-transplant group, the costs of the BVS were spread out over a greatly increased duration of support. For the postcardiotomy patients, which would constitute the majority of patients supported in most centers, the ABIOMED BVS demonstrated a small cost advantage.
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Comment
Profound cardiac failure continues to occur in a small number of cardiac surgical patients. A variety of VADs have been successfully used to stabilize the circulation to allow for recovery or transplantation [3, 9–13]. Through lessons learned from clinical experience, the importance of appropriate patient selection and timely implantation have been recognized. At the Brigham and Women’s Hospital, our initial experience in circulatory support began with a perfusionist-based centrifugal VAD and ECMO program. The implantable TCI HeartMate Implantable Pneumatic (IP) LVAS was available to us as an investigational device in 1991. Our temporary device program evolved primarily to the ABIOMED BVS in late 1994, after FDA approval. Our outcomes for cardiac assist devices substantially improved with conversion. The discharge rate of 50% for postcardiotomy patients was twice that of our previous patients. Historically, there have been reports of discharge rate of 18%–42% with centrifugal devices [14, 15]. The US VAD Registry had typically reported a 50% wean rate and 25% discharge rate in postcardiotomy applications [14]. Very few series have directly compared centrifugal versus pulsatile pumps in a single institution or group, however, the outcomes have been somewhat better with the pulsatile pumps in these series [4, 15, 16].
With the advent of the ABIOMED BVS in our hospital, we have seen a shift in our costs from personnel to disposable blood pumps. Our analysis has shown this to be a cost-effective means of providing temporary mechanical cardiac support. Beyond the direct costs of circulatory support are sometimes hidden costs. In a busy program such as ours, the operating schedule was usually full during the week, and 2 or 3 urgent cases were done most weekends. The load on the perfusion service was substantial, especially when VAD supports with centrifugal devices continued into the weekend or holidays. Only emergent heart cases could then be done, introducing the additional cost of delaying surgery for other patients confined to the hospital. There were times when the lack of sufficient perfusion staff resulted in limitation of the routine operating room schedule, creating a hidden cost by idling other specialized personnel.
Since 1989, our methods of temporary circulatory support have evolved from centrifugal VAD to centrifugal extra corporeal life support [ECLS] (ECMO) to the ABIOMED BVS 5000. Outcomes have steadily improved. Success is dependent upon many factors, including team experience, appropriate patient selection, and appropriate technology. The ABIOMED BVS 5000 has enabled greater success while proving to be a cost-effective method of temporary circulatory support. We believe this technology to be a valuable addition to our program without any compromise in the overall practice of the cardiac surgery program.
References
This article has been cited by other articles:
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  S. Aggarwal, F. Cheema, M. C. Oz, and Y. Naka Long-Term Mechanical Circulatory Support Card. Surg. Adult, January 1, 2008; 3(2008): 1609 - 1628. [Full Text]
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 A. F. Hernandez, J. D. Grab, J. S. Gammie, S. M. O'Brien, B. G. Hammill, J. G. Rogers, M. T. Camacho, M. K. Dullum, T. B. Ferguson, and E. D. Peterson A Decade of Short-Term Outcomes in Post Cardiac Surgery Ventricular Assist Device Implantation: Data From the Society of Thoracic Surgeons' National Cardiac Database Circulation, August 7, 2007; 116(6): 606 - 612. [Abstract] [Full Text] [PDF]
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 R. John, K. Liao, K. Lietz, F. Kamdar, M. Colvin-Adams, A. Boyle, L. Miller, and L. Joyce Experience with the Levitronix CentriMag circulatory support system as a bridge to decision in patients with refractory acute cardiogenic shock and multisystem organ failure J. Thorac. Cardiovasc. Surg., August 1, 2007; 134(2): 351 - 358. [Abstract] [Full Text] [PDF]
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 H. Tatewaki, M. Masuda, T. Nishida, Y. Kaji, H. Ushinohama, S. Morita, and H. Yasui Successful Treatment of Tachycardia-Induced Cardiomyopathy With LVAD in a 12-Year-Old Boy Ann. Thorac. Surg., August 1, 2005; 80(2): e5 - e7. [Abstract] [Full Text] [PDF]
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