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Ann Thorac Surg 2005;80:548-552
© 2005 The Society of Thoracic Surgeons

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Original article: Cardiovascular

CardioWest Total Artificial Heart: Bad Oeynhausen Experience

Department of Thoracic and Cardiovasular Surgery, Heart Center North Rhine-Westphalia, Ruhr University Bochum, Bad Oeynhausen, Germany

Accepted for publication February 28, 2005.

^_* Address reprint requests to Dr El-Banayosy, Klinik für Thorax und Kardiovaskularchirurgie, Herzzentrum NRW, Georgstr. 11, 32545 Bad Oeynhausen, Germany (Email: abanayosy{at}hdz-nrw.de).

	Abstract

Top Abstract Introduction Patients and Methods Results Comment Acknowledgments References

 
BACKGROUND: The use of ventricular assist devices (VAD) has become a widely accepted therapeutic option. However, there are still limitations to the patient collective eligible for VAD placement, who might therefore benefit from the implantation of a total artificial heart. We present the first German single-center experience with the CardioWest total artificial heart (TAH) (SynCardia Systems, Tucson, AZ) in 42 patients.

METHODS: Between February 2001 and December 2003, 42 patients (37 men, 5 women, mean age 51 ± 13 years) received a TAH at our Center. Their body surface area ranged between 1.5 and 2.4 (mean, 1.9 ± 0.19) m². All patients were in persistent cardiogenic shock in spite of maximum inotropic support and had numerous preoperative risk factors (intraaortic balloon pumping, mechanical ventilation, acute renal failure, previous cardiac surgery, recent cardiopulmonary resuscitation).

RESULTS: Duration of support was 1 to 291 days. Eleven patients (26%) underwent successful transplantation; 9 of them could be discharged home. Twenty-two patients died under support, 21 of them from multiple organ failure and 1 patient from a technical problem. Nine patients are still on the device, 4 of them at home after the original CardioWest console was replaced by the Berlin Heart EXCOR driver (Berlin Heart, Berlin, Germany). Exceptional results were achieved in patients with cardiogenic shock after cardiac surgery or after acute myocardial infarction.

CONCLUSIONS: Against the background of the extremely poor preoperative situation of our patients, the overall survival rate of 48% can be considered as favorable. A prospective, randomized study is planned to find out whether patients with idiopathic dilated or ischemic cardiomyopathy are more likely to benefit from a biventricular assist device or a total artificial heart.

	Introduction

Top Abstract Introduction Patients and Methods Results Comment Acknowledgments References

 
The problems resulting from an increasing number of people suffering from congestive heart failure are well known. Although a variety of therapeutic options are available, end-stage heart failure in a significant number of these patients still requires heart transplantation, a procedure widely accepted but facing an enormous shortage in donor organs. In the last two decades, numerous ventricular assist devices (VAD) have been developed and in the meantime are in routine clinical use in many centers worldwide as a bridge to, and even an alternative to, transplantation. However, there are still some limitations to the patient collective eligible for VAD placement. These patients might benefit from the implantation of a total artificial heart (TAH).

In the past decades, several attempts were made to manufacture a TAH, the use of which in its early days, however, was associated with high rates of infection and thromboembolism. A modified version of the Jarvik-7 total artificial heart (CardioWest Total Artificial Heart [SynCardia Systems, Tucson, AZ]) [1] has, meanwhile, been implanted in about 300 patients worldwide. In the following we present the first German experience with the CardioWest TAH implanted in 42 patients in our Center.

The CardioWest TAH is a biventricular orthotopic pneumatic pulsatile pump with two separate artificial ventricles that take the place of the native ventricles. Wire-reinforced air conduits covered with Dacron in the transabdominal wall pathway connect to longer drivelines and to an external console. This console is mobile by virtue of batteries and compressed air tanks, allowing the patient freedom to move about the hospital or other care facilities.

The two artificial ventricles, although differing in the spacing and angulations of the inflow and outflow valves and the entry sites for the conduits for the left and right sides, are basically the same in construction. Each has a rigid spherical outer "housing" that supports a seamless blood-contacting diaphragm, two intermediate diaphragms, and an air diaphragm, all made of segmented polyurethane, and separated by thin coatings of graphite. The inflow (27 mm) and outflow (25 mm) Medtronic-Hall valves (Medtronic Inc, Minneapolis, MN) are mounted on the housing. The diaphragm excursion is essentially from one wall of the housing to the other, allowing the ventricle to fully fill and fully eject nearly 70 mL per beat.

A flexible polyurethane-lined inflow connector is sewn to the atrial cuff of the recipient heart, and then snapped on to the inflow valve mount of the artificial ventricle. On the outflow side, the Dacron outflow connectors are snapped on to the outflow valve mounts of the artificial ventricle after the distal connector anastomoses have been completed.

The external console consists of two pneumatic drivers, one primary and one back-up, transport batteries, air tanks, and an alarm and computer monitoring system. The CardioWest TAH was granted CE approval in Germany in 2000.

	Patients and Methods

Top Abstract Introduction Patients and Methods Results Comment Acknowledgments References

 
Selection Criteria
Since the CardioWest TAH became available at our Center in February 2001, our previously published [2] selection criteria for patients scheduled for biventricular support have been modified. Patients with severe cardiogenic shock resulting in extensive multiple organ failure and a body surface area of more than 1.5 m² are now more likely to receive the CardioWest TAH. This also applies to patients after massive myocardial infarction in whom a left ventricular or biventricular device cannot be implanted for technical or surgical reasons. Furthermore, patients with postcardiotomy heart failure, who have been supported with other ventricular assist devices for a reasonable period of time and do not show any signs of myocardial recovery, receive the CardioWest after having been evaluated and approved for heart transplantation. In addition, implantation of the CardioWest is indicated in patients with intracardiac shunts or left ventricular thrombi, which make them ineligible for VAD implantation, and in selected cases with primary graft failure or rejection.

Patients
Between February 2001 and December 2003, 42 patients (37 men, 5 women, aged 15 ± 74 years; mean age, 51 ± 13 years) out of a total of 118 patients undergoing mechanical circulatory support (18 of them with Thoratec [Thoratec Laboratories Corp, Pleasanton, CA] biventricular support) received a CardioWest TAH at our Center. Their height ranged from 151 to 192 (mean, 176 ± 11) cm, their weight from 46 to 113 (mean, 79 ± 13) kg. Body surface area was 1.5 to 2.4 (mean, 1.9 ± 0.19) m². Left ventricular enddiastolic diameters ranged from 38 to 90 (mean, 67 ± 14) mm, left ventricular endsystolic diameters from 31 to 82 (mean, 60 ± 14) mm. The patient cohort, with regard to etiology of heart failure, is described in Table 1. All patients were in persistent cardiogenic shock in spite of maximum inotropic support. Twenty-eight patients (67%) had been under intraaortic balloon pumping, 31 patients (74%) were under mechanical ventilation, 22 patients (52%) had undergone continuous venovenous hemofiltration because of acute renal failure, 21 patients (50%) had previous cardiac surgery, and 19 patients (45%) had undergone cardiopulmonary resuscitation within the 24 hours prior to CardioWest implantation. Fifteen patients (35%) had been on mechanical circulatory support before for a mean duration of 48 hours (femorofemoral cardiopulmonary bypass, n=11; Thoratec, n=2; Abiomed (ABIOMED, Inc, Danvers, MA), n=1; centrifugal pump, n=1). Thirteen of these patients had received a device for short-term support under resuscitation conditions, but required long-term assistance later. One patient with giant cell myocarditis had initially been on femorofemoral cardiopulmonary bypass for 5 days. Since he showed no recovery, he was switched to Thoratec biventricular support with biatrial cannulation because of the short history of heart disease and the young age of the patient. Unfortunately, after another 7 days of support, a thrombus was detected in the left ventricle leading to CardioWest implantation. In the other patient supported with the Thoratec system after acute myocardial infarction, thrombus formation in the left ventricle was also observed after 7 days of support, which made a system change necessary. Preoperative hemodynamic and laboratory data are summarized in Table 2.

Anticoagulation Protocol
During the first 24 hours postoperatively, the patients receive no anticoagulation. On postoperative day (POD) 1, heparin administration is started if blood loss is less than 50 mL/h over 3 consecutive hours (partial thromboplastin time [PTT] target: 50 seconds). A thromboelastographic (TEG) analysis is performed to identify patients with hypercoagulability (maximal amplitude > 68 mm), who additionally receive 1 mg/kg acetylsalicylic acid (ASA). On POD 2, heparin dosage is increased to adjust PTT to 60–70 seconds. Repeat TEG is performed to evaluate the effect of ASA administration, which might be adjusted to achieve the recommended platelet inhibition level of 70%. This medication is continued until two weeks postoperatively. If ASA turns out to be ineffective, it is replaced by clopidogrel, the effect of which is also verified by TEG to achieve a degree of inhibition of greater than 40%. Two weeks after surgery, heparin is replaced by warfarin (Coumadin), and ASA, or clopidogrel medication is continued.

Antibiotic Protocol
Our antibiotic prophylaxis is the same as with other assist devices and consists of a short-term prophylactic administration of cephalosporin (Cefazolin) (3 x 2 g daily) in all patients until all drains are removed. Further infections are treated according to the antimicrobial sensitivity test. In patients who had been on antibiotic treatment prior to implantation, their regime is replaced by vancomycin, and tazobactam plus piperacillin for at least 4 weeks. Antimycotic prophylaxis was not performed routinely.

	Results

Top Abstract Introduction Patients and Methods Results Comment Acknowledgments References

 
The implantation procedure was uneventful in all patients without any intraoperative fatality. Eight patients (most of them after acute myocardial infarction) had fit problems and chest closure was only possible on PODs 2–5. Three of these patients had a body surface area less than 1.7 m². However, fit problems were not observed in three other patients with a body surface area less than 1.7 m². A bleeding complication defined as blood loss greater than 1,500 cc·m² ·24 hours occurred in 9 patients (21%) with 8 of them needing reexploration. This bleeding complication was not surgery-related but was due to the fact that 35% of our patients had been on mechanical circulatory support before with subsequent coagulation disorders. Liver failure as defined by bilirubin greater than 10 mg/dL and transaminase three times as high as the normal value was found in 11 patients (26%) needing molecular adsorbent recirculating system therapy. Renal failure requiring renal replacement therapy occurred in 3 of 20 patients, who had no renal failure preoperatively. Four patients underwent abdominal surgery on the device for mesenteric ischemia. Hemolysis as defined by plasma-free hemoglobin of greater than 50 mg for more than 12 hours was found in 3 patients (Table 3). These patients usually had systemic hypertension thus needing higher driving pressures. Hemolysis could be resolved by reducing the driving pressure in combination with antihypertensive agents.

Duration of support was 1 to 291 (mean, 86 ± 89; median, 51) days. Altogether, 11 of 42 patients (26%) underwent successful cardiac transplantation with 10 being discharged home. One patient died from an infection one week post heart transplantation (HTx). Another patient, who had been discharged from hospital, died 6 months after the procedure from acute rejection. Survival in those 9 patients being discharged is 2 to 25 months. Twenty-two patients (52%) died under support, 13 of them from multiple organ failure after 1 to 68 days of support, ie, the preexisting organ dysfunction could not be resolved, 3 patients from mesenteric ischemia (72 to 167 days), 2 patients each from sepsis and multiple organ failure (26 and 87 days), and from cerebral bleeding (52 and 56 days), and one patient each from multiple organ and respiratory failure (37 days) and from a technical problem after 5 days. Mean duration of support among survivors to cardiac transplantation was significantly lower (174 ± 87 days) than in nonsurvivors (43 ± 52 days). Nine patients are still on the device, 5 of them within the hospital, whereas 4 patients could be discharged home for a mean duration of 42 days while on the device after the original CardioWest console was replaced by the EXCOR Berlin Heart driver. Of those 15 patients who previously had been supported by a different assist device, 6 patients underwent cardiac transplantation, 5 of them were discharged from hospital. The patient with giant cell myocarditis supported with three different devices is doing well at home. Table 1 details the results with regard to etiology of heart failure.

	Comment

Top Abstract Introduction Patients and Methods Results Comment Acknowledgments References

 
Although a variety of devices for mechanical circulatory support have become available, patients with intracardiac thrombi or shunts, structural damage to the heart, or congenital heart defects are not eligible for the implantation of these assist devices but need a total artificial heart in case of endstage heart failure. This paper describes the application of the CardioWest TAH in one of the sickest patient cohort receiving mechanical circulatory support ever reported as shown by their preimplant hemodynamic and laboratory data. In our recent report on patients bridged to cardiac transplantation with the Thoratec VAD system, preoperative ventilation was shown to be an independent risk factor of death [4]. In the present CardioWest collective, 74% of patients had been on mechanical ventilation preoperatively.

In his recently published paper on 81 patients receiving the CardioWest TAH, Copeland and colleagues [5] reported on a survival to transplantation of 79%, which is markedly higher than that of our collective. However, neither collective is comparable in terms of preoperative risk factors. The Copeland group excluded patients from TAH implantation with a previous vascular assist device or dialysis 7 days before. In contrast, 35% of our patients had been on mechanical circulatory support before and 52% had undergone dialysis for renal failure. Furthermore, the incidence of intraaortic balloon pumping (36% in the Copeland collective vs 67% in our collective), mechanical ventilation (42% vs 74%), previous cardiac surgery (38% vs 50%), and previous cardiopulmonary resuscitation (37% vs 45%) was significantly higher in our group.

In view of the extremely poor preoperative status of the patients presented, the overall survival rate of 48% among these patients can be considered as a favorable result. The main cause of death in our experience was a preimplant multiple organ failure, which turned out to be irreversible after CardioWest implantation. However, an exceptional outcome was found in patients with acute myocardial infarction (AMI) and with postcardiotomy heart failure. Duration of support among survivors with AMI etiology was 185 ± 60 days compared to 39 ± 54 days among nonsurvivors, which is comparable to the support times in the total collective. Patients with these etiologies became acutely sick and their organs did not suffer from long standing low output syndrome compared to patients with a chronic disease like idiopathic dilated or ischemic cardiomyopathy (79% fatalities). Furthermore, severe cardiogenic shock after AMI is usually associated with a high release of cytokines [6]. We assume that the removal of the heart might limit the production of cytokines, which are made responsible for end-organ failure. This hypothesis is the subject of further investigation at our Center.

The body surface area (BSA) always is a main issue when implanting a total artificial heart. In our cohort, 6 patients had a BSA of less than 1.7 m², which resulted in a fit problem in 3 patients only with two survivors (one with a fit problem). However, the fit problems were more likely to be associated with the etiology of the disease (AMI, postcardiotomy cardiogenic shock) than with BSA. Nevertheless, the number of this subgroup is too small to make any meaningful conclusions.

Regarding the clinical status at the time of HTx, TAH patients are accepted for HTx as soon as they have no organ dysfunction. In general, they do not have a higher priority in organ allocation than other patients, except for technical problems, uncontrolled infection, or repeated transient ischemic attacks.

Despite a less sophisticated anticoagulation protocol as described by LePrince and colleagues [7] and Copeland and colleagues [8], and considering the more activated platelet function in TAH patients compared to those supported with other ventricular assist devices, the incidence of thromboembolic complications in our very sick cohort was only 0.04 thromboembolic events per patient month, which proves the low thrombogeneity of the system. Similarly, infectious complications were observed less frequently when compared with other systems for mechanical circulatory support [2, 9]. The incidence of liver failure is comparable to that observed among patients supported with the Thoratec biventricular device [2], although the TAH collective had higher preoperative risk factors. However, bilirubin values 6 and 14 days after implantation were higher among Thoratec patients and had generally normalized after 30 days of support. The bilirubin values obtained 14 days postimplantation differed significantly between survivors (1.7 ± 6 mg/dL) and nonsurvivors (5.2 ± 10 mg/dL) (p < 0.01).

In our institution, patients who suffer from fulminant myocarditis and are in need of mechanical circulatory support usually receive a ventricular assist device as a bridge to recovery. However, four patients of our cohort had suffered fulminant myocarditis; in three of them a giant cell myocarditis was present, which makes a recovery very unlikely. The other patient had been supported with a different device due to severe cardiogenic shock and was switched to the CardioWest because of thrombus formation in the left atrium. This patient, however, died from multiple organ failure.

Our experience strongly recommends the further evaluation of the total artificial heart concept in the management of patients with cardiogenic shock after acute myocardial infarction and postcardiotomy heart failure. As far as other patients (eg, with idiopathic dilated or ischemic cardiomyopathy) are concerned, a prospective, randomized study is highly recommended to find out whether they are more likely to benefit from a total artificial heart or from biventricular support.

	Acknowledgments

Top Abstract Introduction Patients and Methods Results Comment Acknowledgments References

 
Grant support was given by the German Association of Organ Recipients (Registered Association).

	References

Top Abstract Introduction Patients and Methods Results Comment Acknowledgments References

 

1. Copeland JG, Arabia FA, Tsau PH, et al. Total artificial heartsbridge to transplantation. Cardiol Clin 2003;21:105-117.
2. El-Banayosy A, Koerfer R, Arusoglu L, et al. Device and patient management in a bridge-to-transplant setting Ann Thorac Surg 2001;71:S98-S102.[Abstract/Free Full Text]
3. Jurmann MJ, Weng Y, Drews T, Pasic M, Hennig E, Hetzer R. Permanent mechanical circulatory support in patients of advanced age Eur J Cardiothorac Surg 2004;25:610-618.[Abstract/Free Full Text]
4. El-Banayosy A, Arusoglu L, Kizner L, et al. Predictors of survival in patients bridged to transplantation with the Thoratec VAD devicea single-center retrospective study on more than 100 patients. J Heart Lung Transplant 2000;19:964-968.[Medline]
5. Copeland JG, Smith RG, Arabia FA, et al. Cardiac replacement with a total artificial heart as a bridge to transplantation N Engl J Med 2004;351:859-867.[Medline]
6. Neumann FJ, Ott I, Gawaz M, et al. Cardiac release of cytokines and inflammatory responses in acute myocardial infarction Circulation 1995;92:748-755.[Abstract/Free Full Text]
7. Leprince P, Bonnet N, Rama A, et al. Bridge to transplantation with the Jarvik-7 (CardioWest) total artificial hearta single-center 15-year experience. J Heart Lung Transplant 2003;22:1296-1303.[Medline]
8. Copeland JG, Smith RG, Arabia FA, et al. Comparison of the CardioWest total artificial heart, the Novacor left ventricular assist system and the Thoratec ventricular assist system in bridge to transplantation Ann Thorac Surg 2001;71:S92-S97.[Abstract/Free Full Text]
9. Holman WL, Rayburn BK, McGiffin DC, et al. Infection in ventricular assist devicesprevention and treatment. Ann Thorac Surg 2003;75(suppl 6):S48-S57.[Abstract/Free Full Text]

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