Hemopump treatment in patients with postcardiotomy heart failure

Hemopump Treatment in Patients With Postcardiotomy Heart Failure Urban L6nn, MD, Bengt Peterz6n, MD, Hans Granfeldt, MD, Ankica Babic, PhD, and Henrik Casimir-Ahn, MD, PhD Link6ping Heart Center, University of Link6ping, Link6ping, Sweden

Background. This study examined the use of the Hem o p u m p to treat low cardiac output syndrome after cardiopulmonary bypass. Methods. We used the H e m o p u m p temporary cardiac assist system in 29 patients with severe left ventricular dysfunction after open heart operations from September 1991 to N o v e m b e r 1994. Results. Five patients were excluded from the study due to initial patient/device-related problems. Ten patients died in the operating room or early during the stay in the intensive care unit due to progressive biventricular failure. Fourteen patients (58.3%) were weaned from the device, and all of them were later discharged. In a

subgroup of patients (54%) in w h o m w e had a more aggressive approach for early insertion of the pump, the survival rate was 85%. Preoperative Higging risk score was significantly related to survival. Conclusions. The H e m o p u m p can effectively unload a failing left ventricle with preservation of multiorgan perfusion. A minor decrease in kidney function was observed in most patients, but none of the surviving patients needed hemodialysis. One patient required a short period of peritoneal dialysis to get rid of fluid overload. H e m o l y s i s or platelet dysfunction was not a clinical problem.

ow cardiac output syndrome immediately after card i o p u l m o n a r y bypass (CPB) is a difficult task to handle. Treatment involves pharmacologic and metabolic therapy. Sometimes one has to consider mechanical support, such as the intraaortic balloon pump, or prolonged bypass, for example with the Biomedicus pump. The H e m o p u m p (HP) temporary cardiac assist system (Johnson & Johnson lnterventional Systems) was introduced as an alternative method to the aforementioned strategy [1-5]. The most effective p u m p gives a continuous flow of about 5.5 L/rain i n d e p e n d e n t of the heart's own rhythm and is nearly as feasible to use as an intraaortic balloon pump. Still it has a flow capacity similar to that of a left ventricular assist device (LVAD). The indication has not vet been clearly defined. In this article we describe our initial experience with using the HP for postcardiotomy left ventricular (LV) failure after coronary artery bypass grafting. Our basic questions were: (1) Can the HP system effectively unload a failing left ventricle? (2) Can it provide sufficient support to the systemic circulation? (3) What is the trauma to red blood cells and platelets? (4) Are there some major device-related complications, or can it be used safely in high-risk patients to ensure a favorable patient outcome?

dysfunction after open heart operations. Five patients were excluded due to patient/device-related problems. In 3 of those patients we were not able to insert the device into the femoral artery~ due to severe arteriosclerosis. In 2 additional patients we had early cable fractures due to m i s h a n d l i n g of the catheter. In the r e m a i n i n g 24 patients we were able to place the device in a proper way. Patient demographics are summarized in Table 1.

L

M a t e r i a l and M e t h o d s From September 1991 to November 1994 we have used the HP system in 29 patients with severe left ventricular A c c e p t e d for p u b l i c a t i o n Ma~ l l, ]~)qS. A d d r e s s r e p r i n t requeM,, to I)r Id~nn, I inkiiping H e a r t ( e n t e r , Universitx ttospital, 581 ~5 I.ink6ping, S ~ e d c n .

© 1995 bv The Societx of Thoracic Sur~eon~

(Ann Thorac Surg 1995;60:1067-71)

Operating Principles of the Hemopump The system has shown a capability to decompress and unload a failing LV supporting the systemic circulation [1-5]. This is done by a catheter placed into the aorta either by a small cutdown into the femoral artery or by insertion through the arch of the aorta. At the tip of the catheter there is an axial-flow p u m p driven by a small electromagnetic motor. The p u m p speed can be adjusted stepwise from approximately 17,000 up to 25,000 revolutions per minute. The p u m p is covered by a cannula, and its tip end is positioned into the LV. The blood is sucked out of the failing LV a n d ejected out with continuous flow into the aorta (Figs 1, 2). On-off tests, fluoroscopy, or ultrasound was used to confirm correct position of the pump. In this study two different models of the HP were used. In the first 10 patients the HP-21 was the only p u m p available (see Fig 1). This p u m p is designed to be placed through a cutdown into the femoral artery a n d then advanced through the aorta, and gives a flow of about 3.5 L/min [11. After the introduction of the HP-31 (see Fig 2), with a shorter cannula, modified pump, a n d a higher flow capacity up to about 5.5 Lhnin, we started using this model routinely. This device is placed through a graft sutured to the ascending aorta. 0003-4975/95/$9.50 SSDI 0003-4975(95)00582-6

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LONNET AL HEMOPUMP [N CARDIAC [)YSFUNCT1ON

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Table 1. Summary of Data and Pro(edures for 24 of 29 Patients Variable

Value

Patients Excluded (see text) Remaining patients Sex Male Female Age (y) Mean Range Diagnosis Angina pectoris Unstable angina pectoris Mitral insufficiency + angina pectoris Failed PTCA (urgent) Preop EF (accessible in 13 patients) Mean Range Preop NYHA class

29 5 24

1

11 Ill

IV Preop Higgins score Mean Range Procedure CABG CABG ~ mitral valve repair CABG + mitral valve repair ~ ASD closure Coronary artery ostial plastic surgery Grafts Mean Range IMA

21 3 64.9 55-79 10 11 2 1 0.38% 0.20- 0.60

0 3 10

11 5.8 0-13 21 1 1 1

Fix, l. Hemopump HP-21 femoral catheter in position within the heart, and its hmction. (Photograph provided courtesy of Medtronic, Ira, Hemodynamics Division.)

dioplegic solution (Plegisol, A b b o t Laboratories, North Chicago, IL) given in a n a n t e g r a d e or retrograde m a n n e r , a n d with m o d e r a t e h y p o t h e r m i a (30 ° to 32°C). The patients were fully h e p a r i n i z e d u s i n g regular CPB e q u i p m e n t i n c l u d i n g a m e m b r a n e oxygenator. W h e n the patients failed to come off CPB at first attempt, a n a d d i t i o n a l 3 0 - m i n u t e r e p e r f u s i o n was carried out on full bypass. A

3.5 1- 6 83 ~',,

plug

ASD atrial septal defect; CABG:. cllronarv artery bvpass grafting; EF - ejection fraction; IMA internal mammary artery; NYftA New York Heart Association; P T C A percutaneous transluminal coronary angioplasty.

Indications f o r H e m o p u m p T r e a t m e n t All patients h a d severe LV failure, isolated or in combin a t i o n with i s c h e m i a a n d right v e n t r i c u l a r failure. They all h a d adverse or insufficient r e s p o n s e to the p h a r m a cologic therapy• M a n y of the p a t i e n t s were totally p u m p d e p e n d e n t w h e n CPB was d i s c o n t i n u e d . A n e s t h e s i a and Surgical Procedure P r e m e d i c a t i o n a n d general a n e s t h e s i a were p e r f o r m e d according to o u r routines, ie, h i g h - d o s e fentanyl or with s t a n d a r d anesthetic t e c h n i q u e s i n c l u d i n g fentanyl, thiopental, m i d a z o l a m or d i a z e p a m , a n d isoflurane. The p a t i e n t s were m e c h a n i c a l l v v e n t i l a t e d (Servo 900D; Siem e n s Elema, S w e d e n ) with a m i x t u r e of oxygen a n d air. Myocardial protection was achieved by crvstalloid car-

graft(/~ aorta pump

'

L~V

t ~,i~ 2. Hemopump ftP-31 ("sternotomy cannula") in position within the heart tttrou~,qz a gr~ft anastomosed at the ascending aorta. (LV = h~fi ventrich'.)

Ann Thorac Surg 1995;60:1067-71

Swan-Ganz catheter was inserted and complete control of the grafts and anastomoses was performed. At the end of this period moderate inotropic support and afterload reduction were administered. The inotropic drugs used in these patients were a combination of dobutamine, epinephrine, and phosphodiesterase inhibitors (amrinone o r m i l r i n o n e ) . A d o s e o f 8 t o 1 0 / x g - k g ~ . m i n ~of d o b u t a m i n e and 30 to 60 ng - kg ~ - rain ~ of adrenalin was considered a moderate dose. The HP was inserted when the patients failed to come off bypass the second time, or if the heart started to dilate with increasing filling pressures after the termination of CPB. Full CPB flow was reinstituted while the p u m p was inserted. W h e n the femoral HP-21 cannula was used, one of the femoral arteries was exposed and a double pursestring suture was placed around the incision site. A 1.5-cm longitudinal incision was made, and the catheter was introduced and further brought through the aorta into the LV. Roentgenography or transesophageal echocardiography was applied to ascertain correct position of the catheter. If the aortic cannula was used a 12-ram H e m a s h i l e d graft (Meadox Medicals, Oakland, NJ) was sutured to the ascending aorta, through which the HP-31 catheter could be advanced into the LV. As soon as the catheter was introduced into the aorta the HP was set to a m i n i m u m speed to prevent clot formation. W h e n an a d e q u a t e position was achieved in the LV, the p u m p was set to full speed, and CPB was gradually stopped. The systemic heparinization was reversed by protamine, and the activated clotting time was kept at 1.5 times preoperative level during the support. All patients received additional treatment with metabolic support with either a high dose of glucose-insulin-potassium or glutamate or a combination of both.

Statistics Descriptive statistics were used to s u m m a r i z e the data in terms of mean and range, and unpaired t test was used to point out the differences between the patient subgroups regarding the outcome (survival) and the time of device insertion [6].

Results Ten patients (41.7"i,) died in a picture of biventricular failure. Five patients died during the primary operation or shortly after in the operating room. Five patients had a sudden circulatory collapse in the intensive care unit (ICU) shortly after the operation. They were rapidly reopened and put on CBP betnre institution of HP treatment, some of them requiring additional coronary artery bypass grafting when occluded grafts were observed. Two of these patients could later be transferred for the second time to the ICU, but died 2 and 3 days later. Only 1 of the reoperated ICU patients survived. Fourteen of 24 patients (58.3%) were early surviw)rs. All of the surviving patients started to show signs of recovery within the first 24 hours of treatment. This could be detected as own p u m p i n g activity on the arterial

LONN ET AL HEMOPUMP IN CARDIAC DYSFUNCTION

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Tabh, 2. Biochemical Findings: Preoperahve, Maximum Postoperative, and at Discharge From the Hospital '~ Variable s-CREA (~mol/L; RV 50-115) s-UREA (mmol/L; RV 3.0 -9.O) Platelets (y. 10"/L; RV~ 150-350) Pf-Hb (g/L; RV ~ 0.05) ASAT (/,kat/L; RV ..... 0.7) ALAT (/xkat/L; RV • : 0.7)

Preop

Max Postop

Discharge

101 (80-125)

177 (94-301)

96 (72-185)

NA

13.6 (4.7-23.5)

10.1 (3.5-21.6)

237 (153-446)

53 (28-88)

438 (19-675)

NA

0.32 (0.05-0.67) 0.05 (0.02-0.13)

0.95 (0.26-3.7} 5.74 (1.0-21.0)

0.64 (0.16-1.1)

1.42 (0.23-4.3) 2.55 (0.58-19.0) 1.11 (0.34-2.3)

Values are shown as mean with range in parentheses. ALA[ alanine aminotransferase; ASAT aspartate arninotransferase; Max maximum; NA not available; Pf-Hb - plasma tree hemoglobin; Postop postoperative; Preop preoperative; s-CREA serum creatinine; s-UREA s e r u m urea.

pressure monitor with " n o t c h e s " on the pressure line. Cardiac output m e a s u r e m e n t was not reliable, probably due to interference b et w een two p u m p i n g systems, the heart and the HP. The m e t h o d that c o r r e s p o n d e d best to the patients' clinical situation was continuous m e a s u r e ment of mixed venous oxygen saturation. Although some patients showed early recovery, none was w e a n e d before at least 24 hours of treatment. The weaning procedure was p e r f o r m e d with stepwise decrease of the p u m p speed during 6 to 8 hours. W h e n m i n i m u m speed was reached the HP catheter was withdrawn into the descending aorta and kept there for an additional 2 hours in case the device should be n e e d e d again. The HP-21 p u m p was withdrawn through a cutdown in the groin at the ICU. When the HP-31 was used, the patient was taken to the operating room for resternotomy and the p u m p was removed. The aortomy was then d o s e d or the graft just ligated near the aorta. The HP system very effectively u n l o a d e d the failing heart. During the first 10 to 12 hours an almost flat arterial line was seen on the blood pressure monitor. A checkup with Doppler ultrasound showed that the aortic valve cusps were closed around the HP cannula. Mean arterial pressure was very low, 50 m m Hg or less, during the first hours of support, probably partly due to complete continuous blood flow in the systemic circulation and vasodilation as an effect of metabolic support with glucose-insulin-potassium. To keep mean arterial pressure greater than 50 m m Hg, vasoconstrictive drugs were frequently needed. Low urinary output was not a clinical problem, and the kidneys r e s p o n d e d well to diuretic drugs. There was some decrease in kidney function in all surviving patients, but none of them n e e d e d hemodialysis. O n e patient had a short period of peritoneal dialysis to get rid of some fluid overload. Levels of ser um creatinine and serum urea are shown in Table 2.

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Table 3. Statistically Relevant Findin<%~sRegarding, Patient Outcome and Hemopump Insertion Variable Age (p 0.02) Survivors Nonsurvivors Higgins score (p 0.04) Survivors Nonsurvivors ASAT"~(p 0.05) Early intervention Late intervention

Mean (Range) 65 (55-79) 62 (55-76) 70 (57-79) 5.8 (0-13) 4.5 (0-9) 7.5 (2-13) 4.6 (1.0-8.9) 10.1 (3.4-21.0)

<~Maximum postoperative value. ASAT :: aspartate aminotransferase.

Hemolysis and platelet dysfunction were not a clinical problem, although the levels of plasma free hemoglobin rose in all patients and the thrombocyte count dropped significantly (see Table 2). Even if few in n u m b e r , the platelets seemed to function well. During the ICU stay, 5 patients had to be reoperated on due to pericardial effusion compressing the right side of the heart causing diastolic dysfunction. Enzyme activity is indicated in Table 2. The m e d i a n 1CU time was 7.5 days (range, 5 to 28 days). One patient had the HP system as a bridge to a more long-term system, the HeartMate LVAD (ThermoCardiosystems Inc, Woburn, MA). He later received a transplant and was discharged. That is the explanation of the wide range of time in ICU and in the hospital stay. All patients who were weaned from the HP were later discharged from the hospital. They had the HP treatment ongoing for an average of 2.4 days, ranging from 1 to 3 days. Their total hospital stay was on average 19.5 days (range, 12 to 85 days). The Higgins score showed a statistically significant difference (p 0.045), where the mean value for the survivors was 4.5 (range, 0 to 9) and for the nonsurvivors 7.5 (range, 2 to 13). There was also statistically significant effect (p 0.02) of age: survivors, mean of 61.7 years (range, 55 to 76 years) and nonsurvivors, 69.5 years (range, 57 to 79 years) (Table 3). There were 13 patients who had the HP inserted in association with the primary operation without a prolonged delay and considered as having an early intervention. Eleven of those patients (85%) survived. Eleven patients had the HP late after prolonged CPB with metabolic intervention or shortly after arrival in the ICU. Of those patients regarding to have had late intervention only 3 (28%) survived. Figure 3 shows trends of mean arterial pressure and mixed venous oxygen saturation in the survivors and nonsurvivors, respectively. There were differences in behavior in these groups after stabilization of the hemodynamics with proper function of the HP. Nonsurvivors had an u n c h a n g e d mixed venous oxygen saturation and a slow decrease in mean arterial presstire, indicating that

the HP treatment could not restore adequate circulation. Maintained mean arterial pressure with a slow increase in mixed venous oxygen saturation was prognostically favorable for ultimate survival. Looking at the m a x i m u m postoperative value of the enzyme aspartate aminotransferase as an indicator of heart damage, there were only values for 3 patients in the late intervention group. Comparing these values with the early intervention group showed that the late intervention group had statistically higher values postoperatively: early intervention mean, 4.6 tzkat/L (range, 1.0-8.9/zkat/ L); late intervention mean, 10.1 /~kat/L (range, 3.4 to 21.0 tLkat/L; p = 0.05) (see Table 3). We had very few problems with the HP system. A thrombus was found after HP removal in 1 patient. This thrombus was attached to the drive cable. One patient had a lesion in the femoral artery at the implantation site, which required a reconstructive operation using a vein patch. There were no problems with infections or compromised circulation in the leg. The drive unit was silent and without technical problems.

Comment In this group the first 10 patients had the femoral HP-21 catheter; all the rest were treated with the HP-31 aortic cannula. The reason is that this p u m p has a higher flow capacity and is more easy to handle and get into an adequate position. You can either feel the p u m p house above the aortic valve between your fingers or see the whole catheter with transesophageal ultrasound. It is of course an inconvenience to have to remove the device by a resternotomy. We had, however, no complications related to the reoperation, and all the recovering patients u n d e r w e n t an uneventful postoperative course without any infections. When the HP was in a correct position it effectively unloaded the LV, as has been reported earlier [1, 3]. A concomitant reduction in the wall tension should decrease the oxygen d e m a n d and increase the perfusion of the subendocardial tissue [7], which could be beneficial for impaired LVs with initially high filling pressures. An increase in myocardial perfusion pressure and a decrease in myocardial oxygen consumption during HP treatment of experimental cardiogenic shock have been reported ]8]. One major advantage of the HP is that it is so effective in supporting the systemic circulation, while letting the LV be in a state of " e m p t y beating," that only low doses of inotropic drugs are needed. We used such drugs mostly to ensure adequate right ventricular performance. The patients who had progressive right ventricular failure did not, however, respond to pharmacologic therapy, and there was a successive decrease in flow through the pulmonary vascular bed to the LV with ultimate failure of HP treatment. We did not use any right ventricular assist in this study. The laboratory findings and the good status of the surviving patients at discharge indicate that the systemic circulation was sufficient during HP support. We are now p l a n n i n g a follow-up study to assess late outcome of this

Ann Thorac Surg 1995;60:1067-71

[mmHg]

HEMOPUMP

85 80 75 70 65 60 55 50 45 MAP1 66 64

Q•

'lAD2

~

MAP2

Survivors

62 6O 58 56 54 52 5O 48 46

SVO2 1

~V,O: ,:

81202 3

Fig 3. 771ree measurements: (1) baseline Ifirst v,duc recorded ~!ficr introduction of a Swan-Gmlz cnt/leter), ~2~ just heh~re insertion of &e Hemopump, and G)first shlbh, mvasurcnlent with the Hcmopump on hdl speed. (MAP mvml m'terial pressure; SVO2 lllix¢'d Pf'llOllS O.YL/~t'll sl#llrl#iOll.)

t r e a t m e n t , especially r e g a r d i n g cardiac function, cognitive function, a n d quality of life. The s t a n d a r d w a y of treating these p a t i e n t s had b e e n to use the intraaortic balloon p u m p or a m o r e e s t a b l i s h e d LVAD. M a n y of o u r patients w e r e initially totally d e p e n d e n t on the HP, so the a l t e r n a t i v e for t h e m w o u l d h a v e b e e n a n o t h e r LVAD. The overall use of an LVAD is often r e p o r t e d to be a b o u t 1.0%, and the LVAD registry rep o r t e d a survival of 25.5% in 1989 ]9]. P e r h a p s the HP s h o u l d be r e g a r d e d as a m o r e feasible alternative to the c u r r e n t LVADs and as such be i n c l u d e d in a r a n d o m i z e d study. From 1991 t h r o u g h 1994 we h a v e u s e d 48 m e c h a n ical d e v i c e s i n c l u d i n g the intraaortic balloon p u m p during 2,603 o p e n heart p r o c e d u r e s . That m a k e s the incid e n c e of m e c h a n i c a l s u p p o r t 1.8,, a n d HP s u p p o r t 1.0",, in our total material d u r i n g this time. It is, h o w e v e r , p r o b a b l e that our m a t e r i a l i n c l u d e s all patients w h o w o u l d h a v e n e e d e d an LVAD, b e c a u s e we h a v e not u s e d any o t h e r such device, and also a g r o u p of patients in w h o m the intraaortic balloon p u m p w o u l d h a v e b e e n c h o s e n if the HP had not b e e n available. A r a n d o m i z e d c o m p a r i s o n b e t w e e n H P and intraaortic balloon p u m p a n d H P a n d an LVAD, respectively, s h o u l d be p e r f o r m e d on a m u l t i c e n t e r basis b e f o r e differences in p a t i e n t outc o m e can be c l a i m e d .

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It was s o m e t i m e s difficult to get the HP-21 p u m p t h r o u g h the aorta to the LV. C o n c o m i t a n t c o m p r e s s i o n of the arch vessels facilitated this m a n e u v e r . In 3 p a t i e n t s w h o w e r e e x c l u d e d f r o m this s t u d y it was i m p o s s i b l e to pass the pelvic vessels. W a m p l e r a n d associates [5] rep o r t e d this p h e n o m e n o n in 35% of the cases in t h e i r m u l t i c e n t e r trial. The short d i s t a n c e n e e d e d to i n s e r t the HP-31 d e v i c e into the LV was a clear a d v a n t a g e . As it also has a h i g h e r flow capacity we n o w use it routinely. G e t t i n g the d e v i c e t h r o u g h the aortic v a l v e into the LV is a c o m m o n p r o b l e m for b o t h m o d e l s , b e c a u s e the tip of the c a t h e t e r t e n d s to stick in o n e of the s i n u s e s of Valsalva. C o o p e r a t i o n with the p e r f u s i o n i s t is i m p o r t a n t ; w h e n trying to pass the c a t h e t e r t h r o u g h the aortic v a l v e you m u s t be s u r e the h e a r t is filled a n d able to eject s o m e by its o w n so the v a l v e cusps o p e n . The system w o r k s a l m o s t silently a n d i n d e p e n d e n t l y f r o m the p a t i e n t ' s o w n heart r h y t h m a n d fits well into the 1CU e n v i r o n m e n t . The drive unit is easy to use a n d was w i t h o u t technical p r o b l e m s . It is not possible to clearly assess the p u m p o u t p u t in p h y s i o l o g i c values. This has to be d o n e i n d i r e c t l y by h e m o d y n a m i c m e a s u r e m e n t s . W e c o n c l u d e that the H P t e m p o r a r y cardiac assist d e v i c e can effectively u n l o a d a failing left v e n t r i c l e w h i l e m a i n t a i n i n g m u l t i o r g a n p e r f u s i o n . The p u m p s e e m s to be a n e w v a l u a b l e tool in our arsenal of t h e r a p e u t i c choices in p a t i e n t s with potentially r e v e r s i b l e cardiac failure. It is n e a r l y as feasible to use as an intraaortic balloon p u m p b u t still has a s u p p o r t capacity similar to that of an LVAD.

this investigation was supported by grants from the Linkaping Heart Center Fund, Sweden.

References 1. Wampler RK, Moise JC, Frazier OH, Olsen DB. In vivo evaluation of a peripheral vascular access axial flow blood pump. ASAIO Trans 1988;34:450-4. 2. Rutan PM, Rountree WD, Myers KK, Baker LE. Initial experience with the Hemopump. Crit Care Nurs North Am 1989;1:527-34. 3. Frazier OH, Wampler RK, Duncan JM, et al. First human use of the Hemopump, a catheter-mounted ventricular assist device. Ann Thorac Surg 1990;49:299-304. 4. Butler KC, Moise JC, Wampler RK. The Hemopump--a new cardiac prosthesis device. IEEE Trans Biomed Eng 1990;37: 193-6. 5. Wampler RK, Frazier OH, Lansing AM, et al. Treatment of cardiogenic shock with the Hemopump left ventricular assist device. Ann Thorac Surg 1991;52:506-13. 6. Abacus Concepts, Statview. Berkely, CA: Abacus Concepts, 1992. 7. Hoffman lIE, Buckberg GD. Transmural variation in myocardial perfusion. In: Yu PN, Goodwin JF, eds. Progress in Cardiology. Philadelphia: Lea & Febiger, 1976;5:37-89. 8. Scholtz KH, Hering JP, Schr6der T, et al. Protective effects of the Hemopump left ventricular assist device in experimental cardiogenic shock. Eur J Cardiothorac Surg 1992;6:209-14. q. Pae WE, Pierce WS. Combined Registry for the Clinical Use of Mechanical Ventricular Assist Pumps and the Total Artificial Heart: third official report--1988. Trans Am Soc Artif Intern Organs 1990;36:43-6.