[Cardiac substitution by epicardial prosthesis. Stage II. Adaptation of the vascular system to a pulsating artificial circulation].
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Improvements in both mechanical circulatory support devices and immune therapy promise a wider use of sequential mechanical support as a bridge to orthotopic cardiac transplantation. The intra-aortic balloon pump, the left and right ventricular assist pumps, and the pneumatic artificial heart represent the range of devices capable of keeping a patient alive who is awaiting a donor organ. The major difficulty in using circulatory support devices is infection, which is caused by their required percutaneous tubes. We report here our experiences with mechanical circulatory support devices as a bridge to cardiac transplantation. In a series of 31 consecutive transplant procedures, six patients have required preoperative mechanical circulatory support. The intra-aortic balloon pump was used in two patients for 2 and 14 days, respectively, before transplantation. Both patients are well 10 and 11 months after the transplant procedure. Two patients required the left ventricular assist device for 11 and 21 days and are alive 3 weeks and 8 months, respectively, after transplantation. One patient was supported by the pneumatic artificial heart for 10 days before a donor heart became available but died of septic shock 17 days after transplantation. A second patient received a pneumatic artificial heart 7 days after transplantation when the heart transplant failed. He has been in stable condition for 45 days but is recovering from renal failure. Our early experiences indicate that either partial or total mechanical support as a bridge to transplantation is successful if overwhelming sepsis or renal failure can be avoided.
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BACKGROUND: After open heart operations about 1% of patients still need temporary circulatory support for severe cardiac failure, and over half of those patients die during or after the support. This study assessed the efficacy of the current strategy of circulatory support. METHODS: We assessed clinical outcome of 64 consecutive patients (1.5% of pump cases) who had temporary circulatory support associated with perioperative variables. The results were analyzed by logistic regression analysis. RESULTS: The weaning and discharge rates were 50.0% and 26.7% with venoarterial bypass, 76.2% and 57.1% with biventricular bypass, 87.5% and 37.5% with isolated left ventricular bypass, and 60.0% and 40.0% with pulsatile left ventricular assistance, respectively. Logistic regression analysis identified presupport cardiogenic shock (odds ratio, 9.922) and support type (14.684) as factors significantly associated with nonweaning from the temporary support, and cardiogenic shock (28.268), support duration (2.948), and support type (14.184) as factors significantly associated with mortality during or after the circulatory support. CONCLUSIONS: The current strategy of temporary circulatory support improved clinical outcome of patients with severe cardiac failure. Early application of circulatory support before profound cardiogenic shock and proper selection of the support type might be key factors for successful circulatory support postoperatively after operation.
BACKGROUND: We developed a prosthetic left ventricle (LV) to coronary sinus (CS) shunt (LVCSS) that is autoregulating and provides LV-powered retrograde perfusion of the coronary sinus. METHODS: Each of 20 Yorkshire pigs underwent 1 hour of left anterior descending diagonal artery occlusion followed by 3 hours of reperfusion. The controls (n = 5) did not have shunt treatment. The LVCSS group (n = 9) underwent shunt treatment during the ischemic period. The LVCSS with partial coronary sinus occlusion (PCSO) group (LVCSS+PCSO, n = 6) underwent shunt treatment and PCSO during the ischemic period. Vital staining and planimetry techniques were used to determine the area at risk for infarction and the area of necrosis. RESULTS: The area at risk was not significantly different among groups. The area of necrosis was decreased by 53% in the LVCSS group and by 73% in the LVCSS+PCSO group when compared to controls (p<0.01 among all groups). CONCLUSIONS: The LVCSS reduces infarct size in pigs after acute coronary artery occlusion. The addition of PCSO to LVCSS further improves myocardial salvage.
A 53 year old man underwent repeat coronary artery bypass graft surgery after presenting with unstable angina. Because of intraoperative ischemia, the patient developed profound left ventricular dysfunction requiring placement of a left ventricular assist device and intraaortic balloon pump and catecholamine infusion. Serial radionuclide ventriculograms documented delayed recovery of the severely stunned myocardium with mechanical and pharmacologic support.
We describe our clinical experience with 205 implantable left ventricular assist devices at the Cleveland Clinic between December 1991 and January 2000, along with manufacturers' data submitted to the Food and Drug Administration. In patients with end-stage cardiac failure who are suitable candidates for transplantation, these devices serve as excellent bridges to transplantation. Recent modifications have increased pump reliability and reduced thromboembolic rates. The vented electric HeartMate (Thermocardiosystems Inc, Woburn, MA) and the Novacor (Baxter-Novacor, Oakland, CA) left ventricular assist systems allow patients to be discharged from the hospital while awaiting a donor heart. Experience with long-term support is providing insights into permanent implantation of these devices as destination therapy. Although infection remains a major impediment to long-term support, patient-pump interactions leading to changes in the coagulation and immune systems are being recognized, and these interactions may have important implications with respect to thromboembolism, infection, and sensitization to human leukocyte antigens (HLAs). Better understanding of these factors may eventually lead to the development of permanently implantable pumps as an alternative to transplantation.
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Although it is now possible to obtain, with mechanical circulatory support devices, survival of postcardiotomy patients who develop profound cardiogenic shock, their long-term functional status has not been firmly established. We studied 22 patients who survived cardiac operations by the use of circulatory support devices. Their ages ranged from 3 days to 69 years at the time of device support. Operations performed were coronary artery bypass (9 pts), valve replacement (4 pts), congenital defect correction (8 pts), and cardiac transplantation (1 pt). Ten patients were supported with a Pierce-Donachy ventricular assist device (VAD) (left 4, right 3, both 3), nine with extracorporeal membrane oxygenation (ECMO), and three with centrifugal pumps (left 2, both 1). Duration of support ranged from 22 to 189 hours (mean 84.4). There were four late deaths; two of the deaths were cardiac-related within 6 months and two were due to cancer at 46 and 53 months following discharge. The remaining 18 survivors were followed for 6 to 74 months (mean 29.9). Prior to operation three of the patients were New York Heart Association (NYHA) Class I, eight were Class II, six patients were Class III, and five were Class IV. Following discharge from the hospital 13 patients were Class I, two were Class II, and three were Class III; no patients were Class IV. Five patients work full-time, three are retired without limitation, four attend school, and three are pre-school. Only three patients suffer from moderate cardiac disability. These data suggest that patients surviving mechanical circulatory assistance for postoperative cardiogenic shock have an excellent chance for functional recovery.
Eleven infants weighing 2.3 to 7.8 kg underwent mechanical circulatory support for post cardiotomy cardiogenic shock. Initiated pre-operatively in two patients, extracorporeal membrane oxygenation was used in a total of eight patients aged 6 days to 3 months in association with repair of cyanotic congenital heart disease with increased pulmonary blood flow or with a right sided obstructive lesion. Ventricular assist devices were used in three other patients: a centrifugal left ventricular assist device in Patient 1 (10 months, 5.7 kg) after repair of the anomalous left coronary artery, and a pneumatic biventricular assist device (stroke volume 12 ml) in Patient 2 (6 months, 7.0 kg) for cardiac arrest after closure of ventricular septal defect and in Patient 3 (10 months, 7.8 kg) for post transplant graft failure. Duration of extracorporeal membrane oxygenation duration ranged from 26 to 192 hr (mean, 88 hr). Three patients were weaned from extracorporeal membrane oxygenation and two survived. Two others were separated from extracorporeal membrane oxygenation because of bleeding, but both subsequently died. Patient 1 was weaned from the left ventricular assist device after 192 hr and discharged from the hospital. Support was discontinued after 45 hr in Patient 2 who exhibited irreversible brain damage. Patient 3 was weaned from a biventricular assist device after 174 hr, but suffered recurrent graft failure. Our results show that an appropriate circulatory support system should be selected according to the cardiac anatomy in infants.
Surface roughness of a blood pump is an important factor for blood cell damage. This study investigated the effect of surface roughness pertaining to hemolysis in a centrifugal pump. In vitro hemolysis tests were performed under cardiopulmonary bypass (CPB; 5 L/min, 350 mmHg) and left ventricular assist device (LVAD; 5 L/min, 100 mmHg) conditions using the pivot bearing supported Gyro centrifugal pump (C1E3). Seven types of pumps with impellers and housings with different surface roughness were prepared as follows: vapor polish (VP) housing and VP impeller; VP housing and sandpaper (SP) impeller; VP housing and fine sandblasting (FSB) impeller; VP housing and coarse sandblasting (CSB) impeller; SP housing and VP impeller; FSB housing and VP impeller; and CSB housing and VP impeller. The results revealed that 1) the effect of surface roughness on hemolysis was significantly larger with CPB than LVAD; 2) surface roughness, regardless of the impeller or housing, had little effect on hemolysis with LVAD; and 3) during CPB, the surface roughness of the pump housing had a larger effect on hemolysis than did that of the impeller. In conclusion, from a hemolytic point of view, it is likely that an extremely smooth pump housing is required for an impeller centrifugal pump for CPB. However, it is likely that a smooth surface is not as essential for this impeller centrifugal pump as for an LVAD.
A multiple disk, shear force, valveless centrifugal pump was studied to determine its suitability as a blood flow device. A pulsatile version of the Tesla viscous flow turbine was designed by modifying the original steady flow pump concept to produce physiological pressures and flows with the aid of controlling circuitry. Pressures and flows from this pump were compared to a Harvard Apparatus pulsatile piston pump. Both pumps were connected to an artificial circulatory system. Frequency and systolic duration were varied over a range of physiological conditions for both pumps. The results indicated that the Tesla pump, operating in a pulsatile mode, is capable of producing physiologic pressures and flows similar to the Harvard pump and other pulsatile blood pumps.