Use Of Ventricular Assist Devices Research Articles

Ventricular assist devices as a bridge to cardiac transplantation. A prelude to destination therapy.

Ventricular assist devices (VADs) have been used for temporary circulatory support pending transplantation or recovery of the native heart. Outcome in 38 patients treated at the authors' institution with VADs pending transplantation was analyzed to provide information relevant to the future use of VADs as permanent implants. Thoratec (Thoratec Laboratories, Pleasanton, CA) or HeartMate (Thermo Cardiosystems, Woburn, MA) VADs were used in all cases. Patients were considered for VAD placement if they were candidates for cardiac transplantation and fulfilled the criteria for the Food and Drug Administration investigational Device Exemption trials. The following adverse events were included in the analysis; death during VAD support, device malfunction, bleeding, neurologic events, support-related events that preclude transplantation, and device-related infections. Patient survival and complication rates were quantified using the Kaplan-Meier method, competing risk analysis, and hazard functions. Nineteen patients had transplantation. Three patients had VAD removal after cardiac recovery and 16 died without transplantation. The duration of VAD support ranged from 0 to 279 days. The hazard function for death during VAD support had an early phase that lasted for 2 weeks after VAD placement, and early death was related to the preimplant condition of the patient. Device-related infections were noted in 11 patients. Seven of these patients had transplantation after clearing the infection, whereas four died without transplantation. Neurologic events occurred in seven patients. There were no device malfunctions that led to patient death. The absence of fatal device malfunctions suggests that longer term support with current VAD designs is feasible. Appropriate patient selection, infection control, and avoidance of thromboembolic neurologic complications will be crucial to the success of permanent VAD use.

Results of extended bridge to transplantation: Window into the future of permanent ventricular assist devices

There is interest in expanding ventricular assist device use from short-term bridging to transplantation to long-term and permanent support. We have reviewed the outcome of 162 patients who had as mechanical bridge to transplantation that lasted at least 60 days. Eighty-five patients received the HeartMate, 40 the Novacor, and 37 the Thoratec device. Of the 162 patients, 125 received transplants, and 115 survived after transplantation (93%). Within the group there were 174 complications including 54 infections of the driveline, 73 other infections, and thromboembolic strokes in 47. Infections of the driveline were considered major in 24 of 54 cases, and other infections were major in 36 of 73 cases. Twenty-seven of those who sustained thromboembolic events had residual effects. Of 11 patients with a major stroke and infection, only 1 survived transplantation. Eighty-two patients were supported between 60 and 100 days, 63 patients between 101 and 200 days, 12 patients between 201 and 300 days, and only 5 patients in excess of 300 days. A greater percentage of candidates died waiting between 101 and 200 days than between 60 and 100 days (25% versus 10%). The incidence of complications also rose in those patients bridged more than 100 days. The data reinforce the excellent results obtained in the bridge to transplantation trials that reported a shorter duration of support. For those interested in extended bridge to transplantation or permanent use of the currently available devices, the results suggest reasonable success can be anticipated, but the serious infections and strokes tend to be more common with longer duration of support.

Right-to-left veno-arterial shunting for right-sided circulatory failure

Right-sided circulatory failure, a complication of heart transplantation and left ventricular assist device use, results in decreased cardiac output due to diminished flow across the pulmonary circuit. We hypothesized that creation of a controlled right-to-left shunt would result in decompression of the right ventricle and improved systemic cardiac output at tolerable oxygen saturations. We also hypothesized that a peripheral veno-arterial shunt is physiologically superior to a central shunt. Right atrial-femoral artery and right atrial-left atrial shunts were created in a large animal model (calf). Right-sided circulatory failure was induced by banding the pulmonary artery. Hemodynamic measures and blood gas determinations were obtained during nonshunted and shunted states. Peripheral and central shunts resulted in decreased right-sided pressures and increased cardiac output. Arterial oxygen saturation remained greater than 90% during shunting. The peripheral shunt had the added advantage of decreasing left ventricular end-diastolic pressure and left ventricular stroke work. A controlled right-to-left shunt improved hemodynamics and cardiac output in a large animal model with right-sided circulatory failure. This strategy may be useful in the management of transplant and left ventricular assist device recipients with perioperative right-sided circulatory failure. Our studies also indicate that creation of a peripheral shunt has both physiologic and technical advantages over a central shunt.

Long-term left ventricular assist device use before transplantation.

Between September 1992 and April 1995, 19 patients at the authors' institution received pneumatic, pulsatile left ventricular assist devices (LVADs) for bridging to cardiac transplantation. The mean (+/- SD) age of the patients was 51 +/- 14 years (range, 19-64 years). Nine (47%) patients had end-stage idiopathic cardiomyopathy, five (26%) had ischemic cardiomyopathy, and five (26%) other recipients were in cardiogenic shock caused by acute myocardial infarction (AMI). Fifteen (79%) patients were supported with an intraaortic balloon pump or centrifugal LVAD at the time of LVAD insertion (duration, 5.5 +/- 4.1 days). Aprotinin was given to limit bleeding; heparin, followed by warfarin sodium, was used for anticoagulation. A vigorous exercise and nutrition protocol was followed. Cardiac index averaged 2.94 +/- 0.87 L/min/m2 immediately after the implantation procedure. No patient required placement of a right VAD. Average duration of LVAD support was 45 +/- 39 days (range, 3-153 days). Major complications included bleeding requiring reoperation (three patients); cerebrovascular accident (three patients); and severe dysrhythmias requiring direct current cardioversion (four patients). Fourteen (74%) patients underwent transplantation, with one patient still being mechanically supported. All of the patients receiving transplants were discharged from the hospital. Of the individuals who died while supported with the LVAD, 75% were patients with AMI. Timely application of LVADs as part of the interdisciplinary management of end-stage heart disease has generated excellent results for transplant candidates. Right ventricular dysfunction has not necessitated right VAD placement in the authors' experience. Patients with AMI have a higher risk of death while being supported with the device than do more chronically ill recipients.

Use of the Nippon-Zeon pneumatic ventricular assist device as a bridge to cardiac transplantation.

The Nippon-Zeon (NZ) ventricular assist device is a sac type, air driven, heterotopic, external pump. Its performance has been evaluated in Japan as a bridge to myocardial recovery. Few data are available on the device as a bridge to heart transplantation. Since 1991, 10 patients (9 men) were bridged to heart transplantation with NZ, all in biventricular support. The mean age was 39 +/- 13 years (range, 21-60 years), mean body weight was 75 +/- 13 kg (range, 51-95 kg). Five patients had a dilated cardiopathy, and five were ischemic (three acute myocardial infarctions). Despite maximal inotropic support, including enoximone in seven, epinephrine in three, and intraaortic balloon pumping in one, eight patients were anuric, three were in acute hepatic failure, and three were intubated. Preoperative hemodynamic and biologic values were: cardiac index, 1.57 +/- 0.4 l/min/m2; pulmonary capillary wedge pressure, 34 +/- 5 mmHg; creatinine, 200 +/- 80 mumol/l; blood urea nitrogen, 17.5 +/- 8 mmol/l; total bilirubin 36 +/- 6 mumol/l; aspartate aminotransferase, 1,000 +/- 2,000 IU/l. In all patients, a biventricular assist device was implanted without the use of cardiopulmonary bypass. Improvement occurred immediately in all but one. Mean left ventricular flow was 4.5 +/- 0.8 l/min. Anticoagulation was maintained with intravenous heparin. Recently for bleeding was required in one case (10%), and two patients had positive blood cultures that were successfully treated. There was no mechanical failure. Hemolysis was not significant (lactate dehydrogenase, 378 +/- 50 IU/l; plasma-free hemoglobin below 10 mg/dl). Each device was free of thrombi and deposits at time of explantation. One patient died while on assist. Nine patients (90%) were transplanted after 11 +/- 8 days (range, 1-32 days). Three died early after transplantation, one of graft failure, two of sepsis. Six patients (66%) could be discharged. The follow-up ranges from 7 to 28 months. NZ is a simple, reliable, pneumatic device driven by a light, silent console; it can be rapidly implanted without cardiopulmonary bypass in patients in desperate condition who are awaiting cardiac transplantation. The difficulty of patient rehabilitation while using this device should limit the duration of support to weeks to allow the patient to be in optimal condition for heart transplantation.

Potential Risk of Paradoxical Embolization during Use of a Left Ventricular Assist Device: A Case Report

A patient undergoing left ventricular assist had a complicated post-operative course due to a patent foramen ovale. This presented as a right to left shunt with desaturation of the arterial blood, and possibly contributed to paradoxical embolization resulting in neurological complications and death. A method is presented to determine the presence of a patent foramen ovale during left ventricular assist. Possible sources of embolization are discussed.

Intraoperative timing may provide criteria for use of post-cardiotomy ventricular assist devices.

When surgeons consider ventricular assist devices (VADs) for post-cardiotomy support, unnecessary delays and early use can have detrimental effects on patient outcome. The authors analyzed the timing of intraoperative events in all patients receiving post-cardiotomy VAD support at their institution during a 2-1/2 year period (N = 17). They used ability to wean patients from VAD support as a measure of outcome. Neither preoperative risk factors nor the timing of distinct intraoperative events (e.g., cross-clamp time, total bypass time, delay to VAD) significantly differed between those patients able (Group I, n = 9) and those unable (Group II, n = 8) to be weaned from VAD support. The authors did find, however, that the time intervals from completion of the cardiac procedure to insertion of either an intra-aortic balloon pump (time to IABP) or VAD (time to VAD) were predictive of outcome when normalized to the duration of the cardiac procedure (DCP). [Time to IABP]/DCP ratios of < 1.0 versus > 1.0 (p = 0.02) and [time to VAD]/DCP ratios of < 2.5 versus > 2.5 (p = 0.10) each segregated Group I and II patients, respectively. Appropriate timing criteria for VAD insertion may be predicted during surgery by consideration of the duration of the cardiac procedure. This approach may attenuate tendencies to delay VAD use without leading to premature VAD insertion in the post-cardiotomy setting.

Differential Regional Function of the Right Ventricle During the Use of a Left Ventricular Assist Device

The use of a left ventricular assist device (LVAD) as a bridge to transplant is associated with a 52% incidence of RV failure requiring additional inotropic or mechanical support (RVAD). This study evaluated the differential performance of the RV free wall and septum to identify the need for additional RV support. Cross-sectional views of the RV were obtained immediately before, and 1 hr after, Novacor LVAS implantation in 12 consecutive patients using transesophageal echocardiography. Each image was divided into a free wall portion (FW) and a septal portion (SP) by grids drawn from the center of gravity of the end-diastolic endocardial outline to the junction between the FW and the SP. Percentage change between preimplant and postimplant for RV ejection fraction (RVEF), fractional area change for the FW (FAC-FW) and the SP (FAC-SP), and fractional shortening of the FW to SP distance (F-S) is reported for patients based upon the need for RV support: minimal (Group 1), maximal (Group 2). After LVAS implantation, patients showed a reduction in SP fractional area change. However, this reduction was most pronounced in Group 2. The degree of SP impairment may explain the mechanism of RV failure in patients on an LVAD.

Forum Offers Hints of Future Therapy, Prevention Programs for Combating Cardiovascular Problems

THE LATEST cardiovascular research reports may foreshadow tomorrow's therapy and preventive strategy. For example, research involving use of ventricular-assist devices—instead of the heart-lung machine—during coronary artery bypass surgery is being reported by surgeons from the University of Texas Health Science Center, Houston. At the American Heart Association's 19th Science Writers Forum in Galveston, Tex (<i>JAMA</i>. 1992;267:335-336), Michael Sweeney, MD, said that this approach seems promising, especially now when older and/or much sicker patients are among those receiving the 368000 (1989 total) or more coronary artery bypass operations performed annually in this country. Sweeney, who is an associate professor of surgery at the university and director of thoracic and cardiovascular surgery at its Hermann Hospital, points out that—with this approach—"the patient's own lungs continue to oxygenate the blood and the ventricular-assist device partially supports cardiac function while the bypasses are completed." The heart continues to beat, but flaccidly (especially when the

Effectiveness of Ventricular Pressure-Volume Loops for the use of Ventricular Assist Device after CardiacSurgery

Effectiveness of Ventricular Pressure-Volume Loops for the use of Ventricular Assist Device after CardiacSurgery

The Role of Mechanical Devices

Devices to support the circulation and directly assist the ventricle during surgery are now both reliable and essential. The intraaortic balloon counterpulsation device is used in patients who fail to wean easily from cardiopulmonary bypass, who develop ischemia in the immediate postoperative period, or who have low output in the maximal edema phase, 4 to 8 hours postoperatively. Complications relate to the insertion of the device, which may cause major arterial disruption, lower leg ischemia, or distal arterial thromboemboli. Ventricular assist device (VAD) support is indicated when, despite the use of the intraaortic balloon, the patient's hemodynamics remain severely depressed and the patient is unable to wean from bypass. There are several contraindications to the use of VADs, including pulmonary hemorrhage. Nevertheless, as experience with the many different types of VADs increases, their use may be extended to periods of days or even months. Various mechanical support devices have been used to bridge to cardiac transplantation, with ranging degrees of success. Decisions concerning the use of mechanical devices for this purpose must take into account both the standard contraindications to transplantation, and contraindications that develop or are acquired during intervention with the bridging device. Current and future experience will decide which devices will be accepted for common clinical use.

Significance of Various Anticoagulation Therapies During Use of a Left Ventricular Assist Device

Significance of Various Anticoagulation Therapies During Use of a Left Ventricular Assist Device

Right Ventricular Failure During Clinical Use of a Left Ventricular Assist Device

The purpose of this study is to describe the authors' clinical experience of RVF during LVAD pumping and to delineate the effect of LVADs on RV function, with special reference to the level of myocardial recovery. Pneumatically driven LVADs were used on a total of 13 postoperative cases for 18 hours to 70 days (mean, 9.9 days). The RVF, which was defined as increased right atrial pressure (RAP greater than or equal to 20 mmHg) during LVAD pumping, were experienced in four cases (two ischemic, two valvular). Duration of the RVF ranged from 3 hours to 8 days (mean, 3.0 days) and the maximum RAP ranged 22-30 mmHg (mean, 27 mmHg). The effects of LVAD pumping on the RV function were delineated during serial pump on-pump off studies in two cases with RVF and three cases without RVF, in relation to off/on ratio of the systolic aortic pressure (AOP off/on), which worked as an indicative parameter of myocardial recovery. Each pair of on/off data were assigned to four groups according to AOP off/on and complication with RVF, and mean percentage changes of mRAP and PAP were compared. The RAP of RVF cases were significantly increased by 16% with the LVAD pumping when the AOP off/on was below 0.7, whereas PAP invariably decreased in most cases. The results indicated that the LVAD suppressed the RV function before the myocardial recovery and when the heart was complicated with RVF.

Prerequisites to Salvage Profound Biventricular Failure Patients with Ventricular Assist Devices

We conducted chronic experiments to determine how to treat profound biventricular failure systematically with ventricular assist devices (VADs) and to analyze the factors that affect prognoses for this condition. Anoxic arrest was induced in ten goats by aortic cross-clamping under normothermic conditions (38.5 degrees C) for 30 (n = 3), 45 (n = 1), and 60 (n = 6) minutes. A left ventricular assist device (LVAD) was implanted in eight animals, and a biventricular assist device (BVAD) was used in two. Three goats--two of which had undergone anoxic arrest for 30 minutes and one for 60 minutes--whose right atrial pressure (RAP) was approximately 18 mm Hg during the acute stage, recovered in two to three weeks, and the pumps were successfully removed. Pathological findings in these animals showed scattered areas of surviving myocardium, with connective tissue replacing the degenerated myocardium. The remaining five LVAD goats required higher RAPs to maintain circulation and died from various causes. Maintaining circulation without volume loading, even in the presence of arrhythmias, was easier with the BVAD. One BVAD animal that underwent 45 minutes of anoxic arrest recovered from right ventricular failure, and the right pump was removed. The second goat (anoxic arrest, 60 min) on the BVAD failed to recover. Autopsy of the myocardium revealed a thin ventricular wall. Our studies show that the use of VADs allows time for a failing heart to recover, but the potential for healing is affected by the severity of myocardial damage prior to VAD application.(ABSTRACT TRUNCATED AT 250 WORDS)

Ventricular assist systems for temporary life support: device readiness testing

A description is given of a quality control and reliability program for establishing short-term ventricular-assist-device (VAD) safety and efficiency prior to clinical use. Experience in the clinical use of temporary VADs indicates that the pre-clinical reliability testing program works, since no device related failures occurred. The procedures have become much stricter, and a goal of 80% reliability for in vitro testing currently exists for the permanent, ventricular-assist system with strict guidelines on how to determine device-related failure. Animal testing requires total animal-months of continued usage consistent with the 80% in vitro reliability. A critical feature of the program has been freezing of device and system design throughout the quality control/assurance program, reliability testing, and clinical use.

Long-Term Clinical Use of the Novacor Left Ventricular Assist Device as a Bridge to Transplantation

The Novacor left ventricular assist device (NLVAD) is an implantable, electrically powered, pulsatile circulatory assist device undergoing clinical investigation. This report reviews the 33-day bridge-to-transplant course of a patient presenting in cardiogenic shock after acute myocardial infarction who could not be weaned from cardiopulmonary bypass following emergency coronary artery revascularization. Cardiac output was satisfactory during the entire 33-day period: 4.2 ± 0.8 1/min (± SD) during the first week and 6.3 ± 0.9 thereafter. Haptoglobin remained low (30 ± 4 mg%), suggesting mild hemolysis, but plasma hemoglobin remained normal throughout and the patient required only 600 ml of blood after the first two postoperative days. Renal impairment (peak creatinine = 2.9 mg/dl on day three) was attributed to preoperative hypotension and resolved by day seven. The clinical course included pneumonia and hypoxic encephalopathy, both of which resolved. There were no thromboembolic complications or device-related infections. The patient underwent orthotopic cardiac transplantation on day 33. This case demonstrates the long term clinical efficacy and safety of the NLVAD in the setting of cardiogenic shock after massive myocardial infarction as a bridge-to-transplant support system.

Successful Use of a Paracorporeal Left Ventricular Assist Device in Man

A paracorporeal left ventricular assist device (LVAD) with a capacity to pump 8 L/min of blood was employed in a clinical trial, and this report details the first survivor. A 60-year-old man could not be separated from the pump oxygenator following coronary artery bypass grafting, and, therefore, an LVAD was employed. Almost the entire left ventricular workload was assumed by the mechanical pump so that the myocardium was allowed to rest and recover. The LVAD support was continued for 105 hours. It provided satisfactory total body perfusion with maintenance of good hemodynamics--without serious deleterious effects on hematologic factors. The patient is alive and active without cardiac symptoms 16 months after his operation. The total experience with 13 LVAD implantations warrants continuation of the clinical trials in selected patients.