Heterotopic prosthetic ventricles as a bridge to cardiac transplantation. A multicenter study in 29 patients

Control and Treatment of Hemostasis in Cardiovascular Surgery

The hemostasis protocol applied at the Cardiovascular Surgery Dept. of La Pitié Hospital has greatly reduced thromboembolic accidents and excessive bleeding, with consequent benefits for patients as well as cost reduction. Protocol also has been adopted for patients implanted with a circulatory assist device or a TAH. This paper presents our criteria on supervision and treatment of coagulation with such patients, who reflect all the acquired pathology in clinical hemostasis. From 04/86 to 07/94, 82 patients underwent TAH as a bridge to transplantation. Mean age: 38. Overall duration of mechanical support: 1930 days (mean: 23), of which 137 and 603 for 2 patients. Average duration of CPB: 150 min. Systematic approach to complex TAH-blood interaction and pre-operative multiple organ dysfunction used to control bleeding and/or thromboembolism after CPB. In addition to routine tests, specific regular testing was carried out at least once a day for platelet functions, for thrombin formation and its regulatory pathways, and for the fibrinolytic system. Patients were treated with small doses of Heparin, large doses of Dypyridamole, small doses of Aspirin, modulated doses of Aprotinin, Ticlopidine, Pentoxifylline, FFP, as well as Fibrinogen and AT III concentrates. Dosage was adapted to patient's clinical profile as well as to test interpretation criteria to provide personalized treatment. DIC, widely present in its different phases, was thus diagnosed and treated. All DIC bleeding was controlled, making it possible to detect other causes of post-operatory bleeding and use blood derivates rationally. There were no thromboembolic complications and no iatrogenic bleeding. TAH explantation shows no evidence of macroscopic clots in high risk sites, confirmed by microscopic analysis.

Review article : Mechanical ventricular support in the management of postcardiotomy cardiogenic shock

'For many reasons clinicians hesitate to employ mechanical devices of unproved efficacy except in the most critically ill patients and then only as a desperate measure. These approaches accounted for a substantial lag time between intra-aortic balloon pump availability and widespread utilization. Ventricular assist devices, recently approved for initial clinical trials, face the same dilemmas'. Norman, 1977.1

Rescue treatment by percutaneous closure of interatrial septal defect or PFO in infants with Berlin heart

During the past two decades, important progress has been achieved in the treatment of end-stage congestive heart failure in newborns and infants. The use of ventricular assist devices (VAD) in these patients is now available as a bridge to heart transplantation. The use of a VAD may reveal the presence of a silent interatrial septal defect or a patent foramen ovale (PFO), inducing a right to left shunt resulting in systemic desaturation and hemodynamic instability. We present two cases of low weight infants on circulatory support with VADs and right to left shunt through interatrial septum that were successfully treated by percutaneous intervention with an occlusion device.

Left ventricular apical infection and rupture complicating left ventricular assist device explantation in 2 women with postpartum cardiomyopathy

Postpartum cardiomyopathy is rare form of cardiac failure, with the potential for cardiac function to recover to normal. When medical therapy fails to control symptoms or haemodynamic stability, circulatory support with a ventricular assist device may be considered as a bridge to cardiac transplantation. We describe 2 patients with severe postpartum cardiomyopathy, in whom cardiac function recovered sufficiently during mechanical circulatory assistance to enable device explantation. Bacteremia during device support was treated with chronic suppressive antibiotics, yet after cannula explantation and ventricular repair, residual infection led to destruction of the primary repair, with formation of a left ventricular pseudoaneurysm. This is a complication of device support not previously reported. Surgery was necessary to repair the infected ventricular cannula site. Both patients recovered; however one patient developed recurrent cardiomyopathy 4 months later.

The future of mechanical circulatory support

Heart failure is one of the most important causes of morbidity and mortality in adults and the elderly. In the United States, an estimated 5 million persons already have heart failure, and more than 500,000 new cases are being diagnosed each year [ 1]. Today, cardiovascular physicians can choose from a wide range of mechanical circulatory systems, depending on the desired degree of support, length of support, extent of postoperative mobility and other factors. This article describes the growing problem of heart failure and the future prospects for patients with heart disease. It discusses current mechanical circulatory support devices and their changing applications, newer devices still in the experimental stages, and some hurdles to the use of mechanical circulatory support.

Prologue: ventricular assist devices and total artificial hearts. A historical perspective

In the 1960s, when LVADs and TAHs were introduced into clinical use, researchers estimated that, with this technology, the problem of heart failure could be solved within 20 years. Unfortunately, the evolution of these devices has taken much longer than anticipated. Nevertheless, significant advances have been achieved in both cardiac assistance and replacement, and today's cardiac surgeons have a wide range of devices from which to choose (Table 4). This progress has largely been due to the support of the NHLBI, especially the Devices and Technology Division headed by John Watson, and of the devoted commitment of the investigators. Because of the long-term commitment required for both basic and clinical research, commercial medical technology companies are unable to assume this burden. Advances in mechanical circulatory support and replacement have benefited numerous patients worldwide who would otherwise have died of heart failure, and devices now exist for use as bridges to recovery, bridges to transplant, and destination therapy. The current challenge is to refine what we have and to apply these technologies to broader patient populations with maximal safety and at a reasonable cost.

Cardiac infections in the immunosuppressed patient

This article presents the various manifestations of cardiac infections found in the immunosuppressed host. Emphasis is placed on the correlation between specific impairments of host defenses and the occurrence of certain types of pathogens. The effect of immunosuppression on the clinical manifestations of these infections is discussed. Finally, appropriate diagnostic modalities are presented for the major types of infections.

Clinically available extracorporeal assist devices

Mechanical circulatory support has been shown to be of benefit to allow recovery after conventional heart surgery and as a successful bridge to heart transplantation. Recent clinical trials with implantable left ventricular assist devices (LVADs) have been completed with these devices showing restoration of normal hemodynamics and successful bridge to transplantation. A major advantage of the implantable devices is the ability for the patient to be discharged and followed up at an outpatient setting. However, multiple advantages to extracorporeal devices still remain, which are the focus of this review. One advantage of the extracorporeal devices is that they can be placed in much smaller patients than currently available implantable LVADs. Also, because of differences in design of the assist devices, the extracorporeal devices can be placed without the need for the cardiopulmonary bypass and with decreased operative time and dissection. Perhaps the biggest advantage of the extracorporeal devices is that they can provide a support for both the right and left side of the heart as opposed to the implantable LVADs, which are only used as left ventricular assist devices. This article describes in detail the advantages and disadvantages of the extracorporeal devices as well as the operative techniques used to implant them. As the number of patients with heart failure continues to rise, so will the need for mechanical circulatory support. Though the majority of these patients will be served by a long-term implantable device, there will remain a subset of patients that will be best suited for treatment with extracorporeal devices.

Clinical experience with 111 thoratec ventricular assist devices

BACKGROUND

Ventricular assist devices (VADs) have gained wider acceptance due to refinements in patient selection and management and device availability.

METHODS

To evaluate early and late results, we reviewed our first 111 patients with the Thoratec VAD.

RESULTS

Forty-four patients were supported for myocardial recovery. The mean age in the recovery group was 51.9 years. There were 18 left VADs (LVADs), 17 biventricular VADs (BVADs), and nine right VADs (RVADs). Complications included bleeding in 20 patients (45%) and device-related infection in 1 patient (2%). Nineteen were weaned from the VAD, with 12 survivors. Sixty-seven patients were supported as a bridge to cardiac transplantation. The mean age was 41.5 years. There were 39 LVADs and 28 BVADs. Complications included bleeding in 21 patients (31%) and device-related infection in 12 (18%). Three patients were weaned and 39 patients were transplanted from the assist device, for a total of 42 bridge survivors. Device-related thromboembolism occurred in 9 patients (8.1%), 7 of whom were bridge to transplantation. The duration of VAD support ranged from 0.1 to 27 days (mean 4.5 days) in the recovery group and 0.2 to 184 days (mean 40.7 days) in the bridge to transplantation group. The 10-year actuarial survival was 16% for the recovery group, 22%, for the bridge group, and 33% for transplanted patients.

CONCLUSIONS

Despite advances, VAD support remains associated with significant morbidity and operative mortality.

Surgical therapy for dilated cardiomyopathy

As the next millennium approaches, excitement and promise characterize the future of dilated cardiomyopathy. Until recently, dilated cardiomyopathy was considered an incurable, uniformly fatal chronic disease. Epidemiologic studies have demonstrated that at least a quarter of patients with recent onset of symptoms with cardiomyopathy manifest spontaneous improvement and a sustained favorable prognosis. It is imperative that patients who present with new-onset cardiomyopathy be managed medically and closely followed. Medical treatment remains the foundation of therapy, and certainly the advent of beta-blocker use may herald further benefit beyond that observed with conventional therapy (ACE inhibitors and digoxin). Unless mechanical support is required for hemodynamic instability and end organ failure, patients should be treated medically and observed. As discussed earlier, transient mechanical support as a bridge to recovery should be considered in the appropriate clinical scenario before committing to cardiac transplantation. Patients with established disease who have been followed for extended periods (> 6 months) that have progressive symptoms despite optimal medical therapy should be considered for surgical therapies. Cardiac transplantation is available to only a minority of the diseased population. All newer modalities of surgical unloading therapy theoretically reduce wall stress. Clearly in dilated cardiomyopathy, ventricular performance is reduced; however, individual myocyte contractile function may be intact. Studies of isolated myocytes (which are unloaded) have yielded conflicting data; however, if contractile function is intact and performance is reduced primarily secondary to abnormal loading conditions, surgical unloading therapies should yield benefit. Hence the thesis of Batista that geometric alteration will improve performance assumes intrinsic integrity of the myocyte contractile function. The implication of intrinsic myocyte contractile dysfunction is that surgical remodeling does not yield improved ventricular performance. Although clinicians have learned that selection criteria appear to play a role in predicting beneficial outcomes with cardiomyoplasty and the Batista procedure, clinical techniques to assess the integrity of myocyte function are unsophisticated. Quantifying interstitial fibrosis, assays for the degree of apoptosis, and various immunologic measures currently do not provide the insight necessary to predict outcomes reliably. The future assessment of dilated cardiomyopathy and the decision to consider alternative surgical procedures versus cardiac transplantation will likely be determined by biomolecular studies. At present, these new surgical procedures are promising therapies and potential alternatives to cardiac transplantation. Controlled studies to determine the clinical and survival benefit compared with medical therapy will ultimately be required, after the surgical techniques and patient selection criteria are refined. Randomized, prospective controlled studies assessing LVAD therapy and cardiomyoplasty are in progress.

Neurologic complications of vascular surgery

Technological advances in the management of cardiovascular disorders have resulted in an expansion of eligibility criteria for treatment, as well as an increased demand for improved outcomes. Neurologic complications after coronary artery bypass surgery, particularly stroke and cognitive dysfunction, substantially increase mortality, strain health care resources, and reduce the clinical effectiveness of the procedure. Carotid endarterectomy can be both the optimum stroke preventative strategy as well as a cause of stroke. The trend toward minimally invasive endovascular procedures, which has provided non-surgical options for both coronary and cerebral vascular occlusive lesions, is slowly being compared to conventional surgical and medical therapies. The identification of risk factors and mechanisms of adverse cerebral outcomes of these myriad vascular procedures is essential in improving their clinical effectiveness and patient applicability.

Infections After Organ Transplantation

Over the last ten to fifteen years medical and surgical advances have led to lower rates of infection and infection-related mortality in transplant recipients. Despite these advances, the process whereby one diagnoses and manages infectious problems in transplant patients has become increasingly complex. Evaluation of transplant patients with infections requires a good understanding of the intricacies of modern immunosuppressive therapy and both the typical and atypical clinical manifestations of many conventional and opportunistic pathogens. In particular, it is incumbent upon the clinicians caring for transplant patients to be familiar with the biology of cytomegalovirus and other herpes viruses, and of the prophylactic strategies that have evolved to lessen the burden of disease from these agents. Thorough knowledge is also required of common fungal pathogens and the viruses that cause chronic hepatitis. Transplant patients also should always be evaluated in the temporal context of their transplant operation, because different diseases are prevalent at different times after transplantation. Since immunosuppressive drugs modify the clinical presentation of infections is important to maintain clinical vigilance and attend to even minor new symptoms. This chapter is designed to provide a relatively concise overview of transplant infections for intensivists or other clinicians who encounter transplant patients in their practice. The references encompass much of the classic transplant infectious disease literature; they are included, not only for citation, but as a bibliography for further study.

The continuing evolution of mechanical ventricular assistance

A great number of patients suffer and die of the sequelae of acute and chronic heart failure each year. Although advances in medical and surgical therapy have benefited many of these patients, most have disease that is refractory to any definitive therapy. For these patients cardiac transplantation is the only remaining hope. Unfortunately, because of the increasing demand for donor organs in the face of a fixed and limited supply, this option is available to only a small percentage of these patients. Even in patients accepted for transplantation, a significant waiting list mortality has been observed. A variety of VADs have been developed since the first successful case of mechanical cardiac assistance more than 30 years ago. These devices differ in basic mechanical function, method of insertion, and degree of implantability and thus have different indications and potential applications. Whereas the intraaortic balloon pump and centrifugal pumps are effective short-term support modalities, extracorporeal and implantable pulsatile devices have been used successfully for long-term support of patients with reversible and nonreversible cardiac failure. Although these pumps have most commonly been used as bridges to transplantation, increasing clinical experience has supported the notion of long-term mechanical assistance as a definitive therapy for patients with end-stage heart disease. Although complications, particularly infection and thromboembolism, pose significant challenges and long-term device reliability remains to be fully determined, available implantable devices appear to be capable of providing effective long-term support. As data are obtained from currently ongoing trials comparing VAD support with medical therapy for end-stage heart failure, ethical and economic issues will assume increasing importance.

Reducing neurological complications after cardiac transplantation: technical considerations

As the survival rate for cardiac transplantation improves, attention focuses on morbid events that occur perioperatively. Neurological problems have been recognized after transplantation, and appear to have multiple etiologies including thromboembolism, hypoperfusion syndromes, cerebral hemorrhage, and drug toxicities. Since 1988, 113 consecutive adults with end-stage cardiomyopathy were transplanted using a surgical technique that emphasizes precise everting atrial and great vessel anastomoses, a modified order of anastomoses, continuous endocardial and topical cold irrigation, and careful de-airing of the heart. Although a significant fraction of the patients were at high risk for cerebral events, the incidence of early and late neurological complications were each under 2%. The rate of early graft dysfunction was low and no patient was found to develop intracardiac thrombus on intermediate-term follow-up. These technical modifications may contribute to improved neurological outcomes after transplantation.

A reliable bridge to cardiac transplantation: the TCI left ventricular assist device

The Thermo Cardiosystems (TCI) HeartMate, a pneumatically driven, implantable left ventricular assist device, was designed for long-term support of the failing heart. Between February 1990 and August 1992, the HeartMate was implanted in 11 heart transplant candidates because of profound deterioration of left ventricular function. Patients had a mean cardiac index of 1.6 L.min-1 x m-2 and a mean pulmonary capillary wedge pressure of 33 mm Hg despite maximal pharmacologic support with at least three inotropic medications. In addition, 5 patients were being supported with an intraaortic balloon pump. Nine patients were bridged successfully to cardiac transplantation. The mean cardiac index after implantation of the left ventricular assist device was 3.2 L.min-1 x m-2. Support ranged from 2 to 143 days (mean duration, 60 days). One patient died early of low output secondary to right heart failure, and a second died of air embolism, which occurred intraoperatively. All surviving patients became fully ambulatory. There were no thromboembolic complications during a total of 658 patient-days of support on a regimen of only 80 mg of aspirin daily. The 9 bridged patients are currently alive 4 to 34 months after transplantation. The TCI HeartMate provides safe and effective hemodynamic support with low risk of complications and virtual freedom from thromboembolism on a regimen of minimal anticoagulation.

Univentricular and biventricular Thoratec VAD support as a bridge to transplantation

As of October 1991, the Thoratec ventricular assist device (VAD) system has been used in 154 transplant candidates who were in imminent risk of dying before donor heart procurement at 39 medical centers in 10 countries. The VAD system consists of a prosthetic ventricle with a 65-mL pumping chamber made from Thoratec's BPS-215M polyurethane, cannulas for atrial or ventricular inflow and arterial outflow connections, and a pneumatic drive console. The devices can be used for partial or complete support of the pulmonary, systemic, or both circulations. In all patients (average age, 42 years; range, 11 to 64 years), the pumps were placed in a paracorporeal position on the anterior abdominal wall and connected to the heart and great vessels by cannulas crossing the chest wall. Biventricular support was used in 120 patients (78%) and isolated left VADs were used in 34. Average flow rate was 5.0 +/- 0.9 L/min for the left VAD and 4.3 +/- 0.8 L/min for the right VAD. The most frequent complications were bleeding (42% incidence, 7% mortality) and infection (36% incidence, 8% mortality). Ninety-eight patients (65%) recovered sufficiently to undergo heart transplantation after 8 hours to 226 days of support (average, 17.5 days), and 3 are waiting on VADs for transplantation. Eighty-two patients who received transplants have been discharged. This is an 84% early post-transplantation survival and a 54% overall survival. The actuarial survival 1 year after transplantation is 82%, comparable with that of conventional heart transplantation.(ABSTRACT TRUNCATED AT 250 WORDS)

Use of the Symbion biventricular assist device in bridging to transplantation

From 1988 to 1991 13 patients received Symbion biventricular assist devices in attempts to bridge them to cardiac transplantation. All 7 of those who had cardiac transplants survived to hospital discharge. One death occurred 60 days after transplantation because of rejection. All other patients who received transplants are surviving. Implant times in this group varied from 10 to 164 days (mean, 55 days). There were two embolic neurologic events and two significant infections, and 2 of the survivors were dialyzed for reversible renal failure before transplantation. Of those who died on device support, 3 presented on centrifugal pump support. The three other deaths were caused by graft rejection, multiple organ failure, and multiple peripheral emboli. Biventricular assist devices optimally provide cardiac outputs of 4 to 5 L/min, can be quickly inserted often without requiring cardiopulmonary bypass, are easily explanted, and seem best suited for patients weighing less than 80 kg.

Improved multiorgan function after prolonged univentricular support

Eleven cardiac transplant candidates (all male; mean age, 43.3 years) with multiorgan (hepatic, pulmonary, and/or renal) dysfunction were sustained for prolonged periods (> 30 days) with the HeartMate (Thermo Cardiosystems, Inc, Woburn, MA) left ventricular assist device. We evaluated the effect of extended support on end-organ recovery and on the ultimate outcome of cardiac transplantation. In addition to cardiac failure, 9 patients had hepatic dysfunction, 8 had pulmonary dysfunction, and 6 had renal dysfunction (4 of whom required hemodialysis before left ventricular assist device support). Mean duration of support was 115 days (range, 31 to 233 days). All patients underwent successful transplantation; 10 of these patients survived a mean of 24 months. One patient, who had required hemodialysis and ventilatory support during and after support, experienced progressive multiorgan failure and died 7 weeks after transplantation. Two late deaths after transplantation were unrelated to the device. Overall, patients experienced improvement in cardiac functional class status, and most participated in cardiac rehabilitation programs before transplantation. During left ventricular assist device support, hepatic function returned to normal in 8 patients, pulmonary function recovered in 7, and renal function returned to normal in 4. One patient who required hemodialysis underwent renal transplantation after cardiac transplantation and had complete recovery of renal function. In the current era of donor shortages, gravely ill patients can benefit from a strategy of prolonged left ventricular assist device support. This strategy has proved safe, has allowed for reversal of multiorgan dysfunction, and has produced healthier transplant candidates.

Isolated ventricular systolic interaction during transient reductions in left ventricular pressure

The volume and pressure of one ventricle have been demonstrated to modulate the volume and pressure in the contralateral chamber during systole and diastole. To quantitate the isolated systolic effects of left ventricular (LV) pressure on right ventricular (RV) mechanics, we rapidly withdrew blood from the LV immediately after diastole via an apex cannula during a single cardiac cycle in eight open-chest, open-pericardium anesthetized pigs (45 kg) and studied the effects on the RV. Reductions in LV pressure of up to 75 mm Hg were achieved in midsystolic without changing LV or RV diastolic volume or pressure. Resultant changes in RV flow and pressure development during these single unloaded beats may therefore be considered to result from pure systolic interaction. The instantaneous left-to-right systolic pressure gain [G(t)] was determined as the ratio of RV pressure change to LV pressure change as a function of time during systole, and the mean LV-to-RV systolic pressure gain was determined as the ratio of changes in mean systolic RV pressure to changes in mean systolic LV pressure. During LV unloading, there was an average reduction of 62.6 +/- 12.3% in the mean systolic LV pressure, which resulted in decreases of 13.6 +/- 6.4% in mean RV systolic pressure, 17.9 +/- 10.4% in RV stroke volume, and 27.0 +/- 11.3% in RV stroke work. G(t) was found to vary significantly within systole, reaching a minimum of 0.042 +/- 0.014 mm Hg/mm Hg at normalized time 0.70 of the systolic duration and a maximum of 0.079 +/- 0.029 at the end of RV ejection.(ABSTRACT TRUNCATED AT 250 WORDS)

Techniques for optimization of pulsatile ventricular assist device support

For some time now researchers have argued the efficacy of pulsatile versus nonpulsatile hemodynamic support. Pulsatile systems, while providing a more physiological pumping source, are burdened with a multiparametric output function that can greatly affect the utility of such ventricular assist device (VAD) support. A simplified approach to the optimization of the pulsatile VADs' output function has been developed. This approach yields device outputs of approximately 5.5 L/min at physiologic pressures while demonstrating clinically acceptable blood chemistry. Obtaining this optimal operating point involves the determination of the VAD system output function for a range of fill-enhancing vacuum settings. A quantitative method for evaluating synchronous versus asynchronous pumping modes as related to coronary perfusion is also demonstrated.

Cardiogenic shock complicating acute myocardial infarction: the use of coronary angioplasty and the integration of the new support devices into patient management

Conventional therapy for cardiogenic shock complicating acute myocardial infarction continues to be associated with a high in-hospital mortality rate. Hemodynamic support with new mechanical devices and emergency coronary revascularization may alter the long-term prognosis for patients with this complication. Between July 1985 and March 1990, 68 patients presented to the University of Michigan with acute myocardial infarction and cardiogenic shock. Interventions performed included thrombolytic therapy (46%), intraaortic balloon pump counterpulsation (70%), cardiac catheterization (86%), coronary angioplasty (73%), emergency coronary artery bypass grafting/ventricular septal defect repair (15%), Hemopump insertion (11%), percutaneous cardiopulmonary support (4%) and ventricular assist device (3%). The 30-day survival rate was significantly better in patients who had successful angioplasty of the infarct-related artery than in patients with failed angioplasty (61% vs. 7%, p = 0.002) or no attempt at angioplasty (61% vs. 14%, p = 0.003). This difference was maintained over the 1-year follow-up period. The only clinical variable that predicted survival was age less than 65 years. The early use of the new support devices in 10 patients was associated with death in 8 (80%), but this poor outcome may reflect a selection bias for an especially high risk population. Collectively, these recent data continue to suggest that emergency revascularization with angioplasty may reduce the mortality rate, but further study is required to define optimal utilization and integration of new support devices.

Surgical complications in bridging to transplantation: the Thermo Cardiosystems LVAD

Left ventricular assistance with a number of different devices has been used to successfully bridge patients to cardiac transplantation. Surgical complications or complications related to the device itself, however, may preclude transplantation or lead to death. We report our recent experience with the Thermo Cardiosystems model 14 "HeartMate" left ventricular assist device in 3 patients. The device was implanted for 15 to 95 days. Complications included mediastinitis and peritonitis associated with the device in place before transplantation, and colonic perforation, and a late diaphragmatic hernia after transplantation. Despite these and other minor complications, all 3 patients underwent successful cardiac transplantation. Mechanical support for the right ventricle was not necessary. The Thermo Cardiosystems left ventricular assist device provided excellent support in a range of physiological conditions with no mechanical malfunction despite the surgical complications.

Biventricular bypass: alternative to univentricular bypass and total artificial heart-bridge

Left ventricular and biventricular bypasses (LVBs, BVBs) were performed in 102 experiments in sheep, goats, and donkeys. Biventricular bypass was performed in the assisted circulation mode or in the paracorporeal artificial heart bridge (PCAHB) mode when the natural heart fibrillates. During implantation of artificial ventricles instead of a heart-lung bypass, counterpulsation was used. Several types of connective conduits were developed and tested in experiments. The conduits included bifurcational connective pipes that permit "intake" of blood into artificial ventricles from atria and ventricles of the natural heart simultaneously and consequently provide effective blood flow through shunts not depending on the state of the natural heart (acute cardiac weakness or asystole). Monitoring gas content (PO2, PCO2, and pH) in the myocardium of both ventricles suggested development of right ventricular failure under conditions of LVB before hemodynamic changes occurred and confirmed the preferability of BVB over other methods of assisted circulation, as it is most effective and capable of normalizing short-term cardiac disturbances in the course of the 1st 2 days. Survival time of experimental animals (2-3 days for dogs, 5-12 days for sheep, goats, and donkeys) is sufficient to overcome acute cardiac insufficiency. This suggests that BVB in the assisted circulation mode or PCAHB mode can serve as a bridge for cardiac transplantation for the time of search for the available organ.

Extracorporeal mechanical pulsatile pump and its significance for myocardial function recovery and circulatory support

The authors performed 12 acute (on dogs) and 12 chronic (on calves) assisted circulation experiments with the use of the total extracorporeal mechanical pump (TEMP) artificial ventricles. The functional morphological research of the myocardium suggests that in addition to the possibility of the biological heart function full replacement, the artificial ventricle also helps recover damages in both the myocardial infarction and distal zones. The critical time period up to the onset of artificial circulation is not more than 2 h, and after that myocardial changes are irreversible.

Evolving experience with mechanical circulatory support

Since 1985 total mechanical circulatory support for mortally ill transplant candidates has been progressively integrated into the authors' program. During this period 379 patients underwent transplantation. Of this group of patients, 62 required some form of mechanical support other than the intra-aortic balloon pump. Because intra-aortic balloon pump assist was limited in therapeutic effect and was associated with patient immobility and line-related sepsis, the next logical step toward support was the artificial heart. Of 20 patients implanted with the Jarvik heart, 17 underwent transplantation, but only 9 of these survived to discharge. In 1988, the authors abandoned the preferential use of the total artificial heart because of excessive cumulative probability of death from wound infection. They began to use the Novacor electrical assist device with the percutaneous power cord because they believed that univentricular support would be adequate for most patients, because its heterotopic position would reduce the likelihood of infection, and because it had the potential for chronic implantation. Twenty-three patients with biventricular failure (right ventricular ejection fraction less than 20%, 18/23) received the electrical assist device for an average of 50.4 days (range 1-193 days). All 17 transplanted patients survived until discharge. Only one of the five deaths that occurred after implantation, but without transplantation, was due to infection (candidiasis). Remarkably, all patients who survived the perioperative period ultimately survived with univentricular support alone. Based on this experience, survival of mechanically supported patients is now comparable to that of those less mortally ill.

Directions in cardiac assistance

The use of mechanical circulatory support devices came to prominence with the use of the Jarvik 7 total artificial heart, both as a permanent implant and as a bridge to transplantation. Over the past decade, however, interest in the use of left ventricular assist devices has overshadowed that of the total artificial heart and great strides have been made, both in the use of such devices as temporary support, and towards the ultimate goal of permanent implantation. A variety of devices are available to support either or both ventricles with a great range of complexity and expense. This test discusses the use of ventricular assist devices and briefly describes the options available. The era is rapidly approaching when the use of implantable circulatory support devices will become commonplace and may outpace, and possibly outperform, the results currently obtained with cardiac transplantation.