Mechanical circulatory support: the Bad Oeynhausen experience

Mechanical Circulatory Support after Orthotopic Heart Transplantation

Frequently the only therapy for primary graft- and right heart failure, as well as low output syndrome from acute of chronic rejection, is implantation of a mechanical circulatory support system, until recompensation or retransplantation. At our institution, mechanical assist devices were implanted in 25 heart recipients for a cute rejection (n=9), primary graft failure (n=7), acute right heart failure (n=7), and chronic rejection with low output syndrome (n=2).

Patients (pts) with primary graft failure (n=3) received an intraaortic balloon pump (IABP), one pt an IABP plus Abiomed®-System for left ventricular support, one pt the Thoratec®-System for biventricular support. Patients with right heart failure (RHF) received the Biomedicus® centrifugal pump for right ventricular support. Nine pts suffered from acute rejection. Six pts received an IABP, one the Biomedicus® as femoro-femoral bypass, one the Abiomed®-System for biventricular support, two the Thoratec®-System for biventricular support and two within this group switched from the Biomedicus® pump to the Thoratec®-System for biventricular support. Patients with chronic graft failure (n=2) received the Novacor®-System (LVAD) for left ventricular support, one received a Tojobo®-System and an oxygenator for biventricular support post coronary artery bypass surgery.

Support time ranged from 0.5-h to 73 days. Five pts were weaned. Two (8%) of 25 pts were retransplanted, 18 (72%) died in spite of mechanical support from multiple organ failure. The use of a mechanical assist device after heart transplantation is encouraging only in the case of early right heart failure, as well as primary and chronic graft failure. In view of the poor results, the use of mechanical assist devices should not be recommended in the case of heart failure caused by acute rejection.

Primary Graft Failure after Heart Transplantation. Successful Recovery with Pneumatic Biventricular Assistance

A 41-year-old male underwent orthotopic heart transplantation complicated by intraoperative acute allograft failure. The patient required immediate placement of a pneumatic biventricular assist device which was kept for 49 days until graft recovery resulted in successful explantation of the device. The patient was discharged from hospital on postoperative day 112. Management of primary cardiac allograft failure with mechanical ventricular assistance is discussed

A Pivot Bearing-Supported Centrifugal Pump for a Long-Term Assist Heart

A pivot bearing-supported centrifugal blood pump has been developed. It is a compact, cost effective, and anti-thrombogenic pump with anatomical compatibility. A preliminary evaluation of five paracorporeal left ventricular assist studies were performed on pre-conditioned bovine (70-100 kg), without cardiopulmonary bypass and aortic cross-clamping. The inflow cannula was inserted into the left ventricle (LV) through the apex and the outflow cannula affixed with a Dacron vascular graft was anastomosed to the descending aorta. All pumps demonstrated trouble free performance over a two-week screening period. Among these five studies, three implantations were subjected for one month system validation studies. All the devices were trouble free for longer than 1 month. (35, 34, and 31 days). After achieving one month studies, all experiments were terminated. There was no evidence of device induced thrombus formation inside the pump. The plasma free hemoglobin levels were within normal ranges throughout all experiments. As a consequence of these studies, a mass production model C1E3 of this pump was fabricated as a short-term assist pump. This pump has a Normalized Index of Hemolysis of 0.0007 mg/100L and the estimated wear life of the impeller bearings is longer than 8 years. The C1E3 will meet the clinical requirements as a cardiopulmonary bypass pump. For the next step, a miniaturized pivot bearing centrifugal blood pump PI-601 has been developed for use as a permanently implantable device after design optimization. The evolution from C1E3 to the PI-601 converts this pivot bearing centrifugal pump as a totally implantable centrifugal pump. A pivot bearing centrifugal pump will become an ideal assist pump for the patients with failing heart.

Percutaneous ventricular assist devices: new deus ex machina?

The development of ventricular assist devices has broadened the means with which one can treat acute heart failure. Percutaneous ventricular assist devices (pVAD) have risen from recent technological advances. They are smaller, easier, and faster to implant, all important qualities in the setting of acute heart failure. The present paper briefly describes the functioning and assets of the most common devices used today. It gives an overview of the current evidence and indications for left ventricular assist device use in cardiogenic shock and high-risk percutaneous coronary intervention. Finally, extracorporeal life support devices are dealt with in the setting of hemodynamic support.

Novel biomarkers in human terminal heart failure and under mechanical circulatory support

This review summarizes recent findings on novel biochemical plasma biomarkers in terminal heart failure patients, which might predict an advanced mortality risk or even recovery. Moreover, we discussed the regulation of these heart failure-related biomarkers under mechanical circulatory support.

Percutaneous left ventricular assist devices during cardiogenic shock and high-risk percutaneous coronary interventions

Left ventricular assist devices were developed to support the function of a failing left ventricle. Owing to recent technological improvements, ventricular assist devices can be placed by percutaneous implantation techniques, which offer the advantage of fast implantation in the setting of acute left ventricular failure. This article reviews the growing evidence supporting the clinical use of left ventricular assist devices. Specifically, we discuss the use of left ventricular assist devices in patients with cardiogenic shock, in patients with acute ST-elevation myocardial infarction without shock, and during high-risk percutaneous coronary interventions.

Similar transplantation outcomes in patients bridged with cardiac assist devices for acute cardiogenic shock versus chronic heart failure

BACKGROUND

Heart failure (HF) patients may require cardiac assist device implantation prior to transplantation (Tx) because of either acute cardiogenic shock (ACS), with no prior history of HF, or for progression of pump failure in the setting of chronic HF.

AIMS

To investigate whether patients implanted with a cardiac assist device for ACS, have similar post-Tx outcomes as those who underwent cardiac assist device implantation because of progressive chronic HF.

METHODS AND RESULTS

We compared post-Tx outcomes of consecutive patients bridged due to ACS (Acute Group) with the outcomes of patients bridged due to deterioration of chronic HF (Chronic Group). Seventy-three patients had a cardiac assist device implanted and underwent subsequent cardiac Tx. Thirty-five patients (48%) had a cardiac assist device implanted due to ACS, most often caused by massive acute myocardial infarction, and 38 patients (52%) because of progressive chronic HF. Despite greater compromise at the time of implantation, the Acute Group recovered satisfactorily and underwent Tx with similar post-Tx survival rates as the Chronic Group patients [1-year survival: 88.6% vs 86.8%, p=0.80, actuarial survival (mean follow-up 4.2 years): 80.0% vs 81.6%, p=0.86)]. Furthermore, no significant differences were observed between the 2 groups in various post-Tx events.

CONCLUSION

Patients with ACS who underwent emergency cardiac assist device implantation as bridge to Tx had similar post-Tx outcomes as their more chronically ill counterparts who underwent device implantation on a non-urgent basis.

Implantation of Cardio West Total Artificial Heart for Irreversible Acute Myocardial Infarction Shock

Patients who develop cardiogenic shock after acute myocardial infarction have a very high mortality rate despite early reperfusion therapy. Hemodynamic stabilization can often only be achieved by implanting a mechanical circulatory support system. When, in cases representing expansive myocardial impairment without any chance of recovery, pharmacological therapy and the use of percutaneous assist devices have failed, the implantation of a total artificial heart is indicated. We report our first experiences with this extensive and innovative method of managing irreversible cardiogenic shock patients. The CardioWest total artificial heart was implanted in 5 patients (male; mean age, 50 years). All patients were in irreversible cardiogenic shock despite maximum dosages of catecholamines, an intra-aortic balloon pump and/or a femoro-femoral bypass. In all patients early reperfusion therapy was performed. After implantation of the Cardio West system, all dysfunctional organ systems rapidly recovered in all patients. Four of 5 patients underwent successful heart transplantation after a mean support time of 156 days. One patient died because of enterocolic necroses caused by an embolic event after termination of dicumarol therapy. In summary, our first experiences justify this extensive management in young patients who would otherwise have died within a few hours.

Results of a multicenter clinical trial with the Thoratec Implantable Ventricular Assist Device⁎⁎Thoratec Corporation, Pleasanton, Calif

OBJECTIVE

The Thoratec Implantable Ventricular Assist Device (Thoratec Corporation, Pleasanton, Calif) can be used for univentricular or biventricular support in patients with a body surface area as low as 1.3 m(2). Results of the multicenter clinical trial are reviewed.

METHODS

Between October 2001 and June 2004, a total of 39 patients at 12 institutions were supported with the Thoratec Implantable Ventricular Assist Device. Twenty-four patients (62%) received left ventricular assist devices and 15 (38%) received biventricular assist devices. Indications included bridge to transplantation (n = 30) and postcardiotomy failure (n = 9). The control group included 100 patients from the Food and Drug Administration approval submissions for the paracorporeal version of the ventricular assist device.

RESULTS

Twenty-eight male and 11 female patients, with mean age of 48 years (16-71 years) and body surface area of 1.9 m(2) (1.3-2.4 m2) were supported for 3938 patient-days (10.8 patient-years). Mean left ventricular assist device flow index on the first postoperative day was 2.5 +/- 0.5 L/(min x m2). Mean duration of support was 101 days (9-597 days). Eighteen patients were discharged after a mean duration of 96 days. There were no ventricular assist device failures. Complications included 13 cases of bleeding requiring reexploration (33.3%), 1 embolic and 2 hemorrhagic strokes (7.7%), 5 driveline infections (12.8%), and 2 pocket infections (5%). Support to successful outcomes was 70% for bridge to transplantation and 67% for postcardiotomy recovery, versus historical results for the paracorporeal ventricular assist device of 69% for bridge to transplantation and 48% for postcardiotomy recovery.

CONCLUSION

The Thoratec Implantable Ventricular Assist Device is a new implantable pulsatile ventricular assist device that allows hospital discharge for patients as a bridge to transplantation or for postcardiotomy failure. It is the first Food and Drug Administration-approved implantable ventricular assist device with biventricular capability.

Prediction of cardiac function after weaning from ventricular assist devices

OBJECTIVE

We analyzed the factors influencing the cardiac function of patients after weaning from ventricular assist devices and established a prognostic index.

METHOD

A multivariate analysis was performed using the Cox proportional hazards model of the clinical parameters of 28 patients with end-stage heart failure before implantation of a ventricular assist device and directly before weaning from the device.

RESULTS

After weaning from the ventricular assist devices, 14 of the 28 investigated patients showed stable cardiac function, and 12 had recurrent heart failure, but only 1 of them died before transplantation or implantation of another ventricular assist device, and 2 patients died of causes unrelated to heart failure. In addition to left ventricular ejection fraction, the duration of symptomatic heart failure and left ventricular intracavitary dimensions in diastole measured before ventricular assist devices weaning were the major factors influencing cardiac function after weaning. In the group of patients with heart failure duration less than 3 years, only 2 of 13 cases were recurrent, but in the group with heart failure duration more than 3 years, 10 of 15 cases were recurrent. In 10 patients with 40 to 50 mm left ventricular intracavitary dimensions in diastole before weaning, only 1 case was recurrent. In 10 patients with 51 to 55 mm left ventricular intracavitary dimensions in diastole, 3 cases were recurrent. In the group with left ventricular intracavitary dimensions in diastole more than 56 mm, all 8 cases were recurrent. A prognostic index was calculated using the following formula: prognostic index = -10.10 + 0.208 (heart failure duration in years) + 0.173 (pre-explantation left ventricular intracavitary dimensions in diastole in millimeters). In the group with a prognostic index less than 0, only 2 of 16 cases were recurrent, and the rate of stable cardiac function in the 51st month after weaning was 83.6%. In the group with a prognostic index greater than 0, 10 of 12 cases were recurrent, and the rate of stable function in the 57th month was 0.0%.

CONCLUSION

In patients with off-pump left ventricular ejection fraction greater than 40%, the duration of symptomatic heart failure and the left ventricular intracavitary dimensions in diastole measured before weaning yield a useful index to predict long-term cardiac function after weaning from ventricular assist devices.

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.

Recovery of organ dysfunction during bridging to heart transplantation in children and adolescents

The beneficial effects of ventricular assist devices on organ dysfunction during bridging to heart transplantation have been widely reported in the adult population. In contrast, the use of ventricular assist devices used as bridge-to-transplant in children is limited. To evaluate organ recovery during ventricular support in pediatric transplant candidate, respiratory, renal and hepatic function were reviewed retrospectively. The Thoratec device (stroke volume 65 ml) and the HIA-Medos-system (stroke volume 25/10 ml) were used as bridge-to transplant in 11 children and adolescents who were in low-output-syndrome despite maximal pharmacological support. Prior to implantation five patients were mechanically ventilated, six patients underwent cardiopulmonary resuscitation, eight patients had anuria (one treated by hemofiltration), three patients had liver dysfunction and four patients had signs of severe infection. At the time of implantation one patient was supported by the intraaortic balloon pump and one by the femorofemoral bypass for rapid hemodynamic stabilization. Eight patients were treated using the Thoratec device (one of these by Nova cor on the left side), three by the HIA-Medos system. The support time ranged between seven and 140 days. Seven patients could be extubated within three days. Renal function recovered in all pts. Liver enzymes decreased in all pts without reaching normal values. Bilirubin values also decreased in survivors but increased to 9.3 mg/dL in non-survivors. At least seven patients underwent successful heart transplantation, three patients died because of multiorgan failure after extended transfusion and one patient because of technical failure. In our experience the hemodynamic situation was sufficient in all bridging to transplant candidates. In all patients who underwent successful transplantation, transplantability was associated with rapid organ recovery within seven days after initiating mechanical assistance. Extended blood tranfusions, combined failure of three organs and increasing bilirubin values during support seem to be predictors of poor outcome.

Left ventricular assist devices as bridge to heart transplantation: The Niguarda Experience

BACKGROUND

Congestive heart failure is the leading cause of death in Western countries. Heart transplantation currently is the only accepted therapy for patients with end-stage heart failure, but the supply of donor hearts is inadequate, and different mechanical circulatory support systems have been investigated as bridges to heart transplant.

METHODS

Since April 1992, 53 patients (47 men, 6 women, aged 12 to 61 years) received left ventricle mechanical circulatory support as bridge to heart transplant. The two principal devices used were: the Novacor LVAS in 31 patients and the DeBakey VAD in 11 patients.

RESULTS

All patients survived the operation. Mean duration of LVAD support was 2.8 +/- 5.6 months. Thirty-seven patients (71.1%) underwent heart transplantation. Twelve major bleeding episodes occurred in nine patients (16.9%). Globally, major and minor neurologic events occurred in 13 patients (24.5%). Ten patients (19.9%) assisted with the Novacor Wearable LVAS device were discharged at home while waiting for heart transplant (HTx). The mean follow-up of the 34 discharged transplanted patients was 45.3 +/- 37 months. Actuarial survival of transplanted patients while on LVAD was 91.0 +/- 4.9% and 83.4 +/- 8.5% at 1 and 5 years, respectively. No differences in post-transplant long-term survival and rejection and allograft vasculopathy occurred between patients transplanted with or without LVAD implanted.

CONCLUSIONS

LVAD therapy proved to be effective in bridging patients with end-stage heart failure to HTx. While on LVAD support, patients assisted with implantable wearable devices could be discharged at home, ameliorating their quality of life. The excellent survival rate after HTx is concomitant with a low incidence of rejection and cardiac allograft vasculopathy.

Long-term implantable left ventricular assist devices: out-of-hospital program

The assist devices demonstrate the safety and reliability of these systems in the management of end-stage cardiac failure, not only in an in-hospital setting, but also in the cohort of OOH patients. The OOH option has led to a significant improvement in the quality of life of those patients. However, VADs are still associated with a considerable number of complications. The newly introduced fully implantable system (LionHeart) has reduced significantly the system-related infection complications. Further miniaturization of the systems might reduce the comorbidities and increase the acceptance of this therapeutic option in the management of end-stage cardiac failure.

The time course of natriuretic hormones as plasma markers of myocardial recovery in heart transplant candidates during ventricular assist device support reveals differences among device types

BACKGROUND

The natriuretic hormones ANP and BNP are expressed differently in the myocardium. Both hormones have compensatory diuretic activity during heart failure. Mechanical stretch of the myocardial walls induces the expression of these hormones. In failing human myocardium, both ANP and BNP are transcribed in the ventricular myocardium in high amounts. We measured the plasma concentrations of ANP and BNP in patients supported by various ventricular assist devices (VADs) at various times. We analyzed the time courses of ANP and BNP to determine (1) the time scale of their down-regulation as a marker of putative myocardial recovery, (2) their steady-state levels under VAD support and (3) differences caused by various VAD devices.

METHODS

We analyzed ANP and BNP using commercially available radioimmune assays. We analyzed the time courses of patients supported by Thoratec (THO) LVAD (n = 8), TCI Heartmate (TCI) (n = 6), Novacor (NOV) (n = 7), and Lionheart (LIO) (n = 3).

RESULTS

Patients supported with NOV and some patients with TCI showed down-regulation of BNP to a steady-state level at 30 to 50 days, following a single exponential decay. In contrast, patients supported by THO or LIO did not reveal a determined time course of the natriuretic hormones. Only a few patients reached normal plasma values during VAD support.

CONCLUSION

The time courses of ANP and BNP differ among VAD types because of construction and/or driving mode, which might be important when considering patients for weaning from VAD without heart transplant.

A versatile intracorporeal ventricular assist device based on the thoratec VAD system

BACKGROUND

As patients are supported for longer durations with paracorporeal Thoratec left ventricular and biventricular assist devices (longest durations: 515 and 457 days, respectively), there is a need for implantable options.

METHODS

We are developing a small, simple, and versatile intracorporeal ventricular assist device (IVAD) for left, right, or biventricular support as an alternative to the large, implantable, pulsatile left ventricular assist device (LVAD) systems available today. The new device is based on the Thoratec paracorporeal VAD that has been used in more than 1,400 patients weighing from 17 to 144 kg and for durations exceeding 1 year including patient discharge (using the portable driver).

RESULTS

The IVAD has the same blood flow path and Thoralon polyurethane blood pumping sac as the paracorporeal VAD, but the housing is a smooth contoured, polished titanium alloy. The IVAD has a new sensor to detect when the pump is full and empty, and is controlled with the Thoratec TLC-II portable VAD driver, which is a small, briefcase-sized, battery-powered, pneumatic control unit. A small flexible (9 mm OD) percutaneous pneumatic driveline for each VAD is tunneled out of the body from the LVAD or right VAD in a pre- or intraperitoneal position. Small size and simplicity are the major advantages of the new device. The IVAD weight (339 g) and implanted volume (252 mL) are approximately one-half that of the current implantable pulsatile electromechanical LVAD systems.

CONCLUSIONS

The small size of the IVAD should not only allow support of a large range of patient sizes and body habitus, but also provide options for implantable left, right, or biventricular support. By implanting only the mechanically simple blood pump, the more complex control unit is external, where it can be serviced and replaced without surgery. The IVAD with the portable driver will be a viable alternative to large implanted electromechanical systems and should address a larger segment of the physically diverse patient population.

Management of acute cardiac failure with mechanical assist: experience with the ABIOMED BVS 5000

BACKGROUND

Mechanical circulatory assist industries have developed ventricular assist devices (VAD) for short-, intermediate-, and long-term use. The purpose of this report is to describe the progress made with the ABIOMED Biventricular System (BVS) 5000 (ABIOMED, Inc, Danvers, MA) short-term VAD.

METHODS

From June 1994 through August 2000, all cardiogenic shock patients who required short-term mechanical assist were supported with the ABIOMED BVS 5000. Insertion criteria included any condition that may potentially result in cardiac recovery. A formal algorithm for timing of insertion was established to standardize implantation criteria.

RESULTS

A total of 45 patients were supported at Hahnemann University Hospital, Philadelphia, PA. There were 26 male and 19 female patients, with a mean age of 57.9 years (range 33 to 80 years). Devices were inserted for postcardiotomy shock in 36 patients (80%) and precardiotomy shock in 9 patients (20%). The average duration of support was 8.3 days (range 1 to 31 days). Overall, there were 22 (49%) patients weaned from support and 14 (31%) discharged from the hospital. For patients in whom the device was implanted in accordance with an established protocol (group A), the wean and discharge rates were 60% and 43%, respectively. The most common morbidities included bleeding and adverse neurologic events.

CONCLUSIONS

The ABIOMED BVS 5000 VAD continues to be a valuable form of short-term mechanical assist for acute cardiogenic shock. The formation of a uniform VAD insertion algorithm has helped to standardize protocols in management.

Device and patient management in a bridge-to-transplant setting

BACKGROUND

A variety of sophisticated devices have been developed for mechanical circulatory support in patients bridged to cardiac transplantation. Based on 13 years' experience, we have developed specific protocols for patient selection and management for different devices.

METHODS

The principal systems applied in the bridge-to-transplant cohort are the Thoratec ventricular assist device (n = 144, mean duration of support 53 +/- 57 days), the Novacor left ventricular assist system (LVAS) (n = 85, mean duration of support 154 +/- 15 days), and the HeartMate LVAS (n = 54, mean duration of support 143 +/- 142 days). The Thoratec device is used for biventricular assistance or if the duration of support is expected to be less than 6 months. For long-term support, either the Novacor or HeartMate LVAS are preferred.

RESULTS

Despite careful postoperative patient management, this group of patients is prone to a variety of complications. Bleeding occurred in 22% to 35%, right heart failure in 15% to 26%, neurologic disorders in 7% to 28%, infection in 7% to 30%, and liver failure in 11% to 20% of patients. Complications varied with the device applied and the patient's preoperative condition. A total of 73 patients were discharged from hospital for a mean period of 184 days; this cumulative experience amounted to 37.5 patient-years.

CONCLUSIONS

The Novacor and the HeartMate systems offer the additional possibility of discharging patients during support if they fulfill certain criteria. The main reasons for rehospitalization were thromboembolic and infectious complications.

Frequency, risk factors, and clinical outcomes of left ventricular assist device-associated ventricular thrombus

A retrospective, transesophageal study of 51 consecutive patients receiving a left ventricular (LV) assist device (AD) over a 2-year period showed that LVAD-associated LV thrombosis (16%) was predicted by acute myocardial infarction, atrial cannulation, and postimplantation bleeding, and was associated with a fourfold increased risk of stroke compared with patients without thrombosis. LV cannulation, when using short-term LVADs, may decrease the incidence of LV thrombosis, and early transition to Heartmate-LVAD support may improve outcome.

Infectious complications associated with ventricular assist systems

Infectious complications during support with a ventricular assist system (VAS) can cause severe morbidity and mortality, affecting nearly one-half of all VAS recipients. Because of the lack of a uniform definition of infection, the incidence of this complication is hard to determine accurately. It is approximately 50% for patients being supported by an implantable VAS as a bridge to heart transplantation and 28% for patients supported by an external, short-term VAS. Infections can be classified according to the involvement or noninvolvement of the implanted device and according to the severity of the infection. Severe infections involving the implanted device may preclude heart transplantation for some patients, but numerous patients with milder infections have undergone successful transplantation. Numerous factors predispose VAS patients to infection. Postoperative bleeding necessitating re-operation is an important contributing factor. Endotracheal tubes, intravascular catheters, and other indwelling tubes necessary for the care of postsurgical patients are also common routes of contamination. Control of infection may be improved with new VAS designs, antibiotic impregnated drivelines, and innovative therapies such as antibiotic beads. The next generation of VASs should be inherently less susceptible to infection because of their smaller size, reduced thrombogenicity, and better flow characteristics. In addition to more effective antibiotics, improved VAS designs that incorporate transcutaneous energy transmission systems may reduce infectious complications and allow safe, long-term VAS support.

Predictors of survival in patients bridged to transplantation with the thoratec VAD device: a single-center retrospective study on more than 100 patients

BACKGROUND

Careful patient selection markedly influences the outcome of patients who undergo mechanical circulatory support. Therefore, we tried to evaluate predictors of survival after implantation of the Thoratec ventricular assist device (VAD).

METHODS

Between October 1992 and January 2000, 104 patients (86 men, 18 women, aged 11 to 69 years) received the Thoratec VAD as a bridge to transplant. A total of 51 patients required left ventricular support (LVAD), 50 patients required biventricular support (BVAD), and 3 patients required total artificial heart implantation. We performed univariate analysis of 25 parameters with regard to their effect on survival and then applied a multivariate analysis to evaluate those factors that turned out to be marginally significant. We performed all analysis for the total collective as well as for the LVAD and BVAD sub-group.

RESULTS

The BVAD patients tended to have worse outcomes than did LVAD patients. We found no significant predictors of survival in either sub-group. In the total collective, however, we found the following pre-implant conditions were independent risk factors for survival after VAD implantation: patient age > 60 years (odds ratio [OR] 3.87, confidence interval [CI] 1.39 to 10.76), pre-implant ventilation (OR, 6.76; CI 2.42 to 18.84), and increased pre-implant total bilirubin (OR, 1.42; CL, 1.19 to 1.69).

CONCLUSIONS

Transplant candidates on inotropic support should be considered for bridging to transplant as soon as bilirubin values start to increase or before respiratory function deteriorates and ventilation becomes necessary. In elderly patients, careful patient selection, particularly considering potential risk factors, might favorably affect their outcomes.

Mechanical Circulatory Support Sources of Emboli and Neurological Outcome

Long-term mechanical circulatory support devices are currently used as bridges to transplantation or myocar dial recovery and represent a major step forward in the treatment of end-stage heart failure. Examples of left ventricular assist devices/systems are Thoratec Labora tories (Berkley, CA), Baxter Novacor (Oakland, CA), and Thermo Cardiosystems Inc Heartmate (Woburn, MA). The CardioWest (Tucson, AZ) is the current total artifi cial heart device under clinical evaluation. These de vices are associated with neurological complications usually resulting from thromboembolic events to the cerebrum, cerebellum, or brainstem. The device itself is the commonest source of these emboli. Thrombus formation within the device occurs as a result of the interaction between the blood contacting surfaces of the device, the flow of blood through the device, and thrombotic tendency of the blood. There is a wide range of clinical presentation, from asymptomatic emboli detected by transcranial Doppler to devastating strokes. Strategies aimed to reduce the tendency to form throm bus are based on aggressive prevention with anticoagu lation and antiplatelet therapy and/or by design modifi cation. In particular, the use of a textured inner surface that encourages the formation of a pseudoneointima seems successful in reducing anticoagulation require ments and neurological complications.

Analysis of the arterial blood pressure waveform using Fast Fourier Transform technique during left ventricular nonpulsatile assistance: in vitro study

The arterial blood pressure waveform is variable during left ventricular assistance. The aim of this study is to examine the correlation between the left ventricular assist device (LVAD) condition and the arterial blood pressure waveform in a fixed cardiac output condition using a mock circuit. This mock circulation loop was composed of an aortic compliance chamber, a left atrial compliance chamber, a pneumatic pulsatile pump as a native heart, and a rotary blood pump representing the LVAD with left atrial drainage. The Fast Fourier Transform technique was utilized to analyze the arterial blood pressure waveform and calculate the pulsatility index (PI) and the pulse power index (PPI). The PI and PPI decreased with the increase of the LVAD rotational speed, exponentially. There was a significant negative correlation between the PI, PPI, and the LVAD rotational speed, flow rate, and assist ratio. The best correlation was observed between the PPI and the assist ratio (r = 0.986). From this viewpoint, an ideal LVAD condition may be estimated from the pulsatility change of the arterial blood pressure waveform.

Development of an intracorporeal Thoratec ventricular assist device for univentricular or biventricular support

There is a need for a small, simple, and versatile intracorporeal ventricular assist device (IVAD) as an alternative to the large implantable electromechanical LVAD systems in current use. Because the basic design of the Thoratec paracorporeal VAD has been demonstrated in over 1,000 patients, weighing from 17 to 144 kg, and for durations up to 515 days including patient discharge (by using the portable driver), we are developing a new intracorporeal version of our VAD. This IVAD has a smooth contoured, polished titanium housing, and maintains the same blood flow path and Thoralon polyurethane blood pumping sac as the paracorporeal VAD. The IVAD is controlled with the Thoratec TLC-II Portable VAD Driver, which is a small briefcase sized, battery powered, pneumatic control unit. Intracorporeal LVADs and/or RVADs are implanted in a preperitoneal position, with a single small (9 mm OD) percutaneous pneumatic driveline for each VAD. The major advantages of the new IVAD design are size and simplicity. The IVAD weight (339 g) and implanted volume (252 ml) are substantially smaller than current implantable electromechanical LVAD systems. Only the small blood pump is implanted, leaving the more complex control unit external, where it can be serviced and replaced. The versatile design is intended for left and/or right heart support in large or small patients. The IVAD in combination with the TLC-II portable driver will be a viable and attractive alternative to large, implanted electromechanical systems.

Left ventricular assist device bridge therapy for acute myocardial infarction

BACKGROUND

Patients with acute myocardial infarction (AMI) complicated by cardiogenic shock have a high mortality rate. Current treatment modalities remain suboptimal for these patients.

METHODS

From April 1995 to March 1998, 7 patients were identified as having AMI associated with cardiogenic shock. All received intraaortic balloon pump assistance, in addition to maximal inotropic support.

RESULTS

The mean preoperative cardiac index was 2.0+/-0.3 L/min/m2 and pulmonary capillary wedge pressure was 23+/-6 mm Hg. Three patients received thrombolytic therapy and 4 patients underwent percutaneous transluminal coronary angioplasty without success. Left ventricular assist devices (LVADs) were implanted as bridge therapy to heart transplantation. One patient died from recurrence of a ventricular septal defect during LVAD support. Six patients were transplanted successfully after mean LVAD support of 59+/-33 days. Five patients are alive and well at a mean follow-up of 898+/-447 days. One patient died 3 days after transplantation from acute allograft dysfunction.

CONCLUSIONS

Timely application of LVADs as bridge therapy to heart transplantation in these critically ill patients can be lifesaving, and should be investigated further.

Novacor left ventricular assist system versus Heartmate vented electric left ventricular assist system as a long-term mechanical circulatory support device in bridging patients: a prospective study

OBJECTIVE

Long-term mechanical circulatory support as a bridge-to-transplantation procedure and bridge to recovery is of increasing importance. The implantable left ventricular assist devices, Novacor N100 left ventricular assist system (Baxter Healthcare Corporation, Berkeley, Calif) and TCI HeartMate vented electric left ventricular assist system (Thermo Cardiosystems Inc, Woburn, Mass), have proved to be efficient devices in bridge-to-transplantation settings and for prolonged support. The two systems were compared with regard to reliability and morbidity.

METHODS

Between October 1996 and March 1998, a prospective, single-center study was done that included 40 patients, 20 of whom were treated with the Novacor system and 20 of whom were treated with the HeartMate device. The diseases were mainly dilated cardiomyopathy (13/9) and ischemic cardiomyopathy (6/10). There were no statistically significant differences between the two groups regarding age, sex, preoperative clinical blood chemistry values, hemodynamic data, or risk factors.

RESULTS

There were no statistically significant differences between the two groups with regard to postoperative hemodynamics, organ recovery, out-of-hospital support, and survival to heart transplantation. Mean duration of support was 235.3 +/- 210 days for the Novacor group and 174.6 +/- 175 days for the HeartMate group and mean out-of-hospital support was 241 +/- 179 days and 166 +/- 152 days for the two groups, respectively. Neurologic complications occurred significantly more often among the Novacor group, whereas the HeartMate group had a higher prevalence of infections and technical problems, which was statistically significant. Survival to transplantation was 65% for the Novacor group and 60% for the HeartMate group.

CONCLUSIONS

Most patients had organ recovery with left ventricular assist system support, and a considerable number of patients in both groups underwent transplantation. However, both devices need revision to address the current problems, that is, thromboembolism for the Novacor device and infection and reliability for the HeartMate device.

Single-center experience with the thoratec ventricular assist device

OBJECTIVE

The Thoratec ventricular assist device (Thoratec Laboratories, Pleasanton, Calif) is widely accepted for univentricular and biventricular support in patients with various indications. The aim of this study is to describe our experience with implantation of the Thoratec ventricular assist device in more than 100 patients.

METHODS

From March 1992 to June 1998, 114 patients (98 men and 16 women; mean age, 47.9 years) received the Thoratec ventricular assist device for a mean duration of 44.9 days. The patients were divided into 3 groups. Group 1 included 84 patients in whom the system was applied as a bridge-to-transplant procedure. Group 2 included 17 patients with postcardiotomy cardiogenic shock, and group 3 included 13 patients with cardiogenic shock of other causes.

RESULTS

Sixty-eight percent of patients in group 1 survived to transplantation with a posttransplant survival of 88%. The only independent risk factor affecting survival was age more than 60 years. Survivals in groups 2 and 3 were 47% and 31%, respectively. Main complications in all groups were bleeding, multiple organ failure, liver failure, sepsis, and neurologic disorders.

CONCLUSIONS

The Thoratec ventricular assist device has proved to be a reliable device for bridge to transplantation and postcardiotomy support. Further studies are required on patient selection and on patient and device management to reduce the incidence of complications in these patient populations.

New technique for the outflow cannulation of right ventricular assist device

Cannulating the outflow cannula of a right ventricular assist device (RVAD) through the main pulmonary artery is often troublesome because of extensive dissecting adhesion. We implanted RVADs using the new technique for outflow cannulating through the right pulmonary artery between the ascending aorta and the superior vena cava. With this technique, we needed only a little dissection and no cardiopulmonary bypass. This technique could make RVAD implantation simple, quick, and safe.

Temporary pulsatile ventricular assist devices and biventricular assist devices

BACKGROUND

During the past years several systems for mechanical circulatory support have become available. In this study we describe our experience with short-term and mid-term application of the ABIOMED and Thoratec device.

METHODS

Since 1990 the ABIOMED BVS and since 1992 the Thoratec VAD have been applied to 75 and 103 patients, respectively, with postcardiotomy heart failure, as a bridge-to-transplant procedure, and with different other indications.

RESULTS

In the ABIOMED collective 25 of 50 patients (50%) with postcardiotomy heart failure and 1 of 4 patients with miscellaneous other indications could be discharged from hospital, 7 of 14 bridge-to-transplant patients (50%) underwent transplantation with a posttransplant survival of 86%. In the Thoratec collective 6 of 10 patients (60%) with postcardiotomy heart failure and 4 of 8 patients (50%) with miscellaneous indications could be discharged from hospital, 48 bridge-to-transplant patients (74%) underwent transplantation with a posttransplant survival of 90%.

CONCLUSIONS

The results show the versatility of the Thoratec VAD for short-term and mid-term application in patients with postcardiotomy heart failure and as a bridge-to-transplant procedure. The use of the ABIOMED device is not indicated for bridging patients to transplantation. Although in case of postcardiotomy heart failure, Thoratec is also superior to ABIOMED, the high costs of the Thoratec VAD limits its wide acceptance in this patient cohort.

Mechanical circulatory support devices in the treatment of heart failure

With an increasingly aging population, heart failure is a major health issue, affecting more than 10% of the population over 65 years of age, and costing hundreds of millions of dollars per year for ongoing care. Even with maximal medical therapy, annual mortality rates of in excess of 25% are commonly reported. Over the last three decades, various surgical approaches have been examined in the hope of improving the outcome of congestive cardiac failure. These procedures range from simple coronary revascularisation to left ventricular reduction surgery and cardiac transplantation. Although of value in selected situations, no surgical approach, beyond transplantation, has had significant impact on the outcome of heart failure. In the last decade, development in the area of mechanical support for the failing heart has continued to expand at a rapid rate. Strong evidence now exists to show that in many patients with advanced heart failure, prolonged mechanical support results in significant myocardial recovery. There are currently several mechanical support devices available for clinical use, although most are considered experimental in this country. These devices are expensive and are not without significant complications, but early results of their use as either a bridge to transplantation or as a stand alone treatment, have been very encouraging. Currently available mechanical assist devices are described, with discussion of indications for implantation, complications and results of their use.

Usefulness of postoperative percutaneous cardiopulmonary support using a centrifugal pump: retrospective analysis of complications

Between January 1992 and December 1997, we employed percutaneous cardiopulmonary support (PCPS) using a centrifugal pump in 25 patients. In 21 of them, PCPS was used postcardiotomy. These patients could not be weaned from cardiopulmonary bypass due to profound ventricular failure. As for the other 4 patients, PCPS was used preoperatively for profound cardiogenic shock, a thrombosed valve, a stuck valve, and pulmonary embolization. Nine patients (43%) were weaned from PCPS (Group 1), and 3 (14%) were discharged from the hospital. The other 12 patients (57%) had perioperative extensive myocardial infarction and could not be weaned (Group 2). The causes of death were bleeding and multiple organ failure (MOF) associated with ventricular failure. The reasons for MOF were perioperative massive transfusion and hepatic congestion caused by sustained ventricular failure. To increase the survival rate, complete hemostasis and prevention of increased central venous pressure by early use of PCPS are necessary.

Major organ function under mechanical support: comparative studies of pulsatile and nonpulsatile circulation

We examined a major organ function during 3 h biventricular assisted circulation after acute myocardial infarction model in the pig. In left ventricular circulation, the outflow cannula was placed in the ascending aorta and an inflow cannula through the mitral valve in the left ventricle. A pump (pulsatile group, Zeon Medical, Inc., Tokyo, Japan and nonpulsatile group, Nikkiso HPM-15, Nikkiso, Inc., Tokyo, Japan) was connected to each cannula. In right ventricular circulation, the outflow cannula was placed in the pulmonary artery and an inflow cannula in the right ventricle. The right ventricular circulation was supported by a nonpulsatile pump (Nikkiso HPM-15). The items measured were the regional blood flows of the cortex and medulla in the kidney, white matter and gray mater in brain, and liver; renal arterial flow; carotid arterial flow; portal vein flow; common hepatic arterial flow; arterial ketone body ratio (AKBR); and lactate/pyrubic acid (L/P). In the pulsatile group, the renal cortical blood flow increased, and the medulla blood flow decreased. On the other hand, in the nonpulsatile group, both regional blood flows decreased. That means that in the pulsatile assisted group intrarenal redistribution improved rather than in the nonpulsatile assisted group. In addition the liver regional blood flow, AKBR, and L/P showed significant differences between the pulsatile and nonpulsatile groups. On the other hand, the white matter and gray matter regional blood flows and carotid arterial flow did not show significant differences between the groups. The results of our study indicated that pulsatile circulation produced superior circulation in the kidney and liver, and microcirculation on the cell level was superior as well in early treatment of acute heart failure.

[Microcirculation of kidney and skin during left ventricular assisted circulation--comparative studies of pulsatile and nonpulsatile assists]

We examined microcirculation of the kidney and skin over a six-hour period in an acute myocardial infarction model in pigs. The outflow cannula was placed in the ascending aorta, the inflow cannula was placed the in left atrium, and a pump was connected to each (pulsatile group, Zeon Medical pneumatic pump; nonpulsatile group, Nikkiso HPM-15). Items examined included the regional blood flow of the cortex and medulla in the kidney and skin, renal and carotid arterial flow, arterial ketone body ratio (AKBR), lactate/pyruvic acid (L/P), BUN, creatinine, and beta 2-microglobulin. After the experimental study, the major organs were removed and a pathological study was performed. The mean aortic pressure after the assist could be maintained at about 100 mmHg. There were no significant differences between the two groups in mean aortic pressure and total cardiac output. Under assisted circulation, the pulse pressure was maintained at about 15 mmHg in the nonpulsatile group and about 40 mmHg in the pulsatile group. After the assist, there were no significant differences in the carotid arterial blood flow between the two groups. However, there were significant differences between the two groups in the renal arterial, renal cortical, and regional skin blood flows. In the laboratory data, there were significant differences between the two groups in AKBR, L/P, and beta 2-microglobulin. Pathological findings on the kidney in the nonpulsatile group showed expansion of the proximal tubes, retention of red blood cells, and expansion of blood capillaries within the glomerulus. On the other hand, the pulsatile group showed almost normal formation. In the lungs, the nonpulsatile group showed edematous change in the air cells and the pulsatile group showed almost normal formation. The results of the previous and current study indicated that the pulsatile assist produced superior circulation in the kidney and peripheral organs and superior cellular metabolism in the early treatment of acute left cardiac failure. On the other hand, nonpulsatile assisted circulation was found to be ineffective in maintaining the circulation in the body, and to be potentially capable of causing irreversible damage of major organs if continuous for more than three hours. The results also indicated that pulsatility was necessary to maintain normal circulation in the peripheral organs and cellular metabolism in the early treatment of acute left cardiac failure.

Importance of preoperative liver function as a predictor of survival in patients supported with Thoratec ventricular assist devices as a bridge to transplantation

Patient selection is crucial for the success of ventricular assist devices as a bridge to heart transplantation.

PURPOSE

The objective of this study was to identify preoperative markers for survival and end-organ recovery in patients having a ventricular assist device.

METHODS

A retrospective study was performed on 32 severely ill patients with end-stage cardiac failure being mechanically bridged to heart transplantation with the Thoratec Ventricular Assist Device System (Thoratec Laboratories Corporation, Pleasanton, Calif) in a single center between 1984 and 1995. The preoperative cardiac index averaged 1.6 L/min per square meter with a pulmonary capillary wedge pressure of 29 mm Hg. Because of a high incidence of hepatic or renal dysfunction, or both (total bilirubin: 3.5 +/- 6.2 mg/dL; creatinine: 2.0 +/- 1.3 mg/dL), biventricular support was used in most patients (28/32). A total of 30 preoperative and 4 perioperative variables were evaluated for their association with survival and liver recovery.

RESULTS

Nineteen patients (59.4%) survived to transplantation and 13 died. All 19 patients undergoing transplantation were discharged alive with a 1-year survival of 94.4%. All patients without liver recovery died of multiorgan failure. Direct and indirect bilirubin measurements were the only significant predictors for survival to discharge (P = .036, .045); all other factors failed to show significance. As direct bilirubin levels increased (normal range, 3 times normal, and >3 times normal), patient survival decreased (82 %, 56%, and 33 %, respectively). In addition, bilirubin and liver enzyme levels before insertion of the assist device were significantly associated with liver recovery during support with the device.

CONCLUSION

In our patient population with ventricular assist devices, liver function is the most predictive factor of patient survival in bridging to transplantation.