The Pierce-Donachy ventricular assist device as a bridge to cardiac transplantation

Mechanical heart valve performance in a pulsatile pediatric ventricular assist device

A pulsatile pediatric ventricular assist device with a dynamic stroke volume of 12 ml is currently under development at the Pennsylvania State University. A monoleaflet valve (Björk-Shiley Monostrut) and a bileaflet valve (CPHV, CarboMedics Prosthetic Heart Valve) were examined in this study. A high-speed video and data acquisition system was used to simultaneously record video images, pressure waveforms, and flow waveforms for an array of in vitro test conditions that varied heart rate and systolic duration. The CPHV in both the horizontal and vertical orientations have larger regurgitant volumes than the Monostrut valves at all operating conditions in both the inlet and outlet positions. However, the CPHV has higher stroke volumes and cardiac outputs than the Monostrut valve at higher heart rates and longer systolic durations. In addition, the hydrodynamic performance of the Monostrut valve is more sensitive to changes in operating conditions for the pulsatile pediatric ventricular assist device than the CPHV in both orientations. Additional testing is under way to identify the optimal operating conditions for each type of valve.

Left ventricular assist devices: current status and future applications

Despite the advances in the medical management of heart failure over the last 20 years it remains a major cause of morbidity and mortality. While cardiac transplantation has evolved into an established mode of therapy, the number of patients with severe heart failure who could benefit from cardiac transplantation far exceeds the supply of donor organs. The development of an implantable left ventricular assist device (LVAD) began in the early 1970s in centres such as the Texas Heart Institute and was funded by the National Heart, Lung, and Blood Institute. Clinical trials of these devices began in the mid 1980s and several hundred patients have now been supported with one or other of these devices. Most patients have had an LVAD implanted as a bridge to cardiac transplantation. Recently there has also been interest in the use of an LVAD for (a) permanent ventricular support and (b) as a bridge to recovery in patients with potentially reversible causes of heart failure.

Mechanical circulatory support: lessons from a single centre

Over recent years, a number of different mechanical circulatory support (MCS) products have been developed to a stage where they are no longer investigational devices. Registry data provide some information, but this is limited by the mix of historical and contemporary data and the voluntary nature of the contributions. As yet, there are no clear guidelines for patient selection, the differential application of generically different devices or for optimal patient management. Ours is a busy centre offering a comprehensive cardiovascular service. This review details our experience since 1987 and 189 patients supported with five different types of device, used in all of the common applications. Our experience has permitted the formulation of some general principles and guidelines. Data published by registries and by individual manufacturers are, as yet, not standardized. We hope that our experience will be of interest to those centres wishing to establish a mechanical assist service.

Infections during extended circulatory support: University of Alabama at Birmingham experience 1989 to 1994

BACKGROUND

The University of Alabama at Birmingham experience with investigational ventricular assist devices (VADs) used as a bridge to transplantation has increased over the past several years; it now includes 27 VAD implantations with 13 VAD runs lasting for extended periods (ie, > 30 days). A review of complications experienced by patients during extended VAD runs is warranted before the further development and testing of chronically implanted mechanical circulatory support devices.

METHODS

This study focuses on the infectious complications of extended VAD support; it includes 13 patients who were supported by either a Thoratec or HeartMate VAD for longer than 30 days pending cardiac transplantation. Infection was defined as any positive culture. The infections were classed according to site and severity as follows: class I were patient-related non-blood-borne infections, class II were blood-borne infections, class III were VAD percutaneous site infections, and class IV were infections of the blood-contacting surfaces or intracorporeal components of the VAD.

RESULTS

The 8 Thoratec and 5 HeartMate patients were supported for a total of 1,648 days with a range of 33 to 279 days per patient. Every patient had at least one infection; however, there were 6 patients who had no class II or IV infections during the period of support. One of these 6 patients died of a stroke, whereas the other 5 patients survived VAD support. No trends were identified for a change in the incidence of bacterial compared with fungal infections during the course of VAD support. There was no trend for a greater number of infections in patients who died during VAD support compared with those who survived. Neither class II nor IV infections precluded transplantation. Three patients died during VAD support; 1 died as a direct consequence of fungal infection. Eight patients received transplants. One patient had an unanticipated recovery of cardiac function and the VAD was removed. Support in 1 patient is ongoing.

CONCLUSIONS

Infection during VAD support pending cardiac transplantation is an important cause of morbidity and mortality in patients maintained for longer than 30 days by circulatory assist. Infectious complications will probably be a prominent component of the risk associated with the use of chronically implanted mechanical circulatory assist devices and will likely have an important effect on the quality of life experienced by these patients.

Mechanical circulatory support: the Bad Oeynhausen experience

From September 1987 to February 1994, we treated 147 patients ranging between 11 and 82 years old with different mechanical circulatory support systems. The applied devices were the Bio-Medicus centrifugal pump in 61 patients, the Abiomed BVS System 5000 in 49 patients, the Thoratec ventricular assist device in 42 patients, and the Novacor left ventricular assist device in 7 patients. On the basis of indication for mechanical circulatory support, the patients were divided into three groups: group 1 consisted of 72 patients with postcardiotomy cardiogenic shock; group 2, 50 patients in whom mechanical support was used as a bridge to cardiac transplantation; and group 3 (miscellaneous), 25 patients in cardiogenic shock resulting from acute myocardial infarction (n = 14), acute fulminant myocarditis (n = 3), primary graft failure (n = 2), right heart failure after heart transplantation (n = 3), and acute rejection (n = 3). Time of support ranged from 1 hour to 97 days (mean duration, 10.8 days). Seventy-five patients (51%) were discharged from the hospital. The best survival rate was achieved in group 2 with 72%, followed by group 1 with 44% and then group 3 with 28%. The most frequent complications in group 1 were bleeding (44%), multiple-organ failure (24%), neurologic disorders (18%), and acute renal failure (15%). In group 2, the major complications were bleeding (34%) and cerebrovascular disorders (22%) and in group 3, multiple-organ failure and sepsis (60%) and bleeding (32%).

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)

First successful bridge to cardiac transplantation using direct mechanical ventricular actuation

Currently available ventricular assist devices are technically difficult to implant, require continuous anticoagulation, and are associated with hemorrhagic and thromboembolic complications. Direct mechanical ventricular actuation is a biventricular assist device that can be applied in 3 to 5 minutes through a left anterior thoracotomy and has no direct blood contact or need for anticoagulation. The present study was designed to determine the effects of direct mechanical ventricular actuation in total biventricular circulatory support. Cardiogenic shock refractory to standard therapy developed in 2 patients awaiting cardiac transplantation. Direct mechanical ventricular actuation was applied and provided immediate hemodynamic stabilization in both. All inotropic agents and intraaortic balloon support were then discontinued. Fifty-six hours of circulatory support bridged the first patient to successful cardiac transplantation without complication. The patient is alive and well more than 1 year later without incident of infection or rejection. The second patient suffered cardiac arrest and required closed chest cardiopulmonary resuscitation before device application. After 45 hours of support, it was determined that irreversible neurologic injury had occurred and direct mechanical ventricular actuation was discontinued. Neither patient's native heart exhibited any histologic evidence of device-related trauma. Direct mechanical ventricular actuation has undergone limited clinical investigation since its original description 25 years ago, but in these initial trials, the device has proved effective. The concept of mechanically actuating the ventricles appears to be a valuable, yet under-utilized method of total circulatory support.

Early detection of active cytomegalovirus (CMV) infection after heart and kidney transplantation by testing for immediate early antigenemia and influence of cellular immunity on the occurrence of CMV infection

To determine the incidence of active cytomegalovirus (CMV) infection after organ transplantation and its relationship with the immune system, 55 renal and 14 cardiac transplant recipients were closely monitored for active CMV infection (expression of CMV immediate early antigen in granulocytes--antigenemia--and positive cultures) and immune parameters. All 19 CMV-seronegative recipients with seronegative donors remained seronegative, showing that no CMV transmission occurred by leukocyte-depleted blood products. Primary CMV infection occurred in 4 of 11 (36%) patients with positive donors and was symptomatic in 1 (9%) patient. Active CMV infection was found in 29 of 39 (74%) seropositive patients and was symptomatic in 3 (8%) patients. CMV antigenemia was always the first indication of active CMV infection (antigenemia, on average, at day 45 +/- 15; immunoglobulin G rise at day 71 +/- 36; and positive cultures at day 70 +/- 17). Cellular immunity, as measured by lymphocyte proliferation (LPT), proved to be of importance in the prevention of active CMV infection, as 14 of 15 patients with negative LPT obtained active CMV infections with antigenemia and positive cultures, whereas 1 of 10 patients with positive LPT did so (P less than 0.0001).

Extension of donor criteria in cardiac transplantation: surgical risk versus supply-side economics

To combat the continuing shortage of ideal donor hearts, we have used cardiac allografts from high-risk donors for critically ill recipients. We defined high-risk donor variables as age greater than 40 years, systemic (noncardiac) infection, cardiopulmonary resuscitation greater than 3 minutes, ischemic time longer than 5 hours, weight more than 20% less than that of the recipient, and requirements for high doses of inotropes. Of the 305 donors we have used, 73 (23.9%) have been high-risk, with 59/73 (80.8%) exhibiting one variable, 12/73 (16.4%) exhibiting two variables, and 2/73 (2.7%) exhibiting three variables. No correlation was found between the number of donor variables and a poor postoperative result. No infectious complications occurred in 17 patients receiving hearts from potentially infected donors. Hospital mortality rates (30 day) for recipients of high-risk donor versus non-high-risk donor hearts were 8.2% and 6.9%, respectively (not significant). The 1-, 6-, and 12-month actuarial survival rates were 91.7%, 81.2%, and 75.9% for the high-risk donor group and 93.5%, 80.3%, and 77.8% for the non-high-risk donor group (not significant). Among survivors with high-risk donor hearts, mean left ventricular ejection fractions were 0.54 +/- 0.08 at 3 months, 0.55 +/- 0.08 at 1 year, and 0.54 +/- 0.09 at 2 years after transplantation. These results suggest that accepting less than ideal donor hearts can be safe and might be considered when better options are not available.