The continuing evolution of mechanical ventricular assistance

Postoperative Care of the Cardiac Surgical Patient

The subspecialty of interventional cardiology began in 1977. Since then, the discipline of interventional cardiology has matured rapidly, particularly with regards to ischemic heart disease. As a result, more patients are undergoing percutaneous catheter interventional therapy for ischemic heart disease and fewer patients are undergoing surgical myocardial revascularization. Those patients referred for surgical revascularization are generally older and have more complex problems. Furthermore, as the population ages more patients are referred to surgery for valvular heart disease. The result of these changes is a population of surgical patients older and sicker than previously treated.

Ventricular assistance to bridge to transplantation

In 2001, 2202 heart transplants were performed in the United States, leaving 4137 patients waiting who suffer from 30% annual mortality. Status I, Class IV heart failure patients have a 66% 1-year mortality rate and a survival approximating our worst cancers. Left ventricular assist devices (LVADs) first successfully bridged a patient to transplantation in 1978. LVADs have since functioned primarily thus, minimizing end-organ damage and providing rehabilitation potential for individuals awaiting transplantation. In this role, their effectiveness is well-established: they gain time for patients awaiting donors, preserve end-organ function, and provide potential for a high quality of life in and out of the hospital. This success has been the result of numerous advances in VAD technology, which this article discusses.

Inpatient transfers to the intensive care unit: delays are associated with increased mortality and morbidity

OBJECTIVE

To examine if delayed transfer to the intensive care unit (ICU) after physiologic deterioration is associated with increased morbidity and mortality.

DESIGN

Inception cohort.

SETTING

Community hospital in Ogden, Utah.

PATIENTS

Ninety-one consecutive inpatients with noncardiac diagnoses at the time of emergent transfer to the ICU. We determined the time when each patient first met any of 11 pre-specified physiologic criteria. We classified patients as "slow transfer" when patients met a physiologic criterion 4 or more hours before transfer to the ICU. Patients were followed until discharge.

INTERVENTIONS

None.

MEASUREMENTS

In-hospital mortality, functional status at hospital discharge, hospital resources.

MAIN RESULTS

At the time when the first physiologic criterion was met on the ward, slow- and rapid-transfer patients were similar in terms of age, gender, diagnosis, number of days in hospital prior to ICU transfer, prehospital functional status, and APACHE II scores. By the time slow-transfer patients were admitted to the ICU, they had significantly higher APACHE II scores (21.7 vs 16.2; P =.002) and were more likely to die in-hospital (41% vs 11%; relative risk [RR], 3.5; 95% confidence interval [95% CI], 1.4 to 9.5). Slow-transfer patients were less likely to have had their physician notified of deterioration within 2 hours of meeting physiologic criteria (59% vs 31%; P =.001) and less likely to have had a bedside physician evaluation within the first 3 hours after meeting criteria (23% vs 83%; P =.001).

CONCLUSIONS

Slow transfer to the ICU of physiologically defined high-risk hospitalized patients was associated with increased risk of death. Slow response to physiologic deterioration may explain these findings.

Platelet activation, aggregation, and life span in calves implanted with axial flow ventricular assist devices

BACKGROUND

A variety of rotary blood pumps are under development worldwide to serve as chronic ventricular assist devices (VADs). Historically VADs have been associated with thrombotic and thromboembolic complications, yet the ability to evaluate the thrombotic process in preclinical device testing has been limited.

METHODS

We have developed and applied flow cytometric assays for activated platelets, platelet microaggregates, and platelet life span and consumption to calves implanted with an axial flow VAD and calves undergoing a sham surgical procedure.

RESULTS

Surgical sham calves had significant increases in circulating activated platelets (p < 0.05) that resolved within 17 days, and no increases in circulating platelet microaggregates. Calves with uneventful VAD implant periods had early transient elevations in platelet microaggregates and prolonged elevations in activated platelets that did not recover to preoperative values during the study. Daily platelet consumption in VAD implanted calves was increased by 20% +/- 3%. Calves with thrombotic deposition within the VAD and elevated thromboembolism observed at autopsy experienced increases in circulating activated platelets and microaggregates at the end of the implant period when VAD flow decreased.

CONCLUSIONS

This study demonstrates the ability of flow cytometry-based platelet assays to differentiate VAD implant operations from VAD support, and suggests differences that exist between uneventful VAD support and support with complications. These techniques should have value in evaluating other cardiovascular devices undergoing preclinical testing and provide insight into the temporal impact of these devices on the hemostatic system.

Blood biocompatibility analysis in the setting of ventricular assist devices

Ventricular assist devices (VADs) are increasingly applied to support patients with advanced cardiac failure. While the benefit of VADs in supporting this patient group is clear, substantial morbidity and mortality occur during the VAD implant period due to thromboembolic and infective complications. Efforts at the University of Pittsburgh aimed at evaluating the blood biocompatibility of VADs in the clinical, animal, and in vitro setting over the past decade are summarized. Emphasis is placed on understanding the mechanisms of thrombosis and thromboembolism associated with these devices.

Nursing and psychosocial issues of patients on mechanical support

Mechanical support technology continues to evolve. Ongoing research has led to more efficient devices allowing for discharge to outpatient or home settings. From December of 1991 to July 31, 2000 the Cleveland Clinic Foundation has placed 240 mechanical support devices. These include 173 HeartMate devices of the Pneumatic or Vented Electric models, 56 Novacors, and 11 Thoratecs. Patients placed on mechanical support potentially proceed through six phases of support. This begins with the evaluation process and progresses through the perioperative phase, the intensive care phase, the regular nursing floor phase, discharge, and transplantation. We have developed a specialized team to care for this patient population. As a result, the nursing and psychosocial care of patients on mechanical support has advanced over years of experience. We have been able to identify specific nursing and psychosocial issues that develop through the phases of support. Becoming aware of these issues will assist in a successful outcome for the patient.

Cardiac transplantation and other therapeutic options in the treatment of end-stage heart disease

This article focuses on the surgical treatment of heart failure. It reviews the advances and limitations of heart transplantation and gives a broad overview of emerging technologies in the treatment of end-stage heart disease.

Survival outcomes of patients with giant cell myocarditis bridged by ventricular assist devices

Giant cell myocarditis is a highly lethal disorder characterized by rapidly progressive congestive heart failure. The aim of this study was to describe the clinical course of patients with giant cell myocarditis who received a ventricular assist device. Patients with giant cell myocarditis were identified from the Multicenter Giant cell Myocarditis Registry. Bridging to cardiac transplantation in the giant cell myocarditis patients who received a ventricular assist device was compared with bridging in the general population of heart failure patients, as reported in the literature. Median posttransplantation survival for patients with giant cell myocarditis who received and did not receive ventricular assist devices was calculated by the Kaplan-Meier method and compared with use of the log-rank test. Nine patients with giant cell myocarditis who received ventricular assist devices were identified. Seven patients survived to transplantation, four were alive 30 days posttransplantation, and two survived to 1 year. The rate of successful bridging to transplantation in seven of nine patients (78%) is similar to that reported for other ventricular assist device recipients. Posttransplantation survival of 57% (4 of 7) at 30 days and 29% (2 of 7) at 1 year was significantly lower compared with 93% 1-year survival of the 30 patients with giant cell myocarditis who did not receive ventricular assist devices before transplantation (p<0.001). Ventricular assist devices can be an effective bridge to transplantation for patients with heart failure caused by giant cell myocarditis. Although their posttransplantation survival was poor in our series, a few patients had long-term survival.

Control strategy for biventricular assistance with mixed-flow pumps

A left ventricular assist device (LVAD) is an effective method to rescue severe heart failure. Although some require a biventricular assist, the control method for the biventricular assist device (BVAD) with a rotary pump is rarely shown. The objective of this study was to investigate the strategy for controlling BVAD with rotary pumps by in vivo studies. Using 5 piglets, we set a BVAD through a left thoracotomy and made global ischemia for 30 min by clamping the base of the ascending aorta. After unclamping, the analysis of pumping performance acted for 6 h reperfusion. We set the target flow of the LVAD and set the right ventricular assist device (RVAD) speed limit as less than when the atrial collapse occurs. To detect the ventricular collapse without any specific sensor, we calculated the index of current amplitude from motor current waveform and simultaneous mean current value. In all cases, over 6 h of observation was performed, and the RVAD was weaned almost automatically.

Cardiac ventricular support. Considerations for psychiatry

Cardiac ventricular support is fostering additional roles for psychiatric consultation with this vulnerable end-of-life cardiac group. Incidence of premorbid and postsurgical psychiatric disorders (Axis I), psychotropic use, neurologic events, and mortality was obtained for 21 Novacor left-ventricular assist system patients prospectively and 13 Abiomed left/right ventricular-assist device patients retrospectively. This fragile patient population and their families warrant involvement for psychiatry because of the extreme conditions and consequences associated with mechanical cardiac assistance. The authors address psychiatric morbidity and neurobehavioral modifications associated with ventricular support.

Cardiopulmonary bypass: new strategies for weaning from cardiopulmonary bypass

This review focuses on weaning from cardiopulmonary bypass, a very critical time for patients and anaesthetists and frequently requiring major therapeutic effort. Few novel strategies for weaning have been described recently. Most drugs or approaches described during the review period are already well established. Emphasis is placed on the importance of non-cardiac factors, and on the importance of diastolic ventricular function as opposed to systolic function.

Management of sternal and abdominal wounds in a pediatric heart transplant patient

A 14-year-old girl with congenital heart disease underwent ventricular assist device placement before cardiac transplantation. The inability to close her abdominal fascia necessitated the placement of Prolene mesh, which subsequently became exposed and contaminated when her incision dehisced. Stable closure was obtained with Vicryl mesh and a rectus abdominis turnover flap. Her posttransplant course was notable for compression of the donor heart, necessitating prolonged open sternotomy. She failed an attempt at delayed sternal closure due to compression of the right ventricle by the sternum. In addition to standard pectoralis advancement flaps, a pedicled osseous sternal flap based on her left internal mammary artery was developed to avoid ventricular compression yet still provide some protection to the mediastinum. Alternative uses of this vascularized bone flap to assist with chest wall reconstruction are discussed.

Cardiac xenotransplantation

Heart failure is an important medical and public health problem. Although medical therapy is effective for many people, the only definitive therapy is heart transplantation, which is limited severely by the number of donors. Mechanical devices presently are used as "bridges" to transplantation. Their widespread use may solve the donor shortage problem, but at present, mechanical devices are limited by problems related to blood clotting, power supply, and foreign body infection. Cardiac xenotransplantation using animal donors is a potential biologic solution to the donor organ shortage. The immune response, consisting of hyperacute rejection, acute vascular rejection, and cellular rejection, currently prevents clinical xenotransplantation. Advances in the solution of these problems have been made using conventional immunosuppressive drugs and newer agents whose use is based on an understanding of important steps in xenoimmunity. The most exciting approaches use tools of molecular biology to create genetically engineered donors and to induce states of donor and recipient bone marrow chimerism and tolerance in xenogeneic organ recipients. The successful future strategy may use a combination of a genetically engineered donor and a chimeric recipient with or without nonspecific immunosuppressive drugs.