Patient selection for left ventricular assist device therapy

Update on ventricular assist device management in the ICU

PURPOSE OF REVIEW

Mechanical circulatory support has a progressively increasing impact in the treatment of heart failure. The results of mechanical circulatory support are limited not only by the severity of the disease, which necessitated initiation of support, but also by the serious device-related adverse events. Optimized patient selection, improved patient management, and advanced device technology are interdependent key factors that contributed to the recently improved outcomes. The aim of this article is to summarize the current experience in application of mechanical circulatory support, focusing on the ICU management.

RECENT FINDINGS

Management should aim to prevent rather than treat serious complications and adverse events. Timing of intervention, optimization of the preimplantation patient status, patient and device management to ensure optimal hemodynamics, infection prevention, nutritional support, careful anticoagulation, and vigilance for early recognition and prompt treatment of 'minor' events before progression into major complications are essential elements of successful treatment.

SUMMARY

Critical patient care is a valuable adjunct to successful application of mechanical circulatory support, but it cannot counterbalance a late intervention, neither can it be fruitful in treating irreversible organ damage. Current management includes careful application of treatment protocols adjusted to recent experience, and also individualized care by a specialized team.

Heparin-Induced Thrombocytopenia in Left Ventricular Assist Device Bridge-to-Transplant Patients

BACKGROUND

The presence of heparin-induced thrombocytopenia (HIT) increases the risk for thromboembolic events in ventricular assist device (VAD) patients undergoing transplantation. However, cardiopulmonary bypass with alternative anticoagulants is often complicated by bleeding. Owing to this concern, we compared outcomes of HIT-positive versus control bridge-to-transplantation VAD patients; both groups were reexposed to heparin for cardiopulmonary bypass during transplant.

METHODS

From February 2000 to January 2006, data were reviewed on 92 consecutive adult patients who underwent VAD placement as a bridge to transplantation. Patients in whom thrombocytopenia developed after heparin exposure were tested for HIT with an enzyme-linked immunosorbent assay for antiheparin/platelet factor-4 (HPF4) antibody (GTI Diagnostics, Waukesha, Wisconsin). During VAD support, heparin was avoided in HIT-positive patients, but all patients were reexposed to heparin during transplantation. Comparisons between HIT-positive and control patients for survival and freedom from thromboembolic events were determined using the Kaplan-Meier method and log-rank test. Continuous and categorical variables were compared using the Wilcoxon rank-sum and Student t test.

RESULTS

Twenty-four of the 92 patients (26.1%) were determined to be HIT positive by enzyme-linked immunosorbent assay. Survival to transplant was not different between the two groups. When compared with control patients, HIT-positive patients who were reexposed to heparin had a greater decrease in platelet counts immediately after transplant (postoperative days 1 to 4, p < 0.05). Despite this transient thrombocytopenia, there was no difference in posttransplant mortality or thromboembolism.

CONCLUSIONS

Heparin-induced thrombocytopenia-positive VAD patients did not experience increased thromboembolism or mortality after heparin reexposure. In light of the risks of using heparin alternatives, heparin reexposure is a safe management strategy for HIT-positive VAD patients.

Successful mechanical circulatory support as a bridge to transplantation

With the progression of congestive heart failure, therapeutic options become fewer, and cardiac transplantation is the final option. The use of a left ventricular assist device improves the survival rate and quality of life in patients on the waiting list for transplantation. A 64-year-old man was successfully maintained on mechanical circulatory support with a left ventricular assist device for 502 days, as a bridge to transplantation.

Left Ventricular Assist Device Therapy for End‐Stage Congestive Heart Failure: From REMATCH to the Future

Therapy for patients with end-stage cardiomyopathy continues to evolve, but clearly it must now involve left ventricular assist device therapy as either bridge-to-transplantation or destination therapy. Patients who are selected for left ventricular assist device support must be able to undergo the surgical implantation procedure safely and avoid common complications such as right heart failure. Adequate patient selection is essential and can typically be accomplished using simple hemodynamic measures. As left ventricular assist device technology evolves, pulsatile devices will likely be replaced by their newer axial flow counterparts, which offer decided advantages. In the future, therapy for end-stage heart failure will involve aggressive use of mechanical assist device therapy and, as more patients are supported with these devices and the technology improves, this will become a burgeoning field for cardiologists and cardiovascular surgeons.

Evaluation of the clinical effectiveness of the Ventricular Assist Device Program in the United Kingdom (EVAD UK)

BACKGROUND

The UK Government funds ventricular assist device (VAD) implantation as bridge to transplantation (BTT) at three centers. Results from this program have not been published.

METHODS

All 70 VAD implants for BTT, 71 inotrope-dependent and 179 non-VAD transplant candidates, accepted for transplantation between April 2002 and December 2004, were prospectively monitored for survival to transplantation, survival overall and quality of life.

RESULTS

Of the 70 VAD patients, 31 (44%) survived to heart transplantation, 4 (6%) were bridged to recovery and 5 remained on support at the end of the study. Thirty patients (43%) died while on support. Overall survival from VAD implant was 52% at 1 year. Ten percent of non-VAD inotrope-dependent patients and 9% of routine transplant candidates died while on the waiting list. For transplant recipients, 12-month post-operative survival was 84%, 85% and 84%, respectively, for VAD, inotrope-dependent and routine transplant candidates. VAD and non-VAD patients had similar post-transplant adverse event rates.

CONCLUSIONS

There was a role for VAD bridge to transplant for selected patients in the UK, despite the availability of an effective urgent transplant list. VAD patients who underwent transplantation had survival rates similar to other transplant candidates.

Importance of luxury flow for critically ill patients receiving a left ventricular assist system

The presence of a significant organ dysfunction does not immediately exclude patients from consideration for treatment with a left ventricular assist system (LVAS). However, in treating morbid circulatory shock patients with multiple organ failure, it is important to know the preoperative and postoperative factor or factors related to the recovery of the damaged organ function. In this study, we retrospectively analyzed patients receiving a LVAS at our institution and tried to determine the important factors related to the survival of patients with multisystem failure. Twenty-seven patients who underwent LVAS placement at Saitama Medical School Hospital between 1993 and 2003 were included in this study. The preoperative risk factors analyzed were renal dysfunction, respiratory dysfunction, hepatic dysfunction, the existence of active infection, and the combination of all four factors. As a postoperative factor, the pump flow index (mean LVAS pump flow during the first 2 weeks after LVAS surgery divided by the body surface area) was analyzed. None of the analyzed preoperative factors could predict survival after LVAS surgery, but a pump flow index of less than 2.5 l/min/m2 had a significant relationship with death after LVAS surgery. Further analysis revealed that all the patients with a pump flow index of 3.0 l/min/m2 or more could overcome preoperative organ dysfunction. Congestive heart failure patients with multisystem failure need luxury pump flow for successful LVAS surgery; this factor could be especially important in device selection and postoperative management.

Successful Salvage of Ventricular-Assist Devices in the Setting of Pump Pocket Infection

Implantable ventricular-assist devices (VADs) have been approved for use both as a bridge to heart transplantation and as a destination therapy. Rising numbers of patients are surviving with these devices for several years. However, infections of these foreign bodies are serious and frequent complications, often requiring removal of the implant, with serious health consequences. Given the increased use of VADs as life-preserving destination therapy, explantation of these devices in the face of infection is impractical. We evaluated and successfully treated 2 patients with VAD pocket infections referred by the cardiac surgery service at our institution using aggressive surgical and pharmacologic therapy, with the goal of preserving the VADs. However, this is still a largely unsolved dilemma requiring further exploration into prevention and treatment since these devastating infections will likely become a more frequent reconstructive challenge.

Hospital Costs for Left Ventricular Assist Devices for Destination Therapy: Lower Costs for Implantation in the Post-REMATCH Era

BACKGROUND

The use of left ventricular assist devices (LVADs) as an alternative to transplant, or destination therapy (end of life support), is an increasingly important option for patients with end-stage heart failure. Prior studies have examined hospital costs for LVAD implants performed during investigational studies (e.g., REMATCH), but none has been published since that trial was completed.

METHODS

We performed a retrospective analysis of 23 consecutive patients who had a HeartMate XVE pump implanted as destination therapy at 2 high-volume ventricular assist device implant centers after US Food and Drug Administration approval in October 2003. We evaluated survival to discharge during the implantation hospitalization, hospital length of stay, and hospital costs, and compared them with outcomes reported from the REMATCH (RM) trial.

RESULTS

All patients in this cohort implanted post-REMATCH (PRM) had class IV heart failure and were similar in age, gender, and nearly all other pre-implantation clinical measures to the RM subjects. Mean hospital costs for PRM patients were 40% lower than for RM patients when measured from implantation to discharge (dollar 128,084 vs dollar 210,187, p < 0.01). PRM patients who survived implantation hospitalization had 48% lower costs than those who did not survive (dollar 114,979 vs dollar 215,456, p < 0.01), a finding similar to the RM experience. PRM patients in this cohort were more likely to survive to discharge compared with RM patients (87.0% vs 67.3%, p = 0.09). Mean hospital length of stay was 25% lower in the PRM group (44 vs 33 days) but did not reach statistical significance (p = 0.50).

CONCLUSIONS

Outcomes with use of LVADs as destination therapy have improved in the post-REMATCH era, including significantly lower hospital costs as well as strong trends toward better survival to hospital discharge and shorter average length of stay.

Relationship Between Renal Function and Left Ventricular Assist Device Use

BACKGROUND

Poor renal function may affect outcomes after left ventricular assist device (LVAD) placement. Conversely, LVADs may optimize circulation and improve renal function.

METHODS

To assess the relationship between renal function and LVAD use, changes in creatinine clearances (CrCl, in mL/min) were assessed retrospectively in 220 patients who underwent LVAD placement. These patients were also divided into four groups based on CrCl quartiles (< 47, 48-68, 69-95, and > 95) and compared for outcomes post-LVAD placement.

RESULTS

Eighty-four patients died on LVAD support. Survival on LVAD was worse for patients with the worst baseline CrCl (42%, 52%, 63%, and 79% for 6 month and 26%, 34%, 47%, and 66% for 12 month survival for quartiles 1-4; both p < 0.01 for trend). Adjusting for other covariates, patients in the lowest CrCl quartile were at a higher risk of dying postimplant (odds ratio 1.95, 95% confidence interval 1.14-3.63). Paired sample analysis showed the following changes in CrCl: preoperative to week 1, 77.0 +/- 46.6 to 92.1 +/- 51.1 (p < 0.01; n = 202), week 1 to 2, 89.4 +/- 49.2 to 95.2 +/- 52.4 (p = 0.01, n = 171), week 2 to 3, 107.5 +/- 58.1 to 113.7 +/- 66.1 (p = 0.16, n = 74), and week 3 to 4, 111.1 +/- 56.6 to 110.5 +/- 56.8 (p = 0.87, n = 60). For the 60 patients with baseline CrCl less than 50, CrCl increased from 36.7 +/- 9.2 to 60.1 +/- 35.5 (p < 0.01; n = 55 pairs) from preimplant to week 1. In 37 of these patients (62%) on intraaortic balloon pump support preimplant, CrCl increased from 38.4 +/- 8.2 to 67.9 +/- 40.3 mL/minute (p < 0.01) during week 1 postimplant. Recovery of renal function to CrCl greater than 50 was associated with a trend towards better 30-day survival (84% vs 66%, p = 0.09).

CONCLUSIONS

Baseline poor renal function is associated with worse outcomes after LVAD implantation. However, renal function improves substantially and rapidly in post-LVAD survivors and is associated with improved outcomes. These data underscore the importance of careful patient selection for LVAD therapy.

Right ventricular failure after left ventricular assist device implantation: the need for an implantable right ventricular assist device

Right ventricular failure after implantation of a left ventricular assist device is an unremitting problem. Consideration of portal circulation is important for reversing liver dysfunction and preventing multiple organ failure after left ventricular assist device implantation. To achieve these objectives, it is imperative to maintain the central venous pressure as low as possible. A more positive application of right ventricular assistance is recommended. Implantable pulsatile left ventricular assist devices cannot be used as a right ventricular assist device because of their structure and device size. To improve future prospects, it is necessary to develop an implantable right ventricular assist device based on a rotary blood pump.

Managing the Post-Left Ventricular Assist Device Patient

The implantation of ventricular assist devices allows the opportunity for patients with intractable heart failure to have improved quality and quantity of life. The devices may be implanted after failed attempts to wean from bypass, as a bridge to transplantation, or as destination therapy. Key issues following the implantation of assist devices include the prevention of right ventricular failure, appropriate pharmacologic management, prevention and management of infection, and detection and treatment of device dysfunction.

Implantable left ventricular assist devices

The first bridge to transplant with a left ventricular assist device (LVAD) was preformed over 20 years ago. Since that time, the devices have continued to evolve and now patients are being supported with devices as an alternative to transplantation. The primary indication of end-stage heart failure remains the same but increased knowledge about patient selection, the timing of implant, and patient management have contributed to improved outcomes with decreasing adverse events. Multiorgan failure, right ventricular failure, bleeding, infection, thromboembolism, and device malfunction continue to be the most serious threats to long-term survival in these patients. Despite that, patients who do well are now able to be discharged from the hospital and resume relatively normal lives with the devices. The article reviews 3 of the most widely used LVADs for bridge to transplant therapy: the Thoratec; HeartMate vented electric; and the Novacor Left Ventricular Assist System. Indications, mechanism of operation, clinical problems, and out-of-hospital preparation are outlined.

Insights from Continued Use of a Novacor Left Ventricular Assist System for a Period of 6 Years

We report a patient supported with the Novacor Left Ventricular Assist System for more than 6 years and chronicle his progress as an illustration of the clinical, practical, and emotional challenges of this therapy and the benefits of an intervention that can return a morbidly ill patient to an essentially normal lifestyle. This experience underlines the importance of patient selection, optimal timing of intervention, and the potential impact of psychologic issues on outcome.

Development of implantable right ventricular assist device

Implantable ventricular assist devices (VADs) are indicated for long waiting periods before transplantation and also as a destination therapy. Meanwhile, right ventricular failure (RVF) is one of the four major complications observed in patients after left VAD (LVAD) implantation, with an incidence of approximately 20%. Preoperative prediction of the complication remains difficult, and the mortality is very high. To date, no implantable right VAD (RVAD) is available for the clinical situation. The possibility of realizing an implantable RVAD with Gyro centrifugal pump (PI-710 pump) was investigated. Eleven chronic animal experiments with LVAD and RVAD implantation were performed. Right heart bypass was established between right outflow and pulmonary trunk, and the pump was implanted in the preperitoneal space. The anatomic fit was good. The mean term of the experiments was 59 days, with excellent pump performance. Stable pulmonary hemodynamics and respiratory function were maintained during all of the experimental terms. No specific abnormal histologic findings of the lung were confirmed; however, tunica media hypertrophy was recognized in some cases. The PI-710 pump is feasible as a clinically implantable RVAD, but further study of histologic and pulmonary vascular changes after RVAD implantation is needed.

Imaging of Left Ventricular Assist Devices

Left ventricular assist devices are used as a bridge to recovery, a bridge to transplant, or a permanent alternative to cardiac transplant. This exhibit demonstrates the imaging appearance of commonly used left ventricular assist devices and their complications.

Left ventricular assist devices: evolving devices and indications for use in ischemic heart disease

PURPOSE OF REVIEW

The mortality with end-stage heart failure is extremely high, especially when patients become refractory to conventional medical therapy and require frequent hospitalization. Ischemic heart disease remains the primary cause of advanced heart failure. Mechanical pumps or devices have been developed called ventricular assist devices and are being used to support an increasing number of patients with refractory heart failure.

RECENT FINDINGS

The use of ventricular assist devices has evolved from initially only support of patients unable to be weaned from a heart-lung machine after cardiac surgery to use now as a bridge to a heart transplant, including patients with acute myocardial infarction and shock and severe pulmonary hypertension. More recently, they have been proven as a definitive alternative for patients not eligible for heart transplantation. There are new devices being examined in clinical trials, including a change from pusher-plate to devices with axial flow technology that are much smaller and easier to implant. Outcomes with their use are improving rapidly as the devices become more reliable and more is learned about the importance of candidate selection.

SUMMARY

This review describes current indications for the use of these devices, the types of pumps now available, criteria for initiating ventricular assist device support, complications of their use, and new applications such as a platform for stem cell therapy for treatment of end-stage heart failure.

Patient Selection for Left Ventricular Assist Devices

The use of mechanical support as a bridge to cardiac transplant has become the standard of care in many cardiac transplant centers. This therapy has been shown to increase survival and improve morbidity in carefully selected patients waiting for heart transplantation. With approximately 30000 patients being listed worldwide for transplant every year and only 3500 transplantations performed annually, alternative strategies need to be developed to minimize morbidity and mortality in this high-risk population. Patient selection remains the primary determinant of success with left ventricular assist device (LVAD) therapy. This article will review both the cardiac and extracardiac considerations needed in the assessment of patient suitability for LVAD support as a bridge to transplantation.