Risk analysis in patients bridged to transplantation

Characteristics and Outcomes of Patients Bridged to Cardiac Transplantation on Centrifugal Ventricular Assist Devices: A Case Series of the Early Experience of One Canadian Transplant Centre

BACKGROUND

Centrifugal ventricular assist devices (VADs) have been used successfully to bridge patients in cardiogenic shock to cardiac transplantation, though complications are frequent and often life-threatening.

PURPOSE

To describe characteristics and examine outcomes of patients bridged to cardiac transplantation on centrifugal VADs.

METHODS

A retrospective health record review was conducted on all adults over a 12 year period (N=20) placed on centrifugal VADs with the intent to bridge to cardiac transplantation at a major Canadian transplant centre.

RESULTS

Complications of VAD support necessitated removal of 12 patients from the transplant list; seven (35%) survived to cardiac transplantation. Of the seven recipients, five survived to discharge and four remain alive and well.

CONCLUSIONS

Bridging patients on centrifugal VADs to cardiac transplantation requires improvement, including maintaining patient stability during the period of early VAD institution, aggressively managing complications of VAD support, and consideration of long-term pulsatile devices. However, if patients survive to transplantation, good long-term outcomes are expected.

Changes in renal function after implantation of continuous-flow left ventricular assist devices

OBJECTIVES

The aim of this study was to determine renal outcomes after left ventricular assist device (LVAD) implantation.

BACKGROUND

Renal dysfunction before LVAD placement is frequent, and it is unclear whether it is due to primary renal disease or to poor perfusion.

METHODS

A retrospective single-center analysis was conducted in 83 consecutive patients implanted with HeartMate II continuous-flow LVADs (Thoratec Corp., Pleasanton, California). Calculated glomerular filtration rate (GFR) was assessed on admission and 1, 3, and 6 months after implantation. To define predictors for improvement in GFR, clinical variables were examined in patients with decreased renal function (GFR <60 ml/min/1.73 m(2)) before LVAD, surviving and dialysis-free at 1 month (n = 44).

RESULTS

GFR significantly increased from admission (53.2 ± 21.4 ml/min/1.73 m(2)) to 1 month after LVAD implantation (87.4 ± 27.9 ml/min/1.73 m(2)) (p < 0.0001). Subsequently, at 3 and 6 months, GFR remained significantly (p < 0.0001) above pre-LVAD values. Of the 51 patients with GFRs <60 ml/min/1.73 m(2) before LVAD surviving at 1 month, 34 (67%) improved to GFRs >60 ml/min/1.73 m(2). Univariate pre-operative predictors for improvement in renal function at 1 month included younger age (p = 0.049), GFR improvement with optimal medical therapy (p < 0.001), intra-aortic balloon pump use (p = 0.004), kidney length above 10 cm (p = 0.023), no treatment with angiotensin-converting enzyme inhibitors or angiotensin receptor blockers (p = 0.029), higher bilirubin (p = 0.002), higher Lietz-Miller score (p = 0.019), and atrial fibrillation (p = 0.007). Multivariate analysis indicated pre-operative improved GFR (slope = 0.5 U per unit improved; 95% confidence interval: 0.2 to 0.8; p = 0.003), atrial fibrillation (slope = 27; 95% confidence interval: 8 to 46; p = 0.006), and intra-aortic balloon pump use (slope = 14; 95% confidence interval: 2 to 26; p = 0.02) as independent predictors.

CONCLUSIONS

In most patients with end-stage heart failure considered for LVAD implantation, renal dysfunction is reversible and likely related to poor renal perfusion.

Early adverse events as predictors of 1-year mortality during mechanical circulatory support

BACKGROUND

Ventricular assist devices (VADs) provide effective treatment for end-stage heart failure; however, most patients experience > or =1 major adverse events (AEs) while on VAD support. Although early, non-fatal AEs may increase the risk of later death during VAD support, this relationship has not been established. Therefore, we sought to determine the impact on 1-year mortality of AEs occurring during the first 60 days of VAD support.

METHODS

A retrospective analysis was performed using prospectively collected data from a single-site database for patients aged > or =18 years receiving left ventricular or biventricular support during 1996 to 2008 and who survived >60 days on VAD support. Fourteen major classes of AEs occurring during this 60-day period were examined. One-year survival rates of patients with and without each major AE were compared.

RESULTS

The study included 163 patients (80% men; mean age, 49.5 years), of whom 87% were European American, 72% had left ventricular support, and 83% were bridge to transplant. The occurrence of renal failure, respiratory failure, bleeding events, and reoperations during the first 60 days after implantation significantly increased the risk of 1-year mortality. After controlling for gender, age, VAD type, and intention to treat, renal failure was the only major AE significantly associated with later mortality (hazard ratio, 2.96; p = .023).

CONCLUSIONS

Specific AEs, including renal failure, respiratory and bleeding events, and reoperations, significantly decrease longer-term survival. Renal failure conferred a 3-fold increased risk of 1-year mortality. Peri-operative management should focus on strategies to mitigate risk for renal failure in order to maximize later outcomes.

Outcome evaluation of the bridge-to-bridge concept in patients with cardiogenic shock

BACKGROUND

Patients with cardiogenic shock can be stabilized by percutaneous implantation of extracorporeal membrane oxygenation (ECMO). If weaning from ECMO is impossible, the implantation of a ventricular assist device (VAD) is required. Patients either go for recovery of myocardial function (bridge to recovery) or for heart transplantation (bridge to transplant).

METHODS

One hundred thirty-one patients were supported with ECMO between March 1995 and November 2005. Reasons for ECMO implantation were acute heart failure, acute or chronic heart failure, and postcardiotomy heart failure. In 28 patients, subsequent VAD implantation was necessary (bridge to bridge concept).

RESULTS

Fourteen bridge to bridge patients (50%) became long-time survivors with a mean follow-up of 39 months. Risk factors for mortality were status post-cardiopulmonary resuscitation and elevated lactate and bilirubin levels before VAD implantation. Complications after ECMO and VAD implantation were bleeding and thromboembolic events. The most common cause of death was multiorgan failure.

CONCLUSIONS

Bridge to bridge is a successful concept for selected patients with cardiogenic shock. During ECMO support, patients can be evaluated for comorbidities. For patients with a combination of risk factors (status post-cardiopulmonary resuscitation, elevated lactate levels, and impaired liver function), VAD implantation should be considered very carefully.

Predictors and Outcomes of Continuous Veno-venous Hemodialysis Use After Implantation of a Left Ventricular Assist Device

BACKGROUND

Post-operative renal failure is a common complication after left ventricular assist device (LVAD) implantation. This study was designed to evaluate predictors and outcomes of acute renal failure after LVAD insertion.

METHODS

Two-hundred one patients undergoing LVAD implantation at a single institution from June 1996 through April 2004 were retrospectively analyzed. Patients were categorized into 2 groups: those who required post-operative continuous veno-venous hemodialysis (CVVHD) (Group 1, n = 65, 32.3%) and those who did not (Group 2, n = 136, 67.7%). Independent predictors of post-operative renal failure requiring CVVHD were determined using multivariate logistic regression techniques.

RESULTS

Patients who had post-operative renal failure requiring CVVHD were older (53.7 +/- 12.9 vs 48.2 +/- 14.2 years, p = 0.009), had a higher incidence of intra-aortic balloon pump use (46.6% vs 26.2%, p = 0.006), and had a higher pre-operative mean LVAD score (5.8 +/- 3.5 vs 3.8 +/- 3.3, p = 0.001) than those without renal failure. LVAD score was the only independent predictor of post-operative renal failure requiring CVVHD (odds ratio = 1.226, p = 0.006). Sepsis rate was higher (33.3% vs 6.9%, p < 0.001) and bridge-to-transplantation rate was lower (52.4% vs 83.5%, p < 0.001) in Group 1 than in Group 2. Post-LVAD survival rates at 1, 3, 5 and 7 years for Group 1 and Group 2 were 43.2%, 39.1%, 34.7% and 34.7% vs 79.2%, 74.0%, 68.3% and 66.4%, respectively (log rank, p < 0.001).

CONCLUSIONS

Acute renal failure necessitating CVVHD remains a serious complication after LVAD and confers significant morbidity and mortality. Pre-operative evaluation of patient risk factors and optimization of peri-operative hemodynamics are of utmost importance to prevent this major complication.

Extensive Coagulation Monitoring in Patients After Implantation of the MicroMed Debakey Continuous Flow Axial Pump

Ventricular assist device (VAD) implantation is associated with impaired primary hemostasis and thromboembolic complications. Recently, a new generation of implantable continuous flow axial pumps was introduced into clinical application. To study the potential thrombogenic properties of this type of pump, we applied extensive platelet monitoring was applied. In our institution, 13 patients received the MicroMed DeBakey VAD as a bridge to transplantation. Routine coagulation tests (platelet count, activated partial thromboplastin time, prothrombin time, antithrombin III activity) and platelet function tests (whole blood aggregometry, thrombelastography, flow cytometry) were performed. No clinically relevant thromboembolic events were detected. No correlation was found between global function tests, platelet aggregation, and thrombelastography. No correlation was detected between platelet activation and hemolysis parameters. Platelet aggregation and coagulation index were significantly suppressed early after operation. A subsequent phase of hyper-aggregability, starting around day 6, suggested the initiation of antiaggregation therapy. Platelet activation markers were upregulated in the postoperative period but were returned to preoperative levels after initiation of aspirin. In contrast to routine coagulation monitoring, platelet function tests reflect in detail the coagulation status of blood pump recipients and the efficiency of antiaggregation therapy. Aspirin and dipyridamole therapy in addition to oral anticoagulation using phenprocoumon may contribute to platelet function and clot mechanics restoration and is, therefore, recommended for patients after VAD implantation.

Development of a database of patients supported by ventricular assist devices

An increase in the number of patients with end stage heart failure is leading to increased use of ventricular assist devices (VAD). However, sometimes the optimal time point for implantation of left ventricular or biventricular support remains unclear. Data analysis using an electronic database may help to make the decision making process more precise and thus improve outcome. However, it is not easy to find a balance between sufficient comprehensiveness of the data, which are selected from a huge amount of available information, and practicability of database maintenance and data analysis. We developed the Assist Database based on Access for Windows. The Assist Database consists of five main parts: (1) demographic and admission data, diagnosis, goal, and type of VAD; (2) preoperative period; (3) postoperative period up to 30 days; (4) follow-up period; and (5) statistical evaluation. The preoperative and postoperative parts include hemodynamic data; ventilatory support; laboratory results; results from echocardiographic, neurologic, pathologic, and other examinations; medication; and complications. The follow-up part documents readmissions, complications, and outcome. From April 1987 to October 2002, eight different types of VAD were implanted in 654 patients in our institution. Their data were retrospectively added to the Assist Database using medical records and different previously used electronic databases. Since the Assist Database came into routine use, it has been supplied daily with selected data of current patients. On the data entry level, the data arising from medical records are entered either manually via standard forms or automatically from other electronic documentation systems used in our hospital in routine patient care to collect laboratory results, demographic data, blood transfusion data, and operative data and from electronic patient charts via interfaces. The structure of the database is designed to facilitate the data analysis level. The database presented is one of three databases united to form a network. The structure of the Assist Database facilitates comprehensive, time saving data collection, which allows different online data analyses. These analyses may affect the decision making process and thus improve outcome. However, achieving a balance between the volume of available information, the time consumed, and the relevance of the data for further analysis remains difficult. The Assist Database should include information relevant for the decision making process and for the prediction of outcome. In particular, data collection should be focused on patients' preoperative condition and on postoperative organ function and quality of life. Further, different databases (for patients with congestive heart failure, assist device patients, and transplanted patients) should be unified to form a network to avoid the repeated collection of identical data, to save time, and to increase the quality of analysis. In the long-term, multicenter use of the Assist Database could be considered.

Patient selection for assist devices: bridge to transplant

Patients in severely progressed states of heart failure can be bridged to successful heart transplantation with mechanical assist devices. Experience has demonstrated that patient selection and timing of device implantation are crucial for obtaining acceptable results when using this expensive technology. The degree of irreversible secondary organ dysfunction before re-establishing adequate cardiac output determines the chance of reaching transplantation. Patients who recover during support from all sequelae of end stage heart failure have an excellent outcome after heart transplantation.