Mechanical circulatory support and cardiac transplantation

Short- and long-term mechanical cardiac assistance

With the increase in high risk patients undergoing cardiac surgery and the substantial mortality among patients waiting for cardiac transplantation, the need for mechanical circulatory support is growing. Several devices are currently available, ranging from the intra-aortic balloon pump to fully implantable ventricular assist devices. Each system has its own features, and proper patient selection as well as the timing of implantation is sometimes difficult. Algorithms for stepwise management in subgroups of patients remain controversial and the concepts of weaning patients after myocardial recovery during mechanical circulatory support need further evaluation for their long-term effects. Future identification of valuable prognostic and risk factors may help in decision-making and allow for improved survival of these often very ill patients. In this report we review the concepts of mechanical circulatory support at our institution with emphasis on a detailed overview of technical features of extracorporeal life support.

Development and current clinical application of ventricular assist devices in China

Heart failure has become one of the biggest threats to human health. Transplantation remains the most effective therapy for heart failure, but because of the shortage of donors, it cannot meet the demand. Ventricular assist devices (VADs) were developed to treat heart failure, and have now been clinically applied worldwide. As the country with the largest population, China is also facing the threat of heart failure. However, the development of VADs in China is very slow and is seldom discussed. This paper first talks about the background for VAD development in China. Then several home-developed VADs in China are introduced. The current clinical application status of VADs in China is also presented. Finally the challenge and opportunity for VAD development in China are discussed.

Asynchronous Pumping of a Pulsatile Ventricular Assist Device in a Pediatric Anastomosis Model

BACKGROUND

Both pulsatile and continuous flow ventricular assist devices are being developed for pediatric congenital heart defect patients. Pulsatile devices are often operated asynchronously with the heart in either an "automatic" or a fixed beat rate mode. However, most studies have only investigated synchronized ejection.

METHODS

A previously validated viscoelastic blood solver is used to investigate the parameters of pulsatility, power loss, and graft failure in a pediatric aortic anastomosis model.

RESULTS

Pulsatility was highest with synchronized flow and lowest at a 90° phase shift. Power loss decreased at 90° and 180° phase shifts but increased at a 270° phase shift. Similar regions of potential intimal hyperplasia and graft failure were seen in all cases but with phase-shifted ejection leading to higher wall shear stress on the anastomotic floor and oscillatory shear index on the anastomotic toe.

CONCLUSION

The ranges of pulsatility and hemodynamics that can result clinically using asynchronous pulsatile devices were investigated in a pediatric anastomosis model. These results, along with the different postoperative benefits of pump modulation, can be used to design an optimal weaning protocol.

Is Diabetes Mellitus a Risk Factor for Poor Outcomes after Left Ventricular Assist Device Placement?

Diabetes mellitus is associated with adverse outcomes in patients with cardiovascular diseases, including heart failure. Left ventricular assist devices (LVADs) are increasingly used as life-saving therapy for advanced heart failure. The effects of pre-LVAD diabetes on long-term outcomes after LVAD implantation are not well understood. In this study, we retrospectively evaluated the effect of existing diabetes on post-LVAD outcomes. Data on 288 LVAD recipients from 2006 through 2013 were reviewed. Patients were stratified in accordance with their histories of diabetes. Baseline demographic, laboratory, hemodynamic, and echocardiographic information before LVAD placement were reviewed, together with the post-LVAD incidence of major adverse outcomes. Kaplan-Meier analysis and Cox regression analysis were performed. Our cohort comprised 122 patients with diabetes and 166 patients without. The mean glycosylated hemoglobin A_1c level in the diabetes group was 7.4% ± 1.6%. Diabetic patients at baseline had a more adverse medical profile than did nondiabetic patients. There were no differences in major outcomes between the 2 groups other than a higher incidence of hemolysis in the diabetes group: 12 (10%) vs 5 (3%); P=0.02. There was no difference in survival outcomes between the groups. Diabetic patients did not have worse survival or more adverse outcomes than did nondiabetic patients in this study, perhaps because of improved diabetes control, or improvement in biochemical derangements after normalization of cardiac output with LVAD therapy. A diagnosis of diabetes was an independent predictor of hemolysis. Further studies to evaluate the link between hemolysis and diabetes are indicated.

Mechanical circulatory support improves diabetic control in patients with advanced heart failure

AIMS

Left ventricular assist devices (LVADs) are increasingly being used as life-saving therapy for end-stage advanced heart failure. Diabetes is prevalent in advanced heart failure patients. In this study, we sought to investigate the effects of mechanical circulatory support on diabetic parameters with LVAD implantation.

METHODS AND RESULTS

In this retrospective study, data on 244 LVAD recipients between 2006 and 2013 were reviewed. Patients without history of diabetes, death within the first 3 months after LVAD implantation, heart transplantation after LVAD, or LVAD explantation were excluded from the study. Baseline demographic, laboratory, and echocardiographic information prior to LVAD placement and 6-month follow-up were obtained. Laboratory values indicative of diabetic control were found to improve significantly at 6 months post-LVAD implantation (glycated haemoglobin, 7.2 vs. 6.1%, P < 0.0001; serum fasting glucose, 141 vs. 122 mg/dL, P = 0.003; mean daily insulin dose, 30 vs. 24 IU/day, P = 0.02). Additionally, the use of oral hypoglycaemic medication was successfully discontinued in six patients at 6 months post-LVAD implantation.

CONCLUSIONS

Long-term LVAD therapy is associated with improvement in diabetic control which is probabvly due to improvements in cardiac output and normalization of biochemical derangements resulting from diabetes.

HeartMate® II left ventricular assist device: a new device for advanced heart failure

Since the initial use of artificial heart devices decades ago, advances in technology have yielded new artificial heart devices that can finally achieve the goal of providing life-saving treatment and good quality of life in terminally ill patients with heart failure. The HeartMate II left ventricular assist device is a new generation of device that is small, quiet and relatively easy to implant. A pilot study in the USA recently completed enrollment, and the pivotal trial is now underway to study this device in patients who are awaiting transplant and patients who are not candidates for transplant. To date, the results look promising that this device may be widely applicable to patients who have heart failure that do not respond to conventional treatments.

Currently available ventricular-assist devices: capabilities, limitations and future perspectives

The continuous progress in ventricular-assist device (VAD) technology and the management of patients with VADs has broadened the treatment options for end-stage heart failure patients. The available line-up of clinical devices provides the current optimal therapies to meet the specific needs of each patient. The extended durability, safety, efficacy and improved quality of life of the patients provides sufficient proof for the VAD to be a likely alternative therapy to heart transplantation. The sequential progress from the first-, to the second- and to the third-generation VAD technology is expected to bring increasing benefits to clinical outcomes. This article reviews the current status, capabilities, limitations and future perspectives of currently available VADs by generally classifying them via support duration, alignment of pump devices and via pulsatile or nonpulsatile mode of perfusion. Furthermore, the future direction of research and development for next-generation VADs is presented based on the lessons learned from currently available VADs.

How should I treat an unusual referral for heart transplantation?

BACKGROUND

A 55 years old man was referred for cardiac transplantation because of intractable angina and fatigue.

INVESTIGATION

Physical examination, laboratory test, echocardiography, exercise ECG, MRI and coronary arteriography.

DIAGNOSIS

Multiple coronary artery fistulae.

MANAGEMENT

Beta-blockers, angiotensin-converting enzyme inhibitor ICD.

Thyroid hormone and chronically unloaded hearts

The heart is subjected to chronic mechanical unloading during prolonged spaceflight and microgravity. The heart in patients with end-stage heart failure is also unloaded in prolonged duration after left ventricular assist devices (LVAD) are implanted. Heterotopic heart transplantation in rats is an established model of chronic cardiac unloading, and has been used to investigate the effects of chronic cardiac unloading on the heart. Observations that have been found using this experimental model are as follow. Chronic cardiac unloading induces time-dependent depressions of Ca2+ handling and myocyte contractility, which are associated with the shift of myosin heavy chain (MHC) isozymes and altered expressions of Ca2+ cycling-related proteins. Treatment with the physiological treatment dose of thyroid hormone restores the expression levels of Ca2+ cycling-related proteins, Ca2+ handling, and contractile function of cardiac myocytes in chronically unloaded hearts. Although future studies are required to determine precise mechanisms of the beneficial effects of thyroid hormone on chronically unloaded hearts, these observations may have clinical implications in the future for chronic cardiac unloading in the space industry as well as in the treatment of patients with end-stage heart failure supported by LVAD.

Guidelines for heart transplantation

Based on the changes in the field of heart transplantation and the treatment and prognosis of patients with heart failure, these updated guidelines were composed by a committee under the supervision of both the Netherlands Society of Cardiology and the Netherlands Association for Cardiothoracic surgery (NVVC and NVT).THE INDICATION FOR HEART TRANSPLANTATION IS DEFINED AS: 'End-stage heart disease not remediable by more conservative measures'.CONTRAINDICATIONS ARE: irreversible pulmonary hypertension/elevated pulmonary vascular resistance; active systemic infection; active malignancy or history of malignancy with probability of recurrence; inability to comply with complex medical regimen; severe peripheral or cerebrovascular disease and irreversible dysfunction of another organ, including diseases that may limit prognosis after heart transplantation.Considering the difficulties in defining end-stage heart failure, estimating prognosis in the individual patient and the continuing evolution of available therapies, the present criteria are broadly defined. The final acceptance is done by the transplant team which has extensive knowledge of the treatment of patients with advanced heart failure on the one hand and thorough experience with heart transplantation and mechanical circulatory support on the other hand. (Neth Heart J 2008;16:79-87.).

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.

Extracorporeal Membrane Oxygenation Hybrid With Various Ventricular Assist Devices as Double Bridge to Heart Transplantation

Ventricular assist devices (VAD) have benefitted patients with end-stage heart failure as a bridge to heart transplantation (HTx). We present our experience with HTx after an extracorporeal membrane oxygenation (ECMO) hybrid with various ventricular assist devices (VAD). From May 1996 to December 2003, mechanical circulatory support with a Biopump VAD was performed in eight patients, HeartMate left VAD in eight patients, and Thoratec VAD in eight patients. Before VAD implantation, 19 patients maintained their circulation with ECMO. Half of the 24 patients were implanted with VAD to await a suitable donor for HTx. We observed that half of the patients supported by ECMO hybrid with various VAD awaited a suitable donor for HTx. In our experience, we recommend the application of ECMO for short-term support within 1 week and the Biopump VAD, Thoractec VAD, or HeartMate VAD for medium-term or long-term support as a bridge to HTx.

Development of mechanical heart devices

BACKGROUND

A succinct, historical review of developments in mechanical devices to assist the failing heart is provided.

METHODS

A number of methods of mechanical devices to assist the failing heart are briefly assessed. Personal experimental and clinical studies of devices developed over several decades are presented.

RESULTS

Findings and data of devices used in assisting the failing heart, including those developed by the author, are analyzed.

CONCLUSIONS

On the basis of this review, the left ventricular assist device is believed to be the most effective. There is also reason to believe that the axial flow system has considerable advantages. This form of therapy has potentially great value for permanent use in some patients with intractable heart failure.

Short-term in vivo studies of surface thrombosis in a left ventricular assist system

Thrombosis continues to be a major adverse and at times fatal event in patients with left ventricular assist systems (LVAS). To assess acute thrombosis in an LVAS, multiscale analysis of surface thrombosis was performed on LVAS blood sacs retrieved after implantation in seven calves for 3 days. Two study groups were evaluated: One group was given heparin and warfarin sodium throughout the study; the second received no postoperative anticoagulation. On explantation, the blood sacs were examined for macroscopic thrombi; microscale thrombosis was assessed with the use of scanning electron microscopy. Macroscopic thrombi about 1 mm in diameter were seen in all sacs from both groups. Although macroscopic thrombi occurred in all sac regions, scanning electron microscopy revealed differences in microscale topography between the port regions and the other sac regions. The primary structure was spherical particles approximately 400 nm in diameter, found to occur at a lower density in the ports. In contrast, the highest densities of proteinaceous rough topography and fibrillar structures consistent with fibrin clot were seen in the port regions. The density distribution of these structures was different in the eight sac regions, and anticoagulation therapy appeared to have no effect on surface thrombosis in these short-term LVAS implants.

Coronary artery bypass grafting in patients with left ventricular dysfunction

BACKGROUND

Coronary artery bypass grafting surgery (CABG) remains a challenge for patients with coronary artery disease and left ventricular (LV) dysfunction. The aim of this study was to evaluate the result of CABG in patients with LV dysfunction.

METHODS

Medical records of 1,847 patients who underwent primary, isolated CABG at Taipei Veterans General Hospital from January 1, 1991 to December 31, 2002, were reviewed. The mortality rate associated with clinical and operative variables was compared between patients with LV ejection fraction (LVEF) > or = 35% and patients with LVEF < 35%.

RESULTS

Patients with LVEF < 35% had more episodes of myocardial infarction (57.5% vs 28.9%, p < 0.001) and history of congestive heart failure (18.1% vs 3.2%, p < 0.001), higher New York Heart Association (NYHA) class, and higher angina class. Longer cardiopulmonary bypass time (147 +/- 44 minutes vs 137 +/- 40 minutes, p < 0.001) but fewer left internal mammary artery (LIMA) grafts (46.8% vs 65.7%, p < 0.001) were used in patients with LVEF < 35%. Patients with LVEF < 35% had significantly higher hospital mortality (6.6% vs 2.2%, p < 0.001), higher major morbidity (23.3% vs 16.1%, p < 0.01), and longer hospital stay (25 +/- 23 days vs 21 +/- 16 days, p < 0.01).

CONCLUSION

Although patients with LV dysfunction had higher mortality and morbidity, CABG could be done in these high-risk patients with acceptable results.

Multiscale analysis of surface thrombosis in vivo in a left ventricular assist system

Thrombosis limits the success of ventricular assist devices as the demand for alternatives to heart transplants is increasing. This study mapped the occurrence of thrombosis in a left ventricular assist system (LVAS) to better understand the biologic response to these devices. Nine calves divided into two groups were implanted with LVAS for 28 to 30 days. One group was anticoagulated, whereas the second group received no long-term anticoagulation. The blood-contacting poly(urethane urea) surfaces of blood sacs in the LVAS were examined for macroscopic thrombi upon retrieval. The sac was partitioned into eight sections and imaged for thrombi by scanning electron microscopy. No difference in thrombosis was observed macroscopically between the groups. Anticoagulation appeared to result in reduction of platelet-like structures, but the presence of fibrin-like structures remained similar between groups. Regional differences correlating with high and low shear stress regions were observed. At the macroscale, fewer thrombi were recorded in the high shear stress ports. At the microscale, features resembling fibrin were observed primarily in the ports and platelet-like features were common in lower shear stress regions. These variations in thrombosis with anticoagulation and location are likely due to varied fluid dynamics within the LVAS blood sac.

Canadian Cardiovascular Society consensus conference recommendations on heart failure 2006: diagnosis and management

Heart failure remains a common diagnosis, especially in older individuals. It continues to be associated with significant morbidity and mortality, but major advances in both diagnosis and management have occurred and will continue to improve symptoms and other outcomes in patients. The Canadian Cardiovascular Society published its first consensus conference recommendations on the diagnosis and management of heart failure in 1994, followed by two brief updates, and reconvened this consensus conference to provide a comprehensive review of current knowledge and management strategies. New clinical trial evidence and meta-analyses were critically reviewed by a multidisciplinary primary panel who developed both recommendations and practical tips, which were reviewed by a secondary panel. The resulting document is intended to provide practical advice for specialists, family physicians, nurses, pharmacists and others who are involved in the care of heart failure patients. Management of heart failure begins with an accurate diagnosis, and requires rational combination drug therapy, individualization of care for each patient (based on their symptoms, clinical presentation and disease severity), appropriate mechanical interventions including revascularization and devices, collaborative efforts among health care professionals, and education and cooperation of the patient and their immediate caregivers. The goal is to translate best evidence-based therapies into clinical practice with a measureable impact on the health of heart failure patients in Canada.

Effect of Diabetes on Short- and Long-term Outcomes After Left Ventricular Assist Device Implantation

BACKGROUND

Diabetes mellitus (DM) is a frequent co-morbidity in patients with congestive heart failure (CHF). Implantation of LVADs is an acceptable option for diabetic patients with end-stage heart failure, yet no previous study has specifically examined the clinical outcomes of this patient population.

METHODS

A retrospective analysis was performed on all patients who underwent LVAD insertion at a single institution from June 17, 1996 to April 14, 2004. Patients were divided into 2 groups: diabetics (DM) and non-diabetics (NDM). The groups were compared with regard to demographics, etiology of heart failure, body mass index (BMI), intensive care unit (ICU) stay, early mortality (< or =30 days), bridge-to-transplantation rate and post-LVAD and post-transplant survival.

RESULTS

Two hundred one patients were identified. Of these, 49 (24.4%) had DM. Compared with the NDM group, DM patients had a higher mean body mass index (30.1 +/- 6.0 vs 26.1 +/- 4.8, p < 0.001) and a higher proportion of hypertension (57.4% vs 19.7%, p < 0.001). Although post-LVAD survival was similar, post-transplant survival in DM patients was significantly lower compared with NDM patients, with 1-, 3-, 5- and 7-year actuarial survival rates of 86.9%, 71.0%, 56.5% and 56.5% vs 90.5%, 88.4%, 83.0% and 80.7% (p = 0.020), respectively.

CONCLUSIONS

Carefully selected diabetic patients can be successfully bridged to transplantation using LVADs with comparable outcomes to non-diabetic patients. Reasons for diminished post-transplant survival in this cohort are unclear and necessitate the conductance of multi-institutional studies to evaluate outcomes.

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.

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.

Numerical and experimental analysis of an axial flow left ventricular assist device: the influence of the diffuser on overall pump performance

Thousands of adult cardiac failure patients may benefit from the availability of an effective, long-term ventricular assist device (VAD). We have developed a fully implantable, axial flow VAD (LEV-VAD) with a magnetically levitated impeller as a viable option for these patients. This pump's streamlined and unobstructed blood flow path provides its unique design and facilitates continuous washing of all surfaces contacting blood. One internal fluid contacting region, the diffuser, is extremely important to the pump's ability to produce adequate pressure but is challenging to manufacture, depending on the complex blade geometries. This study examines the influence of the diffuser on the overall LEV-VAD performance. A combination of theoretical analyses, computational fluid (CFD) simulations, and experimental testing was performed for three different diffuser models: six-bladed, three-bladed, and no-blade configuration. The diffuser configurations were computationally and experimentally investigated for flow rates of 2-10 L/min at rotational speeds of 5000-8000 rpm. For these operating conditions, CFD simulations predicted the LEV-VAD to deliver physiologic pressures with hydraulic efficiencies of 15-32%. These numerical performance results generally agreed within 10% of the experimental measurements over the entire range of rotational speeds tested. Maximum scalar stress levels were estimated to be 450 Pa for 6 L/min at 8000 rpm along the blade tip surface of the impeller. Streakline analysis demonstrated maximum fluid residence times of 200 ms with a majority of particles exiting the pump in 80 ms. Axial fluid forces remained well within counter force generation capabilities of the magnetic suspension design. The no-bladed configuration generated an unacceptable hydraulic performance. The six-diffuser-blade model produced a flow rate of 6 L/min against 100 mm Hg for 6000 rpm rotational speed, while the three-diffuser-blade model produced the same flow rate and pressure rise for a rotational speed of 6500 rpm. The three-bladed diffuser configuration was selected over the six-bladed, requiring only an incremental adjustment in revolution per minute to compensate for and ease manufacturing constraints. The acceptable results of the computational simulations and experimental testing encourage final prototype manufacturing for acute and chronic animal studies.

Computational Design and Experimental Testing of a Novel Axial Flow LVAD

Thousands of cardiac failure patients per year in the United States could benefit from long-term mechanical circulatory support as destination therapy. To provide an improvement over currently available devices, we have designed a fully implantable axial-flow ventricular assist device with a magnetically levitated impeller (LEV-VAD). In contrast to currently available devices, the LEV-VAD has an unobstructed blood flow path and no secondary flow regions, generating substantially less retrograde and stagnant flow. The pump design included the extensive use of conventional pump design equations and computational fluid dynamics (CFD) modeling for predicting pressure-flow curves, hydraulic efficiencies, scalar fluid stress levels, exposure times to such stress, and axial fluid forces exerted on the impeller for the suspension design. Flow performance testing was completed on a plastic prototype of the LEV-VAD for comparison with the CFD predictions. Animal fit trials were completed to determine optimum pump location and cannulae configuration for future acute and long-term animal implantations, providing additional insight into the LEV-VAD configuration and implantability. Per the CFD results, the LEV-VAD produces 6 l/min and 100 mm Hg at a rotational speed of approximately 6300 rpm for steady flow conditions. The pressure-flow performance predictions demonstrated the VAD's ability to deliver adequate flow over physiologic pressures for reasonable rotational speeds with best efficiency points ranging from 25% to 30%. The CFD numerical estimations generally agree within 10% of the experimental measurements over the entire range of rotational speeds tested. Animal fit trials revealed that the LEV-VAD's size and configuration were adequate, requiring no alterations to cannulae configurations for future animal testing. These acceptable performance results for LEV-VAD design support proceeding with manufacturing of a prototype for extensive mock loop and initial acute animal testing.

Hepatocyte Growth Factor Delivered by Ultrasound-Mediated Destruction of Microbubbles Induces Proliferation of Cardiomyocytes and Amelioration of Left Ventricular Contractile Function in Doxorubicin-Induced Cardiomyopathy

At present, there is no curative strategy for advanced cardiomyopathy except for cardiac transplantation, which is not easily performed, mainly due to a shortage of donors. It has been reported that myocardial progenitor cells exist even in the postnatal heart, suggesting that myocardial progenitor cells could proliferate under some situations and might improve cardiac function in cardiomyopathy-induced hearts. In this study, recombinant human hepatocyte growth factor (rhHGF) was delivered using ultrasound-mediated destruction of microbubbles (UMDM) into the cardiomyopathy-induced heart by doxorubicin (20 mg/kg). Intravenous injection of rhHGF (IV-rhHGF) alone or UMDM alone failed to improve the morphology or the function of the cardiomyopathy-induced heart, but (IV-rhHGF + UMDM) treatment significantly improved the heart morphologically and functionally, and repetitive treatments of (IV-rhHGF + UMDM) enhanced the effects. The number of bromodeoxy-uridine-positive cardiomyocytes significantly increased in the (IV-rhHGF + UMDM)-treated hearts compared with the untreated hearts. Moreover, Sca-1+ myocardial progenitor cells express c-Met, a receptor for HGF. These results suggest that (IV-rhHGF + UMDM) treatment could morphologically and functionally improve the heart in the case of doxorubicin-induced cardiomyopathy through the proliferation of the myocardial progenitor cells.

Platelet activation markers in patients with heart assist device

Clinical use of heart assist devices is often associated with thromboembolic complications. We hypothesized that platelets may be activated in patients receiving assist devices and examined expression of the platelet activation markers CD62, CD63, and thrombospondin using flow cytometry in eight patients with Novacor left ventricular assist system (LVAS) or Berlin Heart. Patients with end-stage heart failure had elevated expression of platelet activation markers before insertion of the assist device. While CD62 (P < 0.05) and thrombospondin expression (n.s.) decreased by the 14th postoperative day, the CD63 expression remained elevated (n.s.). A good correlation was found between CD62 and thrombospondin expression (r = 0.72). Bleeding time ex vivo indicated platelet dysfunction during the first 4 weeks after implantation. No relation between expression of platelet activation markers and bleeding time ex vivo were found. In conclusion, expression of the platelet activation markers CD62, CD63, and thrombospondin is increased in patients with end-stage heart failure before device placement and shows prolonged elevation during the assist period. Future studies in larger patient populations are necessary to identify new and specific markers of platelet activation in this clinical setting.

Risk factor screening scale to optimize treatment for potential heart transplant candidates under extracorporeal membrane oxygenation

We developed a risk factor-scaling score (RFSS) to select which patients supported by extracorporeal membrane oxygenation (ECMO) were suitable for ventricular assist device (VAD) implantation or heart transplantation (HTx). A total of 78 patients supported with ECMO for more than 48 h due to cardiac origin were included in this study. Patients were categorized into two groups based on the outcomes: the poor outcome group (n = 33) consisted of for those who later died or were later excluded from VAD or HTx; the favorable outcome group (n = 45) consisted of those who were weaned off ECMO finally and survived or were deemed suitable candidates for VAD or HTx. Seven risk factors were significant according to univariate analyses. Based on the regression coefficients of multivariate analysis, the RFSS was developed: (lung dysfunction x 7) + (systemic infection x 3) + (peak lactate > 3 mmole/L x 3) + (kidney dysfunction x 2) + (creatine kinase > 10,000 U/L x 1). Patients with an RFSS of 7 or more were be allocated to the poor outcome group. The RFSS was validated by another group of 30 patients with good correlation. The RFSS provides a way to predict which ECMO-supported patients are suitable candidates for VAD implantation or HTx.

Biventricular Support With the Jarvik 2000 Ventricular Assist Device in a Calf Model of Pulmonary Hypertension

The Jarvik 2000 ventricular assist device (VAD) is clinically efficacious for treating end-stage left ventricular failure. Because simultaneous right ventricular support is also occasionally necessary, we developed a biventricular Jarvik 2000 technique and tested it in a calf model. One VAD was implanted in the left ventricle with outflow-graft anastomosis to the descending aorta. The other VAD was implanted in the right ventricle with outflow-graft anastomosis to the pulmonary artery. Throughout the 30 day study, hemodynamic values were continuously monitored. On day 30, both pumps were evaluated at different speeds, under various hemodynamic conditions. By gradually occluding the pulmonary artery proximally or distally, we simulated varying degrees of high pulmonary vascular resistance, right ventricular hypertension, global heart failure, or ventricular fibrillation. The two VADs maintained biventricular support even during pulmonary artery occlusion and ventricular fibrillation, yielding a cardiac output of 3-11 L/min, left ventricular end-diastolic pressure of 11-24 mm Hg, and central venous pressure of 9-25 mm Hg. End-organ function was unimpaired, and no major adverse events occurred. The dual VADs offered safe, effective biventricular assistance in the calf. Additional studies are needed to assess the effects of lowered pulse pressure upon the pulmonary circulation and to develop a single pump speed controller.

Therapeutic left ventricular assist device and apheresis on dilated cardiomyopathy

Pathogenesis and therapies of dilated cardiomyopathy (DCM) have been discussed for a long time, but both of the ultimate answers are still unknown. In the last decade, the pathogenic role of immunological factors, such as cardiac autoimmune antibodies and cytokines, have been discussed attentively. This has led to one possible new therapy, immunoadsorption, which removes antibodies, and it has made a remarkable effect. However, there are other factors to remove. For the removal of cytokines and neurohormones, the most effective method is hemofiltration (HF). Also, double-filtration plasmapheresis (DFPP) removes immunoglobulin as well as low-density lipoprotein (LDL) and coagulation factors that may improve blood circulation, including the coronary arteries. Therefore, to eliminate all deteriorative factors, both apheresis therapies, HF and DFPP, should be performed. Due to the shortage of donor hearts, left ventricular assist systems (LVAD) have been used as a bridge to transplantation. It has now been reported that the total unloading of the left ventricle does not only maintain, but also recovers, the cardiac function, even from end-stage heart failure. However, the patients who have obtained a long-lasting recovery of cardiac function from an LVAD are still in a minority. To make this the majority, therapeutic LVAD should be combined with the apheresis therapies, DFPP and HF. We believe that this concept, a combination of HF and DFPP with therapeutic LVAD, will be the next generation of treatment that has a potential to postpone, or even avoid, heart transplantation.

Changing Trends in Mechanical Circulatory Assistance:. Experience With 131 Consecutive HeartMate VE Left Ventricular Assist Devices

BACKGROUND

The success of long-term implantable ventricular assist devices has led to their increased use in patients previously thought to be unsuitable for mechanical support. As a result, the demographic profile of patients presenting for LVAD support has changed over time. We reviewed our institutional experience to identify emerging risk factors and changing trends in patients who received the HeartMate VE LVAD.

METHODS

The clinical records were reviewed of 131 consecutive LVAD recipients between 1996 and 2001. All perioperative data were collected prospectively and entered into an institutional database. All patients received a preoperative risk stratification score based upon published criteria. The cohort was arbitrarily divided into early (n = 45), mid (n = 45), and late groups (n = 41).

RESULTS

Overall operative mortality was 25% with no difference between groups. The mean risk score increased significantly over time (early 3.5 +/- 0.4 vs. late 5.3 +/- 0.3, p < 0.05). The proportion of patients at high risk for mortality (score >5) was significantly higher in the late group (51% vs. 29%, p < 0.05). Although ventilation time and ICU stay was similar for all groups, hospital stay was longer in the late group (43 days vs. 23 days, p < 0.05). Mean duration of support fell from 90 to 59 days, but this failed to achieve statistical significance. Out-patient therapy decreased from 73% in the early group to 15% in the late group (p < 0.001). Multivariate analysis identified right heart failure (odds ratio 4.1, 95% CI 2-11) and risk score (OR 1.4, 95% CI 1.2-1.6) as independent predictors of death.

CONCLUSIONS

Despite an increasingly high risk patient population, the mortality associated with LVAD therapy has remained constant. Duration of LVAD support has decreased with a trend toward transplantation before hospital discharge. These data continue to support the aggressive institution of mechanical assistance for acute or chronic heart failure.

Management of heart failure: crossing boundary over to the surgical country

Pharmacologic therapy of heart failure appears to have reached its zenith. Few new agents are likely to replace conventional therapy. It is time for a paradigm shift in heart failure management. Aggressive surgical strategies to remodel the failing ventricle will shape heart failure therapy in the decade ahead. The articles that follow will describe in detail the advances that have been made in "crossing the boundary" to surgical treatment of advanced heart failure.

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.

Ventricular assist devices as destination therapy

The prospects for long-term mechanical circulatory support are improving. Axial flow pumps are a promising competitor to pulsatile first-generation LVADs, although the two may serve different patient populations. Centrifugal pumps are in the development phase and seem to require less anticoagulation. Clinical experience has established the safety of diminished pulse pressure circulation, and mechanical unloading appears to promote recovery of the native left ventricle. Under these circumstances, true left ventricular assist is preferable to ventricular replacement and detailed medical management improves patient outcomes. Further clinical trials of destination therapy are indicated and must use more reliable blood pumps implanted before terminal decline into multiorgan failure.

Left ventricular pressure and volume unloading during pulsatile versus nonpulsatile left ventricular assist device support

BACKGROUND

Nonpulsatile axial or centrifugal pumps are the latest generation of left ventricular assist devices (LVAD). Whether left ventricular (LV) unloading and outcome in these devices is similar to pulsatile LVADs during long-term support has not been investigated. We compared LV unloading and mortality between different types of LVAD support (pulsatile versus nonpulsatile).

METHODS

In 31 patients undergoing long-term LVAD implantation (nonpulsatile = 10, pulsatile = 21) preoperative and postoperative echocardiographic and hemodynamic assessment with right heart catheterization had been obtained.

RESULTS

All patients had similar echocardiographic, hemodynamic, and clinical heart failure characteristics at baseline. The degree of LV pressure unloading was the same in both device types, caused by similar reduction of mean pulmonary pressure (18.6 +/- 5.1 versus 18.3 +/- 7.5 mm Hg) and pulmonary capillary wedge pressure (8.9 +/- 4.4 versus 8.0 +/- 7.0 mm Hg). Left ventricular volume unloading was pronounced with a pulsatile device owing to a statistically significant higher pump output (5.1 +/- 1.0 L/min) in comparison with nonpulsatile LVADs (3.6 +/- 0.9 L/min, p < 0.001). Echocardiographic-determined end-systolic indicators confirm this augmentation in pulsatile LVADs. Etiology or the time interval of hemodynamic reassessment had no impact in left ventricular pressure unloading, but LV volume unloading decreased between day 60 and 120 in patients with nonpulsatile LVADs. The preoperative and postoperative transplant mortality was comparable in both groups.

CONCLUSIONS

Left ventricular pressure unloading is similar in patients with nonpulsatile as compared with pulsatile implantable long-term assist devices. Left ventricular volume unloading is pronounced in pulsatile LVADs.

Contemporary medical, surgical, and device therapies for end-stage heart failure

Despite recent advances in medical therapy, mortality remains high following the diagnosis of heart failure (HF). Cardiac transplantation is still the standard surgical treatment option for highly selected patients with severe end-stage HF; however, it is only available to a small percentage of patients. The small number of available donor hearts is an inherent limitation on the ability of cardiac transplantation to greatly impact the management of advanced HF. The increased incidence and prevalence of HF in an ever aging and medically complex population has paved the way for alternative surgical and device treatment strategies. Some of these treatment options include ventricular reduction/remodeling surgery, mitral valve repair, mechanical ventricular assist device implantation, implantable cardioverter-defibrillators, and cardiac resynchronization therapy. Several recent trials have demonstrated the effectiveness of these therapies with regard to improvement in primary cardiac end points, HF symptoms, and survival. Surgical and device techniques are usually combined with optimal medical management of HF. The total cost and actual cost-effectiveness of employing these new therapeutic modalities in a growing population of HF patients remains to be determined.

Pediatric arteriovenous extracorporeal membrane oxygenation (ECMO) as a bridge to cardiac transplantation

BACKGROUND

Since 1990, extracorporeal membrane oxygenation (ECMO) has been used as a bridge to cardiac transplantation in 47 patients.

METHODS

A review of the ECMO database, approved by the Arkansas Children's Hospital institutional review board, forms the basis of this report. We made statistical comparison using Fisher's exact probability testing. The ECMO circuitry was a roller occlusion pump with computer-assisted perfusion system technology.

RESULTS

Thirty-two (68%) patients underwent transcatheter septostomy for cardiac decompression. Diagnosis at presentation was either congenital heart disease (CHD, n = 15) or cardiomyopathy (n = 32). Ages ranged from 1 day to 22 years old (median, 18 months old), and weight ranged from 2.9 to 100 kg (median, 10 kg). The average duration of support was 242 hours (range, 22-1078 hours). Overall long-term survival was 47%, with 16 (34%) patients successfully bridged to cardiac transplantation (of which 9 [56%] survived) and 13 (28%) successfully weaned from ECMO. Patients undergoing ECMO after cardiotomy had 31% survival. Survival was improved significantly (p < 0.02) in patients with cardiomyopathy (59%) vs those with CHD (20%). Patients with cardiomyopathy underwent 8 transplantations with 7 survivors (88%), whereas in the CHD group, there were 8 transplantations with only 2 survivors (25%), p < 0.05. Sub-analysis of the cardiomyopathy group revealed that patients with acute cardiomyopathy in association with documented viral illness had a 75% chance of being weaned from ECMO without undergoing transplantation. Complications during ECMO occurred in 45% of survivors and were more frequent in non-survivors. Infectious complications were most frequent, followed by neurologic complications, technical ECMO problems, and renal insufficiency.

CONCLUSIONS

Patients with cardiomyopathy has a better prognosis than did those with CHD when using ECMO as a bridge to transplantation or survival. Complications are significant and increase with the duration of support. Extracorporeal membrane oxygenation for salvage and subsequent transplantation in this high-risk group of patients requires critical review. Alternative support options must be developed in the pediatric population that will allow improved outcomes, comparable with outcomes achieved in the adult population.

Patient selection for the use of ventricular assist devices as a bridge to transplantation

Patient selection is a critical factor in the outcome associated with the use of mechanical assist devices for the treatment of refractory heart failure/shock. Numerous risk factors impact on the outcome, many of which can be identified and treated before device surgery. This manuscript reviews all the risk factors that have been identified to date and the use of composite risk scores to predict outcome.

Surgical therapy in advanced heart failure

Congestive heart failure (CHF) affects about 1% of adults in the United States and is a contributing factor in >250,000 deaths per year. In an increasingly elderly population, the surgical treatment of CHF made great progress during the past 3 decades, consuming enormous health care resources. Heart transplantation is still the most effective therapy for end-stage heart disease, with the 10-year survival rate after transplantation approaching 50%. Efforts to increase the supply of donor organs have failed to improve the shortage, underscoring the crucial need for alternatives to cardiac allotransplantation. Alternative surgical options to end-stage heart transplantation are rapidly evolving. Left ventricular assist devices have been used as a bridge to heart transplantation for patients who otherwise might die awaiting a new heart. There is also continued interest in the use of these devices either to bridge patients to full recovery or to destination therapy, without the need for heart replacement. Left ventricular reconstruction, including the Batista and Dor procedures, along with mitral valve repair, cardiomyoplasty, and extreme coronary artery bypass graft surgery, are now being increasingly performed as alternative options. The history, status, and personal experience of surgical treatment of end-stage heart disease are discussed.

Management issues for patients with coronary artery disease and heart failure

Despite recent favorable trends in survival, heart failure remains a highly fatal disease. Improvements in the prevention of early death from coronary artery disease, along with an aging population, have resulted in an increased prevalence for heart failure in the United States. In the management of patients with heart failure secondary to coronary artery disease, the relative efficacy of invasive therapies such as coronary revascularization, surgical left ventricle remodeling, internal cardiac defibrillator implantation, cardioverter resynchronization therapy, mechanical ventricular assist, and cardiac transplantation need to be considered. Clinical studies examining these important treatment options are reviewed in order to better define the optimal management strategy for this challenging population of patients.