Blood Volume Analysis of Total Artificial Heart Recipients: A Case Series.

Blood volume analysis provides a quantitative volume assessment in patients with equivocal or discordant clinical findings. Reports on its use in mechanical circulatory support are limited and it has never been described in patients with a total artificial heart. Our series demonstrates that patients supported with total artificial heart as a bridge to transplant have significant reductions in red blood cell volume and heterogeneous adaptations in their total blood volume and plasma volume. Pathologic derangements in our patient's total blood volume were targeted to restore euvolemia.

In Search of the Holy Grail of Artificial Hearts: Are We There Yet?

The total artificial heart (TAH) has a long and rich history, being the product of decades of innovation, hard work, and dedication. This review examines the history of the TAH, a device that has revolutionized the treatment of end-stage biventricular heart failure. It reviews the development of the device from early concepts to the current state-of-the-art device, the SynCardia TAH, which has been implanted in over 2,000 patients worldwide. The article also discusses the challenges and successes experienced by researchers, clinicians, and patients throughout the development of TAH devices. Our focus will also be on discussing the hemostatic alterations in patients implanted with TAH and anticoagulation strategies to decrease associated thromboembolic risks. The article concludes with a look at other novel TAH devices and the future of TAH as an increasingly viable treatment for end-stage heart failure.

The total artificial heart: where have we been, where are we now, where are we going?

The incidence and prevalence of end-stage heart failure continue to rise; however, the number of donor hearts available for transplantation continues to be limited. Therefore, alternatives to transplantation, such as the use of total artificial hearts (TAH), are necessary. The long and winding road to the development and implantation of the ideal TAH remains under construction. Although efforts have been ongoing for almost a century, researchers and clinicians continue to improve currently available TAHs and design and construct new models. With mortality and morbidity rates decreasing, particularly at high-volume centers with a dedicated team and carefully selected patients, the use of TAHs as a bridge to transplantation, and even destination therapy in clinical trials, the future of TAHs is bright.

Heart Transplant Outcomes After Total Artificial Heart.

BACKGROUND: We sought to compare heart transplant (HTX) outcomes from patients with a total artificial heart (TAH), biventricular assist device (BiVAD), or left ventricular assist device (LVAD) as a bridge to transplant (BTT). Interagency Registry for Mechanically Assisted Circulatory Support (INTERMACS)-Scientific Registry of Transplant Recipients (SRTR) created a dataset with TAH or durable mechanical circulatory support (MCS) who reached HTX between 2006 and 2015. METHODS: The retrospective analysis compared TAH outcomes with those with a BiVAD or LVAD before HTX. The primary outcome was posttransplant survival at 1, 36, and 60 months. Secondary outcomes included simultaneous heart-kidney transplants, donor characteristics, and mortality risk factors. INTERMACS-SRTR cohort had, at the time of HTX, 2762 patients with LVAD; 205 BiVAD (139 durable and 66 temporary RVAD); 176 TAH (6 prior HeartMate II). RESULTS: Sixty months after HTX, mortality rates were 16.5% in the total group: LVAD 15.2%, BiVAD 22.4%, and TAH 29%. Survival differed between the LVAD, the TAH, and BiVAD but not between the BiVAD and TAH groups. One-year survival and complication rates were similar across groups-there was no difference in survival by donor age in the overall cohort. There was a difference in TTD based on recipient age in the LVAD group but not in BiVAD or TAH groups. Occurrence of HTX-kidney and post-transplant dialysis were higher in the TAH versus LVAD and BiVAD groups. CONCLUSIONS: The TAH is an efficacious BTT. Refinements in technology and patient selection may improve outcomes.

The Total Artificial Heart: Where Are We?

The total artificial heart (TAH) is a device that replaces the failing ventricles. There have been numerous TAHs designed over the last few decades, but the one with the largest patient experience is the SynCardia temporary TAH. The 50-mL and 70-mL sizes have been approved in the United States, Europe, and Canada as a bridge to transplantation. It is indicated in patients with severe biventricular failure or structural heart issues that preclude the use of a left ventricular assist device. The majority of the patients implanted are Interagency Registry for Mechanically Assisted Circulatory Support profile 1 or 2. The 1-year survival in experienced centers that have implanted over 10 TAHs is 73%. The risk factors for death include older age, need for preimplantation dialysis, and malnutrition. The most common causes of death are multiple organ failure, usually the result of physiologic deterioration before implantation, and neurologic dysfunction. The device allows the patient to be discharged home and managed as an outpatient. Proper patient selection, the timing of intervention, patient care, and device management are essential for a suitable outcome. In addition, the CARMAT TAH is another device that will soon be studied in a clinical trial in the United States. The BiVACOR TAH is a revolutionary design utilizing electromagnetic levitation that is expected to enter a clinical trial in the next few years.

Platelet Mapping by Thromboelastography and Whole Blood Aggregometry in Adult Patients Supported by Mechanical Circulatory Support Device on Aspirin Therapy.

Patients on mechanical circulatory support (MCS) devices are placed on aspirin and may require platelet function testing (PFT) to monitor the adequacy of therapy. Routine laboratory PFT is performed using whole blood aggregation (WBA) which typically has a long turnaround time (4-5 hours) and may not be readily available. By contrast, platelet mapping by thromboelastography (TPM) can provide results within 45 minutes. The objective of this study was to compare the results of TPM with WBA. We compared platelet mapping maximal amplitude (MA) by TPM with that of arachidonic acid (AA) to WBA with AA by impedance. We analyzed paired samples where both TPM and WBA were available. Of 45 paired samples, 34 were from 29 MCS patients and 11 were from non-MCS patients. When applying institutional interpretation guidelines with an MAActivator cutoff of ≤40 mm, WBAAA vs TPM MAAA in non-MCS and MCS patients correlated well with an accuracy of 100 and 94.4%, respectively. MAActivator >40 had poor correlation with an accuracy of 37.5%. Irrespective of MAActivator value, TPM AA inhibition expressed in percent of inhibition had poor accuracy. When used with proper guidelines for interpretation, specifically when MAActivator ≤ 40 mm, TPM is a suitable and reliable test to use for MCS patients on aspirin.

Total artificial heart: surgical technique in the patient with normal cardiac anatomy.

Heart failure is a complex, growing problem with significant morbidity and mortality. Though heart transplantation remains the gold standard treatment for end-stage heart failure, there remains a national shortage of donor hearts. Mechanical circulatory support has provided an additional option for clinicians to support patients for the purposes of bridging patients to transplantation or to be used for destination therapy purposes. Despite generally favorable outcomes with univentricular support, in a subset of patients with biventricular heart failure, an isolated left ventricular assist device is not sufficient. Right ventricular failure has a negative impact on patient survival if not identified and treated promptly. The Total Artificial Heart (TAH) is the only Food and Drug Administration (FDA) approved artificial heart used for bridging patients to transplantation. Outcomes in patients who undergo implantation of the TAH at experienced centers have been good and reproducible.

Assessing Cerebrovascular Hemodynamics Using Transcranial Doppler in Patients with Mechanical Circulatory Support Devices.

BACKGROUND AND PURPOSE: Mechanical circulatory support (MCS) devices are commonly used in heart failure patients. These devices carry risk for presumably embolic and additionally hemorrhagic stroke. Alterations in blood flow play a key role in stroke pathophysiology, and we aimed to learn more about hemodynamic compromise. In this study, we used transcranial Doppler (TCD) ultrasound to define hemodynamics of commonly used nonpulsatile MCS devices, as well as pulsatile devices, with special attention to the total artificial heart (TAH). METHODS: From 2/2013 through 12/2016, we prospectively enrolled patients with MCS who underwent TCD imaging. We analyzed TCD parameters, including peak systolic velocity, end-diastolic velocity, pulsatility indices (PIs), and number of high-intensity transient signals. Waveform morphologies were compared between various MCS devices. RESULTS: We performed 132 TCD studies in 86 MCS patients. Waveforms in patients supported by venoarterial-extracorporeal membrane oxygenation demonstrated continuous flow without clear systolic peaks with an average (±SD) PI of .43 (±.2). PIs were low in patients with continuous-flow left ventricular assist devices with a mean PI of .32 (±.13). Impella patients had morphologically distinct pulsatile waveforms and a higher mean PI of .65 (±.24). In intra-arterial balloon pump patients, mean PI was 1.01 (±.16) and diastolic upstrokes were pronounced. In TAH patients, mean middle cerebral artery velocity of 79.69 (±32.33) cm/seconds and PI of .74 (±.14) approached normal values. CONCLUSION: TCD can detect characteristic waveforms in patients supported by various MCS devices. These device-specific TCD patterns are recognizable and reproducible.

Clinical Outcomes of Impella Microaxial Devices Used to Salvage Cardiogenic Shock as a Bridge to Durable Circulatory Support or Cardiac Transplantation.

Temporary mechanical circulatory support (MCS) can be a bridge to decision for patients in severe cardiogenic shock who may be eligible for durable support or transplantation. Outcomes with Impella microaxial devices for salvage of severe shock in the end-stage heart failure population are not well described. Patients who underwent Impella placement as a bridge to decision, durable MCS, or transplantation were included. Eighty Impella devices (2.5 [1.3%], CP [53.8%], and 5.0 [45.0%]) were placed in 64 patients. Implant age was 56.2 ± 12.5 years. Mean duration of assisted support was 13.2 ± 15.1 days, and median duration per device was 7 days (interquartile range: 3-14). A total of 48.4% were in Interagency Registry for Mechanically Assisted Circulatory Support (INTERMACS 1) shock at implant, 51.6% in profile 2. Recent cardiopulmonary resuscitation (CPR) (26.7%), ventilator use (67.2%), and extracorporeal membrane oxygenation (ECMO) use (26.7%) were frequent. Forty four of sixty four (68.8%) survived to next therapy: durable MCS (40.9%), heart transplant (OHT) (36.4%), and recovery (22.7%). Overall 30 and 60 day survival were 67.2% and 65.6%, respectively. Thirty and 60 day survival conditional on having survived to next therapy were 94.1% and 91.2%, respectively. Survivors were less likely to be on ventilators (p = 0.049) or continuous renal replacement therapy (p < 0.001) but were otherwise not different from nonsurvivors by age, sex, INTERMACS profile, CPR, prevalence of ischemic cardiomyopathy, among other characteristics. Sixteen patients were directly bridged to heart transplantation, and all were alive at long-term follow-up. Impella devices can be used to salvage patients in severe heart failure as a bridge to decision, durable MCS, or transplantation. Baseline demographics are not predictive of survival. Their use for this indication is increasing and further investigations are warranted.

Role of Methadone in Extracorporeal Membrane Oxygenation: Two Case Reports.

Extracorporeal membrane oxygenation (ECMO) affects pharmacokinetics/dynamics of drugs in unpredictable ways. Anecdotally, ECMO patients require high doses of opioids and sedatives, leading to concerns of tolerance. Methadone is a long-acting synthetic opioid with antagonist properties at the n-methyl-d-aspartate (NMDA) receptor. It has been shown to improve spontaneous breathing trials and weaning from mechanical ventilation; however, there is no literature describing its use in ECMO. We describe two patients from the cardiac surgery intensive care unit at Cedars Sinai (Los Angeles, CA) on ECMO for over 30 days maintained on methadone.

High Molecular Weight von Willebrand Factor Multimer Loss and Bleeding in Patients with Short-Term Mechanical Circulatory Support Devices: A Case Series.

Acquired von Willebrand syndrome (VWS) due to loss of high-molecular-weight multimers (HMWMs) has been reported with longer term mechanical devices and is associated with mucosal bleeding, a primary hemostasis type of bleeding. However, little is known whether a similar defect occurs in patients with short-term mechanical circulatory support (STMCS) devices. We reviewed von Willebrand factor (VWF) profiles in patients with STMCS devices who underwent VWS workup from December 2015 to March 2017 at an academic quaternary care hospital. There were a total of 18 patients (57.0 ± 12.7 years old; 83.3% male) including nine with mucosal bleeding and nine with decreasing hemoglobin. The STMCS devices included Impella (n = 11), Impella and right ventricular assist device (n = 2), and an extracorporeal membrane oxygenator (n = 5). The mean HMWM by quantitative VWF multimer analysis was 3.6% ± 1.3% (normal cutoff: 18-34%). In all 10 cases in which VWF activity, fibrinogen, factor VIII, or VWF antigen level were obtained, they were either normal or elevated. All cases demonstrated high normal or elevated levels of low molecular weight multimers (LMWMs). These findings are consistent with type 2 VWS (qualitative defect). This is the first study that quantitatively describes STMCS device-associated HMWM loss, which may contribute to mucosal bleeding. This finding may have implications for intraoperative management during implantation of longer term devices or heart transplantation or other surgery while on STMCS.

Interagency registry for mechanically assisted circulatory support report on the total artificial heart.

BACKGROUND: We sought to better understand the patient population who receive a temporary total artificial heart (TAH) as bridge to transplant or as bridge to decision by evaluating data from the Interagency Registry for Mechanically Assisted Circulatory Support (INTERMACS) database. METHODS: We examined data related to survival, adverse events, and competing outcomes from patients who received TAHs between June 2006 and April 2017 and used hazard function analysis to explore risk factors for mortality. RESULTS: Data from 450 patients (87% men; mean age, 50 years) were available in the INTERMACS database. The 2 most common diagnoses were dilated cardiomyopathy (50%) and ischemic cardiomyopathy (20%). Risk factors for right heart failure were present in 82% of patients. Most patients were INTERMACS Profile 1 (43%) or 2 (37%) at implantation. There were 266 patients who eventually underwent transplantation, and 162 died. Overall 3-, 6-, and 12-month actuarial survival rates were 73%, 62%, and 53%, respectively. Risk factors for death included older age (p = 0.001), need for pre-implantation dialysis (p = 0.006), higher creatinine (p = 0.008) and lower albumin (p < 0.001) levels, and implantation at a low-volume center (≤10 TAHs; p < 0.001). Competing-outcomes analysis showed 71% of patients in high-volume centers were alive on the device or had undergone transplantation at 12 months after TAH implantation vs 57% in low-volume centers (p = 0.003). CONCLUSIONS: Patients receiving TAHs have rapidly declining cardiac function and require prompt intervention. Experienced centers have better outcomes, likely related to patient selection, timing of implantation, patient care, and device management. Organized transfer of knowledge to low-volume centers could improve outcomes.

Characterizing Predictors and Severity of Vasoplegia Syndrome After Heart Transplantation.

BACKGROUND: Vasoplegia is characterized as a severe vasodilatory shock after cardiac surgery, and can be associated with substantial morbidity. Increased systemic inflammation and endothelial dysfunction, often related to prolonged cardiopulmonary bypass times, anesthesia, or mechanical circulatory support have been shown to be associated with the development of vasoplegia. We sought to identify risk factors and the impact of various degrees of vasoplegia after heart transplantation. METHODS: A retrospective review was conducted of 244 consecutive patients who underwent heart transplantation over a 3-year period. Patients were divided into three groups: no vasoplegia, mild vasoplegia (requiring one vasopressor), and moderate/severe vasoplegia (more than two vasopressors). One-year survival, freedom from rejection, and postoperative complication rates were assessed. Risk factors for vasoplegia subgroups were retrospectively identified. RESULTS: Vasoplegia syndrome was observed in 34.3% of patients after heart transplantation (mild, 74.1%; moderate/severe, 25.9%). Cardiopulmonary bypass time was significantly longer and pretransplant creatinine was significantly higher in the moderate/severe vasoplegia group. There was a strong trend toward greater use of mechanical circulatory support among moderate/severe vasoplegia patients compared with mild and no vasoplegia patients. After heart transplantation, 1-year survival, freedom from rejection, and need for hemodialysis were not significantly different between groups. CONCLUSIONS: Vasoplegia syndrome is common after heart transplantation. Risk factors for increased severity include longer cardiopulmonary bypass times and elevated preoperative creatinine. Although higher rates of mortality or graft rejection were not detected, vasoplegia was associated with prolonged intubation, greater blood product usage, and lengthened hospital stay. Further studies involving larger cohorts are warranted.

Acute Cor Pulmonale in Veno-Venous Extracorporeal Membrane Oxygenation: Three Case Reports.

A retrospective review of three patients with acute respiratory distress syndrome (ARDS) and normal baseline right ventricular function admitted to the Cardiac Surgery Intensive Care Unit whom developed acute cor pulmonale while on veno-venous extracorporeal membrane oxygenation. These patients were diagnosed with ARDS using Berlin Criteria definitions and cannulated with a dual lumen (Avalon) cannula. Despite variations in history, presentation, and course, findings of acute cor pulmonale were encountered 4 to 6 weeks after extracorporeal membrane oxygenation cannulation. The potential mechanisms include thromboembolic burden to the pulmonary vasculature, hypoxemia, acidosis, the pathologic progression of ARDS, and chronic nonphysiologic flow to the right heart.