The CardioWest total artificial heart as a bridge to transplantation

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.

Anesthetic and Perioperative Considerations in Patients Undergoing Placement of Totally Implantable Replacement Hearts

The recent successful implantation of the AbioCor im plantable replacement heart at the Rudd Heart-Lung Institute, Jewish Hospital, Louisville, KY, has renewed clinical interest in the use of the mechanical replace ment heart as therapy for intractable heart failure. Al though the number of orthotopic heart transplants has plateaued in the past decade, the number of patients requiring transplantation continues to increase. This supply/demand discrepancy continues to be the main catalyst for the research and development of other therapies for the failing heart. This review addresses perioperative considerations, monitoring modalities, and perioperative therapeutic interventions that may help guide the cardiac anesthesiologist through the challenges presented by implantation of total replace ment hearts in end-stage cardiac patients.

Neurologic Events With a Totally Implantable Left Ventricular Assist Device: European LionHeart Clinical Utility Baseline Study (CUBS)

BACKGROUND

Neurologic events such as thromboembolic and hemorrhagic strokes are common complications of mechanical circulatory support. We report the neurologic events observed in patients treated for end-stage heart failure with the implantable, pulsatile LionHeart left ventricular assist device (LVAD). This sub-study was part of the LionHeart European Clinical Utility Baseline Study (CUBS).

METHODS

Twenty-three male patients were implanted with the LionHeart LVAD in a non-randomized, observational study. Neurologic events were classified into three categories: (1) transient ischemic attacks (TIAs); (2) strokes, including cerebrovascular accidents (CVAs) and intracranial bleeding (ICB); and (3) "other," including hypoperfusion, coma and brain death. Neurologic injuries were also categorized as transient/reversible or permanent/disabling.

RESULTS

Thirteen of 23 patients (57%) had a total of 30 neurologic events. Eight patients (35%) had 18 TIAs. Eight patients (35%) also had a stroke, either CVA (n = 5, 22%) or ICB (n = 3, 13%), and 5 of these patients (22%) also had 12 TIAs. Three patients (13%) had 4 "other" neurologic events. Ten patients (43%) had transient/reversible neurologic deficits and 10 (43%) had permanent/disabling events. One patient (4%) had intracranial bleeding as a primary cause of death (anti-coagulation-related hemorrhage). The combined incidence of neurologic events was 1.37 events/patient-year. The incidences of transient and permanent events were 0.91 and 0.46 event/patient-year, respectively.

CONCLUSIONS

Neurologic events caused morbidity in the CUBS trial, with infrequent mortality. These results are similar to previous experiences with destination therapy and underscore the need for improvements in LVAD design, patient selection and patient management to reduce the incidence of neurologic events.

Patients With a Body Surface Area Less Than 1.7 m2 Have a Good Outcome With the CardioWest Total Artificial Heart

BACKGROUND

A body surface area (BSA) of 1.7 m2 was considered as the lower limit to implant a CardioWest Total Artificial Heart (TAH). We reviewed our experience with the TAH in patients with a BSA of less than 1.7 m2.

METHODS

From April 1986 to May 2003, among 149 patients implanted with a TAH in our institution, 30 had a BSA of less than 1.7 m2 (Group I). Results were compared with the remaining 119 patients (Group II).

RESULTS

One patient in Group I experienced a fitting problem and was left with the chest open. Otherwise, in this group, the Day 1 cardiac index averaged 3.6 +/- 0.6 liter/min/m2, which was significantly higher than the 2.8 +/- 0.36 liter/min/m2 observed in Group II. Post-implantation central venous pressure and mean arterial pressure were similar in both groups: 14.7 +/- 3.8 mm Hg vs 14.5 +/- 4 mm Hg and 87 +/- 23 mm Hg vs 88 +/- 19 mm Hg, respectively. In Group I, survival on the device dramatically increased from 9% before 1992, to 36% between 1992 and 1997 and finally reached 75% after then. In the meantime, for the same time periods, global survival to hospital discharge increased from 9% to 36% and reached 50% after 1997. In Group II, global survival to hospital discharge was 25.5% before 1992, 34.6% between 1993 and 1997, and reached 52% thereafter.

CONCLUSION

The CardioWest TAH can be used in patients with a BSA between 1.5 m2 and 1.7 m2 with few fitting problems. In this group of patients, results are similar to those obtained in patients with a BSA greater than 1.8 m2.

The AbioCor totally implantable replacement heart

The AbioCor artificial heart (Abiomed, Inc., Danvers, MA) represents the latest technologic advancement in the quest for a total heart replacement system. The AbioCor is an electric heart with fully implantable components. The Food and Drug Administration approved a clinical trial in January 2001. The clinical trial was designed as an initial feasibility study to determine the safety and efficacy of this first generation system. The study criteria include end-stage adult heart failure patients who are not transplant candidates. These patients have biventricular failure with a predicted 30-day life expectancy of less than 30%. On July 2, 2001 the first AbioCor device was implanted. Six other patients have undergone implantation to date. Four of the seven have been successful as defined by the study parameters of 60-day survival with improved quality of life. Two patients were discharged from the hospital. Outpatient activities were possible in four patients. There have been no device malfunctions and no device-related infections. The trial is active and enrollment is ongoing.

Biventricular mechanical replacement

The role of biventricular mechanical support (assist or replacement) is important for the management of severe biventricular cardiac failure. One only has to look at the role of cardiac transplantation to realize the benefit of a natural therapy to end-stage heart disease. Although the technology today is not that different from the technology that existed a decade ago (ie, BioMedicus, BVS 5000, Thoratec, CardioWest), the application of it and the experience gained by it have allowed surgeons to improve the chances of a positive outcome. In terms of new technologies for biventricular mechanical support, the totally implantable versions of a VAD (eg, Thoratec IVAD) or the totally implantable TAH (eg, AbioCor) are promising technologies that add to the spectrum of devices as destination therapy or alternatives to transplantation. And lastly, the role of the Berlin Heart as a tool for the management of biventricular failure in pediatric patients may be realized in the United States in the near future. In conclusion, the treatment of biventricular failure (acute or chronic) with assist or replacement technologies has gained widespread acceptance in the medical and surgical communities. It is now time to use these technologies wisely in an effort to treat the worldwide epidemic of congestive heart failure.

Improved Early Survival with the Total Artificial Heart

We report our experience with the total artificial heart (TAH) to determine if outcomes have improved. Thirty-one patients received the TAH as a bridge to transplant and were divided into the two groups A (eighteen implanted in the first eight years) and B (thirteen implanted in the last eight years). Changes in management included immediate sternal closure, early extubation, delayed transplant listing, early rehabilitation, and measurement of preformed antibodies. The infection rate in B was lower than in A, both during support (31% versus 39%) and following transplant (38% versus 72%), and rejection was lower in B than in A (0% versus 44%). There was no difference in neurological events between groups; however, reopening was more frequent in B (61% versus 28%). Hospital survival increased from 61% in A to 85% in B; however, this was not statistically significant. We hypothesize that this improvement was likely due to changes in patient management.

Successful bridge to transplantation in a patient with Becker muscular dystrophy-associated cardiomyopathy

A 28-year-old male patient diagnosed with Becker muscular dystrophy (BMD)-associated cardiomyopathy was successfully bridged to transplantation with the Cardiowest total artificial heart. Dramatic improvement of muscular functional status occurred following transplantation.

Synthetic membrane neo-pericardium facilitates total artificial heart explantation

BACKGROUND

In the past, explantation of the Cardio West total artificial heart (TAH) has been technically challenging because of the presence of dense adhesions and extremely thickened pericardium. To prevent this, we constructed a synthetic neo-pericardium in 14 patients.

METHODS

Using expanded polytetrafluoroethylene (e-PTFE) membrane, we constructed a pericardium within the pericardium, or "neo-pericardium," completely covering the Cardio West TAH separating the native atria from the native pericardium, and wrapping the ascending aorta from the outflow conduit distally for about 5 to 7 cm.

RESULTS

Of the 14 patients, 9 were transplanted and could be evaluated, 3 died on device support, and 2 are currently on device support. In each case, we attained faster (by 25 minutes) and easier reentry through the sternum. Surgical planes around the aorta, over the right and left atria, and throughout the pericardial space became apparent immediately after e-PTFE membrane removal. The pericardium and related tissues although slightly thickened (<2 mm) were pliable compared with our previous 36 patients, with very thick adherent pericardium over the device and native atria.

CONCLUSIONS

The plastic materials forming the ventricular housing and drivelines of the Cardio West TAH and the Dacron outflow conduits have in the past caused profound local inflammatory reactions, resulting in extremely dense adhesions and thickened adherent pericardium. Using e-PTFE membrane to fashion a complete neo-pericardium and to wrap the ascending aorta at the time of Cardio West implantation dramatically reduces adhesions and pericardial thickening and facilitates explantation.

Future directions of cardiac assistance

During the past decade, mechanical circulatory support has gained increased acceptance as a treatment for patients with severe heart failure who are unresponsive to conventional treatment. Steady progress has been made with respect to technology, patient selection, and postoperative management. Currently, a wide array of circulatory assist pumps offers various levels of assistance and degrees of postoperative mobility. These devices not only save lives (lowering the mortality of heart transplant candidates by 55%) but, in some long-term bridge-to-transplant cases, permit hospital discharge and cardiac rehabilitation. More than 4000 patients have been supported by long-term assist pumps worldwide. In addition to being used for bridging to transplantation or bridging to the use of some other bridging device, long-term circulatory assist devices are being evaluated as bridges to recovery or alternatives to transplantation in selected patients with severe heart failure. Moreover, several total artificial hearts have shown considerable potential in calves and will soon undergo clinical trials aimed at permanent heart replacement. Eventually, as cardiac support or replacement devices become smaller, more durable, and less obtrusive, they may become as conventional and commonplace as pacemakers are today.