Fig. 29.1
The CardioWest Total Artificial Heart (TAH). The TAH consists of two pneumatically driven pulsatile pumps that replace the ventricle and four heart valves. The device is connected to the atrial cuffs and great vessels (Reprinted with permission from Syncardia Systems Inc.)
Fig. 29.2
The pneumatic drivers for the CardioWest Total Artificial Heart (TAH). Patients after device implantation are connected to the 400 lb. in hospital drive (a). The portable Freedom Driver (b) is under clinic investigation and will allow for discharge to home with the CardioWest TAH (Images provided by Joe Kuttenkuler, Virginia Commonwealth University)
The AbioCor IRH replaces the ventricles of the heart, and has a unique charging mechanism allowing it to be free of a percutaneous driveline [14]. The AbioCor IRH has four internal components and four external components. The internal components include the AbioCor thoracic unit, lithium ion battery, controller, and TET coil (Fig. 29.3). The thoracic unit consists of an energy converter, two pumping chambers (left and right ventricles) and four 24 mm tri-leaflet valves, along with a hydraulic pumping system. The energy converter is situated between the chambers and contains a centrifugal pump driven by a brushless direct current motor. The centrifugal pump pressurizes low-viscosity hydraulic fluid, which utilizes a 2-position switching valve to alternate pumping of the right and left chambers. Displacing fluid to one ventricle creates negative pressure in the other ventricle resulting in alternating left and right ventricular pumping. The rate of the switching valve can be set between 75 and 150 beats per minute and results in flows of 4–8 liters per minute. Blood contacting surfaces are made of polyetherurethane. The internal controller transmits device performance data to a bedside console by radiofrequency transmission, including hydraulic pressure waveforms and battery status. Implementing a process of inductive coupling, internal TET coil accepts high frequency power transmitted through the skin from an external TET coil (secured over the internal TET coil with adhesive dressings). The external components include the external TET coil, portable TET module (ambulatory use), bedside console, and batteries.
Fig. 29.3
The fully implantable AbioCor Implantable Replacement Heart (IRH). The device is shown in panel (a) with all of the implantable internal components include the AbioCor thoracic unit, lithium ion battery, controller, and TET coil. The chest x-ray (b) shows the components of the device in a patient (Reprinted with permission from Abiomed)
The AbioCor IRH was first approved by the Food and Drug Administration (FDA) in September of 2006 as a Humanitarian Use Device. However, this pump is currently no longer being manufactured, thus the remainder of the chapter will focus on the CardioWest TAH.
Clinical Trials
Much of the contemporary published experience with the CardioWest TAH comes from the 10-year North American pivotal study and single center experiences from high volume European hospitals (data summarized in Table 29.1). There are no randomized, controlled trials that compare the TAH to other forms of biventricular support or replacement.
Copeland et al. [17] | Leprince et al. [15] (127 pts); | El-Banayosy et al. [16] (42 patients) | Roussel et al. [18] (42 patients) | ||
|---|---|---|---|---|---|
Protocol (N = 81) | Exception (N = 14) | ||||
Preoperative characteristics | |||||
Age (years, mean ± SD ) | 51 ± 10 | NR | 38 ± 13 | 51 ± 13 | 46 ± 10 |
Male gender (%) | 86 % | NR | 85 % | 88 % | 95 % |
IABP (%) | 36 % | NR | NR | 67 % | 33 % |
Multiple/Inotropes Pressors (%) | 100 % | NR | NR | 100 % | NR |
Mechanical ventilation (%) | 42 % | NR | NR | 74 % | 14 % |
Pre-operative dialysis (%) | 0 % | NR | NR | 52 % | 7 % |
Pre-operative cardiac arrest (%) | 37 % | NR | NR | 45 % | 14 % |
Failure to wean from CPB (%) | 19 % | NR | NR | 26 % | NR |
Survival to transplant (%) | 79 % | 50 % | < 1993 = 43 %; 1993–1997 = 55 %; 1997–2001 = 74 % | 26 % transplanted;22 % alive on device | 72 % |
Days on device (Mean ± SD) | 79 ± 84 | NR | NR | 86 ± 89 | 101 ± 86 |
Device malfunction | |||||
Ruptured diaphragm (%) | 1 % | 1 % | 2 % | 0 % | |
Catheter entrapment (%) | 3 % | NR | 2 % | 2 % | |
Fit complication (%) | 5 % | NR | 19 % | 5 % | |
Complications | |||||
Any bleeding (%) | 44 % | 26 % | 21 % | NR | |
Bleeding requiring re-operation (%) | 21 % | NR | 19 % | 52 % | |
Pump/mediastinal infection (%) | 5 % | NR | 3 % | 5 % | 5 % |
Driveline infection (%) | 21 % | NR | NR | 7 % | 14 % |
Any infection (%) | 77 % | NR | NR | 83 % | |
Any neurological Event (%) | 27 % | 0.016 event/month | 9.6 % | ||
Stroke (%) | 12 % | NR | 0 % | NR | 8 % |
Hemodialysis (%) | 27 % | 15 % in those with normal baseline | 64 % | ||
Outcomes | |||||
Survival to transplant (%) | 79 % | 50 % | < 1993 = 43 %; 1993–1997 = 55 %; 1997–2001 = 74 % | 26 % transplanted;22 % alive on device | 72 % |
Post-transplant 1-Yr Survival (%) | 86 % | NR | NR | NR | 90 % |
In 1990, use of the Jarvik-7 was banned in the United States, until 1993 when the FDA approved the device for investigational use at five U.S. centers. Dr. Jack Copeland and colleagues published their 10-year experience evaluating the safety and efficacy of the now renamed CardioWest TAH as a bridge to heart transplantation [19]. The study included 95 patients of which 81 met the standard inclusion criteria of the protocol. The survival analysis of this protocol group was the basis for eventual FDA approval of the device in the United States. Fourteen of the patients were excluded from the core analysis because they failed to meet the protocol inclusion criteria or received the device on a compassionate use exception (absent documentation for meeting inclusion criteria [4], rescue from LVAD [3], dialysis [2], not transplant candidate [2], co-existing medical condition likely to prevent survival [2] or failing cardiac allograft [1]).
The investigators established that the device restored end-organ function and hemodynamic stability, thus effectively bridging dying patients to heart transplantation at an impressive rate of 79 %, the highest reported rate for any device at the time of publication. Additionally, patients experienced a post-transplant survival comparable to published registry data (1-year 86 %, 5-year 64 %). The device had very low failure rates (1 case of diaphragm rupture) and most of the device- related complications were related to fitting complications (2 deaths) and catheter entrapment from upper extremity central venous lines (3 deaths).
Unlike in the United States, European utilization of the Jarvik-7/CardioWest TAH has been uninterrupted since the 1980’s. Reports from France and Germany describe outcomes from a wide spectrum of patients of high severity of illness including a higher prevalence of preoperative cardiac arrest, hemodialysis, and mechanical ventilation. Leprince published the French experience in 127 patients over 15 years [15]. Most deaths were related to multi-organ failure and occurred within 2 weeks (12 ± 9 days) of device implantation. A German series by El-Banayosy et al. reported on 42 patients implanted with the TAH who were extremely sick, many who would have been excluded criteria for the U.S. trial. The study reported a 52 % mortality rate on the TAH, with most patients dying from irreversible pre-implantation end organ failure [16]. The findings of the German study highlight the limitations of the pump in the setting of chronically or severely compromised liver and kidney function.
Patient Selection
The current application of the TAH is to bridge patients dying from bi-ventricular failure to heart transplantation. The inclusion criteria for the U.S. clinical trial included (1) heart transplant eligibility, (2) New York Heart Association class IV symptoms, (3) adequate thoracic cavity size, and (4) hemodynamic compromise (Cardiac index ≤2.0 liters/min/m2 with systemic hypotension or high central venous pressure [>18 mmHg] or requirement of multiple vasoactive medication/IABP/CPB) [19]. Real world application of the device has extended to a number of indications where LVAD therapy is not ideal: including patients with myocardial wall rupture, extensive intracavitary thrombus formation, cardiac allograft failure, refractory arrhythmias, mechanical valves, complex congenital heart disease, restrictive cardiomyopathy, hypertrophic cardiomyopathy, proximal aortic disease, failed LVAD therapy and acute fulminant cardiogenic shock.
Right ventricular failure in patients who have LVADs portends a poor outcome [20]. However, identifying patients with right ventricular dysfunction that would benefit from biventricular support/replacement rather than an LVAD for bridge to heart transplantation remains clinically challenging. While a myriad of risk measures for right ventricular failure have been identified, congruency of these measures in the real world patient is often absent. Table 29.2 lists a sampling of the various echocardiographic, hemodynamic, clinical and laboratory measures that have been proposed [20–24]. Furthermore, selecting type of biventricular therapy can be clinically challenging. In retrospective reports, outcomes with biventricular assist devices (bi-VADs) have been generally sub-optimal compared to the TAH, however comparative prospective data are lacking [25, 26]. In general, patients requiring biventricular support with potential for myocardial recovery should be considered for bi-VADs; while those with refractory shock or expected to require prolonged support may benefit from the TAH.
No RVF | RVF | P | Study | |
|---|---|---|---|---|
Hemodynamic parameters | ||||
RVSWI (mmHg •mL•m−2) | 368 ± 245 | 151 ± 75 (RVAD) | 0.01 | Fukamachi et al. [24] |
556 ± 298 | 391 ± 226 (RVAD) 541 ± 344 (inotropes > 14d) 560 ± 335 (Late RVF) | 0.04 | Kormos et al. [20] | |
463 ± 180 | 330 ± 160 (RVAD, inhaled NO, inotropes>14d) | 0.002 | Kato et al. [23] | |
Cardiac output (L/min) | 3.5 ± 0.9 | 2.8 ± 0.5 (RVAD) | 0.02 | Fukamachi et al. [24] |
Cardiac index (L/min/m2) | 2.5 (IQR 1.2–4.3) | 2.1 (IQR 1.5–3.1) (RVAD, inhaled NO, hypotension) | 0.04 | Potapov et al. [21] |
Pulmonary artery systolic pressure (mmHg) | 38 ± 11 | 31 ± 5 (RVAD) | 0.015 | Fukamachi et al. [24] |
52 ± 11 | 62 ± 11 (inotropes>14d) | 0.03 | Puwanant et al. [22] | |
Central venous pressure (mmHg) | 12 ± 6.4 | 16 ± 6 (RVAD) 15 ± 7 (inotropes > 14d) 13 ± 8 (late RVF) | 0.01 | Kormos et al. [20] |
Echocardiographic parameters | ||||
TAPSE (mm) | 15 ± 6 | 8 ± 4 (inotropes>14d) | <0.01 | Puwanant et al. [22] |
RV systolic pressure (mmHg) | 46 ± 11 | 60 ± 14 (inotropes>14d) | 0.02 | Puwanant et al. [22] |
LVEDd (mm) | 75 (IQR 53–102) | 68 (IQR 64–75) (RVAD, inhaled NO, hypotension) | 0.03 | Potapov et al. [21] |
73 ± 13
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