A 55-year-old male with a history of dilated ischemic cardiomyopathy, presented with NYHA Class IV CHF, with worsening SOB. Echo demonstrated biventricular failure. Invasive hemodynamic monitoring suggested low cardiac output with elevated filling pressures including a high CVP and laboratory values were indicative of renal and hepatic dysfunction. Initial trial of therapy with dual inotropes did not lead to an improvement in his clinical status. His ABO blood group was O+. He was considered a candidate for advanced therapies and a TAH was inserted. Following adequate clinical recovery and improvement in his functional and nutritional status, he had a heart transplantation and was discharged in a stable condition.

INTRODUCTION

Heart transplantation is considered the gold standard for the treatment of end-stage heart failure (HF). However, the total number of patients receiving heart transplantation worldwide in the last few decades has remained around 4000 due to the limitations posed by the supply of donor hearts. The rising worldwide epidemic of HF coupled with increasing waitlist times for heart transplantation has made the concept of developing heart assist or heart replacement devices a reality. Total artificial heart (TAH), ventricular assist device (VAD), and cardiopulmonary bypass technologies all share the same lineage, originating in 1934 when Michael Ellis DeBakey described a dual roller pump for blood transfusions. This brought about a new era in cardiac surgery and the dawn of mechanical circulatory support. The critical difference between a VAD and TAH is that the native heart is left in situ during a VAD implantation, whereas implantation of the TAH requires excision of the left and right ventricles of the heart and replacing them with the TAH in the orthotropic position. The majority of patients in New York Heart Association (NYHA) class IV HF can be supported with isolated left VAD (LVAD) only—evidenced by the fact that more than 20,000 LVADs have been implanted worldwide. However, a minority of patients present with biventricular failure or other structural abnormalities of the heart precluding the placement of an isolated LVAD only. The TAH is an excellent therapeutic option under those circumstances. The TAH has been implanted in more than 1400 patients in North America, Europe, Russia, Turkey, Israel, and Australia with nearly all the implants being the SynCardia temporary Total Artificial Heart (SynCardia Systems, Inc.; Tucson, AZ, US).

The objective of this chapter is to give a brief review on the evolution and development of the TAH, its indications, clinical management, outcomes, and the current advances.

A BRIEF HISTORY

A clear start in the history of the TAH can be attributed to some of the scientific incentives advocated by the Kennedy administration in the 1960s. The National Institutes of Health initiated an artificial heart program for the development of partial and complete cardiac replacement devices. Parallel efforts progressed in Baylor College of Medicine in Texas, Cleveland Clinic, Pennsylvania State University, and University of Utah, creating a global race with research programs in the United States, Japan, West Germany, East Germany, Czechoslovakia, and the Soviet Union.

Willem Kolff and his trainees pioneered and laid the foundation for the development of TAH in its current form. The first reported TAH implantation was in a dog in 1957 by Dr Kolff and Tetsuzo Akutsu and circulation was supported for 90 minutes.¹ In 1969, Denton Cooley and Domingo Liotta performed the first human TAH implantation using the Liotta heart designed by Dr Liotta in a 47-year-old patient with ischemic cardiomyopathy, following a ventriculoplasty and an inability to separate from cardiopulmonary bypass. This device provided hemodynamic support for 64 hours. However, the early development of hemolysis and renal failure necessitated heart transplantation and the patient succumbed to sepsis 32 hours following the transplantation.² The media attention and controversy generated from this first human TAH implantation hampered its progress. After a long hiatus, a second TAH device (the Akutsu III developed by Dr Akutsu) was implanted in 1981 by Dr Cooley in a 36-year-old male patient in postcardiotomy shock following coronary artery bypass grafting. This procedure was complicated by renal failure and hypoxia and necessitated heart transplantation after 55 hours of TAH support. The patient expired 1 week later from sepsis.³ In 1962, William DeVries implanted the Jarvik 7 TAH (designed by Robert Jarvik) into Dr Clark, a 61-year-old retired dentist with nonischemic cardiomyopathy.⁴ While Dr Clark was supported for 112 days on this device, enthusiasm for further implantations of TAH was dampened because of the complex postoperative course, the adverse publicity generated by significant complications suffered by Dr Clark, and the advances in immunosuppression in the field of heart transplantation that resulted in superior results. After spluttering starts, and a few successes with the Jarvik 7 TAH,⁵ a trial of the CardioWest TAH (developed from Jarvik 7) was initiated in 1993 and concluded in 2002. Eighty-one patients were implanted with the device with 79% survival to transplantation and 70% 1-year survival. Based on the encouraging results of the CardioWest TAH (currently marketed as SynCardia TAH) as a bridge to transplantation, the device was approved by the United States Food and Drug Administration in 2004 and Centers for Medicare and Medicaid Services in 2008.

TECHNOLOGY

A VAD is a pump primarily designed to augment the function of the ventricle. However, with continued clinical use and more familiarity with these devices, its uses have also extended to serve as biventricular support devices, where both ventricles are supported with the devices or the ventricles are excised and completely replaced with 2 of these pumps as first described by O.H. Frazier in 2011.⁶

With advancements in the fields of technology, aerospace, and bioengineering, multiple research teams continued to work on the TAH. Fundamental engineering designs that have evolved are the pneumatic diaphragm pumps as in SynCardia and the centrifugal pump as in AbioCor. In the mid-1980s, the major issues related to the TAH were that artificial hearts were powered by washing-machine-sized pneumatic power sources derived from Alfa Laval milking machines and that 2 sizable catheters had to cross the body wall to carry the pneumatic pulses to the implanted heart, greatly increasing the risk of infection. These limitations were overcome by SynCardia, which designed a more compact compressor and power supply known as the Freedom portable driver. The AbioCor TAH does not require percutaneous cable for power supply; it has both internal and external components. The internal thoracic unit is powered via the transcutaneous energy transfer (TET) coil.

SYNCARDIA TOTAL ARTIFICIAL HEART

SynCardia TAH is an upgraded version of the TAH formerly known as Jarvik 7 (Symbion, Inc.; Salt Lake City), designed by Robert Jarvik. Collectively, research and implantation techniques were pioneered by Denton Cooley, Wihelm Kolff, Robert Jarvik, Clifford Kwan-Gett, William DeVries, Lyle Joyce, Jack Copeland, and Don Olsen. The device consists of 2 polyurethane ventricles each with a stroke volume of 70 mL and a total displacement volume of 400 cc in the chest cavity. It delivers a cardiac output of more than 7 to 9 L /min. The current version in clinical trial is smaller with a stroke volume of 50 mL.⁷ Traditionally, an anterior-posterior chest diameter (from the anterior border of T10 vertebra to the posterior table of the sternum) of at least 10 cm by computed tomography and a minimum body surface area of 1.7 m² were considered as absolute contraindication for the 70 mL device. Each chamber contains 2 mechanical single leaflet tilting disc valves (Medtronic Hall valves), a 27-mm inflow valve, and a 25-mm outflow valve to regulate direction of blood flow (a total of 4 mechanical valves). The 2 ventricles are pneumatically actuated by drivelines attached percutaneously to an external pump.

IMPLICATIONS

1. 
   

   Candidates for heart transplantation

   
   
   
   
   1. 
      

      Severe biventricular failure

      
      
   2. 
      

      Failing right ventricle while on a LVAD

      
      
   3. 
      

      Infiltrative diseases such as amyloidosis

      
      
   4. 
      

      End-stage hypertrophic cardiomyopathy

      
      
   5. 
      

      Anatomic reasons such as congenital heart disease with single ventricles or a corrected transposition with failing ventricles

      
      
   6. 
      

      Ventricular septal defects

      
      
   7. 
      

      Ventricular rupture

      
      
   8. 
      

      Cardiac tumors (rare)

   
   
2. 
   

   Severe clot burden in the left ventricle

   
   
3. 
   

   Malignant arrhythmias uncontrolled with surgical or medical options

   
   
4. 
   

   Failed allograft posttransplant

   
   
5. 
   

   Complex reoperative surgery

   
   
6. 
   

   Humanitarian reasons for patient as bridge to recovery from an acute cardiac failure and multiorgan failure, who would otherwise be a transplant candidate.

SURGICAL TECHNIQUE

A standard median sternotomy is performed. Two small incisions are made in the left upper abdomen and intramuscular tunnels are created through the left rectus muscle for the TAH drivelines. Mediastinal dissection and mobilization of the great vessels are minimized to maintain dissection planes for subsequent transplantation. The arterial cannulation is done via the aorta and venous cannulation via the superior and inferior vena cava; the aorta is then cross-clamped. The pulmonary artery and aorta are divided and separated at the level of the valve commissures. The left and right ventricles are excised, leaving a 1-cm rim of ventricular muscle around the mitral and tricuspid annulus, but the mitral and tricuspid valve leaflets are excised (Figure 41-1A-C). The coronary sinus is oversewn and the atrial septum is inspected for patent foramen ovale, which is repaired if present. The TAH atrial quick connectors are sutured to the respective valve annuli with 2-0 Prolene sutures over Teflon strips (Figure 41-1D). The aortic and pulmonary artery graft quick connectors are trimmed and sutured to the respective vessels with running 3-0 Prolene sutures. It is important that these are carefully cut to size to avoid both stretching and kinking. The pulmonary artery graft is longer than the aortic graft in order to reach over the aortic graft and connect to the artificial right ventricle.⁸ At time of implantation, extra efforts are made to maintain the avascular tissue planes; this dramatically simplifies re-entry for transplantation. The drivelines are passed through the intramuscular tunnels in the left rectus sheet with the Penrose drains. The TAH ventricles are attached to their respective atrial and arterial graft quick connects (Figure 41-2). Routine de-airing maneuvers are done and the left ventricle is started and the aortic cross clamp is removed. De-airing is confirmed by transesophageal echocardiography. The patient is often readily weaned off cardiopulmonary bypass as TAH support is increased. Usual post bypass TAH parameters are left drive pressure 180 to 200 mm Hg, right drive pressure 30 to 60 mm Hg, HR 100 to 120 bpm, and 50% systole. Vacuum is usually not initiated until the chest is closed.⁹ At re-entry for transplantation, during the initial implants, intense inflammatory reaction was observed in the pericardium and the surrounding structures and added to the complexity of the dissection process. To minimize this difficulty, the pericardium is reconstructed at the end of the procedure utilizing Gore-Tex surgical membrane (W.L. Gore & Associates; Flagstaff, AZ). In addition it was also noted that the mediastinum had collapsed around the TAH without leaving enough mediastinal space for the transplanted heart. To overcome this difficulty, a saline implant (Mentor smooth round, Mentor Worldwide LLC; Santa Barbara, CA) is placed at the former cardiac apex and inflated to 150 to 250 mL to maintain the space. This is removed at the time of heart transplantation along with the device and this extra space allows adequate room for the transplanted heart to function effectively.