STROKE OUTCOMES FOLLOWING IMPLANTATION OF THE CAR-DIOWEST TOTAL ARTIFICIAL HEART

Total artificial heart--concepts and clinical use

End-stage congestive heart failure remains the leading cause of death in the United States. Despite advances in medical treatment, it also remains the most common reason for admission to the hospital. The gold standard of treatment for the failing heart, orthotopic heart transplantation, is limited by a shortage of donor hearts. There are also a significant number of patients who are not transplant candidates due to comorbid conditions and/or inability to tolerate immunosuppressive therapy. To meet the need for this latter group, the medical field has embraced ventricular assist device (VAD) therapy to extend survival and improve quality-of-life for the end-stage cardiac patient. This therapy, however, has been currently limited to the failing left ventricle and is still fraught with complications that limit long-term and widespread use. The total artificial heart, as currently available with two devices, is rapidly becoming the treatment of choice for biventricular failure.

Total artificial hearts: bridge to transplantation

The CardioWest TAH was created and initially tested at the same time as the Thoratec, Novacor, and HeartMate devices. It was designed as a permanent artificial heart and was the first-ever mechanical circulatory device to be used as destination therapy. Twenty years have passed since that early experience. Pneumatic technology is still current and being developed as in existing or new implantable Thoratec VADs the pneumatic HeartMate, and the Abiomed BVS 5000 pumps. Portable pneumatic drivers have been available since 1982, and in recent times have allowed discharge to home of substantial numbers of patients, thus reducing the length of hospital stays and making mechanical device support less expensive to society and more tolerable to patients. Within months, a portable driver for the CardioWest will be available. The documented benefits of the CardioWest TAH include rescue of: critically ill patients with advanced heart failure; patients with biventricular failure especially those with significant right heart failure, elevated pulmonary vascular resistance, or pulmonary edema; patients with renal or hepatic failure secondary to low cardiac output; patients with massive myocardial damage such as those with post-\infarction VSD or irreversible cardiac graft rejection; patients with mechanical valves or native valve disease; and patients with intractable arrhythmias and heart failure. High device outputs with restoration of normal filling pressures result in high perfusion pressures that have led to dramatic recoveries, convalescence, and return to levels of activity compatible with normal life. The average device output with the CardioWest TAH is higher than any other approved or investigational device. The reason for this resides in design simplicity this device has the shortest and largest inflow pathway. Stroke, in the authors' own series, is rare with a linearized rate of 0.068 events per patient year. If the experiences of La Pitie and the University of Arizona are combined, there has been one stroke in 25 patient years (0.04 events/patient year). Serious infections have been rare (12% of patients). No clinical mediastinitis has occurred. Drivelines have healed in tightly and never caused an "ascending" infection. There has not been a case of device endocarditis. Using a broad definition of bleeding, including takeback reoperation for bleeding, bleeding more than 8 units in the first postoperative 24 hours or 5 units over any other 48-hour period, a 25% to 36% incidence has been documented. No cases of fatal exsanguination have resulted, as there have been with the HeartMate. The incidence of bleeding as an adverse event is about 17% lower than the rate reported for the HeartMate VE LVAD, and it is about the same as that reported for Novacor and for Thoratec. Implantation of this device is relatively easy and often done (with attending help) by the authors' residents. If one follows the guidelines for fitting the device, and takes the recommended advice for implantation, hemostasis is excellent and restoration of immediate cardiac function with high flows is nearly automatic. Use of a neopericardium of 0.1 mm EPTFE at the time of implantation assures atraumatic and relatively quick re-entry for transplantation and prevents the normal inflammatory mediastinal reaction that might be desirable in a destination application. In selected patients the CardioWest TAH is the device of choice for bridge to transplantation. When a portable driver becomes available, out of hospital management of CardioWest TAH patients will be feasible and consideration of use of this device for longer term applications, (e.g., "destination therapy,") will be reasonable. A wearable driver, even smaller than a portable, will improve quality of life and expand the patient population that may be therapeutically served with this system. In short, the CardioWest TAH has come nearly full circle. It was first used as a destination device. It has since been used as a bridge to transplantation in nearly 200 patients as the Jarvik-7/Symbion TAH and, since 1993, in over 225 patients as CardioWest. The results have improved with time. Thromboembolism and infection rates have been competitive with currently available devices. Device reliability and durability have been excellent. Survival rates have been very high in a group of perhaps the sickest patients to be supported with any pulsatile device. Pneumatic technology has improved with portability and miniaturization, and there is reason to believe that it will become even better. Application of modern manufacturing techniques to this very simple device raises the possibility of significant manufacturing cost reduction, in an era of prohibitive cost for other devices. All of this establishes the CardioWest as a valuable device for any program that is seriously interested in end-stage heart disease and a likely device for permanent use in appropriately selected patients.