Không ai trong số các TAHs sử dụng lâm sàng cho đến nay, sẽ phục vụ eflFectively như cấy ghép vĩnh viễn do yêu cầu bệnh nhân được buộc vào một giao diện điều khiển lái xe bên ngoài lớn, do đó nhốt bệnh nhân đến bệnh viện (Hình 2). Tuy nhiên, thế hệ tiếp theo của TAHs hiện đang được phát triển sẽ được cấy dưới da | 178 T. Mussivand . Hendry . Masters and . Keon None of the TAHs utilized clinically to date would serve effectively as a permanent implant due to the requirement that the patient be tethered to a large external driving console thus confining the patient to the hospital Figure 2 . However the next generation of TAHs currently being developed will be implantable and actuated electrically as opposed to pneumatically thus eliminating the need for a large external driving console and potentially allowing the recipients to be discharged from the hospital. Ventricular Assist Devices Ventricular Assist Devices VADs are connected in parallel to the native heart and pump all or part of the normal stroke volume. Unlike TAHs the native heart is left in place allowing for the potential of recovery of native heart function and possible removal of the device as well as maintaining the native heart neurohormonal control mechanisms. VADs can be classified into two major categories pulsatile devices and non-pulsatile or continuous flow devices. Clinical use of pulsatile VADs over 5800 reported cases has largely surpassed that of TAHs less than 350 cases and therefore offers the greatest hope in the near future for permanent use . Not only has there been significant clinical experience with these devices but certain devices are already being utilized in what could be considered a permanent application for extended durations and outside of the hospital . Successful utilization Figure 2. Artists representation of theJarvik Total Artificial Heart courtesy of CardioWest Technologies Tucson AZ . Permanent Mechanical Circulatory Support 179 Table 2. Clinical use of Ventricular Assist Devices VAD Device type Number of Patients Maximum Duration FDA Approval Status External Devices Berlin Heart Extracorporeal Console Driven 450 None Thoratec VAD Extracorporeal Console Driven 906 515 days Bridge to Transplant and Post-Cardiotomy Abiomed BVS-5000 Extracorporeal Console Driven
