The key here is the difference between a VAD and a TAH (total artificial heart). In a TAH, pulsatility is probably very important, especially at the capillary level where red blood cells are passing one at a time. The pulse seems to "thump" each cell through better than a constant force. Animal studies have been done where the entire heart was removed and a constant speed non-pulsatile pump was implanted. Proper organ function and blood oxygenation required about 20% higher flow. However, after a short period, the entire circulatory system started pulsing at approximately 40 beats per minute. This seems to be the "idle speed" of the circulatory system. This study is the same one you referenced in your post.
In a VAD however, the natural heart is still providing a pulse. The key is to not fight or interrupt this weak but steady pulse. Most diseased hearts still beat regularly, they just don't flow enough due to enlargement or reduced range of motion. There is evidence that pulsatile pumps which are out of sync with the natural heart can actually cause the heart to get worse (enlargen more and motion decrease). The key for a non-pulsatile pump is too have the right flow-pressure curve so that it pumps when the heart pumps, and it doesn't pump when the heart is filling. The DeBakey device does this very well.
So it all depends on the patient. A patient whose heart is completely disfunctional may do better with a pulsatile pump. Others may do worse. Patients who have received the DeBakey VAD have shown dramatic improvement in organ function, blood oxygenation, and energy level. The patient who made it to transplant went 75 days on the device. His health continually improved all the way to the transplant. What would have happened if he went much longer ? Who knows ?
It's all very confusing because there is so little data, especially for non-pulsatile pumps. Before the DeBakey VAD, there was no viable non-pulsatile pump which was long term implantable. The data is just coming in. If you find anything else on this issue, let me know. This obviously is one of the most important issues to resolve.
Regards,
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