PHYSIOLOGICAL CONTROL OF CARDIAC ASSIST DEVICES

Total artificial hearts (TAHs) and biventricular assist devices (BVADs ) have varying levels of acceptance and reliability, and the research on both focuses on their control mechanisms. Efforts generally aim to achieve a response to physiologic demand and left/right output balance , and beneficial cardiac output (CO) and effective control mechanisms have been achieved by eliciting a Starling-like response to preload an d afterload. Such control mechanisms, however, generally base device o utput on a single parameter, such as the preload on the heart. Current TAHs and BVADs provide relatively fixed oxygen delivery to patients w ith large physiologically induced variations in oxygen consumption. Th is paper aims to document fluctuations in oxygen consumption that are normal in BVAD and TAH patients, identify a number of patient-generate d signals that reflect these fluctuations, and describe a multitiered control algorithm based upon these signals. Such a control system may offer better response times and more physiologic cardiac outputs. Ther e currently exists a microprocessor-based control mechanism that can b e adapted to control TAHs and BVADs using input from a variety of sens ors, and it can be found in modern implantable pulse generators (IPGs) . Today's pacemakers are capable of rate control and can run diagnosti c programs and store data that could be valuable in the evaluation of the patient's condition.