Implantable Extra-Cardiac Soft Robotic Sleeve for Ventricular Assist in Heart Failure Patients
Introduction. Heart failure is characterized by the impairment of cardiac myocytes to intrinsically contract – leading to a reduction in the efficiency of stroke volume, and ultimately cardiac output1. Ventricular assist devices (VADs) are currently used to mechanically assist a failing heart as a method to prolong life while awaiting transplantation, or often as a life-long therapy for the remainder of the patient’s life2. Implantable soft robotic sleeves are under investigation as an improved upon iteration of VADs, with the goal of maximizing cardiac output while minimizing the coagulation risks of VADs. The soft robotic sleeve consists of actuators with recoiling ability, coupled to the heart, leading to synchronized beating and improved diastolic filling2. Methods. The soft robotics sleeve is fabricated using a thermoforming process to form the actuators in circumferential and helical patterns. The actuators are then combined into a 2D laminate by selective bonding between thin silicone sheets. The result is a flat monolayer device that conforms to the epicardial surface of the heart3. A custom control and instrumentation system was developed to implement timing schemes to optimize the actuation sequence by monitoring and recording physiological parameters such as heart rate, pulmonary artery pressure and flow rate, ascending aortic pressure and flow rate2. In vivo studies were conducted on a 70 kg swine to test three hypotheses4. Results. The first hypothesis confirms that mechanical coupling between the actuator and heart improves cardiac output4. The experimental results demonstrate that under every timing condition tested, coupling of the actuators to the ventricle significantly improved aortic and pulmonary output4. The second hypothesis correlates a longer systolic actuation period to improving cardiac function with coupling4. The mean aortic and pulmonary flow rates positively correlate with longer systolic actuation time conditions when the soft robotic device is coupled to the heart4. The third hypothesis analyzes the effect of actuation contraction rate on cardiac output4. The slowest actuator contraction rate significantly augmented aortic and pulmonary flow compared to the faster rates of contraction4. Conclusions. The results highlight some important trends and show the benefit of soft robotic sleeves in assisting heart failure. Future studies will explore different actuation strategies for left and right ventricles to independently optimize performance. The next phase will also explore minimally invasive approaches combined with pericardial preservation and limited myocardial trauma.
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