Artificial Muscles and Soft Robotic Devices for Treatment of End-Stage Heart Failure

Medical soft robotics constitutes a rapidly developing field in the treatment of cardiovascular diseases, with a promising future for millions of patients suffering from heart failure worldwide. Herein, the present state and future direction of artificial muscle-based soft robotic biomedical devices in supporting the inotropic function of the heart are reviewed, focusing on the emerging electrothermally artificial heart muscles (AHMs). Artificial muscle powered soft robotic devices can mimic the action of complex biological systems such as heart compression and twisting. These artificial muscles possess the ability to undergo complex deformations, aiding cardiac function while maintaining a limited weight and use of space. Two very promising candidates for artificial muscles are electrothermally actuated AHMs and biohybrid actuators using living cells or tissue embedded with artificial structures. Electrothermally actuated AHMs have demonstrated superior force generation while creating the prospect for fully soft robotic actuated ventricular assist devices. This review will critically analyze the limitations of currently available devices and discuss opportunities and directions for future research. Last, the properties of the cardiac muscle are reviewed and compared with those of different materials suitable for mechanical cardiac compression.

Mitral valve repair for severe mitral valve regurgitation during left ventricular assist device implantation

BACKGROUND

The management of severe mitral regurgitation (MR) at the time of left ventricular assist device (LVAD) implantation is controversial. We adopted an approach of systematic repair of severe MR at the time of LVAD implantation and report our experience.

METHODS

We performed mitral valve repair (MVr) on 78 consecutive patients with severe MR undergoing LVAD implantation at our institution between 2013 and 2017. We compared data on these patients to 28 historical controls with severe MR from the immediate preceding period between 2011 and 2013 where the MR was not treated, using Cox modeling and propensity score methods. Median follow-up time was 17.7 months.

RESULTS

Patients who underwent MVr were younger than those who did not (non-MVr group) (55 vs 63 years; P = .006), but otherwise had similar preoperative characteristics. The incidence of 30-day mortality (2.6% vs 3.6%; P = .78) and other early major adverse events was similar in both groups. At 3 months, no patient in the MVr group had more than mild MR compared with 7 patients (29%) in the non-MVr group (P < .001). Cardiac catheterization done 3 to 6 months after surgery showed tendency toward greater reduction from preoperative pulmonary artery systolic pressure in the MVr group compared with the non-MVr group (-20 vs -13 mm Hg; P = .10). The cumulative incidence of readmission due to congestive heart failure at 2 years was lower in the MVr group than in non-MVr group (7.1% vs 19.7%; adjusted hazard ratio, 0.18; 95% confidence interval, 0.04-0.76; P = .02).

CONCLUSIONS

Concurrent MVr at the time of LVAD implantation can be done safely without increase in perioperative adverse events. MVr may be associated with better reduction in severity of MR and may have potential benefit in terms of reduction in readmissions for heart failure.

Valvular Regurgitation in a Biventricular Mock Circulatory Loop

Aortic regurgitation (AR), mitral regurgitation (MR), and tricuspid regurgitation (TR) after continuous-flow left ventricular assist device (LVAD) are common and may increase with prolonged LVAD support. The aim of this study was to simulate severe valvular regurgitation (AR, MR, and TR) within a 4-elemental pulsatile mock circulatory loop (MCL) and observe their impact on isolated LVAD and biventricular assist device (BiVAD) with HeartWare HVAD. Aortic regurgitation, MR, and TR were achieved via the removal of one leaflet from bileaflet mechanical valve from the appropriate valves of the left or right ventricles. The impact of alteration of LVAD pump speed (LVAD 2200-4000 RPM, right ventricular assist device [RVAD] 2400 RPM) and altered LVAD preload (10-25 mm Hg) was assessed. With each of the regurgitant valve lesions, there was a decrease in isolated LVAD pump flow pulsatility. Isolated LVAD provided sufficient support in the setting of severe MR or TR compared with control, and flows were enhanced with BiVAD support. In severe AR, there was no benefit of BiVAD support over isolated LVAD, and actual loop flows remained low. High LVAD flows combined with low RVAD flows and dampened aortic pressures are good indicators of AR. The 4-elemental MCL successfully simulated several control and abnormal valvular conditions using various pump speeds. Current findings are consistent with conservative management of MR and TR in the setting of mechanical support, but emphasize the importance of the correction of AR.