New continuous-flow total artificial heart and vascular permeability

The ongoing quest for the first total artificial heart as destination therapy

Many patients with end-stage heart disease die because of the scarcity of donor hearts. A total artificial heart (TAH), an implantable machine that replaces the heart, has so far been successfully used in over 1,700 patients as a temporary life-saving technology for bridging to heart transplantation. However, after more than six decades of research on TAHs, a TAH that is suitable for destination therapy is not yet available. High complication rates, bulky devices, poor durability, poor biocompatibility and low patient quality of life are some of the major drawbacks of current TAH devices that must be addressed before TAHs can be used as a destination therapy. Quickly emerging innovations in battery technology, wireless energy transmission, biocompatible materials and soft robotics are providing a promising opportunity for TAH development and might help to solve the drawbacks of current TAHs. In this Review, we describe the milestones in the history of TAH research and reflect on lessons learned during TAH development. We summarize the differences in the working mechanisms of these devices, discuss the next generation of TAHs and highlight emerging technologies that will promote TAH development in the coming decade. Finally, we present current challenges and future perspectives for the field.

Microvascular dysfunction in patients with diabetes after cardioplegic arrest and cardiopulmonary bypass

PURPOSE OF REVIEW

The purpose of the current review is to describe the changes of microvascular function in patients with diabetes after cardioplegic arrest and cardiopulmonary bypass (CPB) and cardiac surgery.

RECENT FINDINGS

Cardiac surgery, especially that involving cardioplegia and CPB, is associated with significant changes in vascular reactivity of coronary/peripheral microcirculation, vascular permeability, gene/protein expression, and programmed cell death, as well as with increased morbidity and mortality after surgical procedures. In particular, these changes are more profound in patients with poorly controlled diabetes.

SUMMARY

Because alterations in vasomotor regulation are critical aspects of mortality and morbidity of cardioplegia/CPB, a better understanding of diabetic regulation of microvascular function may lead to improved postoperative outcomes of patients with diabetes after cardioplegia/CPB and cardiac surgery.

Ventricular Assist Device Implantation Configurations Impact Overall Mechanical Circulatory Support System Thrombogenic Potential

Ventricular assist devices (VADs) became in recent years the standard of care therapy for advanced heart failure with hemodynamic compromise. With the steadily growing population of device recipients, various postimplant complications have been reported, mostly associated with the hypershear generated by VADs that enhance their thrombogenicity by activating platelets. Although VAD design optimization can significantly improve its thromboresistance, the implanted VAD need to be evaluated as part of a system. Several clinical studies indicated that variability in implantation configurations may contribute to the overall system thrombogenicity. Numerical simulations were conducted in the HeartAssist 5 (HA5) and HeartMate II (HMII) VADs in the following implantation configurations: 1) inflow cannula angles: 115° and 140° (HA5); 2) three VAD circumferential orientations: 0°, 30°, and 60° (HA5 and HMII); and 3) 60° and 90° outflow graft anastomotic angles with respect to the ascending aorta (HA5). The stress accumulation of the platelets was calculated along flow trajectories and collapsed into a probability density function, representing the "thrombogenic footprint" of each configuration-a proxy to its thrombogenic potential (TP). The 140° HA5 cannula generated lower TP independent of the circumferential orientation of the VAD. Sixty-degree orientation generated the lowest TP for the HA5 versus 0° for the HMII. An anastomotic angle of 60° resulted in lower TP for HA5. These results demonstrate that optimizing the implantation configuration reduces the overall system TP. Thromboresistance can be enhanced by combining VAD design optimization with the surgical implantation configurations for achieving better clinical outcomes of implanted VADs.

Calpain inhibition decreases inflammatory protein expression in vessel walls in a model of chronic myocardial ischemia

BACKGROUND

Emerging data suggest a link between calpain activation and the enhanced inflammatory response of the cardiovascular system. We hypothesize that calpain activation associates with altered inflammatory protein expression in correlation with the proinflammatory profile of the myocardium. Our pig hypercholesterolemic model with chronic myocardial ischemia was treated with calpain inhibitors to establish their potential to improve cardiac function.

METHODS

Yorkshire swine, fed a high cholesterol diet for 4 weeks then underwent placement of an ameroid constrictor on the left circumflex artery. Two weeks later, animals received either no drug (high-cholesterol control group, n = 8), a low dose of calpain inhibitors (0.12 mg/kg, n = 9), or a high dose of calpain inhibitors (0.25 mg/kg; n = 8). The high-cholesterol diet and calpain inhibitors were continued for 5 weeks, after which the pig was euthanized. The left ventricular myocardial tissue (ischemic and nonischemic) was harvested and analyzed for inflammatory protein expression. Data were statistically analyzed via the Kruskal-Wallis and Dunn post hoc test.

RESULTS

Calpain inhibitor treatment coincides with increased expression of IKB-α and decreased expression of macrophages, NFkB, IL-1, and tumor necrosis factor (TNF)-α in the ischemic myocardial tissue as compared with the control group. An NFkB array revealed decreased expression of IRF5, JNK1/2, JNK2, CD18, NFkB p65, c-Rel, Sharpin, TNF R1, TNF R2, and DR5 in the ischemic myocardium of the group treated with a high dose of calpain inhibitors compared with the control.

CONCLUSION

Calpain activation in metabolic syndrome is a potential contributor to cardiac dysfunction in metabolic disorders with ischemic background. We suggest that calpain inhibition downregulates NFkB signaling in the vessel walls, which might be useful for improving myocardial blood flow in ischemic conditions.