Editors' ChoiceCardiology

And the beat goes on

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Science Translational Medicine  20 Mar 2019:
Vol. 11, Issue 484, eaax2729
DOI: 10.1126/scitranslmed.aax2729

Abstract

A flexible, conductive, 3D-printed patch restores conduction after cardiac injury in a canine model.

The ventricles of the heart consist of cardiac myocytes that when functioning properly, rapidly conduct electrical impulses that activate their synchronous contraction. However, the heart is susceptible to many forms of injury that lead to necrosis of cardiac myocytes. Because cardiac myocytes cannot regenerate, severely injured or necrotic myocytes are replaced with nonconductive, noncontractile scar tissue. This type of structural abnormality can trigger arrhythmias by interrupting normal electrical conduction. These arrhythmias can progress to many dangerous outcomes, such as fibrillation and death. Current treatments include ablation of injured sites, which also damages healthy tissue and leads to additional scarring, or anti-arrhythmic medications, which have limited efficacy. In Pedrotty et al., the authors developed a solution by three-dimensional (3D) printing a conductive and flexible patch and implanting it over sites of ventricular injury. The patch consists mostly of nanofibrillated cellulose, a biomaterial with shear-thinning characteristics that are ideal for 3D printing. The nanofibrillated cellulose was mixed with single-walled carbon nanotubes to increase the conductance of the patch to levels matching native myocardium. To test their patches, the authors placed them over incisions made in the ventricles of canine hearts. By measuring the time of electrical activation at multiple locations on the ventricle, they saw that the patches successfully restored conduction across the incisions. This type of approach is advantageous because the treatment is localized to the site of injury, and the underlying tissue should not be adversely affected. This approach also has exciting translational potential because 3D printing is a rapid and inexpensive manufacturing technique that could easily be used in a hospital setting. Furthermore, the electrical properties and geometry of the patch can be customized on-demand for the patient and the characteristics of his/her specific injury. Pediatric and elderly patients would likely require very different patch parameters, for example. The patch is also cell-free, which increases the safety profile and further reduces the cost. However, further testing is needed to ensure that the patch itself does not induce arrhythmias long-term. The efficacy of this patch for larger and more realistic injuries also needs to be tested to fully determine its potential as a therapy for injured human hearts.

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