Original article
Adult cardiac
Material Properties of CorCap Passive Cardiac Support Device

https://doi.org/10.1016/j.athoracsur.2012.07.036Get rights and content

Background

Myocardial function deteriorates during ventricular remodeling in patients with congestive heart failure (HF). Ventricular restraint therapy using a cardiac support device (CSD) is designed to reduce the amount of stress inside the dilated ventricles, which in turn halts remodeling. However, as an open mesh surrounding the heart, it is unknown what the mechanical properties of the CSD are in different fiber orientations.

Methods

Composite specimens of CorCap (Acorn Cardiovascular, Inc, St. Paul, MN) CSD fabric and silicone were constructed in different fiber orientations and tested on a custom-built biaxial stretcher. Silicone controls were made and stretched to detect the parameters of the matrix. CSD coefficients were calculated using the composite and silicone matrix stress-strain data. Stiffness in different fiber orientations was determined.

Results

Silicone specimens exerted a linear behavior, with stiffness of 2.57 MPa. For the composites with 1 fiber set aligned with respect to the stretch axes, stiffness in the direction of the aligned fiber set was higher than that in the cross-fiber direction (14.39 MPa versus 5.66 MPa), indicating greater compliance in the cross-fiber direction. When the orientation of the fiber sets in the composite were matched to the expected clinical orientation of the implanted CorCap, the stiffness in the circumferential axis (with respect to the heart) was greater than in the longitudinal axis (10.55 MPa versus 9.70 MPa).

Conclusions

The mechanical properties of the CorCap demonstrate directionality with greater stiffness circumferentially than longitudinally. Implantation of the CorCap clinically should take into account the directionality of the biomechanics to optimize ventricular restraint.

Section snippets

Specimen Construction

In contrast to biological tissues being routinely tested on biaxial stretching systems, the CorCap CSD fabric has an open mesh structure that is not homogeneous and uniform. Therefore, if the CSD is tested alone, an uneven distribution of forces results, which in turn leads to a large amount of shear stress and deformation of the specimens. This open air mesh makes determination of mechanical properties using standard tensile testing methods unreliable without the development of additional

Results

Cauchy stress/Green strain curves for silicone specimens are depicted in Fig 3. The mechanical behavior of silicone specimens was completely linear as expected. It was consistent among the 4 different specimens as well as between the 2 orthogonal directions for each individual specimen, with an average stiffness of 2.57 MPa. Silicone specimens were stretched to a maximum extension of 10%, at which point the samples tore, mainly at the site of hook insertion. An average constant of 445 kPa was

Comment

Ventricular remodeling is 1 of the most important mechanisms of the progression of HF, independent of the patient's hemodynamic and neurohormonal status [4, 16, 17]. From the gross anatomic standpoint, alterations in left ventricular (LV) geometry leads to 4 major pathophysiologic consequences: LV chamber dilation, increased LV sphericity, LV wall thinning, and mitral valve incompetence [18]. As a result, LV wall stress dramatically increases during ventricular remodeling and places higher

References (29)

  • P.A. Chaudhry et al.

    Passive epicardial containment prevents ventricular remodeling in heart failure

    Ann Thorac Surg

    (2000)
  • A. Dell'Amore et al.

    Postmortem examination of the CorCap device: macroscopic and microscopic findings

    Cardiovasc Pathol

    (2007)
  • M. Jessup et al.

    Heart failure

    N Engl J Med

    (2003)
  • V.L. Roger et al.

    Heart disease and stroke statistics—2011 update: a report from the American Heart Association

    Circulation

    (2011)
  • Cited by (7)

    • Thermoplastic polycaprolactone elastomer for a 3D-printed pericardial scaffold in the treatment of dilated cardiomyopathy

      2022, Bioprinting
      Citation Excerpt :

      Intervention with a pericardial scaffold 3D printed from the TPE could be less costly and less invasive than LVADs, syncardia, or heart transplants. There is a growing body of evidence suggesting that pericardial scaffolds can afford the heart the necessary rest to sufficiently recover [17,18]. In a recent canine study, a biodegradable heart wrap showed higher left ventricular ejection fractions (LVEFs) versus non-biodegradable controls over 12 weeks [19].

    • Cardiac mechanostructure: Using mechanics and anisotropy as inspiration for developing epicardial therapies in treating myocardial infarction

      2021, Bioactive Materials
      Citation Excerpt :

      Two of the most extensively studied epicardial restraint devices are CorCap by Acorn and the HeartNet by Paracor. The Acorn CorCap, made by knitting polyester, features a unique geometry that provides bidirectional compliance, with greater support in the circumferential direction compared to the longitudinal direction (Fig. 1A) [130]. Preclinical studies in ovine models revealed improvement in global ventricular structure [127] and function [131] when treating tachycardia-induced HF as well as preserved cardiomyocyte length adjacent to infarcted myocardium when treating MI [132].

    • A bioresorbable biomaterial carrier and passive stabilization device to improve heart function post-myocardial infarction

      2019, Materials Science and Engineering C
      Citation Excerpt :

      Adequate conformity of mechanical support devices with the healthy myocardium in terms of mechanical properties is essential to successfully transfer stress from the infarcted myocardium and border zone while preserving the native cardiac contractility [4,6,22]. However, former whole heart passive restraint devices [4] are characterized by a much higher stiffness than the native myocardium at the end of the systole, such as 500 kPa [22], and as a result impair diastolic function of the right ventricle [64]. Chitsaz, Wenk [64] determined that the CorCap device has a minimal stiffness of 3 MPa in its cross-fiber direction.

    • Biventricular finite element modeling of the acorn CorCap cardiac support device on a failing heart

      2013, Annals of Thoracic Surgery
      Citation Excerpt :

      Both sets of angles are based on previous measurements of the CSD [13]. We recently derived a material property law sufficient to describe the Acorn CSD fabric and measured material constants in silicone embedded fabric samples with a biaxial stretcher [14]. Those findings were implemented into LS-DYNA using the material routine *MAT_091 [8].

    View all citing articles on Scopus
    View full text