Original article
Adult cardiac
Effect of Adjustable Passive Constraint on the Failing Left Ventricle: A Finite-Element Model Study

https://doi.org/10.1016/j.athoracsur.2009.08.075Get rights and content

Background

Passive constraint is used to prevent left ventricular dilation and subsequent remodeling. However, there has been concern about the effect of passive constraint on diastolic left ventricular chamber stiffness and pump function. This study determined the relationship between constraint, diastolic wall stress, chamber stiffness, and pump function. We tested the hypothesis that passive constraint at 3 mm Hg reduces wall stress with minimal change in pump function.

Methods

A three-dimensional finite-element model of the globally dilated left ventricle based on left ventricular dimensions obtained in dogs that had undergone serial intracoronary microsphere injection was created. The model was adjusted to match experimentally observed end-diastolic left ventricular volume and midventricular wall thickness. The experimental results used to create the model were previously reported. A pressure of 3, 5, 7, and 9 mm Hg was applied to the epicardium. Fiber stress, end-diastolic pressure–volume relationship, end-systolic pressure–volume relationship, and the stroke volume–end-diastolic pressure (Starling) relationship were calculated.

Results

As epicardial constraint pressure increased, fiber stress decreased, the end-diastolic pressure–volume relationship shifted to the left, and the Starling relationship shifted down and to the right. The end-systolic pressure–volume relationship did not change. A constraining pressure of 2.3 mm Hg was associated with a 10% reduction in stroke volume, and mean end-diastolic fiber stress was reduced by 18.3% (inner wall), 15.3% (mid wall), and 14.2% (outer wall).

Conclusions

Both stress and cardiac output decrease in a linear fashion as the amount of passive constraint is increased. If the reduction in cardiac output is to be less than 10%, passive constraint should not exceed 2.3 mm Hg. On the other hand, this amount of constraint may be sufficient to reverse eccentric hypertrophy after myocardial infarction.

Section snippets

Finite-Element Model

A three-dimensional FE model of the globally dilated LV based on LV dimensions obtained in dogs that had undergone serial intracoronary microsphere injection was created [14, 15]. The model was adjusted to match experimentally observed end-diastolic LV volume [16] and midventricular wall thickness. The experimental results used to create the model were previously reported.

The geometry of this model consisted of an axially symmetric prolate spheroid with a focus of 2.25 cm and a

Results

Using our FE model we could describe detailed average wall stress distribution and the LV pump function associated with different levels of passive constraint on the failing canine LV.

Comment

The principal finding of this study is that both stress and cardiac output decrease in a linear fashion as the amount of passive constraint is increased. Although no amount of pump function reduction is desirable, a small decrease may be acceptable if it leads to reverse remodeling and improved systolic function. According to the numerical model, if the reduction in cardiac output is to be less than 10%, passive constraint should not exceed 2.3 mm Hg. At that level of constraint, mean

References (28)

  • R.K. Ghanta et al.

    Adjustable, physiological ventricular restraint improves left ventricular mechanics and reduces dilatation in an ovine model of chronic heart failure

    Circulation

    (2007)
  • A.S. Blom et al.

    Cardiac support device modifies left ventricular geometry and myocardial structure after myocardial infarction

    Circulation

    (2005)
  • A. Cheng et al.

    Passive ventricular constraint prevents transmural shear strain progression in left ventricle remodeling

    Circulation

    (2006)
  • J.J. Pilla et al.

    Ventricular constraint using the acorn cardiac support device reduces myocardial akinetic area in an ovine model of acute infarction

    Circulation

    (2002)
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