Ventricle-specific epicardial pressures as a means to optimize direct cardiac compression for circulatory support: A pilot study

Figures

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  Fig 1. Human biventricular models. Examples of human biventricular models reconstructed from a CT scan (A); an echocardiogram scan (B); and a computer rendering of a passive human biventricular model (C) designed with these reported data.

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  Fig 2. Stress-strain curve of the heart tissue data overlay with Yeoh 3rd model.

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  Fig 3. Computer renderings of a biventricular model. The BiV model surface divided into six sections for proper boundary and loading conditions applications (A: Fixed top surface, B, C: RVP, D: LVP, E: LVEP, F: RVEP), and generated into a mesh model (G) for cavity extractions before (H) and after (I) deformations (J).

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  Fig 4. Stroke volumes and ejection fractions of the BiV model after four-case cardiac compressions. A: Stroke volumes (a) and ejection fractions (b) of Case 1 where uniform EPs were applied to both ventricles with zero afterload; B: Stroke volumes (a) and ejection fractions (b) of Case 3 where uniform EPs were applied to both ventricles with end-systolic afterloads; C: Cardiac outputs of Case 2 where separate EPs were applied to LV (a) and RV (b) with zero afterload; and D: Cardiac outputs of Case 4 where separate EPs were applied to LV (a) and RV (b) with end-systolic afterloads.

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  Fig 5. The BiV model (A) Deformations after four-case cardiac compressions. Case 1: A uniform EP of 5 mmHg (B), 10 mmHg (C), and 25 mmHg (D) applied to both ventricles with zero afterload; Case 2: Different combinations separate EPs (5 mmHg LVEP and 2 mmHg RVEP (E), 30 mmHg LVEP and 4 mmHg RVEP (F), 60 mmHg LVEP and 10 mmHg RVEP (G)) applied to both ventricles with zero afterload; Case 3: A uniform EP of 0 mmHg (H), 30 mmHg (I), and 60 mmHg (J) applied to LV and RV with end-systolic afterloads; and Case 4: Different combinations separate EPs (0 mmHg LVEP and 0 mmHg RVEP (K), 100 mmHg LVEP and 10 mmHg RVEP (L), 160 mmHg LVEP and 25 mmHg RVEP (M)) applied to LV and RV with end-systolic afterloads. Deformation units are in mm.

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  Fig 6. The RVEP-to-LVEP ratio for zero and end-systolic afterloads. The relationship between applied LVEPs and RVEPs to induce the similar amounts of LVEFs and LVEFs (Δ <5%) for ventricles with zero (A) and end-systolic (B) afterloads.

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  Fig 7. Stress, strain, and energy experienced by the BiV model for Case 4. Local maximum (σ1), middle (σ2) and minimum (σ3) principal stresses and maximum (ε1), middle (ε2) and minimum (ε3) principal strains and total strain energy were solved using ANSYS Workbench for Case 4 where separate LVEP and RVEP were applied to the LV and RV loaded with end-systolic AoP and PAP, respectively. Principal stresses (A) initially dropped before rising due to the higher ventricular afterload compared to epicardial compressive pressure (D). Similarly, principal strains (B) dropped until the EP exceeded afterload pressures (E). Strain locale transitioned from the fixed top surface (B) to the middle of the RV wall (C) as EP increased. Total strain energy of the BiV model exhibited an exponential trend due to the hyperelastic material property of the model (F).