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A New Device for Heart Failure: Quantitative Ventricular Restraint Reduces Transmural Myocardial Pressure in a Post-Infarction Ovine Model of Heart Failure
R. K. Ghanta, R. Umakanthan, A. Rangaraj, B. S. Kim, R. G. Laurence, J. D. Scott, J. A. Fox, L. H. Cohn*, F. Y. Chen. Brigham and Women's Hospital, Boston, MA,
Objective: Ventricular restraint is a promising therapeutic option for congestive heart failure. Its precise mechanism of action, however, is unclear. In this study, we evaluate the effect of quantitative ventricular restraint on transmural myocardial pressure (Ptm) in an ovine model of heart failure.
Methods: A novel fluid-filled balloon was developed to quantitatively measure and apply ventricular restraint to the entire epicardial surface. To produce heart failure, five ovine underwent D1/D2 coronary ligation. Six weeks post-infarction, all ovine developed dilated heart failure, characterized by a LV EF<35% and an 80% increase in LV EDV. Ventricular restraint levels were defined by the maximum pressure applied by the balloon to the epicardium (at end-diastole). We measured aortic, LV, and epicardial (balloon) pressure throughout the cardiac cycle at 4 different restraint levels: 0, 1/3 Pmax, 2/3 Pmax, and Pmax, where Pmax was defined as the restraint pressure that caused a 10 mmHg drop in mean aortic pressure. Ptm was defined as LV pressure minus epicardial pressure.
Results: Mean Ptm decreased significantly with increasing ventricular restraint levels.
Conclusions: Ventricular restraint decreases transmural myocardial pressure in an ovine model of heart failure, suggesting that decreased wall stress is one potential mechanism of this therapy. Quantitative ventricular restraint may allow for the optimization of therapy, whereby the reduction of wall stress is maximized and the effect on systemic hemodynamics is minimized.
Table 1| Restraint Level | Mean Arterial Pressure (mmHg) | Mean Ptm (mmHg) | | MAP | Δ from baseline | p | Ptm | Δ from baseline | p | | Baseline | 53.1 (+7.2) | | | 33.6 (+4.9) | | | | 1/3 Pmax (3mmHg) | 52.6 (+8.1) | -1% | =.56 | 30.1 (+5.4) | -11% | <.05 | | 2/3 Pmax (5mmHg) | 46.6 (+4.4) | -12% | <.05 | 26.9 (+5.5) | -20% | <.05 | | Pmax (8mmHg) | 43.1 (+6.9) | -19% | <.05 | 22.6 (+4.7) | -33% | <.05 |
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