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(Circulation. 2007;115:1201-1210.)
© 2007 American Heart Association, Inc.

Cardiovascular Surgery

Adjustable, Physiological Ventricular Restraint Improves Left Ventricular Mechanics and Reduces Dilatation in an Ovine Model of Chronic Heart Failure

Ravi K. Ghanta, MD; Aravind Rangaraj, MD; Ramanan Umakanthan, MD; Lawrence Lee, MD; Rita G. Laurence, BS; John A. Fox, MD; R. Morton Bolman, III, MD; Lawrence H. Cohn, MD; Frederick Y. Chen, MD, PhD

From the Division of Cardiac Surgery (R.K.G., A.R., R.U., L.L., R.G.L., R.M.B., L.H.C., F.Y.C) and Division of Cardiac Anesthesia (J.A.F.), Brigham and Women’s Hospital, Harvard Medical School, Boston, Mass.

Correspondence to Frederick Y Chen, MD, PhD, Division of Cardiac Surgery, Brigham and Women’s Hospital, 75 Francis St, Boston, MA 02115. E-mail fchen{at}partners.org

Received October 20, 2006; accepted January 2, 2007.

Background— Ventricular restraint is a nontransplantation surgical treatment for heart failure. The effect of varying restraint level on left ventricular (LV) mechanics and remodeling is not known. We hypothesized that restraint level may affect therapy efficacy.

Methods and Results— We studied the immediate effect of varying restraint levels in an ovine heart failure model. We then studied the long-term effect of restraint applied over a 2-month period. Restraint level was quantified by use of fluid-filled epicardial balloons placed around the ventricles and measurement of balloon luminal pressure at end diastole. At 4 different restraint levels (0, 3, 5, and 8 mm Hg), transmural myocardial pressure (P_tm) and indices of myocardial oxygen consumption (MO₂) were determined in control (n=5) and ovine heart failure (n=5). Ventricular restraint therapy decreased P_tm and MO₂, and improved mechanical efficiency. An optimal physiological restraint level of 3 mm Hg was identified to maximize improvement without an adverse affect on systemic hemodynamics. At this optimal level, end-diastolic P_tm and MO₂ indices decreased by 27% and 20%, respectively. The serial longitudinal effects of optimized ventricular restraint were then evaluated in ovine heart failure with (n=3) and without (n=3) restraint over 2 months. Optimized ventricular restraint prevented and reversed pathological LV dilatation (130±22 mL to 91±18 mL) and improved LV ejection fraction (27±3% to 43±5%). Measured restraint level decreased over time as the LV became smaller, and reverse remodeling slowed.

Conclusions— Ventricular restraint level affects the degree of decrease in P_tm, the degree of decrease in MO₂, and the rate of LV reverse remodeling. Periodic physiological adjustments of restraint level may be required for optimal restraint therapy efficacy.

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