Ventricular remodeling after cardiomyoplasty in heart failure sheep: Passive and dynamic effects

Background. Recent reports claim that cardiomyoplasty (CMP) has a girdling effect on the left ventricle, to prevent dilatation and functional deterior ation, but the mechanism of its long-term effects on the native heart is no t known. We compared the relative role of CMP's active squeezing and passiv e girdling in chronically failing hearts. Methods. After induction of stable heart failure (Left ventricular ejection fraction = 27% +/- 7%) by staged coronary microembolization, CMP was perfo rmed in 11 of 18 sheep. After g weeks pacing training of the Iatissimus dor si muscle (LDM), cardiac assist was begun with 1:2 synchronous bursts in 6 sheep (d-CMP, n = 6), and the LDMinthe passive group (p-CMP, n = 5) remaine d unstimulated. Four (base line) and 30 weeks after induction of heart fail ure, the pressure-volume relationship was derived. Results. After 30 weeks in d-CMP the slope (E-max) of the end-systolic pres sure-volume relationship increased by 66% +/- 55% (p < 0.05) and external w ork efficiency by 48% +/- 41% (p < 0.01). In the passive CMP and control gr oups, slope and external work efficiency were unchanged. Conversely, left v entricular end-diastolic volume decreased (-14% +/- 12%, p < 0.05) in the d ynamic CMP group compared with a static course in the passive CMP group (3% +/- 10%, p > 0.05) and an increase (18% +/- 15%, p < 0.05) in controls. Conclusions. Dynamic CMP improved native heart's contractility and external work efficiency. In addition, whereas passive CMP has simply a girdling ef fect, dynamic CMP also induces reverse left ventricular chamber remodeling. (Ann Thorac Surg 2000;70:2102-6) (C) 2000 by The Society of Thoracic Surge ons.