EFFECTS OF PARTIAL LEFT VENTRICULECTOMY ON LEFT-VENTRICULAR GEOMETRY AND WALL STRESS IN EXCISED PORCINE HEARTS

Background and aims of the study: Partial left ventriculectomy (PLV, t he ''Batista procedure'') has received recent attention as a surgical treatment for patients with dilated cardiomyopathy and end-stage conge stive heart failure; however, the mechanisms responsible for the purpo rted short-term improvement in left ventricular (LV) function are poor ly characterized. This study examined the effects of PLV on three-dime nsional (3-D) LV geometry, wall stress and passive LV mechanics in exc ised porcine hearts. Methods: Thirty-three radio-opaque tantalum marke rs were placed into the LV wall of nine freshly excised, porcine heart s (arrested with cold crystalloid cardioplegia) to measure three dimen sional LV geometry and volume. Simultaneous biplane videofluoroscopic marker images and LV pressure (LVP) were obtained over a wide range of LV volumes generated with an intracavitary LV balloon. Measurements w ere repeated after excision of a diamond-shaped wedge of the lateral L V wall between the papillary muscles (mean: 8 x 3 x 2 cm; 10 +/- 2% of LV mass). Results: Following PLV, the ventricle assumed a more ellipt ical shape (LV eccentricity rose from 0.71 +/- 0.15 to 0.81 +/- 0.09, p < 0.01). Circumferential radius of curvature fell in the anterior, l ateral and posterior regions at the equatorial level (p < 0.01), while the posterior wall longitudinal radius of curvature increased at the basal, equatorial and apical levels (p < 0.01). No change in the longi tudinal radius of curvature was observed in the other walls. These cha nges were associated with a fall in average equatorial LV wall stress from 176 +/- 34 to 159 +/- 30 kdyne/cm(2) (p < 0.02). Myocardial stiff ness (slope of the LV stress-strain relation) fell from 12.4 +/- 4.0 t o 10.0 +/- 3.4 (p < 0.004), indicating lower global LV wall stress at any given LV size. Conclusions: In flaccid porcine hearts, the left ve ntricle became more elliptical and chamber size decreased after PLV, w hich resulted in lower regional LV wall stress and myocardial stiffnes s. LV ellipticalization may improve systolic LV performance by decreas ing regional LV afterload (e.g. systolic wall stress), which would the reby lower myocardial oxygen consumption and improve LV pump efficienc y.