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, the 'Batista procedure') has received recent attention as a surgical treatment for patients with dilated cardiomyopathy and end-stage congestive heart failure; however, the mechanisms responsible for the purported short-term improvement in left ventricular (LV) function are poorly characterized. This study examined the effects of PLV on three-dimensional (3-D) LV geometry, wall stress and passive LV mechanics in excised porcine hearts. Methods: Thirty-three radio-opaque tantalum markers were placed into the LV wall of nine freshly excised, porcine hearts (arrested with cold crystalloid cardioplegia) to measure three dimensional LV geometry and volume. Simultaneous biplane video-fluoroscopic marker images and LV pressure (LVP) were obtained over a wide range of LV volumes generated with an intracavitary LV balloon. Measurements were repeated after excision of a diamond-shaped wedge of the lateral LV 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 elliptical 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, lateral 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 longitudinal radius of curvature was observed in the other walls. These changes were associated with a fall in average equatorial LV wall stress from 176 ± 34 to 159 ± 30 kdyne/cm² (p<0.02). Myocardial stiffness (slope of the LV stress-strain relation) fell from 12.4 ± 4.0 to 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 ventricle became more elliptical and chamber size decreased after PLV, which resulted in lower regional LV wall stress and myocardial stiffness. LV ellipticalization may improve systolic LV performance by decreasing regional LV afterload (e.g. systolic wall stress), which would thereby lower myocardial oxygen consumption and improve LV pump efficiency.