Ventricular radius reduction without resection: a computational analysis

Reducing a dilated left ventricle's radius by wedge resection lowers wall stress, improving performance. However, compliance falls, stroke volume improvement is limited, and, later, both functional deterioration and serious dysrhythmias are frequent. These all may result from loss of circumference, loss of contractile mass, and myocardial trauma, none of which would occur in geometric remodeling. One specific technique is bimeridianal restraint, which uses two indenting bars to remodel the left ventricle (LV) as two widely communicating "lobes" of reduced radius. Computational analysis of this technique, applied to the dilated ventricular dimensions of four pretransplant patients, showed that 20% radius reduction would be accomplished by two < or =18 mm wide bars, indenting the epicardium < or =8.3 mm with < or =6.4 mm greatest outward displacement. Projected stroke volume (SV) for the subject ventricles was then modeled and compared with projections for resected ventricles. Assuming that equally improved contractile fraction will follow equal radius reduction, however that reduction is accomplished, improvement is dramatic: if postresection remodeling SV were 1.0, 1.2, or 1.5 times baseline, then postgeometric remodeling SV would be 1.36+/-0.06, 1.66+/-0.05, or 2.14+/-0.04 times baseline, respectively. These results, preservation of contractile mass and circumferential length, complete reversibility, and minimal operative trauma, warrant study of implementing mechanical designs.