Quantification of mechanical stabilization for the performance of off-pump coronary artery surgery

Introduction: Our objective was to analyze the motion of a coronary artery in 3-dimensional (3-D) space and to quantify the stabilization afforded by a mechanical arm using 3-D digital sonomicrometry. Methods: The left anterior descending coronary artery (LAD) was exposed in swine (n = 7) via sternotomy. A 2-mm sonomicrometry crystal was sutured to the LAD, and an acrylic (Plexiglas) ring with 3 2-mm crystals fixed in an equilateral triangle was placed in the oblique pericardial sinus. Sonomicrometry measurements were obtained before and 10 minutes after placement of a stabilizing arm. Traces were analyzed for motion and velocity on a beat-to-beat basis in the x, y, and z planes by means of triangulation theory. Excursion was defined as the average maximum observed distance between LAD Cartesian positions p(k) = [px(k),py(k),pz(k)] over a beat such that the Excursion = max(j,k in beat) sqrt {[px(j) - px(k)]2 + [py(j) - py(k)]2 + [pz(j) - pz(k)]2}. The maximum and the average of the Cartesian velocity magnitude, v = sqrt[vx(2) + vy(2) + vz(2)], were also calculated. Results: Analysis of the LAD motion in planar space demonstrated a biphasic pattern in all 3 planes that appeared to be stable through the duration of the data acquisition period. The stabilizer dampened the motion of the LAD to a monophasic pattern and reduced the total distance traveled by the LAD crystal in all 3 planes. Stabilization resulted in a significant reduction of excursion, the maximum Cartesian velocity, and the average Cartesian velocity of the LAD. Conclusions: This method allows the precise quantification of LAD artery motion in 3-D space before and after the application of a stabilizing arm. We have demonstrated a significant reduction in the complexity of motion, the degree of motion in planar space, and the velocity of the LAD after application of a stabilizer.