Left ventricular external subannular plication: an indirect off-pump mitral annuloplasty method in a canine model

Abstract

Objective: Mitral annular dilatation in cardiomyopathy is due to left ventricular chamber enlargement. We hypothesized that the size of the mitral annulus could be “indirectly” reduced if the plicating sutures were placed externally into subannular myocardium . Methods In healthy mongrel dogs, an off-pump technique to create external subannular plication was designed and implemented. The sutures were placed directly into the myocardium below the atrioventricular groove. In 14 dogs, the sutures were tightened with tourniquets, and after a 30-minute observation period the hearts were arrested. Subsequently the mitral annular size was measured with the tourniquets still tight and then released. In 6 dogs, circumflex coronary blood flow, coronary blood flow reserve, and left ventricular systolic function were also measured during experiments. Results Subannular plication had no significant effect on the animals’ hemodynamic stability, and it did not generate any arrhythmias. Suture tightening effectively reduced postmortem mitral annular diameter and circumference by 17% (30.8 ± 0.4 mm and 96.8 ± 1.1 mm vs 25.6 ± 0.4 mm and 80.4 ± 1.1 mm, respectively, P < .001) and mitral annular area by 31% (747 ± 17 mm 2 vs 517 ± 14 mm 2, P < .001). Circumflex coronary blood flow (39.0 ± 7.9 mL/min vs 37.2 ± 7.2 mL/min, P not significant) and left ventricular systolic function (dP/dt max 1705 ± 237 mm Hg/s vs 1928 ± 330 mm Hg/s, P not significant) remained unchanged (n = 6). Conclusion In healthy hearts, subannular ventricular plication resulted in a significant indirect mitral annular size reduction without compromising circumflex coronary blood flow or left ventricular systolic performance.