Improving methods of chordal-sparing mitral valve replacement - Part III: Optimal direction for artificial chordae

Background and aims of the study: The optimal direction to preserve artificial chordae tendineae (CT) during mitral valve replacement (MVR) is not known, especially in regard to the response to inotropic stimulation which simulates exercise conditions. Methods: Using a non-distorting isovolumic balloon technique, we compared left ventricular (LV) systolic and diastolic mechanics in 11 dogs in a control state (no chordal sparing) and with four different methods of chordal preservation: posterior, anterior, oblique (anterior papillary muscle chordae directed anteriorly and others posteriorly, the direction which theoretically augments LV systolic twist), and counteroblique (counter, chordae preserved in directions opposite to oblique). Results: Before dobutamine, ΔE(max) from the control was: 0.32 ± 0.82, 0.10 ± 0.43, 0.64 ± 1.07, and 0.51 ± 0.78 (anterior, posterior, oblique, and counter method, respectively). With dobutamine (3 mg/kg/min), ΔE(max) (mmHg/ml) was: 0.41 ± 1.21, -0.13 ± 0.75, 0.59 ± 0.82*, and -0.34 ± 0.71. Before dobutamine, ΔLV stiffness (S(d), mmHg/ml) was -0.01 ± 0.09, -0.02 ± 0.12, 0.02 ± 0.10, and 0.01 ± 0.12; with dobutamine it was 0.01 ± 0.09, 0.00 ± 0.15, 0.03 ± 0.15, and -0.06 ± 0.11. Similarly, before dobutamine ΔLV equilibrium volume (V(eq)) was -1.2 ± 3.8, -0.3 ± 3.0, -0.7 ± 2.7, and -0.2 ± 3.5, whereas with dobutamine ζ(eq) was -0.1 ± 1.1, -0.4 ± 0.8, 0.6 ± 1.7, and -0.4 ± 1.1. (Mean ± S.D.; *p = 0.005 posterior and counter by ANOVA; p = NS (< 0.06) versus counter and posterior by ANOVA). Conclusions: The oblique method enhanced systolic LV function both with and without dobutamine, while a tendency towards better diastolic LV function (V(eq)) was observed with dobutamine. The anterior method was next best in preserving systolic function, both with and without dobutamine. LV diastolic function tended to deteriorate with dobutamine in the posterior group. Systolic function with the counter method deteriorated with dobutamine. These results warrant further study in an ejecting model to investigate LV systolic and diastolic mechanics with the oblique method of CT preservation, including interactions with LV systolic twist and diastolic recoil.