IMPROVING METHODS OF CHORDAL-SPARING MITRAL-VALVE REPLACEMENT .3. OPTIMAL DIRECTION FOR ARTIFICIAL CHORDAE

Background and aims of the study: The optimal direction to preserve ar tificial chordae tendineae (CT) during mitral valve replacement (MVR) is not known, especially in regard to the response to inotropic stimul ation which simulates exercise conditions. Methods: Using a non-distor ting isovolumic balloon technique, we compared left ventricular (LV) s ystolic and diastolic mechanics in II dogs in a control state (no chor dal sparing) and with four different methods of chordal preservation: posterior, anterior, oblique (anterior papillary muscle chordae direct ed anteriorly and others posteriorly, the direction which theoreticall y augments LV systolic twist), and counter-oblique (counter, chordae p reserved in directions opposite to oblique). Results: Before dobutamin e, Delta E(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 coun ter method, respectively). With dobutamine (3 mg/kg/min), Delta E(max) (mmHg/ml) was: 0.41 +/- 1.21, -0.13 +/- 0.75, 0.59 +/- 0.82, and -0. 34 +/- 0.71. Before dobutamine, Delta LV 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 Delta LV equilibrium volume (V-eq) eq was -1.2 +/- 3.8, -0.3 +/- 3.0, -0.7 +/- 2.7, and -0.2 +/- 3.5, whereas with dobutamine sigma(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 a nd counter by ANOVA; p = NS ( < 0.06) versus counter and posterior by ANOVA). Conclusions: The oblique method enhanced systolic LV function bath with and without dobutamine, while a tendency towards better dias tolic LV function (V-eq) was observed with dobutamine. The anterior me thod was next best in preserving systolic function, both with and with out dobutamine. LV diastolic function tended to deteriorate with dobut amine in the posterior group. Systolic function with the counter metho d deteriorated withe dobutamine. These results warrant further study i n an ejecting model to investigate LV systolic and diastolic mechanics with the oblique method of CT preservation, including interactions wi th LV systolic twist and diastolic recoil.