IMPROVING METHODS OF CHORDAL-SPARING MITRAL-VALVE REPLACEMENT .2. OPTIMAL TENSION FOR CHORDAL RESUSPENSION

Background and aims of the study: Although chordal-sparing mitral valv e replacement (MVR) is popular, the optimal tension for preserved or r eattached chordae tendineae (CT) or for synthetic (ePTFE) CT is unknow n. Methods: Changes in left ventricular (LV) systolic and diastolic fu nction in nine dogs with anterior CT preservation with different level s of end-diastolic chordal tension (0, 10, 20, 30, and 40 gm, measured by spring scale) were compared using an isovolumic double-balloon tec hnique. Results: LV function data at each level of tension were compar ed to control data using 0 gm of tension. Systolic function assessed a s E(max) (mmHg/ml) at 10, 20, 30, and 40 gm versus control was: 5.7 +/ - 2.6/4.9 +/- 2.7, 4.7 +/- 2.2/4.7 +/- 2.7, 4.8 +/- 3.1/4.7 +/- 2.8, a nd 5.0 +/- 3.5/5.1 +/- 2.9; Delta improvement from the control at 10 g m was larger than that at 20 gm (p < 0.05 by paired t-test). Diastolic function assessed as diastolic stiffness (S-d, mmHg/ml) at the same C T tensions versus control was: 0.56 +/- 0.23/0.56 +/- 0.34, 0.53 +/- 0 .30/0.57 +/- 0.37, 0.56 +/- 0.39/0.52 +/- 0.38, and 0.60 +/- 0.36/0.58 +/- 0.39; Delta S-d was smaller at 20 gm than at 30 gm (p = 0.05 by A NOVA). Conclusions: With chordal tension exceeding 10 gm, which is bar ely palpable, there was no additional enhancement in LV systolic funct ion compared to zero CT tension. V-eq was largest at the lowest tensio n; LV diastolic function (assessed as S-d) deteriorated with tensions of 30 gm or higher. The optimal end-diastolic tension of preserved CT should enhance systolic LV performance without adversely affecting dia stolic function; in this isovolumic model, minimal CT tension (10 gm) best met these goals. Excessive tension may negate the potential hemod ynamic benefits of chordal preservation during mitral valve replacemen t.