Mitral annular size predicts Alfieri stitch tension in mitral edge-to-edge repair.
OBJECTIVE
Whilst increased 'Alfieri stitch' tension may reduce the durability of 'edge-to-edge' mitral repair, the factors affecting suture tension are unknown. In order to study hemodynamics and left ventricular (LV) and annular dynamics that determine suture tension, the central edge of the mitral leaflets was approximated with a miniature force transducer to measure leaflet tension (T) at the leaflet approximation point.


METHODS
Eight sheep were studied under open-chest conditions immediately after surgical placement of a force transducer and implantation of radiopaque markers on the left ventricle and mitral annulus (MA). Hemodynamic variables were altered by two caval occlusion steps (deltaV1 and deltaV2) and dobutamine infusion. Three-dimensional marker coordinates were obtained by simultaneous biplane videofluoroscopy to measure LV volume, MA area (MAA) and septal-lateral (SL) annular dimension throughout the cardiac cycle.


RESULTS
At baseline, peak Alfieri stitch tension (0.30 +/- 0.18 N) was observed 96 +/- 61 ms prior to end-diastole coincident with peak annular SL diameter (98 +/- 58 ms before end-diastole). Dobutamine infusion decreased suture tension (from 0.30 +/- 0.18 N to 0.20 +/- 0.12 N, p = 0.01), although peak systolic pressure increased significantly (138 +/- 19 versus 115 +/- 14 mmHg; p = 0.03). A regression model was fitted with the goal of interpreting the hemodynamic and geometric predictors of tension as their influence varied with time: Tt (N) = 0.1916 + 0.2115 x SL (cm) - 0.1996 x MAA/SL (cm2/cm) + ft x LVP (mmHg), where Tt is tension at any time during the cardiac cycle and ft is the time-varying coefficient of LVP.


CONCLUSIONS
Tension on the leaflets in the edge-to-edge repair is determined primarily by MA SL size, and paradoxically is lower when the contractile state is enhanced. This indicates that annular and/or LV dilatation increase stitch tension and may adversely affect durability of the repair if concomitant ring annuloplasty is not performed.
Timek
Tomasz A
TA
Department of Cardiothoracic Surgery, Stanford University School of Medicine, Stanford, CA 94305-5247, USA.
Nielsen
Sten L
SL
Lai
David T
DT
Tibayan
Frederick
F
Liang
David
D
Daughters
George T
GT
Beineke
Philip
P
Hastie
Trevor
T
Ingels
Neil B
NB
Miller
D Craig
DC
D000818:Animals; D002315:Cardiopulmonary Bypass; D002316:Cardiotonic Agents / Q000008:administration & dosage; D004280:Dobutamine / Q000008:administration & dosage; D006339:Heart Rate / Q000187:drug effects / Q000502:physiology; D019918:Heart Valve Prosthesis Implantation; D006352:Heart Ventricles / Q000503:physiopathology / Q000601:surgery; D008297:Male; D008943:Mitral Valve / Q000503:physiopathology* / Q000601:surgery*; D023421:Models, Animal; D008955:Models, Cardiovascular; D011237:Predictive Value of Tests; D012756:Sheep; D013223:Statistics as Topic; D013318:Stroke Volume / Q000187:drug effects / Q000502:physiology; D013536:Suture Techniques; D013599:Systole / Q000187:drug effects / Q000502:physiology; D013997:Time Factors; D017725:Ventricular Pressure / Q000187:drug effects / Q000502:physiology
D002316:Cardiotonic Agents; D004280:Dobutamine