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(Circulation. 1995;92:458-466.)
© 1995 American Heart Association, Inc.

Articles

Left Ventricular Function, Twist, and Recoil After Mitral Valve Replacement

Abe DeAnda, Jr, MD; Masashi Komeda, MD, PhD; Srdjan D. Nikolic, PhD; George T. Daughters, II, MS; Neil B. Ingels, PhD; D. Craig Miller, MD

From the Department of Cardiovascular and Thoracic Surgery, Stanford (Calif) University School of Medicine (A.D., M.K., D.C.M.); the Cardiac Surgery Section, Department of Veterans Affairs Medical Center, Palo Alto, Calif (D.C.M.); and the Research Institute of the Palo Alto Medical Foundation, Palo Alto, Calif (S.D.N., G.T.D., N.B.I.).

Correspondence to D. Craig Miller, MD, Department of Cardiovascular and Thoracic Surgery, Falk Cardiovascular Research Center, Stanford University School of Medicine, Stanford, CA 94305-5247.

Background Preservation of the mitral subvalvular apparatus during mitral valve replacement (MVR) has become more popular, in part because of the clinically and experimentally demonstrated more optimal left ventricular (LV) performance after surgery; the mechanisms responsible for this beneficial influence, however, have not been clearly elucidated.

Methods and Results Fourteen dogs underwent placement of 26 myocardial markers into the LV and septum. One week later, the animals were studied while awake, sedated, and atrially paced (120 beats per minute) both under baseline conditions and after inotropic stimulation (calcium). The animals then underwent MVR and were randomized into either chord-sparing (MVR-Intact) or chord-severing (MVR-Cut) techniques. Two weeks later, the animals were studied under the same conditions. LV systolic function was assessed by the slope of the end-systolic pressure-volume relation (E_es); early LV diastolic filling was analyzed by the pressure-time constant of relaxation (). The instantaneous longitudinal gradient of torsional deformation for the LV (twist) was also calculated, as were the changes in twist with respect to time during systole and early diastole (LV recoil). Intergroup comparison showed a trend toward increased contractility (E_es, P=.061, before versus after MVR), as well as faster relaxation for the MVR-Intact group. Concurrent analysis of LV systolic function and the rate of systolic twist revealed a significant inverse relation, which disappeared after MVR when the chordae were severed.

Conclusions These observations suggest that the mitral subvalvular apparatus acts as a modulator of LV systolic torsional deformation into LV pump (or ejection) performance.

Key Words: ventricles • mechanics • valves • torsion

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