Surgical treatment of oligosymptomatic mitral valve incompetence

Objective: Despite improvements of the surgical technique in NYHA (III)-(IV ) mitral valve incompetence (MVI) postoperative longterm results remain poo r. As long-term results reflect primarily the ventricular function rather t han the quality of the surgical technique the contractile performance of is olated papillary muscles obtained from patients undergoing mitral valve rep lacement for MVI (n = 25) was analysed in detail. Methods: Muscle preparati ons (0.4 x 5.0 mm) obtained from left ventricular papillary muscles (NYHA ( I), n = 4; NYHA (II), n = 7; NYHA (III), n = 8; NYHA (IV), n = 6) were load ed for intracellular calcium measurements with FURA-2, stretched to optimal length (L-max) and electrically stimulated with frequencies ranging from 3 0 to 180 beats/min (b.p.m.) (10% above threshold, 37 degrees C, Krebs-Hense leit solution). Isometric force development and diastolic intracellular cal cium (measured by the 'ratio method'; excitation light: wavelengths alterna ting 340 and 380 nm, frequency: 250 Hz) were simultaneously recorded as a f unction of the stimulation frequency. Results: At 60 b.p.m. force developme nt was significantly higher in NYHA(I) myocardium (21.3 +/- 2.8 mN/mm(2)) t han in NYHA(III) myocardium (12.8 +/- 2.2 mN/mm(2)), (P < 0.0001). In NYHA( I) myocardium force rose with increasing stimulation frequency ('positive s taircase'). In contrast the stimulation frequency associated with maximum f orce was shifted towards lower frequencies in NYHA (II)-(IV) myocardium ('n egative staircase'). As compared with NYHA (I) myocardium diastolic intrace llular calcium was significantly elevated at 150 b.p.m. in NYHA (II)-(TV) m yocardium (P < 0.01). Conclusion: The data show, that severe impairment of contractile function ('negative staircase phenomenon', reduced force, eleva ted diastolic calcium) is present in MVI classified as NYHA (III)-(IV) that may explain the poor long-term results. Most interestingly the data argue for a significant impairment of myocardial function even in NYHA(II) MVI. T he results suggest an early surgical treatment of mitral valve incompetence as long as the myocardial function is normal (NYHA (I)) as (1) a reduced p erioperative risk, (2) improved long-term results, and(3)a higher probabili ty for mitral valve repair (instead of replacement) may be expected in thes e early stages of mitral valve disease. (C) 1999 Elsevier Science B.V. All rights reserved.