ISOLATED LEFT-VENTRICULAR MYOCYTE CONTRACTILITY IN PATIENTS UNDERGOING CARDIAC OPERATIONS

Background: Because of methods required for obtaining isolated left ve ntricular myocytes, evaluation of the contractile function of isolated left ventricular myocytes in normal human patients has been limited. Accordingly, the goal of the present study was to develop a means to i solate human left ventricular myocytes from small myocardial biopsy sp ecimens collected from patients undergoing elective coronary artery by pass operations and to characterize indices of myocyte contractile per formance. Methods: Myocardial biopsy specimens were obtained from the anterior left ventricular free wall of 22 patients undergoing coronary artery bypass operations. Myocytes were isolated from these myocardia l samples by means of a stepwise enzymatic digestion method and micro- trituration techniques. Isolated left ventricular myocyte contractile function was assessed by computer-assisted high-speed videomicroscopy under basal conditions and in response to beta-adrenergic receptor sti mulation with isoproterenol, Results: A total of 804 viable left ventr icular myocytes were successfully examined from all of the myocardial biopsy specimens with an average of 37 +/- 4 myocytes per patient. All myocytes contracted homogeneously at a field stimulation of 1 Hz with an average percent shortening of 3.7% +/- 0.1% and shortening velocit y of 51.3 +/- 1.3 mu m/s, After beta-adrenergic receptor stimulation w ith isoproterenol, percent shortening and shortening velocity increase d 149% and 118% above baseline, respectively (P < .05). Conclusion: Th e unique results of the present study demonstrated that a high yield o f myocytes could be obtained from human left ventricular biopsy specim ens taken during cardiac operations. These myocytes exhibited stable c ontractile performance and maintained the capacity to respond to an in otropic stimulus. The methods described herein provide a basis by whic h future studies could investigate intrinsic and extrinsic influences on left ventricular myocyte contractility in human beings.