AUTOGENOUS CARDIAC ASSIST WITH CHRONIC DESCENDING THORACIC AORTOMYOPLASTY

Alternative surgical treatments to orthotopic cardiac transplantation are needed for patients with heart failure. We hypothesized that desce nding thoracic aortomyoplasty with conditioned (fatigue-resistant) lat issimus dorsi muscle could provide diastolic augmentation that would i mprove left ventricular function. Six mongrel dogs were studied. The l eft latissimus dorsi muscle was wrapped clockwise around the descendin g thoracic aorta. Left ventricular volume was measured with a conducta nce catheter. Aortic and left ventricular pressures were measured with a micromanometer. The following were measured after descending thorac ic aortomyoplasty at baseline and with the descending thoracic aortomy oplasty stimulated 1:1 with the heart rate: stroke work, stroke volume , left ventricular peak pressure, maximum rate of increase of left ven tricular pressure, diastolic relaxation time constant, peak rate of pr essure decay, left ventricular end-diastolic pressure, endocardial via bility ratio, mean diastolic aortic pressure, peak diastolic aortic pr essure, and time-averaged aortic diastolic velocity. Before data colle ction, the latissimus dorsi was stimulated (5 pulses delivered at 33 H z at a rate of 28 per minute for 4 weeks) with burst stimulation to in duce fatigue resistance. Results (expressed as the mean +/- the standa rd error of the mean) showed significant improvement in the indices of ventricular contractility (maximum rate of increase of left ventricul ar pressure, 1,217 +/- 83 to 1,414 +/- 91 mm Hg/s) and diastolic relax ation mechanics (peak rate of pressure decay, 1,152 +/- 92 to 1,282 +/ - 79 mm Hg/s; diastolic relaxation time constant, 43 +/- 2 to 38 +/- 2 ms). Significant differences were noted with stimulation at 1:1 in th e endocardial viability ratio (0.90 +/- 0.05 to 1.14 +/- 0.04), an ind ex of myocardial oxygen supply. Systemic diastolic pressures (peak dia stolic aortic pressure, 95 +/- 6 to 107 +/- 5 mm Hg; mean diastolic ao rtic pressure, 92 +/- 6 to 102 +/- 6 mm Hg) and the time-averaged aort ic diastolic velocity (1.5 +/- 0.6 to 3.3 +/- 1.0 m/s) increased signi ficantly. We conclude that descending thoracic aortomyoplasty stimulat ion with conditioned latissimus dorsi muscle can improve indices of ve ntricular contractility, diastolic relaxation mechanics, diastolic pre ssures, and diastolic aortic velocity in the nonfailed canine heart. F urther studies with the chronic failed heart model are required.