CHRONIC COUNTERPULSATION WITH DESCENDING THORACIC AORTOMYOPLASTY IMPROVED CARDIAC-FUNCTION IN ANIMALS WITH HEART-FAILURE

Descending thoracic aortomyoplasty uses latissimus dorsi muscle for ex traaortic diastolic counterpulsation. We hypothesized that descending thoracic aortomyoplasty could improve ventricular function in dogs (n = 5) with heart failure. The left latissimus dorsi muscle was wrapped around the descending aorta and conditioned for 4 weeks with a burst s timulator (five pulses, 33 Hz, 28 bursts/min). Heart failure was induc ed by rapid ventricular pacing after conditioning. Left ventricular vo lume was measured with a conductance catheter. Left ventricular and ao rtic pressures were measured with a micromanometer. Mean diastolic blo od pressure, endocardial viability ratio, left ventricular peak pressu re, left ventricular end-diastolic pressure, stroke work, isovolumic r elaxation time constant, and the end-systolic pressure volume relation were measured at baseline (after heart failure) and with the descendi ng thoracic aortomyoplasty stimulated at 1:1. Contraction of the desce nding thoracic aortomyoplasty augmented mean diastolic blood pressure (62 +/- 4 to 71 +/- 3 mm Hg) and endocardial viability ratio (1.0 +/- 0.30 to 1.5 +/- 0.13) (p < 0.05). Left ventricular peak pressure (98 /- 4 to 88 +/- 3 mm Hg), left ventricular end-diastolic pressure (19 /-4 to 14 +/- 4 mm Hg), and stroke work (1048 +/- 124 to 743 +/- 80 mm Hg. cm3) (p < 0.05) were reduced. The end-systolic pressure volume re lation increased with descending thoracic aortomyoplasty stimulation ( 3.7 +/- 0.7 to 4.5 +/- 0.8 mm Hg/mL), and the isovolumic diastolic rel axation time constant significantly decreased (54 +/- 6 to 49 +/- 7 ms ec) (p < 0.05). We conclude that descending thoracic aortomyoplasty ca n provide diastolic counterpulsation and reduce stroke work in animals with heart failure. In addition, descending thoracic aortomyoplasty a ppears to have an effect on left ventricular contractility and diastol ic relaxation that is independent of its effect on ventricular loading parameters.