Dynamic descending thoracic aortomyoplasty: Comparison with intraaortic balloon pump in a model of heart failure

Abstract

Descending thoracic aortomyoplasty (DTA) uses the latissimus dorsi muscle to compress the proximal descending thoracic aorta as an autogenous diastolic counterpulsator. We studied the hypothesis that DTA could confer hemodynamic benefits equivalent to those yielded by an intraaortic balloon pump (IABP) in dogs (n = 7) with heart failure. The left latissimus dorsi muscle was wrapped around the proximal thoracic aorta and subsequently electrically conditioned to induce fatigue resistance. Heart failure was produced by rapid ventricular pacing after muscle conditioning. Data were collected under three conditions: (1) after the induction of heart failure; (2) with the 20-mL IABP at 1:1; and (3) with the DTA stimulated at 1:1. Effective diastolic counterpulsation was achieved with both the IABP and the DTA. The mean diastolic aortic pressure increased from 66 ± 5 mm Hg at baseline to 90 ± 4 mm Hg with the IABP and to 75 ± 4 mm Hg with the DTA. The left ventricular peak and end-diastolic pressures decreased with IABP (95 ± 5 mm Hg versus 88 ± 4 mm Hg and 16 ± 4 mm Hg versus 12 ± 4 mm Hg, respectively; p < 0.05) and with DTA (95 ± 5 mm Hg versus 87 ± 4 mm Hg and 16 ± 4 mm Hg versus 12 ± 4 mm Hg, respectively; p < 0.05). Counterpulsation with the IABP did not change the end-systolic pressure-volume relationship or the time constant for diastolic relaxation, whereas the DTA increased the endsystolic pressure-volume relationship (3.2 ± 0.6 mm Hg/mL versus 4.0 ± 0.7 mm Hg/mL; p < 0.05) and decreased the time constant for diastolic relaxation (49 ± 5 msec versus 45 ± 6 msec; p < 0.05). These data show that DTA using conditioned skeletal muscle can provide diastolic counterpulsation in animals with compromised cardiac function. In addition, the procedure appears to have an effect on left ventricular contractility that is independent of its effects on cardiac preload and afterload.