DYNAMIC DESCENDING THORACIC AORTOMYOPLASTY - COMPARISON WITH INTRAAORTIC BALLOON PUMP IN A MODEL OF HEART-FAILURE

Descending thoracic aortomyoplasty (DTA) uses the latissimus dorsi mus cle to compress the proximal descending thoracic aorta as an autogenou s diastolic counterpulsator. We studied the hypothesis that DTA could confer hemodynamic benefits equivalent to those yielded by an intraaor tic balloon pump (IABP) in dogs (n = 7) with heart failure. The left l atissimus 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 th e 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 w as 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 w ith the IABP and to 75 +/- 4 mm Hg with the DTA. The left ventricular peak and end-diastolic pressures decreased with IABP (95 +/- mm Hg ver sus 88 +/- 4 mm Hg and 16 +/- 4 mm Hg versus 12 +/- 4 mm Hg, respectiv ely; 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). Counter pulsation with the IABP did not change the end-systolic pressure-volum e relationship or the time constant for diastolic relaxation, whereas the DTA increased the end-systolic pressure-volume relationship (3.2 /- 0.6 mm Hg/mL versus 4.0 +/- 0.7 mm Hg/mL; p < 0.05) and decreased t he time constant for diastolic relaxation (49 +/- 5 msec versus 45 +/- 6 msec; p < 0.05). These data show that DTA using conditioned skeleta l muscle can provide diastolic counterpulsation in animals with compro mised cardiac function. In addition, the procedure appears to have an effect on left ventricular contractility that is independent of its ef fects on cardiac preload and after-load.