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Pulmonary artery balloon counterpulsation for right ventricular failure. An experimental evaluation
Abstract:
Right ventricular (RV) failure frequently occurs in patients undergoing correction of congenital cardiac defects, as well as in other clinical settings. RV hypertrophy was created in 10 neonatal lambs by pulmonary artery (PA) banding. Twelve months later RV hypertrophy was present (RV weight/body weight = 2.71 +/- 0.31 gm/kg); RV systolic pressures were elevated (65 +/- 9 mm Hg) and the average gradient across the PA band was 38 +/- 9 mm Hg. RV failure was produced in all animals by performing a right ventriculotomy. Four unassisted (control) animals died shortly after separation from bypass. Six experimental animals underwent pulmonary artery balloon counterpulsation (PABCP). A Dacron graft anastomosed to the proximal PA served as a reservoir for a 40 ml intra-aortic balloon pump system. PABCP effectively reversed RV failure, low cardiac output, and systemic arterial hypotension. Periods with PABCP on and off in each animal were compared. PABCP increased cardiac output from 1.45 +/- 0.16 to 2.03 +/- 0.13 L/min (p less than 0.0001) and increased aortic systolic pressure from 78 +/- 7 to 99 +/- 6 mm Hg (p less than 0.0004). PABCP produced a significant reduction in RV peak systolic pressure from 56 +/- 5 to 41 +/- 3 mm Hg (p less than 0.0001). PA peak pressure distal to the band increased from 31 +/- 2 to 40 +/- 1 mm Hg (p less than 0.0001). Right atrial pressure decreased from 14 +/- 1 to 11 +/- 1 mm Hg (p less than 0.0001) with PABCP, and RV end-diastolic pressure fell from 15 +/- 1 to 11 +/- 1 mm Hg (p less than 0.0001). RV stroke work index increased 49% from 0.081 +/- 0.011 to 0.121 +/- 0.017 gm X m/kg/beat (p less than 0.01), and RV systolic pressure time index decreased 38% from 1140 +/- 79 to 710 +/- 65 mm Hg sec/min (p less than 0.0001). Thus PABCP in the presence of RV dysfunction can produce substantial improvement in RV function and in overall cardiac function and may prove clinically useful in managing patients in refractory RV failure.