Feasibility of closed-chest left ventricular bypass using unilateral retrograde transpulmonary flow

A method for closed-chest left heart bypass using retrograde unilateral transpulmonry blood flow originating from the left atrium and retrieved by a cuffed cannula wedged in a pulmonary artery branch is described. Technical feasibility and physiological implications were tested in 12 anesthetized sheep and 4 awake calves. Retrograde transpulmonary flow showed a curvilinear relationship to the left atrial pressure, with the highest rate of rise occurring when left atrial pressure approached levels of pulmonary edema (25 to 35 mm Hg); at this point retrograde transpulmonary flow became equal to control cardiac output. The intervention and the bypass were well tolerated for short periods by these healthy animals. The possible advantages of the method are discussed, with emphasis on self-regulation of bypass flow by the filling resistance of the left ventricle.