Myocardial mechanics, energetics, and hemodynamics during intraaortic balloon and transvalvular axial flow hemopump support with a bovine model of ischemic cardiac dysfunction

Unlike the mechanisms of intraaortic balloon pump (IABP) support, the mecha nisms by which transvalvular axial flow Hemopump (HP) support benefit dysfu nctional myocardium are less clearly understood. To help elucidate these me chanisms, hemodynamic, metabolic, and mechanical indexes of left ventricula r function were measured during conditions of control, ischemic dysfunction , IABP support, and HP support. A large animal (calf) model of left ventric ular dysfunction was created with multiple coronary ligations. Peak intrave ntricular pressure increased with HP support and decreased with IABP suppor t. Intramyocardial pressure (an indicator of intramyocardial stress), time rate of pressure change tan indicator of contractility), and left ventricul ar myocardial oxygen consumption decreased with IABP and HP support, Left v entricular work decreased with HP support and increased with IABP support. During HP support, indexes of wall stress, work, and contractility, all pri mary determinants of oxygen consumption, were reduced. During IABP support, indexes of wall stress and contractility were reduced and external work in creased. These changes were attributed primarily to changes in ventricular preload, and geometry for HP support, and to a reduction in afterload for I ABP support. These findings support the hypothesis that bath HP and IABP su pport reduce intramyocardial stress development and the corresponding oxyge n consumption, although via different mechanisms.