Development of a porcine beating-heart model of self-myocardial retroperfusion: evaluation of hemodynamic and cardiac responses to ischemia and clinical applications.

BACKGROUND: Retrograde perfusion into the coronary sinus is used to deliver cardioplegia. We developed an in-vivo porcine beating-heart model of self-myocardial retroperfusion (SMR) using the venous route to supply myocardial oxygenation and sought to assess hemodynamic and cardiac responses triggered by SMR before and after a prolonged occlusion of the LAD.

METHODS: A bypass-line between the ascending aorta and the coronary sinus was made to perform a selective retrograde perfusion of the great cardiac vein with oxygenated blood (SMR). A Control group (N.=6) was assigned to collect baseline data, and an SMR group (N.=6) was dedicated to undergo SMR with occlusion of LAD for 240 minutes. Cardiac output (CO), maximal pressure in the LV (Pmax in-LV), stroke volume (SV), left ventricular ejection fraction (LVEF), diastolic durations, heart rate, and arterial systemic pressure were evaluated with conductance catheters for the following periods: basal (before SMR), SMR with patent LAD, and SMR with occluded LAD. In order to assess peripheral perfusion, patterns of sublingual microcirculation were analyzed. At the end of the procedures, the hearts were harvested for histology.

RESULTS: Echographic LVEF evaluation was affected by sternotomy, but conductance catheter evaluation was not. Following pericardiotomy, CO decreased by 7.51% (P<0.05). SMR with patent LAD showed inotropic properties with improvements in CO, SV, Pmax in-LV and LVEF (P<0.0001). Following LAD occlusion, SMR supplied myocardial oxygenation with hemodynamic compensation and preserved the peripheral perfusion. Histology confirmed no signs of infarct.

CONCLUSIONS: SMR showed capacities to produce inotropic effects and protect against ischemia, opening interesting perspectives.