Left Ventricular Unloading Before Reperfusion Promotes Functional Recovery After Acute Myocardial Infarction.

BACKGROUND: Heart failure after an acute myocardial infarction (AMI) is a major cause of morbidity and mortality worldwide. We recently reported that activation of a transvalvular axial-flow pump in the left ventricle and delaying myocardial reperfusion, known as primary unloading, limits infarct size after AMI. The mechanisms underlying the cardioprotective benefit of primary unloading and whether the acute decrease in infarct size results in a durable reduction in LV scar and improves cardiac function remain unknown. OBJECTIVES: This study tested the importance of LV unloading before reperfusion, explored cardioprotective mechanisms, and determined the late-term impact of primary unloading on myocardial function. METHODS: Adult male swine were subjected to primary reperfusion or primary unloading after 90 min of percutaneous left anterior descending artery occlusion. RESULTS: Compared with primary reperfusion, 30 min of LV unloading was necessary and sufficient before reperfusion to limit infarct size 28 days after AMI. Compared with primary reperfusion, primary unloading increased expression of genes associated with cellular respiration and mitochondrial integrity within the infarct zone. Primary unloading for 30 min further reduced activity levels of proteases known to degrade the cardioprotective cytokine, stromal-derived factor (SDF)-1α, thereby increasing SDF-1α signaling via reperfusion injury salvage kinases, which limits apoptosis within the infarct zone. Inhibiting SDF-1α activity attenuated the cardioprotective effect of primary unloading. Twenty-eight days after AMI, primary unloading reduced LV scar size, improved cardiac function, and limited expression of biomarkers associated with heart failure and maladaptive remodeling. CONCLUSIONS: The authors report for the first time that first mechanically reducing LV work before coronary reperfusion with a transvalvular pump is necessary and sufficient to reduce infarct size and to activate a cardioprotective program that includes enhanced SDF-1α activity. Primary unloading further improved LV scar size and cardiac function 28 days after AMI.

Duodenal Cannulation in Pigs (Sus scrofa) as a Drug Delivery Method.

Currently available animal models for delivery of drug capsules and pharmacokinetic testing are limited by either intersubject variability in gastric emptying time or the need to sedate animals when using targeted delivery methods of drug capsules. With the increasing development of large-molecule biologics, better in vivo models for testing the pharmacokinetics of capsule-delivered drugs are urgently needed. To this end, we made engineering modifications to an existing bovine surgical cannula device, successfully implanted this modified cannula into pigs, and delivered drug capsules directly to the proximal duodenum. In our porcine model, capsule insertion and serial blood samples were all acquired without the use of sedatives. Furthermore, we were able to maintain cannulated pigs for weekly pharmacokinetic testing for more than 18 mo, with minimal postoperative complications. This study demonstrates a novel and effective porcine model of sedation-free drug delivery and blood collection that eliminates inconsistencies associated with models that require either gastric emptying or animal sedation.

Hemodynamic effects of left atrial or left ventricular cannulation for acute circulatory support in a bovine model of left heart injury.

Our objective was to examine the hemodynamic effects of a trans-aortic axial flow catheter (Impella CP) in the left ventricle (LV) versus left atrial (LA) to femoral artery bypass using a centrifugal pump (TandemHeart: TH) in a bovine model of acute LV injury. In three male calves, we performed sequential activation of a CP then TH device in each animal. After 60 minutes of left anterior descending artery ligation, a CP was activated at maximal power. The CP was then removed and the TH activated at 5,500 then a maximum of 7,500 rotations per minute (RPM). The CP generated a maximum 3.1 ± 0.2 L/minute (LPM) of flow, whereas the TH at 5,500 and 7,500 RPM generated 3.1 ± 0.4 and 4.4 ± 0.3 LPM. At 3.1 LPM, the CP and TH reduced LV stroke work (LVSW) similarly. The TH reduced stroke volume, whereas the CP did not. The CP reduced end-systolic pressure, whereas the TH did not. At a maximum flow of 4.4 LPM, the TH provided a greater reduction in LVSW than maximal CP activation. This is the first report to compare the hemodynamic effects of trans-aortic LV unloading versus LA-to-femoral artery (FA) bypass.