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Effect of Intracoronary Metformin on Myocardial Infarct Size in Swine.

ABSTRACT: RATIONALE:Metformin has been demonstrated to decrease infarct size (IS) and prevent postinfarction left ventricular (LV) remodeling in rodents when given intravenously at the time of reperfusion. It remains unclear whether similar cardioprotection can be achieved in a large animal model. OBJECTIVE:The objective of this study was to determine whether intravascular infusion of metformin at the time of reperfusion reduces myocardial IS in a porcine model of acute myocardial infarction. METHODS AND RESULTS:In a blinded and randomized preclinical study, closed-chest swine (n=20) were subjected to a 60-minute left anterior descending coronary artery occlusion to produce myocardial infarction. Contrast-enhanced computed tomography was performed during left anterior descending coronary artery occlusion to assess the ischemic area-at-risk. Animals were randomized to receive either metformin or vehicle as an initial intravenous bolus (5 mg/kg) 8 minutes before reperfusion, followed by a 15-minute left coronary artery infusion (1 mg/kg per minute) commencing with the onset of reperfusion. Echocardiography and computed tomographic imaging of LV function were performed 1 week later, at which time the heart was removed for postmortem pathological analysis of area-at-risk and IS (triphenyltetrazolium chloride). Baseline variables including hemodynamics and LV function were similar between groups. Peak circulating metformin concentrations of 374±35 µmol/L were achieved 15 minutes after reperfusion. There was no difference between the area-at-risk as a percent of LV mass by computed tomography (vehicle: 20.7%±1.1% versus metformin: 19.7%±1.3%; P=0.59) or postmortem pathology (22.4%±1.2% versus 20.2%±1.2%; P=0.21). IS relative to area-at-risk averaged 44.5%±5.0% in vehicle-treated versus 38.2%±6.8% in metformin-treated animals ( P=0.46). There was no difference in global function 7 days after myocardial infarction as assessed by echocardiography or computed tomographic ejection fraction (56.2%±2.6% versus 56.3%±2.4%; P=0.98). CONCLUSIONS:In contrast to rodent hearts, postconditioning with high-dose metformin administered immediately before reperfusion does not reduce IS or improve LV function 7 days after myocardial infarction in swine. These results reinforce the importance of rigorously testing therapies in large animal models to facilitate clinical translation of novel cardioprotective therapies.

SUBMITTER: Techiryan G

PROVIDER: S-EPMC6207210 | biostudies-literature | 2018 Sep

REPOSITORIES: biostudies-literature

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Effect of Intracoronary Metformin on Myocardial Infarct Size in Swine.

Techiryan George G Weil Brian R BR Palka Beth A BA Canty John M JM

Circulation research 20180901 8

<h4>Rationale</h4>Metformin has been demonstrated to decrease infarct size (IS) and prevent postinfarction left ventricular (LV) remodeling in rodents when given intravenously at the time of reperfusion. It remains unclear whether similar cardioprotection can be achieved in a large animal model.<h4>Objective</h4>The objective of this study was to determine whether intravascular infusion of metformin at the time of reperfusion reduces myocardial IS in a porcine model of acute myocardial infarctio ...[more]

PMID: 30355033

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Project description:BackgroundPerfluoropropane droplets formulated from commercial microbubbles exhibit different acoustic characteristics than their parent microbubbles, most likely from enhanced endothelial permeability. This enhanced permeability may permit delayed echo-enhancement imaging (DEEI) similar to delayed enhancement magnetic resonance imaging (DE-MRI). We hypothesized this would allow detection and quantification of myocardial scar.MethodsIn 15 pigs undergoing 90 minutes of left anterior descending ischemia by either balloon (n = 13) or thrombotic occlusion (n = 2), DE-MRI was performed at 2-24 days postocclusion. Delayed echo-enhancement imaging was performed at 2-4 minutes following an intravenous injection of 1 mL of 50% Definity (Lantheus Medical) compressed into 180 nm droplets; DEEI was attempted in all pigs with single-pulse harmonic imaging at 1.7 transmit/3.4 MHz receive. Myocardial defects observed with DEEI were quantified (percentage of infarct area) and compared with DE-MRI as well as postmortem staining. In six pigs, multipulse low-mechanical index (MI) fundamental nonlinear imaging (FNLI) with intermittent high-MI impulses was performed to determine whether droplet activation within the infarct zone was achievable with a longer pulse duration.ResultsThe range of infarct size area by DE-MRI ranged from 0% to 46% of total left ventricular area. Single-pulse harmonic imaging detected a contrast defect that correlated closely with infarct area by DE-MRI (r = 0.81, P = .0001). The FNLI high-MI impulses resulted in droplet activation in both the infarct and normal zones. Harmonic subtraction of the FNLI images resulted in infarct zone enhancement that also correlated closely with infarct size (r = 0.83; P = .04). Droplets were observed on postmortem transmission electron microscopy within myocytes of the infarct and remote normal zone.ConclusionIntravenously Definity nanodroplets can be utilized to detect and quantify infarct zone at the bedside using DEEI techniques.

Project description:BackgroundThrombus embolization and microvascular obstruction during percutaneous coronary intervention (PCI) in ST-segment elevation myocardial infarction (STEMI) is commonly detected, which causes inadequate myocardial perfusion and elevated infarct size. An approach with low-dose intracoronary fibrinolytic treatment for reducing distal embolization and improving myocardial reperfusion in high-risk STEMI cases remains controversial.MethodsThe RECOVER II study represents a multicenter, randomized, double-blind, parallel-group trial assessing low-dose adjunctive intracoronary reteplase during primary PCI in individuals with large anterior myocardial infarction and thrombus determined by angiography. The trial will enroll 306 cases who present within 12 h following STEMI for proximal or mid left anterior descending artery occlusion undergoing primary PCI. Cases will be randomized to receive a bolus intracoronary reteplase at 9 mg or 18 mg vs. placebo. The drug will be delivered over 2 minutes proximal to culprit lesions with an intracoronary catheter early after wire-crossing and before thrombus aspiration or balloon dilation.ResultsThe primary outcome will be infarct size assessed by late gadolinium-enhanced magnetic resonance imaging (MRI) (% of left ventricular mass) on day 7 after enrollment. Secondary outcomes will include the amount of microvascular obstruction and myocardial salvage index examined via MRI on day 7, angiographic measures of reperfusion [Thrombolysis in Myocardial Infarction (TIMI) coronary flow grade, TIMI frames count and myocardial blush grade], incidence of complete ST-segment resolution at 2 hours after reperfusion, area under the curve for troponin T, and rates of major adverse cardiovascular events at 30 days.ConclusionsRECOVER II will determine whether the addition of low-dose intracoronary reteplase early after wire-crossing as an adjunct to reperfusion treatment reduces infarct size in individuals with large anterior myocardial infarction.Trial registrationClinicalTrials.gov Identifier: NCT04571580.

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Effect of Intracoronary Metformin on Myocardial Infarct Size in Swine.

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Effect of Intracoronary Metformin on Myocardial Infarct Size in Swine.

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