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      Attenuation of ST-segment elevation after ischemic conditioning maneuvers reflects cardioprotection online

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          Impact of the Timing of Metoprolol Administration During STEMI on Infarct Size and Ventricular Function.

          Pre-reperfusion administration of intravenous (IV) metoprolol reduces infarct size in ST-segment elevation myocardial infarction (STEMI).
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            Ischemic preconditioning during coronary angioplasty is prevented by glibenclamide, a selective ATP-sensitive K+ channel blocker.

            Brief episodes of ischemia render the heart more resistant to subsequent ischemia; this phenomenon has been called ischemic preconditioning. In some animal species, myocardial preconditioning appears to be due to activation of ATP-sensitive K+ (KATP) channels. The role played by KATP channels in preconditioning in humans remains unknown. The aim of this study was to establish whether glibenclamide, a selective KATP channel blocker, abolishes the ischemic preconditioning observed in humans during coronary angioplasty following repeated balloon inflations. Twenty consecutive patients undergoing one-vessel coronary angioplasty were randomized to receive 10 mg oral glibenclamide or placebo. Sixty minutes after glibenclamide or placebo administration, patients were given an infusion of 10% dextrose (8 mL/min) to correct glucose plasma levels or, respectively, an infusion of saline at the same infusion rate. Thirty minutes after the beginning of the infusion, both patient groups underwent coronary angioplasty. The mean values (+/- 1 SD) of ST-segment shifts on the surface 12-lead ECG and the intracoronary ECG were measured at the end of the first and second balloon inflations, both 2 minutes long. In glibenclamide-treated patients, the mean ST-segment shift during the second balloon inflation was similar to that observed during the first inflation (23 +/- 13 versus 20 +/- 8 mm, P = NS), and the severity of cardiac pain was greater (55 +/- 21 versus 43 +/- 23 mm on a scale of 0 to 100, P < .05). Conversely, in placebo-treated patients the mean ST-segment shift during the second inflation was less than that during the first inflation (9 +/- 5 versus 23 +/- 13 mm, P < .001), as was the severity of cardiac pain (15 +/- 15 versus 42 +/- 19 mm, P < .01). Blood glucose levels were significantly reduced 60 minutes after glibenclamide compared with those at baseline (53 +/- 9 versus 102 +/- 10 mg/100 mL, P < .001) in the glibenclamide group; however, before coronary angioplasty, blood glucose levels increased to 95 +/- 19 mg/100 mL, a value similar to that found in placebo group (96 +/- 11 mg/100 mL, P = NS). In humans, ischemic preconditioning during brief repeated coronary occlusions is completely abolished by pretreatment with glibenclamide, thus suggesting that it is mainly mediated by KATP channels.
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              Measurement of regional myocardial blood flow with multiple colored microspheres.

              The use of radioactive microspheres (RM) for the measurement of regional myocardial blood flow (RMBF) is limited and inaccessible to many investigators due to radiation safety concerns and radioactive waste disposal problems. Therefore, a new method for the measurement of RMBF using colored microspheres (CM) was developed. Polystyrene spheres (diameter, 15 +/- 0.1 [SD] micron; density, 1.09 g/ml) were dyed with one of five colors. With the injection of CM into the left atrium or into a coronary perfusion line, RMBF and its distribution can be determined. CM are extracted from the myocardium and blood by digestion with potassium hydroxide and subsequent microfiltration. The dyes are then recovered from the CM within a defined volume of a solvent, and their concentrations are determined by spectrophotometry. The separation of composite absorbance spectra by spectrophotometry with the CM technique was as good as the separation of energy spectra by a gamma-counter using the RM technique. Leaching of dye from the CM was less than 0.1% during a 2-month period in vitro. Significant leaching of dye from the microspheres also did not occur during 8 hours in the blood and myocardium of four anesthetized dogs in vivo. For further validation of this method, pairs of CM and RM (15.5 +/- 0.1 [SD] microns) were simultaneously injected under five different RMBF conditions (range, 0-10 ml/[min.g]) into the left anterior descending coronary artery of four anesthetized pigs, with coronary inflow as a flow reference, or into the left atrium of four anesthetized dogs using aortic blood withdrawal as a reference. The relation between RMBF determined by CM and RM was CM = 0.01 + 1.00.RM (r = 0.98, n = 1,080 data points) in the pigs, and CM = -0.19 + 0.92.RM (r = 0.97, n = 1,813 data points) in the dogs. Measurement of RMBF with CM yields values very similar to those of RM. Their use is less expensive and avoids all the disadvantages related to radioactivity, thus offering an alternative method for as many as five RMBF measurements in a single experiment.
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                Author and article information

                Journal
                Basic Research in Cardiology
                Basic Res Cardiol
                Springer Science and Business Media LLC
                0300-8428
                1435-1803
                May 2019
                April 1 2019
                May 2019
                : 114
                : 3
                Article
                10.1007/s00395-019-0732-3
                © 2019

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