Circulation
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Comparative Study
Effect of normothermic blood cardioplegia on postoperative conduction abnormalities and supraventricular arrhythmias.
Conduction defects and supraventricular tachycardia (SVT) are common after myocardial revascularization using current methods of cold hyperkalemic blood or crystalloid cardioplegia. The current retrospective study was undertaken to assess the influence of normothermic blood cardioplegia on conduction defects and SVT. ⋯ Normothermic cardioplegia is associated with a marked decrease in new and permanent conduction disturbances and postoperative CK-MB release. This suggests that a significant factor in the pathogenesis of conduction blocks is cold-related injury. Supraventricular arrhythmias were not affected by the type of cardioplegia given.
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Randomized Controlled Trial Multicenter Study Clinical Trial
Pharmacokinetics and pharmacodynamics of intravenous diltiazem in patients with atrial fibrillation or atrial flutter.
Diltiazem, a calcium channel blocker, has been shown to be safe and effective in the treatment of patients in atrial fibrillation and/or atrial flutter. However, there have been no pharmacokinetic/pharmacodynamic studies of diltiazem in these patients. ⋯ First, the pharmacokinetics of diltiazem in patients with atrial fibrillation or atrial flutter is nonlinear with an apparent dose-dependent decrease in systemic clearance with increasing infusion rate. Second, using a sigmoidal Emax model, there is a strong relation between plasma diltiazem concentration and percent heart rate reduction. Third, the plasma concentrations of the principal metabolites desacetyldiltiazem and N-desmethyldiltiazem are low and are not expected to contribute significantly to the pharmacodynamics of intravenous diltiazem in these patients.
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Randomized Controlled Trial Comparative Study Clinical Trial
Aprotinin prevents cardiopulmonary bypass-induced platelet dysfunction. A scanning electron microscope study.
Administration of aprotinin during extracorporeal circulation reduces blood loss and improves platelet function. ⋯ By preserving platelet function, aprotinin improves postoperative hemostasis in all patients who receive high dose and in most who receive low dose.
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beta-Adrenergic receptor blockade has been reported to improve hemodynamics and beta-adrenergic receptor-adenylate cyclase function in idiopathic dilated cardiomyopathy. The purpose of this study was to determine the effects of beta-adrenergic receptor blockade on the beta-adrenergic receptor system and myocardial function in a model of compensated ischemic heart failure. ⋯ After large MI in rats, there is impaired papillary muscle function with decreased beta-adrenergic receptors and adenylate cyclase activity in the noninfarcted myocardium. Propranolol treatment improved basal isometric muscle function and beta-adrenergic receptor density in rats after myocardial infarction but did not improve adenylate cyclase activity or isoproterenol-stimulated muscle function. These data suggest that there is a primary defect in adenylate cyclase function that persists despite upregulation of receptors with propranolol treatment.
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Comparative Study
Precordial QT interval dispersion as a marker of torsade de pointes. Disparate effects of class Ia antiarrhythmic drugs and amiodarone.
Patients with a history of class Ia drug-induced torsade de pointes have been treated with chronic amiodarone without recurrence of torsade de pointes despite comparable prolongation of the QT interval. We hypothesized that in such patients, class Ia drugs cause nonhomogeneous prolongation of cardiac repolarization times, whereas amiodarone causes homogeneous prolongation of cardiac repolarization times. ⋯ An increase in regional QT interval dispersion during class Ia antiarrhythmic drug therapy is associated with torsade de pointes. Chronic amiodarone therapy in patients with a history of class Ia drug-induced torsade de pointes produces comparable maximum QT interval prolongation but does not increase QT interval dispersion. This characteristic may explain its apparent safe use in patients with a history of class Ia drug-induced torsade de pointes.