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Ligation of the posterior interventricular branch of the right coronary artery in rats induced bradyarrhythmia similar by its pathophysiological mechanisms to bradyarrhythmias developed in humans during acute ischemia of the posterior cardiac wall. The type and severity of arrhythmia and conduction disturbances, their latency and duration, and correlation with the volume of damaged myocardial tissue were determined. The efficacy and safety of the use of methylxanthines during acute myocardial ischemia was proved. [ABSTRACT FROM AUTHOR]

Epicardial potentials of the sinus node, the right atrium, and the right ventricle were recorded in dogs during cold potassium-induced cardioplegia. We found that the sinus node fibers were more resistant to the cardioplegia than were the other myocardial fibers. When the cardioplegia rendered the atrial muscle inexcitable, the high frequency atrial potential was delayed and then abolished in the sinus node electrogram, and a smooth tracing similar to the action potential of the sinus node cell appeared. These findings should be pertinent for the cardiac surgeon attempting to avoid surgically-induced sinoatrial arrhythmias. [ABSTRACT FROM AUTHOR]

Complete heart block in children admitted to the pediatric intensive care unit with respiratory syncytial viral (RSV) infections has been described. This report describes a prolonged sinoatrial block exceeding 4 s in an infant with RSV, which, to the authors' knowledge, is the longest such event described in the published literature. This block was followed by shorter episodes within the next 24 h. An extensive workup showed no other known cause of bradycardia or sinoatrial block. The infant was discharged home with 48 h Holter monitoring, which was normal. At this writing, the infant has remained asymptomatic since discharge. Respiratory syncytial viral infections may cause prolonged sinoatrial block in an otherwise healthy child. [ABSTRACT FROM AUTHOR]