44 research outputs found
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The Chicago School of Arrhythmology: An Analysis of a Revisionist View
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Atrioventricular block after reciprocating atrioventricular junctional tachycardia
Short runs of symptomatic atrioventricular (A-V) block occurred after spontaneous cessation of reciprocating A-V Junctional tachycardia in a patient with right bundle branch block, normal H-V interval and sinus nodal dysfunction. These episodes were characterized by long (more than 1 sec) P-P intervals during which the A deflections were not followed by His bundle electrograms. Three possible explanations are: (1) a posttachycardia-induced period of abnormally prolonged A-V nodal refractoriness; (2) pseudo-A-V block produced by concealed A-V Junctional tachycardia, or (3) bradycardia-dependent (phase 4) A-V block at the “upper” His bundle, above the site from which the H deflection was recorded
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A Different Approach to the Analysis of Pure Ventricular Parasystole
Until recently, it had not been recognized that predictions regarding the number of sinus beats interposed between two consecutive parasystolic beats could be made. In a case of perfect, pure parasystole resulting from unintentional fixed rate ventricular pacing, the following was observed: there were consistently three different values (0,2,3) for the number of interposed sinus beats; only one of these values was odd, and the sum of the two smaller values was one less than the larger value. Our findings, which are in keeping with those obtained in an mathematical model, may be of additional help in the diagnosis of this elusive arrhythmia
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Electrophysiologic Studies in a Patient with Atrial Flutter and 1:1 Atrioventricular Conduction
Intracardiac electrophysiologic studies were performed in a patient having paroxysms of atrial flutter with 1:1 atrioventricular (A-V) conduction. Although duration of conduction intervals was normal during sinus rhythm, the atrio-His (A-H) interval did not show the expected increase when the atria were stimulated at progressively higher rates. The results of pacing with the extrastimulus technique also indicated that the refractory periods of the A-H tissues were shorter than normal. Yet, intravenously administered ouabain produced a significant increase in these refractory periods. The findings in this case are compatible with a partial A-V nodal bypass with a shorter refractory period than the A-V node or with an A-V node with unusual capacity for rapid conduction. The response to ouabain therapy was that of A-V nodal tissues
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Dynamics of the QT intervals encompassing secondary repolarization abnormalities during sudden but transient lengthening of the RR intervals
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Patterns of acute inferior wall myocardial infarction caused by hyperkalemia
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Second degree His-Purkinje block during his bundle pacing
This report presents, for the first time, clear evidence supporting the occurrence of Wenckebach and 2:1 H-V block during His bundle pacing. The simultaneous recording of various intracardiac electrograms, as well as the comparison of the effects produced by selective His bundle pacing and high right atrial pacing at the same rates, permitted the identification of conduction disturbances located distal to the paced His bundle site. This could be done although one criterion usually required to diagnose selective His bundle pacing (namely, stimulus-V intervals of
constant duration) was not presen