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Biomedical subjects

L Littmann

Publications and source records attributed to L Littmann.

At least 73 records · Page 4Linked to original sources
PubMed1986

Rate-dependent patterns of modulated ventricular parasystole.

The effects of ventricular pacing on the arrangement of ventricular parasystolic beats were studied in 14 patients. By analyzing the effects of various pacing rates and modalities, it was found that both rate and pattern of manifest parasystolic beats were intimately related to the rate and coupling interval of the paced rhythm. Our findings indicate that fixed coupling of ectopic beats is not incompatible with parasystole; modulated parasystole may manifest as fixed rate classic parasystole; a parasystolic pacemaker can be entrained by a wide range of driving rates both above and below the intrinsic rate of the parasystole; and with different driving rates, these rate-dependent patterns can be observed in the same patient. Our observations suggest that spontaneous or drug-induced changes in the heart rate can lead to major alterations in the frequency and patterns of ventricular parasystole.

Electrocardiography↗
PubMed1986

Failure of idioventricular suppression in man by overdrive pacing as well as lidocaine: the role of abnormal automaticity.

Five patients with third-degree atrioventricular block and an idioventricular escape rhythm who showed unusual responses to overdrive ventricular pacing and lidocaine are presented. In four cases, the idioventricular rhythm was not suppressed by overdrive; in one, the recovery time of the escape rhythm was shorter than the escape cycle length. Lidocaine did not affect the cycle lengths and recovery times of the idioventricular rhythms. These responses are characteristic of abnormal automaticity. The role of abnormal automaticity in human idioventricular escape rhythms has not been previously supported by these characteristic responses to overdrive pacing and lidocaine.

Aged↗
PubMed1986

Simple approach to an apparently chaotic arrhythmia.

Deciphering complex arrhythmias requires a strict, systematic approach. In a step-by-step analysis of an electrocardiogram recorded from a patient with severe metabolic disturbances, we present a few simple suggestions that may often be helpful in electrocardiographic interpretation.

Arrhythmias, Cardiac↗
PubMed1985

Electrophysiologic study of tachycardia-dependent paroxysmal His bundle block in man.

Electrophysiologic study was performed in a patient with tachycardia-dependent paroxysmal atrioventricular block. The site of block was within the His bundle. The effective refractory period of the His bundle was markedly prolonged and it was comparable to the critical atrial cycle length producing type II His bundle block. The most likely mechanism of paroxysmal atrioventricular block was repetitive concealed penetration of the blocking zone by nonconducted impulses that reached the proximal His bundle. Enhancing the blocking ratio at the atrioventricular nodal level resulted in improvement of overall atrioventricular conduction.

Atrioventricular Node↗
PubMed1985

The effects of overdrive pacing and lidocaine on atrioventricular junctional rhythm in man: the role of abnormal automaticity.

The effects of overdrive pacing and lidocaine were studied in 22 patients with atrioventricular (AV) junctional rhythms. Based on the responses to cardiac pacing and lidocaine, patients were divided into two groups. AV junctional rhythms in group I (17 patients) were suppressed by overdrive pacing, and their rates were decreased by lidocaine. Lidocaine also prolonged the junctional recovery time in these patients. AV junctional rhythms in group II (five patients) were not suppressed by overdrive pacing. In contrast, the rate increased after overdrive pacing. Lidocaine did not alter the basic cycle lengths or the recovery times of the AV junctional rhythms in this group of patients. The data suggest that AV junctional rhythms in group I were caused by normal automaticity, while those in group II were probably due to abnormal automaticity.

Adult↗
PubMed1985

Underdrive suppression of the sinus rhythm in man.

This report demonstrates unusual responses of the sinus rhythm to atrial pacing. The sinus rhythm failed to become manifest when the heart was driven at a rate slower than the inherent sinus rate. Sinus rhythm returned only after termination of underdrive pacing with the recovery time longer than twice the cycle length of the control sinus rhythm. The largest difference between underdrive and sinus cycle lengths measured 600 msec. To the best of our knowledge, underdrive suppression of the sinus rhythm has not been previously reported in man.

Aged↗
PubMed1984

Demonstration of reentry within the right bundle branch in man.

Reentry within the right bundle branch which, to our knowledge is a hitherto undescribed mechanism of His-Purkinje reentry in man, was elicited during programmed right ventricular stimulation. Electrophysiologic analysis excluded atrioventricular nodal reentry. His bundle reentry, reentry involving both bundle branches, and intraventricular micro-reentry.

Bundle of His↗
PubMed1982

Atrioventricular alternating Wenckebach periodicity: conduction patterns in multilevel block.

Atrioventricular (A-V) conduction patterns were analyzed in three patients with atrial pacing-induced alternating Wenckebach periodicity. These cases were unique because in each (1) separate levels of block responsible for the conduction disturbance were located above and below the His bundle recording site, and (2) there were several departures from the simple alternating Wenckebach pattern. Apparent supernormal conduction, temporary 1:1 conduction and a specific form of gap in A-V conduction resulted from the interplay of many factors including a simple mathematic relation of the blocking ratio at the two levels, the characteristics of the Wenckebach cycles, and the cycle length-dependent features of refractory periods at the different sites. The findings indicate that (1) delay in proximal impulse transmission is usually the critical factor in overcoming prolonged distal refractoriness and producing variable conduction atterns during the course of alternating Wenckebach periodicity; (2) many irregularities in alternating Wenckebach periodicity can be explained by known electrophysiologic mechanisms; and (3) simple mathematic equations alone are too rigid to reflect properly the dynamic process underlying this conduction disturbance.

Adult↗
PubMed1982

Concealed reentry: a mechanism of atrioventricular nodal alternating Wenckebach periodicity.

Alternating WEnckebach periodicity is generally believed to reflect bilevel block due to horizontal electrophysiologic dissociation in the conducting tissues. We describe a case of atrial pacing-induced atrioventricular nodal alternating Wenckebach periodicity with concealed reentry in a longitudinally dissociated AV conduction system. Three observations support this unique mechanism: Concealed reentry occurred during the course of alternating Wenckebach periodicity; it could be invoked to explain the peculiar conduction patterns in this patient; and alternative mechanisms did not explain the alternating Wenckebach periods. Our findings also indicate that long conduction times during 2:1 block can be due to concealed reentry rather than concealed antegrade conduction, and participation in the echo process of a retrograde pathway with electrophysiologic characteristics of an atrioventricular nodal bypass tract does not exclude manifest and concealed reentry at a subatrial level.

Adult↗
PubMed1982

Concealed re-entry in the human heart.

The mechanism and electrophysiologic manifestations of concealed re-entry were studied in human electrocardiograms and intracardiac recordings. Previously described patterns of concealed re-entry were documented in 49 patients. In seven cases concealed re-entry was involved in the genesis of Wenckebach periodicity and alternating Wenckebach periodicity in the AV node, and "reversed" Wenckebach periods in the His-Purkinje system. These manifestations of concealed re-entry were not described so far. In five cases re-entry was apparently concealed. Complete (but hidden) circus movement of the supraventricular impulses in these patients were detected by intracardiac recordings and by analysing the effects of echo beats on timing of the subsequent sinus beats. Concealed re-entry of the cardiac impulse is a well-documented electrophysiologic event which explains many common and peculiar manifestations of impulse formation and impulse conduction in the human heart.

Arrhythmias, Cardiac↗