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Biomedical subjects

L Zaman

Publications and source records attributed to L Zaman.

52 records · Page 3Linked to original sources
PubMed1983

Multiple electrophysiologic manifestations and clinical implications of vagally mediated AV block.

Clinical, surface ECG, and intracardiac findings were analyzed in 20 patients with spontaneous conduction disturbances in whom vagally mediated AV block could be induced by carotid sinus pressure during electrophysiologic evaluation. The latter demonstrated that the surface ECG pattern attributed to bradycardia-dependent (phase 4), and paroxysmal block within the His bundle and bundle branches could reflect vagally mediated, bradycardia-associated (rather than bradycardia-dependent), and paroxysmal AV nodal (AH) block. The decision regarding the use of pacemakers was not based on QRS duration or on patterns (or site) of block but on the underlying clinical settings and the correlation of symptoms with maximal ventricular (R-R) pauses. However, more studies are required to extend our findings, especially to other subgroups of patients (or normal individuals) in whom vagally mediated block occurs.

Aged↗
PubMed1983

Ectopic left atrial rhythm that produces QRS changes in absence of Wolff-Parkinson-White syndrome.

In an 18-year-old patient without manifest or concealed Wolff-Parkinson-White syndrome, spontaneous and paced left atrial impulses penetrated a left-sided AV nodal input and thereafter activated the ventricles in a normal fashion exclusively through the His-Purkinje system. On the other hand, sinus and paced right atrial impulses entered a right-sided atrioventricular nodal input that was completely dissociated from the left-sided input to subsequently activate the ventricles partly through Mahaim fibers and partly through the His-Purkinje system. The Mahaim fibers, which acted as "bystanders" during episodes of atrioventricular nodal reciprocating tachycardia, seemed to have extended from a "distal," common (right-sided) intranodal pathway (or "proximal" His bundle) to the right ventricle or, although this is less likely, to the right bundle branch. More studies are necessary to determine whether the association on the surface electrocardiogram of an ectopic slow left atrial rhythm with changes in QRS morphology (but not in QRS duration) always reflects the existence of Mahaim fibers.

Adolescent↗
PubMed1983

The arrhythmias of dual-chamber cardiac pacemakers and their management.

The field of cardiac pacing has developed exponentially in the past several years. The widespread use of atrioventricular synchronous pacemakers has resulted in the recognition of several types of pacemaker-associated arrhythmias. Certain of these arrhythmias follow asynchronous stimulation of either cardiac chamber; others are the result of the artificial bypass tract created with dual-chamber sensing and pacing. All the arrhythmias, however, are associated with normal pacemaker function.

Arrhythmias, Cardiac↗
PubMed1982

Electrophysiologic effects of diltiazem hydrochloride on supraventricular tachycardia.

The effects of intravenous diltiazem hydrochloride (0.25 mg/kg body weight) were studied in eight patients with nine episodes of supraventricular tachycardia. Five episodes of tachycardia were due to atrioventricular (A-V) nodal reentry (group A), two were due to retrograde utilization of a concealed A-V accessory pathway (group B) and two were episodes of atrial fibrillation (group C). Intravenous administration of diltiazem slowed the ventricular rate in eight of nine episodes of tachycardias. Supraventricular tachycardia was terminated within 2 minutes after intravenous diltiazem in four of five patients in group A, and one of two in group B. Cycle length alternation was observed before termination of the arrhythmia in two patients from group A. In group C the ventricular response slowed but also became regular during atrial fibrillation. Although diltiazem depressed both anterograde and retrograde conduction as assessed by programmed stimulation, tachycardia termination or slowing or alternation of cycle length all occurred because of the effects of diltiazem predominantly on anterograde A-V nodal properties during supraventricular tachycardia. Although no statistical conclusions can be made from this limited study, it appears that diltiazem has significant depressant electrophysiologic effects on both anterograde and retrograde A-V nodal function as assessed by programmed stimulation during sinus rhythm. Further electrophysiologic studies are needed before determining the clinical efficacy of this agent for treatment or prophylaxis of recurrent supraventricular tachycardias.

Adult↗
PubMed1982

Aberrant origin of the left coronary artery from the proximal right coronary artery: diagnostic features and pre- and postoperative course.

In this report, we present the pre and late postoperative course of a patient with severe angina secondary to aberrant origin or the left coronary artery from the proximal righ coronary artery (Fig. 1). We illustrate the noninvasive diagnosis and evaluation of this patient by two-dimensional ultrasound and stress thallium imaging, and the pre and late postoperative angiographic and thallium perfusion findings.

Angina Pectoris↗
PubMed1982

Evolving concepts of management of stable and potentially lethal arrhythmias.

Recent studies indicate that the eradication of premature ventricular complexes (PVCs) by antiarrhythmic agents is an inadequate end point for estimating long-term protection against potentially lethal arrhythmias. In a study of survivors of prehospital ventricular fibrillation (VF), who have a 30% risk for recurrent VF during the first year of follow-up, we observed an apparent protection against recurrent VF by antiarrhythmic agents even if chronic PVCs were not suppressed by stable therapeutic plasma levels. To expand the data base pertinent to the relationships between PVCs and advanced arrhythmias, we studied six patients with chronic recurrent ventricular tachycardia (VT) and frequent PVCs between episodes of VT. Plasma levels of procainamide (PA) required to protect against recurrent VT averaged 9.4 +/- 3.4 microgram ml, compared with mean levels of 14.9 +/- 3.8 microgram/ml for 85% suppression of PVCs (p less than 0.01). PVC frequency decreased by a mean of only 36% (range -11% to -63%) at plasma levels of PA sufficient to prevent spontaneous VT. Concentration-response relationships between (PA) and PVC suppression were also compared in patients with PVCs during acute myocardial infarction and in patients with PVCs in stable chronic ischemic heart disease. In the former group of patients the mean plasma level of PA required to suppress 85% of the PVCs was 5.0 +/- 0.5 microgram/ml, and in the latter group was 9.3 +/- 0.7 microgram/ml (p less than 0.001). We conclude that the relationship between plasma levels of PA and PVC suppression is different in the two groups of patients, and furthermore, that a high degree of PVC suppression may not be a necessary end point for protecting patients against symptomatic recurrent VT or VF.

Arrhythmias, Cardiac↗
PubMed1982

Quintuple pathways participating in three distinct types of atrioventricular reciprocating tachycardia in a patient with Wolff-Parkinson-White syndrome.

Electrophysiologic studies were performed in a patient with recurrent supraventricular tachyarrhythmias. Sinus and paced atrial beats had QRS complexes characteristic of atrioventricular (A-V) conduction through a manifest left lateral accessory pathway (Wolff-Parkinson-White syndrome, type A). Three distinct types of A-V reciprocating tachycardia and three different modes of retrograde atrial activation were demonstrated. Type 1 tachycardia involved the slow A-V nodal pathway and a second (left lateral or left paraseptal) accessory A-V pathway capable of retrograde conduction only. Type 2 tachycardia was of the slow-fast A-V nodal pathway type. Type 3 tachycardia involved in heretofore undescribed circuit in that retrograde conduction occurred through an accessory A-V pathway with long retrograde conduction times and anterograde conduction through both the manifest left lateral accessory A-V pathway and fast A-V nodal pathway. Premature ventricular beats delivered late in the cycle of this tachycardia advanced (but did not change) the retrograde atrial activity without affecting the timing of the corresponding anterograde H deflection. In summary, this patient had five (three accessory and two intranodal) pathways participating in three different types of A-V reciprocating tachycardia; the recurrence of these were prevented with oral amiodarone therapy.

Aged↗
PubMed1982

"Invisible" pseudo-pseudofusion beats.

Three simultaneous leads (I, II and VI) were recorded in a patient with a normally functioning bipolar AV sequential (DVI) pacemaker. Superimposition of the ineffectual atrial spikes upon the early part of the QRS complexes resulted in pseudo-pseudofusion beats, clearly identified in lead II. However, the small spikes were hardly seen in lead I and not seen at all in lead VI. Therefore, the pseudo-pseudofusion beats were "almost invisible" and "invisible," respectively, in these leads. Delivery of atrial spikes within the beginning of the QRS complexes was possible because sensing of the ventricular electrogram occurred after the onset of ventricular depolarization in the surface leads.

Electrocardiography↗
PubMed1982

Transverse dissociation of the human His bundle.

"Completed" and "abortive" alternating Wenckebach periods occurred in a symptomatic female with calcification of the mitral annulus. These arrhythmias were attributed to transverse dissociation of the His bundle into two horizontal levels "connected in series," with 2:1 block in the "distal" level and Wenckebach periods in the "proximal" level. Intra-Hisian alternating Wenckebach periods resembled those resulting from transverse dissociation of other infra-AV nodal structures in that they are rare, usually symptomatic and require pacemaker implantation. This contrasts with the variety of rhythms resulting from transverse dissociation of the AV node which occur frequently, are not always malignant, and generally are not treated with implanted pacemakers.

Bundle of His↗
PubMed1981

Atropine-induced multilevel block in acute inferior myocardial infarction. A possible indication for prophylactic pacing.

The degree of A-V block increased after intravenous administration of atropine in 10 nondigitalized patients with acute inferior myocardial infarction who had narrow QRS complexes during periods of 1:1 A-V conduction. Short episodes of 3:1, 4:1 and 5:1 A-V block were seen to emerge: (a) in 6 patients, directly from Wenckebach periods; (b) in 3 patients, from alternating Wenckebach periods; and (c) in 1 patient, from a 3:2 Wenckebach period which led to a short-lived alternating Wenckebach period. Apparently, the predominance of the chronotropic effects on the sinus node over the dromotropic effects on the A-V node led to a tachycardia-dependent (more ischemic than vagal) process, exposing or producing multi- (two, three or four) level block involving the A-V node (and perhaps the His bundle). Subsequently, therapeutic pacing was instituted in 9/10 patients because they developed spontaneous symptomatic advanced A-V block. Therefore, it is possible that the early effects of atropine identified a narrowly-defined subset of patients in whom prophylactic pacing may be indicated. However, more studies are necessary to corroborate these assumptions.

Atropine↗
PubMed1981

The mechanism of flutter electrical alternans.

We have had the opportunity to observe the occurrence of flutter electrical alternans in which two distinct populations of flutter waves are present and which alternate in 1:1 and 2:1 patterns. The flutter alternans whether 2: or 3:1, was concordant with the pattern of preceding ventricular conduction (ventriculophasic variation). This concordance occurred reproducibly and remained consistent. Our example of flutter alternans probably represents mechanical artefact caused by catheter movement during ventricular mechanical systole. We reproduced this pattern consistently at a slower rate during coronary sinus pacing. These findings appear to suggest an explanation for certain types of so-called atrial flutter electrical alternans.

Atrial Flutter↗