Exercise tolerance testing in symptomatic and asymptomatic complete intra-His block.
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Aged↗
Biomedical subjects
L Zaman
Publications and source records attributed to L Zaman.
Recent advances in the diagnosis of fascicular blocks.
The electrocardiographic criteria for the diagnosis of left fascicular blocks have been a subject of debate and speculation. Nevertheless, careful analysis of certain electropathologic studies, extrapolations from animal experiments, and studies resulting from the inadvertent section of the various fascicles and of tracings obtained at the moment that the conduction disturbances appeared or disappeared have led to the acceptance of characteristic patterns. Although the specificity and sensitivity of electrocardiographic criteria of left anterior and left posterior fascicular block still require independent confirmation, there are already some methods that appear promising in this regard.
Bundle of His↗
Unstable intraventricular conduction disorders.
Unstable bundle branch blocks may be tachycardia dependent, bradycardia dependent, or rate independent. When appearing at the "critical" rates or "critical" cycle lengths they may seem to be rate independent. Conversely, "true" rate-independent blocks may be reversible or irreversible. Determining if a rate-unrelated block may disappear can be difficult because irreversile bundle branch block seems to develop through a slow process in time during which rate-dependent, rate-independent, and even normal conduction alternate in successive electrocardiograms.
Bradycardia↗
Linking phenomenon during atrial stimulation with accessory pathways.
Linking is an electrophysiologic phenomenon in which each successive impulse entering a macroreentry circuit propagates preferentially along 1 limb because of the functional impedance to conduction in the contralateral limb produced by the previous impulse. Electrophysiologic studies were performed in 12 patients with a bidirectionally conducting accessory pathway. Linking was analyzed while 1:1 atrioventricular conduction took place through the normal pathway. When atrial pacing (at the same cycle length) could be initiated during sinus rhythm in patients with rapidly conducting accessory pathways, linking was dynamically maintained by repetitive local refractoriness (interference). When it could be initiated during the usual type of orthodromic circus movement tachycardia, linking was sustained by actual impulse collision, the underlying mechanism having also been called entrainment. When it could be initiated during sinus rhythm in a patient with a slowly conducting accessory pathway, linking was maintained by impulse collision, but the underlying mechanism could not be called entrainment because stimulation had not been started during tachycardia. This study showed that 2 terms--linking and entrainment--may be applied to the same mechanism and, conversely, that the same name could not be used in reference to the same mechanism when pacing was initiated under different circumstances. However, using the proposed conceptual formulation for linking, it is apparent that seemingly diverse mechanisms associated with macroreentry circuits involving accessory pathways are, in fact, variations on a common electrophysiologic theme.
Adolescent↗
Cardiac arrest in an adolescent with atrial fibrillation and hypertrophic cardiomyopathy.
A 15 year old youth, who presented with out-of-hospital cardiac arrest due to documented ventricular fibrillation, was found to have nonobstructive hypertrophic cardiomyopathy. Electrophysiologic study demonstrated inducible sustained atrial fibrillation with a rapid ventricular response. This rhythm, associated with hypotension and evidence of myocardial ischemia, spontaneously degenerated into ventricular fibrillation. No ventricular arrhythmias were inducible by programmed ventricular stimulation. Therapy with metoprolol and verapamil slowed the ventricular rate during atrial fibrillation and maintained hemodynamic stability, both during follow-up electrophysiologic study and during a subsequent spontaneous episode.
Adolescent↗
Attempted entrainment of circus movement tachycardias by ventricular stimulation.
Entrainment was attempted while pacing the right ventricle in 12 patients with circus movement tachycardias. At the onset of stimulation eight patients had short episodes of intraventricular and atrioventricular dissociation during which the paced impulses activated the various ventricular recording sites (right and left), but did not reach the atria. The latter occurred because the ventricular electrograms were recorded from parts of the ventricles which were not essential components of the reentry circuit. Relatively long (greater than 5 s) runs of entrainment were not possible in any case because of the relatively prompt termination of the tachycardias. Whereas in three patients this was due to the abrupt appearance of retrograde block in the accessory pathway, in nine patients it happened when the sequential, anterograde and retrograde, penetration of the AV node resulted in AV nodal block of the subsequent, reentering atrial impulse. The findings in this study showed that, with the methodology used, entrainment of circus movement tachycardias by ventricular stimulation had to be defined conceptually, by the fulfillment of requirements which did not include its occurrence for at least 5 seconds. Furthermore, the results also suggested that entrainment and tachycardia termination were best demonstrated by a technique which allowed the emission of the first stimulus in a constant (late) moment of the cycle, with deliverance of one additional stimulus at the same cycle length in successive pacing runs.
Adolescent↗
Surgical management of post-myocardial infarction ventricular tachyarrhythmia by myocardial debulking, septal isolation, and myocardial revascularization.
Sustained ventricular tachycardia or ventricular fibrillation, associated with severely depressed left ventricular function after myocardial infarction, carries a poor prognosis. We have used an extensive surgical procedure in 18 patients (15 men and three women) with a mean age of 63 years who had more than three episodes of recurrent, hemodynamically significant ventricular tachycardia or fibrillation and congestive heart failure. The operation consisted of complete myocardial revascularization and myocardial debulking by extensive infarctectomy with unguided endocardial resection and septal isolation with support of the necrotic wall with a Teflon patch. Implantable defibrillator patches were placed in eight patients. Blood cardioplegia and intra-aortic balloon assist (12 patients) were used for perioperative myocardial preservation. Postoperative studies demonstrated a significant increase in ejection fraction (n = 16) and a decline in pulmonary wedge pressure. Hospital mortality was 16% (three patients). Two deaths were due to congestive heart failure and one to arrhythmia. During postoperative electrophysiologic studies, ventricular tachycardia was not inducible in six of eight patients (75%). During a mean follow-up of 24 months, 11 of 15 patients who survived operation are alive and are in New York Heart Association Class I or II. Three of four late deaths were due to congestive heart failure and drug toxicity and one was arrhythmia related. This procedure is effective for preventing recurrent ventricular tachycardia or fibrillation in a majority of patients who cannot have intraoperative mapping.
Aged↗
Concealment of manifest, and exposure of concealed, ventricular parasystole produced by isoproterenol.
Few studies have dealt with the effects of isoproterenol on ventricular parasystole. Intravenous isoproterenol (2 to 4 micrograms/min) was administered to 11 nonmedicated patients with ventricular parasystole. At the onset of the drip infusion, 8 patients had continuous parasystole, 2 had intermittent parasystole, and 1 patient (in whom intermittent parasystole was documented 2 to 5 days earlier) showed no manifest parasystolic activity. In all patients, whose control parasystolic cycle length varied between 960 and 2,530 ms, isoproterenol caused a decrease of the parasystolic cycle lengths ranging from 12 to 36%. Therefore, isoproterenol produced a consistent increase of the parasystolic rate. In 4 patients, parasystolic activity ceased to be manifest when the concomitantly enhanced (by isoproterenol) sinus cycle lengths became shorter than 430 ms. This phenomenon reflected a tachycardia-dependent parasystolic concealment, presumably as a result of interference in the parasystolic-ventricular junction. In every case, the arrhythmia reappeared at its initial rate upon stopping the drip infusion. In no patient did parasystolic ventricular tachycardia develop. In the patient without manifest parasystolic beats, isoproterenol unmasked the intermittent parasystole that previously had been intrinsically manifest. The latter effect reflected a true exposure, or unmasking of a latent, rate-independent concealed, parasystolic focus.(ABSTRACT TRUNCATED AT 250 WORDS)
Adult↗
Entrainment of circus movement tachycardia utilizing an accessory pathway with long retrograde conduction times during ventricular and atrial stimulation.
An unusual case is presented in which a circus movement tachycardia incorporating an accessory pathway with long retrograde conduction time was transiently entrained. Overdrive high right atrial stimulation produced entrainment without atrial fusion since collision of anterograde and retrograde impulses took place within the accessory pathway. Tachycardia termination occurred when, at a faster pacing rate, an atrial impulse that collided in the accessory pathway was blocked at the atrioventricular (AV) node. In contrast, the entrainment seen during right ventricular apical stimulation was characterized by the occurrence of both fusion and collision within the ventricles. The tachycardia was terminated when a pure paced impulse that collided in the normal pathway was blocked in a retrograde direction in the accessory pathway. These data indicate that: 1) transient entrainment of this arrhythmia (circus movement tachycardia) can be identified by the classical criteria used to diagnose it, provided that fusion and collision occur within the ventricles; and 2) the accessory pathway is the weak link for tachycardia termination only during ventricular pacing since the AV node is the weak link during atrial stimulation.
Adult↗
Clinical characteristics of sudden death: implications for survival.
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Coronary Disease↗
[Pacing and right atrial ventricular dissociation in auricular stimulation in reciprocal tachycardia using an accessory pathway].
The effects of right atrial (RA) and coronary sinus (CS) stimulation have been studied in 13 patients with circus movement tachycardia (CMT). Tachycardia entrainment has occurred in all patients during RA pacing and in 11/13 during CS pacing, for a pacing rate 10 to 31 beats faster than the tachycardia rate. During RA pacing, short episodes of right atrial ventricular dissociation (6/13 patients) occurred but not during CS pacing. This can be explained by the anatomical proximity of the CS to the AV node (AVN) or by postulating two separate lateral inputs in the upper part of the AVN. Tachycardia entrainment is a criteria in favor of a reentry mechanism. It delineates a ranges of frequency between tachycardia rate and the slowest possible atrial stimulation rate capable of tachycardia termination which may be benefit for patients with drug resistant CMT, for whom antitachycardia pacemaker is envisaged.
Adolescent↗
Classification of ventricular arrhythmias based on parallel hierarchies of frequency and form.
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Arrhythmias, Cardiac↗
Annihilation, entrainment and modulation of ventricular parasystolic rhythms.
Annihilation and one-to-one entrainment of modulated parasystolic rhythms in humans has not been previously discussed. In 9 nonmedicated patients, it was possible to measure the intrinsic, parasystolic ectopic cycle length given by the intervals between 2 consecutive parasystolic beats without any interposed nonparasystolic beat. The corresponding values varied between 960 and 2,350 ms (corresponding to rates between 62 and 26 beats/min). In addition, modulation could be determined, because nonparasystolic beats falling during the initial 59% of the cycle prolonged the parasystolic cycle length (by 12 to 37.5%), whereas those that fell later in the cycle shortened it (by 9 to 25%). Plotting this prolongation or shortening as a function of the temporal position of the nonparasystolic beats in the cycle yielded biphasic response curves, of which 7 were symmetric and 2 asymmetric. In 2 patients, episodes of concealed one-to-one entrainment were initiated by late nonparasystolic (sinus) beats and, later on, terminated by early ventricular extrasystoles. In 2 other patients (and in 2 separate occasions) nonparasystolic beats, falling in part of the cycle located in between those of maximal delay and acceleration, produced pacemaker annihilation (cessation of automatic activity for the remaining monitoring time). Parasystolic annihilation and concealed entrainment may be one of the causes that can explain the large, spontaneous, day-to-day variability in the incidence of ectopic ventricular beats reported in Holter recordings. Nevertheless, future prospective studies performing interventions that can change the sinus and ectopic rates are required to corroborate our finding.
Arrhythmias, Cardiac↗
Entrainment of atrioventricular nodal reentrant tachycardias during overdrive pacing from high right atrium and coronary sinus. With special reference to atrioventricular dissociation and 2:1 retrograde block during tachycardias.
Entrainment was attempted during electrophysiologic evaluation of 8 patients with atrioventricular (AV) nodal reentrant tachycardia. Entrainment could be performed while pacing from the high right atrium in 35 of 35 episodes, from proximal coronary sinus in 9 of 21 episodes and from distal coronary sinus in 10 of 20 episodes. The minimal rates required were 8 to 40 beats/min faster than those of the tachycardias. That the atria (as defined in electrophysiologic studies) were not a necessary component of the reentry circuit was suggested by the occurrence, during tachycardia, of short episodes of AV dissociation and of 1 episode of 2:1 retrograde block. For the tachycardia to be interrupted, the pacing rate usually had to be slightly faster than that required to entrain, as well as sufficiently rapid to produce anterograde block of an atrial impulse in the slow AV nodal pathway. Moreover, termination of tachycardia apparently was a function of the pacing site. In some episodes, either because of a proximity effect or because of a preferential input into the upper common pathway, coronary sinus pacing terminated the tachycardia at slower rates or with fewer stimuli than high right atrial pacing. Thus, patients with drug-resistant AV nodal reentrant tachycardias may benefit from recently introduced pacing techniques for termination of tachycardia through entrainment.
Adolescent↗
Outcome of resuscitation from bradyarrhythmic or asystolic prehospital cardiac arrest.
Previous studies of outcome as a function of the initial electrophysiologic mechanisms recorded at the scene of prehospital cardiac arrest have demonstrated that bradyarrhythmias and asystole have the worst prognosis. In this report, our observations in bradyarrhythmic and asystolic arrests occurring from 1980 to 1982 are compared with those from 1975 to 1978. From 1980 to 1982, 61 (27%) of 225 cardiac arrest events meeting entry criteria for the study were bradyarrhythmic or asystolic. Only 2 (8%) of 24 patients with asystole and 1 (20%) of 5 patients with sinus bradycardia survived prehospital intervention. Only 1 of these 29 patients was discharged from the hospital alive. In contrast, 15 (47%) of 32 patients who presented with idioventricular rhythm at initial contact survived prehospital intervention and were hospitalized, and 8 (25%) of these 32 were ultimately discharged alive. When compared with the 1975 to 1978 patients with bradyarrhythmia and asystole, both prehospital survival (8 versus 30%, p less than 0.001) and survival after hospitalization (0 versus 15%, p less than 0.05) significantly improved, but the improvement occurred predominantly in the subgroup with idioventricular rhythm. Survivors within this subgroup tended to have a prompt response to prehospital pharmacologic interventions that were not available to the 1975 to 1978 group. The response was manifested by return to a sinus mechanism or increase in the rate of idioventricular rhythm. In conclusion, outcome has improved for a specific subgroup of victims of prehospital cardiac arrest with bradyarrhythmia or asystole; the improved outcome may relate to field interventions by rescue personnel at the scene of arrest but the mortality rate is still high.
Adult↗
Right atrial-ventricular dissociation and entrainment while pacing from high right atrium and coronary sinus during circus movement tachycardias.
Thirteen patients with circus movement tachycardias (CMT) were studied. Twelve had left-sided, and one, right-sided, accessory pathways. Entrainment was possible during overdrive high right atrial stimulation in 13/13 patients, and during coronary sinus pacing in 10/12 patients. The minimal pacing rates required for this to occur were 10 to 31 beats/min faster than those of the tachycardias. Short episodes of right atrial-ventricular dissociation occurred while pacing from the high right atrium (6/13 patients), but not from the coronary sinus (0/13 patients). It is possible to explain this phenomenon by postulating the existence of two distinct atrioventricular (AV) nodal inputs (one for right-sided and the other for left-sided impulses); it could also have been an expression of the close distance existing between the AV node and the coronary sinus. Entrainment, by defining a range of pacing rates followed by resumption of the tachycardia upon the cessation of stimulation, indicated that faster rates were needed for the CMT to be interrupted. However, regardless of the pacing rate and pacing site, tachycardia termination occurred when an anterograde impulse was blocked at the AV node. The information obtained from this study suggests that some patients with drug-resistant CMT may benefit from pacing modes capable of terminating the arrhythmia "through entrainment" at the slowest atrial rate at which this is possible.
Adolescent↗
Prehospital cardiac arrest survivors: classification of risk groups on the basis of electrophysiologic testing.
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Anti-Arrhythmia Agents↗
Long-term survival after prehospital cardiac arrest: analysis of outcome during an 8 year study.
We analyzed long-term follow-up data accumulated during an 8 year study of survivors of prehospital cardiac arrest. All patients included in this study were primary entrants via community-based rescue systems; patients who were tertiary referrals (survivors of cardiac arrest from other hospitals) were not included in this analysis. In the group of 61 patients entering our study between 1975 and 1980, with a follow-up to 1983, there have been a total of 24 deaths (39%). Sixteen of the 24 deaths were the result of recurrent cardiac arrest; eight were nonsudden cardiac deaths or noncardiac deaths. The mean duration from entry to death in the nonsurvivors was 27.5 +/- 19.7 months, and the time from the index event to last follow-up in the long-term survivors was 59.9 +/- 19.4 months. Life table analysis demonstrated a 10% rate of recurrence of cardiac arrest in the first year, with a 5% per year rate in each of the subsequent 3 years. Left ventricular ejection fractions at entry were not significantly different between survivors (mean = 45.3 +/- 13.6%) and nonsurvivors (mean = 37.6 +/- 12.6%), and the severity of ejection fraction abnormality at entry did not correlate with time to death in the nonsurvivors. However, ejection fraction was significantly lower in patients who died from causes other than recurrent cardiac arrest than in those who died of cardiac arrest (24.5 +/- 9.1% vs 42.7 +/- 9.2%; p less than .002).(ABSTRACT TRUNCATED AT 250 WORDS)
Anti-Arrhythmia Agents↗