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At least 667 records · Page 37Linked to original sources
PubMed1999

A new defibrillator discrimination algorithm utilizing electrogram morphology analysis.

Inappropriate therapies delivered by implantable cardioverter defibrillators (ICDs) for supraventricular arrhythmias remain a common problem, particularly in the event of rapidly conducted atrial fibrillation or marked sinus tachycardia. The ability to differentiate between ventricular tachycardia and supraventricular arrhythmias is the major goal of discrimination algorithms. Therefore, we developed a new algorithm, SimDis, utilizing morphological features of the shocking electrograms. This algorithm was developed from electrogram data obtained from 36 patients undergoing ICD implantation. An independent test set was evaluated in 25 patients. Recordings were made in sinus rhythm, sinus tachycardia, and following the induction of ventricular tachycardia and atrial fibrillation. The arrhythmia complex is defined as wide if the duration is at least 30% greater than the template in sinus rhythm. For narrow complexes, four maximum and minimum values were measured to form a 4-element feature vector, which was compared with a representative feature vector during normal sinus rhythm. For each rhythm, any wide complex was classified as ventricular tachycardia. For narrow complexes, the second step of the algorithm compared the electrogram with the template, computing similarity and dissimilarity values. These values were then mapped to determine if they fell within a previously established discrimination boundary. On the independent test set, the SimDis algorithm correctly classified 100% of ventricular tachycardias (27/27), 98% of sinus tachycardias (54/55), and 100% of episodes of atrial fibrillation (37/37). We conclude that the SimDis algorithm yields high sensitivity (100%) and specificity (99%) for arrhythmia discrimination, using the computational capabilities of an ICD system.

Algorithms↗
PubMed1994

Elimination of AV nodal reentrant tachycardia with 2:1 VA block by posteroseptal ablation.

AV nodal reentry capable of VA block during tachycardia was successfully eliminated using a posteroseptal ablation pulse delivered well away from the site of earliest atrial activation during tachycardia. A possible explanation is that the arrhythmia represented typical AV nodal reentrant tachycardia with transient intra-atrial conduction block during tachycardia.

Catheter Ablation↗
PubMed1979

Atrial infarction leading to rupture.

In the case described, necrosis of the atrial musculature led to rupture of the chamber. This was overlooked for 4 days until the patient died of ventricular rupture. This unusual complication of atrial infarction may be amenable to surgical repair if recognised in time. The high gain recording of P waves in the presence of AV block made it possible to evaluate the P wave changes during atrial infarction: (1) changes in the configuration and width of the P wave, probably resulting from intra-atrial conduction defect; (2) depression of the PR segment (0.04 to 0.07 mV); and (3) a previously unrecorded convexity in the first portion of the PR segment, in the leads in which the depression of the PR segment was observed.

Aged↗
PubMed1968

Atrial reciprocal rhythm and reciprocating tachycardia in Wolff-Parkinson-White syndrome.

In an infant with type A Wolff-Parkinson-White syndrome, atrial reciprocal beats and attacks of reciprocating tachycardia were repeatedly recorded. Their dependence on a prolongation of the P-R interval could be well demonstrated during Wenckebach periods. Because of the normal aspect of the QRS complex during arrhythmia, the short ventriculo-atrial conduction time (0.08 sec), and the vectorial orientation of the secondary P wave, it was concluded that retrograde reactivation of the atria probably took place via the anomalous bundle. The versatility of the conduction through the accessory bundle is shown by the fact that its direction may change from antegrade in one beat to retrograde in the next. The importance of a circus movement in the genesis of some types of tachycardia in the WPW syndrome is discussed.

Atrioventricular Node↗
PubMed1977

Sudden death after repair of tetralogy of Fallot. Electrocardiographic and electrophysiologic abnormalities.

In order to try to determine the mechanism of sudded death in patients after surgical repair of tetralogy of Fallot, electrocardiographic, intracardiac electrophysiologic, and clinical data of 51 children who had postoperative intracardiac electrophysiologic studies were reviewed. Ninety-four percent had developed right bundle branch block (RBBB) and 16 percent had additional left anterior hemiblock (LAH). Two had had transient complete A-V block (CAVB) and one had permanent CAVB. Six had a first degree A-V block and nine had premature ventricular contractions (PVC). Nine patients were found to have prolonged intra-atrial conduction times, four prolonged A-V nodal conduction, four prolonged His-Purkinje conduction, and five prolonged corrected sinus node recovery times. Patients with first degree A-V block or LAH did not have an increased incidence of abnormalities on electrophysiologic study. No patient with RBBB and LAH developed complete A-V block or died. Three of the nine patients with PVCs died, one of intractable ventricular fibrillation and two suddenly, presumably of dysrhythmia. All three had significant congestive heart failure. Although late complete A-V block occurs and should be watched for, ventricular dysrhythmias in patients with PVCs may be the cause of most sudden deaths after tetralogy repair. We currently are treating all of our postoperative tetralogy patients who have PVCs with quinidine or propranolol.

Adolescent↗
PubMed1993

Predictors of major vascular events in patients with a transient ischemic attack or nondisabling stroke. The Dutch TIA Trial Study Group.

BACKGROUND AND PURPOSE: Very few studies have addressed the identification of prognostic factors in patients with a transient ischemic attack or minor stroke. METHODS: We prospectively studied the prognostic value of clinical, laboratory, radiological, and electrocardiographic findings in 997 patients with a transient ischemic attack and 2,130 patients with a minor stroke who were entered into a multicenter clinical trial. The mean follow-up period was 2.6 years. RESULTS: A total of 302 patients died (212 from a vascular cause), 272 had a stroke, and 200 had a cardiac event. By means of a multivariate analysis we identified the following independent risk factors for stroke, myocardial infarction, or vascular death: age of > 65 years; male sex; dysarthria; multiple attacks; diabetes; angina pectoris; intermittent claudication; computed tomographic evidence of any cerebral infarct, especially a border zone infarct or white matter hypodensity; and electrocardiographic evidence of an anteroseptal infarct, ST depression, left ventricular hypertrophy, or left atrial conduction delay. Protective predictors were monocular attacks only or the presence of rotatory dizziness. CONCLUSION: A limited number of easily obtainable characteristics are powerful predictors of major vascular events in patients with cerebral ischemia.

Aged↗
PubMed1992

Sinus node function in hyperthyroid patients.

We have studied the electrophysiology of the sinus node and the role of the autonomic nervous system on sinus node function in 8 thyrotoxic patients of both sexes, 37.5 +/- 4.3 (mean +/- SE) yr old. The resting heart rate (RHR), the sino-atrial conduction time (SACT), and the sinus node recovery time (SNRT) were measured in the untreated condition (basal), after sympathetic blockade with propranolol 0.2 mg/kg body weight (BW) i.v. infusion, and after complete autonomic blockade with the additional administration of atropine 0.04 mg/kg BW i.v. bolus. 1) In the thyrotoxic patients the RHR was higher [117 +/- 6 beats per min (bpm)] than in 20 normal subjects (73 +/- 1 bpm, P less than 0.001), whereas the SACT and SNRT values were not different. 2) After sympathetic blockade with propranolol, the RHR decrement and SACT increase were greater in the hyperthyroid patients than in normal subjects, whereas there was no difference in SNRT values between the two groups. 3) In the thyrotoxic patients the complete autonomic blockade reestablished the electrophysiological parameters to values similar to those observed in basal condition. In conclusion, in thyrotoxic patients the intrinsic activity of the sinus node is increased. It appears that this is a direct consequence of thyroid hormone excess, rather than an effect of extrinsic influences exerted by the autonomic nervous system on sinus node activity.

Adolescent↗
PubMed1981

Effect of ouabain on electrical coupling of rabbit atrial muscle fibers.

The effects of ouabain on passive electrical properties of isolated rabbit atrial muscle fibers (crista-terminalis) were investigated. The space constant as well as the time constant of the crista-terminalis was determined using the partition method of Kamiyama and Matsuda based on the cable equation proposed by Hodgkin and Rushton. Ouabain treatment for 30 minutes at a lower concentration (2 X 10(-7) M), caused no significant change in the space constant and time constant of the crista-terminalis. After ouabain treatment for 30 minutes at a higher concentration (1 X 10(-6) M), the space constant of the crista-terminalis was reduced significantly, whereas the time constant was not affected. An apparent reduction in the resting membrane potential and the amplitude of action potential was also observed at the higher concentration of ouabain. These effects of ouabain on passive electrical properties of the crista-terminalis are most likely explained by the increase of its axial resistance (electrical uncoupling) due to intracellular calcium accumulation resulting from inhibition of the membrane sodium pump. This suggests that such an electrical uncoupling may play an important role in the intra-atrial conduction disturbance by cardiac glycosides.

Action Potentials↗
PubMed1983

The effect of pacing site on the echo zone in patients with concealed Wolff-Parkinson-White syndrome.

In 14 patients with the left-sided concealed Wolff-Parkinson-White syndrome, the effects of changing atrial pacing site on the echo zone were evaluated. In 12 patients, re-entrant tachycardia was induced by premature stimuli both in the coronary sinus (CS) and the high right atrium (HRA). In the remaining 2 patients, the tachycardia was induced by premature stimuli only in the CS. The lower limit of the echo zone was shifted to a longer coupling interval during CS pacing in 12 patients. The longer effective refractory period (ERP) of the CS was responsible for the shifting of the lower limit of the echo zone to a longer coupling interval. The upper limit of the echo zone was shifted to a longer coupling interval during CS pacing in 10 patients. The difference of atrial conduction times from the site of stimulation to the 2 conduction pathways (the normal conduction pathway and the accessory pathway) is thought to be responsible for the shifting of the upper limit of the echo zone.

Adult↗
PubMed1976

[Paroxysmal ventricular tachycardia with retrograde Wenckebach block and reciprocal beats (author's transl)].

A case of recurrent paroxysmal ventricular tachycardia with retrograde Wenckebach block and reciprocal beats was studied with His bundle electrogram and right ventricular stimulation. Reentry was reproduced whenever retrograde ventriculo-atrial conduction time reached a critical value. Concealed reentry was also demonstrated and shown to be responsible for the dropped beats of the Wenckebach sequence.

Bundle of His↗
PubMed1978

[Electrophysiological effects of chloroacetyl ajmaline in Wolff-Parkinson-White syndrome].

The electrophysiological effects of chloro-acetyl-ajmaline in the Wolff-Parkinson-White syndrome have been studied in 7 patients after an intravenous dose of 1.5 mg/kg of the drug. Preexcitation was abolished in 3 cases, while 3 other subjects showed a slight increase in effective refractory period of the abnormal route of excitation (a mean of 13 ms). The possibility of bringing about a reciprocal rhythm was removed in one case out of two. During tachycardia, chloro-acetyl-ajmaline produced significant lengthening of the ventriculo-atrial conduction time (p less than 0.05). These results show the usefulness of chloro-acetyl-ajmaline in the control of the arrhythmias associated with the Wolff-Parkinson-White syndrome.

Adolescent↗
PubMed2000

Effects of concentrated ambient particles in rats and hamsters: an exploratory study.

Considerable controversy surrounds the biological plausibility of adverse effects from exposure to ambient particulate matter (PM)*, chiefly because these adverse effects have been observed at particle mass concentrations below those that have been shown to produce effects in healthy animals and human volunteers in the laboratory. To address this research gap, we examined the potential for concentrated ambient PM to produce pulmonary and cardiovascular changes in compromise rodent models. Normal healthy and monocrotaline-treated rats received single or multiple exposures to concentrated ambient PM, and their responses were tested using functional, cellular, biochemical, and histological endpoints. Analyses determined that no changes in pulmonary function or structure occurred after exposure to concentrated ambient PM. Cardiac arrhythmias did not increase after PM exposure in normal or monocrotaline-treated rats. Increased atrial conduction time, accompanied by a decrease in the duration of the T wave portion of the electrocardiogram (ECG) waveform, was observed in PM-exposed monocrotaline-treated rats in one experiment. In addition, on several but not all exposure days, small yet statistically significant increases in heart rate and peripheral blood cell differential counts were observed in normal and monocrotaline-treated rats within 6 hours after exposure to concentrated ambient PM. The observed changes in cardiovascular parameters in rats returned to control values by 24 hours after exposure. In a hamster cardiomyopathy model, no adverse cardiac or pulmonary changes were detected after exposure to concentrated ambient PM. Thus, these studies found that cardiopulmonary effects could be produced in rats, but not in hamsters with cardiomyopathy, exposed to concentrated ambient PM. None of the changes occurred on every exposure day and none appeared to be life threatening. Thus, the cardiac changes may reflect changes in homeostasis that could affect individuals who are critically ill, and these findings do not resolve the biological plausibility of adverse health effects associated with ambient PM in epidemiologic studies.

Age Factors↗
PubMed1979

[The incidence of concealed accessory atrioventricular pathways in paroxysmal junctional tachycardias].

Forty patients with normal resting ECGs and a history of paroxysmal junctional tachycardia underwent endocavitory electrocardiography. Accessory atrioventricular pathways were demonstrated in 34 patients (82.5%), 14 of whom (35%) had Kent bundles. The ventriculo-atrial conduction time during ventricular stimulation was constantin 85% of the 40 patients but increased after injection of striadyne (ATP). This may suggest a reentry circuit partially bypassing the atrioventricular node.

Adenosine Triphosphate↗
PubMed2003

[Diagnosis and treatment of sinoatrial node dysfunction].

Sick sinus syndrome is characterized by disturbance of its automatic function and (or) sinu-atrial conductivity caused by organic or vegetative defects. Diagnostic algorithm includes: clinical evidence, ECG, Holter monitoring, electrophysiological investigation, pharmacological test. Treatment is pharmacological and surgical.

Anti-Arrhythmia Agents↗
PubMed1992

[Lipomatous hypertrophy of the interatrial septum. Report of 2 cases diagnosed in vivo].

Lipomatous hypertrophy of intervenous tubercle is a clinicopathological entity characterized by an accumulation of not capsulated fatty tissue, with its thickness exceeding 15 mm, in the atrial septum, above the fossa ovalis, at the intervenous level and protruding into the right atrium. It can be clinically associated with atrial electric abnormalities such as disorders of the atrial conduction and supraventricular arrhythmias, difficulty of the venous return and sudden death. Nowadays its diagnosis is not difficult using non invasive image techniques. We present two cases of lipomatous hypertrophy of intervenous tubercle which were suspected by echocardiography. In one of them we used transthoracic echocardiography and in the other one transesophageal echocardiography. The diagnostic was latter confirmed by magnetic nuclear resonance and axial computerized tomography.

Aged↗
PubMedDate not supplied

Sinus node dysfunction in children.

Seven out of 829 pediatric cardiac patients (0.84%) were found to have sinus node dysfunction (SND) over the past seven years. Of the seven patients, three had structurally normal hearts. One of these three patients had long QT syndrome. In four patients, structural heart disease was noted. In three of these four patients the sinus node dysfunction was attributed to cardiac surgery. The age of onset of SND ranged from four months to eight years. Presenting symptoms and signs included syncope, near-syncope, seizure and congestive heart failure. Two patients were asymptomatic. Five patients had episodic sinus pause. Sinus or junctional bradycardia was noted in four patients. Three had tachy-bradycardia. High grade atrioventricular block was noted in one patient. Treadmill exercise test revealed a nonsustained ventricular tachycardia in two patients. All seven patients were found to have prolonged maximal corrected sinus node recovery time. Prolonged intra-atrial conduction time was found in three, prolonged AV nodal conduction time in one, and prolonged His-Purkinje conduction time in one patient during the electrophysiologic study. All seven patients showed abnormal results in intrinsic heart rate study. Anti-arrhythmic drugs were prescribed. During the follow-up study, no patient died, but two patients received a pacemaker implantation. Because of the extent of their conduction system diseases, it is recommended that patients with SND should be thoroughly investigated.

Child↗
PubMed1992

[A clinical study of induction rate of atrioventricular reciprocating tachycardia in WPW syndrome].

The differences in induction rate of atrioventricular reciprocating tachycardia (AVRT) were analyzed in 76 consecutive patients of WPW syndrome with tachycardia attack, confirmed by either ECG or history, and who underwent electrophysiological study. AVRT was induced by programed electrical stimulation in 72% of patients with manifest WPW syndrome, in 77% of patients with intermittent WPW syndrome, and in 96% of patients with concealed WPW syndrome, respectively. There was a significant difference in induction rate between manifest WPW syndrome and concealed WPW syndrome (p less than 0.05). Induction rate of AVRT in patients with accessory pathway (AP) located in the ventricular septum was significantly lower (50%) than in patients with AP located in the left ventricle (88%) and in the right ventricle (72%) (p less than 0.05). Ventricular atrial conduction was found in only 56% of patients with AP located in the ventricular septum, while it was found in 94% of patients with AP located in the left ventricle, and in 100% of patients with AP located in the right ventricle (p less than 0.05). There were no significant differences in antegrade effective refractory periods of atrioventricular node and AP between patients with and without inducible AVRT. There was also no significant difference in the retrograde effective refractory periods of AP between patients with or without inducible AVRT. We concluded that the induction rate of AVRT would be affected by the location of AP and the mode of delta wave appearance in the surface electrocardiogram.

Adult↗
PubMed2005

[Electrophysiological and hemodynamic consequences of pacemaker syndrome].

The pacemaker syndrome is a complex of adverse clinical, hemodynamic and electrophysiologic signs temporally related to the onset of ventricular pacing and having no other causes. We observed 975 patients (454 men and 251 women, mean age 67.1+/-2.4 years) who received ventricular VVI pacemakers because of sick sinus syndrome or complete atrio-ventricular block. The presence of ventriculo-atrial conduction was confirmed by transesophageal ECG. Pacemaker syndrome was diagnosed in 121 patients (12.4%) who had the following complaints: general weakness (n=82), rapid fatigability (n=51), retarded thinking (n=43), dizziness (n=75), exertional dyspnea (n=86), anginal pain at rest (n=14), or exertion (n=43), unpleasant pulsation of neck vessels (n=41), transient hypotension (n=54), syncope (n=5). Retrograde P-wave was registered in standard ECG-leads in 98 (80.9%) and only on transesophageal ECG - in 23 patients (19%). Stroke volume after stopping of ventricular pacing (mean heart rate during sinus rhythm - 52.1+/-3/min) increased in 97 (80.2%) and decreased in 24 patients (19.8%). Main method of treatment of pacemaker syndrome was restoration of atrioventricular synchrony.

Aged↗