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Biomedical subjects

P Denes

Publications and source records attributed to P Denes.

At least 109 records · Page 6Linked to original sources
PubMed1978

Self-initiated conversion of paroxysmal atrial flutter utilizing a radio-frequency pacemaker.

A patient is described with drug-resistant recurrent paroxysmal atrial flutter. Electrophysiologic studies demonstrated that flutter was inducible with rapid atrial stimulation (stimulation rates of 375 to 400/min) and convertible with rapid atrial stimulation (rates of 400 to 460/min). Because of the latter response, a radio-frequency atrial pacemaker was implanted, which allowed self-initiated conversion of flutter episodes with rapid stimulation.

Arrhythmias, Cardiac↗
PubMed1978

Electrophysiologic effects of lidocaine on sinus node and atrium in patients with and without sinoatrial dysfunction.

Electrophysiological studies were conducted in 13 patients with normal sinus node function and 14 with sinus node dysfunction before and after intravenous lidocaine. Mean +/- SEM sinus cycle length significantly shortened from 810 +/- 34.3 to 774 +/- 34.3 msec in patients with normal sinus node (P less than 0.001) and from 1061 +/- 67.6 to 1016 +/- 64.5 msec in patients with sinus node dysfunction (P less than 0.025) after lidocaine. Mean sinus recovery time was 1027 +/- 49.4 before and 1026 +/- 52.5 msec after lidocaine in patients with normal sinus node (NS) and 1269 +/- 97.7 before and 1170 +/- 73.8 msec after lidocaine in patients with sinus node dysfunction (P less than 0.05). Mean calculated sinoatrial conduction time was 87 +/- 9.5 before and 90 +/- 9.2 msec after lidocaine in patients with normal sinus node (NS) and 80 +/- 10.3 before and 96 +/- 10.2 msec after lidocaine in patients with sinus node dysfunction (P less than 0.001). Mean atrial effective and functional refractory periods were not significantly changed with lidocaine. Thus lidocaine shortened sinus cycle length in both groups, without affecting atrial refractoriness. Lidocaine appeared to depress perinodal tissue only in patients with sinus node dysfunction. The abbreviation of sinus recovery time in patients with sinus node dysfunction could reflect increased sinus automaticity and/or increased perinodal refractoriness, allowing entrance block to occur. This mechanism may explain why sinus arrest has been noted in some patients during lidocaine administration.

Adult↗
PubMed1978

Electrocardiographic changes in concussion.

A patient is described in whom electrocardiographic changes simulating acute nontransmural myocardial infarction occurred in association with head trauma. Despite extensive noninvasive investigation, including computerized axial tomography and myocardial scanning, no acute structural central nervous system or cardiac abnormality could be detected. A review of the literature failed to reveal a similar case of these electrocardiographic changes occurring in the absence of organic brain or cardiac pathology.

Aged↗
PubMed1978

A characteristic precordial repolarization abnormality with intermittent left bundle-branch block.

We reviewed electrocardiograms of 23 patients with intermittent left bundle-branch block. A characteristic electrocardiographic pattern consisting of right and mid-precordial deep symmetrical T-wave inversions was detected during normal conduction in 19 of the 23. Of the seven patients who had cardiac catheterization, only two had findings suggestive or organic heart disease and only one had significant obstructive coronary disease. Thus we conclude that patients with intermittent left bundle-branch block frequently have T-wave inversions in right and mid-precordial leads during normal conduction that do not necessarily reflect coronary disease. These T-wave changes are similar to those after termination of chronic right ventricular pacing (left bundle-branch pattern), suggesting that both patterns of abnormal ventricular activation can produce abnormal repolarization when activation returns to normal.

Adult↗
PubMed1977

Arrhythmias documented by 24 hour continuous electrocardiographic monitoring in 50 male medical students without apparent heart disease.

Results are reported of portable 24 hour dynamic electrocardiographic monitoring in 50 male medical students without cardiovascular disease, as defined by normal clinical and noninvasive cardiovascular examination. During waking periods, maximal sinus rates ranged from 107 to 180 beats/min (mean +/- 5). Twenty-five subjects (50 percent) had episodes of marked sinus arrhythmia as defined by spontaneous changes in adjacent cycle lengths of 100 percent or more. Fourteen subjects (28 percent) had sinus pauses of more than 1.75 seconds, usually during sinus arrhythmia. Transient nocturnal type I second degree atrioventricular (A-V) block was noted in three subjects (6 percent). Of 28 patients (56 percent) having atrial premature beats, only 1 (2 percent) had more than 100 such beats (141) in 24 hours. Of 25 patients (50 percent) having premature ventricular contractions, only 1 (2 percent) had more than 50 such contractions (86) in 24 hours. In conclusion, frequent atrial and ventricular premature beats are unusual in a young adult male population. In contrast, bradyarrhythmias (including marked sinus arrhythmia with sinus pauses, sinus bradycardia and nocturnal A-V block) are common. These findings are useful in evaluating the clinical significance of arrhythmias detected with portable monitoring.

Adult↗
PubMed1977

Atrial pacing at multiple sites in the Wolff-Parkinson-White syndrome.

Atrial pacing at multiple sites was used in an attempt to predict the site of pre-excitation in 5 patients with Wolff-Parkinson-White syndrome with 5 different anomalous pathway locations (right anterior, right posterior, septal, left posterior, and left lateral). At least 3 atrial pacing sites were tested in each patient. Pacing sites tested included high right atrium, low lateral right atrium, low septal right atrium, proximal coronary sinus, and distal coronary sinus. Atrial stimulation sites with shortest and longest stimulus-delta intervals could be identified in each patient, the shortest stimulus-delta interval in each case ranging from 60 to 80 ms. The difference between the shortest and longest stimulus-delta interval in each case ranged from 60 to 110 ms. It was suggested that the site with the shortest stimulus-delta interval corresponded to a site close to the atrial insertion of the anomalous pathway. This hypothesis was confirmed in all cases (3 with epicardial mapping and 2 with retrograde atrial activation data). In conclusion, atrial pacing at multiple sites is helpful in predicting the site of anterogradely conducting anomalous pathways, and appears particularly useful for differentiation of right posterior, left posterior, and septal pre-excitation.

Adolescent↗
PubMed1977

Effect of anomalous pathway location on rate of canine experimental A-V reentrant tachycardia.

The effect of anomalous pathway (AP) location and conduction time on the cycle length (CL) and sustainability of paroxysmal A-V reentrant tachycardia was studied in 15 dogs, using an anomalous pathway simulator (APS). The APS was a programmable digital electronic circuit with ability for unidirectional conduction, ventricular sensing, adjustable delay, and atrial stimulation. Contiguous pairs of ventricular sensing electrodes were placed along the A-V ring in each dog at the following sites: anterior, posterior, and lateral right (AR, PR, and LR) and anterior, posterior, and lateral left (AL, PL, and LL) and septal (S). There were significant differences in the CL of tachycardias among the tested sites (P less than 0.01). The CL of tachycardias from the LL site was significantly longer and from the PR site significantly shorter than that from the other sites (P less than 0.05). These differences in CL of tachycardias in relation to the AP location were explicable in terms of corresponding variation in conduction times of the various components of the tachycardia circuit (e.g., intra-atrial, A-V nodal, intraventricular conduction times). The differences in magnitude of the CL of tachycardias, although significant, were small. It was also found that all sites allowed maintenance of tachycardias up to an AP conduction time of 10 ms. In 27% of experiments, atrial refractoriness prevented sustained tachycardias at pathway delays of 1 ms. The relationship between AP conduction time and CL of tachycardias was exponential.

Animals↗
PubMed1977

Clinical significance of prolonged sinoatrial conduction time.

Prolonged (greater than 152 msec) calculated sinoatrial conduction times (SACT) were found in 24 of 470 patients studied by the atrial extrastimulus technique, ranging from 155 to 220 msec (180+/-4.4; mean+/-SEM). There were 18 males and six females with ages of 29 to 85 (mean 65+/-2.6). Electrocardiographic monitoring revealed significant sinus or atrial dysrhythmias in 19 (79%) patients. Of these 19, 15 had persistent sinus bradycardia and/or sinoatrial block, three had sinus bradyarrhythmia with paroxysmal atrial tachycardia, and one had isolated atrial tachycardia. Additional electrophysiological evidence of sinus node or atrial dysfunction was present in 11 patients. Four patients needed permanent pacing during follow-up (mean follow-up period of 427+/-39 days) because of symptomatic bradyarrhythmia. Three patients died, none suddenly. In conclusion, prolonged calculated SACT was associated with a high incidence of electrocardiographic and electrophysiologic abnormalities of sinus node and/or atrium. Despite this, bradyarrhythmic morbidity was relatively low, suggesting that prolonged sinoatrial conduction time in the absence of symptoms is not an indication for prophylactic pacing.

Adult↗
PubMed1977

Effects of cycle length on atrial vulnerability.

The effect of cycle length on atrial vulnerability was studied in 14 patients manifesting reproducible repetitive atrial firing during atrial extra-stimulus (A2) testing. Repetitive atrial firing was defined as the occurrence of two or more premature atrial responses with return cycle (A2-A3) of 250 msec or less and subsequent mean cycle length of 300 msec or less, following A2. The zone of repetitive atrial firing could be defined in terms of its longest and shortest A1-A2 coupling intervals. Each patient was tested at a long cycle length (CL1) (mean 884 msec) and a short cycle length (CL2) (mean 557 msec). CL1 was sinus rhythm and CL2, an atrial paced rhythm. Repetitive atrial firing occurred in two patients at CL1 and in all patients at CL2. Of the former two patients (group 2), the zone of repetitive atrial firing was markedly widened in one at CL2 due to a shortening of atrial functional refractory period (FRP) at CL2. In the other, zone of repetitive atrial firing could not be totally defined due to induction of sustained atrial flutter preventing definition of atrial FRP. The occurrence of repetitive atrial firing at only CL2 in 12 patients (group 1) reflected: 1) a shortening of atrial FRP from 294 +/- 11 msec at CL1 to 242 +/- 10 msec at CL2 (mean +/- SEM; P less than 0.01), allowing delivery of A2 at shorter coupling intervals (9); 2) the new occurrence of repetitive atrial firing at A1-A2 coupling intervals achievable at both cycle lengths (1); or 3) both effects (2). In conclusion, decrease of cycle length potentiated atrial vulnerability. This demonstration implies that atrial pacing could potentiate occurrence of paroxysmal atrial fibrillation or flutter.

Adult↗
PubMed1977

Participation of fast and slow A-V nodal pathways in tachycardias complicating the Wolff-Parkinson-White syndrome. Report of a case.

Electrophysiological studies in one patient with type B pre-excitation and dual A-V nodal pathway revealed several types of paroxysmal narrow QRS tachycardia (PSVT). One type of PSVT reflected antegrade fast A-V nodal pathway and retrograde anomalous pathway conduction. This PSVT was characterized by early retorgrade activation of right atrial appendage, P following QRS and cycle length of 290 to 350 msec. A second PSVT reflected antegrade slow A-V nodal pathway and retrograde anomalous pathway conduction. This PSVT was characterized by early retrograde activation of right atrial appendage, P following QRS, and cycle length of 440 msec. A third PSVT reflected A-V nodal re-entrance with antegrade slow pathway and retrograde fast pathway conduction. This PSVT was characterized by normal retrograde atrial activation sequences, P simultaneous with QRS, and cycle length of 320 msec. All PSVT inductions could be explained in terms of antegrade and retrograde properties of fast and slow A-V nodal and anomalous pathways.

Adult↗