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PubMed1980

Ventricular tachycardia initiated by both normally and aberrantly conducted atrial premature beats.

Electrophysiologic studies were performed in a 72-year-old female with recurrent ventricular tachycardia in whom all documented spontaneous episodes were initiated by atrial premature beats. These studies confirmed the diagnosis of ventricular tachycardia and its initiation by atrial premature beats. Both normally and aberrantly conducted atrial premature beats were capable of initiating the tachycardia. With aberrant prematures the onset of the tachycardia was delayed in proportion to the delay in the right bundle branch. Triggered automaticity and re-entry were equally plausible as underlying mechanisms for this arrhythmia.

Aged↗
PubMed2001

Method for simultaneous epicardial and endocardial mapping of in vivo canine heart: application to atrial conduction properties and arrhythmia mechanisms.

INTRODUCTION: It has been suggested that the three-dimensional structure of the atria may be crucial in arrhythmogenesis; however, previous in vivo atrial activation mapping studies have been limited to either endocardial or epicardial approaches. METHODS AND RESULTS: To investigate the role of endocardial and epicardial structures and their interaction in atrial conduction and arrhythmias, we used five epicardial plaques and two intra-atrial balloon arrays to record a total of 368 unipolar electrograms from the entire epicardial and endocardial surface of both atria. During regular 1:1 pacing from the right atrial appendage, right atrial endocardial activation spread considerably faster than epicardial (total activation time 45+/-12 msec vs 60+/-19 msec, respectively [mean +/- SD]; P < 0.05), pointing to preferential conduction over structures like the crista terminalis and pectinate muscles. No such differences were noted in the left atrium. Transseptal spread occurred via discrete anterior and posterior pathways, causing separate breakthroughs in anterior and posterior atrial regions, respectively. Dissociation between septal pathways played a role in reentry during vagal atrial fibrillation. In 2 of 4 dogs with atrial fibrillation associated with congestive heart failure, single macroreentrant circuits involving endocardial and epicardial components were revealed during the arrhythmia. CONCLUSION: We conclude that activation mapping using simultaneous recording from both epicardial and endocardial surfaces provides potentially important insights into the mechanisms of atrial conduction and arrhythmogenesis.

Activation Analysis↗
PubMed1978

[The effect of diphenylhydantoin on the automatism of the sinus node and on the sino-atrial conduction time in patients with and without sick sinus syndrome].

In 30 test persons (15 patients with disturbed function of the sino-auricular node, 9 of them with classical sick-sinus-syndrome as well as 15 test persons without disturbance of the sino-auricular node, of them 7 healthy ones) the influence of diphenylhydantoin on the function of the sino-auricular node was tested. By means of atrial stimulation the so-called sino-atrial conduction time, the recreation time of the sino-auricular node as well as the duration of the sinus period before and after intravenous application of 250 mg of diphenylhydantoin was estimated. The auricular stimulation was carried out either through an oesophageal electrode probe or usually through an electrode catheter directly placed in the right atrium. In the entire collective the sino-atrial conduction time did prolong itself statistically not significantly by 2 +/- 5ms (x +/- 2 s), in which cases there was not to be observed a different behaviour between test persons with a healthy rhythm and patients with disturbed function of the sino-auricular node. In 2 patients with sick-sinus-syndrome, however, after diphenylhydantoin and individual atrial stimulation in each case sino-atrial blockings of higher degree developed. The maximum absolute and corrected recovery time of the sino-auricular node prolonged itself in patients with syndrome of the sino-auricular node by on an average 1406 +/- 2120 ms or 1378 +/- 2338 ms, in which cases in 1 test person a threatening prolongation of the poststimulation pause to 10 s developed. In another patient after application of diphenylhydantoin an atrial arrest was observed. The automatism of the sino-auricular node of test persons with healthy rhythm was not influenced.

Arrhythmia, Sinus↗
PubMed2001

Influence of atrial flutter ablation on right to left inter-atrial conduction.

AIMS: Ablation of the atrial isthmus between the tricuspid annulus and the inferior vena cava changes P-wave morphology during low lateral right atrial pacing. For better understanding of the mechanism of this alteration, the sequence of activation of the inter-atrial septum and the left atrium were compared before and after ablation of the isthmus between the inferior vena cava and the tricuspid annulus. METHODS AND RESULTS: In 13 patients, left atrial mapping was performed using a duodecapolar electrode catheter advanced to the far distal coronary sinus. The inter-atrial septum was mapped using a right atrial duodecapolar electrode catheter. Conduction times were measured during low lateral right atrial pacing from the pacing artefact and during sinus rhythm from the earliest right atrial electrogram to every intra-cardiac electrogram before and after the ablation. During low lateral right atrial pacing, isthmus ablation resulted in a significant delay in every left atrial lead. Changes were maximal at the posterior aspect of the left atrium and minimal at its anterior aspect. No significant change was discernible on the inter-atrial septum. During sinus rhythm, atrial activations remained unchanged. CONCLUSION: Electrocardiographic changes of P-wave morphology result from alteration in the sequence of left atrial activation rather than that of the inter-atrial septum.

Atrial Flutter↗
PubMed1993

[Frequency dependent prolongation of inter-atrial conduction time by mexiletine in human atrium].

To investigate frequency dependent conduction slowing by mexiletine in the human atrium, we examined inter-atrial conduction time (IACT) at different stimulation frequencies (100/min to 220/min) in 13 patients with paroxysmal atrial fibrillation (Paf) and 7 patients without Paf. IACT was prolonged as the stimulation frequency was increased, and either before or after mexiletine administration IACT was longer in the Paf group (max 114 +/- 9 msec, p < 0.01, mean +/- SD) at any stimulation frequency than in the non-Paf group (max 100 +/- 8 msec). The change in IACT induced by mexiletine administration (% delta IACT) was larger in the Paf group (max 14.8 +/- 5.4%, p < 0.05) than in the non-Paf group (max 5.5 +/- 2.2%) at stimulation frequency over 140/min. Effective refractory period measured at the high right atrium was slightly decreased due to mexiletine in both the non-Paf and the Paf group. In conclusion, mexiletine showed frequency dependent suppression of conduction in the human atrial myocardium especially in patients with Paf.

Adolescent↗
PubMed2003

Ventriculo-atrial conduction in the ovine heart, caused by premature ventricular complexes.

In humans, and certain animals, the atrioventricular conduction system is capable of bidirectional conduction. Depolarization impulses, originating in the ventricle itself, may thus be conducted in a retrograde direction towards the atria. Two common causes for this phenomenon of ventriculo-atrial (retrograde) conduction are premature ventricular complexes and ventricular pacing. The surface electrocardiogram can be used for the detection of such retrogradely conducted beats. The purpose of this study was to investigate the possibility of ventriculo-atrial conduction in Dorper sheep. Premature ventricular complexes in eight healthy Dorper wethers were induced and it was possible to document retrogradely conducted beats on the surface electrocardiogram in all of them. It is concluded that the Dorper sheep heart is capable of ventriculo-atrial conduction.

Animals↗
PubMed1998

The signal averaged P wave in atrioventricular block--evidence for abnormal atrial conduction?

The incidence of atrial fibrillation in patients with atrioventricular block (AVB) appears increased over that for the unpaced population even if atrioventricular synchrony is maintained by dual chamber pacing. To assess whether atrial fibrillation in these patients might be due to concurrent abnormality in atrial activation we performed signal averaged P wave (SAPW) recordings in 15 patients with dual chamber pacemakers implanted for AVB and compared the results to those from 21 unpaced controls. The median (range) age was 69 (53-89) years for patients and 60 (51-78) years for controls. Eleven patients and 12 controls were male. All patients were pacing in VDD mode at the time of study. SAPW recordings were obtained using our previously reported selective P wave averaging system. We measured P wave duration after high pass filtering at 40 Hz, the rate of change of P wave voltage over time (spatial velocity) and low and high frequency spectral energy after Fourier transformation of the P wave signal. We found increased P wave duration, mean spatial velocity and lower frequency energy in patients with AVB compared to controls [duration, 144 (5) vs. 134 (2) ms, p<0.05; mean spatial velocity, 5.6 (0.4) vs. 4.6 (0.1) mV/s, p<0.05; energy 20-150 Hz, 57.4 (8.2) vs. 36.3 (2.8) muV2.s, p<0.01. All values mean (SEM)]. These results suggest that the increased incidence of atrial fibrillation in patients paced for AVB may be related to intrinsic abnormalities of atrial activation and not solely to the pacing mode. Ensuring sequential atrioventricular pacing in these patients may not completely abolish the increased incidence of atrial fibrillation.

Aged↗
PubMed1976

[Interpretation of a bundle of His electrogram (using the spike potentials of the sinus node and atrial conduction tracts in the analysis)].

Spike potentials of the sinus node and of the atrial conductivity pathways were recorded by way of heart microcatheterization via the subclavian vein in 40 canine experiments and in 307 patients, using the obtained data for a more precise interpretation of the bundle of His electrogramme taken in the course of these examinations. The importance of the density of the spikes for their successful recording was studied, and it was found that the onset of the atrial A--wave preceeded that of the P-wave by 10-30 ms on ECG tracings recorded from the body surface. The atrial A--complex recorded with the aid of an intracardiac unipolar electrode from the right atrium was found to consist of a slow depolarization wave of the atria and of three spike potentials (A1, A2 and A3). The A2 spike coinsides with the peak of the P-wave in the II lead and reflects the moment of the impulse's arrival at the atrioventricular node along the Bachman and Wenkebach's tract, while the A3 spike coinsides with the termination of the P-wave in the II lead being dependent on the depolarization of the Torel's tract. The P--A interval should be measured between the sinus spike and the A2 spike, while the A--H interval--between the A2 spike and the H-potential.

Action Potentials↗
PubMed1998

Acute effects of radiofrequency ablation upon atrial conduction in proximity to the lesion site.

The electrophysiological effects of RF ablation upon the areas in proximity to the lesioned zones have not yet been well characterized. An experimental model is used to investigate atrial conduction in the boundaries of RF damaged zones. In 11 isolated and perfused rabbit hearts, endocardial atrial electrograms were recorded using an 80-lead multiple electrode positioned in the left atrium. Both before and after the RF application (5 W, 8 s, 1-mm diameter unipolar epicardial electrode) in the mid-portion of the free left atrial wall, measurements were made of conduction time from the pacing zone (posterior wall of the left atrium) to three points between 7.5 and 7.9 mm distal to the damaged zone. Conduction velocity and the direction of the activation propagation vector were determined in ten groups of four electrodes positioned around the damaged zone, and at the left atrial appendage. The mean diameter (+/- SEM) of the transmural lesions produced by RF ablation and defined by macroscopic examination was 4.2 +/- 0.2 mm. The conduction times to the three points distal to the lesion site were significantly prolonged as a result of RF ablation; 7.6 +/- 0.4, 7.4 +/- 0.5, and 6.9 +/- 1.0 ms (control); and 11.3 +/- 1.0 (P < or = 0.01), 11.1 +/- 1.3 (P < 0.01), 10.6 +/- 1.4 ms (P < 0.05) (post-RF). The differences between the conduction velocities determined in the areas surrounding the lesion, before and after RF application, failed to reach statistical significance: 86.2 +/- 6.5 cm/s (control) versus 75.5 +/- 5.7 cm/s (post-RF) (NS). After RF, significant variations were only observed in the direction of impulse propagation in the proximal-inferior quadrant adjacent to the lesion site, the difference being -61 degrees +/- 18 degrees (P < 0.02). In 2 of 4 experiments in which the lesion size was increased by a second RF application (5 W, 16 s), tachycardias with activation sequence around the lesion could be induced, with cycle lengths of 56 and 50 ms, respectively. In the atrial wall, the conduction times to the regions distal to the RF lesion are significantly prolonged. No significant changes are observed in conduction velocity in the areas in proximity to the lesion. Prolonged conduction to the areas distal to the ablation site is due to the lengthened pathway traveled by the impulses in reaching these areas. Tachycardias with activation patterns that suggest reentry around the RF damaged zone may be induced.

Animals↗
PubMed1983

Atrio-ventricular and ventriculo-atrial conduction times in patients undergoing pacemaker implant.

Pacemaker mediated reentrant tachycardias have been seen frequently during use of dual chamber sensing pacemakers and are dependent on the presence of intact retrograde (ventriculo-atrial) conduction. The status of a patient's retrograde (VA) conduction cannot be determined from the surface electrocardiogram. At the time of pacemaker implant the state of antegrade conduction should be determined at incremental atrial pacing rates, the exact timing measured from the intracardiac electrograms, i.e., from the intrinsic deflection of the intrinsic deflection of the ventricle. With this information obtained in 53 patients, it was possible to determine which patients could safely receive dual chamber sensing pacemaker devices, the appropriate pacemaker atrial refractory period setting to avoid pacemaker mediated tachycardias in those patients with intact retrograde conduction, and the optimal timing for programming the pacemaker's AV delay. Patients who have been studied in this manner and who were felt to be suitable for a dual chamber sensing device have not displayed pacemaker mediated reentrant tachycardias. Forty-seven percent of all patients who require pacemaker implant have VA 1:1 conduction; 67% of those with sinus node dysfunction and 14% of those with complete antegrade block have VA conduction at a mean interval of 235 +/- 50 ms (range 110-380 ms).

Atrioventricular Node↗
PubMed1994

Atrioventricular nodal reentrant tachycardia in patients with ventriculo-atrial conduction block.

OBJECTIVE: To demonstrate the reversibility of retrograde ventriculo-atrial block by isoproterenol in patients with atrioventricular nodal reentrant tachycardia (AVNRT). DESIGN: Three case reports and their electrophysiological features. PATIENTS: Three patients with documented or suspected paroxysmal supraventricular tachycardia. INTERVENTIONS: At routine electrophysiology study, no supraventricular tachycardia was inducible in the baseline state. Infusion of isoproterenol (1 to 5 micrograms/min) was given and stimulation procedures were repeated. RESULTS: At baseline, all three patients had discontinuous antegrade atrioventricular (AV) nodal conduction, but very poor (two patients) or absent (one patient) ventriculo atrial conduction prevented induction of AVNRT. During infusion of isoproterenol, retrograde conduction was enhanced so that 1:1 retrograde occurred to cycle lengths of 300, 340 and 260 ms. AVNRT was then inducible in all patients, reproducing their clinical symptoms. CONCLUSION: Absent or poor ventriculo-atrial conduction in patients with suspected AV node reentry does not preclude the development of tachycardia with sympathomimetic enhancement. Isoproterenol should be given to attempt reversal of retrograde block in these patients.

Adult↗
PubMedDate not supplied

Validation of inter-atrial conduction time measurement by means of echo-Doppler.

BACKGROUND: Little is known about the correlation between the inter-atrial conduction time (IACT) measured at the electrophysiology laboratory and the interval measured from the beginning of the electrocardiographic P wave to the initiation of the A wave in the mitral Doppler signal (P-A interval). HYPOTHESIS: IACT can be assessed by means of echo-Doppler. METHODS: We studied 21 patients who were referred to our arrhythmia clinic for evaluation of supraventricular tachycardia. During the electrophysiological study, the IACT was measured from the first rapid deflection of the A wave recorded with the high right atrial catheter to the A wave recorded with the coronary sinus catheter. An independent observer measured the P-A interval. Both the electrophysiological and echo-Doppler measurements were corrected for heart rate. RESULTS: P-A interval was slightly longer than IACT (83.36 +/- 23.91 vs 80.77 +/- 24.11 msec; p = 0.042), but a very good correlation was found between both measurements (r2 = 0.94). CONCLUSIONS: IACT can be non-invasively assessed by measuring the P-A interval.

Adult↗
PubMed1976

[Significance of spike potentials in the sinus nodes and atrial conduction system during interpretation of bundle-of-his electrography].

The article deals with the issues of the His bundle electrogram (HBE) analysis, using the spike potentials of the sinus node and the atrial conductive tracts for the interpretation of the HBE. The HBE and the atrium spike potentials have been recorded in 40 dogs and in 307 patients. According to our data the onset of the A-wave on the IcECG begins in some msec earlier than the onset of the P-wave on the standard ECG leads. The spike potentials of the sinus node have been recorded directly at the sinus node area, the onset of which begins in 20-40 msec earlier than the onset of the P-wave. By our data the atrial A-wave recorded from the right atrium on the IcECG consists of the slow wave showing summary effect of the atrium depolarization and the three spikes (A1, A2, A3). They are recorded at the beginning (A1) middle (A2) and the end (A3) of the P-wave and reflect the quick impulse spread through the atrium conductive tracts. The moment of the impulse coming to the AV nodes is reflected by the atrial spike A2. The time of the impulse spread from the sinus node to the AV node shows exactly the interval from the onset of the spike potential of the sinus node till the spike A2. The interval from the spike A2 to the H-potential (A2-H) shows the impulse spread time through the AV node. The recording of the HBE and the atrium spike potentials was performed by means of the microcatheter of own construction (with the unipolar electrodes, external diameter of which does not exceed 1 mm) after our method of the heart microcatheterization through the subclavian vein.

Action Potentials↗
PubMed2004

Unidirectional atrio-atrial conduction after surgical isolation of the posterior part of the left atrium and pulmonary veins for atrial fibrillation: simple postsurgical procedure electrophysiological evaluation.

A 66-year-old woman underwent mitral valve replacement and surgical isolation of the posterior part of the left atrium for persistent AF. During sinus rhythm an isolated atrial rhythm was recorded from the isolated posterior left atrium using an esophageal electrode catheter. After the intravenous administration of adenosine triphosphate sinus rhythm was suppressed and 1:1 conduction from the posterior left atrium to the rest of the atrium was recorded. Unidirectional atrio-atrial conduction was revealed by a simple electrophysiological evaluation

Adenosine Triphosphate↗
PubMed2001

Effect of ethnicity and hypertension on atrial conduction: evaluation with high-resolution P-wave signal averaging.

BACKGROUND: Measurements by P-wave signal-averaged electrocardiogram (P-SAECG) of P-wave duration and P-wave voltage integral are higher in patients with atrial fibrillation (AF) than in those with sinus rhythm. Hypertension is perhaps the most common cardiovascular antecedent cause of AF, and particularly a disproportionate cause of morbidity and mortality among blacks. The purpose of this study was to examine the effect of hypertension and ethnicity on P-SAECG parameters in patients without AF. HYPOTHESIS: It was hypothesized that P-SAECG parameters can identify hypertensives, and are disproportionately higher in hypertensive blacks. METHODS: In all, 234 normotensives and 84 hypertensives underwent P-SAECG analysis. In an ancillary study group of 34 hypertensive black men, the relationship between severity of hypertension and measured parameters of P-SAECG was evaluated. RESULTS: Mean filtered P-wave duration and total P-wave voltage integral for normotensives of both ethnic groups were similar. Hypertensive blacks had greater increase in P-wave duration (138 +/- 16 vs. 132 +/- 12ms;p < 0.01, N42:42) and total P-wave voltage integral (922 +/- 285 vs. 764 +/- 198 microV-ms; p < 0.001) than white hypertensives. Filtered P-wave duration and total P-wave voltage integral increased with severity of hypertension. CONCLUSIONS: Patients at very early stages of hypertension have demonstrable evidence of prolonged atrial conduction by P-SAECG and, thus, cardiac electrical remodeling. P-wave duration and total P-wave voltage integral increase with severity of hypertension. Hypertensive blacks manifest a greater increase in P-SAECG parameters than whites. This may portend an increased cardiovascular risk for black patients with hypertension.

Adolescent↗