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At least 55 records · Page 3Linked to original sources
PubMed2001

Intra-atrial conduction block along the mitral valve annulus during accessory pathway ablation: evidence for a left atrial "isthmus".

INTRODUCTION: We observed a change in the atrial activation sequence during radiofrequency (RF) energy application in patients undergoing left accessory pathway (AP) ablation. This occurred without damage to the AP and in the absence of a second AP or alternative arrhythmia mechanism. We hypothesized that block in a left atrial "isthmus" of tissue between the mitral annulus and a left inferior pulmonary vein was responsible for these findings. METHODS AND RESULTS: Electrophysiologic studies of 159 patients who underwent RF ablation of a left free-wall AP from 1995 to 1999 were reviewed. All studies with intra-atrial conduction block resulting from RF energy delivery were identified. Fluoroscopic catheter positions were reviewed. Intra-atrial conduction block was observed following RF delivery in 11 cases (6.9%). This was evidenced by a sudden change in retrograde left atrial activation sequence despite persistent and unaffected pathway conduction. In six patients, reversal of eccentric atrial excitation during orthodromic reciprocating tachycardia falsely suggested the presence of a second (septal) AP. A multipolar coronary sinus catheter in two patients directly demonstrated conduction block along the mitral annulus during tachycardia. CONCLUSION: An isthmus of conductive tissue is present in the low lateral left atrium of some individuals. Awareness of this structure may avoid misinterpretation of the electrogram during left AP ablation and may be useful in future therapies of atypical atrial flutter and fibrillation.

Arrhythmias, Cardiac↗
PubMed2000

Detection of inter-atrial conduction defects with unfiltered signal-averaged P-wave ECG in patients with lone atrial fibrillation.

AIMS: To demonstrate a possible inter-atrial conduction delay in patients with lone paroxysmal atrial fibrillation (PAF) using 'unfiltered' signal-averaged P-wave ECG (PSAECG) and compare these results with those obtained with conventional filter settings. METHODS AND RESULTS: Twenty one patients with lone PAF and 20 healthy volunteers (control group) were enrolled in the study. An orthogonal lead surface ECG was high-pass filtered at 0.8 Hz, averaged with template matching, and combined into a spatial magnitude ('unfiltered' technique). Results were compared with conventionally filtered (40-300 Hz) PSAECG. The filtered technique revealed no differences in P-wave duration between the two groups (121 +/- 12 vs 128 +/- 15 ms, control and PAF groups respectively, ns). Double-peaked P-wave spatial magnitudes (interpeak distance >30 ms) were revealed in 11 of 21 PAF patients but only in two of 18 controls (P<0.01). The nadir in the spatial magnitude was located significantly later in the PAF group (114 +/- 13 vs 103 +/- 9 ms, P<0.01). CONCLUSION: 'Unfiltered' PSAECG revealed significant differences in orthogonal P-wave morphology in patients with lone PAF, indicating the possibility of an inter-atrial conduction delay, while conventional P-wave duration analysis failed to discriminate between the two groups.

Adult↗
PubMed2006

Human atrial conduction and arrhythmogenesis correlates with conformational exposure of specific epitopes on the connexin40 carboxyl tail.

BACKGROUND: Gap junction expression is considered to influence myocardial conduction and arrhythmogenesis, but studies in patients with atrial fibrillation (AF) have reported inconsistent results. We used human atrial conduction and arrhythmogenicity to provide clinical parameters with which to correlate quantification of connexin40 (Cx40) by different techniques to address the hypothesis that antibody-epitope binding properties may influence quantification methods. METHODS AND RESULTS: Atrial conduction properties were studied in patients undergoing coronary artery bypass grafting (N = 27) using multi-electrode array mapping. Patients were defined as having a vulnerable atrial substrate if pacing-induced AF lasted for more than 30 s. Using antibodies targeted at two different epitopes of the cytoplasmic carboxyl tail, Cx40 signal was quantified by immunoconfocal microscopy in biopsies taken from the mapped atria. Only patients with a vulnerable substrate subsequently developed post-operative AF (P < 0.02). Immunoconfocal Cx40 signal measured by one antibody, designated S15C(R85), was lower in patients with sustained induced AF (0.013 +/- 0.009 microm(2)/microm(2) vs. 0.024 +/- 0.010 microm(2)/microm(2), P = 0.005) and was negatively correlated with atrial conduction velocity during sinus rhythm (P < 0.05). However, these relationships did not exist when the Cx40 signal was measured using a different antibody (Y21Y(R968)). Further studies suggested that quantification technique was reproducible against the same epitope (P < 0.001) but not against different epitopes indicating variable exposure of Cx40 epitopes. CONCLUSIONS: Quantification of Cx40 by immunoconfocal microscopy appears to be epitope dependent and evidence of epitope masking raises the possibility of more than one conformational form of the Cx40 carboxyl tail, suggesting functionally important conformations of the protein.

Aged↗
PubMed2003

Sinus node dysfunction and impairment of global atrial conduction time after high rate atrial and ventricular pacing in dogs.

It has been shown in animals and humans that AF shortens the atrial refractory period and impairs its rate adaptation. The aim of the study was to evaluate the effects of high rate pacing on sinus node function and intraatrial conduction. Eight dogs were subjected to rapid atrial pacing (AP) at a rate of 400 beats/min for 16 days. After a complete recovery of left ventricular function, they underwent rapid ventricular pacing (VP) at 240 beats/min of equal duration. Sinus node recovery time (SNRT) was measured after pacing at 150, 160, and 170 beats/min. P wave duration was measured on a surface ECG recorded at a paper speed of 200 mm/s. Measurements were performed at baseline, immediately after AP or VP, and four weeks after termination of AP or VP. SNRT immediately after AP and VP was significantly prolonged at all three pacing rates (P < 0.03). P wave duration increased significantly after either type of pacing (AP: 74.3 +/- 6.4 ms, VP: 70.0 +/- 3.8 ms) compared with baseline values (60.6 +/- 6.2 ms, P < 0.05). Rapid AP and VP induces sinus node dysfunction and prolongs intraatrial conduction time. The effects of sustained AP and VP on sinus node function and atrial myocardium returned toward control values 4 weeks after cessation of pacing. The authors hypothesize that reversible electrical remodeling occurs both in the sinus node and in the atrial myocardium.

Animals↗
PubMed2002

Relative expression of immunolocalized connexins 40 and 43 correlates with human atrial conduction properties.

OBJECTIVES: The aim of this study was to determine the relationship between immunolocalized gap-junctional proteins and human atrial conduction. BACKGROUND: As a determinant of intercellular conductance, gap-junctional coupling is considered to influence myocardial conduction velocity. This study tested the hypothesis that the quantity of immunodetectable atrial gap-junctional proteins, connexin40 (Cx40) and connexin43 (Cx43), are related to atrial conduction velocity in humans. METHODS: Epicardial mapping was performed on 16 patients undergoing cardiac surgery using an array of 56 unipolar electrodes. The conduction velocity was measured over the right atrial free wall during sinus rhythm and at a paced cycle length 500 ms. A biopsy from this region was excised for quantitative confocal immunodetection of Cx40 and Cx43. RESULTS: There was no correlation between conduction velocity and Cx43 signal or total connexin signal (Cx40 + Cx43). Connexin40 signal was inversely correlated with conduction velocity (p = 0.036). However, the relative quantity of connexin immunolabeling (expressed as Cx40/[Cx40+Cx43] or the inverse equivalent Cx43/[Cx40+Cx43]) was strongly associated with conduction velocity during sinus rhythm, such that, as the proportion of Cx40 signal increased (and that for Cx43 decreased), the conduction velocity decreased (p < 0.005, r = -0.66). Furthermore, with paced atrial activation at 500 ms cycle length, the relative quantity of connexin labeling (Cx40/[Cx40+Cx43]) correlated with the rate-related change in atrial conduction velocity (p < 0.02, r = 0.59). CONCLUSIONS: In human right atrium, conduction velocity is inversely related to immunodetectable Cx40 levels. The relative level of connexins 40 and 43 signal is strongly associated with atrial conduction properties, suggesting that interactions between the two connexins may result in novel coupling properties.

Adult↗
PubMed2003

Atrial septal versus atrial appendage pacing: feasibility and effects on atrial conduction, interatrial synchronization, and atrioventricular sequence.

Atrial septal (Se-P) and atrial appendage pacing (Ap-P) were compared in a randomized, controlled study to assess the feasibility, the reliability, and the effects of Se-P on atrial conduction, interatrial synchronization, and the AV sequence. The main baseline characteristics of the patients were comparable in both groups. There was no difference in feasibility or reliability between the two techniques. Compared to Ap-P (n = 28), Se-P (n = 28) decreased the P wave duration, left atrial electromechanical delay (LAEMD), and interatrial interval (-1.6% vs +28%, P < 0.001; -3% vs +30%, P < 0.001; -130% vs +78%, P < 0.001); it induced a smaller increase of the right AEMD, a slight reversal of the timing of the atrial systoles and a shortening of the PR interval (-13% vs +25%, P < 0.001) and of the interval separating atrial systoles from ventricular activation. Finally, the shortening of the PR interval was smaller during high Se-P versus low Se-P. Se-P avoids the undesirable prolongation of the atrial, interatrial, and AV conductions observed during Ap-P. In addition, Se-P creates a slight reversal of the timing of the atrial systoles and induces a shortening of PR interval, the extent of which could depend on the height of the pacing site on the septum.

Aged↗
PubMed1985

Anterograde sinuatrial conduction evaluated by sinus node electrogram in atropine blocked retrograde atrial conduction.

Two cases are described where atropine induced the disappearance of reset zone as response to premature atrial stimulation for blocked retrograde atrial conduction. Because of this, sinuatrial conduction time could not be estimated. The sinus node electrogram allowed the direct measurement of sinuatrial conduction and showed a facilitated anterograde conduction through the perinodal fibers after administration of the drug.

Atropine↗
PubMedDate not supplied

Experimental validation of sino-atrial conduction time using sinus node potential recording, right and left atrial continuous pacing method.

In an experimental study indirect sino-atrial conduction time (SACT) was measured, using continuous pacing method from right and left atrial sites, and compared with direct SACT obtained from sinus node potential recording, all the determination being done before and after autonomic blockade. The distance between the two sites of stimulation may be taken into account as a correction factor for SACT determination. The SACT obtained with sinus node potential technique is the same as the indirect SACT after autonomic blockade. These findings are valuable for SACT determination with transesophageal pacing method. Left atrial pacing, thus transesophageal pacing, is a valuable method in estimating the SACT, but a time correction and autonomic blockade is required in order to obtain a real value, eliminating the extrinsic influences.

Animals↗
PubMed2000

The importance of right atrial pacing electrode position and pacing configuration for intra-atrial and inter-atrial conduction times.

Pace prevention of atrial tachyarrhythmias is based in part on the reduction of intra-atrial (IAA) and/or inter-atrial (IEA) conduction. We previously introduced a novel pacing mode using floating atrial ring electrodes on a VDD-lead (BIdirectional MO nophasic impulSe: BIMOS). The effects of BIMOS pacing on IAA and IEA conduction times has not been studied. In nine Merino sheep electrode catheters were placed at the His-Bundle (HBE), high right atrium (HRA), coronary sinus ostium (Cs-Os), and left lateral atrium (LLA). A VDD-lead was introduced with floating electrodes in the high and mid right atrium (Floating). IAA (S/P-HRA, S/P-Cs-Os, S/P-HBE, S/P-Floating), IEA conduction times (S/P-LLA), and P-wave duration (PD) were measured during sinus rhythm (S), during bipolar cathodal pacing (P) in the HRA, in the Cs-Os position, as well as during BIMOS floating pacing. The mean PD during S was significantly shorter than during HRA- (66. 6+/-12.8ms; vs. 116.2+/-11.1ms; p<0.05) and Cs-Os-P (66.6+/-12.8ms vs. 94.4+/-9.0ms; p<0.05). In comparison to HRA-P, BIMOS configuration lead to a significant reduction of the P-wave duration (116.2+/-11.1ms vs. 85. 4+/-8.8ms; p<0.05). During BIMOS pacing, the global atrial conduction time was significantly shorter than during pacing in the HRA and Cs-Os position. The results of this study demonstrate a clear reduction of IAA and IEA conduction times using BIMOS configurations compared to conventional HRA-P. Furthermore, BIMOS pacing produced a more homogeneous atrial activation when compared with conventional HRA- and Cs-Os-P.

Animals↗
PubMed2004

Novel use of postpacing interval mapping to guide radiofrequency ablation of focal atrial tachycardia with long intra-atrial conduction time.

If the intra-atrial conduction time of a focal tachycardia is prolonged and exceeds the tachycardia cycle length, isochronal electroanatomical maps may be confusing by not showing the classical centrifugal pattern of focal activation. In addressing the hypothesis that by mapping post pacing intervals (PPI), the shortest PPI (ideally identical to tachycardia cycle length) would clearly display the site of origin of a focal tachycardia; this technique was used successfully to identify the origin and ablate the atrial tachycardia of a patient with previously corrected Tetralogy of Fallot.

Adult↗
PubMed1984

Atrial conduction: effects of extrastimuli with and without atrial dysrhythmias.

The effects of cycle length and stimulation site on intraatrial conduction and refractoriness were evaluated in patients with and without atrial flutter (AFI) or fibrillation (AF) using the extrastimulus technique. Nineteen patients with spontaneous sustained AFI or AF were compared with 19 control patients. Programmed stimulation was performed at the right atrium and coronary sinus at drive cycle lengths of 600 and 450 ms. The atrial effective refractory period was similar in the patients with atrial dysrhythmias and the control group. The right atrial effective refractory period at a drive cycle length of 600 ms was significantly shorter in patients with AF (211 ms) than in patients with AFI (235 ms, p = 0.05). The conduction time of late (coupling intervals more than 50% of the drive cycle length) premature impulses was similar in the patients with atrial dysrhythmias and the control group. However, early extrastimuli (coupling intervals less than 50% of the drive cycle length) at a drive cycle length of 600 ms produced significantly more intraatrial conduction delay in the patients with atrial dysrhythmias than in the control patients. At a drive cycle length of 450 ms, similar delays in intraatrial conduction occurred in the patients with and without atrial dysrhythmias because of an increase in the maximal-observed intraatrial conduction delay in the control patients. This study shows that delay in conduction of early premature atrial stimuli at a drive cycle length of 600 ms is a marker of patients with spontaneous AFI and AF.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed2003

Left atrial conduction along the coronary sinus during ectopic atrial tachycardia and atrial fibrillation: a study using correlation function analysis.

INTRODUCTION: Correlation function analysis was applied to endocardial electrograms to investigate conduction patterns along the coronary sinus (CS) during sinus rhythm (SR) and atrial tachycardias. METHODS AND RESULTS: Eighteen recordings were obtained from 14 patients with supraventricular tachycardias. Five atrial fibrillation (AF) recordings were compared to 10 SR recordings and 3 ectopic atrial tachycardia (EAT) recordings. The maximum correlation coefficient was used to assess similarity between signals, i.e., if they originate from the same wavefront. The cumulative time delay, calculated as pairwise summation of interelectrode time delays, was used as an indicator of activation sequence along the CS. Method validation using SR showed right-to-left conduction with high correlations in 8 of 10 recordings indicating one single wavefront. EAT recordings showed consistent left-to-right conduction with left atrial foci and right-to-left with right atrial focus and lower correlations than SR. All 5 AF recordings showed predominantly left-to-right conduction direction, also with correlations lower than SR. CONCLUSION: (1) Correlation function analysis can be used to assess agreement between signals and direction of activation spread. (2) Due to the position of CS, the results can be used to derive mechanisms of interatrial conduction. (3) Consistency in electrical activity propagation along CS is common in AF.

Algorithms↗
PubMed1991

Retrograde (ventriculo-atrial) conduction, premature beats, pseudotricuspid regurgitation, systolic atrial sounds and pacemaker sounds observed together in two patients with ventricular pacing.

Two patients were found to have retrograde atrioventricular conduction with premature beats during permanent ventricular pacing. In both patients the auscultatory phenomena had been heard and recorded that had been described as independent signs, but all together in the same patient had not been reported before. In one of the patients pseudotricuspid regurgitation was observed with Doppler echocardiography and the other was suspected having the same. It seems that patients with these symptoms deserve high preventive care and attention.

Arrhythmias, Cardiac↗
PubMed1991

[Pathological modifications of the P wave due to probable primary changes in intra-atrial conduction].

Two cases of variable changes in ECG P oscillation not due, as is usually the case, to familiar cardiac or respiratory conditions suggested a review of the literature on the subject. It is concluded that these anomalies are the result of changes in the intra-atrial conduction of the stimulus through preferential ways or to aberrant atrial conduction. These are situations of no little practical interest because they may be precursors of major rhythm disturbances such as atrial flutter or atrial fibrillation.

Electrocardiography↗
PubMed1986

Noninvasive assessment of ventriculo-atrial conduction and early experience with the tachycardia termination algorithm in pacemaker-mediated tachycardia.

Since the advent of physiologic dual chamber pacing systems, pacemaker-mediated tachycardia (PMT) has occurred and the need for invasive measurement of ventriculo-atrial conduction (VAC) has arisen. The variability in VAC and the potential for PMT often make it necessary to assess for the presence or absence of VAC at different points in time. We noninvasively evaluated 20 pacemaker patients for the presence or absence of VAC. We compared ventriculo-atrial conduction time (VACT) obtained with the atrial sense event maker with that obtained from Holter monitoring and invasive methods. The incidence of spontaneous (S) and induced (I) PMT and the efficacy of the tachycardia termination algorithm (TTA) was assessed. Fourteen of 20 had VAC with invasive or noninvasive methods. Twelve of 19 had PMT (63%); three were sustained (greater than 15 beats). We conclude that VACT assessed with the atrial sense event marker (ASEM) yielded a high correlation when compared to the Holter monitor data obtained utilizing our methodology. PMT is commonly a nonsustained (less than 15 beats) event, and the TTA is effective in sustained PMT. Myopotential sensing, atrial premature contractions and loss of atrial capture are common mechanisms in the initiation of PMT.

Adult↗
PubMed1977

Human atrial conduction with reference to heart rate and refractory periods.

Atrial conduction time (ACT) between a stimulating pacemaker electrode and an "impulse-detecting" monophasic action potential (MAP) electrode has been determined in 20 healthy males. A small increase in ACT was found with increasing paced heart rates. Using the extra stimulus technique, ACT was found to increase when the early ectopics approached the atrial effective refractory period (AERP). The degree of ACT prolongation was similar at long and short basic ACTs, indicating that the slowing of impulse propagation probably occurred near the simulating electrode and presumably within 1/2-1 cm from that electrode. The increase in ACT close to the AERP was of importance when determining the atrioventricular refractory period. In three recordings a supernormal phase of conduction was found. The small errors of the MAP recordings in detecting the time of excitation make the method sensitive enough to detect small differences in ACT.

Action Potentials↗
PubMed1993

[Effect of electro-acupuncture at neiguan P6 on sino-atrial conduction in patients without sick sinus syndrome].

The effects of electro-acupuncture (EA) at Neiguan P6 served as a main point and Jianshi P5 as an adjunct point on sino-atrial conduction were studied in 10 patients with normal sinus nodal function. The results were as follows: During EA and in period of intrinsic heart rate (IHR0) the sinoatrial conduction times (SACT) from sinus node electrogram were significantly shortened than that in control, (P < 0.01 and P < 0.001, respectively). But the SACT could not be further shortened by stimulating the acupoints during IHR0 (P < 0.05). It is suggested that EA at Neiguan P6 as a main point could improve sino-atrial conductivity in most patients with normal sinus node function, which seems to be mediated by autonomic nerve system. The normal value of SACT after autonomic nerve blockade needs to be established.

Acupuncture Points↗