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At least 505 records · Page 28Linked to original sources
PubMed1995

Effects of disopyramide on the atrial fibrillation threshold in the human atrium.

The effects of disopyramide on the atrial fibrillation threshold (AFT) in the human atrium were investigated. To evaluate atrial vulnerability, the following electrophysiologic parameters were measured before and after the administration of disopyramide (2 mg/kg) in 12 patients with paroxysmal atrial fibrillation: The right atrial effective refractory period (ERP) and percentage maximum atrial fragmentation (%MAF) were measured by atrial premature stimulation based on a cycle length of 500 ms. The inter-atrial conduction time (ACT) was measured by burst pacing (120/min) for 30 s. AFT was measured by applying a high-frequency (50 Hz) stimulation for 1 s given at the right atrial appendage. AFT was defined as the lowest intensity of electrical current that could induce atrial fibrillation lasting for more than 30 s. Disopyramide significantly reduced %MAF, and prolonged ERP and ACT. AFT was measured in all patients and the mean AFT was 3.1 +/- 1.7 mA. After the administration of disopyramide, AFT significantly increased to 6.1 +/- 3.6 mA. There was a positive correlation between ERP and AFT, and a negative correlation between %MAF and AFT. No correlation was detected between ACT and AFT. In conclusion, disopyramide increased AFT in the human atrium.

Adult↗
PubMed1992

Atrial vulnerability.

The electrophysiologic substrates of atrial flutter and fibrillation (AFF) have been studied in patients with paroxysmal arrhythmias. Atrial repetitive responses to extrastimuli are a nonspecific response, even though they can precipitate AFF. AFF inducibility is rather sensitive, but not very specific, in separating patients from controls. There is no established protocol to explore vulnerability in this fashion. Atrial refractoriness is abnormal in some patients. Some authors have found a tendency toward short effective refractory periods (AERP) and others have found a poor adaptation of AERP to decreases in cycle length. Unfortunately, these abnormalities are neither sensitive nor specific enough. Atrial conduction may be abnormal basally, but subtler abnormalities are shown by premature stimulation. Early extrastimuli are conducted with increased conduction delays in patients with paroxysmal AFF in relation to controls. Again, there is not enough sensitivity and specificity in the findings to make them of diagnostic value. Electrophysiologic abnormalities are detectable in patients with AFF, but larger studies, including reproducibility and the effect of drugs on the abnormal parameters, will be necessary to develop clinical applications.

Atrial Fibrillation↗
PubMed2003

Effects of P-wave dispersion on atrial fibrillation in patients with acute anterior wall myocardial infarction.

BACKGROUND: P-wave dispersion (P dispersion), defined as the difference between the maximum and the minimum P-wave duration (P minimum), and maximum P-wave duration (P maximum) have been used to evaluate the discontinuous propagation of sinus impulse and the prolongation of atrial conduction time respectively. The aim of this study was to investigate whether early assessment of P dispersion predicts paroxysmal atrial fibrillation (AF) in patients with acute anterior wall myocardial infarction (MI). METHODS: We prospectively evaluated 147 consecutive patients (45 women, 102 men; aged 55 +/- 9 years) with a first acute anterior wall MI. All patients were evaluated by echocardiography to measure the left atrial diameter and left ventricular ejection fraction (LVEF). Electrocardiography was recorded from all patients on admission and every day during hospitalization. RESULTS: AF occurred in 25 patients. In 122 patients, AF did not occur. P maximum was found to be significantly higher in patients with AF than in patients without AF (115 +/- 17.3 ms vs 101 +/- 14.7 ms, P = 0.001). P dispersion also was significantly higher in patients with AF than in patients without AF (50 +/- 12.5 ms vs 43 +/- 10.1 ms, P = 0.01). There was no significant difference between the two groups in P minimum (64 +/- 12.5 ms vs 59 +/- 11.7 ms, P = 0.057). The echocardiographically left atrial diameters were not significantly higher in the patients with AF than those without (25 +/- 3.38 mm and 23 +/- 3.36 mm, respectively, P = 0.76). LVEF was found to be significantly different in the patients who developed AF and in those who did not (37.96 +/- 6.18% vs 47.70 +/- 6.01%, P = 0.0001). CONCLUSIONS: Although P maximum and P dispersion are significant predictive factors of AF in patients with acute anterior wall MI in the univariate analysis, on the basis of multivariate analysis, only age and LVEF were independent predictive parameters for AF.

Age Factors↗
PubMed1984

Clinical electrophysiological effects of chronic administration of verapamil: the phenomenon of overdrive excitation of junctional pacemaker.

The electrophysiological effects of chronic administration of verapamil were studied in 10 patients with normal sinus node function, who received 160 mg of the drug every eight hours for at least two weeks. Uncorrected and corrected sinus node recovery time, sino-atrial conduction time, effective and functional refractory periods were normal in each case. In three patients, at the cessation of atrial pacing, an overdrive excitation of junctional pacemaker with short lasting A-V dissociation was observed.

Electric Stimulation↗
PubMed1988

Atrial natriuretic factor-SV40 T antigen transgenes produce tumors and cardiac arrhythmias in mice.

Transgenic mice that carry fusions between the transcriptional regulatory sequences of atrial natriuretic factor (a hormone intimately involved in the regulation of blood pressure) and those encoding SV40 T antigen (an oncoprotein) were generated. Although both atria express the fusion gene, the pathological response to T antigen is asymmetrical. The right atrium undergoes a several hundredfold increase in mass while the left atrium remains relatively normal in size. Hyperplasia is accompanied by a progressive increase in both the frequency and severity of abnormalities in the atrial conduction system, which ultimately result in death.

Animals↗
PubMed1991

Simulated myocardial infarction and slow atrial flutter due to cerebral embolism from a free left atrial thrombus.

The case of a 38-year-old female who suffered a cerebral embolism from a free left atrial thrombus is reported. The clinical picture, including serum enzyme elevations, was consistent with a nontransmural myocardial infarction. Atrial flutter exhibiting very slow (162/min) and tall waves was transiently recorded indicating development of an intra-atrial conduction disturbance.

Adult↗
PubMed2005

Atrial septal pacing to resynchronize atrial contraction and improve atrial transport function.

OBJECTIVES: Atrial septal pacing via a trans-septal breakthrough site within the right atrial septum can shorten global atrial activation time, resulting in significant reduction of recurrence of atrial fibrillation events. This study examined whether this pacing method will lead to resynchronization of atrial contraction and its benefit on hemodynamic function can be maintained for 24 months. METHODS: Thirty patients with atrial fibrillation and delayed atrial conduction were enrolled (17 males, 13 females, mean age 73 +/- 7 years). Trans-septal breakthrough site within the right atrial septum was identified through pacing from the dorsal left atrium. Continuous atrial septal pacing at the trans-septal breakthrough site was performed for 24 months. Time difference (TD) between right and left atrial contractions was measured during atrial septal pacing and sinus rhythm by pulse Doppler echocardiography of the trans-tricuspid (P-At) and mitral (P-Am) blood flows (TD = P-Am - P-At). RESULTS: The atrial lead was screwed near the fossa ovalis in 29 of 30 patients. Atrial septal pacing yielded significantly shorter P wave duration (101.9 +/- 10.4 vs 139.6 +/- 14.7 msec, p < 0.001), leading to significant reduction of TD in atrial contraction (-8.8 +/- 10.0 vs 29.8 +/- 13.6 msec, p < 0.001)as compared to sinus rhythm. Both shorter P wave duration and reduced TD during atrial septal pacing remained statistically significant during the follow-up period as compared to sinus rhythm. Both left atrial diameter and A to E ratio of filling waves at mitral valve were significantly decreased at 12 months and remained decreased at 24 months. CONCLUSIONS: Atrial septal pacing at the trans-septal breakthrough site can resynchronize atrial contraction and results in improved hemodynamic effects during 24 months of follow-up.

Aged↗
PubMed2005

Anxiety and P wave dispersion in a healthy young population.

BACKGROUND: P wave dispersion (P(d)), defined as the difference between the maximum (P(max)) and the minimum P wave duration (P(min)), and P(max) are electrocardiographic (ECG) markers that have been used to evaluate the discontinuous propagation of sinus impulses and the prolongation of atrial conduction time. P(d) in normal subjects has been reported to be influenced by the autonomic tone, which induces changes in atrial size and the velocity of impulse propagation. However, the association between P(d) and anxiety has not been studied in normal subjects. METHODS AND RESULTS: P(max), P(min) and P(d) were measured in 726 physically and mentally healthy young male volunteers, aged 21.23 +/- 1.25 years (range 20-26). The Spielberger State-Trait Anxiety Inventory (STAI) was scored concomitantly. Blinded intra- and interobserver reproducibility of the P wave duration and P(d) measurement were evaluated, and comparison revealed a Pearson correlation coefficient of 0.87 and 0.89 for the P wave duration, and 0.93 and 0.90 for P(d), respectively (p < 0.001). P(max) and P(d) were significantly correlated with the state anxiety (STAI-1) subscale (r = 0.662, p < 0.001, and r = 0.540, p < 0.001, respectively) and the trait anxiety (STAI-2) subscale (r = 0.583, p < 0.001, and r = 0.479, p < 0.001, respectively). P(min) did not show any significant correlation with anxiety. Across 3 variables included in a multiple linear regression analysis, STAI-1 and STAI-2 were the significant independent determinants of P(max) and P(d). Beta coefficients indicated that the contribution of STAI-1 to P(max) (66.3 and 33.7%) and P(d) (65 and 35%) was much greater than that of STAI-2. CONCLUSIONS: STAI-1 and STAI-2 are associated with an increase in P(max) and P(d). The association of P(d) resulted from an augmentation of P(max). This is the first study to show the relation between P(max), P(d) and anxiety.

Adult↗
PubMed1990

Mechanism of double ventricular response to a single atrial extrastimulus in patients with Wolff-Parkinson-White syndrome.

The purpose of this study is to elucidate electrophysiological determinants of double ventricular response (DVR) to a single atrial extrastimulus in Wolff-Parkinson-White (WPW) syndrome. DVR was observed in 5 (3.4%) out of 146 consecutive patients with WPW syndrome. The site of accessory pathway was located in left lateral free wall in four patients and posterior septum in one. DVR was induced by extrastimulus from coronary sinus in four patients with left-sided accessory pathway, and from both coronary sinus and high right atrium in a patient with septal accessory pathway. However, it was not possible to induce DVR from high right atrium in patients with left-sided accessory pathway, because 50 to 80 ms are needed for intra-atrial conduction from high right atrium to coronary sinus. Critical prolongation of normal AV conduction allowing DVR was seen in the slow pathway of AV node in four patients. In the remaining patients requisite conduction delay occurred in both AV node and His-Purkinje system. Single right ventricular extrastimulus could easily elicit orthodromic AV reciprocating tachycardia or echo beat in four out of five patients and incremental ventricular stimulation induced it in the remaining patient, indicating the presence of retrograde block in the normal AV pathway. As requisites of DVR to a single atrial extrastimulus in WPW syndrome: (1) slow antegrade conduction and retrograde block in the normal AV pathway; and (2) stimulation site in the vicinity of accessory pathway, are needed.

Adolescent↗
PubMed1995

Role of right atrial endocardial structures as barriers to conduction during human type I atrial flutter. Activation and entrainment mapping guided by intracardiac echocardiography.

BACKGROUND: The importance of barriers in atrial flutter has been demonstrated in animals. We used activation and entrainment mapping, guided by intracardiac echocardiography (ICE), to determine whether the crista terminalis (CT) and eustachian ridge (ER) are barriers to conduction during typical atrial flutter in humans. METHODS AND RESULTS: In eight patients, ICE was used to guide the placement of 20-pole and octapolar catheters along the CT and interatrial septum and a roving catheter to nine sites: just posterior (1) and anterior (2) to the CT along the lateral right atrium, at the fossa ovalis (3), and just posterior and anterior to the ER at the low posterolateral (4 and 5), low posterior (6 and 7), and low posteromedial (8 and 9) right atrium. Entrainment was performed, and each site was considered within the flutter circuit if the postpacing interval-flutter cycle length (PPI-FCL) and the stimulus time-activation time (stim time-act time) were < 10 msec. Split potentials were recorded along the CT with components activated in a low-to-high pattern and a high-to-low pattern. Conduction times, as percentage of FCL, were significantly different at sites on either side of the CT and ER: site 1 (33 +/- 13%) and site 2 (43 +/- 12%) (P = .02), site 4 (48 +/- 24%) and site 5 (75 +/- 8.9%) (P = .02), and site 6 (22 +/- 10%) and site 7 (82 +/- 5.3%) (P = .0009). During entrainment, no surface fusion was observed at sites 5, 7, or 9. The PPI-FCL and stim time-act time were not significantly different than 0 at sites 2, 7, 5, or 9, indicating that they were within the flutter circuit, whereas sites 1, 3, 4, and 6 were not. CONCLUSIONS: ICE enabled the correlation of functional electrophysiological properties with specific anatomic landmarks, identifying the CT and ER as barriers to conduction during human atrial flutter.

Aged↗
PubMed1976

[Significance of spontaneous reduction of long term auricular fibrillation. Apropos of a case followed by subtotal auricular paralysis].

The authors report the case of a female patient with mitro-aortic valve disease, whose atrial fibrillation had been recorded over a period of 13 years. There was then a conversion to sinus rhythm, followed by the appearance of a junctional rhythm with retrograde atrial conduction. Intracavitory investigation revealed that the electrical activity of the right atrium could be recorded only from a limited area, and that atrial stimulation was effective only over that area. This subtotal atrial paralysis suggests that the spontaneous conversion from atrial fibrillation was a sign of deterioration in the condition rather than of a "paradoxical improvement".

Atrial Fibrillation↗
PubMed1999

Pharmacologic cardioversion of chronic atrial fibrillation in the goat by class IA, IC, and III drugs: a comparison between hydroquinidine, cibenzoline, flecainide, and d-sotalol.

INTRODUCTION: Recently, we reported that repetitive induction of atrial fibrillation (AF) in the goat causes electrical remodeling of the atria leading to the development of sustained AF. The aim of the present study was to compare Class IA, IC, and III drugs in their ability to cardiovert chronic AF in remodeled atria. METHODS AND RESULTS: In 16 goats with sustained AF, hydroquinidine (HQ), cibenzoline (Ci), flecainide (FI), and d-sotalol (dS) were infused. HQ, Ci, Fl, and dS restored sinus rhythm (SR) in 83%, 91%, 67%, and 92% of the cases, while adverse drug effects occurred in 17%, 36%, 56%, and 8%. Prior to restoration of SR, AF cycle length prolonged by 68%, 103%, 53%, and 20%, respectively. The QRS width increased by 14%, 64%, and 58% (HQ, Ci, and Fl), and remained unchanged by administration of dS. RR intervals were slightly prolonged by HQ, Ci, and Fl, and markedly prolonged by dS (48%). The QT interval was moderately prolonged by HQ, Ci, and Fl, and considerably by dS (34%). QTc was only slightly prolonged by each of the drugs. Directly after cardioversion of AF, the atrial refractory period was 87+/-29 (HQ), 119+/-32 (Ci), 66+/-10 (Fl), and 73+/-18 msec (dS) (control: 146+/-18 msec). Atrial conduction velocity was 85+/-6, 71+/-11, 86+/-12, and 110+/-11 cm/sec compared with a control value of 116+/-10 cm/sec. Because directly after cardioversion the atrial wavelength was still very short (5.7 to 8.4 cm), the vulnerability for AF was still very high, and a single premature beat reinduced AF in 71% (Ci) to 100% (HQ, Fl, and dS) of the cases. CONCLUSION: In a goat model of sustained AF, Class IA, IC, and III drugs restored sinus rhythm in 67% to 92% of the cases. However, after cardioversion, the atrial wavelength was still abnormally short, and AF was readily inducible in 71% to 100% of the cases.

Animals↗
PubMed2000

Influence of age on atrial activation as measured by the P-wave signal-averaged electrocardiogram.

We used the P-wave signal-averaged electrocardiogram (SAECG) prospectively in 93 healthy volunteers of different ages and observed: (1) a positive correlation between P-wave duration on the SAECG and age (r = 0.39, p < 0.0001); and (2) the proportion of subjects with prolonged P-wave duration was increased with older age. These findings confirm the hypothesis that age-related atrial conduction delay in healthy subjects is present, and detectable by the P-wave SAECG.

Adult↗
PubMed1984

Automatic tachycardia recognition.

A microcomputer algorithm for tachycardia identification, suitable for use in an implanted antitachycardia pacemaker, is described. The system employs an atrial and ventricular electrogram, detects a sustained fast rate in either chamber, and awakens the main program to perform detailed analysis of the tachycardia and its immediately preceding beats. The algorithm distinguishes atrial, ventricular, and AV nodal and re-entrant tachycardia from high rates due to sinus tachycardia. For testing of the program, we used a data base of twenty-two tape-recorded and documented arrhythmias provoked during electrophysiologic studies in which atrial and ventricular bipolar electrodes were in place; twenty-one were successfully detected. These included atrial fibrillation, atrial flutter, atrial tachycardia, AV nodal re-entrant tachycardia, AV re-entrant tachycardia using an accessory pathway, and ventricular tachycardia with and without ventriculo-atrial conduction.

Atrial Fibrillation↗
PubMedDate not supplied

Electrophysiological effects of a new antiarrhythmic agent, nicainoprol, in humans.

The electrophysiological effects of nicainoprol, a new antiarrhythmic drug, were evaluated in a heterogeneous group of 23 patients aged 59 +/- 15 (mean +/- standard deviation) years. Nicainoprol was administered intravenously as a bolus of 1-2 mg/kg followed by continuous infusion at two dose levels. Electrophysiologic study was performed before and during the infusion at a steady-state drug level on each dose. The sinus node recovery time was unaltered in patients with normal sinus node function and was markedly prolonged in three of six patients with sinus node dysfunction. The intranodal conduction time (p less than 0.01) and the infranodal conduction time (p less than 0.001) increased, and the QRS duration (p less than 0.05) lengthened significantly even during 1 mg/kg/h. During 2 mg/kg/h, these times were further prolonged and, in addition, the intra-atrial conduction time (p less than 0.05), atrioventricular nodal effective and functional refractory periods (p less than 0.01), as well as the Wenckebach cycle length (p less than 0.001) also increased significantly. Similar depressant effects on the retrograde ventriculoatrial conduction system were also produced by nicainoprol. Retrograde His-atrioventricular nodal conduction was blocked in six of eight patients with this condition and was prolonged in the remaining two. Sustained supraventricular tachycardia was induced in seven patients, five of whom received nicainoprol during the tachycardia. The termination of supraventricular tachycardia was exclusively due to ventriculoatrial block in all five subjects, three with orthodromic circus movement tachycardia and two with atrioventricular nodal reentrant tachycardia of the slow-fast type. The reinducibility of supraventricular tachycardia could be prevented in five of seven patients.(ABSTRACT TRUNCATED AT 250 WORDS)

Adolescent↗
PubMed2003

Prognostic significance of serial P wave signal-averaged electrocardiograms following external electrical cardioversion for persistent atrial fibrillation: a prospective study.

The authors hypothesized that the persistence of abnormal atrial conduction detected by serial P wave signal-averaged electrocardiograms (P-SAECGs) can identify patients who are at high risk of recurrent atrial fibrillation (R-AF) following electrical cardioversion (ECV). P-SAECGs were recorded in 60 consecutive patients after ECV (53 men, age 66 +/- 10 years) and repeated in those who had remained in sinus rhythm (SR) 1 week, and 1, 3, and 6 months later. Filtered P wave duration (PD), root mean square (RMS) voltage of the terminal 40, 30, 20 ms (RMS-40, RMS-30, RMS-20) of the filtered P wave, RMS voltage of the entire filtered P wave (RMS-p), and the integral of the voltages in the entire P wave (integral-p) were analyzed. Thirty-one (52%) patients returned to AF within 1 week, an additional 11 (18%) by 1 month, and a further 2 (3.3%) at each subsequent assessment (3 and 6 months). The patients with R-AF had longer PD (157 +/- 24 vs 143 +/- 17 ms, P < 0.0001) and lower RMS-40, RMS-30, RMS-20 (5.3 +/- 2.0 vs 6.1 +/- 3.4 microV, P = 0.007; 4.3 +/- 1.5 vs 5.7 +/- 3.2 microV, P < 0.0001; 3.6 +/- 1.4 vs 5.2 +/- 3.0 microV, P < 0.0001, respectively) than those who remained in SR. These measurements did not change significantly in either group. RMS-p increased in SR patients (P = 0.009) but decreased in those who subsequently reverted to AF (P = 0.032) with a significant difference between the slopes of the RMS-p change (P = 0.006). Integral-p decreased from the time of ECV in the R-AF group only (P = 0.0028) and created a significant difference between the two slopes (P = 0.0004). The evolution of P-SAECG parameters after ECV differs in patients whose AF recurs versus patients who remain in SR.

Aged↗
PubMed1997

Optical mapping of conduction patterns of normal and tachycardia-like excitations in the rat atrium.

Multiple-site optical recording of transmembrane voltage activity (MSORTV), using a voltage-sensitive dye and a 12 x 12-element photodiode array, was employed to monitor action potentials in the rat atrium. Atrial preparations including the sinus node area, caval area, and atrial septum were dissected from adult rat hearts and stained with a voltage-sensitive merocyanine-rhodanine dye (NK2761). For suppression of optical artefacts due to contractile movements, a bathing medium containing 2,3-butanedione monoxime (BDM: 10-20 mM) was used. The spread of spontaneous excitation from the pacemaker was assessed optically by timing the initiation of the action potential-related extrinsic absorption changes. The optical signals were recorded from more than 300 contiguous loci in the atrium by sliding the photodiode array over the image of the preparation; in this way, the intra-atrial conduction pattern of spontaneous excitation was mapped. The obtained maps revealed a non-radial spread of excitatory waves originating in the pacemaking area over the atrium. Furthermore, we also mapped the conduction pattern of long-lasting tachycardia-like excitation evoked by a short train of electrical stimulation (5-10 Hz, 1-2s) applied with a bipolar electrode. These maps suggest that excitatory waves are propagated in a circular pathway which often surrounds the ostium of the superior or inferior vena cava. Various patterns for the pathway were also demonstrated optically.

Action Potentials↗