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PubMed2003

Acute and chronic effects of cryoablation of the pulmonary veins in the dog as a potential treatment for focal atrial fibrillation.

BACKGROUND: Atrial fibrillation (AF) may be triggered by premature atrial depolarizations originating in the pulmonary veins (PV). Radiofrequency catheter ablation of PV foci may prevent recurrence of AF, but may cause PV stenosis. Therefore, a safer method for ablation of PV foci is needed. This study evaluated the acute and chronic effects of PV ablation using a cryocatheter ablation (CCA) system, which may be less likely to cause PV stenosis. METHODS: CCA was performed by freezing for 5 minutes or more in one or more PVs in 10 anesthetized dogs. Pacing threshold and vessel diameter were measured before and after PV cryoablation. All dogs were restudied at 4.0 +/- 1.64 months (range 2-7) in a manner identical to baseline. RESULTS: CCA was performed in 27 PVs (range 1-4/dog), with a mean freeze time of 8.62 +/- 5.42 minutes per vein (range 5.23-22.06). Mean temperature for all freezes was -65 +/- 5.3 degrees C. Mean PV diameter was 6.49 +/- 1.73 vs 6.24 +/- 1.83 mm (p = NS) and mean pacing threshold 1.32 +/- 0.75 vs 9.36 +/- 5.93 mA (p <.01), before vs. acutely after ablation. At followup, at the ablation sites PV diameter (7.02 +/- 1.88 mm) was unchanged from baseline, whereas pacing threshold remained elevated (2.54 +/- 1.44 mA, p <.05 vs baseline). There were no acute or long-term complications. CONCLUSIONS; (1) CCA of PVs produced a significant rise in acute and chronic pacing threshold indicating loss of atrial conductivity. (2) CCA of PVs did not cause PV stenosis or other complications. (3) The data suggest that CCA of PVs may be a safe and effective method for treating focal AF.

Animals↗
PubMed2006

Intra- and interatrial asynchrony in patients with heart failure.

Heart failure (HF) is associated with atrial conduction delay. Color tissue Doppler imaging was used to evaluate intra- and interatrial asynchrony in patients with HF, patients with structural heart disease without HF, and controls. Twenty-three controls (mean age 65 +/- 13 years), 29 patients with structural heart disease without HF (mean age 68 +/- 9 years), and 29 patients with HF (mean age 67 +/- 9 years) were studied. Patients had no histories of atrial fibrillation. Echocardiographic color tissue Doppler imaging of the atria was performed. Measurements below the atrioventricular plane were selected on the right atrial (RA) free wall, interatrial septum (IAS), and left atrial (LA) free wall. The time difference from the onset of the P wave to the onset of the A wave at the right atrium (P-RA), the IAS (P-IAS), and the left atrium (P-LA) was measured. Asynchrony was defined as the differences between P-IAS and P-RA (RA asynchrony), P-LA and P-IAS (LA asynchrony), and P-LA and P-RA (interatrial asynchrony). In patients with HF, a significant increase in RA asynchrony was observed compared with controls and patients without HF (30 +/- 21 vs 12 +/- 13 and 14 +/- 15 ms, p <0.001). LA asynchrony was not different (19 +/- 26 vs 25 +/- 13 vs 25 +/- 14 ms, p = NS). Interatrial asynchrony was significantly increased in patients with HF (49 +/- 24 vs 37 +/- 9 and 39 +/- 17 ms, p = 0.04). There were moderate but significant correlations of RA asynchrony with log N-terminal-pro-B-type natriuretic peptide (r = 0.3, p = 0.01) and the ejection fraction (r = -0.4, p <0.001). In conclusion, in patients with HF, significant RA and interatrial asynchrony was documented, evaluated by noninvasive color tissue Doppler imaging. Asynchrony was related to N-terminal-pro-B-type natriuretic peptide and to the ejection fraction.

Aged↗
PubMed2005

P-wave signal-averaged electrocardiogram for predicting atrial arrhythmia after cardiac surgery.

BACKGROUND: Atrial arrhythmias (AF) are usually benign, but occur frequently after cardiac surgery. P-wave signal-averaged electrocardiogram has been used to characterize atrial conduction delay as a marker of risk of AF during sinus rhythm. METHODS: Ninety-five patients undergoing either primary isolated coronary artery bypass grafting or aortic valve replacement were enrolled. The duration and the root mean square voltage for the last 20 ms of filtered (40 to 300 Hz) P-wave of the spatial magnitude were recorded before surgery. Any episode of postoperative atrial fibrillation, atrial flutter, or paroxysmal atrial fibrillation lasting longer than 1 hour was considered as AF. RESULTS: Twenty-eight patients (29%) exhibited AF 3.0 +/- 2.3 days after surgery. The P-wave duration recorded with P-wave signal-averaged electrocardiogram was significantly prolonged in patients with AF (135 +/- 14 ms versus 127 +/- 9 ms; p = 0.002). Patients with AF more often had dilated left atrium (p = 0.003), left ventricular hypertrophy (p = 0.03), and advanced age (p = 0.02). Logistic regression analysis identified the following three variables as predictive of AF: P-wave duration of 135 ms or greater (p = 0.02; odds ratio, 3.5), patients 70 years of age and older (p = 0.03; odds ratio, 3.2), and left atrial dimension of 35 mm or greater (p = 0.03; odds ratio, 3.2). If a patient had two or more of these three risk factors, the occurrence of AF was predicted with a sensitivity of 75%, specificity of 76%, positive predictive accuracy of 57%, and negative predictive accuracy of 88%. CONCLUSIONS: The prolonged P-wave duration recorded with P-wave signal-averaged electrocardiogram, together with advanced age and left atrial enlargement, is a potent and independent predictor of AF after cardiac surgery. Patients with these risk factors may benefit from prophylactic antiarrhythmic treatment.

Aged↗
PubMed2005

Mechanisms of atrial remodeling and clinical relevance.

PURPOSE OF REVIEW: Atrial fibrillation usually occurs in the context of an atrial substrate produced by alterations in atrial tissue properties referred to as remodeling. Remodeling can result from cardiac disease, cardiac arrhythmias, or biologic processes such as senescence. Recent advances in understanding remodeling have allowed for insights into mechanisms underlying atrial fibrillation that have been transferred from experimental models to humans. This paper reviews recent progress in understanding atrial remodeling, as well as the consequent clinical insights into atrial fibrillation pathophysiology and treatment. RECENT FINDINGS: Two principal forms of remodeling have been described in animal models of atrial fibrillation: ionic remodeling, which affects cellular electrical properties, and structural remodeling, which alters atrial tissue architecture. Atrial tachycardias (particularly rapid tachyarrhythmias such as atrial flutter and atrial fibrillation) cause ionic remodeling, which decreases the atrial refractory period and promotes atrial reentry. Congestive heart failure produces atrial interstitial fibrosis, which promotes arrhythmogenesis by interfering with atrial conduction properties. Recent animal studies have provided insights into the pathways involved in remodeling, and have indicated the pathophysiological role of remodeling in specific contexts. In addition, work in animal models has provided information about pharmacological interventions that can prevent the development of remodeling. Clinical studies have shown that novel approaches to remodeling prevention identified in animal work have potential therapeutic value in man. SUMMARY: Understanding atrial remodeling has the potential to improve our appreciation of the pathophysiology of clinical atrial fibrillation and to allow for the development of useful new therapeutic approaches.

Action Potentials↗
PubMed2000

Conduction time oscillations precede the spontaneous termination of human atrioventricular reciprocating tachycardia.

Prior clinical research indicates that conduction slowing is the primary mechanism leading to the spontaneous termination of reentrant tachycardia in humans. Yet, some experimental models indicate that cycle length oscillations and enhanced conduction are important prerequisites. The role of oscillations in conduction times and enhanced conduction in the spontaneous termination of human reentrant tachycardia has not been adequately investigated. The electrophysiologic features preceding the spontaneous termination of orthodromic atrioventricular (AV) reciprocating tachycardia (RT) were evaluated in 21 patients, each of whom had a sustained (>60 seconds) and a spontaneously terminating (>/=10 beats and </=60 seconds) episode of AVRT during the same electrophysiologic study. Atrio-His, His-ventricular, interventricular, ventriculoatrial and atrial conduction times were measured for each beat of spontaneously terminating AVRT and for paired beats of sustained AVRT. Beats of spontaneously terminating and sustained tachycardia were pooled and Hadi multivariate outlier analysis was used to identify whether significant beat-to-beat alterations in conduction times preceded the spontaneous termination of reentry. Cycle lengths of sustained (348+/-62 msec) and spontaneously terminating AVRT (351+/-70 msec) were similar. Significant beat-to-beat oscillations in conduction times preceded the spontaneous termination of AVRT in 10 of the 21 (48%) patients. An apparent enhancement in atrio-His or ventriculoatrial conduction times immediately preceded the spontaneous termination of AVRT in 11 patients (52%), while an apparent conduction delay occurred in only 2 patients (10%). Moreover, significant oscillations in conduction times were present in 9 of the 11 patients (82%) with enhanced conduction, but only in 1 of the 10 (10%) remaining patients (p=0.002. Conduction time oscillations, which are related to apparent enhancement in atrio-His or ventriculoatrial conduction, frequently precede the spontaneous termination of reentry in humans.

Adult↗
PubMed2001

Effects of cardiac rehabilitation on atrial wave in patients after myocardial infarction.

Cardiac rehabilitation (CR) can improve cardiac hemodynamic performance in patients after myocardial infarction (MI). Little evidence is provided concerning the consequences of CR on atrial wave duration, and less is known about the link between pre-arrhythmogenic patterns and the cardiovascular performance improvement in these subjects. Twenty-six patients, post-MI 0 to 7 days, underwent a complete CR cycle and a signal-averaged electrocardiogram (SAECG) for the evaluation of atrial activation parameters (group 1) to appreciate if physical training can promote parallel improvement in cardiovascular and intra-atrial conduction parameters. A control group of 24 well-matched nonischemic subjects (group 2) was chosen for data comparison. Resting heart rate (p < 0.01) and resting double product (p < 0.01) decreased after CR in groups 1 and 2, while diastolic blood pressure at maximal stress was decreased in group 1 (p < 0.01) with a parallel increase in the time of physical training (p < 0.05). SAECG parameters of atrial activation were unchanged in group 1 after the comparison and only total atrial duration activation (dA) reached statistical significance (113.3 +/- 17.2 msec vs 120.8 +/- 14.2 msec, subjects after CR vs before CR, p < 0.01). CR could improve intra-atrial activation in subjects after MI, but the consequences of hemodynamic adjustment of the trained heart must undergo a more accurate evaluation to verify if CR can prevent adverse arrhythmogenic complications of MI through cardiovascular performance improvement.

Blood Pressure↗
PubMed1996

Electrophysiologic abnormalities of cardiac function in progressive systemic sclerosis.

The heart has been generally recognized as a target organ in progressive systemic sclerosis. Noninvasive studies have assessed the incidence and prognostic importance of cardiac arrhythmias in these patients. However, detailed exploration of the function of impulse formation and the conduction system of the heart in these patients has never been reported. Therefore, invasive electrophysiologic studies were performed in 30 patients with systemic sclerosis, all of whom had neither obvious cardiac involvement nor cardiac arrhythmias, and in 32 subjects with no evidence of heart disease, who served as a control group. Corrected sinus node recovery time in patients with systemic sclerosis was significantly longer (P < .001) than in the control group, as was the HV interval (P < .05). Of the 30 patients with systemic sclerosis, 10 had an HV interval of 60 ms or longer. In four patients with systemic sclerosis, the recorded AH interval exceeded 125 ms. The intra-atrial conduction time tended to increase to a significant degree (P < .05) in patients with systemic sclerosis. The interatrial conduction time was much longer (P < .001), and the maximal conduction delay to the atrioventricular junction and to the distal coronary sinus was much greater in the patients with systemic sclerosis than in the control group (P < .001 for both). Supraventricular tachyarrhythmias were induced in 15 patients with systemic sclerosis versus 3 control group subjects (P < .001). With respect to corrected sinus node recovery time, AH and HV intervals, atrial vulnerability, and ventricular tachycardia, 3 of the 30 patients with systemic sclerosis had abnormal findings in one of these parameters and 14 had abnormalities in more than one. These results suggest that a broad spectrum of electrophysiologic abnormalities is present in patients with systemic sclerosis, which can be revealed only by invasive studies. Furthermore, this study provides additional support for the hypothesis that diffuse myocardial involvement is characteristic of scleroderma patients, since a number of these patients showed more than one electrophysiologic defect.

Adolescent↗
PubMed1998

[Long term follow-up in patients with the permanent form of junctional reciprocating tachycardia treated with radiofrequency ablation].

OBJECTIVES: This study sought to determine the long-term follow-up, safety and efficacy of radiofrequency catheter ablation in patients with the permanent form of junctional reciprocating tachycardia. We assessed the reversibility of tachycardia-related left ventricular dysfunction and we detailed the location and electrophysiologic characteristics of these atrioventricular decremental pathways. BACKGROUND: Permanent junctional reciprocating tachycardia is an infrequent form on reciprocating tachycardia, commonly incessant and usually drug-refractory. The electrocardiographic hallmarks include an RP interval > PR with inverted P waves in leads II, III, aVF and V3-V6. During tachycardia, retrograde ventriculo-atrial conduction occurs over an accessory pathway with decremental conduction properties, located predominantly in the posteroseptal zone. It is known that long lasting and incessant tachycardia may result in tachycardia-related severe ventricular dysfunction, the so called tachycardiomyopathy. PATIENTS AND METHODS: We included 24 patients (9 males, 15 females; mean age 42 +/- 22 years) with the diagnosis of permanent junctional reciprocating tachycardia at electrophysiologic study. Six patients had tachycardia-related left ventricular dysfunction. Radiofrequency energy was delivered at the site of earliest retrograde atrial activation during reciprocating tachycardia (n = 22) or ventricular pacing (n = 2). All patients were followed at the outpatient clinic and serial echocardiograms were performed in those who presented depressed left ventricular function. RESULTS: Radiofrequency catheter ablation was performed in 24 decremental accessory pathways. Earliest retrograde atrial activation was right posteroseptal in 22 patients (92%), right midseptal in 1 (4%) and right posterolateral in 1 (4%). Twenty-three accessory pathways were successfully ablated with a mean of 5 +/- 3 (median, 4) radiofrequency applications of a mean duration of 48 +/- 13 s. Only the midseptal accessory pathway could not be ablated. After a mean follow-up of 21 +/- 16 months (median, 15; range 2 to 64) 22 patients remain asymptomatic. There were recurrences in 4 patients after the initial successful ablation (three during the first month and one during the second month after the procedure), two were ablated in a second ablation procedure, one patient required a third procedure and one required a fourth. All patients with left ventricular dysfunction experienced an improvement after ablation. Mean preablation left ventricular ejection fraction in patients with tachycardiomyopathy was 28 +/- 6% (median, 27) and raised to 51 +/- 16% (median, 47) after ablation (p < 0.02). CONCLUSIONS: Our study supports the concept that radiofrequency catheter ablation is a safe and useful treatment for patients with permanent junctional reciprocating tachycardia. Radiofrequency current should be the treatment of choice in these patients because this arrhythmia is usually drug-refractory. The majority of accessory pathways with decremental conduction properties are localized in the posteroseptal zone. Cessation of the arrhythmia after successful ablation results in recovery of left ventricular dysfunction.

Adolescent↗
PubMed2006

What are arrhythmogenic substrates in diabetic rat atria?

INTRODUCTION: Diabetes mellitus is one of the significant independent risk factors for the development of atrial fibrillation (AF). However, the pathophysiological mechanisms of the relationship have not been fully elucidated. METHODS AND RESULTS: The genetic type II diabetes (GK) rats and their original (Wistar) ones were subjected to electrophysiological (n = 8 per group) and histological (n = 7 per group) studies. At 40 weeks old, when GK rats had significantly (P < 0.01) more increased plasma glucose and HbA(1c) values than Wistar rats, atrial electrical stimuli in the isolated-perfused hearts induced significantly greater number of repetitive atrial responses in GK rats than in Wistar rats (47.9 +/- 17.5 vs 3.1 +/- 1.3 beats, respectively, P < 0.01). GK rats showed significantly longer intra-atrial activation time than Wistar rats (18.3 +/- 0.4 ms vs 15.9 +/- 0.5 ms, P < 0.01) without any significant difference in the atrial refractoriness. The histological examination revealed significantly increased diffuse fibrotic deposition in GK rats atria compared with Wistar ones (P < 0.01). CONCLUSION: The present diabetic GK rat showed increased atrial arrhythmogenicity with intra-atrial conduction disturbance, and thus indicated that the structural remodeling of atrium characterized by diffuse interstitial fibrosis would be a major substrate for diabetes-related AF.

Animals↗
PubMed1997

Incidence of induced atrial fibrillation/flutter in complete atrioventricular block. A concept of 'atrial-malfunctioning' atrio-hisian block.

BACKGROUND: Atrial fibrillation/flutter (Af) has been considered to occur coincidentally with atrioventricular (AV) block. However, a case with complete AV block was reported to histologically show fibrotic changes solely in the atrial muscles but neither in the AV node nor in the His bundle, indicating a possible relation between AV block and atrial tachyarrhythmias. To test a hypothesis that AV block and Af are causally interrelated, we investigated the incidence and electrophysiological characteristics of Af in complete AV block. METHODS AND RESULTS: Forty-two patients with persistent complete AV block underwent the electrophysiological study. Patients with spontaneous/electrically induced Af were compared with the other patients with respect to their electrophysiological variables. Of the 42 patients, Af was transiently induced by electrical stimulation in 5 patients (11.9%), while persistent Af was observed in 2 patients (4.8%, AH and HV block). AV block in the 5 patients with induced Af was invariably due to AH block. AH block complicated by persistent/induced Af was marked by relatively short RR intervals, significantly short junctional recovery time, and impaired intra-atrial conduction. CONCLUSIONS: Electrically induced Af in complete AV block was associated frequently with complete AH block. These patients were characterized differently from the commonly recognized AV block and therefore may stand as a unique subgroup of AH block.

Adult↗
PubMed2006

Effects of right bundle branch block on the antidromic circus movement tachycardia in patients with presumed atriofascicular pathways.

BACKGROUND: The typical and most common tachycardia in patients with atriofascicular pathways is a macro reentrant tachycardia, with anterograde conduction over the decrementally conducting bypass tract and retrograde conduction over the right bundle branch-His-AV node axis resulting in a short V-right bundle branch and short V-H interval. OBJECTIVES: To report on changes in rate and QRS configuration when right bundle branch block (RBBB) develops spontaneously during antidromic tachycardia using an atriofascicular fiber. METHODS: Three of 25 patients with an antidromic circus movement tachycardia using a right-sided atriofascicular pathway showed episodes of right bundle branch block (RBBB) during ventriculo-atrial conduction. Effect of retrograde RBBB on tachycardia rate and QRS configuration was studied using intracardiac and extracardiac recordings. RESULTS: All 3 patients showed prolongation of their V-A interval when retrograde RBBB occurred during tachycardia, resulting in a longer tachycardia cycle length. The VA time increase ranged from 85 to 100 msec, with a mean 346 +/- 5 msec. Two of the 3 patients also showed a change in QRS configuration due to a more leftward shift of the frontal plane QRS axis. CONCLUSION: Rate changes in antidromic tachycardia in patients with atriofascicular fibers can be based on a shift in VA conduction from one bundle branch to the other. This may be accompanied by changes in the frontal plane QRS axis because of a change in ventricular activation sequence.

Adult↗
PubMed2004

Atrial electrophysiologic abnormalities in patients with Wolff-Parkinson-White syndrome but without paroxysmal atrial fibrillation.

BACKGROUND: Paroxysmal atrial fibrillation (PAF) frequently occurs in patients with Wolff-Parkinson-White (WPW) syndrome. HYPOTHESIS: The purpose of this study was to analyze the atrial electrophysiologic abnormalities and vulnerability to develop atrial fibrillation (AF) in patients with WPW syndrome but with no previous history of PAF. METHODS: We investigated atrial electrophysiologic abnormalities and vulnerability to AF in patients with WPW syndrome but without PAF. An electrophysiologic study was performed in 28 patients with WPW syndrome, 23 with atrioventricular nodal reentrant tachycardia (AVNRT) and 25 with other arrhythmias (control), all of whom had no history of PAF. The following atrial excitability parameters were assessed: effective refractory period (ERP), spontaneous or paced (A1) and extrastimulated (A2) atrial electrogram widths, percent maximum atrial fragmentation (%MAF; A2/A1 x 100), wavelength index (WLI; ERP/A2), and inducibility of AF. RESULTS: The ERP tended to be shorter in patients with WPW syndrome and in those with AVNRT than in the control group. The %MAF increased (154 +/- 33 vs. 137 +/- 23%, p < 0.05) and WLI decreased (2.7 +/- 0.8 vs. 3.4 +/- 1.0, p < 0.05) significantly in patients with WPW syndrome compared with the control group; however, these parameters in patients with AVNRT showed intermediate values. Atrial fibrillation was more inducible in patients with WPW syndrome (4/28 [14.3%]) than in those with AVNRT (4.3% [1/23]) and the control group (0/25 [0%]). With respect to patients with WPW syndrome and with and without inducible AF, the %MAF increased (195 +/- 23 vs. 148 +/- 30%, p < 0.01) and the WLI decreased (2.2 +/- 0.3 vs. 2.9 +/- 0.9, p < 0.05) in subjects with inducible AF. CONCLUSIONS: Atrial electrophysiologic abnormalities, especially atrial conduction delays, are more prominent in patients with WPW syndrome, even if they had no previous history of PAF. These abnormalities may play an important role in determining the vulnerability to AF.

Adolescent↗
PubMed2001

Frequency-dependent electrophysiological effects of flecainide, nifekalant and d,l-sotalol on the human atrium.

To compare the effects of class Ic and III antiarrhythmic agents on the termination and prevention of atrial fibrillation, the present study investigated the use-dependent electrophysiological effects of flecainide, nifekalant and d,l-sotalol on the human atrium. Flecainide significantly prolonged effective refractory period (ERP), intra-atrial conduction time (IACT) and monophasic action potential duration (MAPD), and its effects on ERP and IACT were use-dependent. Nifekalalant significantly prolonged ERP and MAPD, and these effects were reverse use-dependent; however, there was no significant change in IACT. d,l-Sotalol significantly prolonged MAPD and the effect was reverse use-dependent. It significantly prolonged ERP, but the effect was not reverse use-dependent. d,l-Sotalol increased IACT in a use-dependent manner. Thus, for atrial fibrillation, class Ic antiarrhythmic agents might be more effective in termination and class III antiarrhythmic agents might be more effective in prevention.

Action Potentials↗
PubMed1988

Electrocardiographic features of P waves from patients with transient atrial fibrillation.

The electrocardiographic characteristics of P waves from patients having more than two episodes of transient atrial fibrillation (T-af) were examined during an episode-free period. The P waves of these patients recorded from the X Y Z leads of Frank's lead system on high-speed and high-gain recordings revealed longer durations than those of the normal control subjects (p less than 0.001), while the standard 12 lead ECG did not show any difference in width between the 2 groups. The configuration of the P loops on VCGs showed abnormal irregularities, such as bites or notches, in 16 of 28 cases of the T-af group. The maximum magnitudes of the P loops in VCGs and those in SVECGs were greater in the T-af group than those in the normal group (p less than 0.05). Body surface maps during atrial excitation showed that the duration of the anterior maximum was longer than that of the left maximum, and that the values of both maxima of the T-af group were longer than those of the normal group (p less than 0.01). These findings suggest the presence of intra-atrial conduction disturbances in patients with this disease, which might contribute to the genesis of this arrhythmia. Furthermore, these electrocardiographic characteristics of the P waves in the T-af group can be used as predictive and diagnostic signs of this arrhythmia even during an episode-free period.

Adult↗
PubMed2003

Effects of angiotensin II type 1 receptor antagonist on electrical and structural remodeling in atrial fibrillation.

UNLABELLED: The purpose of the present study was to evaluate the effect of angiotensin II type 1 receptor (AT1R) antagonist on chronic structural remodeling in atrial fibrillation (AF). BACKGROUND: We previously reported that an AT1R antagonist, candesartan, prevents acute electrical remodeling in a rapid pacing model. However, the effect of candesartan on chronic structural remodeling in AF is unclear. METHODS: Sustained AF was induced in 20 dogs (10 in a control group and 10 in a candesartan group) by rapid pacing of the right atrium (RA) at 400 beats/min for five weeks. Candesartan was administered orally (10 mg/kg/day) for one week before rapid pacing and was continued for five weeks. The AF duration, atrial effective refractory period (AERP) at four sites in the RA, and intra-atrial conduction time (CT) from the RA appendage to the other three sites were measured every week. RESULTS: The mean AF duration in the control group after five weeks was significantly longer than that with candesartan (1,333 +/- 725 vs. 411 +/- 301 s, p < 0.01). The degree of AERP shortening after five weeks was not significantly different between the two groups. The CT from the RA appendage to the low RA after five weeks with candesartan was significantly shorter than that in the control (43 +/- 14 vs. 68 +/- 10 ms, p < 0.05). The candesartan group had a significantly lower percentage of interstitial fibrosis than the control group (7 +/- 2% vs. 16 +/- 1% at the RA appendage, p < 0.001). CONCLUSIONS: Candesartan can prevent the promotion of AF by suppressing the development of structural remodeling.

Angiotensin Receptor Antagonists↗
PubMed2000

The ultrarapid and the transient outward K(+) current in human atrial fibrillation. Their possible role in postoperative atrial fibrillation.

Atrial fibrillation (AF) causes distinct changes in atrial conduction, characterized as electrical remodeling. Experimental data on the possible significance of alterations of specific K(+)outward currents in this process are still limited in human AF. The ultra-rapid delayed rectifier current (I(Kur)) has not been studied in AF with respect to its sensitivity to 4-Aminopyridine (4-AP). To clarify the role of (1) the 4-AP sensitive I(Kur)current, compared to recordings without using 4-AP (I(Kur*)), and (2) the transient outward current (I(to)) in changes of atrial repolarization associated with AF, whole cell voltage-clamp recordings were obtained from atrial myocytes of patients undergoing elective cardiac surgery, with and without a history of atrial fibrillation (AF/non-AF). Further, a possible relation between experimental data and postoperative AF was studied. In AF patients, I(Kur*)was reduced by 40% [5.00+/-0.32 pA/pF (non-AF) and 2.91+/-0. 45 pA/pF (AF) at +50 mV, P<0.0001, n=22/11], I(Kur)by 55% [3.81+/-0. 30 pA/pF (non-AF) and 1.71+/-0.20 pA/pF (AF) at +50 mV, P<0.0001, n=22/11]. The mean amplitude of I(Kur)was significantly smaller than I(Kur*). Consistently, I(to)was reduced by 44% [11.57+/-0.77 pA/pF (non-AF) and 6.51+/-1.31 pA/pF (AF), P<0.01, n=25/11]. In 48% of non-AF patients, postoperative AF was detected. The corresponding voltage-clamp recordings showed a trend to reduced I(Kur*)and I(Kur)currents, although it did not reach statistical significance. The consistent reduction of all three K(+)currents investigated due to the presence of AF indicates an important association of abnormalities in cellular repolarization with the onset and the self-sustaining nature of human AF.

4-Aminopyridine↗
PubMed1997

Critical atrial site for ablation of pacing-induced atrial fibrillation in the normal dog heart.

INTRODUCTION: Radiofrequency catheter ablation (RFA) has been used recently to treat atrial fibrillation (AF). The purpose of this study was to investigate a new approach to preventing AF by RFA. METHODS AND RESULTS: In open chest, anesthetized dogs, AF (lasting > 30 sec) was induced after burst stimulation, and electrophysiologic parameters were recorded before and after RFA. In group 1 (9 dogs) we performed selective and combined slow and fast pathway RFA, whereas in group 2 (11 dogs) RFA was applied as a linear lesion at the mid-atrial septum between the inferior vena cava and the fossa ovalis. After ablation, the Wenckebach cycle length was significantly prolonged only in group 1 (194 +/- 23 vs 282 +/- 35 msec, P = 0.002), whereas the interval between the stimulus (S) artifact applied at the high right atrium to the His bundle (H) (SH interval) prolonged to the same extent in both groups (162 +/- 14 vs 146 +/- 45 msec, P = NS); group 1 due to an A-H prolongation whereas in group 2 it was due to an intra-atrial conduction delay. In group 1 AF still remained inducible, although with a longer mean R-R interval (215 +/- 16 vs 433 +/- 88 msec, P < 0.05). No instance of complete AV block developed. In group 2, sustained AF was noninducible in 10 dogs and its duration was markedly shorter in the remaining one (8 sec). Gross anatomy and histology did not reveal any damage inside of Koch's triangle, and particularly to the compact AV node. CONCLUSION: These findings suggest that RFA at the mid-atrial septum prevents AF in the normal dog heart. This approach might also be successful in those clinical settings in which the atrial septum plays a critical role in the maintenance of sustained AF.

Animals↗
PubMed2003

Clinical significance of prolonged P wave width after right atrial appendage pacing in sick sinus syndrome.

The present study investigated both the clinical significance of atrial fibrillation (AF) before right atrial appendage (RAA) pacing and the influence of prolonged P wave on AF occurrence in RAA-paced patients with sick sinus syndrome (SSS). Fifty-seven patients (age 68+/-10 years; 19 men, 38 women) with SSS who underwent RAA pacing were divided into 2 groups: 23 patients without AF before pacing (I + II; Rubenstein I or II) and 34 patients with AF before pacing (III; Rubenstein III). The P wave duration in intrinsic rhythm and with RAA pacing were measured on the standard electrocardiography in leads II and V(1) with the use of a digitizing tablet. Group III was further subdivided into 2 groups: 20 patients (IIIb) with a paced P wave >130 ms in both leads II and V(1) and the other 14 patients (IIIa). The duration of the intrinsic P wave in leads II and V(1) was significantly greater in group III than in group I + II (119+/-20 vs 108+/-21 ms, p=0.0417, 106+/-16 vs 95+/-21 ms, p=0.0258, respectively). During the follow-up of 40+/-21 months, AF recurrence was significantly higher in group IIIb than in groups IIIa and I + II (17/20 vs 5/14 vs 2/23 p<0.0001). A few occurrences of AF were observed by conventional RAA pacing in patients without AF before pacing. However, SSS with AF before pacing caused a significant intra-atrial conduction disturbance and a high incidence of AF recurrence after implantation of RAA pacing, especially in patients with a prolonged paced P wave, in whom new pacing modalities may be needed to shorten paced P wave duration and prevent AF.

Aged↗