Reverse Electrical Remodeling of the Atria Post Cardioversion in Patients Who Remain in Sinus Rhythm Assessed by Signal Averaging of the P-Wave

Pulmonary vein isolation alone or in combination with substrate modulation after electrical cardioversion failure in patients with persistent atrial fibrillation: The PACIFIC trial: Study design

INTRODUCTION

Pulmonary vein isolation (PVI) is effective at treating 50% of unselected patients with persistent atrial fibrillation (AF). Alternatively, PVI combined with a new ablation strategy entitled the Marshall-PLAN ensures a 78% 1-year sinus rhythm (SR) maintenance rate in the same population. However, a substantial subset of patients could undergo the Marshall-PLAN unnecessarily. It is therefore essential to identify those patients who can be treated with PVI alone versus those who may truly benefit from the Marshall-PLAN before ablation is performed. In this context, we hypothesized that electrical cardioversion (EC) could help to select the most appropriate strategy for each patient.

METHODS

In this multicentre, prospective, randomized study, patients with AF recurrence within 4 weeks after EC will be randomized 1:1 to PVI alone or the Marshall-PLAN. Conversely, patients in whom SR is maintained for ≥4 weeks after EC will be treated with PVI only and included in a prospective registry. The primary endpoint will be the 1-year SR maintenance rate after a single ablation procedure.

RESULTS AND CONCLUSION

The Marshall-PLAN might be necessary in patients with an advanced degree of persistent AF (i.e., where SR is not maintained for ≥4 uninterrupted weeks after EC). Conversely, in patients with mild or moderate persistent AF (i.e., where SR is maintained for ≥4 weeks after EC), PVI alone might be a sufficient ablation strategy. The PACIFIC trial is the first study designed to assess whether rhythm monitoring after EC could help to identify patients who should undergo adjunctive ablation strategies beyond PVI.

Limited Ablation for Persistent Atrial Fibrillation Using Preprocedure Reverse Remodelling

Pulmonary vein isolation (PVI) has been demonstrated to be a highly effective treatment option for patients with paroxysmal atrial fibrillation (AF), but less effective for patients with persistent AF. The lower efficacy of PVI alone has been attributed to adverse atrial electrical and structural remodelling in the setting of AF. Strategies to improve efficacy of catheter ablation for persistent AF alter these pathophysiological characteristics of atrial tissue remodelling. Here we will review the physiology of atrial electrical remodelling observed during AF and evidence that it is reversible. Further, we will explore its uses to reduce the amount of atrial tissue that needs to be ablated to successfully treat patients with persistent AF.

Usefulness of P-wave signal averaging to predict atrial fibrillation recurrences after electrical cardioversion

BACKGROUND

Accurate markers of atrial fibrillation (AF) recurrences after electrical cardioversion (ECV) are lacking. This study was conducted to assess the value of P-wave signal averaging (SAPW) for predicting AF recurrences in a nonselected patients population submitted to ECV.

METHODS

A total of 133 patients (107 males, 26 females, mean age 66 ± 9 years) were included after successful ECV for persistent AF (mean duration of AF 3.6 ± 2.2 months). The mean ejection fraction (EF) was 60 ± 9%, and left atrial (LA) diameter was 44 ± 6 mm. SAPW ECG was obtained immediately after ECV and patients were prospectively followed.

RESULTS

During a mean follow-up of 8.9 ± 5.2 months, AF recurrences occurred in 40.6% (54/133). No SAPW parameters was statistically different between the group of patients with and the group without recurrences. Recurrences were less often observed in patients with a total P-wave duration <150 ms (16/52 or 31% vs 38/81 or 47% in patients with total P-wave duration ≥150 ms) but the difference was not statistically different (P = 0.07). P-wave duration was correlated with age (r = 0.32; P < 0.001) and left atrial diameter (r = 0.19; P = 0.02). Age, sex, structural heart disease, amiodarone therapy, or hypertension were not associated with AF recurrences but patients without recurrences had a shorter AF duration (P = 0.001) and more often had a history of previous ablation (P = 0.027).

CONCLUSION

In this unselected "real-life" group of patients submitted to ECV for persistent AF, none of the SAPW parameters, including total filtered P-wave duration, was able to predict AF recurrences.

Reverse atrial electrical remodelling induced by continuous positive airway pressure in patients with severe obstructive sleep apnoea

BACKGROUND

Obstructive sleep apnoea (OSA) is associated with cardiovascular morbidity and mortality, including atrial arrhythmias. Continuous positive airway pressure (CPAP) is the gold standard treatment for OSA; its impact on atrial electrical remodelling has not been fully investigated. Signal-averaged p-wave (SAPW) duration is an accepted marker for atrial electrical remodelling.

OBJECTIVE

The objective of this study is to determine whether CPAP induces reverse atrial electrical remodelling in patients with severe OSA.

METHODS

Consecutive patients attending the Sleep Disorder Clinic at Kingston General Hospital underwent full polysomnography. OSA-negative controls and severe OSA were defined as apnoea-hypopnea index (AHI) < 5 events/hour and AHI ≥ 30 events/hour, respectively. SAPW duration was determined at baseline and after 4-6 weeks of CPAP in severe OSA patients or without intervention controls.

RESULTS

Nineteen severe OSA patients and 10 controls were included in the analysis. Mean AHI and minimum oxygen saturation were 41.4 ± 10.1 events/hour and 80.5 ± 6.5 % in severe OSA patients and 2.8 ± 1.2 events/hour and 91.4 ± 2.1 % in controls. At baseline, severe OSA patients had a greater SAPW duration than controls (131.9 ± 10.4 vs 122.8 ± 10.5 ms; p = 0.02). After CPAP, there was a significant reduction of SAPW duration in severe OSA patients (131.9 ± 10.4 to 126.2 ± 8.8 ms; p < 0.001), while SAPW duration did not change after 4-6 weeks in controls.

CONCLUSION

CPAP induced reverse atrial electrical remodelling in patients with severe OSA as represented by a significant reduction in SAPW duration.

P wave signal-averaged ECG in normal population and in patients with converted atrial fibrillation

BACKGROUND

Signal-averaged electrocardiography of the P wave (P wave SAECG) is a noninvasive method for evaluating the risk of atrial fibrillation (AF). We aimed to study P wave SAECG parameters in a large number of apparently healthy subjects and to compare them with patients with converted AF.

METHODS

We examined 591 individuals; P wave SAECG were recorded in 330 normal subjects, 31 patients with converted persistent AF and 57 patients with converted paroxysmal AF immediately after conversion, at 12 and 24 hours after conversion, then after 3 and 6 months. P wave SAECG were recorded using a commercially available machine aiming to obtain a noise level <1 μV.

RESULTS

In the normal population the duration of the filtered P wave (PWD) was higher in men. P wave duration, RMS(40) and RMS(30) were significantly correlated with age. By comparing the normal population with patients with persistent AF converted to sinus rhythm we demonstrated significant differences in PWD and P wave integral. Patients with recurrent persistent AF had significantly higher PWD. The study of patients with paroxysmal AF, compared to the control group, showed significant increase of the same parameters: PWD and integral of the P wave. Patients with recurrent paroxysmal AF had higher PWD and lower RMS(40) , RMS(30) , RMS(20) .

CONCLUSIONS

Filtered P wave duration was higher in men; PWD was weakly but significantly correlated with age. Patients with paroxysmal or persistent AF converted to sinus rhythm had significantly higher P wave duration and P wave integral.

Improved outcome following restoration of sinus rhythm prior to catheter ablation of persistent atrial fibrillation: a comparative multicenter study

BACKGROUND

Catheter ablation of persistent atrial fibrillation (AF) is associated with longer procedure times and lower long-term success rates than that of paroxysmal AF.

OBJECTIVE

To test the hypothesis that restoration/maintenance of sinus rhythm (SR) preablation would facilitate AF termination and improve outcomes in patients with persistent AF.

METHODS

We conducted a 2-group cohort study of consecutive patients with persistent AF and SR restored for at least 1 month prior to ablation (SR group; n = 40) and controls matched by age, sex, and AF duration (control group; n = 40). Radiofrequency stepwise catheter ablation was performed in AF for both groups (induced and spontaneous, respectively). Success was defined as freedom from atrial tachyarrhythmia without antiarrhythmic drugs beyond 1 year of follow-up.

RESULTS

During the index ablation procedure, AF cycle length was longer in the SR group than in the control group (183 ± 32 ms vs 166 ± 20 ms; P = .06), suggestive of reverse remodeling. In the SR group, AF more frequently terminated during ablation (95.0% vs 77.5%; P <.05) and required less extensive ablation of complex fractionated electrograms (40.0% vs 87.5%; P <.001) and linear lesions (42.5% vs 82.5%; P <.001). Mean procedural (199.8 ± 69.8 minutes vs 283.5 ± 72.3 minutes; P <.001), fluoroscopy (51.0 ± 24.9 minutes vs 96.3 ± 32.1 minutes; P <.001), and radiofrequency energy delivery (47.5 ± 18.9 minutes vs 97.0 ± 30.6 minutes; P <.001) times were shorter in the SR group. Clinical success rates were similar between groups for first (55.0% vs 45.0%; P = .28) and last (80.0% vs 70.0%; P = .28) procedures, during similar follow-up periods (21.1 ± 9.7 months).

CONCLUSIONS

Restoration of SR prior to catheter ablation for persistent AF whenever possible decreases the extent of ablation with the same high clinical efficacy.

Pulmonary vein isolation alone in patients with persistent atrial fibrillation: an ablation strategy facilitated by antiarrhythmic drug induced reverse remodeling

INTRODUCTION

Pulmonary vein isolation (PVI) alone has been thought to be insufficient in patients with persistent atrial fibrillation (PersAF). We hypothesized that preablation treatment of PersAF with a potent antiarrhythmic drug (AAD) would facilitate reverse atrial remodeling and result in high procedural efficacy after PVI alone.

METHODS AND RESULTS

Seventy-one consecutive patients (59.4 ± 9.8 years) with PersAF and prior AAD failure were treated with oral dofetilide (768 ± 291 mcg/day) for a median of 85 days pre-PVI. P-wave duration (Pdur) on ECG was used to assess reverse atrial remodeling. Thirty-five patients with paroxysmal (P) AF not treated with an AAD served as controls. All patients underwent PVI alone; dofetilide was discontinued 1-3 mos postablation. In the PersAF patients, the Pdur decreased from 136.3 ± 21.7 ms (assessed postcardioversion on dofetilide) to 118.6 ± 20.4 ms (assessed immediately prior to PVI) (P < 0.001). In contrast, no change in Pdur (122.6 ± 11.5 ms vs. 121.3 ± 13.7 ms, P = NS) was observed in PAF patients. The 6 and 12 mos AAD-free response to ablation was 76% and 70%, respectively, in PersAF patients, similar to the 80% and 75%, response in PAF patients (P = NS). A decline in Pdur in response to dofetilide was the only predictor of long-term clinical response to PVI in patients with PersAF.

CONCLUSIONS

Pre-treatment with AAD resulted in a decrease in Pdur suggesting reverse atrial electrical remodeling in PersAF patients. This may explain the excellent clinical outcomes using PVI alone, and may suggest an alternative ablation strategy for PersAF.

Reversal of atrial remodeling after cardioversion of persistent atrial fibrillation measured with magnetocardiography

BACKGROUND

Atrial fibrillation (AF) causes electrical, functional, and structural changes in the atria. We examined electrophysiologic remodeling caused by AF and its reversal noninvasively by applying a new atrial signal analysis based on magnetocardiography (MCG).

METHODS

In 26 patients with persistent AF, MCG, signal-averaged electrocardiography (SAECG), and echocardiography were performed immediately after electrical cardioversion (CV), and repeated after 1 month in 15 patients who remained in sinus rhythm (SR). Twenty-four matched subjects without history of AF served as controls. P-wave duration (Pd) and dispersion (standard deviation of Pd values in individual channels) and root mean square amplitudes of the P wave over the last 40 ms portions (RMS40) were determined.

RESULTS

In MCG Pd was longer (122.8 +/- 18.2 ms vs 101.5 +/- 14.6 ms, P < 0.01) and RMS40 was higher (60.4 +/- 28.2 vs 46.9 +/- 19.1 fT) in AF patients immediately after CV as compared to the controls. In SAECG Pd dispersion was increased in AF patients. Mitral A-wave velocity and left atrial (LA) contraction were decreased and LA diameter was increased (all P < 0.01). After 1 month, Pd in MCG still remained longer and LA diameter greater (both P < 0.05), while RMS40 in MCG, Pd dispersion in SAECG, mitral A-wave velocity, and LA contraction were recovered.

CONCLUSIONS

Magnetocardiographically detected atrial electrophysiologic alterations in persistent AF diminish rapidly although incompletely during maintained SR after CV. This might be related to the known early high and late lower, but still existent tendency to AF relapses.

Impact of obstructive sleep apnea on the atrial electromechanical activation time

BACKGROUND

Obstructive sleep apnea (OSA) is closely associated with atrial fibrillation, which is provoked by electrical and structural remodeling. However, the association between OSA and atrial remodeling has not been fully elucidated.

METHODS AND RESULTS

Atrial electromechanical activation time (EMAT) was investigated using tissue Doppler imaging (TDI) in men with severe OSA (n=24) and control subjects (n=24). The EMAT was determined as the time interval from the initiation of P-wave deflection until the peak of local lateral left atrial (LA) TDI signal. The early diastolic velocity of the mitral annulus (E(a)) and the EMAT were significantly lower and longer in OSA cases than in controls (E(a): 6.1+/-0.9 cm/s vs 7.3+/-1.5 cm/s, P=0.001; EMAT: 129.7+/-11.5 ms vs 118.5+/-12.3 ms, P=0.002). Among OSA cases, the apnea - hypopnea index (AHI) was significantly correlated with EMAT (r=0.660, P<0.001), E(a) (r=-0.609, P=0.002), LA dimension (r=0.486, P=0.016), and early diastolic velocity of mitral flow (E)/E(a) ratio (r=0.418, P=0.042). In multivariate stepwise linear regression analysis, EMAT was independently associated with AHI (P=0.025) and E(a) (P=0.028) in OSA cases.

CONCLUSION

EMAT measured by TDI could be a useful parameter for identifying atrial remodeling in patients with severe OSA.

The electrical substrate of vagal atrial fibrillation as assessed by the signal-averaged electrocardiogram of the P wave

BACKGROUND

The autonomic nervous system is thought to be involved in the initiation of atrial fibrillation (AF). However, there is a distinct entity of vagal AF characterized by episodes occurring at rest, postprandially, or during sleep. The purpose of this study was to compare intraatrial conduction in patients with vagally mediated AF to those with nonvagal AF, using the signal-averaged electrocardiogram (SAECG) of P wave.

METHODS

SAECG of P wave was performed in 58 patients with AF using the Marquette Medical System, and the mean filtered P-wave duration (SAPW) was measured. Nine patients were categorized as having pure vagal AF (Group I), and 42 patients as having nonvagal AF (Group II); the remaining seven patients were excluded from analysis because of incomplete data.

RESULTS

The patients in Group I were significantly younger and more likely to have paroxysmal lone AF, as compared to those in Group II. There was no significant difference in left atrial size and left ventricular function in the two groups. The mean SAPW was significantly shorter in Group I when compared to Group II (118 +/- 5 ms vs 149 +/- 39 ms, P < 0.001). Whereas all patients in Group I had a normal SAPW, 79% of patients in Group II had an abnormal SAPW (P < 0.001). A normal SAPW was significantly predictive of vagal AF independent of other co-variables.

CONCLUSIONS

(1) Patients with vagal AF are younger, and invariably have paroxysmal lone AF. (2) SAPW is normal and significantly shorter in vagal AF when compared to patients with nonvagal AF. (3) This suggests that those in the vagal AF population have normal intraatrial conduction, which has implications for AF ablation in these patients.