Right and left atrial activation during external direct-current cardioversion shocks delivered for termination of atrial fibrillation in humans

Non-invasive atrial fibrillation organization follow-up under successive attempts of electrical cardioversion

The development of non-invasive tools able to provide valuable information about the effectiveness of a shock in external electrical cardioversion (ECV) is clinically relevant to enhance these protocols in the treatment of atrial fibrillation (AF). The present contribution analyzes the ability of a non-linear regularity index, such as sample entropy (SampEn), to follow-up non-invasively AF organization under successive attempts of ECV and to predict the effectiveness of every single shock. To this respect, the atrial activity (AA) preceding each delivered shock was extracted by using a QRST cancellation method. Next, the main atrial wave (MAW), which can be considered as the fundamental waveform associated to the AA, was obtained by applying a selective filtering centered on the dominant atrial frequency (DAF). Finally, the MAW organization was estimated with SampEn and two thresholds (Th1 = 0.1223 and Th2 = 0.0832) were established to predict the ECV outcome. Results indicated that, prior to the first attempt, all the patients who needed only one shock to restore NSR were below Th1. In addition, most of them were above Th2 in case of AF relapsing during the first month. Regarding several shocks, all the patients who maintained NSR more than one month were below Th2 after the first shock. Moreover, all the patients who relapsed to AF during the first month were between Th1 and Th2 and, finally, all the patients with ineffective ECV were above Th1. After each unsuccessful shock, a SampEn relative decrease was observed for the patients who finally reverted to NSR, but the largest variation took place after the first attempt, thus indicating that this shock plays the most important role in the procedure. Indeed, by considering jointly the patients who needed only one shock and the patients who needed several shocks, 91.67% (22 out of 24) of ECVs resulting in NSR, 93.55% (29 out of 31) of ECVs relapsing to AF during the first month and 100% (10 out of 10) of ECVs in which NSR was not restored were correctly classified. As conclusion, the MAW organization analysis via SampEn can provide useful information that could improve the effectiveness of conventional external ECV protocols used in AF treatment.

Clinical value of fibrillatory wave amplitude on surface ECG in patients with persistent atrial fibrillation

PURPOSE

We postulated that amplitude of fibrillatory (F)-wave in patients with persistent AF would correlate with clinical characteristics and outcome in patients undergoing catheter ablation for AF.

METHOD

Maximal and mean amplitude of F-waves were measured in V1 and lead II in 90 patients prior to ablation for persistent AF. F-wave amplitudes were correlated to clinical, echocardiographic variables, and outcome.

RESULTS

F-wave > or = 0.1 mV in lead II and V1 was correlated with younger age and shorter AF history, and in lead II only was correlated with a smaller left atrium. Higher F-wave amplitude at baseline predicted AF termination during ablation. Maximal amplitude of > or = 0.07 mV predicted AF termination by ablation with 82%/79% sensitivity and 68%/73% specificity in V1/lead II respectively. An association between F-wave amplitude and AF recurrence was observed. Forty-three percent of patients with mean f wave amplitude <0.05 in lead V1 had AF recurrence compared to 12% of those with F-wave > or = 0.05 (p = 0.004).

CONCLUSION

Longer AF duration, older age and larger LA size are associated with fine AF amplitude. High F-wave amplitude predicts procedural termination of arrhyhmia in patients with persistent AF and freedom from AF upon follow-up.

Atrial activation occurring immediately after successful cardioversion of atrial fibrillation

BACKGROUND AND OBJECTIVE

Electrical defibrillation is very effective in interrupting atrial fibrillation (AF). However, its mechanism is not completely understood. We report our observations in patients subjected to external electriocardioversion (ECV) of atrial fibrillation and contrast them with recent theories about defibrillation mechanism.

METHODS

In 13 consecutive patients transthoracic electrical cardioversion for AF was performed during an electrophysiological study (11 monophasic -200-360 J- and 9 biphasic shocks -50-150 J-). About 10-16 electrograms were obtained with multipolar catheters recording right atrium, coronary sinus, and right pulmonary artery. AF was defined by interelectrogram intervals and changing sequences among recordings, indicating complete lack of organization. We evaluated the presence of propagated activations immediately (<300 ms) after successful shocks (>or=1 discrete electrogram in all recordings). In unsuccessful shocks we evaluated changes in electrogram morphology (discrete/fragmented) and interelectrogram intervals before and after defibrillation.

RESULTS

About 16/20 shocks terminated AF. In 6/16 one or two cycles of atrial activation were recorded just after the shock and before AF ended. In 10/16 AF was interrupted immediately after the shock. 4/20 shocks did not interrupt the arrhythmia. After these shocks, transient organization of recorded activity with longer interelectrogram cycle length and disappearance of fragmented activity were transiently observed.

CONCLUSION

Our clinical findings in atrial defibrillation in vivo reproduce experimental data that show myocardial activations early after successful direct current shocks. These observations suggest that successful defibrillation depends not only on the immediate effects of the shock, but also on transient effects on electrophysiological properties of the myocardium, capable of interrupting persistent or reinitiated activations.

Catheter ablation of inducible atrial flutter, in combination with atrial pacing and antiarrhythmic drugs ("hybrid therapy") improves rhythm control in patients with refractory atrial fibrillation

Atrial flutter or tachycardia may coexist with atrial fibrillation [AF] and can be treated with ablation techniques in attempt to reduce the total AF burden. The role of ablation of latent atrial tachyarrhythmias elicited at electrophysiologic study in conjunction with atrial pacing and antiarrhythmic drugs in patients with refractory AF has not been evaluated. We evaluated the efficacy of catheter ablation of electrically induced atrial flutter or atrial tachycardia in improving rhythm control in patients with refractory AF.

METHODS

Consecutive patients with refractory AF, and spontaneous atrial flutter (Group 1) or without spontaneous atrial flutter (Group 2) underwent programmed stimulation in a baseline drug-free state. All patients had electrically induced atrial flutter or tachycardia. Radiofrequency ablation of the arrhythmia substrate was performed in all patients. Primary endpoints evaluated for patient outcome in both groups included maintenance of rhythm control and freedom from recurrent atrial tachyarrhythmias.

RESULTS

Forty-three patients, with a mean age of 66 +/- 13 years were studied. Group 1 consisted of 22 patients while Group 2 had 21 patients. Ablation of the tricuspid valve-inferior venacaval isthmus was performed in 41 patients who had common atrial flutter induced at electrophysiologic study. Ablation of other atrial sites was performed in 8 patients with induced atypical flutter and 4 patients with induced atrial tachycardia. Ten of these patients had ablation of more than one arrhythmia. 17 patients (40%) had atrial pacing instituted and 28 patients remained on a class 1/3 antiarrhythmic drug. During a mean follow-up of 26 +/- 14 months, 33 patients (82.5%) remained in rhythm control. Actuarial analysis showed 96% of patients in rhythm control at 6 months, 94% at 12 months, and 90% at 24 months. Freedom from symptomatic AF recurrence was 64% at 6 months, 58% at 12 months, and 42% at 24 months. The outcome for both of these endpoints was similar for Group 1 and Group 2 (p = NS). The AF free interval increased significantly from 7+/- 9 days to 172 +/- 121 days (p < 0.01) after ablation. This increase was again similar in both the groups. In the 14 patients were who did not receive atrial pacing and who remained on the same class 1/3 antiarrhythmic drug, the AF free interval increased from 18 +/- 17 days to 212+/- 102 days (p < 0.01).

CONCLUSIONS

We conclude that electrophysiologic studies can elicit latent atrial flutter or tachycardia in patients with refractory AF without spontaneous monomorphic atrial tachyarrhythmias. Catheter ablation of electrically induced atrial flutter or tachycardia either alone, or with atrial pacing and with antiarrhythmic drug may improve rhythm control and reduce AF recurrences. This is similar in patients with and without spontaneous atrial flutter and refractory AF.