Atrial fibrillation: A never ending story?

Atrial fibrillation (AF) often recurs after ablative therapy. In our patient, intraoperative epicardial mapping during therapy- resistant AF revealed highly dissociated atrial conduction patterns and that long lines of conduction block throughout the entire atria. Given the extensiveness of the substrate, it is not surprising that ablations were not successful. Conduction patterns during therapy-resistant atrial fibrillation (AF) are highly dissociated and show long lines of conduction block. As long as the presence and extensiveness of the arrhythmogenic substrate underlying AF remains poorly understood and cannot be evaluated in the individual patient, none of the present available antiarrhythmic treatment modalities will be effective

The Impact of Filter Settings on Morphology of Unipolar Fibrillation Potentials

Using unipolar atrial electrogram morphology as guidance for ablative therapy is regaining interest. Although standardly used in clinical practice during ablative therapy, the impact of filter settings on morphology of unipolar AF potentials is unknown. Thirty different filters were applied to 2,557,045 high-resolution epicardial AF potentials recorded from ten patients. Deflections with slope ≤ − 0.05 mV/ms and amplitude ≥ 0.3 mV were marked. High-pass filtering decreased the number of detected potentials, deflection amplitude, and percentage of fractionated potentials (≥ 2 deflections) as well as fractionation delay time (FDT) and increased percentage of single potentials. Low-pass filtering decreased the number of potentials, percentage of fractionated potentials, whereas deflection amplitude, percentage of single potentials, and FDT increased. Notch filtering (50 Hz) decreased the number of potentials and deflection amplitude, whereas the percentage of complex fractionated potentials (≥ 3 deflections) increased. Filtering significantly impacted morphology of unipolar fibrillation potentials, becoming a potential source of error in identification of ablative targets.

Intraoperative Inducibility of Atrial Fibrillation Does Not Predict Early Postoperative Atrial Fibrillation

Background Early postoperative atrial fibrillation ( EP o AF ) is associated with thromboembolic events, prolonged hospitalization, and development of late Po AF ( LP o AF ). It is, however, unknown if EP o AF can be predicted by intraoperative AF inducibility. The aims of this study are therefore to explore (1) the value of intraoperative inducibility of AF for development of both EP o AF and LP o AF and (2) the predictive value of de novo EP o AF for recurrence of LP o AF . Methods and Results Patients (N=496, 75% male) undergoing cardiothoracic surgery for coronary and/or valvular heart disease were included. AF induction was attempted by atrial pacing, before extracorporeal circulation. All patients were on continuous rhythm monitoring until discharge to detect EP o AF . During a follow‐up period of 2 years, LP o AF was detected by ECG s and Holter recordings. Sustained AF was inducible in 56% of patients. There was no difference in patients with or without AF before surgery ( P =0.159), or between different types of surgery ( P =0.687). In patients without a history of AF , incidence of EP o AF and LP o AF was 37% and 2%, respectively. EP o AF recurred in 58% patients with preoperative AF , 53% developed LP o AF . There were no correlations between intraoperative inducibility and EP o AF or LP o AF ( P &gt;0.05). EP o AF was not correlated with LP o AF in patients without a history of AF ( P =0.116), in contrast to patients with AF before surgery ( P &lt;0.001). Conclusions Intraoperative AF inducibility does not predict development of either EP o AF or LP o AF . In patients with AF before surgery, EP o AF is correlated with LP o AF recurrences. This correlation is absent in patients without AF before surgery. </jats:sec

Heterogeneity in Conduction Underlies Obesity-Related Atrial Fibrillation Vulnerability

BACKGROUND: Obese patients are more vulnerable to development of atrial fibrillation but pathophysiology underlying this relation is only partly understood. The aim of this study is to compare the severity and extensiveness of conduction disorders between obese patients and nonobese patients measured at a high-resolution scale. METHODS: Patients (N=212) undergoing cardiac surgery (male:161, 63±11 years) underwent epicardial mapping of the right atrium, Bachmann bundle, and left atrium during sinus rhythm. Conduction delay (CD) was defined as interelectrode conduction time of 7 to 11 ms and conduction block (CB) as conduction time ≥12 ms. Prevalence of CD/CB, continuous CDCB (cCDCB), length of CD/CB/cCDCB lines, and severity of CB were analyzed. RESULTS: In obese patients, the overall incidence of CD (3.1% versus 2.6%; P=0

Impact of ischemic and valvular heart disease on atrial excitation

Background--The influence of underlying heart disease or presence of atrial fibrillation (AF) on atrial excitation during sinus rhythm (SR) is unknown. We investigated atrial activation patterns and total activation times of the entire atrial epicardial surface during SR in patients with ischemic and/or valvular heart disease with or without AF. Methods and Results--Intraoperative epicardial mapping (N=128/192 electrodes, interelectrode distances: 2 mm) of the right atrium, Bachmann's bundle (BB), left atrioventricular groove, and pulmonary vein area was performed during SR in 253 patients (186 male [74%], age 66±11 years) with ischemic heart disease (N=132, 52%) or ischemic valvular heart disease (N=121, 48%). As expected, SR origin was located at the superior intercaval region of the right atrium in 232 patients (92%). BB activation occurred via 1 wavefront from right-to-left (N=163, 64%), from the central part (N=18, 7%), or via multiple wavefronts (N=72, 28%). Left atrioventricular groove activation occurred via (1) BB: N=108, 43%; (2) pulmonary vein area: N=9, 3%; or (3) BB and pulmonary vein area: N=136, 54%; depending on which route had the shortest interatrial conduction time (P < 0.001). Ischemic valvular heart disease patients more often had central BB activation and left atrioventricular groove activation via pulmonary vein area compared with ischemic heart disease patients (N=16 [13%] versus N=2 [2%]; P=0.009 and N=86 [71%] versus N=59 [45%]; P < 0.001, respectively). Total activation times were longer in patients with AF (AF: 136±20 [92-186] ms; no AF: 114±17 [74-156] ms; P < 0.001), because of prolongation of right atrium (P=0.018) and BB conduction times (P < 0.001). Conclusions--Atrial excitation during SR is affected by underlying heart disease and AF, resulting in alternative routes for BB and left atrioventricular groove activation and prolongation of total activation times. Knowledge of atrial excitation patterns during SR and its electropathological variations, as demonstrated in this study, is essential to further unravel the pathogenesis of AF