Dr Paul Wang:                   Welcome to the monthly podcast, On the Beat, for Circulation: Arrhythmia and Electrophysiology. I'm Dr Paul Wang, Editor-in-Chief, with some of the key highlights from this month's issue.

                                                In our first paper, Mark McCauley, Flavia Vitale and associates report that carbon nanotube fibers may improve impaired myocardial conduction. In three sheep, radiofrequency ablation was used to create epicardial conduction delay. In addition, in a rodent model, carbon nanotube fibers were sewn across the atrial ventricular junction. They demonstrated acute ventricular preexcitation, but in chronic studies at four weeks, atrial pacing was required for resumption of AV conduction. Carbon nanotube fibers are conductive, biocompatible with no gross or histopathological evidence of toxicity.

                                                In our next paper, Koichiro Ejima and associates compared outcomes of circumferential pulmonary vein isolation for atrial fibrillation ablation randomized to contact force monitoring or unipolar signal modification in 136 patients with paroxysmal atrial fibrillation. In the unipolar signal modification-guided group, each radiofrequency application was delivered until the development of completely positive unipolar electrograms. In the contact force monitoring-guided group, a contact force of 20 grams, ranged 10 to 30 grams, and a minimum force time integral of 400 gram seconds were the targets for each radiofrequency application. The freedom from atrial tachyarrhythmia recurrence at 12 months was 85% in the unipolar signal modification-guided group and 70% in the contact force monitoring-guided group, P equals 0.031. The radiofrequency time for pulmonary vein isolation was shorter in the unipolar signal modification-guided group than contact force monitoring-guided group, but was not statistically significant, P equals 0.077. The incidence of time-dependent in ATP-provoked early electrical reconnections between the left atrium and pulmonary veins, procedural time, fluoroscopic time, and average force-time integral did not significantly differ between the two groups.

                                                In our next paper, Vishal Luther and associates tested whether ripple mapping is superior to conventional annotation-based local activation time mapping for atrial tachycardia diagnosis. Patients with atrial tachycardia were randomized, either ripple mapping or local activation time mapping. The primary endpoint was atrial tachycardia termination with delivery of the planned ablation lesion set. The inability to terminate atrial tachycardia with the first lesion set, the use of more than one entrainment maneuver, or the need to cross over to the other mapping arm were defined as failure to achieve the primary endpoint. The primary endpoint occurred in 38 of 42 patients or 90% in the ripple mapping group, and 29 of 41 patients, 71%, in the local activation time mapping group, P equals 0.45. The primary endpoint was achieved without any entrainment in 31 out of 42 patients or 74% with ripple mapping, and 18 out of 41 patients or 44% with local activation time mapping, P equals 0.01. Of those patients who failed to achieve the primary endpoint, atrial tachycardia termination was achieved in 9 out of 12 patients or 75% in the local activation time mapping group following crossover to ripple mapping with entrainment, but zero out of four patients, 0%, in ripple mapping group crossing over to local activation time mapping with entrainment, P equals 0.04.

                                                In our next paper, Franziska Fochler and associates examined whether anatomical targeting of late gadolinium enhancement MRI-detected gaps and superficial atrial scar is feasible and effective to treat recurrent atrial arrhythmias post-atrial fibrillation ablation. The authors studied 102 patients who underwent initial atrial fibrillation ablation and repeat ablation for recurrent atrial arrhythmias within one-year. 46 patients or 45% with atrial fibrillation recurrence were assigned to group one and underwent fibrosis homogenization as the second procedure. 56 patients or 55% with atrial tachycardia recurrence were assigned to group two and underwent late gadolinium enhancement MRI detected scar-based dechanneling. Both groups underwent re-isolation of pulmonary veins, if necessary.

                                                In the first 25 patients from group two, the atrial tachycardia was electroanatomically mapped and a critical isthmus was defined. It was found that those isthmi were located in the regions with non-transmural scarring detected by late gadolinium enhancement MRI. In the last 31 patients from group 2, an empirical late gadolinium enhancement MRI-based dechanneling was performed solely based on late gadolinium enhancement MRI results. During one-year follow-up after the second ablation, 67% of patients group one and 64% of patients group two were free from occurrence. In group two, 64% in the electroanatomic-guided and 65% in the late gadolinium enhancement MRI dechanneling group were free from recurrence. The authors concluded that homogenization of existing scar is appropriate treatment for recurrent atrial fibrillation while dechanneling of existing isthmi seem the appropriate approach for patients recurring with atrial tachycardia.

                                                In our next paper, George Leef, Fatemah Shenasa, Neal Bhatia and associates examined whether wave front field mapping of persistent atrial fibrillation can reveal an underlying network of a small number of spatially anchored rotational and focal sites. They examined unipolar atrial fibrillation electrograms from 64-pole baskets in 54 patients from an international registry in whom persistent atrial fibrillation was terminated by targeted ablation. They identified 4.0, plus or minus 2.1, spatially anchored rotational focal sites in atrial fibrillation that were a single in seven patients type I or paired chiral-antichiral type II rotational drivers that controlled most of the atrial area. Ablation of one or two large drivers terminated all cases of these types of atrial fibrillation. Third, interaction of three to five drivers type III, n equals 42, was present with changing areas of control. Targeted ablation at driver center terminate atrial fibrillation and required more ablation in type III versus I, P equals 0.02 in the left atrium.

                                                In our next paper, Ryan Azarrafiy and associates examined survival after superior vena cava tear using an endovascular balloon. Data were prospectively collected from both a United States Food and Drug Administration-maintained database and physician reports of adverse events as they occurred. Confirmed superior vena cava tears were analyzed for patient demographics, case details, and index hospitalization mortality. Over a period of two years, 116 confirmed superior vena cava events were identified, of which 44% involve proper balloon use and 50% involve no use or improper use. When an endovascular balloon was properly used, 45 of 51 patients, or 88.2%, survived in comparison to 37 out of 65, or 56.9%, when a balloon was not used or improperly used; P equals 0.0002. Furthermore, multivariate regression modeling found that proper balloon deployment was an independent, negative predictor of in-hospital mortality for patients who experienced a superior vena cava laceration, odds ratio of 0.13; P value less than 0.001.

                                                In our next paper, Bharatraj Banavalikar and associates examined 28 patients with focal atrial tachycardia, mean age 34.6 years, females 60.7%, were included in the study. Most common symptoms were palpitations, 85.7%, followed by shortness of breath, 25%. The mean atrial tachycardia rate was 170 beats per minute and mean left ventricular ejection fraction was 54.7%. Overall, 18 or 64.3% patients responded within six hours of the first dose of ivabradine; 13 out of the 18 ivabradine responders subsequently underwent catheter ablation. Focal atrial tachycardia originating in the atrial appendages was a predictor of ivabradine response compared with those arising from other atrial sites, P equals 0.46.

                                                In our next paper, Takumi Yamada and associates studied 26 consecutive patients with idiopathic origins that were identified at the left ventricular summit. The authors studied 26 consecutive patients with idiopathic left ventricular summit ventricular arrhythmias in the basal and apical left ventricular summit in 15 and 11 patients, respectively. Radiofrequency ablation of the apical left ventricular summit ventricular arrhythmias were successful in the great cardiac vein in nine patients and in the apical left ventricular outflow tract in two. Ablation of the basal left ventricular summit was successful in the aortomitral continuity in nine patients, at the junction of the left and right coronary cusp in 4 and the left coronary cusp in two. Three apical left ventricular summit ventricular arrhythmias exhibited an eccentric endocardial pattern that was from basal to apical left ventricular outflow tract. In 11 basal left ventricular summit ventricular arrhythmias, the activation pattern was eccentric because ventricular activation within the great cardiac vein in the apical left ventricular summit was earlier than that in the basal left ventricular outflow tract. In two left ventricular summit ventricular arrhythmias, the activation was eccentric because a relatively early ventricular activation was recorded at multiple sites away from the successful ablation site. The authors concluded that eccentric activation patterns often occurred during idiopathic lef