Takahiko Nagase

Characteristics and Catheter Ablation of Focal Atrial Tachycardia Originating From the Interatrial Septum

BACKGROUND Ablation of focal atrial tachycardia (AT) originating from the interatrial septum (IAS) is challenging because of its complex anatomy. METHODS We studied the electrocardiographic and electrophysiologic characteristics of focal, septal AT in seven patients who underwent successful ablation. RESULTS The site of successful ablation was at the site of earliest activation on the right side of the IAS in three patients and on the left side in four patients, >1cm away from the centre of the fossa ovalis in the septum secundum. A negative or +/- versus a positive or -/+ P wave in lead V1 during AT accurately predicted a right- versus left-sided origin of the AT, respectively. In the four left septal AT cases, right atrial activation mapping opposite the site of successful ablation revealed the presence of a small, low-frequency potential followed by a larger, high-frequency potential. In contrast, a high-frequency potential was not preceded by a low-frequency potential in the three right septal AT cases. CONCLUSIONS Septal AT may originate from either side of the septum secundum. The P wave polarity in lead V1 accurately predicted the side of the IAS that the AT originated from. Left septal AT is characterised by the recording of double potentials reflecting far-field activation of the left-sided IAS, followed by near-field activation of the right-sided IAS, when recording from its right side, opposite the AT origin. These observations are particularly relevant when mapping an apparent right septal AT.

The influence of the electrodes spacing of a mapping catheter on the atrial voltage substrate map

BACKGROUND Detailed substrate mapping is important for catheter ablation. However, the influence of the electrode spacing of the mapping catheter on the substrate map has not been well clarified. The aim of this study was to investigate the influence of the electrode spacing of the mapping catheter on the voltage of the substrate map. METHODS Protocol 1: We recorded the local atrial potentials of the left atrium (LA) using the ablation catheter during sinus rhythm in six atrial fibrillation (AF) patients. The voltage of each atrial potential was compared between a close-bipolar (1-2 electrode) recording and wide-bipolar (1-4 electrode) recording. Protocol 2: Two voltage-maps of the LA were constructed separately using a 20-pole circular catheter and 10-pole circular catheter during sinus rhythm in 42 AF patients. The low voltage zone (LVZ) (<0.5mV) areas obtained by 2 voltage maps using the 10-pole and 20-pole circular catheters were compared. RESULTS Protocol 1: The close-bipolar voltage of the local potentials was significantly smaller than that of the wide-bipolar voltages (0.76±0.39mV vs. 0.63±0.41mV, p<0.0001). Protocol 2: The size of the LVZ areas identified by the 10-pole and 20-pole catheters was 1.12±1.92cm2 (1.47±2.78%) and 8.30±7.80cm2 (8.83±8.32%), respectively (p<0.0001). CONCLUSIONS The voltage of the local atrial potential using the close-bipolar catheter was significantly smaller than that using the wide-bipolar catheter. Care should be given to the electrode spacing of mapping catheters when analyzing the voltage of the atrial myocardial potentials.

Analysis of the heart rate variability during cryoballoon ablation of atrial fibrillation

Aims Vagal responses such as marked bradycardia or a rapid blood pressure decrease are often observed during pulmonary vein (PV) isolation of atrial fibrillation (AF) using a cryoballoon (CB). However, the relationship between the marked vagal response and change in the heart rate variability (HRV) as a marker of the autonomic tone is not well understood. Methods and results Fifty-four paroxysmal AF patients underwent CB ablation. The CB ablation was started from the right sided PVs in 25 patients (R group) and left sided PVs in 29 (L group). The HRV and haemodynamic status during the procedure were analysed. A vagal response was observed in 16 L group patients (61.5%) during the ablation of the different PVs (RSPV:1, RIPV:5, LSPV:15, LIPV:5), while it was observed in only 2 R group patients (9.5%) (RSPV:0, RIPV:0, LSPV:1, LIPV:1) (P = 0.0002). The HRV in the L group was significantly higher than that in the R group just after the CB ablation especially for the left sided PVs (L group vs. R group, total power of the HRV, median; RSPV, 11184.7 vs. 4360.0, P = 0.21; RIPV, 9044.3 vs. 2115.1, P = 0.01; LSPV, 21186.0 vs. 1314.2, P = 0.0002; LIPV 10265.9 vs. 1236.2, P = 0.0007). Conclusion A marked increase in the HRV parameters was observed just after the CB ablation. An initial CB ablation of the right PVs decreased the change in the autonomic tone during the right PV ablation and subsequent left PV ablation. It prevented an excessive vagal response during the CB ablation and might be a safe procedure.

Low Risk of Pulmonary Vein Stenosis After Contemporary Atrial Fibrillation Ablation ― Lessons From Repeat Procedures After Radiofrequency Current, Cryoballoon, and Laser Balloon ―

BACKGROUND The incidence of pulmonary vein stenosis (PVS) after AF ablation following contemporary procedures remains unclear. We compared the incidence of PVS/narrowing (PVS/N) after PV isolation (PVI) for (1) 3-D mapping-guided wide-area encircling irrigated radiofrequency current (RFC) ablation; (2) first-third-generation big cryoballoon (CB1-3) ablation; and (3) laser balloon (LB) ablation.Methods and Results:All patients undergoing a second procedure between January 2012 and November 2016 were subgrouped according to index ablation (PVI): RFC; CB; or LB. PVS/N was classified using PV diameter ratio (second/index procedure) on selective PV angiogram performed before ablation: mild, 25-49%; moderate, 50-74%; or severe, ≥75%. A total of 344 patients (1,362 PV) were analyzed (RFC, n=211; 840 PV; CB1, n=21; 82 PV; CB2,3, n=64; 250 PV; LB, n=48; 190 PV). In the LB group, 45 patients (94%) were treated with dose ≥8.5 W. Second procedures were performed on average 14.9±14.1 months after the index procedure. Mild PVS/N was observed in 18.4%, 9.5% and 3.6% of PV in the LB, RFC and CB groups, respectively (P<0.01). Moderate PVS was recognized in 2 PV (0.1%; RFC, LB). Severe PVS was never observed, and no PV intervention/surgery was required. CONCLUSIONS The risk for significant PVS is low after RFC/CB. The incidence of mild PVS/N was highest after standard-dose LB ablation and lowest after high-dose CB ablation.

AF Sustained in Only a Small Area of SVC

A 66-year-old female was admitted to our hospital to undergo catheter ablation for symptomatic paroxysmal atrial fibrillation (AF). After pulmonary vein isolation was achieved by cryoballoon and adenosine triphosphate was injected to confirm the dormant conduction of the pulmonary veins, AF was induced. Sinus rhythm was restored by cardioversion, whereas AF was sustained only in the superior vena cava (SVC) (Picture 1 and 2). Mapping under a 3D mapping system revealed that AF was sustained in only a very small area of SVC (13.6 cm) (Picture 3 and 4). All ar-