Left Voltage Research Articles

The Efficacy of Inducibility and Circumferential Ablation with Pulmonary Vein Isolation in Patients with Paroxysmal Atrial Fibrillation

Some conflicting results of the efficacy of the inducibility test used in the catheter ablation of atrial fibrillation (AF) have been reported. The aim of this study was to investigate the inducibility and efficacy of circumferential ablation with pulmonary vein isolation (PVI) in patients with paroxysmal AF and its relationship to the atrial substrate. This study consisted of 88 patients with paroxysmal AF who underwent catheter ablation. Electroanatomic mapping using a NavX system was performed and the biatrial voltage was obtained during sinus rhythm. After successful circumferential ablation with PVI, an inducibility test was performed to determine the requirement for creating left atrial (LA) ablation line. After procedure, patients with inducible AF had a higher recurrence rate than did those with noninducibility of AF (55% vs 18%, P = 0.02). The patients with inducible AF after the PVI had a lower biatrial voltage than did those with negative inducibility. The patients with inducible AF after the final procedure who had a recurrence had a lower LA voltage (1.3 +/- 0.4 vs 1.8 +/- 0.4 mV, P = 0.02) and longer LA total activation time (99 +/- 18 vs 88 +/- 13 msec, P = 0.02) than did those with noninducible AF and no recurrence. None of the patients had occurrence of LA flutter during the follow-up. After a single procedure of circumferential ablation with PVI and noninducibility, 82% patients did not have recurrence of AF. The inducibility of AF was related to the recurrence of AF. The atrial substrate affected the outcome of the inducibility.

Progressive Remodeling of the Atrial Substrate—A Novel Finding from Consecutive Voltage Mapping in Patients with Recurrence of Atrial Fibrillation After Catheter Ablation

Atrial substrate properties have been demonstrated to be related to atrial arrhythmias. This study investigated whether the atrial substrate exhibits progressive remodeling in patients with recurrence of atrial fibrillation (AF) after catheter ablation. Fifteen consecutive AF patients (52 +/- 12 years old, 12 males) underwent the same mapping technique (NavX, St. Jude Medical, Minnetonka, MN, USA) and same ablation technique for primary AF and recurrence of AF (170 +/- 66 days after the first procedure). The bipolar mean peak-to-peak voltage (PPV) of the global left atrium during sinus rhythm significantly decreased in the second procedure (2.25 +/- 0.62 vs. 1.79 +/- 0.60 mV, P = 0.008). Also, the percentage of the surface area of the low voltage zone (LVZ; less than 0.5 mV) in the left atrium increased from 6 +/- 4% to 13 +/- 6% (P = 0.001) in the second procedure. There was no significant change in the right atrial bipolar mean PPV or surface area of the LVZ in the second procedure. Atrial substrate remodeling with a progressive decrease in the left atrial voltage was demonstrated in patients with recurrent AF.

Characteristics of Cavotricuspid Isthmus–Dependent Atrial Flutter After Left Atrial Ablation of Atrial Fibrillation

Patients who have previously undergone ablation of atrial fibrillation may experience cavotricuspid isthmus (CTI)-dependent atrial flutter during follow-up. The effects of left atrial (LA) ablation on the characteristics of CTI-dependent flutter have not been described. Fifteen patients underwent ablation of CTI-dependent flutter late after LA ablation of AF. The ECG, biatrial activation patterns, and LA voltage maps during flutter were analyzed. Thirty age- and gender-matched patients who underwent ablation of CTI-dependent flutter without prior LA ablation served as control subjects. Among the patients with prior LA ablation, mapping revealed counterclockwise activation around the tricuspid annulus in 12 of 15 patients (80%) and clockwise activation in 3 of 15 patients (20%). The flutter waves in the inferior leads were upright in 9 of the 15 patients (60%) with prior LA ablation and in none of the control subjects (P<0.001). The upright flutter waves in the inferior leads in patients with counterclockwise flutter corresponded to craniocaudal activation of the right atrial free wall. LA activation contributed little to the genesis of the flutter waves in these patients because of a significant reduction in bipolar LA voltage (0.44+/-0.20 versus 1.54+/-0.19 mV in patients with biphasic/negative flutter waves; P<0.001). CTI-dependent flutter that occurs after LA ablation of atrial fibrillation often has atypical ECG characteristics because of altered LA activation. In patients presenting with atrial flutter after LA ablation, entrainment mapping should be performed at the CTI even if the ECG is uncharacteristic of CTI-dependent flutter.