Endocardial impedance mapping during circumferential pulmonary vein ablation of atrial fibrillation differentiates between atrial and venous tissue.

BACKGROUND: Circumferential pulmonary vein ablation (CPVA) is an effective treatment for atrial fibrillation (AF). Accurate left atrial (LA) mapping is essential for creating lesions at the LA-pulmonary vein (PV) junction, avoiding PV stenosis. OBJECTIVES: The purpose of this study was to establish whether endocardial impedance varies within the LA and PVs and whether it is a useful tool for mapping and ablation. METHODS: Pilot Phase: Three-dimensional LA maps were created using CARTO. Impedance (Z) was measured using a radiofrequency generator at multiple points in the LA, PV ostia (PVO), and deep PVs in 79 patients undergoing their first AF ablation (group 1) and 29 patients undergoing repeat CPVA (group 2). Prospective Phase: In an additional 20 patients, using pilot phase data, one operator defined catheter tip location as either LA or PVO based on CARTO and fluoroscopy. A second operator blinded to CARTO simultaneously did the same based on impedance at 15 +/- 4 points per patient. RESULTS: Group 1: Z(LA) was 99.4 +/- 9.0 omega. Z(PVO) was higher (109.2 +/- 8.5 omega), rising further as the catheter advanced into deep PV (137 omega +/- 18). Z(PVO) differed from Z(LA) by 9 +/- 4 omega. Group 2 had a lower Z(LA) and Z(PVO) compared with group 1 (P <.05). Impedance monitoring differentiated between LA and PVO, with 91% specificity and sensitivity, 96% positive predictive value, and 81% negative predictive value. At 3-month follow-up, no patients had evidence of PV stenosis on magnetic resonance imaging. CONCLUSION: Impedance mapping reliably identifies the LA-PV transitional zone, facilitating AF ablation, and its use is associated with a low incidence of PV stenosis.

Left atrial tachycardia after circumferential pulmonary vein ablation for atrial fibrillation: electroanatomic characterization and treatment.

OBJECTIVES: The purpose of this study was to evaluate the electroanatomic characteristics of left atrial tachycardia (AT) in a series of patients who underwent circumferential pulmonary vein ablation (CPVA) and to describe the ablation strategy and clinical outcome. BACKGROUND: Circumferential pulmonary vein ablation is an effective treatment for atrial fibrillation. A potential midterm complication is the development of left AT. There are only isolated reports describing mapping and ablation of such arrhythmias. METHODS: Thirteen patients (age 57.4 +/- 8.9 years, five female) underwent mapping and ablation of 14 left ATs via an electroanatomic mapping system a mean of 2.6 +/- 1.6 months after CPVA. RESULTS: Three patients were characterized as having focal AT (cycle length: 266 +/- 35.9 ms). Of 11 macro-re-entrant tachycardias studied in the remaining 10 patients (cycle length: 275 +/- 75 ms), 5 showed single-loop and 6 dual-loop circuits. Re-entrant circuits used the mitral isthmus, the posterior wall, or gaps on previous encircling lines. Such gaps and all three foci occurred anterior to the left superior pulmonary vein or at the septal aspect of the right pulmonary veins. Thirteen of 14 tachycardias (93%) were successfully ablated. CONCLUSIONS: Left AT after CPVA can be due to a macro-re-entrant or focal mechanism. Re-entry occurs most commonly across the mitral isthmus, the posterior wall, or gaps on previous ablation lines. Such gaps and foci occur most commonly at the anterior aspect of the left superior pulmonary vein and at the septal aspect of the right pulmonary veins. These arrhythmias can be successfully mapped and ablated with an electroanatomic mapping system.

Abnormalities of the repolarization characteristics of patients with heart failure progress with symptom severity.

BACKGROUND: Congestive heart failure is a common condition with high mortality. Many of these deaths are sudden and unexpected. Ventricular action potential, surface repolarization (QT interval), and dispersion of repolarization are prolonged in the failing heart, contributing to arrhythmogenesis and sudden death. We studied the relationship between QT and heart rate (RR interval) from ambulatory recordings using a novel method in patients with ischemic heart disease and varying degrees of left-ventricular impairment (IHD) and compared them to healthy subjects (HS). We compare the degree of abnormality with the functional impairment and ejection fraction. METHODS: Using a previously described automated method for continuous estimation of the QT/RR characteristic that incorporates a correction formula for compensation of QT adaptation lag (VERDA, Del Mar Reynolds Medical Ltd., Hertford, UK), we compared recordings from 41 IHD patients with age-matched HS. RESULTS: IHD Patients have prolonged 24-hour mean QTo (461 ms vs 426 ms, P < 0.01), and abnormal rate dependence relative to controls (24-hour mean slope: 0.20 vs 0.14, P < 0.001; J: 0.38 vs 0.28, P < 0.001). There is increased temporal variation in J with respect to HS. These abnormalities of repolarization increase with worsening NYHA class, but do not correlate with ejection fraction. CONCLUSIONS: The use of a universal correction formula to compare dynamic QT data in IHD patients is inappropriate. The observed progressive abnormalities may be responsible for the high incidence of sudden death through promotion of arrhythmias.