Novel approaches to mechanism-based atrial fibrillation ablation.

Modern cardiac electrophysiology has reported significant advances in the understanding of mechanisms underlying complex wave propagation patterns during atrial fibrillation (AF), although disagreements remain. One school of thought adheres to the long-held postulate that AF is the result of randomly propagating wavelets that wonder throughout the atria. Another school supports the notion that AF is deterministic in that it depends on a small number of high-frequency rotors generating three-dimensional scroll waves that propagate throughout the atria.

Long-term follow-up of right atrial ablation in patients with atrial fibrillation:

Introduction: The aim of this study was to evaluate the efficacy and the impact on quality of life of a new ablative approach to the right atrium in patients with atrial fibrillation (AF).

Methods And Results: Seventy-four symptomatic patients with paroxysmal (n = 49) or permanent (n = 25) refractory AF underwent radiofrequency ablation. A nonfluoroscopic electroanatomic mapping system was used to perform the following lesions: (1) an isthmus line between the tricuspid annulus and the inferior vena cava; (2) a posterior intercaval line from the superior vena cava and the inferior vena cava; (3) a septal line from the superior vena cava to the fossa ovalis, proceeding to the coronary sinus ostium where a circumferential line around the ostium was performed, and then on to the inferior vena cava; and (4) a transversal lesion connecting the posterior intercaval and the septal lesions.

Catheter ablation of paroxysmal atrial fibrillation using a 3D mapping system.

Background: We treated paroxysmal recurrent atrial fibrillation (AF) with radiofrequency (RF) catheter ablation by creating long linear lesions in the atria. To achieve line continuity, a 3D electroanatomic nonfluoroscopic mapping system was used.

Methods And Results: In 27 patients with recurrent AF, a catheter incorporating a passive magnetic field sensor was navigated in both atria to construct a 3D activation map.

Atrial linear ablations in pigs. Chronic effects on atrial electrophysiology and pathology.

Background: Generation of long and continuous linear ablations is required in a growing number of atrial arrhythmias. However, deployment and assessment of these lesions may be difficult, and there are few data regarding their short- and long-term effects on atrial electrophysiology and pathology.

Methods And Results: A nonfluoroscopic mapping and navigation technique was used to generate 3-dimensional (3D) electroanatomic maps of the right atrium in 8 pigs.

Renal response of euryhaline toad (Bufo viridis) to acute immersion in tap water, NaCl, or urea solutions.

Green toads (Bufo viridis) were acclimated to either tap water, 230 mOsmol NaCl kg-1 H2O (saline), 500 mOsmol NaCl kg-1 H2O (high saline), or 500 mmol L-1 urea. Renal functions for each acclimation group were studied on conscious animals that had one ureter chronically catheterized. Reciprocal immersion of tap-water- and saline-acclimated toads in the opposite solution did not stress the animals osmotically, and plasma osmolality increased or decreased by no more than 15%.

Electromechanical characterization of chronic myocardial infarction in the canine coronary occlusion model.

Background: Defining the presence, extent, and nature of the dysfunctional myocardial tissue remains a cornerstone in diagnostic cardiology. A nonfluoroscopic, catheter-based mapping technique that can spatially associate endocardial mechanical and electrical data was used to quantify electromechanical changes in the canine chronic infarction model.

Methods And Results: We mapped the left ventricular (LV) electromechanical regional properties in 11 dogs with chronic infarction (4 weeks after LAD ligation) and 6 controls.

Effect of alpha-ketoglutarate on organic anion transport in single rabbit renal proximal tubules.

The effect of exogenous alpha-ketoglutarate (alpha KG) and the peritubular Na(+)-dicarboxylate (Na-DC) cotransporter on organic anion/dicarboxylate (OA/DC) exchange in S2 segments of single, nonperfused rabbit proximal tubules was measured using 1 microM fluorescein (FL), a model OA, and epifluorescence microscopy. The effect of different transmembrane distributions of 10 microM alpha KG on peritubular FL uptake was measured at 37 degrees C using bicarbonate-buffered, nutrient-containing buffers, which are conditions similar to those found in vivo. Compared with FL uptake in the absence of exogenous alpha KG, preloading tubules with alpha KG (trans-configuration) or acute exposure to alpha KG (cis-configuration) increased FL uptake 62% and 54%, respectively, whereas a cis-trans-configuration of alpha KG increased FL uptake by 76%.

Hemodynamic evaluation of the heart with a nonfluoroscopic electromechanical mapping technique.

Background: Clinical cardiac volumetric measurement techniques are essential for assessing cardiac performance but produce significant inaccuracies in extrapolation of the volume of a three-dimensional (3D) object from two-dimensional images and lack the ability to associate cardiac electrical and mechanical activities. In this study, we tested the accuracy of cardiac volumetric measurements using a new catheter-based system.

Methods And Results: The system uses magnetic technology to accurately locate a special catheter at a frequency of 125 Hz and is currently used in the field of electrophysiology, in which activation maps are superimposed on the 3D geometry of the cardiac chamber.

Guidance of radiofrequency endocardial ablation with real-time three-dimensional magnetic navigation system.

Background: Ablation therapy for certain arrhythmias requires the formation of complex lesions based on electrical and anatomic mapping. We tested the accuracy and reproducibility of a nonfluoroscopic mapping and navigation (NFM) system to guide delivery of radiofrequency (RF) energy in the right atrium (RA) of swine.

Methods And Results: The NFM system uses an ultralow magnetic field to measure the real-time three-dimensional (3D) location of the tip of the locatable catheter.

Interaction of alpha-KG with basolateral organic anion transporter in isolated rabbit renal S3 proximal tubules.

To understand the basolateral p-aminohippurate (PAH) transporter in the S3 segment of rabbit proximal tubules and its relationship to the transporter in the S2 segment, we measured the 30-s uptake and efflux of PAH across the basolateral membrane of single isolated S3 segments at 37 degrees C in bicarbonate-buffered media. Kinetic analysis of uptake data revealed a concentration of PAH at one-half Jmax of approximately 107 microM (same as in the S2 segment) but a Jmax of 600 fmol.min-1.

Renal function at steady state in a toad (Bufo viridis) acclimated in hyperosmotic NaCl and urea solutions.

Kidney function of the euryhaline toad Bufo viridis was studied in animals acclimated to tap water and solutions of NaCl (230 and 500 mosmol.kg-1 H2O) and urea (500 mmol.l-1) in steady-state conditions.

Anuran amphibia which are not acclimable to high salt, tolerate high plasma urea.

1. The capacity of five anuran Amphibians (Bufo viridis, B. regularis, Rana ridibunda, Hyla arborea and Pelobates syriacus) to acclimate to NaCl and urea solutions was investigated.

Urea transport across urinary bladder and salt acclimation in toad (Bufo viridis).

The fluxes of urea across the urinary bladder of the toad Bufo viridis have been studied under conditions of acclimation to tap water or 500 mosM NaCl solution. The [14C]urea fluxes were measured simultaneously with [3H]inulin to test for nonspecific leakage. The fluxes are quite high (Ktrans = 75 x 10(-7) cm/s at 5 mmol/l urea) and are similar in either the mucosal-to-serosal or the opposite direction.

Saturable urea transport pathway across the urinary bladder of Bufo viridis and salt acclimation.

Urea fluxes across the urinary bladder of Bufo viridis were studied in vitro after modification of the mounting technique. The fluxes increased as a function of the bath urea concentration, saturating near 200 mmol/l. The apparent Km was 88 mmol/l in the bladders from tapwater-acclimated toads, and 107 mmol/l in toads acclimated to 500 mOsm NaCl.