Antegrade slow pathway mapping of typical atrioventricular nodal reentrant tachycardia based on direct slow pathway capture.

Background: Radiofrequency (RF) ablation of typical atrioventricular nodal reentrant tachycardia (tAVNRT) is performed without revealing out the location of antegrade slow pathway (ASp). In this study, we studied a new electrophysiological method of identifying the site of ASp.

Methods: This study included 19 patients.

The effect of metabolic syndrome on heart rate turbulence in non-diabetic patients.

Background: Metabolic syndrome (MetS), which includes a cluster of risk factors, is being increasingly recognized as a new risk factor for cardiovascular disease. Heart rate turbulence (HRT) is a Holter-based non-invasive method for detecting cardiac autonomic imbalance and is an independent, powerful predictor of cardiac arrhythmias and sudden cardiac death in different patient groups. This study evaluated the effect of MetS on HRT in non-diabetic patients.

Cardiac autonomic function measured by heart rate variability and turbulence in pre-hypertensive subjects.

Non-dipping blood pressure pattern was shown to be associated with increased cardiovascular events. In addition, cardiac autonomic dysfunction was found to be associated with non-dipper phenomenon. In this study, we aimed to evaluate the cardiac autonomic functions in dipper and non-dipper pre-hypertensive subjects.

Novel method to evaluate the conduction velocity and conducting area during isthmus-dependent atrial flutter.

Objective: The difference of the conduction velocity (CV) around the tricuspid valve annulus between the counter-clockwise (CCW) atrial flutter and the clockwise (CW) atrial flutter has not been well clarified. This study was undertaken to evaluate the CV and the conducting area (CA) per millisecond around the tricuspid valve annulus using the electroanatomical mapping.

Methods: The electroanatomical mapping was performed during the tachycardia for 30 consecutive patients (mean age: 61±16 years) with isthmus-dependent atrial flutter (CCW, 25; CW, 5).

Altered action potential dynamics in electrically remodeled canine atria: evidence for altered intracellular Ca2+ handling.

Background: Electrical instability following sustained rapid excitation has been attributed to altered ion channels. Alterations of Ca(2+) handling could also contribute to abnormal dynamics of action potential, favoring the initiation and perpetuation of arrhythmia.

Methods And Results: Transmembrane action potentials and twitch force (TF) were recorded from normal (n=6) and remodeled (6-week atrial pacing at 400 beats/min, n=6) canine atria.

Temporal patterns of progression and regression of electrical and mechanical remodeling of the atrium.

Objectives: We evaluated serial changes of electrical and mechanical parameters of atrial remodeling in dogs subjected to rapid atrial pacing.

Background: Prolonged rapid atrial excitation causes electrical and mechanical remodeling, which contributes to persistence of atrial fibrillation and clot formation. However, the temporal relationship between these two types of atrial remodeling remains unknown.

A comparison between calcium channel blocking drugs with different potencies for T- and L-type channels in preventing atrial electrical remodeling.

Calcium overload plays a key role in the development of atrial electrical remodeling. The effect of an L-type Ca channel blocker in preventing this remodeling has been reported to be short lasting, partly due to down-regulation of this channel and persisting Ca entry through the T-type Ca channel. To prove if efonidipine, a dual L- and T-type Ca channel blocker exerts a greater effect than an L-type Ca channel blocker verapamil, 21 dogs underwent rapid atrial pacing at 400 bpm for 14 days, pretreatment with efonidipine in 7 (E), verapamil in 7 (V), and none in 7 (C).

Oral verapamil attenuates the progression of pacing-induced electrical and mechanical remodeling of the atrium.

Background: Calcium overload plays a major role in the development of electrical and mechanical remodeling during atrial fibrillation, but the potential of verapamil, a Ca blocker, for preventing atrial electrical remodeling remains controversial.

Methods And Results: Pacing and recording electrodes were sutured to the right atrium in 16 dogs. After a 5-day recovery period, rapid atrial pacing at 400 ppm was initiated in 8 dogs (control group).

Preserved effects of potassium channel blockers in the pacing-induced remodeled canine atrium: a comparison between E4031 and azimilide.

This study was designed to evaluate the electrophysiologic effects of E4031 (a pure IKr blocker) and azimilide (AZ: a combined Ikr + IKs blocker) at various stages of atrial electrical remodeling. Twelve dogs underwent continuous rapid atrial pacing (400/min) for 14 days. The electrophysiologic study was performed on the day before as well as after 2, 7, and 14 days of rapid atrial pacing both before and after the administration of either E4031 (n = 6) or AZ (n = 6).

Daily oral verapamil before but not after rapid atrial excitation prevents electrical remodeling.

Background: Intravenous verapamil has been reported to prevent electrical remodeling induced by rapid atrial excitation of several minutes to several hours. However, the clinical efficacy of verapamil when taken orally and daily remains controversial.

Purpose: We attempted to demonstrate our hypothesis that if verapamil prevents calcium (Ca) overload, its efficacy would be greater when taken before, rather than after, the onset of rapid atrial excitation.

Density and function of inward currents in right atrial cells from chronically fibrillating canine atria.

Objective: To determine whether I(Na) and I(CaL) are altered in function/density in right atrial (RA) cells from dogs with chronic atrial fibrillation (cAF dogs, episodes lasting at least 6 days) and whether the changes that occur differ from those in dogs with nonsustained or brief episodes of fibrillation (nAF dogs).

Methods: Using whole cell voltage clamp, sodium and calcium current density and function were determined in disaggregated RA cells from nAF, cAF and control atria (Con). Ca(2+) currents were studied with either Ca(2+) or Ba(2+) as charge carrier, as well as with either EGTA or BAPTA as the internal solution Ca(2+) chelator.

Discordant temporal changes in electrophysiological properties during electrical remodeling and its recovery in the canine atrium.

Prolonged rapid atrial excitation gives rise to atrial electrical remodeling, which perpetuates atrial fibrillation (AF). However, there has been controversy regarding the nature of temporal changes in conduction characteristics during the development and recovery of electrical remodeling. This study was designed to clarify the nature of the development and recovery of electrical remodeling in relation to AF inducibility in dogs subjected to rapid atrial pacing.

Anisotropic conduction properties in canine atria analyzed by high-resolution optical mapping: preferential direction of conduction block changes from longitudinal to transverse with increasing age.

Background: Anisotropic conduction properties may provide a substrate for reentrant arrhythmias. We investigated the age-dependent changes of structural and functional anisotropy in isolated right atria from infant (1 to 2 months), young (6 to 12 months), and old (6 to 10 years) dogs.

Methods And Results: The histology of the mapped atrial tissues (a small subepicardial area, 2.