Using the initial vector from surface electrocardiogram to distinguish the site of outflow tract tachycardia.

Background: The purpose of this study is to determine whether initial vector force might best distinguish tachycardias arising from the right ventricular (RV) outflow tract (OT) versus aortic sinus cusps (ASCs).

Methods: Among 45 patients with OT tachycardia, we measured the time from the earliest QRS onset in any lead to local onset and to the first QRS peak/nadir in each surface leads during VT. We compared the earliest phase differences among patients with foci in RVOT (n = 32) and in ASCs (n = 13) (determined by ablation), using unpaired t-tests.

Reentry within the cavotricuspid isthmus: an isthmus dependent circuit.

Background: We describe a new cavotricuspid isthmus (CTI) circuit.

Methods: This study includes 8 patients referred for atrial flutter (AFL) ablation whose tachycardia circuit was confined to the septal CTI and the os of the coronary sinus (CS(OS)) region. Entrainment mapping was performed within the CTI, CS(OS), and other right atrial annular sites (tricuspid annulus (TA)).

Site specificity of transverse crista terminalis conduction in patients with atrial flutter.

Introduction: The causes of transcristal conduction (TC) in patients with atrial flutter (AFL) are unknown.

Methods And Results: In two groups of patients referred for AFL ablation, 36 had cavotricuspid isthmus (CTI) dependent flutter (Group I) and 24 had lower (n = 21) or upper loop reentry (n = 5) (Group II). After ablation, isthmus block was evaluated by pacing from the coronary sinus (CS) and low lateral right atrium and by alternative techniques, including mapping with electrodes spanning the CTI or electroanatomic mapping.

Surface electrocardiographic characteristics of right and left atrial flutter.

Background: There is little information about the surface expression of non-cavotricuspid isthmus (CTI)-dependent right atrial (RA) or left atrial (LA) flutter circuits.

Methods And Results: We retrospectively evaluated 32 episodes (in 26 patients) of atypical RA and 22 episodes (in 21 patients) of LA flutter. The surface ECG of 13 patients with lower-loop reentry was similar to that of their pattern during counterclockwise (CCW) CTI atrial flutter (AFL), except for decreased amplitude of the terminal forces in the inferior leads.

Significance of bundle branch block during atrioventricular nodal reentrant tachycardia.

There are very limited data on the effects of bundle branch block (BBB) in patients with atrioventricular nodal reentrant tachycardia (AVNRT). Studies in a total of 155 patients with 162 episodes of AVNRT were retrospectively analyzed. A total of 38 patients (25%) developed spontaneous right BBB, whereas 5 (3%) developed left BBB during tachycardia.

Optimizing the detection of bidirectional block across the flutter isthmus for patients with typical isthmus-dependent atrial flutter.

The purpose of this study was to show that multipolar electrographic recordings along the subeustachian isthmus (SI) can better differentiate slow conduction from complete isthmus block after atrial flutter ablation, leading to a lower incidence of recurrent atrial flutter (Afl). Despite the presence of various techniques to identify bidirectional conduction block (BDB) after isthmus ablation for typical Afl, several studies, including a report from a national registry, suggest that radiofrequency ablation is still associated with a 15% recurrence rate. Thus, techniques that can distinguish slow conduction from complete isthmus block have the potential for reducing long-term recurrences.

P2X7 receptor-mediated release of excitatory amino acids from astrocytes.

Astrocyte glutamate release can modulate synaptic activity and participate in brain intercellular signaling. P2X7 receptors form large ion channels when activated by ATP or other ligands. Here we show that P2X7 receptors provide a route for excitatory amino acid release from astrocytes.

Alpha(1)-adrenoceptor subtypes mediate negative inotropy in myocardium from alpha(1A/C)-knockout and wild type mice.

Cardiac alpha(1)-adrenoceptors (AR) have two predominant subtypes (alpha(1A)-AR and alpha(1B)-AR) however, their roles in regulating contraction are unclear. We determined the effects of stimulating alpha(1A)-AR (using the subtype-selective agonist A61603) and alpha(1B)-AR (using a gene knockout mouse lacking alpha(1A)-AR) separately, and together (using phenylephrine) on Ca(2+) transients, intracellular pH, and contraction of mouse cardiac trabeculae. Stimulation of alpha(1)-AR subtypes separately or together caused a triphasic contractile response.