Effects of acute reduction of temperature on ventricular fibrillation activation patterns.

Because of its electrophysiological effects, hypothermia can influence the mechanisms that intervene in the sustaining of ventricular fibrillation. We hypothesized that a rapid and profound reduction of myocardial temperature impedes the maintenance of ventricular fibrillation, leading to termination of the arrhythmia. High-resolution epicardial mapping (series 1; n = 11) and transmural recordings of ventricular activation (series 2; n = 10) were used to analyze ventricular fibrillation modification during rapid myocardial cooling in Langendorff-perfused rabbit hearts.

Mapping of atrial activation patterns after inducing contiguous radiofrequency lesions: an experimental study.

High resolution mapping techniques are used to analyze the changes in atrial activation patterns produced by contiguous RF induced lesions. In 12 Langendorff-perfused rabbit hearts, left atrial activation maps were obtained before and after RF induction of epicardial lesions following a triple-phase sequential protocol: (phase 1) three separate lesions positioned vertically in the central zone of the left atrial wall; (phase 2) the addition of two lesions located between the central lesion and the upper and lower lesions; and (phase 3) the placement of four additional lesions between those induced in the previous phases. In six additional experiments a pathological analysis of the individual RF lesions was performed.

Alteration of ventricular fibrillation by flecainide, verapamil, and sotalol: an experimental study.

Background: The purpose of this study was to determine whether the myocardial electrophysiological properties are useful for predicting changes in the ventricular fibrillatory pattern.

Methods And Results: Thirty-two Langendorff-perfused rabbit hearts were used to record ventricular fibrillatory activity with an epicardial multiple electrode. Under control conditions and after flecainide, verapamil, or d,l-sotalol, the dominant frequency (FrD), type of activation maps, conduction velocity, functional refractory period, and wavelength (WL) of excitation were determined during ventricular fibrillation (VF).

Reduction of atrial fibrillation inducibility by radiofrequency ablation: an experimental study.

Unlabelled: A study is made of the antifibrillatory effects of radiofrequency (RF)-induced atrial lesions using nine Langendorff-perfused rabbit hearts in which the atrial electrophysiological properties and atrial fibrillation (AF) inducibility were modified by atrial stretching. Using a multiple electrode consisting of 121 unipolar electrodes, determinations were made of the atrial refractory periods, conduction velocity, wavelength of the atrial activation process, and the inducibility of sustained AF episodes (duration over 30 s) by atrial burst pacing in four situations: (a) control; (b) following dilatation of the right atrium; (c) after adding an RF linear lesion at the cava-tricuspid annulus isthmus; and (d) after adding two RF linear lesions rounding the base of the right atrial appendage and extending from the inferior zone of the sulcus terminalis to the anterior wall of the appendage. Under control conditions, AF was not induced in any of the experiments.

Quantification of the modifications in the dominant frequency of ventricular fibrillation under conditions of ischemia and reperfusion: an experimental study.

The characteristics of ventricular fibrillatory signals vary as a function of the time elapsed from the onset of arrhythmia and the maneuvers used to maintain coronary perfusion. The dominant frequency (FrD) of the power spectrum of ventricular fibrillation (VF) is known to decrease after interrupting coronary perfusion, though the corresponding recovery process upon reestablishing coronary flow has not been quantified to date. With the aim of investigating the recovery of the FrD during reperfusion after a brief ischemic period, 11 isolated and perfused rabbit heart preparations were used to analyze the signals obtained with three unipolar epicardial electrodes (E1-E3) and a bipolar electrode immersed in the thermostatized organ bath (E4), following the electrical induction of VF.

Acute effects of radiofrequency ablation upon atrial conduction in proximity to the lesion site.

The electrophysiological effects of RF ablation upon the areas in proximity to the lesioned zones have not yet been well characterized. An experimental model is used to investigate atrial conduction in the boundaries of RF damaged zones. In 11 isolated and perfused rabbit hearts, endocardial atrial electrograms were recorded using an 80-lead multiple electrode positioned in the left atrium.

Are double potentials markers of a specific zone of the atrioventricular junction in the isolated rabbit heart?

A study is made of the characteristics of the atrial potentials recorded in the Koch triangle and its proximity, their variations on modifying the site of cardiac pacing, and their usefulness as markers of a distinct zone of the AV junction. In 12 isolated and perfused rabbit heart preparations an analysis was made of the endocardial atrial electrograms recorded with a multiple electrode positioned in the AV junction. The electrograms were obtained during spontaneous rhythm and on pacing at the crista terminalis (CT), interatrial septum (IAS), left atrium, and right ventricle.

Distortion product otoacoustic emissions in healthy newborns: normative data.

Distortion product otoacoustic emissions (DPOAE) offer an alternative to transiently evoked otoacoustic emissions (TEOAE) as an audiological test. The former can be used as a screening technique, and may also provide frequency-specific information about the functional state of the cochlea. We recorded DPOAE in a group of healthy newborns to establish the characteristics of a DPOAE "audiogram" (DP-gram) in this population.

Nasal mucociliary function during the menstrual cycle in healthy women.

Nasal mucociliary transport time was studied in nine healthy women over the menstrual cycle using the vegetable charcoal powder technique. Three measurements were made at different points of the cycle: during the early follicular phase, periovulatory phase and luteal phase. The mean transport times were 10.

The influence of anesthetics and vasoconstrictors on nasal mucociliary transport.

Nasal mucociliary transport time is studied in 38 healthy individuals using the charcoal dust technique, following topical application of a lidocaine solution in 10 cases, tetracaine in 11, and oxymetazoline in 17. The results show that lidocaine does not alter the transit time, whereas tetracaine increases it significantly; in turn, oxymetazoline progressively increases transit time, although this slowing is fully reversible 30 minutes after application.

Observations on variability of atrioventricular nodal conduction in man and the dual-pathway response.

A study was made of nodal conduction times of atrial stimuli with fixed coupling intervals, in 23 patients divided into two groups according to their atrial stimulus test response: Group I (continuous AV node function curve; 17 cases) and Group II (dual AV node pathway; six cases). The stimulation protocol involved the delivery of 75 stimuli with a fixed coupling interval 20 ms greater than the effective refractory period (ERP) of the AV node (Group I) or fast pathway (Group II). The atrial coupling intervals (A1A2) and node conduction times (A2H2) were measured.

Induction of partial alterations in atrioventricular conduction in dogs by percutaneous emission of high-frequency currents.

Ten anesthetized dogs were studied in an attempt to provoke partial alterations in atrioventricular (AV) conduction by high-frequency current (HFC) transcatheter ablation. A discharge power (10 to 15 W) was used for less than 5 seconds after reaching complete AV block (CAVB). The catheter was placed within an area having an A/V ratio = 1 with His bundle deflection.