Modifications in Ventricular Fibrillation and Capture Capacity Induced by a Linear Radiofrequency Lesion

[EN] Introduction and objectives: An analysis was made of the effects of a radiofrequency-induced linear lesion during ventricular fibrillation and the capacity to capture myocardium through high-frequency pacing. Methods: Using multiple epicardial electrodes, ventricular fibrillation was recorded in 22 isolated perfused rabbit hearts, analyzing the activation maps upon applying trains of stimuli at 3 different frequencies close to that of the arrhythmia: a) at baseline; b) after radio-frequency ablation to induce a lesion of the left ventricular free wall (length=10 [1] mm), and c) after lengthening the lesion (length=23 [2] mm). Results: Following lesion induction, the regularity of the r…

Comments on “New epicardial mapping electrode with warming/cooling function for experimental electrophysiology studies” [33 (5) (2011) 653–659]

Analyzing the electrophysiological effects of local epicardial temperature in experimental studies with isolated hearts

As a result of their modulating effects upon myocardial electrophysiology, both hypo- and hyperthermia can be used to study the mechanisms that generate or sustain cardiac arrhythmias. The present study describes an original electrode developed with thick-film technology and capable of controlling regional temperature variations in the epicardium while simultaneously registering its electrical activity. In this way, it is possible to measure electrophysiological parameters of the heart at different temperatures. The results obtained with this device in a study with isolated and perfused rabbit hearts are reported. An exploration has been made of the effects of local temperature changes upon…

Simultaneous atrial and ventricular restitution and fibrillation analyses using a low-cost scalable panoramic whole-heart optical mapping configuration for whole-heart imaging of translational models

Abstract Introduction Optical mapping (OM) is the primary method for imaging electrophysiologically relevant parameters from the outer surface of Langendorff-perfused hearts. However, current panoramic OM systems are financially challenging, require multiple sensors to map wide areas of the surface with overlapping regions and missing areas of interest due to the intrinsic shape of the heart. We proposed different panoramic configurations to dynamically characterize atrial and ventricular function during arrhythmia and, in presence of a coronary occlusion. Methods We devised both a multi-sensor and a single sensor system integrated with the perfusion circuit comprising sensor elements, a co…

Dual-sided Mapping During Global Stretch Using a Custom Miniaturized Endocardial Balloon with a Multipurpose Multichannel Acquisition System for Preclinical Electrophysiological Studies

Acute regional myocardial stretch (STR) is known to induce myocardial electrophysiological modifications via mechano-electric feedback (MEF), including abnormal repolarization, premature excitation and increased complexity of activation leading to the initiation, maintenance and acceleration of arrhythmic events. Due to technical limitations little is known about intramural and endo-epicardial (ENDO-EPI) phenomena during these events. Understanding ENDO-EPI modifications produced by STR through MEF may require a dual-sided approach to simultaneously correlate macroscopic surface modifications and their independent or interconnected components. For that purpose, we optically mapped (OM) the …

Estudio experimental de los efectos de EIPA, losartán y BQ-123 sobre las modificaciones electrofisiológicas inducidas por el estiramiento miocárdico

Resumen Introduccion y objetivos Se han implicado diversos mecanismos en la respuesta mecanica al estiramiento miocardico, que incluyen la activacion del intercambiador Na+/H+ por acciones autocrinas y paracrinas. Se estudia la participacion de estos mecanismos en las respuestas electrofisiologicas al estiramiento agudo miocardico mediante el analisis de los cambios inducidos con farmacos. Metodos Se analizan las modificaciones de la fibrilacion ventricular inducidas por el estiramiento agudo miocardico en corazones de conejo aislados y perfundidos utilizando electrodos multiples epicardicos y tecnicas cartograficas. Se estudian 4 series: control (n = 9); durante la perfusion del antagonist…

Effects of chronic exercise on myocardial refractoriness: a study on isolated rabbit heart

Aim:  To determine whether chronic physical training increases atrial and ventricular refractoriness in isolated rabbit heart. Methods:  Trained rabbits were submitted to a protocol of treadmill running. The electrophysiological parameters of refractoriness investigated in an isolated heart preparation were: (1) atrial effective refractory period (AERP) and atrial functional refractory period and ventricular effective and functional refractory periods (VERP and VFRP) using the extrastimulus technique at four different pacing cycle lengths; (2) the dominant frequency (DF) of ventricular fibrillation (VF). A multi-electrode plaque containing 256 electrodes and a spectral method were used to o…

Modificaciones de la fibrilación ventricular y de la capacidad de captura inducidas por una lesión lineal con radiofrecuencia

Resumen Introduccion y objetivos Analizar los efectos, en la fibrilacion ventricular y en la capacidad de capturar al miocardio mediante estimulacion a frecuencias rapidas, de una lesion lineal producida con radiofrecuencia. Metodos En 22 corazones de conejo aislados y perfundidos, se utilizaron electrodos multiples epicardicos para registrar la fibrilacion ventricular. Se analizaron los mapas de activacion al aplicar trenes de estimulos a tres frecuencias distintas, cercanas a las de la arritmia, en tres situaciones: a) basalmente; b) tras producir con radiofrecuencia una lesion en la pared libre del ventriculo izquierdo (longitud, 10 ± 1 mm), y c) tras ampliar su extension (longitud, 23 ±…

A novel multielectrode for epicardial recording with temperature control based in Peltier cells

Electrophysiological parameters of the myocardium are influenced by temperature. Working with experimental models of isolated heart, the analysis of modulating effect exerted by local changes of temperature can provide some information about the mechanisms of certain arrhythmias and their electrophysiological bases, such as ventricular fibrillation. Conventional multiple electrodes do not seem to be appropriate, being necessary the development of specific devices. The design and implementation of a device adapted to these requirements is presented in this paper. This is a multi-electrode able to reproduce located and controlled conditions of hypothermia and hyperthermia, in a determined are…

2D Isochronal Correlation Method to Detect Pacing Capture during Ventricular Fibrillation

During ventricular fibrillation (VF), a portion of myocardial tissue can be captured by pacing at a rate near the fibrillation rate. Interruption of ventricular fibrillation can be favored by achieving stable myocardial capture, lowering the energy required for electrical cardioversion. Existence of myocardial capture during electrical stimulation is determined by visual inspection of electrograms (EGM) by an experienced observer. The objective of this work is the development of a semi-automatic method for the detection of myocardial capture based on the 2D correlation of isochronal maps. In 4 isolated rabbit hearts VF was induced by ventricular pacing with an increasing rate. An array of 1…

Efectos de la estreptomicina en las modificaciones de la activación miocárdica durante la fibrilación ventricular inducidas por el estiramiento

Se ha evaluado si las modificaciones en la activacion miocardica durante la fibrilacion ventricular producidas por el estiramiento agudo pueden ser contrarrestadas por un bloqueador de los receptores sensibles al estiramiento. En 16 corazones aislados de conejo, se ha analizado la refractariedad y la frecuencia de activacion durante la fibrilacion ventricular antes, durante y despues de producir un estiramiento agudo localizado en la pared libre del ventriculo izquierdo, en ausencia (serie A, n = 8) o en presencia (serie B, n = 8) de estreptomicina 200 μmol. Durante la perfusion de estreptomicina (serie B), tanto basalmente como durante y despues del estiramiento, la fibrilacion ventricular…

New epicardial mapping electrode with warming/cooling function for experimental electrophysiology studies

Cardiac electrical activity is influenced by temperature. In experimental models, the induction of hypothermia and/or hyperthermia has been used for the study of mechanisms of cardiac arrhythmia. A system that allows for localized, controlled induction, besides simultaneously recording electrical activity in the same induced area, needs to be developed ad hoc. This article describes the construction and application of a new system capable of locally modifying the epicardial temperature of isolated hearts and of carrying out cardiac mapping with sufficient spatial resolution. The system is based on a thermoelectric refrigerator and an array of 128 stainless steel unipolar electrodes in encap…

Experimental study on the effects of physical training on the defibrillation threshold

Background: Chest compression artifacts during cardiopulmonary resuscitation (CPR) deteriorate the rhythm diagnosis of automated external defibrillators (AED). Cardiopulmonary resuscitation must therefore be interrupted for a reliable shock/no-shock decision. However, these hands-off intervals adversely affect the defibrillation success, and, in addition, pauses in chest compressions compromise circulation. An accurate diagnosis of the rhythmwhile performing CPR is therefore needed to minimize these hands-off intervals. Methods: The characteristics of the CPR artifact are very variable, and the artifact presents an important spectral overlap with human cardiac arrest rhythms. Consequently, …

A Single-sensor High-resolution Panoramic Optical Mapping Configuration for Simultaneous Non-overlapped Complete Atrial and Ventricular Parametric Imaging

Nowadays optical mapping (OM) is the primary method for imaging electrophysiologically relevant parameters from the outer surface of Langendorff-perfused hearts. This technique has become essential for comprehensively understanding mechanisms of cardiac propagation during physiological activation, arrhythmia, and therapeutic antiarrhythmic interventions in translational hearts. Panoramic whole heart optical mapping systems, using either multiple cameras, plane mirrors or a combination of both, have been developed to overcome intrinsic visualization limitations to traditional single-sensor designs. However current panoramic OM systems are financially challenging for physiology and engineerin…

Heterogeneidades inducidas en el intervalo QT mediante enfriamiento/calentamiento epicárdico local. Estudio experimental

Resumen Introduccion y objetivos La duracion anormal del intervalo QT o su dispersion se han asociado con un incremento en el riesgo de arritmias ventriculares. Se analiza el posible efecto arritmogenico de sus variaciones inducidas mediante enfriamiento y calentamiento local epicardico. Metodos En 10 corazones aislados de conejo, se modifico escalonadamente la temperatura de una region epicardica del ventriculo izquierdo (22 a 42 ° C ), registrando simultaneamente los electrogramas en dicha zona y en otra del mismo ventriculo. En ritmo sinusal, se determino el QT y el intervalo de recuperacion de la activacion y, mediante estimulacion programada, la velocidad de conduccion y la induccion d…

Effect of Streptomycin on Stretch-Induced Change in Myocardial Activation During Ventricular Fibrillation

The aim of this study was to determine whether the changes in myocardial activation pattern resulting from acute stretching during ventricular fibrillation can be counteracted by administering a compound that blocks receptors sensitive to stretch. The study involved 16 isolated rabbit hearts, in which refractoriness and activation frequency during ventricular fibrillation were measured before, during and after localized acute stretching of the left ventricular free wall, either without (series A, n=8) or with (series B, n=8) the presence of streptomycin, 200 micromol. At baseline and during and after stretching, ventricular fibrillation was slower with streptomycin perfusion in series B tha…

Experimental Study of the Effects of EIPA, Losartan, and BQ-123 on Electrophysiological Changes Induced by Myocardial Stretch

[ES] Introducción y objetivos Se han implicado diversos mecanismos en la respuesta mecánica al estiramiento miocárdico, que incluyen la activación del intercambiador Na+/H+ por acciones autocrinas y paracrinas. Se estudia la participación de estos mecanismos en las respuestas electrofisiológicas al estiramiento agudo miocárdico mediante el análisis de los cambios inducidos con fármacos. Métodos Se analizan las modificaciones de la fibrilación ventricular inducidas por el estiramiento agudo miocárdico en corazones de conejo aislados y perfundidos utilizando electrodos múltiples epicárdicos y técnicas cartográficas. Se estudian 4 series: control (n = 9); durante la perfusión del antagonista d…

Epicardial-limited electrophysiological heterogeneities do not facilitate ventricular arrhythmia induction. An experimental study

The electrophysiological heterogeneities of the myocardium are associated with vulnerability to arrhythmias. This study presents an experimental heterogeneity model based on local epicardial cooling/warming.

P315Study of the induction and characteristics of ventricular fibrillation in an experimental model of metabolic syndrome

QT interval heterogeneities induced through local epicardial warming/cooling. An experimental study

[EN] ntroduction and objectives Abnormal QT interval durations and dispersions have been associated with increased risk of ventricular arrhythmias. The present study examines the possible arrhythmogenic effect of inducing QT interval variations through local epicardial cooling and warming. Methods In 10 isolated rabbit hearts, the temperatures of epicardial regions of the left ventricle were modified in a stepwise manner (from 22 °C to 42 °C) with simultaneous electrogram recording in these regions and in others of the same ventricle. QT and activation-recovery intervals were determined during sinus rhythm, whereas conduction velocity and ventricular arrhythmia induction were determined dur…