Análisis tiempo-frecuencia de la fibrilación ventricular. Estudio experimental

Introduction and objectives. The analysis of frequency variability during ventricular fibrillation has yielded inconsistent results. We used an experimental model of ventricular fibrillation, with a short timescale, to analyze variations in frequency and their associated spatial distribution. Methods. Epicardial recordings of ventricular fibrillation were made in 10 perfused isolated rabbit heart preparations using a multiple electrode system (i.e., 240 unipolar electrodes). Both spectral and time-frequency analysis were used to derive the dominant frequency in the anterolateral wall of the left ventricle. Results. Linear regression analysis showed that there was a good correlation between …

Evaluation of the Complexity of Myocardial Activation During Ventricular Fibrillation. An Experimental Study

A B S T R A C T Introduction and objectives: An experimental model is used to analyze the characteristics of ventricular fibrillation in situations of variable complexity, establishing relationships among the data produced by different methods for analyzing the arrhythmia. Methods: In 27 isolated rabbit heart preparations studied under the action of drugs (propranolol and KB-R7943) or physical procedures (stretching) that produce different degrees of change in the complexity of myocardial activation during ventricular fibrillation, use was made of spectral, morphological, and mapping techniques to process the recordings obtained with epicardial multielectrodes. Results: The complexity of ve…

P312The selective late sodium current inhibitor eleclazine attenuates ventricular fibrillation spectral characteristics modifications produced by acute myocardial stretch

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…

Changes in the Spectral Characteristics of Ventricular Fibrillation in Lesions Produced by Radiofrequency Ablation. An Experimental Study

INTRODUCTION AND OBJECTIVES Although electro- physiological databases contain information about changes in the time domain in lesions produced by radiofrequency ablation, very few data on changes in the frequency domain are available. The aim of this study was to investigate changes in the spectral characteristics of ventricular fibrillation in zones with radiofrequency lesions. METHODS Recordings of ventricular fibrillation were obtained in 11 isolated perfused rabbit heart preparations using a multiple epicardial electrode located on the left ventricular free wall. Spectral parameters derived by Fourier analysis before and after the creation of transmural radiofrequency lesions were compa…

Ranolazine induced modifications of ventricular fibrillation activation complexity under mechanical stretch

P267Myocardial electrophysiological effects mediated by KATP channels: controversial aspects about their involvement in the protection by chronic exercise

P1602Basic electrophysiological modifications induced by carvedilol in unstrectched and stretched ventricular myocardium

Abstract Background Acute regional ventricular stretch (ARVS) is a pathophysiologic event that may occur in certain situations, originating arrhythmogenic effects through the mechanoelectrical feedback. Mechanical effects of stretch originate calcium-related changes as sarcoplasmic recticulum Ca2+ overload that can trigger Ca2+ diastolic leaks (store-overload-induced Ca2+ release, SOICR), mediated by the cardiac ryanodine receptor (RyR2). SOICR seems to be implicated in the mechanisms underlying stretch-induced arrhythmias. Carvedilol can inhibit the overload of Ca2+ through blocking of beta-adrenergic receptors, and also suppress the release of Ca2+ induced by the SOICR. Purpose The aim of…

Development and Long-Term Follow-Up of an Experimental Model of Myocardial Infarction in Rabbits

Simple Summary Ischemic heart disease is one of the leading causes of death. A series of processes occur during acute myocardial infarction that contribute to the development of ventricular dysfunction, with subsequent heart failure and ventricular arrhythmias, which account for most episodes of sudden cardiac death in these patients. These complications are associated with the adverse cardiac remodeling that occurs during the healing process following an acute episode. The remodeling causes the appearance of a substrate that can trigger life-threatening arrhythmias, such as tachycardia and/or ventricular fibrillation. The development of experimental models for analyzing the basic mechanism…

Application of machine learning techniques to analyse the effects of physical exercise in ventricular fibrillation

This work presents the application of machine learning techniques to analyse the influence of physical exercise in the physiological properties of the heart, during ventricular fibrillation. To this end, different kinds of classifiers (linear and neural models) are used to classify between trained and sedentary rabbit hearts. The use of those classifiers in combination with a wrapper feature selection algorithm allows to extract knowledge about the most relevant features in the problem. The obtained results show that neural models outperform linear classifiers (better performance indices and a better dimensionality reduction). The most relevant features to describe the benefits of physical …

Endurance training increases ventricular refractoriness and wavelength of the cardiac impulse without participation of parasympathetic postganglionic neurons. A study in isolated rabbit heart

Abstract Background Endurance physical training plays a protective role in against ventricular fibrillation (VF), but the exact underlying mechanisms are not completely understood. It is well-known that modifications in myocardial ventricular properties such as refractoriness, conduction velocity and wavelength are key in the initiation and maintenance of VF; furthermore, vagus nerve stimulation has prophylactic effects on malignant arrhythmias and VF. On the other hand, parasympathetic nervous system activity is increased in trained individuals, which in turn affects different ventricular electrophysiological properties. We hypothesized that physical training increases conduction velocity …

P314Modifications of atrial refractoriness produced in an experimental rabbit model of diet-induced metabolic syndrome

P3492Carvedilol and its analogue VK-II-86 attenuate stretch-induced manifestations of mechanoelectric feedback

Abstract Background Mechanical stretch modifies Ca2+ handling and myocardial electrophysiology, favoring arrhythmogenesis. The store-overload-induced Ca2+ release (SOICR) through the ryanodine receptor (RyR2) seems to be implicated in this deleterious effect. Carvedilol and its analogue VK-II-86 (which does not have significant beta-blocking effects) suppress SOCIR by directly reducing the open duration of the cardiac RyR2, and could modulate calcium-related changes produced by myocardial stretch. Purpose The aim of this study was to investigate, by the ventricular fibrillation (VF) spectral analysis, whether carvedilol and VK-II-86 prevents stretch-induced arrhythmogenic effects. Methods T…

Effect of chronic exercise on myocardial electrophysiological heterogeneity and stability. Role of intrinsic cholinergic neurons: A study in the isolated rabbit heart

[EN] A study has been made of the effect of chronic exercise on myocardial electrophysiological heterogeneity and stability, as well as of the role of cholinergic neurons in these changes. Determinations in hearts from untrained and trained rabbits on a treadmill were performed. The hearts were isolated and perfused. A pacing electrode and a recording multielectrode were located in the left ventricle. The parameters determined during induced VF, before and after atropine (1 mu M), were: fibrillatory cycle length (VV), ventricular functional refractory period (FRPVF), normalized energy (NE) of the fibrillatory signal and its coefficient of variation (CV), and electrical ventricular activatio…

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

Dominant frequency and complexity of electrical reentrant activation during ventricular fibrillation with releasing of NO after acute local stretching. A study in isolated rabbit heart

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…

CaMKII inhibition reduces electrical activation heterogeneities caused by mechanical stretch in the myocardium

Abstract Introduction Ca2+/calmodulin-dependant protein kinase II (CaMKII) activity in cardiomyocytes plays a crucial role in their contractility. Increased CaMKII signalling has been associated with mechanical stretch, often caused in the border zone of myocardial infarction. CaMKII upregulation causes a mishandling of intracellular calcium, a precursor of multiple pro-arrhythmic mechanisms, such as early afterdepolarisations. Purpose In this study, we aim to quantify the effects of KN-93 -a CaMKII inhibitor- on wave dynamics, in order to investigate its effectiveness as an anti-arrhythmic agent. Methods An isolated Langendorff model was constructed based on rabbit hearts (n=18) and poster…

An Experimental Model of Diet-Induced Metabolic Syndrome in Rabbit: Methodological Considerations, Development, and Assessment

In recent years, obesity and metabolic syndrome (MetS) have become a growing problem for public health and clinical practice, given their increased prevalence due to the rise of sedentary lifestyles and unhealthy eating habits. Thanks to animal models, basic research can investigate the mechanisms underlying pathological processes such as MetS. Here, we describe the methods used to develop an experimental rabbit model of diet-induced MetS and its assessment. After a period of acclimation, animals are fed a high-fat (10% hydrogenated coconut oil and 5% lard), high-sucrose (15% sucrose dissolved in water) diet for 28 weeks. During this period, several experimental procedures were performed to…

Influencia del tipo de registro (unipolar o bipolar) en las características espectrales de los registros epicárdicos de la fibrilación ventricular. Estudio experimental

Introduction and objectives. The aim of this study was to examine the hypothesis that the recording mode (ie, unipolar or bipolar) affects the information obtained using spectral analysis techniques during ventricular fibrillation by carrying out an experiment using epicardial electrodes. Methods. Recordings of ventricular fibrillation were obtained in 29 isolated rabbit hearts using a multipleelectrode probe located on the left ventricular free wall. The parameter values obtained in the frequency domain (by Fourier analysis) using unipolar or bipolar electrodes, different interelectrode distances, and different orientations (ie, horizontal, vertical, or diagonal) were compared. Results. Ch…

Modificaciones de las características espectrales de la fibrilación ventricular en las lesiones producidas con radiofrecuencia. Estudio experimental

Introduccion y objetivos Aunque se dispone de informacion sobre las modificaciones en el dominio del tiempo de los registros electrofisiologicos en zonas lesionadas con radiofrecuencia, los datos disponibles en el dominio de la frecuencia son muy escasos. Se analizan las modificaciones de las caracteristicas espectrales de la fibrilacion ventricular en zonas lesionadas con radiofrecuencia. Metodos En 11 preparaciones de corazon aislado y perfundido de conejo, se registra la fibrilacion ventricular con un electrodo multiple epicardico situado en la pared libre ventricular izquierda. Se comparan los parametros espectrales obtenidos mediante analisis de Fourier antes y despues de practicar les…

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…

Effect of chronic exercise and ATP-sensitive potassium channel blockade on the spectral characteristics evolution of ventricular fibrillation in acute regional ischemia

Purpose: It has been proposed that chronic exercise produces a KATP channel blockade in ischemic myocardium. We have also reported that channel blockade and training exert very similar effects on energy required to defibrillate. In fact it is postulated that one mechanism by which exercise exerts an antiarrhythmic effect, is by blocking KATP channel. We have analyzed the evolution of spectrum characteristics of ventricular fibrillation (VF), in normoxic conditions and after acute myocardial ischemia, in isolated hearts from trained rabbits, and in hearts submitted to KATP channel blockade. Our hypothesis is that the spectrum characteristics of VF evolve similarly in trained hearts and in he…

Effects of exercise training on adrenergic and cholinergic responses of rabbit carotid artery

P330Modifications of short-term heart rate varibility and intrinsic pacemaker variability in an experimental model of metabolic syndrome

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…

Diet-Induced Metabolic Syndrome Reduced Heart Rate Variability and Increased Irregularity and Complexity of Short-Term RR Time Series in Rabbits.

Simple Summary In recent years, obesity and metabolic syndrome (MetS) have become more prevalent, owing to increased unhealthy habits and sedentary lifestyles becoming public health problems. Both conditions are linked with a higher prevalence of sudden cardiac death (SCD), but the exact mechanisms are not known. An autonomic nervous system imbalance can produce atrial and ventricular arrhythmias, which cause SCD, and this can be quantified by analyzing heart rate variability (HRV). We investigated HRV using time-domain, frequency-domain and nonlinear analyses during the development of MetS in rabbits and found HRV modifications that could be associated with the higher prevalence of SCD in …

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…

Development and characterization of an experimental model of diet-induced metabolic syndrome in rabbit

Metabolic syndrome (MetS) has become one of the main concerns for public health because of its link to cardiovascular disease. Murine models have been used to study the effect of MetS on the cardiovascular system, but they have limitations for studying cardiac electrophysiology. In contrast, the rabbit cardiac electrophysiology is similar to human, but a detailed characterization of the different components of MetS in this animal is still needed. Our objective was to develop and characterize a diet-induced experimental model of MetS that allows the study of cardiovascular remodeling and arrhythmogenesis. Male NZW rabbits were assigned to control (n = 15) or MetS group (n = 16), fed during 2…

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, …

Time and frequency domain analysis of long-term heart rate variability in an experimental model of diet-induced metabolic syndrome

Abstract Background Metabolic syndrome (MetS) is defined as the set of at least three of the following conditions: central obesity, elevation of triglycerides, decreased in high-density lipoproteins, systemic hypertension and glucose intolerance. MetS is linked with a high prevalence of cardiovascular disease, including sudden cardiac death and atrial arrhythmias, which may be a consequence of changes related to the structure, function and autonomic control of the heart. One of the underlying mechanisms responsible could be the alteration of sinus node automaticity. Heart rate variability (HRV) analysis is a useful non-invasive tool for evaluating alterations in neural control of cardiac au…

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…

Evaluación de la complejidad de la activación miocárdica durante la fibrilación ventricular. Estudio experimental

Resumen Introduccion y objetivos Analizar en un modelo experimental las caracteristicas de la fibrilacion ventricular en situaciones con distintos grados de complejidad y establecer la relacion existente entre los datos aportados por distintos metodos de analisis de la arritmia. Metodos En 27 preparaciones de corazon aislado de conejo estudiadas bajo la accion de farmacos (propranolol y KB-R7943) o procedimientos fisicos (estiramiento) que causan distintos grados de variacion de la complejidad de la activacion miocardica durante la arritmia, se han utilizado tecnicas espectrales, morfologicas y cartograficas para procesar los registros obtenidos con multielectrodos epicardicos. Resultados L…

P1605Increased irregularity and spectral complexity of the intrinsic pacemaker beat-to-beat variability correlates with increased metabolic syndrome components

Abstract Background Metabolic syndrome (MetS) is becoming one of the future potential leading risk factors for heart and cardiovascular disease. MetS relates to a condition associated with at least three metabolic risk factors raising risk for health diseases concomitantly such as diabetes, stroke, hypertension, obesity and dyslipidemia. This can lead to chest pain, heart attack, heart damage and overall higher prevalence of cardiovascular disease, atrial fibrillation and sudden cardiac death. One of the underlying mechanisms of the progressive remodeling in presence of MetS components could be altered automaticity, which would reflect modifications of sinus node activity. These phenomena c…

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…