摘要:

Mechanisms of VF.Introduction: It is not known whether ventricular fibrillation (VF) is always caused by multiple wavelet reentry, or if it could also be caused by a single wandering reentrant wavefront. Activation mapping of the entire ventricles during VF is practically impossible.Methods and Results: We studied VF in a two‐dimensional sheet of left ventricular subepicardial tissue of isolated. Langendorff‐perfused pig hearts. Left and right endocardial cryoablation via probes tilled with liquid nitrogen caused coagulation necrosis of the right ventricle, interventricular septum, and most of the left ventricular wall, leaving a thin subepicardial layer intact. Left ventricular epicardial activation patterns were constructed based on simultaneous recording of 128 unipolar extracellular electrograms. Regular pacing through a central electrode before and after freezing revealed that, following cryoablation, the activation pattern no longer showed evidence of involvement of the Purkinje system, and that it was compatible with propagation through a two‐dimensional anisotropic tissue sheet. VF was induced by burst pacing. When the mass of surviving subepicardium was20 g. VF was sustained. Unipolar extracellular electrograms during VF before and after cryoablation could not be distinguisbed from each other; however, epicardial activation patterns were markedly different. In the intact left ventricle, up to six different wavefronts were simultaneously present during a 100‐msec time window. In the “frozen heart.” during a period of about 0.5 seconds, at most two wandering reentrant waves were simultaneously present; sometimes only one reentrant wave was seen in a 100‐msec time window.Conclusion: The extracellular waveform during VF can be caused by different forms of reentry: multiple wavelet reentry (on the order of six different wavefronts), two independent wandering reentrant waves, and a single wandering r

ISSN:1045-3873    

DOI:10.1111/j.1540-8167.1995.tb00424.x

出版商:Blackwell Publishing Ltd    

年代:1995

数据来源: WILEY

摘要:

Heart Surface Source Model.Introduction: The bidomain model of the heart leads to the result that the volume density of cardiac current source moment is proportional to the gradient of the macroscopic transmembrane action potential distribution. If the anisotropy ratios of the inner and outer domains (syncytia) of the myocardium are equal, then the volume distribution of cardiac sources can be replaced by an appropriate double layer on the heart surface. The double layer source distribution (heart surface source model) provides a basis for calculating heart surface potentials from cardiac sources.Methods and Results: The heart surface model was used to calculate epicardial potentials for the normal heart as well as for a case of ischemia and of infarction. The model was also used to determine the effect of insulating the heart surface. Insulating the heart surface caused an almost fourfold increase in peak‐to‐peak amplitude of simulated electrograms, with little change in waveshape. Simulated electrograms showed good agreement with recorded electrograms reported in the literature.Conclusion: The heart surface source model appears to provide a basis for relating heart surface potentials to the distribution of cellular action potent

ISSN:1045-3873    

DOI:10.1111/j.1540-8167.1995.tb00425.x

出版商:Blackwell Publishing Ltd    

年代:1995

数据来源: WILEY

摘要:

Reperfusion Arrhythmias and Afterdepolarizations.Introduction: The precise mechanism of reperfusion arrhythmias is not established. The role of early afterdepolarizations (EADs) and triggered activity in the genesis of reperfusion ventricular arrhythmia was investigated.Methods and Results: Monophasic action potentials (MAPs) were recorded in the canine heart using Ag‐AgCl contact electrodes from the left and right ventricular endocardium and the left ventricular epicardial border zone during 10 minutes of occlusion of the proximal left anterior descending coronary artery followed by 2 minutes of reperfusion. Ventricular arrhythmias during ischemia and reperfusion were studied in three autonomically varied groups. Group 1 (n = 8) had intact autonomic neural innervation; group 2 (n =8) had bilateral transection of ansae subclavii and vagi; and group 3 (n =8) underwent bilateral transaction of ansae subclavii and vagi with bilateral ansae subclavii stimulation during reperfusion. Ventricular fibrillation (VF) on reperfusion occurred in 2, 3, and 5 animals in the innervated, denervated, and sympathetically stimulated groups, respectively. Rapid ventricular tachycardia during ansae subclavii stimulation, antecedent to VF, occurred in 4 of 5 episodes in the sympathetically stimulated group. The frequency of premature ventricular complexes, couplets, and triplets on reperfusion was not significantly different among the three groups. Phase 2 or phase 3 EADs were noted during the acute ischemic phase in 6 of 8, 7 of 8, and 7 of S animals in the three groups, respectively (and persisted during reperfusion in the majority). Thus, these EADs were not a de novo phenomenon during reperfusion. Of the 72 MAP recording sites, only one demonstrated de novo phase 2 EADs during reperfusion. EADs disappeared during reperfusion in 6 animals (prior to the onset of VF in 4), and 5 dogs developed reperfusion VF without EADs being recorded. There was no direct correlation between tbe presence of EADs during repertusion and the development of VF. The prevalence and onset of reperfusion VT was not significantly different in tbe presence of sympathetic stimulation.Conclusion: This study demonstrates that EADs can be recorded in the majority of dogs during both ischemia and reperfusion and do not appear to be a major mechanism responsible for reperfusion ventricular tachycardia and V

ISSN:1045-3873    

DOI:10.1111/j.1540-8167.1995.tb00426.x

出版商:Blackwell Publishing Ltd    

年代:1995

数据来源: WILEY

摘要:

Recipient‐to‐Donor Interatrial Tachycardia. Interatrial conduction of recipient atrial tachycardia to the donor atria of an orthotopic heart transplant recipient resulted in a unique cause of supraventricular tachycardia. An electrophysiologic study was performed, and the recipient atria was found to be in an atrial tachycardia, cycle length of 210 msec, with periods of both 2:1 and 1:1 conduction to the donor atria resulting in a donor atrial cycle length of 420 msec and 210 msec, respectively. The site of interatrial conduction was mapped to the right atrial suture line, along the atrial free wall, and was successfully disrupted with radiofrequency energy. Arrhythmias of a similar mechanism may also be observed in other postsurgical patie

ISSN:1045-3873    

DOI:10.1111/j.1540-8167.1995.tb00427.x

出版商:Blackwell Publishing Ltd    

年代:1995

数据来源: WILEY

摘要:

MSORTV in Patterned Growth Heart Cell Cultures. It is well established that impulse propagation in cardiac tissue is determined by the interaction between active membrane properties and the passive electrical characteristics of the network formed by individual myocytes. In the past, the intricate microarchitecture of intact cardiac tissue and the limited spatial resolution of available recording techniques had rendered a systematic evaluation of the influence of the cellular microarchitecture on impulse propagation difficult. Recently, however, successful efforts have been undertaken to: (1) simplify the cellular arrangement by designing cardiac structures with defined two‐dimensional geometries; and (2) measure impulse propagation in these preparations at the cellular/subcellular scale using optical techniques. This short review considers both of these developments, i.e., patterned growth of heart cells in culture and multiple site optical recording of transmembrane voltage (MSORTV), and summarizes first results obtained with the combination of both technique

ISSN:1045-3873    

DOI:10.1111/j.1540-8167.1995.tb00428.x

出版商:Blackwell Publishing Ltd    

年代:1995

数据来源: WILEY

摘要:

Neurocardiogenic Syncope. Neurocardiogenic syncope is a collective term used to describe the clinical syndromes of syncope that result from inappropriate, and often excessive, autonomic reflex activity, and manifest as abnormalities in the control of vascular tone and heart rate. These include carotid sinus syndrome, vasovagal syncope, and the syndromes of cough, deglutition, and micturition syncope. Orthostatic hypotension, which, in contrast, results from a failure of autonomic reflexes, is not considered part of this family of closely related syndromes. This review will focus on vasovagal and carotid sinus syndromes.

ISSN:1045-3873    

DOI:10.1111/j.1540-8167.1995.tb00429.x

出版商:Blackwell Publishing Ltd    

年代:1995

数据来源: WILEY

ISSN:1045-3873    

DOI:10.1111/j.1540-8167.1995.tb00430.x

出版商:Blackwell Publishing Ltd    

年代:1995

数据来源: WILEY

ISSN:1045-3873    

DOI:10.1111/j.1540-8167.1995.tb00431.x

出版商:Blackwell Publishing Ltd    

年代:1995

数据来源: WILEY

ISSN:1045-3873    

DOI:10.1111/j.1540-8167.1995.tb00432.x

出版商:Blackwell Publishing Ltd    

年代:1995

数据来源: WILEY

摘要:

Spontaneous Ventricular Defibrillation. Ventricular fibrillation (VF) is one of the most life‐threatening arrhythmias encountered in daily clinical practice. Its occurrence cannot be completely prevented by currently used antiarrhythmic drugs, and, in most instances, VF is sustained and leads lo the patient's death unless a successful DC defibrillation is applied. However, spontaneous reversion of VF to sinus rhythm has been observed in various animals and occasionally even in man. Hence, facilitation of self ventricular defibrillation must be explored as an alternative therapeutic approach. In experimental studies using several mammalian species, we have found that self ventricular defibrillation requires a good intercellular coupling and well synchronized electrical activity in the ventricles, which, in untreated animals, depend on their myocardial catecholamine content. It can then be hypothesized that any agent that elevates the catecholamine level during VF would facilitate spontaneous ventricular defibrillation, and drugs inhibiting extraneuronal catecholamine reuptake have indeed been shown to possess this ability. It is suggested that their effects are mediated by an increase in the intracellular cAMP level, and any compounds sharing this property could well prove efficacious in making VF transient and in reducing sudden cardiac deat

ISSN:1045-3873    

DOI:10.1111/j.1540-8167.1995.tb00433.x

出版商:Blackwell Publishing Ltd    

年代:1995

数据来源: WILEY