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Predictors of left atrial appendage stunning after electrical cardioversion of non-valvular atrial fibrillation.

OBJECTIVE: To identify predictors of left atrial appendage stunning after the use of electrical cardioversion to restore sinus rhythm in patients with non-valvular atrial fibrillation. METHODS: A total of 68 consecutive patients (45 men, 23 women, 60.5 +/- 8.7 years of age) with non-valvular atrial fibrillation undergoing electrical cardioversion were enlisted in this study. Clinical and echocardiographic variables were analyzed by univariate regression and multivariate logistic regression to investigate the relationship between occurrences of left atrial appendage stunning and these factors. RESULTS: Univariate analysis revealed that, in comparing patients without and with left atrial appendage stunning, there were significant differences in the duration of atrial fibrillation > 8 weeks (32.3% vs 75.5%, P < 0.001), left atrial diameter > 50 mm (29.0% vs 54.1%, P < 0.05), left atrial emptying fraction (31.5% +/- 7.8% vs 27.1% +/- 8.5%, P < 0.05), left ventricular ejection fraction < 50% (38.7% vs 67.6%, P < 0.05), maximum electrical energy (96.8 J +/- 65.8 J vs 156.8 J +/- 100.8 J, P < 0.01), cumulative electrical energy 146.8 J +/- 142.6 J vs 290.5 J +/- 242.1 J, P < 0.01) and number of electrical cardioversion shocks (1.7 +/- 0.9 vs 2.43 +/- 1.20, P < 0.05). However, backward stepwise multivariate logistic regression analysis identified as significant and independent predictors of left atrial appendage stunning only duration of atrial fibrillation > 8 weeks (OR = 7.249, 95% CI = 1.998 - 26.304, P < 0.01), left atrial diameter > 50 mm (OR = 3.896, 95% CI = 1.105 - 13.734, P < 0.05), left ventricular ejection fraction < 50% (OR = 4.465, 95% CI = 1.51713.140, P < 0.01) and cumulative energy of electrical cardioversion (OR = 1.004, 95% CI = 1.000 - 1.008, P < 0.05). CONCLUSIONS: Duration of atrial fibrillation > 8 weeks, left atrial diameter > 50 mm, left ventricular ejection fraction < 50%, and cumulative energy of electrical cardioversion are independent predictors of left atrial appendage stunning. Anticoagulation treatment should be individualized for patients undergoing electrical cardioversion to reduce the risk of both cardioversion-related thromboembolic events and hemorrhagic complications caused by warfarin treatment.

Aged↗

Electrically evoked myoelectric signals.

Electrical stimulation of the nervous system is attracting increasing attention because of the possibilities it offers for physiological investigations, clinical diagnosis, muscle function assessment, noninvasive muscle characterization, and functional control of paralyzed extremities. Parameters of the myoelectric signal evoked by surface stimulation of a muscle motor point or by stimulation of a nerve trunk by means of implanted electrodes provide information about muscle performance and properties if the stimulation artifact is properly removed or suppressed. Comparison of these parameters with those obtained during voluntary contractions provides additional insight into muscle physiology. The relationships between myoelectric signal amplitude parameters, spectral parameters, and conduction velocity are discussed with special reference to muscle fatigue. This review focuses on a few methodological aspects concerning electrical stimulation of the peripheral nervous system, detection, and processing of the electrically evoked myoelectric signals in skeletal muscles. The state of the art of the following issues is discussed: (1) properties of voluntary and electrically evoked myoelectric signals; (2) techniques for evoking and detecting myoelectric signals; (3) techniques for suppression of stimulation artifacts; (4) effect of stimulation waveforms and electrode properties; (5) signal processing techniques for electrically evoked myoelectric signals; (6) physiological significance of myoelectric signal variables; (7) order of recruitment of motor units during electrical stimulation; (8) myoelectric manifestations of fatigue in electrically stimulated muscles; (9) assessment of crosstalk by electrical stimulation; and (10) applications in sport, rehabilitation, and geriatric medicine.

Animals↗

[Biophysical models of the heart electrical activity].

Based on the fundamental knowledge of the space-temporal organization of extracellular electrical fields of the myocardium, a system for 3-D computer modeling of the cardiac electrical activity at different structural levels of the object is being developed at the Institute of Theoretical and Experimental Biophysics. The system is based on the earlier proposed and modified biophysical model of the electrocardiosignal genesis represented by a double electrical layer along the surface of the electrically active myocardium. The system combines the model for activation and repolarization of the heart ventricles; the advanced model for the evaluation of parameters of the cardiac electric field, which makes it possible to derive model electrocardiosignals both in the direct regime of calculation of the potentials and in the regime of calculation of electrocardiosignals from preliminarily determined components of the multipole equivalent electrical heart generator; a database for the model parameters and their combinations in the form of cards of simulated "patients", and a database of modeled electrocardiosignals. In the present paper (first from three within the framework of the problem), simulation methods in electrocardiology are briefly described and a biophysical model of the heart electrical activity is presented, which has made up the basis of the system for computer modeling of forward and inverse problems of the cardiac electric field. The parameters of the model are electrophysiological, anatomical, and biophysical characteristics of the heart.

Biophysical Phenomena↗

A tyrosine kinase related to pp60c-src is associated with membranes of Electrophorus electricus electric organ.

A tyrosine-specific protein kinase immunologically related to pp60c-src, the cellular homolog of the Rous sarcoma virus-transforming protein, was expressed at elevated levels in the electric organ of the electric eel Electrophorus electricus. The electric organ kinase phosphorylated antibodies reactive with pp60c-src at tyrosine residues in immune complex protein kinase assays and was associated with electric organ membranes enriched in acetylcholine receptors. The protein recognized by anti-pp60c-src antibodies was phosphorylated in endogenous membrane phosphorylation reactions and was shown to have a relative molecular mass of 57 kDa by two-dimensional gel electrophoresis. In immune complex protein kinase assays the 57-kDa protein was phosphorylated at threonine by a distinct threonine kinase from the electric organ. The tyrosine kinase was purified 844-fold from electric organ membranes by chromatography on omega-aminohexyl agarose, phosphocellulose, and casein-Sepharose. Threonine kinase activity in immunoprecipitates was not observed in the tyrosine kinase fractions after the first step. Incubation of the casein Sepharose fraction with [gamma-32P]ATP-Mn2+ in solution resulted in phosphorylation of only the 57-kDa protein. Phosphorylation occurred solely at tyrosine, suggesting that the kinase is capable of autophosphorylation. The structural and functional properties of the 57-kDa electric organ kinase indicate that the 57-kDa electric organ protein is a member of the src subfamily of tyrosine kinases and is closely related to pp60c-src.

Animals↗

Short and long latency reflexes in human muscles following electrical and mechanical stimulation.

Electromyographic (EMG) recordings were made during slight voluntary contraction or during rest in various human muscles following electrical and mechanical stimulation. The electrical stimuli used in most of these experiments were square wave pulses with the duration of 100 microseconds given at a frequency of 3 Hz on cutaneous and mixed nerves. The mechanical stimuli were constant stretches of the muscle induced by taps of the electromechanical reflex hammer. The aims of the series of studies were to investigate the characteristic features of electrically and mechanically elicited muscular responses, the correspondence between electrically and mechanically elicited responses, the short latency response following muscle afferent stimulation and the modifications of the electrically elicited responses. The electrical stimulation during slight voluntary activity caused short and long latency excitatory phases in averaged and rectified EMG with the onset latencies much shorter than the voluntary reaction time. The responses were considered reflexive. The most constant short and long latency reflexes following electrical stimulation were found in the first dorsal interosseus muscle in the hand and in the extensor digitorum brevis in the foot. The mean onset latency for the short latency reflex was 30.9 +/- 1.7 ms (SD) and for the long latency reflex 50.9 +/- 2.8 ms in the hand muscle. In the foot muscle the mean short latency reflex latency was 54.9 +/- 4.1 ms and the long latency reflex latency was 80.5 +/- 5.5 ms. The onset latencies of the short and long latency reflexes during slight voluntary activity following stretching and following cutaneous nerve stimulation corresponded in the first dorsal interosseus muscle. It was concluded that they are generated at least partly via mutual pathways. The stretches given to the triceps brachii muscle during various head positions, different elbow angles and during the Jendrassik maneuver revealed short latency reflex facititations. The lesser degree of the facilitation was caused by the tonic neck reflex and the Jendrassik maneuver caused the greater degree of the facilitation. The short latency reflex following muscle afferent stimulation (the H-reflex) was elicited in the flexor carpi radialis muscle with a mean latency of 15.4 +/- 0.5 ms. The amplitude of the 50% H-reflex was modified by contracting or by stretching of the muscle. Voluntary contraction increased the 50% H-reflex amplitude about 30% and the passive stretching decreased it to about 80% of the control value. The patients with different central nervous system disorders showed abnormal electrically elicited short and long latency reflexes. The s

Adult↗

Electrical measurements of complement-mediated membrane damage in cultured nerve and muscle cells.

Cultured neuroblastoma-glioma hybrid cells and primary mouse and rat muscle cells were studied by using intracellular microelectrodes to monitor membrane electrical potential and resistance changes during complement-mediated lysis. The cell membrane was TNP modified under mild conditions and subsequently coated with rabbit IgG anti-TNP, with no electrical changes observed. However, upon addition of guinea pig C the membrane potential dropped from approximately -50 mv to less than -12 mv within a few minutes, with parallel decreases in electrical resistance. Ten to 60 min after these electrical changes the cells became stainable with trypan blue. No electrical changes or trypan blue staining was observed in the absence of antibody or with heat-inactivated C. With more dilute C so that only a fraction of cells became trypan blue positive, all cells nevertheless showed the membrane electrical changes; surviving cells recovered their original membrane properties within 1 hr. Thus the C-mediated damage to the membrane measured electrically is not in itself sufficient to ensure the subsequent death of the cell. The early electrical changes observed appear to be comparable to increases in 86Rb efflux measured by others.

Animals↗

60-Hertz electric-field exposures in transmission line towers.

This article reports on an investigation of 60-Hz electric-field exposures of line workers in 230- to 765-kV transmission line towers. The exposures were based on computations of the unperturbed electric field along climbing routes and at work positions on the towers and on insulated ladders suspended in towers. Computed exposures were expressed in terms of the unperturbed electric field averaged over the body as stipulated by guidelines. For the realistic on-tower positions, the worker's posture, the uniformity of the field, and the field orientation differed from the guideline exposure scenario of standing erect in a vertical uniform field. These differences suggest the need for care in comparing electric-field exposures in towers with guideline limits. The unperturbed nonuniform fields at discrete points near steel and aluminum lattice structures were computed using Monte Carlo methods that model surface and spatial electric fields on and near standard geometrical elements. To estimate a whole-body average, fields were computed at 10 discrete points positioned on segments of an articulated stick-figure model of the human body. The whole-body average field was computed from fields at all the points weighted by the fraction of body volume that the corresponding segment represented. We estimated the average unperturbed electric field, the space potential at the torso, and the induced short-circuit current for 19 climbing and work positions in six towers. The maximum average electric-field exposure during climbing ranged from 10 kV/m for a 230-kV tower to 31 kV/m for a 765-kV tower. Exposures at on-tower work positions were lower than the estimated maximum exposures during climbing. For 500- and 765-kV towers, computed exposures while climbing and at some on-tower positions exceeded the limit of 20 kV/m given in the recently adopted IEEE Standard C95.6 2002. For lower voltage towers, exposures did not exceed 20 kV/m.

Adult↗

Electrical injuries.

Electrical injury is a relatively infrequent but potentially devastating form of multisystem injury with high morbidity and mortality. Most electrical injuries in adults occur in the work-place, whereas children are exposed primarily at home. In nature, electrical injury occurs due to lightning, which also carries the highest mortality. The severity of the injury depends on the intensity of the electrical current (determined by the voltage of the source and the resistance of the victim), the pathway it follows through the victim's body, and the duration of the contact with the source of the current. Immediate death may occur either from current-induced ventricular fibrillation or asystole or from respiratory arrest secondary to paralysis of the central respiratory control system or due to paralysis of the respiratory muscles. Presence of severe burns (common in high-voltage electrical injury), myocardial necrosis, the level of central nervous system injury, and the secondary multiple system organ failure determine the subsequent morbidity and long-term prognosis. There is no specific therapy for electrical injury, and the management is symptomatic. Although advances in the intensive care unit, and especially in burn care, have improved the outcome, prevention remains the best way to minimize the prevalence and severity of electrical injury.

Adult↗

Role of creatine phosphate in the discharge of the electric organ of Torpedo marmorata.

The role of creatine phosphate and adenosine triphosphate, as high energy phosphate sources, has been investigated during the discharge and recovery of the electric organ of Torpedo. ATP serves as the immediate source of energy for the biochemical process supporting the electrical activity of the electric organ. Under repetitive stimulation, when the energy demands exceed production, ATP levels are maintained constant at the expense of creatine phosphate. Only when the reservoir of creatine phosphate is depleted do the levels of ATP decrease, and this point corresponds to the state of maximal fatigue of the electric organ. Recovery studies show that the electric organ rapidly recovers the capacity to respond to single pulse stimuli. This recovery is statistically related to the recovery of the levels of ATP and acetylcholine. However, in this phase, the fatiguability of the electric organ is very high since its energy reservoir is still depleted. The complete recovery of the electric organ requires several hours and is closely related to the restoration of the levels of creatine phosphate.

Acetylcholine↗

Granular cells of the mormyrid electrosensory lobe and postsynaptic control over presynaptic spike occurrence and amplitude through an electrical synapse.

Primary afferent fibers from the electroreceptors of mormyrid electric fish use a latency code to signal the intensity of electrical current evoked by the fish's own electric organ discharge (EOD). The afferent fibers terminate centrally in the deep and superficial granular layers of the electrosensory lobe with morphologically mixed chemical-electrical synapses. The granular cells in these layers seem to decode afferent latency through an interaction between primary afferent input and a corollary discharge input associated with the EOD motor command. We studied the physiology of deep and superficial granular cells in a slice preparation with whole cell patch recording and electrical stimulation of afferent fibers. Afferent stimulation evoked large all-or-none electrical excitatory postsynaptic potentials (EPSPs) and large all or none GABAergic inhibitory postsynaptic potentials (IPSPs) in both superficial and deep granular cells. The amplitudes of the electrical EPSPs depended on postsynaptic membrane potential, with maximum amplitudes at membrane potentials between -65 and -110 mV. Hyperpolarization beyond this level resulted in either the abrupt disappearance of EPSPs, a step-like reduction to a smaller EPSP, or a graded reduction in EPSP amplitude. Depolarization to membrane potentials lower than that yielding a maximum caused a linear decrease in EPSP amplitude, with EPSP amplitude reaching 0 mV at potentials between -55 and -40 mV. We suggest that the dependence of EPSP size on postsynaptic membrane potential is caused by close linkage of pre- and postsynaptic membrane potentials through a high-conductance gap junction. We also suggest that this dependence may result in functionally important nonlinear interactions between synaptic inputs.

Action Potentials↗

Temporal structure of non-propagated electric communication signals.

Acoustic and electric communication differ in one important respect: while acoustic communication signals propagate through air or water as a wave, electric signals do not propagate, but exist instead as electrostatic fields. As a result of propagation, acoustic signals are distorted during transmission in a largely unpredictable way. Sound receivers, therefore, may not be able to recognize fine details in the waveform of an acoustic signal, but may have to rely instead upon time intervals between repetitions of a waveform, on the frequency of a signal, or on frequency modulations. By contrast, non-propagating electric communication signals are immune to many sources of signal distortion that affect sounds. Consequently, electric signal receivers may reliably use waveform cues to recognize a sender's identity and discriminate between signals. As examples, mormyrid electric fish encode species and sex differences in the fine structure of the electric organ discharge waveform and sense the differences using temporal cues. Gymnotiform pulse-discharging electric fish may employ scan-sampling for waveform analysis: a specialized mechanism analogous to a digital sampling oscilloscope for slowly scanning a repetitive waveform.

Acoustics↗

Electrical current density model from surface electrodes.

The goal of this research is to determine the optimum electrical current for subthreshold electrical stimulation. The first step is to collect atrophied muscle impedance data from children with neuromuscular disorders using Bioelectric Impedance Analysis (BIA). Then to incorporate this impedance data into a model using the 3-D Finite Element Method (FEM). This will allow the evaluation of electric current densities in the target muscle resulting from Therapeutic Electrical Stimulation (TES). Using the FEM, optimum electrical stimulation parameters, levels, and electrode placement can be determined. The FEM will provide the first means to determine the quantity of electric current flowing through the target muscle from surface electrode stimulation. TES is adding new life to electrical stimulation therapy. TES is low intensity (subthreshold), long duration transcutaneous stimulation using surface electrodes. TES effects muscle growth and peripheral nerve sprouting leading to increased functional control and sensation. The initial parameters used in TES have been proven clinically to be effective for use in rehabilitation therapy for people with neuromuscular disorders. This research is the first step towards optimization of the TES protocol. Ultimately, the results will lead to improved quality of life for children with neuromuscular disorders.

Body Composition↗

Spectrum of double outlet right ventricle induced by electrical shock at the conotruncus of the embryonic chick heart: emphasis on cellular changes and evaluation of hemodynamics using Doppler.

Administration of electrical shock to the conotruncal area of embryonic chicks at developmental stage 24-27 induced a complex malformation, namely, double outlet right ventricle (DORV) of varying degrees of severity. The device used to apply electrical current to the heart was constructed using a 9-volt battery, a push-button switch, and a 100-ohm potentiometer with calibrated dial. This allowed a short pulse of known voltage to be applied through the electrodes to a selected area of the heart. Two different methods were chosen to administer electrical shock at the conotruncal area of the heart. One method utilized longitudinal application of electrical shock, and the other used horizontal application of electrical shock directly to the conotruncus. Three distinct types of DORV were found in the longitudinal (L) and the horizontal (H) electrical shock groups: 1) DORV without a ventricular septal defect (VSD), in which the dilated sinus of Valsalva of the aortic valve extends into the right ventricle. 2) DORV with a subaortic VSD, with variable degrees of pulmonary stenosis and a hypoplastic left ventricle. 3) DORV with a subpulmonic VSD, pulmonic stenosis and a hypoplastic right ventricle. Longitudinal stimulation produced a higher incidence of cardiovascular anomalies than horizontal stimulation (p = 0.01). Histological examination showed complete disappearance of myocardial fibers, myocardial degeneration, and the aggregation of protein material or glycogen within myocardial cells. Our Doppler findings demonstrate that relative to control embryos, peak velocity initially increased 3 minutes after electrical stimulation (p less than 0.01), and subsequently decreased significantly within 30 minutes (p less than 0.01). One may hypothesize that the marked initial increase of peak velocity was induced by tissue damage, which led to a narrowing of the conotruncal outflow tract. Evidence for contruncal narrowing was also reflected in percent window data (% W), which indicates the level of turbulence within a vessel. However, the decrease of peak velocity 30 minutes after stimulation might be caused by myocardial damage resulting in a diminished cardiac output. The relationship between cell death processes in the conotruncal area and DORV spectrum induced by electrical shock is discussed.

Animals↗

Electrical synapse formation disrupts calcium-dependent exocytosis, but not vesicle mobilization.

Electrical coupling exists prior to the onset of chemical connectivity at many developing and regenerating synapses. At cholinergic synapses in vitro, trophic factors facilitated the formation of electrical synapses and interfered with functional neurotransmitter release in response to photolytic elevations of intracellular calcium. In contrast, neurons lacking trophic factor induction and electrical coupling possessed flash-evoked transmitter release. Changes in cytosolic calcium and postsynaptic responsiveness to acetylcholine were not affected by electrical coupling. These data indicate that transient electrical synapse formation delayed chemical synaptic transmission by imposing a functional block between the accumulation of presynaptic calcium and synchronized, vesicular release. Despite the inability to release neurotransmitter, neurons that had possessed strong electrical coupling recruited secretory vesicles to sites of synaptic contact. These results suggest that the mechanism by which neurotransmission is disrupted during electrical synapse formation is downstream of both calcium influx and synaptic vesicle mobilization. Therefore, electrical synaptogenesis may inhibit synaptic vesicles from acquiring a readily releasable state. We hypothesize that gap junctions might negatively interact with exocytotic processes, thereby diminishing chemical neurotransmission.

Animals↗

On the mechanism of colonic motility: the electric activation theory of colonic contraction.

PURPOSE: A previous study has demonstrated that the longitudinal muscle possesses electric activity, while the circular does not (A. Shafik and A. A. Shafik, 2000, Front. Biosci. 5, b5). In the current study, we investigated the mechanism of action of the two colonic muscle coats in the motility of the gut. METHODS: Fourteen patients (43.8 years, 10 men) with left colon or rectal cancer were scheduled to have transverse colostomy as a part of their operation. The electric activity of the ascending colon was recorded by three electrodes applied to each of the circular and the longitudinal (taenia coli) muscle coats. Simultaneously, the colonic pressure was recorded before and after colonic distension. The test was repeated after longitudinal muscle anesthetization. RESULTS: Electric waves in the form of pacesetter (PPs) and action (APs) potentials were recorded from the longitudinal but not the circular muscle fibers. APs were associated with an intracolonic pressure rise. Colonic distension produced significant increase in the PPs and APs recorded from the longitudinal muscle with appearance of similar electric activity from the circular muscle. Electric activity and colonic pressure increased upon increase in the colonic distension until the balloon in the proximal part of the ascending colon moved to the transverse colon in one mass contraction. Ten minutes after longitudinal muscle anesthetization, no electric activity was recorded from the longitudinal and circular muscles upon colonic distension. CONCLUSIONS: The electric waves appear to be transmitted from the longitudinal to the circular muscle upon colonic distension. The giant migrating contractions of the colon that move the food bolus from the cecum to the transverse colon are suggested to be a function of the longitudinal muscle electric activation with gut lumen modulation by the circular fibers.

Action Potentials↗

Differential modulation of chemical and electrical components of mixed synapses in the lobster stomatogastric ganglion.

1. Two pairs of neurons in the pyloric network of the spiny lobster, Panulirus interruptus, communicate through mixed graded chemical and rectifying electrical synapses. The anterior burster (AB) chemically inhibits and is electrically coupled to the ventricular dilator (VD); the lateral pyloric (LP) and pyloric (PY) neurons show reciprocal chemical inhibition and electrical coupling. We examined the effects of dopamine (DA), serotonin (5HT) and octopamine (Oct) on these mixed synapses to determine the plasticity possible with opposing modes of synaptic interaction. 2. Dopamine increased net inhibition at all three pyloric mixed synapses by both reducing electrical coupling and increasing chemical inhibition. This reversed the sign of the net synaptic interaction when electrotonic coupling dominated some mixed synapses, and activated silent chemical components of other mixed synapses. 3. Serotonin weakly enhanced LP-->PY net inhibition, by reducing electrical coupling without altering chemical inhibition. Serotonin reduced AB-->VD electrical coupling, but variability in its effect on the chemical component made the net effect non-significant. 4. Octopamine enhanced LP-->PY and PY-->LP net inhibition by enhancing the chemical inhibitory component without altering electrical coupling. 5. Differential modulation of chemical and electrical components of mixed synapses markedly changes the net synaptic interactions. This contributes to the flexible outputs that modulators evoke from anatomically defined neural networks.

Animals↗

Impact of biologically closed electric circuits (BCEC) on structure and function.

The basis of our physical world is electrical. The unified Electromagnetic field can appear to us as particles, i.e., matter, at certain densities of wavelengths. A close interrelation therefore exists between matter and electric energy. This knowledge is extensively utilized in technology. Various tools and instruments are electrically powered, utilizing the exceedingly important principle of closed electric circuits. Corresponding closed electric circuits and functions also exist in biology but are more sophisticated and complex. Unfortunately, these aspects are almost unrecognized. The principle of Biologically Closed Electric Circuits (BCEC) and some of their structural and functional effects are described. The Vascular-Interstitial Closed Circuit (VICC) is one specific BCEC system. It functions as a circulatory system in addition to the mechanical circulation. Its efficiency partly depends on its capacity to provide bidirectional transport of ions. The VICC is an in vivo electrophoretic-dielectrophoretic system that is powered by metabolic energy or injury currents. A VICC activation leads to transports of metabolites, new structuring and healing of an injured tissue. Examples are also presented of the process of healing. An abnormal, e.g., prolonged activation of VICC may also induce pathology. Neoplastic formation of cells and tissue can also be healed by the use of artificially applied electrophoresis or an artificially applied electric field as will be described. Our world once developed from electrical energy. This is probably the reason why the BCEC systems make primary differences between nonbiological and biological matter.

Animals↗

Comparison between laser and electrical ablation of ventricle in dogs: hemodynamic, pathologic and electrocardiographic observations.

To characterize and compare the pathologic, hemodynamic and electrocardiographic changes of both transcatheter laser and electrical energy on ventricle, 36 subendocardial myocardium lesions were induced at energy 60, 120 and 240 Joules by either transcatheter laser irradiation or electrical shock in 7 anesthetized dogs. The following results were observed: 1) Both laser and electrical ablation on myocardium created nonhomogeneous myocardium injury, but laser ablation caused mainly focal tissue vaporization and necrosis, while electrical shock induced widespread tissue degenerations; 2) Both laser and electrical induced-lesion dimensions increased parallel to the total dosage of energy; 3) Laser ablation caused mainly (90%) single ventricular premature beats and 86% of them occurred within the first minute after energy discharged, while ventricular tachycardias were found in any electrical energy groups; ventricular fibrillations occurring during laser and electrical ablation were 5% and 13% respectively (P < 0.01); 4) A decrease in aortic blood pressure and an increase in central venous pressure induced by laser ablation were significantly less than that produced by the same amount of electrical energy (P < 0.01). Our preliminary results have shown that transcatheter laser ablation has great potential for becoming a practical method in the management of refractory tachycardias.

Animals↗