摘要:

Radiofrequency Ablation of Supraventricular Arrhythmias,Introduction: Several reports iiave demonstrated that radiofrequency catheter ablation provides effective control of a variety of supraventricular tachycardias. However, the efficacy, complications, risk of arrhythmia recurrence, and follou‐up survival analysis have not been reported in a large series of consecutive patients with supraventricular arrhythmias with diverse electrophysiologic mechanisms. This report details the results of radiofrequency catheter ahiation in 760 consecutive patients (386 males, 374 females) with a wide variety of supraventricular tachycardias treated at one center.Methods and Results: Arrhythmias were associated with the presence of an accessory pathway i n 363 patients (384 accessory pathways), including four patients with Mahaim fibers and eight patients with the permanent form of junctional reciprocating tachycardia. The mechanism of the clinical arrhythmia was AV nodal reentrant tachycardia in 245 patients, and a primary atrial tachycardia in 20 patients (ectopic atrial tachycardia in 16 patients and sinus nodal reentry in 4 patients). Ablation of the reentrant circuit of atrial flutter within the right atrium was attempted i n 13 patients. AV node ahiation and permanent pacemaker implantation were performed in 119 patients with medically refractory atrial fihrillation or flutter. Radiofrequency catheter ahiation was successful in 346 of 363 patients (95.3%, CI 93.I%–97.5%) with accessory pathways (367 of 384 pathways, 95.6%, CI 93.5%–97.6%) with a complication rate of 1.1% and a recurrence rate of 5.5%. Successful accessory pathway ablation was achieved for 179 of the first 192 pathways treated (93.2%, CI 89.7%–96.6%) and increased to 188 of 192 pathways (97.9%, CI 95.9%–99.9%) over the second half of the series. AV nodal reentry was successfully abolished in 244 of 245 patients (99.6%, CI 98.8%–100%) by selective ablation of the slow pathway in 234 patients and the fast pathway in 10 patients. The complication rate in this group was 2.0% with a recurrence rate of 6.5%. All 20 primary atrial tachycardias were successfully ablated with no complications and a recurrence rate of 15%. The reentrant circuit of atrial flutter was ahlated successfully in 10 of 13 patients (77%) with recurrent atrial flutter in one additional patienl. Complete AV block was achieved in 117 of 119 (98.3%, CI 96.0%–100%) patients with atrial fibrillation or flutter treated hy AV nodal ablation with a complication rate of 0.8% and recurrence of AV conduction in 6%. The median duration of fluoroscopy exposure for the population was 23.4 minutes. The overall primary success rate for the entire population was 97.0% (737 of 760 patients, CI 95.8%–98.2%).Conclusion: Thus, the results of this large series of patients demonstrates the safety and efiicacy of radiofrequency ahiation for the treatment of a wide variety of supraventricular arrhythmias. It also appears that increasing experience with these procedures increases the rate of successful ahlation and decreases the risk o

ISSN:1045-3873    

DOI:10.1111/j.1540-8167.1993.tb01277.x

出版商:Blackwell Publishing Ltd    

年代:1993

数据来源: WILEY

ISSN:1045-3873    

DOI:10.1111/j.1540-8167.1993.tb01278.x

出版商:Blackwell Publishing Ltd    

年代:1993

数据来源: WILEY

摘要:

Overdrive Stimulation and Functional Reentry,introduction:The purpose of the experiments described in this article was to investigate the effects of overdrive stimulation on functional anisotropic reentrant circuits causing ventricular tachycardia in infarcted canine ventricles. We determined how overdrive stimuli affect reentrant circuits to alter characteristics of the tachycardia.Methods and Results:Activation patterns were determined In mapping excitation with a 192 bipolar electrode array. We found that overdrive stimuli could activate the circuits with the same pattern as the reentrant wavefront and that after overdrive stopped either the last or the next to last stimulated wavefront continued propagating through the circuit as a new reentrant impulse and tachycardia continued. When the circuit was not altered after overdrive, the exit route that the stimulated wavefront took from the circuit to activate the rest of the ventricles was also not altered and the tachycardia after overdrive had the same cycle length and QRS morphology as prior to overdrive. In some experiments, however, the overdrive stimuli did not follow the original reentrant pathway but led to the formation of a different circuit with a different exit route to the ventricles. As a result, after overdrive stimulation tachycardia had a different QRS morphology and cycle length than prior to stimulation. When the new circuit after overdrive was small and the revolution time of the reentrant impulse around the circuit was short, fibrillation occurred.Conclusion:Functional reentrant circuits can either be maintained or altered after a period of overdrive stimulation. The results explain many of the effects that have been seen during overdrive stimulation of clinical ventricular tachycardia.

ISSN:1045-3873    

DOI:10.1111/j.1540-8167.1993.tb01279.x

出版商:Blackwell Publishing Ltd    

年代:1993

数据来源: WILEY

摘要:

Reentry in Anisotropic Myocardium.Introduction:We investigated numerically the effects of the rotation of finer axis orientation through the myocardial wall on wave propagation.Methods and Results:We show that because of this rotation and inherent discrete properties of myocardium, a premature stimulus can create unidirectional conduction block leading to reentry.Conclusion:The dynamics of the subsequent reentrant patterns are complicated by the presence of rotational anisotropy, as the center of reentry drifts, and the reentry terminates in finite time when it collides with the domain boundary.

ISSN:1045-3873    

DOI:10.1111/j.1540-8167.1993.tb01280.x

出版商:Blackwell Publishing Ltd    

年代:1993

数据来源: WILEY

摘要:

Calcium Current in Human Heart.Introduction:Significant species‐, issue‐, and age‐dependent differences have been described for the L‐type calcium current (ICa). Therefore, extrapolation data obtained from the many animal models to human cardiac physiology is difficult. In this study, we have characterized the voltage‐dependent properties of ICafrom pediatric and adult, atrial and ventricular human heart tissue.Methods and Results: ICa, was measured in single human heart muscle cells using the “whole cell,” voltage clamp method. Single myocytes were isolated from myocardial specimens obtained intraoperatively from both pediatric and adult patients (ages 3 months to 75 years) undergoing cardiac surgery. Cells obtained for these experiments appeared to be healthy; the resting potential was between ‐80 and ‐85 mV. The action potential shape and duration and current‐voltage relationship for 1Cawere similar to that reported by others for human heart cells. The steady‐state activation variable, dxwas found to be similar in both pediatric atrial and ventricular cells but shifted approximately 5 mV negative in the adult atrial and ventricular cells. I, of all cells displayed biex‐ponential inactivation and steady‐state inactivation was incomplete at positive potentials (steady‐state inactivation curves turned up at positive potentials) consistent with inactivation arising from voltage‐dependent and calcium‐dependent processes as reported in heart cells from many species. The potential of maximal inactivation was more negative for adult cells (around ‐10 mV) than pediatric cells (around 0 mV). Estimates of the calcium “window” current, using a modified Hodgkin‐Huxlcy model, could explain measured differences in action potential shape and duration.Conclusion:Human cardiac I, can be investigated using whole cell, voltage clamp methods and a modified Hodgkin‐Huxley model. Quantitative characterization of many of the properties of ICain human heart tissue suggests that important species differences do exist and that further investigations are required to characterize the dependence of inactivation on [Ca2+]iin human heart cells. Since the array of characteristics of ICain different species varies, the study of human myocardial cells per se continues to be importan

ISSN:1045-3873    

DOI:10.1111/j.1540-8167.1993.tb01281.x

出版商:Blackwell Publishing Ltd    

年代:1993

数据来源: WILEY

摘要:

Potential Patterns in a 3‐D Cardiac Depolarization Model,introduction:We present simulations of extracellular potential patterns elicited by delivering ectopic stimuli to a parallelepipedal slab of ventricular tissue represented as an anisotropic bidomain incorporating epiendocardial fiber rotation.Methods and Results:Simulations were based on an eikonal model that determines wave‐front shapes throughout the slab at every time instant during the depolarization phase, coupled with an approximate model of the action potential profile. The endocardial face of the slab was in contact with blood and the composite volume was surrounded by an insulating medium. The effect of a simplified Purkinje network was also studied. Results: (1) For all pacing depths, except endocardial pacing, a central negative area and two potential maxima were observed at QKS onset in all intramural planes parallel to the cpicardium. In all planes, the axis joining the two maxima was approximately aligned with the direction of fibers in the plane of pacing. Endocardial pacing generated a different pattern, but only when blood was present; (2) During later stages of excitation, outflowing currents (from the wavefront toward the resting tissue) were always emitted, at all intramural depths, only from those portions of the wavefront that spread along fibers. At any given instant, the position of the two potential maxima in a series of planes parallel to the epicardium and intersecting the wavefront rotated as a function of depth, following the rotating direction of intramural fibers. Purkinje involvement modified the above patterns.Conclusion:Epicardial and endocardial potential maps provided information on pacing site and depth and on subsequent intramural propagation by reflecting the clockwise or counterclockwise rotation of the deep positivity. Results may be applicable to epicardial and endocardial potential maps recorded at surgery or from endocavitary pro

ISSN:1045-3873    

DOI:10.1111/j.1540-8167.1993.tb01282.x

出版商:Blackwell Publishing Ltd    

年代:1993

数据来源: WILEY

摘要:

Sequential Bilateral BBB During Dofetilide.Introduction:I in mechanism of wide QRS complex tachycardias during dofetilide infusion was studied in a patient with atrial fibrillation.Methods and Results:Endocardial recording from the intraventricular conduction system showed that dofetilide caused “classic” aberrant conduction (Ashman phenomenon, typical QKS morphology) at high prematurity ratios (preceding interval = 1.78 X coupling interval 290), thus mimicking ventricular ectopy. In addition, there was frequent sequential bilateral bundle branch block, caused by a significant difference in preceding bundle‐to‐bundle intervals (mean difference ± 1 SD: 74 ± 26 msec).Conclusion:The present findings may prove helpful in the clinical assessment of wide QKS complex rhythms after dofetilide and possibly other “pure” Class III an

ISSN:1045-3873    

DOI:10.1111/j.1540-8167.1993.tb01283.x

出版商:Blackwell Publishing Ltd    

年代:1993

数据来源: WILEY

摘要:

Preexcitation After Catheter Ablation.Introduction:The basis for anterograde or retrograde unidirectional block of accessory pathways still remains a controversial issue.Methods and Results:Four of 19 consecutive patients (1 mule, 3 Female; ages 27 to 34 years) who underwent transcatheter ablation of concealed accessory pathways developed manifest preexcitation after the ablation. The location of the concealed accessory pathways in these four patients were right lateral, left posteroseptal, left posterolateral, and left lateral. Radiofrequency current was used in three of the four patients and high energy direct current in one patient. After ablation, manifest preexcitation was observed in these four patients for the first time. Manifest preexcitation developed immediately after ablation in two of the four patients and after 4 and 14 days in the other two. Detailed endocardial mapping revealed that the manifest preexcitation originated from the same location as the concealed pathways. Subsequently, catheter ablation was successfully performed in three of the four patients using radiofrequency current. One patient underwent successful surgical ablation. No recurrence of preexcitation was observed during a follow‐up period of 9 to 38 months. All patients remained free of arrhythmias.Conclusion:The basis for this unexpected emergence of preexcitation in these patients with only retrograde conducting accessory pathways deserves further investigation. Although not compared in the present study, this phenomenon has not been reported in patients who underwent surgical interruption of accessory pathways. We postulate that a lesion at the site of insertion of the accessory pathway had modified the anterograde conduction capacit

ISSN:1045-3873    

DOI:10.1111/j.1540-8167.1993.tb01284.x

出版商:Blackwell Publishing Ltd    

年代:1993

数据来源: WILEY

摘要:

Spontaneous Myocardial Calcium Oscillations. The physiological oscillation of cytosolic that underlies each heart heat is generated by the sarcoplasmic reticulum (SK) in response to an action potential (AP) and occurs relatively synchronously within and among cells. When the myocardial cell and SR loading become sufficiently high, the SK can also generate spontaneous, i.e., not triggered by sarcolemmal depolarization, oscillations The purpose of this review is to describe properties of S‐CaOs in individual cells, myocardial tissue, and the intact heart, and to examine the evidence that may link S‐CaOs to the initiation or maintenance of ventricular fibrillation (VF). The SR Ca2+release that generates S‐CaOs occurs locally within cells and spreads within the cell via Ca2+‐induced Ca2+release. The localized increase in cytosolic [Ca2+] due to S‐CaOs may equal that induced by an AP and causes oscillatory sarcolemmal depolarizations of cells in which it occurs. These oscillatory depolarizations are due to activation of the Na/Ca exchanger and of nonspecific cation channels. Asynchronous occurrence of diastolic S‐CaCs among cells within the myocardium causes inhomogencity of diastolic SR loading; this leads lo inhomogeneity of the systolic cytosolic [Ca2+] transient levels in response to a subsequent AP, which leads to heterogeneity of AP repolarization, due to heterogeneous modulation of the exchanger, nonspecific cation channels, and of the L‐type channel. In a tissue in which asynchronous S‐CaOs are occurring in diastole, the subsequent AP temporarily synchronizes SR Ca2+loading and release within and among cells. Varying extents of synchronized S‐Caos then begin to occur during the subsequent diastole. The partial synchronization of this diastolic S‐CaOs among celts within myocardial tissue produces after contractions and diastolic depolarizations. When S‐CaOs are sufficiently synchronized, the resultant depolarizations summate and can be sufficient to trigger a spontaneous AP. S‐CaOs occurrence within some cells during a long AP plateau also modulates the removal of voltage inactivation of L‐type channels and increases the likelihood for “early after depoializations” to occur in myocardial tissue. S‐CaOs have an apparent modulatory role in the initiation at VF in the CV+overload model and in the reflow period following ischemia. Likewise, in non‐a priori Ca2+overloaded hearts, S‐CaOs modulate the threshold for VF induction (induced typically by alternating current) but may not be essential for VF induction. The role of S‐CaOs in maintenance of VF in these VF models is less clear: to date there is no evidence that inhibition of S‐CaOs can abolish VF once it has been established. The precise definition of the role of S‐CaOs in the initiation

ISSN:1045-3873    

DOI:10.1111/j.1540-8167.1993.tb01285.x

出版商:Blackwell Publishing Ltd    

年代:1993

数据来源: WILEY

摘要:

Nonsustained Ventricular Tachycardia. Nonsustained ventricular tachycardia (NSVT) is an arrhythmia not often associated with symptoms; however, its occurrence in patients with structural heart disease is a prognostic indicator of an increased risk of mortality and sudden death. The management of asymptomatic patients with NSVT should first attempt to identify which patients are at highest risk for cardiac arrest, and second, devise a treatment that can reduce the incidence and/or mortality of cardiac arrest in this group. In patients with chronic coronary artery disease (CAD) and NSVT, programmed electrical stimulation identifies both a low and high risk group with respect to occurrence of ventricular arrhythmias. The negative predictive value of programmed electrical stimulation in patients with CAD and NSVT has been well established; however, uncertainty remains as to the optimal therapy for CAD patients with inducible ventricular arrhythmias. A number of reports suggest that patients whose inducible ventricular arrhythmias are rendered noninducible with antiarrhythmic drugs have a much lower risk of sudden death. It is yet to be resolved whether arrhythmias rendered noninducible identify a subgroup at low risk for cardiac arrest, independent of treatment. There is some evidence to suggest that the frequency of NSVT in patients with nonischemic dilated cardiomyopathy identifies a group at higher risk of sudden death. Programmed electrical stimulation adds little in helping to identify which of these patients are most likely to have cardiac arrest. The presence of NSVT in asymptomatic patients with hypertrophic cardiomyopathy may identify a group at higher risk for cardiac arrest. Further clinical studies are needed to define the best management strategy for NSVT in different types of structural heart disease.

ISSN:1045-3873    

DOI:10.1111/j.1540-8167.1993.tb01286.x

出版商:Blackwell Publishing Ltd    

年代:1993

数据来源: WILEY