摘要:

Beat‐by‐Beat Recording of Terminal QRS.Introduction:Beat‐by‐beat recordings of quasiorthogonal leads were performed in 82 normal subjects (35 male and 47 female) with normal standard electrocardiograms (ECGs) in order to: (1) establish normal values for parameters that were similar to those used in signal‐averaged ECG; (2) compare these data with the signal‐averaged ECG; and (3) assess the noise level in beat‐by‐beat recording.Methods and Results:Low‐noise recordings were achieved by special instrumentation, preparation of subjects, and screening recording sites for an optimal magnetic field at 60 Hz or its harmonics without using a shielded room. Using a 40‐Hz bidirectional high‐pass filter, 95% of normal subjects had a beat‐by‐beat duration of vector magnitude complex ≤ 107 msec, a duration of low‐amplitude signal under 40 μV ≤ 37 msec, and a root mean square (RMS) voltage of last 40 msec ≥ 24.1 μV. Significant difference was found in duration of vector magnitude complex (P0.3). Although the beat‐by‐beat and signal‐averaged data were highly correlated in all three parameters, the beat‐by‐beat recordings exhibited a shorter duration of low‐amplitude signal (P<0.0004) and a higher RMS voltage of last 40 msec (P0.2). The mean RMS noise in the vector magnitude lead from the normal group was 1.52 ± 0.65 μV (mean ± SD) while over 80% of the subjects had RMS noise under 1 μV in an individual lead.Conclusion:The normal values from beat‐by‐beat recordings are correlated to but different from those of signal‐averaged ECGs. Every‐beat high‐resolution recordings of terminal QRS are stable and reproducible in normal subjects. Also, the use of individual lead (s) with lower noise is recommended for better detection of low‐level terminal QRS

ISSN:1045-3873    

DOI:10.1111/j.1540-8167.1992.tb01100.x

出版商:Blackwell Publishing Ltd    

年代:1992

数据来源: WILEY

摘要:

Dantrolene‐Induced Purkinje Fiber Action Potential Prolongation.Introduction:The purpose of this study was to investigate the influence that the mode of drug administration and preparation geometry exerted on the ability of dantrolene to prolong sheep and canine Purkinje fiber (PF) action potential duration (APD).Methods and Results:Sheep PF with attached muscle were superfused with dantrolene 3–5 μg/mL for 90 minutes (group A), while identical preparations were incubated in dantrolene 33.3 μg/mL for 5 minutes, then washed for 60 minutes (group B). Additional preparations were incubated with dantrolene (as in group B) for 5 minutes, then washed for 60 minutes: sheep PF (group C); sheep PF attached to muscle at one end but tied off from the muscle (group D); PF as in group D with a freshly cut branch (group E); freshly cut canine PF (group F); and sheep PF attached to muscle at one end were placed in a partitioned bath and each side incubated with dantrolene separately and then washed for 60 minutes (group G). Superfusion (group A) or incubation (group B) with dantrolene prolonged PF APD by 93% and 83%, respectively (NS). Sealed PF of groups C and D: APD prolonged by 10% and 34%, respectively (compared to A, P<0.01). Freshly cut PF in groups E and F: APD lengthened by 78% and 74%, respectively (compared to A, NS). Dantrolene administration to the PF side and to the muscle side in group G prolonged the PF APD on either side similarly.Conclusion:Thus, dantrolene is effective by prolonged superfusion or short incubation. Dantrolene penetrates sealed PF poorly, but readily penetrates freshly cut PF or ventricular muscle. In vitro geometry greatly influences dantrolene's effect on Purkinje fibers. (J Cardiovasc Electrophysiol, Vol. 3, pp. 119–127, Apr

ISSN:1045-3873    

DOI:10.1111/j.1540-8167.1992.tb01101.x

出版商:Blackwell Publishing Ltd    

年代:1992

数据来源: WILEY

摘要:

Early Electrophysiologic Changes in Acute Ischemia.Introduction:The purpose of this study was to match changes in conduction velocity, refractoriness, and wavelength during acute regional ischemia with initiation of ventricular fibrillation.Methods and Results:In 30 isolated, Langendorff‐perfused pig hearts we measured refractory period duration and conduction velocity in ventricular myocardium during the first minutes of regional ischemia in an attempt to determine the minimal changes in these parameters related to the occurrence of ventricular fibrillation (VF). In addition, we wanted to evaluate whether wavelength, i.e., the product of conduction velocity and refractory period, was a useful parameter to predict the occurrence of arrhythmias, as has been shown to be the case for atrial arrhythmias.1The refractory period increased significantly after 1 minute of ischemia at basic cycle length and after one and two premature beats. Longitudinal and transverse conduction velocities varied with ischemic time. Compared to the preocclusion value, the longitudinal conduction velocity decreased significantly, but only after 2 minutes of ischemia and at basic cycle length. Wavelength was the least sensitive parameter for ischemia: neither in the longitudinal nor in the transverse direction did it change significantly even during 5 minutes of ischemia. VF was never induced by applying a single premature stimulus within the ischemic area. It occurred in 33% of the occlusions when three successive premature stimuli were delivered from within the ischemic zone, and in 100% when they were applied to the nonischemic myocardium. Whenever fibrillation was induced, it occurred within 3 minutes following coronary occlusions. Wavelength, neither before nor after coronary occlusion, could predict whether VF would occur. The only difference between hearts that fibrillated by stimulation of the ischemic myocardium and those that did not was that, in the first group, the refractory period at the site of stimulation prolonged significantly less than in the no‐VF group. Since electrophysiologic changes within the ischemic zone are inhomogeneous,2an attempt was made to measure simultaneously at 52 sites the onset of inhomogeneity by determining the average interval between local depolarization during VF. This so‐called VF interval is an index of local refractoriness.3The coefficient of variation of the VF interval, taken as an index of spatial dispersion in refractoriness, increased significantly 1 minute after occlusion in the border zone and 2 minutes after occlusion in the central ischemic area.Conclusion:In conclusion, wavelength is not a useful parameter to predict the occurrence of VF in hearts with regional ischemia because of the inhomogeneity in refractoriness, which develops within 2 minutes of ischemia. VF occurs when hearts are stimulated from sites with relatively short refractory periods, either within or outside the ischemic zone. (J Cardiovasc Electrophysiol, Vol. 3, pp. 128–140, Apr

ISSN:1045-3873    

DOI:10.1111/j.1540-8167.1992.tb01102.x

出版商:Blackwell Publishing Ltd    

年代:1992

数据来源: WILEY

摘要:

Radiofrequency Ablation of Multiple Accessory Pathways. A 19‐year‐old patient is described having three accessory atrioventricular pathways. All three pathways were ablated using radiofrequency current in a single electrophysiologic investigation. (J Cardiovasc Electrophysiol, Vol. 3, pp. 141–149, April

ISSN:1045-3873    

DOI:10.1111/j.1540-8167.1992.tb01103.x

出版商:Blackwell Publishing Ltd    

年代:1992

数据来源: WILEY

ISSN:1045-3873    

DOI:10.1111/j.1540-8167.1992.tb01104.x

出版商:Blackwell Publishing Ltd    

年代:1992

数据来源: WILEY

摘要:

Radiofrequency Catheter Ablation. Radiofrequency catheter ablation techniques are becoming increasingly accepted as the therapy of choice for selected patients with symptomatic arrhythmias. The ability to titrate the power output using radiofrequency current has allowed these ablative techniques to be applied safely in a variety of arrhythmias. In many institutions, radiofrequency catheter ablation has now become standard therapy for controlling medically refractory atrial arrhythmias using atrioventricular (AV) junction ablation and for curing AV nodal reentrant tachycardia and supra ventricular tachycardia due to accessory AV connections. This technology is also being used to treat some forms of ventricular tachycardia such as bundle branch reentry ventricular tachycardia, ventricular tachycardia in structurally normal hearts, and with limited success in patients with ventricular tachycardia and coronary artery disease. Advancements in catheter design and energy delivery systems may further expand the use of this form of therapy. (J Cardiovasc Electrophysiol, Vol. 3, pp. 173–186, April 199

ISSN:1045-3873    

DOI:10.1111/j.1540-8167.1992.tb01106.x

出版商:Blackwell Publishing Ltd    

年代:1992

数据来源: WILEY

摘要:

Electropbysiology of the Sinus Node. Differentiation of normal from abnormal sinus nodal function is frequently difficult because the electrocardiographic and electrophysiologic presentations of abnormal and normal sinus nodal function are quite diverse. The autonomic nervous system greatly influences sinus nodal function, making this differentiation even more complicated. Data obtained from the recording of sinus nodal electrogram in animals and humans have helped in elucidating changes in automaticity and conduction of the sinus node. In this review, we provide examples of rhythms related to normal and abnormal sinus nodal function. (J Cardiovasc Electrophysiol, Vol. 3, pp. 187–197, April 199

ISSN:1045-3873    

DOI:10.1111/j.1540-8167.1992.tb01107.x

出版商:Blackwell Publishing Ltd    

年代:1992

数据来源: WILEY