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J R Windle

Publications and source records attributed to J R Windle.

25 records · Page 2Linked to original sources
PubMed1989

Fast Fourier transformation of the entire low amplitude late QRS potential to predict ventricular tachycardia.

Signal-averaged electrocardiograms (X, Y and Z leads) were acquired from 24 patients with coronary artery disease and recurrent ventricular tachycardia, 24 control patients with coronary artery disease and 23 normal subjects to assess the discriminant value of fast Fourier transformation of the entire late potential period of the QRS complex. Analysis of the vector magnitude in the temporal domain (25 to 250 Hz bandpass filters) measured high frequency QRS duration, the duration of terminal signals less than 40 microV and the root mean square voltage of the last 40 ms. Late potentials were defined as terminal signals greater than 25 Hz that were less than 40 microV. Analysis in the frequency domain used a 120 ms window that encompassed (had onset with) all of the late potential, but the mean value was first subtracted to eliminate a direct current component. High frequency spectral areas (60 to 120 Hz) and the percent high frequency (100 x [60 to 120 Hz/0 to 120 Hz]) were calculated. Results in both temporal and frequency domains were similar in control patients with coronary artery disease and normal subjects. Patients with ventricular tachycardia had a longer high frequency QRS complex (p less than 0.0001) and longer high frequency terminal signals less than 40 microV (p less than 0.0004), but not significantly lower voltage in the last 40 ms. The most useful temporal domain measurement was high frequency QRS duration (if greater than or equal to 120 ms, odds ratio = 8.2). Patients with ventricular tachycardia had increased high frequency spectral areas (p less than 0.0002) in the late potential, and the percent high frequency was especially increased (p = 0.0000; if percent high frequency greater than 3.1%, odds ratio = 18.4). The odds ratio and the area under the receiver operating characteristic curve were both greater for percent high frequency than for high frequency QRS duration (p less than 0.03). All patients with ventricular tachycardia had a high frequency QRS complex greater than or equal to 107 ms or percent high frequency greater than or equal to 3.1% (sensitivity 100%). For a high frequency QRS complex greater than or equal to 107 ms and percent high frequency greater than or equal to 3.1%, specificity was 96%. Therefore, high frequencies in late potentials, not their duration or reduced voltage, most usefully identify patients with coronary artery disease who are prone to ventricular tachycardia.

Adult↗
PubMed1986

Subthreshold conditioning stimuli prolong human ventricular refractoriness.

This study tested whether a subthreshold stimulus (Sc) inserted before a premature stimulus prolonged the right ventricular effective refractory period in humans, and whether the degree of effective refractory period lengthening was influenced by heart rate, Sc current intensity or Sc pulse duration. Sc at current intensity 10 mA and pulse width 2 ms prolonged mean effective refractory period from 255 ms to 277 ms (p less than 0.001, n = 20). The increase in effective refractory period was similar in 6 patients studied at pacing cycle lengths 600 (259 to 289 ms) and 400 ms (236 to 258 ms). When Sc current intensities were varied at 2, 5 or 10 mA at a constant pulse duration of 100 ms the effective refractory period progressively prolonged by 6, 40 and 81 ms respectively (p less than 0.02, n = 6). The pulse duration of Sc at a constant current of 10 mA significantly influenced effective refractory period prolongation. With Sc pulse durations of 2, 10, and 100 ms the effective refractory period prolonged by 16, 33 and 66 ms respectively (p less than 0.01, n = 7). Thus, subthreshold impulses prolong the effective refractory period in human right ventricular myocardium. The prolongation of effective refractory period depended on Sc current intensity and pulse duration but was independent of heart rate at the cycle lengths tested. The use of subthreshold stimuli as antiarrhythmic therapy may be feasible in some patients.

Adult↗
PubMed1986

Determination of the earliest site of ventricular activation in Wolff-Parkinson-White syndrome: application of digital continuous loop two-dimensional echocardiography.

Surgical and transcatheter ablation of accessory atrioventricular (AV) connections (Wolff-Parkinson-White syndrome) requires accurate localization of the accessory pathway. In a canine model of endocardial pacing, a continuous loop two-dimensional echocardiographic technique was developed for determining the earliest site of ventricular activation. This technique was then used to localize accessory AV connections in patients. Echocardiographic images were acquired on videotape and converted to a digital continuous loop format, from which the earliest site of systolic motion was determined. In six dogs, using six distinct endocardial sites, two blinded observers accurately identified the earliest site of ventricular activation in 31 (86%) of 36 and 32 (89%) of 36 locations. Determination of the earliest site of ventricular activation with the continuous loop digital technique was superior to standard analog analysis in overall accuracy (p less than 0.02) and in intraobserver variability (p less than 0.004). After validation of this technique, 21 patients with 22 accessory AV connections with anterograde conduction were studied. The earliest site of mechanical activity was determined during sinus (10 patients) or atrial paced (11 patients) rhythms by two blinded observers and compared with electrophysiologic mapping and surface electrocardiograms. Digitally processed echocardiograms correctly localized the earliest site of ventricular activation in 18 of 22 connections and predicted an adjacent location in the remaining 4.(ABSTRACT TRUNCATED AT 250 WORDS)

Adolescent↗
PubMed1984

Pacemaker insertion for prehospital bradyasystolic cardiac arrest.

We investigated the use of transvenous (TV) and transmyocardial (TM) pacemakers in the emergency department (ED) in 54 adult patients (42 men and 12 women) with bradyasystolic cardiac arrest. Down time prior to cardiopulmonary resuscitation (CPR) was 4.8 +/- 4.3 minutes. Time in the ED prior to pacer insertion was 26.9 +/- 17.7 minutes. Electrical capture rate was 63%. Pulse developed in 5%. Only 1.2% were admitted, and none was discharged alive. There was no significant difference in capture rate for TV versus TM pacers or in capture rate whether the pacer was inserted early or late after ED arrival. We conclude that ED pacer insertion for such patients does not alter survival rates.

Adult↗
PubMedDate not supplied

False-negative findings in pericardial effusion using M-mode echocardiography.

M-mode echocardiography in a 3-year-old patient with suspected pericardial effusion was negative for the presence of an effusion. A subsequent 2-dimensional echocardiogram demonstrated a large effusion lateral to the right atrium and right ventricle. The reasons for the false-negative M-mode echocardiogram and a discussion of the literature are presented.

Child, Preschool↗