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Biomedical subjects

J M Jenkins

Publications and source records attributed to J M Jenkins.

At least 127 records · Page 7Linked to original sources
PubMed1990

Observations of the microwave emission of Venus from 1.3 to 3.6 cm.

Laboratory measurements of Steffes (1986) have suggested that the intensity and shape of the microwave spectrum of Venus might be especially sensitive to the subcloud abundance of constituents such as SO2 and gaseous H2SO4. It was likewise suggested that some variations of the shape of the emission spectrum might occur between 1.5 and 3 cm (10 to 20 GHz), a wavelength range which had previously only been sparsely observed. As a result, coordinated observations of Venus emission were conducted at four wavelengths between 1.35 cm (22.2 GHz) and 3.6 cm (8.42 GHz) using the 43-m NRAO antenna at Green Bank, West Virginia, and the 64-m antenna at NASA's Deep Space Communication Complex, Goldstone, California. In this paper, we report the methodology and results of these observations, and compare the results with other observations and with calculated emission spectra. We conclude that the observed emission spectrum is consistent with an average subcloud abundance of gaseous H2SO4 in equatorial and midlatitude regions which is approximately 5 ppm. It is suggested that additional measurements of atmospheric microwave opacity be made with the Pioneer-Venus Orbiter Radio Occultation experiment to search for temporal and spatial variations in gaseous H2SO4 abundance in the Venus atmosphere. An upper limit for the subcloud abundance of SO2 is also determined.

Astronomy↗
PubMed1990

Extended profundoplasty to minimize pelvic and distal tissue loss.

Multiple levels of aortoileofemoral occlusive disease may necessitate profundoplasty or extension of the outflow anastomosis to insure pelvic and distal arterial perfusion. During the period 1978 through 1988, 1637 patients underwent elective aortic reconstruction for aneurysmal or occlusive disease. One hundred forty-five had profundoplasty performed to ensure adequate outflow. Associated disease was common with 88 (60%) patients having arteriosclerotic heart disease and chronic obstructive pulmonary disease (COPD) present in 89 (61%) patients. Hypertension and extracranial occlusive disease was found in 68 (46%) and 56 (38%) patients, respectively. The superficial femoral artery was occluded in 108 (74%) patients, while in 17 (12%) the profunda femoris was the only patent artery in the groin. Death occurred in nine patients (6.2%). Three were due to arrhythmias or myocardial infarction and ischemic colitis was the cause of death in two. Renal failure, sepsis, aspiration and cerebral anoxia, and disseminated intravascular coagulopathy accounted for one each. Five graft limbs failed. Amputation was required in one patient, while thrombectomy or distal bypass restored flow in four patients. Seventeen graft limbs in 136 patients occluded during the follow-up period. Distal bypass was successful in four and amputation was required in the fifth patient. Extension of the profundoplasty restored flow in nine limbs, while thrombectomy alone was successful in one. Bilateral amputation was required in one patient with poor run off and insufficient autogenus venous tissue. One hundred fourteen (78.6%) of the 145 patients survived 10 years with patency in 268 of the original 290 limbs at risk (92.4%). Profundoplasty in these patients with multilevel disease seems to extend the long-term patency of aortofemoral grafts and allows return to a normal life-style.

Anastomosis, Surgical↗
PubMed1990

Factors protecting children living in disharmonious homes: maternal reports.

This study investigated factors which were protective to children living in disharmonious homes. The sample was drawn from a representative sample of children aged 9 to 12 who took part in a previous general population study. Semi-structured interviews with both parents were used to assess the quality of the parental marriage. Mothers provided information on children's emotional and behavioral problems and putative protective factors. Fifty-seven families were in the disharmonious marriage group and 62 were in the harmonious marriage group. Putative protective factors, hypothesized to be beneficial for children, were either an aspect of social support or related to children's activities. Data were analyzed using a two-way analysis of variance with parental marriage and the putative protective factor as main effects. A differentiation was made between protective factors which interacted with parental marriage and those that acted independently. Factors which interacted with the quality of parental marriage were children having a relationship with an adult outside the family, an activity for which they received much positive recognition, and good sibling relationships. The parent-child relationship was associated with children's disturbance in both harmonious and disharmonious homes.

Achievement↗
PubMed1990

The Bin Area Method: a computationally efficient technique for analysis of ventricular and atrial intracardiac electrograms.

Recent studies have reported a significant false positive rate in delivery of therapy by implantable antitachycardia devices utilizing detection algorithms based on sustained high rate. More selective decision schemes for the recognition of life-threatening arrhythmias have been recently proposed that use analysis of the intrinsic electrogram rather than rate alone. Morphological discrimination of abnormal electrograms using correlation waveform analysis (CWA) has been proposed as an effective method of intracardiac electrogram analysis, but its computational demands limit its use in implantable devices. A new method for intracardiac electrogram analysis, the bin area method (BAM), was created to detect abnormal cardiac conduction with computational requirements of one-half to one-tenth those of CWA. Like CWA, BAM is a template matching method that is sensitive to conduction changes revealed in the electrogram morphology and is independent of amplitude and baseline fluctuations. Performance of BAM and CWA were compared using bipolar right ventricular and right atrial electrode recordings from 47 patients undergoing clinical cardiac electrophysiology studies. Nineteen patients had 31 distinct monomorphic ventricular tachycardias (VTs) induced (group I), thirteen patients had paroxysmal bundle branch block of supraventricular origin (BBB) induced (group II), and 19 patients had retrograde atrial activation during right ventricular overdrive pacing (group III). (One patient was common to all three groups, and two patients were common to groups II and III.) Using the ventricular electrogram, both BAM and CWA distinguished VT from sinus rhythm in 28/31 (90%) cases, and BBB from Normal Sinus Rhythm (NSR) in 13/13 (100%) patients. Using the atrial electrogram, both BAM and CWA distinguished anterograde from retrograde atrial activation in 19/19 (100%) patients. BAM achieves similar performance to CWA with significantly reduced computational demands, and may make real-time analysis of intracardiac electrograms feasible for implantable pacemakers and antitachycardia devices.

Algorithms↗
PubMed1990

Paroxysmal bundle branch block of supraventricular origin: a possible source of misdiagnosis in detecting ventricular tachycardia using time domain analyses of intraventricular electrograms.

Current implantable antitachycardia devices use several methods for differentiating sinus rhythm (SR) from supraventricular tachycardia (SVT) or ventricular tachycardia (VT). These methods include sustained high rate, the rate of onset, changes in cycle length, and sudden onset. Additional methods for detecting VT include techniques based upon ventricular electrogram morphology. The morphological approach is based on the assumption that the direction of cardiac activation, as sensed by a bipolar electrode in the ventricle, is different when the patient is in SR as compared to VT. Whether paroxysmal bundle branch block of supraventricular origin (BBB) can be differentiated from VT has not been determined. In this study, we compared the morphology of the ventricular electrogram during sinus rhythm with a normal QRS (SRNIQRS) or SVT with a normal QRS (SVTNIQRS) with the morphologies of BBB and VT in 30 patients undergoing cardiac electrophysiology studies. Changes in ventricular electrogram morphology were determined using three previously proposed time domain methods for VT detection: Correlation Waveform Analysis (CWA), Area of Difference (AD), and Amplitude Distribution Analysis (ADA). CWA, AD, and ADA distinguished VT from SRNIQRS or SVTNIQRS in 16/17 (94%), 14/17 (82%), and 12/17 (71%) patients, and BBB from SRNIQRS or SVTNIQRS in 15/15 (100%), 13/15 (87%), and 6/15 (40%) patients, respectively. However, the ranges of values during BBB using these methods overlapped with ranges of values during VT in all cases for CWA, AD, and ADA. Hence, BBB may be a source of misdiagnosis in detecting VT when these time domain methods are used for ventricular electrogram analysis.

Adolescent↗
PubMed1990

Intraventricular electrogram analysis for ventricular tachycardia detection: statistical validation.

Time-domain analysis of intraventricular electrogram morphology during ventricular tachycardia (VT) and sinus rhythm or atrial fibrillation (SR/AF) has been proposed as a method for increasing the specificity of pathological tachycardia detection by antitachycardia devices. However, few studies have validated the use of such analysis with statistical methods. When statistical methods have been utilized, it has been assumed that the distribution of the values derived from analysis of the intracardiac electrograms have had a normal (gaussian) distribution. In this study, we sought to determine whether: (1) the distribution of values derived from analysis of intracardiac electrogram during SR/AF and VT is gaussian or nongaussian; and (2) the discrimination of monomorphic VT from SR/AF using SR/AF templates can be validated statistically. Two previously proposed time-domain methods--correlation waveform analysis (CWA) and area of difference (AD)--were selected for evaluation of 29 patients with 33 distinct, sustained monomorphic VTs. An initial SR/AF template was used to analyze subsequent SR/AF and VT passages with a minimum of 50 consecutive depolarizations using a "best-fit" alignment. The values derived from each analysis were examined subsequently for skewness (asymmetry) and kurtosis (shape) using two-tailed tests (P less than 0.02). For passages of SR/AF, a normal (gaussian) distribution was present in only 24% (CWA), and 45% (AD); for passages of VT, normal distribution was present in only 58% for both CWA and AD. Using appropriate statistical testing with nonparametric tolerance intervals, CWA and AD discriminated VT from SR/AF in 29 out of 33 (88%), and 30 out of 33 (91%) instances, respectively, with 95% confidence.(ABSTRACT TRUNCATED AT 250 WORDS)

Atrial Fibrillation↗
PubMed1990

Detection of ventricular tachycardia using scanning correlation analysis.

Cross correlation is an accurate method for distinguishing normal sinus rhythm (NSR) from ventricular arrhythmias. The computational demands of the method, however, have prohibited development of an implantable device using correlation. In this study, temporal data compression prior to correlation analysis was used to reduce the total number of computations. Unipolar and bipolar intracardiac electrograms of NSR and 23 episodes of ventricular tachycardia (VT) from 23 patients were obtained from a right ventricular apex electrode catheter during routine electrophysiology studies. The data were filtered (1-11 Hz), digitized (250 samples/sec) and temporally compressed to 50 samples/sec. Data compression removed four out of every five samples by only saving the sample with the maximum excursion from the last saved sample. The average squared correlation coefficient (r2) was computed for the NSR and VT episodes using each patient's NSR waveform as a template. In all 23 patients, the r2 values showed large separation between NSR versus VT in both unipolar (0.93 +/- 0.05 vs 0.20 +/- 0.16, P less than 0.005) and bipolar (0.91 +/- 0.07 vs 0.17 +/- 0.11, P less than 0.005) electrode configurations using template lengths of 80% the intrinsic interval (avg +/- SD). Narrow templates (40% intrinsic interval or less) often resulted in multiple r2 peaks during each heart cycle and degraded the r2 separation (n = 10, P less than 0.005). High pass filtering at 3 Hz also degraded the r2 separation (n = 10, P less than 0.05). Standard noncompressed correlations indicated that data compression had negligible effects on the results. Thus, a computationally efficient cross correlation method was found to be a reliable detector of VT.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1989

An algorithm for the quantification of ST-T segment variability.

A template boundary algorithm which quantitatively determines repolarization (ST-T segment) variability in a normal population has been developed. The algorithm defines an initial ST-T template for comparison with successive beats. Variability is quantified using boundary limits around the template which are widened, when necessary, to included incoming ST-T segments. The boundaries at the end of each hour are stored and the collection of boundaries over a set of normal subjects quantifies the normal variation over the entire ST-T segment. The algorithm can be used to determine prospectively normal ST-T variability based on a regression analysis of R-wave or T-wave amplitude, and QT interval. Application of these boundary predictions should be useful in distinguishing repolarization changes secondary to ischemia from normal variability.

Algorithms↗
PubMed1989

A system for simultaneous esophageal atrial pacing and ventricular recording in computer analysis of posterior ischemia.

Abnormalities of the posterior cardiac wall are often small and obscured by electrical activity of the anterior wall of the left ventricle or by right ventricular hypertrophy. The posterior wall is hidden from the precordial leads by the anterior wall, and electrodes placed on the back are of little use because of their distance from the heart and of the intervening high-resistivity lungs. In contrast to the body surface, the esophagus provides a unique perspective of the posterior aspects of the heart at close range. The authors employed a noninvasive approach to produce cardiac stress and simultaneously record posterior cardiac electrical activity via the esophagus. A new esophageal electrode and instrumentation were developed for acquiring a high-quality esophageal electrocardiogram (ECG) during transesophageal atrial pacing stress. They present their technique for combining stress testing and computer analysis of ST-segment changes in the esophageal ECG as well as preliminary results from one normal subject and one patient with known posteroinferior ischemia.

Cardiac Pacing, Artificial↗
PubMed1989

Coping with parental quarrels.

Children's reactions to parental quarrels were investigated in a general population sample of children between 9 and 12 years old. One hundred and thirty-nine families participated in the study. Approximately half the children were living in disharmonious families and half were in harmonious families. Mothers and children were interviewed with semistructured interviews to determine how children responded to specific episodes of parental quarrelling. Seventy-one percent of children reported intervening in parental quarrels. A range of other coping strategies was identified: seeking contact with a sibling, confiding in friends, offering comfort to parents after a quarrel, self-blame, seeking information about quarrels, and perceiving beneficial aspects to parental quarrelling. The hypothesis was examined that certain coping strategies would be associated with lower levels of children's behavioral and emotional problems. Only a weak relationship was found between children's intervention in parental quarrels and emotional and behavioral problems. No other coping strategies were found to predict children's disturbance.

Adaptation, Psychological↗
PubMed1989

Discrimination of retrograde from anterograde atrial activation using intracardiac electrogram waveform analysis.

The prevention of pacemaker-mediated tachycardias requires a safe, reliable method for distinguishing retrograde from anterograde atrial activation by dual chamber pacemakers. In this study, a technique was developed to detect the morphological change that occurs in the waveform of the intra-atrial electrogram during retrograde atrial activation. The method employed for waveform analysis is based upon statistical correlation. In 19 patients undergoing electrophysiological studies, atrial electrograms were recorded from bipolar endocardial electrodes during sinus rhythm and 1:1 retrograde atrial depolarization while undergoing right ventricular pacing. Data were digitally sampled at 750, 1,000, and 1,500 Hz. Templates of anterograde atrial depolarization were constructed by signal averaging waveforms from an initial sinus rhythm passage. These were used for analysis of anterograde depolarizations from a subsequent passage of sinus rhythm and a passage of known retrograde atrial depolarization. In all 19 cases, a patient-specific threshold could be derived to separate anterograde from retrograde atrial depolarizations using 1,000 Hz and 1,500 Hz sampling rates. However, at a sampling rate of 750 Hz, separation of anterograde from retrograde atrial activation was possible in only 16/19 patients (84%). We conclude that correlation waveform analysis of a suitably sampled atrial electrogram is a reliable method of discriminating retrograde atrial depolarization from anterograde atrial depolarization in intracardiac electrograms.

Adult↗
PubMed1988

Reflections from a decade of carotid reconstructive surgery.

Carotid artery reconstructive surgery for atherosclerotic lesions of the extracranial cerebral circulation has become the most common operation in peripheral vascular surgery. A better understanding of the indications for operative intervention, enhanced monitoring during surgery, and more precise management of intraoperative anesthesia have all helped decrease the risks associated with internal carotid endarterectomy. To evaluate the safety and efficacy of extracranial carotid reconstructive surgery, we reviewed 2,857 operations done on 2,087 patients from 1976 to 1985. Operation was recommended because of hemispheric symptoms in 58%, and because of asymptomatic, significant stenosis in 14%. Postoperative hemiparesis occurred in 24 patients and was associated with thrombosis at the operative site in 18 patients. Antiplatelet drugs used during the last three years were found to be effective in preventing thrombosis at the operative site. Operative mortality during the study period was 1.5%. Follow-up has ranged from one month to 104 months, with 84% of the patients alive and 79% symptom free.

Aged↗
PubMed1988

Identification of ventricular tachycardia using intracavitary ventricular electrograms: analysis of time and frequency domain patterns.

Tachycardia detection by implantable antitachycardia devices using rate alone has major limitations. Several alternative methods have been proposed to distinguish ventricular tachycardia or ventricular fibrillation from normal sinus rhythm using intracardiac electrograms. These methods have not been tested, however, for recognition of ventricular tachycardia in patients with abnormal surface QRS conduction during sinus rhythm or with antiarrhythmic drug therapy. In this study, three techniques for the identification of ventricular tachycardia from intracavitary bipolar ventricular electrograms were examined and compared: correlation waveform analysis, amplitude distribution analysis, and spectral analysis using Fast Fourier transformation. Thirty episodes of induced monomorphic ventricular tachycardia were analyzed and compared sinus rhythm in four groups of patients with: I. Normal surface QRS conduction during sinus rhythm without antiarrhythmic drug therapy (five episodes); II. Intraventricular conduction delay or bundle branch block during sinus rhythm without antiarrhythmic drug therapy (nine episodes); III. Normal surface QRS conduction during sinus rhythm with antiarrhythmic therapy (six episodes); and IV. Intraventricular conduction delay or bundle branch block during sinus rhythm with antiarrhythmic drug therapy (ten episodes). Correlation waveform analysis had 100% sensitivity and specificity in distinguishing ventricular tachycardia from sinus rhythm, even in the presence of an intraventricular conduction delay, bundle branch block, and antiarrhythmic drug therapy. In contrast, amplitude distribution analysis differentiated 15/30 episodes (50.0%) of ventricular tachycardia from sinus rhythm, and a maximum of 18/30 episodes (60.0%) of ventricular tachycardia were identified by special analysis using Fast Fourier transformation. Correlation waveform analysis appears to be a reliable technique to discriminate ventricular tachycardia from sinus rhythm using intracavitary ventricular electrograms. Its computational demands are modest, making it suitable for consideration in an implantable antitachycardia device.

Adolescent↗