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Biomedical subjects

R W Peters

Publications and source records attributed to R W Peters.

At least 91 records · Page 5Linked to original sources
PubMed1987

Electrophysiologic effects of cigarette smoking in patients with and without chronic beta-blocker therapy.

After refraining from smoking for at least 8 hours, 22 adult male habitual smokers underwent baseline electrophysiologic study including atrial and ventricular burst pacing and programmed premature stimulation with single extrastimuli. After smoking 2 of their usual brand of cigarettes in rapid succession, the electrophysiologic protocol was repeated. Nicotine, catecholamine and carbon monoxide concentrations all increased significantly. Smoking increased heart rate and improved atrioventricular conduction in the 13 patients receiving chronic beta-blocker therapy (mostly for angina pectoris); increases in heart rate and improvement in atrioventricular conduction were not different statistically from those seen in patients not receiving beta-blocker therapy, suggesting the possibility of a direct effect of nicotine or other components of tobacco smoke. Ventricular refractoriness was not altered and atrial and ventricular arrhythmias were not increased by smoking. Persistent sympathomimetic actions of cigarette smoking may explain in part the failure of beta-blocking drugs to reduce cardiac mortality risk in smokers after myocardial infarction.

Adrenergic beta-Antagonists↗
PubMed1987

Mortality in the beta blocker heart attack trial: circumstances surrounding death.

In the Beta Blocker Heart Attack Trial, a double blind, randomized, controlled study, patients taking propranolol (180 or 240 mg/day) initiated 5-21 days post myocardial infarction had 26% fewer deaths than those taking placebo over a 25 month (mean) followup. Detailed analysis of the circumstances surrounding the BHAT deaths failed to reveal any striking difference between propranolol and placebo in the type of clinical event preceding death, the incidence and type of acute and prodromal signs and symptoms, the location of death, the activity preceding death or the percentage of deaths that were sudden or instantaneous, suggesting that propranolol may exert an "across the board" effect and improve survival by a combination of mechanisms. An unexpected finding was that the protective effect of propranolol appeared to occur during the hours of 10 p.m. to 7 a.m.

Aged↗
PubMed1986

Beta-blockers in congestive cardiomyopathy. Conceptual advance or contraindication?

The precise role of adrenergic activity in congestive cardiomyopathy has not been established. A number of mechanisms through which increased catecholamine levels may be harmful, along with the clinical and experimental evidence supporting this concept, are summarized in this review. In this context, the suggestion that beta blockers may be beneficial for patients with severe heart failure, despite their well-known propensity to decrease cardiac contractility, can be better understood. Published reports on the use of beta blocker therapy for congestive cardiomyopathy now include approximately 200 patients, but have yielded inconsistent results. Non-randomized trials in Sweden have suggested increased survival, with most patients having improved functional status while receiving beta blockade, although improvement may take three to six months to become evident. The Swedish group also reported clinical deterioration after discontinuation of beta blockade. Two recent randomized trials in America yielded promising results, but the unexpectedly low mortality in the placebo groups emphasizes the critical importance of concurrent controls. Unfavorable reports have involved small groups with short-duration therapy. Even in these reports, overt aggravation of clinical heart failure has been quite infrequent but sometimes profound. As large scale trials are undertaken, an obvious goal is the development of methods to differentiate the patients with congestive cardiomyopathy who will benefit in response to beta blocker therapy from the few patients who will have a serious adverse response.

Adrenergic beta-Antagonists↗
PubMed1986

Delayed chest wall complications of median sternotomy.

Chest wall pain after coronary artery bypass surgery is often attributed to incisional pain or anxiety. Although this assumption is often correct, a small number of patients have an unrecognized chest wall complication of the median sternotomy. In this paper we identify these delayed postoperative midsternotomy complications and discuss their appropriate management.

Cartilage Diseases↗
PubMed1986

Coronavirus IBV: virus retaining spike glycopolypeptide S2 but not S1 is unable to induce virus-neutralizing or haemagglutination-inhibiting antibody, or induce chicken tracheal protection.

Avian infectious bronchitis coronavirus (IBV) inactivated by beta-propiolactone induced partial protection of the trachea in up to 40% of chickens following one intramuscular inoculation 4 to 6 weeks prior to challenge. Retention of an intact tracheal ciliated epithelium 4 days after challenge was the criterion of protection. There was no correlation between protection and serum titres of virus-neutralizing (VN) and haemagglutination-inhibiting (HI) antibody, which were maximal at about 4 weeks after inoculation. Virus from which the S1 but not the S2 (spike-anchoring) spike glycopolypeptide had been removed by urea did not induce protection or VN or HI antibody. Four intramuscular inoculations of monomeric S1 induced VN and HI antibody in two and four chickens respectively. These results indicate that VN and HI antibodies are induced primarily by S1, that intact spikes are a major requirement for the induction of protective immunity and that this property is probably associated with S1.

Animals↗
PubMed1986

Prolonged sinus arrest complicating a thrombotic stroke.

A 56-year-old man developed sinus node dysfunction culminating in 27 seconds of asystole during a thrombotic stroke. Bradyarrhythmias resolved over a period of 96 hours, at which time sinus node recovery times were normal. Sinus node dysfunction has not recurred during the two years of follow-up. We suggest that cardiac rhythm be closely monitored in acute stroke patients.

Bradycardia↗
PubMed1986

Thresholds for hearing mistuned partials as separate tones in harmonic complexes.

When a low harmonic in a harmonic complex tone is mistuned from its harmonic value by a sufficient amount it is heard as a separate tone, standing out from the complex as a whole. This experiment estimated the degree of mistuning required for this phenomenon to occur, for complex tones with 10 or 12 equal-amplitude components (60 dB SPL per component). On each trial the subject was presented with a complex tone which either had all its partials at harmonic frequencies or had one partial mistuned from its harmonic frequency. The subject had to indicate whether he heard a single complex tone with one pitch or a complex tone plus a pure tone which did not "belong" to the complex. An adaptive procedure was used to track the degree of mistuning required to achieve a d' value of 1. Threshold was determined for each ot the first six harmonics of each complex tone. In one set of conditions stimulus duration was held constant at 410 ms, and the fundamental frequency was either 100, 200, or 400 Hz. For most conditions the thresholds fell between 1% and 3% of the harmonic frequency, depending on the subject. However, thresholds tended to be greater for the first two harmonics of the 100-Hz fundamental and, for some subjects, thresholds increased for the fifth and sixth harmonics. In a second set of conditions fundamental frequency was held constant at 200 Hz, and the duration was either 50, 110, 410, or 1610 ms. Thresholds increased by a factor of 3-5 as duration was decreased from 1610 ms to 50 ms. The results are discussed in terms of a hypothetical harmonic sieve and mechanisms for the formation of perceptual streams.

Auditory Threshold↗
PubMed1985

Transcutaneous temporary pacing in the operating room.

The safety and efficacy of transcutaneous temporary pacing were assessed in 21 patients undergoing elective surgical procedures under general anesthesia. Complete capture was achieved in all patients. The pacing threshold was 50 mamp in two patients, 100 mamp in nine, and 200 mamp in ten. The threshold was influenced by electrode position and also, possibly, by age, heart size, and chest size. No adverse effects of pacing were encountered. Transcutaneous pacing is a rapid, safe, and effective means of temporary pacing in the operating room.

Adult↗
PubMed1985

Routine preoperative exercise testing in patients undergoing major noncardiac surgery.

A prospective study of preoperative exercise testing was carried out in 200 patients older than 40 years scheduled for elective major noncardiac surgery under general anesthesia. The exercise test response was electrocardiographically positive in 32 patients (16%) (2 patients had a markedly positive test), equivocal in 11 patients (5.5%) and negative in 157 patients (78.5%). The patients were followed with serial pre- and postoperative electrocardiograms (ECGs) and determinations of serum creatine kinase (CK) and CK-MB. Six patients (3%) had primary endpoints: 3 (1.5%) died postoperatively and 3 (1.5%) had definite postoperative myocardial infarction. Secondary endpoints of suspected postoperative myocardial ischemia/injury diagnosed by ECG or elevation in CK-MB levels occurred in 27 patients (14%). Endpoint events were more common in patients aged 70 years or older. Endpoint events were also more common in patients with an abnormal (positive or equivocal) preoperative exercise test response than in those with a negative response (27% vs 14%); however, preoperative exercise results were not statistically significant independent predictors of cardiac risk. Using multivariate analysis, the only statistically significant independent predictor of risk was the preoperative ECG. Endpoint events were more common in patients with an abnormal than in those with a normal ECG (23% vs 7%, p less than 0.002). Because the results of exercise testing do not appear to add substantially to the risk separation provided by the ECG at rest, exercise testing is not recommended as a routine preoperative method for assessing perioperative risk in older patients who are being evaluated before major elective noncardiac surgery under general anesthesia.

Adult↗
PubMed1985

Technetium-99m-pyrophosphate scintigraphy in patients with suspected acute myocardial infarction: impact of interobserver variability.

Technetium-99m-pyrophosphate (TcPYP) scintigraphy may have great value in patients with suspected acute myocardial infarction (AMI), but interobserver variability undoubtedly has adverse impact on predictive value. TcPYP scintigrams for 133 (80%) of 166 consecutive patients admitted for suspected AMI were interpreted independently by three experienced readers. Although there was complete agreement for 87 interpretations (65%), major discrepancies (i.e., at least one positive and one negative reading on the same scan) occurred for 28 scans (21%). To assess predictive accuracy, patients were categorized as follows: 36 had definite AMI manifest by new ECG Q waves and/or CK-MB evidence of AMI (group I), 56 were classified as possible AMI (group II), and 41 had AMI excluded (group III). Using only the definitive diagnostic categories (groups I and III), accuracy for each reader approximated 0.68, with no single reader being correct more often than any other.

Creatine Kinase↗
PubMed1985

Persistent chest pain due to sternal wire sutures: a complication of coronary artery bypass surgery.

Disabling incisional pain weeks or months after coronary artery bypass surgery should prompt an investigation for a postmidsternotomy chest wall complication. Our patient had symptomatic relief after the removal of a painful sternal wire suture. Prompt recognition of this delayed chest wall complication, which can be confused with cardiac pain, may obviate a more lengthy and costly evaluation.

Coronary Artery Bypass↗
PubMed1985

Long-term management of recurrent paroxysmal tachycardia by cardiac burst pacing.

Sixteen patients with either recurrent symptomatic supraventricular tachycardia (SVT) (ten) or ventricular tachycardia (VT) (six) unresponsive to drug treatment underwent insertion of chronic overdrive cardiac pacing devices for arrhythmia control. All patients with SVT followed for longer than 2.5 years required concomitant drug therapy for rhythm control. In addition, one of the ten patients required amiodarone and three required nonpharmacologic therapy (catheter ablation of the atrioventricular junction (one), surgical ablation of the Kent bundle and/or bundle of His (two). In the six patients with VT, only one patient used the device successfully. In the other five patients, either the arrhythmia failed to respond to burst overdrive pacing (three) or overdrive acceleration resulted (two). One death in the latter group was related to induction of rapid VT followed by ventricular fibrillation. Long-term follow-up of patients with paroxysmal SVT shows that virtually all require concomitant drug therapy and may require aggressive medical or surgical procedures for arrhythmia control. Use of ventricular overdrive pacing for those with VT appeared singularly disappointing in that pacing proved either ineffective (three) or resulted in overdrive acceleration (two) in 5/6 patients.

Adult↗
PubMed1985

Thresholds for the detection of inharmonicity in complex tones.

Thresholds were measured for the detection of inharmonicity in complex tones. Subjects were required to distinguish a complex tone whose partials were all at exact harmonic frequencies from a similar complex tone with one of the partials slightly mistuned. The mistuning which allowed 71% correct identification in a two-alternative forced-choice task was estimated for each partial in turn. In experiment I the fundamental frequency was either 100, 200, or 400 Hz, and the complex tones contained the first 12 harmonics at equal levels of 60 dB SPL per component. The stimulus duration was 410 ms. For each fundamental the thresholds were roughly constant when expressed in Hz, having a mean value of about 4 Hz (range 2.4-7.3 Hz). In experiment II the fundamental frequency was fixed at 200 Hz, and thresholds for inharmonicity were measured for stimulus durations of 50, 110, 410, and 1610 ms. For harmonics above the fifth the thresholds increased from less than 1 Hz to about 40 Hz as duration was decreased from 1610-50 ms. For the lower harmonics (up to the fourth) threshold changed much less with duration, and for the three shorter durations thresholds for each duration were roughly a constant proportion of the harmonic frequency. The results suggest that inharmonicity is detected in different ways for high and low harmonics. For low harmonics the inharmonic partial appears to "stand out" from the complex tone as a whole. For high harmonics the mistuning is detected as a kind of "beat" or "roughness," presumably reflecting a sensitivity to the changing relative phase of the mistuned harmonic relative to the other harmonics.(ABSTRACT TRUNCATED AT 250 WORDS)

Auditory Threshold↗
PubMed1985

Giant pacemaker spikes. An electrocardiographic artifact.

The size and orientation of the spikes produced by a pacemaker are often used by clinicians as an index of the pacemaker's function. Following implantation, the pacemaker spikes ordinarily remain constant in size; alterations suggest electrical or mechanical malfunction. We describe a patient in whom giant spikes from a pacemaker were recorded on a digital electrocardiograph shortly after implantation. An electrocardiogram taken the following day, using an analog machine, showed marked diminution in the pacemaker spike. Because of a different type of signal processing, digital electrocardiographs show much larger spikes from pacemakers than do analog machines.

Cardiac Pacing, Artificial↗
PubMed1985

Humoral antibody response and assessment of protection following primary vaccination of chicks with maternally derived antibody against avian infectious bronchitis virus.

Commercially bred chicks with maternally derived antibody to avian infectious bronchitis virus (IBV) were hatched in isolated conditions and a number vaccinated within the first three weeks of life with live IBV strain H120. Humoral antibody responses were assayed by haemagglutination inhibition (HI) or neutralisation (SN) tests, and the degree of protection against challenge with the virulent Massachusetts M41 strain assessed on the basis of tracheal ciliary activity four days after challenge. Maternal antibody in unvaccinated chicks declined linearly with a mean half-life of five to six days based on both HI and SN tests; these chicks were protected against challenge until four weeks old. There was complete correlation between ciliary activity and histopathological findings, but little between protection and antibody titre. It was concluded that the optimum age for primary vaccination was about two weeks.

Animals↗