Search PubMed⌕ Search

Biomedical subjects

R W Peters

Publications and source records attributed to R W Peters.

At least 109 records · Page 6Linked to original sources
PubMed1984

Electrophysiologic testing in bundle branch block and unexplained syncope.

Thirty-two patients with bundle branch block and unexplained syncope underwent electrophysiologic testing, including programmed ventricular stimulation with up to triple extrastimuli. The infranodal conduction time (HV) was 70 ms or greater in 12 patients. Pathologic infranodal block during atrial pacing occurred in 2 patients. Unimorphic ventricular tachycardia (VT) was induced in 9 patients (28%) and polymorphic VT in 5 (16%). A permanent pacemaker was implanted in patients with infranodal block during atrial pacing and, generally, in patients with an HV of 70 ms or more. Patients with inducible unimorphic or sustained polymorphic VT were treated with an antiarrhythmic drug. The mean follow-up period was 19 +/- 14 months (+/- standard deviation). Three patients died suddenly: a noncompliant patient with inducible sustained VT; a patient with a normal electrophysiologic study treated empirically with quinidine for premature ventricular complexes; and a patient with an HV of 70 ms and no inducible VT treated with a permanent pacemaker. The actuarial incidence of sudden death was 10% at 45 months of follow-up. Only 2 patients had recurrent syncope; both had a normal electrophysiologic study. Approximately 50% of patients with bundle branch block and unexplained syncope who undergo electrophysiologic testing are found to have a clinically significant abnormality (HV of 70 ms or more, infranodal block during atrial pacing and inducible unimorphic VT), and some patients have more than 1 abnormality. Long-term management guided by the results of electrophysiologic testing generally is successful in preventing recurrent syncope.(ABSTRACT TRUNCATED AT 250 WORDS)

Adolescent↗
PubMed1984

Catheter-induced A-V nodal block occurring during electrophysiologic study.

We describe a patient who underwent electrophysiologic study for evaluation of recurrent syncope. No abnormalities were found but high-grade A-V block proximal to the His bundle depolarization developed abruptly as the coronary sinus electrode catheter was being withdrawn. The A-V block disappeared gradually over a 12-hour period, progressing to type I second-degree A-V block, and then to first-degree A-V block (due to prolonged A-V nodal conduction), prior to resuming normal conduction. We postulate that A-V block was induced by direct contact between the electrode catheter and the A-V node or very proximal His bundle. Catheter-induced A-V block at this site has been described only rarely, possibly because of the relatively protected location and the configuration of the A-V node.

Adult↗
PubMed1984

Sequential development of humoral immunity and assessment of protection in chickens following vaccination and challenge with avian infectious bronchitis virus.

Chicks without specific maternal antibody to avian infectious bronchitis virus were vaccinated intranasally at two weeks old with a live H120 vaccine and a proportion revaccinated with a live H52 vaccine at 15 weeks. Groups of these birds were then challenged intratracheally with the Massachusetts M41 strain at varying intervals and their humoral antibody responses monitored by neutralisation and haemagglutination-inhibition tests. Protection was assessed by the presence of tracheal ciliostasis four days after challenge and was shown to correlate completely with histopathological findings and immunofluorescence microscopy. Chicks were protected by H120 alone up to 12 weeks old and, following revaccination with H52, up to between 30 and 50 weeks. The antibody responses following challenge became increasingly enhanced as the vaccinal antibody titres declined. The results are discussed in relation to previous reports and the response to vaccination against infectious bronchitis virus of chickens in commercial flocks.

Animals↗
PubMed1983

Serum creatine kinase in the diagnosis of acute myocardial infarction. Optimal sampling frequency.

To document optimal sampling frequency, we reviewed creatine kinase (CK) myocardial specific isoenzyme (CKMB) results in 314 patients with suspected acute myocardial infarction (MI). In 127 patients with elevated CK/CKMB, peak CK observed using all samples (every four-hour [Q4hr] method) was compared with results that would have been obtained had samples been taken on admission and either twice daily (every 12-hour [Q12hr] method) or once daily (every 24-hour [Q24hr] method). Although average peak CK was statistically different (Q4hr greater than Q12hr greater than Q24hr), major underestimation of peak CK (greater than or equal to 500 units/L) was uncommon (3%) using the Q12hr method, suggesting that Q12hr sampling is a practical, cost-effective approach for patients with suspected acute MI.

Clinical Enzyme Tests↗
PubMed1983

Acute changes in infranodal conduction time following left ventriculography and sublingual nitroglycerin administration in man.

During diagnostic cardiac catheterization for the evaluation of chest pain, His bundle electrograms were obtained in 32 male patients before and 2 to 5 minutes after each of two interventions known to acutely affect left ventricular volume and left ventricular end-diastolic pressure (the injection of 40 to 60 cc of contrast medium during left ventriculography and the administration of 0.4 mg of sublingual nitroglycerin). Changes in left ventricular end-diastolic pressure (18 +/- 6 vs 30 +/- 7 mm Hg, p less than 0.001 following ventriculography and 32 +/- 8 vs 19 +/- 8 mm Hg, p less than 0.005 following nitroglycerin administration) were accompanied by parallel alterations in HQ (48 +/- 8 vs 54 +/- 10 msec, p less than 0.005 following ventriculography and 57 +/- 10 vs 53 +/- msec, p less than 0.005 following nitroglycerin administration), but there were no significant changes in atrioventricular (AV) nodal conduction (AH). Significantly greater changes in HQ were seen in patients with triple-vessel coronary artery disease than in the remainder of the population, although there was clinical and/or ECG evidence of ischemia in only one patient. We conclude that factors other than progression of intrinsic conduction system disease may affect infranodal conduction. HQ should be interpreted cautiously in situations with rapidly changing hemodynamics, especially in patients with severe coronary artery disease.

Bundle of His↗
PubMed1983

Cardiac arrhythmias after abrupt clonidine withdrawal.

Abrupt clonidine withdrawal may be associated with sharp marked increases in catecholamine levels, heart rate, and blood pressure, which may induce nausea, vomiting, and palpitations. Relatively little information is available on the incidence of cardiac arrhythmias in this setting. With continuous ambulatory ECG recordings, we determined the incidence of arrhythmias in seven male hypertensive patients (without active heart disease) after abrupt clonidine withdrawal. Serious ventricular arrhythmias, including brief ventricular tachycardia, developed in two patients who had greater increases in mean systolic blood pressure (28 +/- 3 vs 10 +/- 8 mm Hg) and double product (552 +/- 681 vs 333 +/- 195) than the others. The differences were not significant. Ventricular arrhythmias were not related to age, dose, withdrawal symptoms, initial blood pressure, urinary norepinephrine levels, or ECG abnormalities. We conclude that serious ventricular arrhythmias may be relatively common but unpredictable during clonidine withdrawal, even in patients with no clinically apparent heart disease. The triggering of ventricular arrhythmias should be added to the list of components of clonidine withdrawal syndrome.

Adult↗
PubMed1983

Electrophysiologic studies in patients with bundle branch block.

A total of 401 patients with chronic bundle branch block underwent electrophysiologic studies and were followed for a mean of approximately 30 months. Patients with an infranodal conduction time (H-Q) greater than or equal to 70 ms had a significantly higher incidence of progression to spontaneous second-degree or third-degree atrioventricular (AV) block (12%) compared with those with H-Q less than 70 ms (3.5%). The incidence of AV block was 25% for those with H-Q greater than or equal to 100 ms. Although the incidences of all deaths and cardiac deaths were higher for the H-Q greater than or equal to 70 ms group, there was no statistically significant difference in the incidence of sudden deaths in the two groups. A subgroup of 77 patients underwent prophylactic pacemaker insertion based on the presence of transient neurologic symptoms and/or a prolonged H-Q interval. We found no significant difference in the incidence of relief of symptoms or incidence of cardiac or sudden deaths between paced and unpaced groups. A subgroup of 25 patients with syncope underwent ventricular stimulation studies and ventricular tachycardia was induced in 14. We conclude that a markedly prolonged H-Q interval (greater than or equal to 100 ms) may be of value in detection of spontaneous AV block. Prophylactic pacing is of no value in either relief of symptoms or prolongation of life. Complete electrophysiologic studies, including ventricular stimulation studies, are indicated for patients with bundle branch block and syncope.

Aged↗
PubMed1983

Pitch of components of complex tones.

Subjects made pitch matches to individual components in complex tones consisting of either the 4th to 7th or the 1st to 7th harmonics of a 200-Hz fundamental. All components were at equal levels (either 31-, 51-, or 71-dB SPL per component) and the matching pure tone was equal in level to the component being matched. Attention was drawn to the component to be matched either by giving the matching tone an initial frequency close to that of the component (standard condition) or by suppressing and then introducing the component (emergent condition). The pitch matches did not differ significantly for the two conditions, and did not change with overall level. For two subjects, matches to components in the context of the complexes were very close to matches obtained for the components presented in isolation. For a third subject, matches in context were shifted slightly upwards for the lowest component, and downwards for the highest component. A control condition showed that subjects were able accurately to match a small shift in frequency of one component in a four-tone complex. An adaptive forced-choice method described by Jesteadt [Percept. Psychophys. 28, 85-88 (1980)] was also used to estimate the pitches of the components. A very slight bias was apparent in the results, but the pitches of components in context were again found to be very close to those of components in isolation.

Humans↗
PubMed1982

Value of the H-Q interval in patients with bundle branch block and the role of prophylactic permanent pacing.

His bundle electrograms were obtained in 313 patients with chronic bundle branch block who were followed for a mean period of almost 3 years. The infranodal conduction time (H-Q interval) was less than 55 ms in 97 patients (Group I), 55 to 69 ms in 99 patients (Group II), and greater than or equal to 70 ms in 117 patients (Group III). There was a higher incidence of organic heart disease in patients in Group III, but the groups were otherwise comparable. On follow-up study, mortality and the incidence of sudden death were similar among the groups, but patients in Group III had a greater incidence of progression to high degree atrioventricular block (HDB) than did those in Groups I and II (14 of 117 [12%] versus 4 of 97 [4%] and 2 of 99 [2%], p less than 0.01, respectively). High degree block was found in 4 of 17 (24%) patients with an H-Q interval (H-Q) greater than or equal to 100 ms. Sixty-two patients underwent permanent prophylactic pacemaker insertion at the discretion of the referring physician and were compared with 231 patients who did not. Paced patients had a higher incidence of transient neurologic symptoms and prolonged H-Q, but the groups were otherwise comparable. On follow-up study, mortality and the incidence of sudden death were similar among the groups, but symptom relief was significantly more common among patients with pacemakers. In conclusion, in our population (1) H-Q greater than or equal to 70 ms was an independent risk factor for progression to HDB, (2) H-Q greater than or equal to 100 ms identified a subgroup at particularly high risk, and (3) prophylactic pacemakers relieved neurologic symptoms but did not prolong life.

Aged↗
PubMed1982

Late unheralded pacemaker pocket infection due to Staphylococcus epidermidis: a new clinical entity.

Late pacemaker pocket infections in the absence of predisposing factors such as multiple pacemaker related procedures, skin erosion, chest wall trauma or generalized sepsis have been rarely reported. In the past year, we have seen three late pocket infections (18, 32 and 47 months post-implantation) due to Staphylococcus epidermidis (S. epidermidis). All three patients with late S. epidermidis infections presented with painless swelling over the pulse generator site and had been well until shortly before admission. The patients denied febrile illnesses or chest trauma in the preceding year and no skin erosion was evident. All had been seen regularly in clinic and bimonthly transtelephonic recordings had shown normal pacemaker function. Local drainage, antibiotics and removal of the pacing system was successful in all three patients. We conclude that late pacemaker pocket infections due to S. epidermidis may become an important clinical problem in this era of long-lasting pulse generators. In light of the insidious nature of S. epidermidis infections, regular inspection of the pocket area by both patient and physician is mandatory.

Aged↗
PubMed1982

Change in the pitch of a complex tone following its association with a second complex tone.

The pitch of a high-frequency complex stimulus was changed and maintained in the direction of the pitch of a low-frequency complex stimulus with which it was associated. Six observers made pitch matches for a pitch-shift stimulus (1250-1450-1650 Hz) before and after simultaneous presentation of this stimulus with the first through fifth harmonics of 200 Hz (200-400-600-800-1000 Hz). Data were collected for each observer on five consecutive days and one week following the fifth day. The experimental phases each day were (1) ten matches, (2) simultaneous stimuli followed by ten matches, and (3) simultaneous stimuli followed by ten matches. Association periods for simultaneous stimuli were 5 min in duration and a 5-min rest period separated the association and matching periods. The result indicated that the pitch of the pitch-shift stimulus continued to change significantly for days one through four, from an initial pitch match near 210 Hz to a final match near 205 Hz. The post one-week pitch match was also significantly lower than the initial pitch match. The pitch changes are discussed in terms of a pitch learning hypothesis.

Acoustic Stimulation↗
PubMed1982

Serial electrophysiologic studies in patients with chronic bundle branch block.

Serial His bundle recordings were obtained during 1:1 atrioventricular (AV) conduction in 90 patients with chronic bundle branch block over a mean interval of 30 months. Atrioventricular conduction time (AH) increased greater than or equal to 10 msec in 25 (28%) and infranodal conduction time (HV) increased greater than or equal to 8 msec in 29 (32%), but only 10 patients had parallel increases in AH and HV intervals. Increases in conduction times were independent of age, time interval between studies, cause of heart disease or initial AH or HV intervals. Women were significantly more likely than men to show an increased HV interval and spontaneous trifascicular block. Spontaneous progression to second- or third-degree AV block occurred at the AV node in seven patients and below the node in 12 patients. The initial AH interval was prolonged in five of seven patients (71%) with AV nodal block and had increased further in only two at restudy. The initial HV interval was abnormal in eight of 12 patients (67%) who progressed to infranodal block and was prolonged further in eight at restudy. We conclude that in patients with chronic bundle branch block, (1) approximately 33% show progressive AV conduction system disease and AV nodal and infranodal disease progress independently; (2) progression of infranodal disease is more common in women; (3) AV nodal disease progress independently; (2) progression of infranodal disease is more common in women; (3) AV nodal disease is a common cause of AV block and can occur without further prolongation of the AH interval once a critical level of disease is attained, whereas infranodal block is usually accompanied by progressive lengthening of the HV interval; and (4) progression of AV conduction disease is not readily predictable from clinical and electrophysiologic variables.

Aged↗
PubMed1982

Collateral circulation in patients with unstable angina.

Coronary collaterals were evaluated in 218 consecutive catheterized patients with unstable angina (defined as ischemic cardiac pain at rest associated with transient electrocardiographic changes). Collaterals were present in 106 patients (49 percent). The presence of collaterals correlated with the extent and severity of the coronary artery disease but not with age, sex, or risk factors. Among patients with comparable severity of narrowings, the presence of collaterals did not appear to protect against abnormal wall motion or pathologic Q waves on the ECG. In patients with single vessel disease, collaterals also did not appear to protect against transient ST segment evaluation during ischemia.

Age Factors↗
PubMed1981

Atrial and ventricular vulnerability in a patient with the Wolff-Parkinson-White syndrome.

An electrophysiologic study was carried out in a patient with the Wolff-Parkinson-White syndrome and a history of spontaneous atrial fibrillation but with no evidence of organic cardiac disease. A single induced premature ventricular depolarization resulted in ventricular tachycardia followed by ventricular fibrillation. Similarly, atrial pacing or premature atrial stimulation resulted in frequent episodes of atrial fibrillation or flutter. The atrial and ventricular effective refractory periods were 180 ms and less than 160 ms, respectively, at a driven cycle length of 480 ms. Intravenous administration of procainamide resulted in lengthening of the refractory periods and failure to induce either atrial or ventricular arrhythmias with pacing. In most patients with enhanced atrioventricular nodal or accessory atrioventricular nodal by-pass, the mechanism of ventricular tachycardia is related to an inordinately rapid ventricular response during supraventricular arrhythmias. In our patient, a unique mechanism was apparent: atrial and ventricular vulnerability to fibrillation was associated with extremely short myocardial effective refractory periods. The relationship of this finding to sudden cardiac death bears further study.

Adult↗
PubMed1981

Pitch for nonsimultaneous successive harmonics in quiet and noise.

Pitch perception was studied with respect to nonsimultaneous successive harmonics of fundamentals in quiet and noise. Stimuli consisted of three nonoverlapping sine waves each of 40-msec duration. Pitch perception, examined by discrimination and matching, was found to correspond to spectral frequency in quiet and fundamental frequency in noise. The results suggest a pitch processor that integrates over time (synthetic mode) in noise and analyzes spectral components (analytic mode) in quiet. The findings are discussed with respect to current theories of pitch perception and auditory integrative functions. The findings are thought to be particularly relevant to analytic and synthetic modes of pitch perception.

Acoustics↗