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Biomedical subjects

C Wyndham

Publications and source records attributed to C Wyndham.

At least 37 records · Page 2Linked to original sources
PubMed1979

Chronic nonparoxysmal sinus tachycardia in otherwise healthy persons.

Seven patients had chronic, unexplained, nonparoxysmal sinus tachycardia. The clinical, electrocardiographic, and electrophysiologic characteristics of these cases are described. In each case electrocardiographic and electrophysiologic observations suggested that tachycardia was nonparoxysmal and due to increased automaticity of the sinus node (or of an automatic atrial focus located very near the sinus node). The mechanisms of increased sinus node automaticity in these patients were explored using drugs affecting the autonomic nervous system. In each patient these studies suggested a defect in either sympathetic or vagal nerve control of resting heart rate, with or without an abnormality of intrinsic heart rate. Data are also presented on baroreceptor reflex arc function in these patients.

Adolescent↗
PubMed1978

In vitro metabolism of 4-chlorobiphenyl by control and induced rat liver microsomes.

The in vitro metabolism, mechanism of metabolism, and macromolecular binding of a monochlorobiphenyl component of commercial polychlorinated biphenyls (PCB) have been investigated. 4-Chlorobiphenyl was metabolized by rat liver microsomes in the presence of NADPH to yield a major metabolite, 4'-chloro-4-biphenylol, and a number of minor metabolites. The metabolism of deuterium-labeled 4-chlorobiphenyl proceeded with the NIH shift of the isotope and no observed isotope effect thus indicating the intermediacy of an arene oxide. Noninduced rat liver microsomes mediated the covalent binding between the 4-chlorobiphenyl and 4'-chloro-4-biphenylol substrates and endogenous microsomal protein. Prior in vivo administration of a commericial PCB preparation, Aroclor 1248 (Monsanto Chemical Co., containing 48 percent by weight of chlorine), resulted in an induced microsomal preparation which significantly increased the substrate-protein binding. The effect of various inhibitors on protein binding was investigated. Aroclor 1248 induced microsomes mediated binding of 4-chlorobiphenyl to endogenous and exogenous nucleic acids, indicating a possible mechanism for the previously reported mutagenic action of this chlorobiphenyl. The spectral properties of Aroclor 1248 induced cytochrome P-450 were investigated and compared with the pentobarbital-induced cytochrome fraction.

Animals↗
PubMed1978

Significance of left axis deviation in patients with chronic left bundle branch block.

Forty-nine patients with chronic left bundle branch block and a normal frontal axis were compared with 53 patients with left bundle branch block and left axis deviation. The following clinical variables were more frequent (P less than 0.05) in patients with left axis deviation: greater age, exertional angina, congestive heart failure, cardiomegaly, cardiac functional class II to IV, coronary artery disease and presence of organic heart disease. Absence of organic heart disease (primary conduction disease) was seen only in patients with a normal axis. Patients with left axis deviation had longer (P less than 0.05) mean P-R, A-H and H-V intervals and atrial and atrioventricular (A-V) nodal effective refractory periods. All patients were prospectifely followed up for 30 to 2,271 days with a mean +/- standard error of the mean follo-up period of 538 +/- 72 for the group with a normal axis and 604 +/- 72 days for the group with left axis deviation (difference not significant). A-V block developed in three patients (6 percent) with left axis deviation and in none of those with a normal axis. The cumulative 4 year mortality rate for the entire group approached 75 percent. The patients with left axis deviation had greater cardiovascular mortality (P less than 0.05). In conclusion, among patients with left bundle branch block, those with left axis deviation have a greater incidence of myocardial dysfunction, more advanced conduction desease and greater cardiovascular mortality than those with a normal axis.

Bundle-Branch Block↗
PubMed1978

A comparison of the in vitro metabolism of biphenyl and 4-chlorobiphenyl by rat liver microsomes.

The comparative metabolism of the hydrocarbons, biphenyl and 4-chlorobiphenyl, was investigated using two different preparations of rat hepatic microsomes. The assay was designed to account for all the metabolic products which included the ether soluble lipophilic metabolites, low molecular weight conjugates, and macromolecular adducts, and to determine the effects of induction with Aroclor 1254 and 1248, two commercial polychlorinated biphenyl (PCB) preparations. 4-chlorobiphenyl was the more metabolically active substrate with the induced and control enzymes. In most metabolic fractions biphenyl was less inducible by the PCB's, with the exception of the 2-biphenylol metabolite which was induced ca. 18-fold. Preincubation of the microsomes with carcinogens did not enhance biphenyl 2-hydroxylation. Instead, a general inhibition of metabolic activity was observed for both biphenyl and 4-chlorobiphenyl substrates. Preincubation with phenobarbitone, a noncarcinogen, did not change the microsome-mediated metabolism of biphenyl or 4-chlorobiphenyl. The substitution of a single halogen atom on the biphenyl nucleus altered both the reactivity and pattern of metabolites for these substrates.

Animals↗
PubMed1978

Normalization of bundle branch block patterns by distal His bundle pacing. Clinical and experimental evidence of longitudinal dissociation in the pathologic his bundle.

Clinical and experimental observations in which bundle branch block patterns (BBBP) in ECG leads were normalized by distal His bundle (H) pacing are reported. The clinical material includes four patients with acute right BBBP secondary to anterior wall myocardial infarction and three patients with chronic left BBBP. Six of the seven patients had a prolonged H-V interval (60-85 msec) including three who showed evidence of an intra-H conduction delay (IHCD) with split H (H and H'). Distal H pacing from a right-sided electrode catheter normalized the BBBP with a stimulus-to-QRS (PI-V) interval 20-35 msec shorter than the H-V interval and almost identical to the H'-V interval in the three patients with documented IHCD. In 18 dogs ligation of the anterior septal artery resulted in IHCF with split H associated with right or left BBBP. Distal H pacing from catheter and/or plunge wire electrodes normalized the BBBP in 12 experiments (67%) with a PI-V interval identical to the H'-V interval. H pacing was selective and direct stimulation of myocardium was excluded by monitoring the high ventricular septal electrogram. The clinical and experimental observations are discussed as evidence that functional longitudinal dissociation is probably only operative in the pathologic H due to selectively greater depression of conduction in the transverse interconnections.

Animals↗
PubMed1977

Clinical significance of prolonged sinoatrial conduction time.

Prolonged (greater than 152 msec) calculated sinoatrial conduction times (SACT) were found in 24 of 470 patients studied by the atrial extrastimulus technique, ranging from 155 to 220 msec (180+/-4.4; mean+/-SEM). There were 18 males and six females with ages of 29 to 85 (mean 65+/-2.6). Electrocardiographic monitoring revealed significant sinus or atrial dysrhythmias in 19 (79%) patients. Of these 19, 15 had persistent sinus bradycardia and/or sinoatrial block, three had sinus bradyarrhythmia with paroxysmal atrial tachycardia, and one had isolated atrial tachycardia. Additional electrophysiological evidence of sinus node or atrial dysfunction was present in 11 patients. Four patients needed permanent pacing during follow-up (mean follow-up period of 427+/-39 days) because of symptomatic bradyarrhythmia. Three patients died, none suddenly. In conclusion, prolonged calculated SACT was associated with a high incidence of electrocardiographic and electrophysiologic abnormalities of sinus node and/or atrium. Despite this, bradyarrhythmic morbidity was relatively low, suggesting that prolonged sinoatrial conduction time in the absence of symptoms is not an indication for prophylactic pacing.

Adult↗
PubMed1977

Participation of fast and slow A-V nodal pathways in tachycardias complicating the Wolff-Parkinson-White syndrome. Report of a case.

Electrophysiological studies in one patient with type B pre-excitation and dual A-V nodal pathway revealed several types of paroxysmal narrow QRS tachycardia (PSVT). One type of PSVT reflected antegrade fast A-V nodal pathway and retrograde anomalous pathway conduction. This PSVT was characterized by early retorgrade activation of right atrial appendage, P following QRS and cycle length of 290 to 350 msec. A second PSVT reflected antegrade slow A-V nodal pathway and retrograde anomalous pathway conduction. This PSVT was characterized by early retrograde activation of right atrial appendage, P following QRS, and cycle length of 440 msec. A third PSVT reflected A-V nodal re-entrance with antegrade slow pathway and retrograde fast pathway conduction. This PSVT was characterized by normal retrograde atrial activation sequences, P simultaneous with QRS, and cycle length of 320 msec. All PSVT inductions could be explained in terms of antegrade and retrograde properties of fast and slow A-V nodal and anomalous pathways.

Adult↗
PubMed1977

Sites of conduction disease in aortic stenosis: significance of valve gradient and calcification.

Electrophysiologic studies were done in 32 patients with aortic stenosis. In 24 patients with intact A-V conduction, A-H intervals ranged from 55 to 145 msec and were prolonged in two. Two had split His bundle potentials. The H-V intervals ranged from 25 to 94 msec and were prolonged in 12. The mean H-V interval was 63 +/- 2.6 msec in 12 patients with calcific aortic stenosis compared with 50 +/- 4.9 msec in 12 without calcification (P less than 0.05). The mean H-V in 10 patients with aortic gradients greater than 40 mm Hg was 62 +/- 5.6 msec compared with 47 +/- 3.1 msec in nine with gradients less than 40 (P less than 0.05). In patients with aortic stenosis and A-V block, the site of the block was distal to the His bundle in three and within the His bundle in five. All eight had calcified valves. Aortic stenosis was commonly associated with latent and manifest conduction disease in the His bundle and the trifascicular conduction system. Conduction disease was more extensive with calcified valves and greater valve obstruction.

Adult↗
PubMed1976

Significance of A-H interval in patients with chronic bundle branch block. Clinical, electrophysiologic and follow-up observations.

His bundle electrograms were recorded in 308 adults with chronic bundle branch block. The A-H interval was normal in 249 patients and prolonged in 59. Comparison of patients with normal and prolonged A-H intervals revealed a greater incidence of demonstrable organic heart disease in the latter (P less than 0.01). Dyspnea, cardiomegaly and congestive heart failure were more frequent in patients with A-H prolongation. These patients also had longer P-R intervals and atrioventricular (A-V) nodal effective refractory periods, lower paced rates producing second degree A-V block proximal to the His bundle and a greater frequency of H-V prolongation. All patients were prospectively followed up in a conduction disease clinic with mean follow-up periods (+/- standard error of the mean) of 523 +/- 23 and 588 +/- 47 days in the patients with normal and prolonged A-H intervals, respectively. Seven (3 percent) of the patients with a normal A-H interval had A-V block with probable or definite site of block proximal to the His bundle in three and distal to the His bundle in four. In five of the six patients with a prolonged A-H interval who experienced A-V block (10 percent), the probable or definite site of block was proximal to the His bundle. Mortality (both sudden and nonsudden) was not significantly different in the patients with normal and prolonged A-H intervals. In summary, A-H prolongation was associated with increased incidence of organic heart disease and myocardial dysfunction. The risk of development of A-V nodal block was greater in patients with a prolonged A-H interval but appeared to be of minimal clinical significance.

Adolescent↗
PubMed1976

Electrophysiologic effects of atropine on human sinus node and atrium.

Electrophysiologic studies were conducted in 17 patients without apparent sinus node disease before and after intravenous administration of 1 to 2 mg of atropine. Mean values in milliseconds (+/- standard error of the mean) before and after administration of atropine were as follows: sinus cycle length 846 +/- 26.4 versus 647 +/- 20.0 (P less than 0.001); sinus nodal recovery time 1,029 +/- 37 versus 774 +/- 36 (P less than 0.001); mean calculated sinoatrial (S-A) conduction time 103 +/- 5.7 versus 58 +/- 3.9 (P less than 0.001); mean P-A interval 34 +/- 1.5 msec versus 31 +/- 1.5 (P less than 0.05); mean atrial effective and functional refractory periods during sinus rhythm 285 +/- 11.3 versus 238 +/- 7.9 and 331 +/0 11.6 versus 280 +/- 8.6, respectively (P less than 0.001 for both); mean atrial effective and functional refractory periods measured at equivalent driven cycle length 239 +/- 7.7 versus 213 +/- 7.4 and 277 +/- 11.4 versus 245 +/- 9.5, respectively (P less than 0.001 for both). In conclusion, atropine shortened sinus cycle length, sinus nodal recovery time and calculated S-A conduction time. The shortening of atrial refractory periods with atropine implies that vagotonia prolongs atrial refractoriness in man.

Adult↗
PubMed1976

Electrophysiologic demonstration of bilateral anomalous pathways in a patient with Wolff-Parkinson-White syndrome (type B preexcitation).

Pre- and postoperative electrophysiologic studies are described that were suggestive of two (right- and left-sided) anomalous atrioventricular (A-V) connections in a patient with type B Wolff-Parkinson-White syndrome and intractable arrhythmias, who underwent epicardial mapping and successful surgical ablation of the right-sided anomalous pathway. The presence of the right-sided anomalous pathway capable of both antegrade and retrograde conduction was suggested by the following observations: (1) Type B preexcitation on the surface electro-cardiogram; (2) maximal preexcitation and minimal stimulus-delta with low lateral right atrial pacing; (3) epicardial mapping of the atria and ventricles; and (4) disappearance of ventricular preexcitation after surgical ablation of the right-sided anomalous pathway. The presence of an additional left-sided anomalous pathway capable of only retrograde conduction (concealed on the surface electrocardiogram) was sugg-sted by the following observations: (1) Left to right retrograde atrial activation sequence during reentrant tachycardia and ventricular pacing at rapid rates and with coupled ventricular pacing postoperatively; (2) spontaneous conversion of wide ORS tachycardia utilizing the anomalous pathway for antegrade conduction to narrow QRS tachycardia with significant slowing in rate; and (3) smooth antegrade A-V nodal conduction curves with echo zone postoperatively. The demonstration of bilateral anomalous pathway in patients with preexcitation has important electrophysiologic and surgical implications.

Adolescent↗
PubMed1976

Electrophysiologic effects of atropine on sinus node and atrium in patients with sinus nodal dysfunction.

Electrophysiologic studies were conducted in 21 patients with sinus nodal dysfunction before and after intravenous administration of 1 to 2 mg of atropine. The mean sinus cycle length (+/- standard error of the mean) was 1,171 +/- 35 msec before and 806 +/- 29 msec after administration of atropine (P less than 0.001). Mean sinus nodal recovery time determined at a aced rate of 130/min and maximal recovery time were, respectively, 1,426 +/- 75 and 1,690 +/- 100 msec before and 1,169 +/- 90 and 1,311 +/- 111 msec after atropine (P less than 0.001 and less than 0.001). Mean calculated sinoatrial conduction time, measured in 16 patients, was 113 +/- 8 msec before and 105 +/- 9.7 msec after atropine (difference not significant). Mean atrial effective refractory period, measured at an equivalent driven cycle length, was 262 +/- 11.1 msec before and 256 +/- 10.3 msec after atropine (not significant). Mean atrial functional refractory period was 302 +/- 12.5 msec before and 295 +/- 11.3 msec after atropine (not significant). The shortening of sinus cycle length and sinus recovery time with atropine was similar to that noted in patients without sinus nodal dysfunction. In contrast, atropine had insignificant effects on sinoatrial conduction and atrial refractoriness in this group whereas it shortens both in normal subjects. This finding may reflect altered perinodal and atrial electrophysiologic properties in patients with sinus node disease.

Adult↗
PubMed1976

Catheter mapping of retrograde atrial activation. Observations during ventricular pacing and AV nodal re-entrant paroxysmal tachycardia.

A systematic study of retrograde atrial sequence at commonly used electrode catheter recording sites in 8 patients without, and in 4 patients with AV nodal re-entrant paroxysmal tachycardia was made. During right ventricular pacing, the retrograde atrial activation sequence was low septal right atrium--proximal coronary sinus--distal coronary sinus--high right atrium. During the episodes of paroxysmal tachycardia, a similar pattern was observed. This information should be helpful in the understanding of abnormal activation sequences in patients with paroxysmal supraventricular tachycardia in whom retrogradely conducting anomalous pathways are suspected.

Adult↗
PubMed1976

Electrophysiological studies in patients with chronic recurrent ventricular tachycardia.

Seventeen consecutive patients with chronic recurrent ventricular tachycardia (VT) were studied in an attempt to delineate the reproducibility and mechanism of this arrhythmia. Six patients had nonsustained and 11 had sustained VT. The following electrophysiological techniques were utilized in an attempt to reproduce VT: 1) rapid atrial and ventricular pacing (17 pts); 2) atrial extrastimulus technique (17 pts); 3) ventricular extrastimulus technique (17 pts); 4) V1V2V3 stimulation technique (5 pts); 5) ventricular pacing from two or more sites (5 pts). Ventricular tachycardia was induced in six of 11 (54%) patients with sustained VT. However, in four there was only a single induction and only in the remaining two patients could VT be repetitively induced. In the latter two patients ventricular tachycardia was induced with both atrial and ventricular stimulation. Ventricular tachycardia could not be induced in any patient with nonsustained VT, although three had spontaneous episodes of ventricular tachycardia during study. In conclusion, in the present series of patients with chronic recurrent VT, this rhythm could not be reproducibly induced in the majority of patients in the cardiac catheterization laboratory utilizing catheter stimulation techniques.

Action Potentials↗
PubMed1976

The clinical spectrum of chronic His bundle block.

This report details our total experience with documented chronic His bundle block in 24 patients. Ten patients had second-degree block (eight with 2:1 block and two with type-1 block), and 14 patients had complete heart block. There were 16 women (67 percent) and eight men (33 percent) with ages ranging from 17 to 87 years. Diagnoses were as follows: hypertensive cardiovascular disease, nine patients (38 percent); arteriosclerotic heart disease, six patients (25 percent); aortic valvular disease, three patients (13 percent); primary conduction disease, two patients (8 percent); primary myocardial disease, two patients (8 percent); congenital heart block, one patient (4 percent); and traumatic heart block, one patient (4 percent). Pacing was instituted in 20 patients because of the following; congestive heart failure, seven patients; syncope, seven patients; fatigue, four patients; and recurrent dizziness, two patients. Permanent pacing was indicated within ten days of initial diagnosis in 13 patients, from 20 to 80 days in four patients, and later than 100 days in three patients. An additional two asymptomatic patients were treated with prophylactic pacing.

Adolescent↗
PubMed1976

The in vitro metabolism, macromolecular binding and bacterial mutagenicity of 4-chloribiphenyl, a model PCB substrate.

The in vitro metabolism of 4-chlorobiphenyl, a model polychlorinated biphenyl (PCB) substrate, proceeds via an arene oxide intermediate to give the observed in vivo hydroxylated metabolites. The rabbit liver microsomal fraction mediates binding between the PCB and the endogenous microsomal protein and RNA and the major part of the PCB was bound to the light 3S-10S RNA fraction. The lower chlorinated 4-chlorobiphenyl isomer was highly mutagenic to the Salmonella typhimurium strain TA1538 (sensitive to frameshift mutagens) whereas higher chlorinated PCB were only weakly mutagenic.

Animals↗
PubMed1975

Sinus nodal responses to atrial extrastimuli in patients without apparent sinus node disease.

In 36 patients without sinus node disease scanning with an atrial extrastimulus (A2) was performed during sinus rhythm with the sinus cycle length measured in milliseconds. Zones of nonreset due to interference, reset, interpolation and sinus echoes were defined by noting the timing of the first response after A2. Zones were defined in terms of their longest and shortest A1-A2 coupling intervals (in milliseconds). A zone of nonreset was found in 12 of 12 patients in whom A2 was delivered late. The mean cycle length in these 12 patients was 779 msec, with a mean zone of nonreset of 779 to 585 msec (25 percent of cycle length). All 36 patients (100 percent) had a zone of reset. The mean cycle length in these 36 patients was 803 msec with a zone of reset from 692 to 319 msec (46 percent of cycle length). Seven of 36 patients (19 percent) had a zone of interpolation. The mean cycle length in these seven patients was 754 msec, with a mean zone of interpolation of 344 to 279 (9 percent of cycle length). Four of 36 patients (11 percent) had a zone of sinus echoes. The mean cycle length in these four patients was 870 msec, with a mean zone of echoes from 350 to 313 msec (4 percent of cycle length). Calculated sinoatrial conduction time ranged from 40 to 153 msec (mean +/- standard deviation 92 +/- 30 msec). Shortening of the cycle length with atrial pacing increased the number of patients with zones of interpolation and echoes. In conclusion, zones of nonreset and reset are found in all patients with normal sinus nodal function, whereas zones of interpolation and echoes are much less common. Sinoatrial conduction time is surprisingly long in patients without apparent sinus node disease.

Adult↗