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Biomedical subjects

D L Ross

Publications and source records attributed to D L Ross.

At least 109 records · Page 6Linked to original sources
PubMed1986

Regulation of plasma arginine vasopressin in patients with chronic renal failure maintained on hemodialysis.

Plasma arginine vasopressin (PAVP) was studied in patients before and after hemodialysis. The levels of PAVP were higher before and reverted to normal range after dialysis (5.7 vs. 2.7 pg/ml). Sequential chemical dialysis showed that vasopressin was removed during the chemical dialysis phase. Data obtained during a simulation experiment were also consistent with the view that vasopressin was removed during the chemical dialysis phase.

Arginine Vasopressin↗
PubMed1986

Prognostic significance of ventricular tachycardia and fibrillation induced at programmed stimulation and delayed potentials detected on the signal-averaged electrocardiograms of survivors of acute myocardial infarction.

The relative prognostic significance of ventricular tachycardia and ventricular fibrillation inducible at programmed stimulation within 1 month of acute myocardial infarction was compared in a prospective study of 403 clinically well survivors of transmural infarction who were 65 years old or younger. The prognostic significance of delayed potentials on the signal-averaged electrocardiogram was also examined in a subset of 306 patients without bundle branch block. Among the study patients, 20% had inducible ventricular tachycardia, 14% had inducible ventricular fibrillation, and 66% had no inducible arrhythmias. The 2 year probability of remaining free from cardiac death or nonfatal ventricular tachycardia or fibrillation was 0.73 for those with inducible ventricular tachycardia, 0.93 for those with inducible ventricular fibrillation, and 0.92 for those with no inducible arrhythmias. The cycle length of inducible ventricular tachycardia was 230 msec or more in 70% of the patients with inducible tachycardia who died. Of the patients studied by signal-averaged electrocardiography, 26% had delayed potentials. At 2 years, the probability of remaining free from cardiac death or nonfatal ventricular tachycardia or fibrillation was 0.73 for patients with delayed potentials and 0.95 for patients with no delayed potentials. There was a significant correlation (p less than .001) between the presence of delayed potentials and the ability to induce ventricular tachycardia. In conclusion, in survivors of recent infarction who have not had spontaneous ventricular tachycardia or fibrillation, inducible tachycardia (but not inducible fibrillation) at programmed stimulation predicts a significant risk of death or spontaneous tachycardia or fibrillation. A similar risk is found for patients with delayed potentials on the signal-averaged electrocardiogram.

Adult↗
PubMed1986

Suppressed pituitary ACTH response after ACTH treatment of infantile spasms.

Suppression of an adrenocorticotropic hormone (ACTH) response to insulin hypoglycemia has been reported in ACTH-treated adults. There are no guidelines for withdrawal of ACTH treatment in children. After observing suppressed morning cortisol in several children, insulin tolerance tests were performed in five children within 48 hours after tapered withdrawal of ACTH treatment for myoclonic seizures. ACTH response, as determined by cortisol and beta-endorphin radioimmunoassay, was adequate in four of the children. One child showed low basal levels and minimal elevation during hypoglycemia for both beta-endorphin (0 to 3 pg/ml) and cortisol (3.6 to 4.4 micrograms/dL) on initial testing, but normal responses six weeks later. Measurement of beta-endorphin response supported a central basis for suppression in the child, who had had an adrenal hemorrhage during gram-negative sepsis while on ACTH. ACTH release is transiently suppressed in some children after exogenous ACTH treatment. Tapered withdrawal and stress coverage is recommended.

Adrenocorticotropic Hormone↗
PubMed1985

Value of programmed stimulation and exercise testing in predicting one-year mortality after acute myocardial infarction.

The ability of programmed ventricular stimulation and exercise testing to predict 1-year mortality after acute myocardial infarction (AMI) was investigated in 228 clinically well survivors of AMI. Patients with inducible ventricular tachycardia (VT) or ventricular fibrillation (VF) had a higher mortality rate than those without inducible arrhythmias (26% vs 6%, p less than 0.001). Exercise-induced ST-segment change of 2 mm or more was associated with a higher mortality rate than ST change of less than 2 mm (11% vs 4%, 0.05 less p less than 0.10). Of patients who had both tests, 62% had no inducible ventricular tachycardia or ventricular fibrillation and ST change of less than 2 mm, and only 1% died during the first year. Thus, in clinically well survivors of AMI, programmed stimulation is a powerful predictor of first-year mortality; programmed stimulation and exercise testing together predict virtually all deaths within the first year, and they can identify a large group of patients with a very low mortality rate.

Adult↗
PubMed1985

Curative surgery for atrioventricular junctional ("AV nodal") reentrant tachycardia.

A new surgical approach was studied prospectively in 10 consecutive patients with atrioventricular (AV) junctional reentrant tachycardia. The aim was to abolish tachycardia yet preserve normal AV conduction. On the basis of electrophysiologic study before operation, patients were classified as type A (ventriculoatrial [VA] intervals during tachycardia less than or equal to 40 ms) (seven patients) or type B (VA intervals greater than 40 ms) (three patients). Dual AV junctional pathways were demonstrable with single extrastimulus testing in seven patients before operation. Endocardial mapping during tachycardia at surgery revealed earliest atrial activation anteromedial to the AV node in type A patients and posterior to the node in the type B patients. The perinodal atrium in the region of earliest atrial activation during tachycardia was carefully disconnected from the AV node. After operation, AV junctional reentrant tachycardia was not inducible at comprehensive electrophysiologic study in any patient, and no clinical recurrences have occurred during a follow-up period of 2 to 14 months (mean 8 +/- 4). Normal AV conduction was preserved in all cases. Anterograde slow AV junctional pathway conduction was abolished in five of seven cases. Retrograde His to atrium conduction time was prolonged in type A patients but the capacity for retrograde VA conduction remained excellent. Retrograde His to atrium conduction was interrupted or severely compromised in the type B patients. These data show that there are at least two types of AV junctional reentry. Perinodal atrium appears to be part of the reentrant circuit in human AV junctional reentry. Although the most consistent effect of surgery was on the retrograde limb of the circuit, anterograde slow pathway conduction was also modified. AV junctional reentry is surgically curable with a high success rate.

Adult↗
PubMed1984

Trigeminal schwannoma in a child.

A 5-year-old girl presented with headache, vomiting, flushing, ptosis, and paroxysmal tachycardia. The neurological findings were partial motor and sensory left trigeminal palsy, left conductive hearing defect, and left cerebellar deficit. The radiological and neuropathological findings were typical for trigeminal schwannoma, which is rare in childhood. The present patient is the youngest yet recorded.

Child, Preschool↗
PubMed1983

Safety and efficacy of intravenous quinidine.

The safety and efficacy of intravenous quinidine were evaluated in a patient population with a high prevalence of left ventricular dysfunction and intraventricular conduction delays. Quinidine gluconate (mean dose 9.1 +/- 1.6 mg/kg) was administered during electrophysiologic study to 100 patients with ventricular or supraventricular tachyarrhythmias. Clinical heart failure was present in 68 percent of the patients. Left ventricular end-diastolic pressure, cardiac index, and left ventricular ejection fraction were abnormal in 62, 48, and 70 percent, respectively. Major intraventricular conduction delays (QRS of 120 msec or more) were present in 27 percent, and the H-V interval was prolonged (over 55 msec) in 28 percent. Despite the prevalence of these abnormalities, quinidine was discontinued because of hypotension in only 10 patients. Saline solution was infused to maintain preload in 37 percent, and hypotension responded promptly to saline solution infusion or discontinuation of quinidine infusion in all subjects. Hypotension was not more common in patients with more severe left ventricular dysfunction. QRS duration, H-V interval, QTc, and right ventricular effective refractory period increased significantly (p less than 0.001) after quinidine administration. Heart block or QRS widening of 50 percent or more did not occur. Quinidine prevented arrhythmia induction in 26 percent of patients who received full doses. Ventricular tachycardia cycle length increased in all 41 patients in whom identical forms were induced before and after quinidine (287 +/- 71 msec versus 361 +/- 93 msec, p less than 0.001). Intravenous quinidine may be administered safely to patients with intraventricular conduction delays and moderate heart failure. When antiarrhythmic efficacy is assessed by electrophysiologic study, quinidine compares favorably with other antiarrhythmic agents.

Arrhythmias, Cardiac↗
PubMed1983

Clinical factors predicting successful electrophysiologic-pharmacologic study in patients with ventricular tachycardia.

Data from 142 patients who had sustained ventricular tachycardia or ventricular fibrillation were analyzed to determine if clinical variables predict response to antiarrhythmic drugs at electrophysiologic study. Effective antiarrhythmic drugs were identified for 43 patients (30%). Ten of 25 variables analyzed were univariate predictors of drug response at the probability (p) level of less than 0.05. Stepwise logistic regression identified three variables independently predictive of drug response: fewer coronary arteries with 70% or greater stenosis (p less than 0.001), female sex (p less than 0.002) and fewer episodes of arrhythmia (p less than 0.03). A function incorporating these three variables was constructed to predict the probability of drug response, and ranges of the predictor function corresponding to high, intermediate and low probabilities of drug response were identified. Response rates in the high (greater than 50%), intermediate and low (less than 10%) probability ranges were 28 (58%) of 48, 10 (27%) of 37 and 5 (9%) of 57, respectively. Thus 40% of the patients who had a less than 10% likelihood of benefit from electrophysiologic-pharmacologic study were classified into the low probability range. When the predictor function was applied prospectively to 25 additional patients, response rates in the three probability ranges were 3 (50%) of 6, 1 (12%) of 8 and 0 (0%) of 11. These data show that analysis of clinical variables can be used to estimate the probability of benefit from electrophysiologic-pharmacologic study.

Anti-Arrhythmia Agents↗
PubMed1983

Delayed termination of re-entrant atrioventricular nodal tachycardia.

Termination of atrioventricular nodal (AVN) re-entrant tachycardia by one or two induced premature beats generally occurs within one tachycardia cycle from the last premature beat. Two cases are described in which programmed stimulation during sustained re-entrant AVN tachycardia caused delayed termination in the second or third tachycardia cycle following the extrastimuli. The site of block was the antegrade pathway in one case and the retrograde pathway in the other. The most likely mechanism was induced second degree block in one limb of the tachycardia circuit. Delayed termination provided evidence for concealed penetration of the tachycardia circuit in one case. We conclude that delayed termination of tachycardia is not an indicator of the underlying mechanism of tachycardia. Delayed termination may reveal concealed penetration of the tachycardia circuit. Lastly, in unusual cases programmed stimulation may fail to cause immediate termination of re-entrant tachycardia but may perturb the tachycardia circuit enough to cause termination in subsequent tachycardia cycles.

Atrioventricular Node↗
PubMed1982

Decreased incidence of antiarrhythmic drug efficacy at electrophysiologic study associated with the use of a third extrastimulus.

Drug trials during electrophysiologic study were performed in 166 patients with sustained ventricular tachycardia (VT) or ventricular fibrillation. In the first 21 patients (group I), a maximum of two extrastimuli was used. In 145 subsequent patients (group II), drug efficacy was assessed using three extrastimuli if one or two failed to induce VT. The incidence of acute drug efficacy was 15 of 21 (71%) in group I, but only 44 of 145 (30%) in group II (p less than 0.01). To assess the influence of the third extrastimulus on the differing incidence of acute drug efficacy, we examined the 69 group II patients whose VT was initially induced by one or two extrastimuli. Acutely effective agents were identified for 19 of these 69 patients using up to three extrastimuli to define efficacy. In 24 of te 50 patients for whom no effective drug could be found, VT was induced with one or two extrastimuli during all drug trials. In the remaining 26 patients VT could be induced after drug administration only with use of three extrastimuli. If efficacy had been defined using a maximum of two extrastimuli, these 26 patients would have been considered responsive to drug testing. Overall, 45 to 69 (65%) rather than 19 of 69 (28%) would have had a favorable response (p less than 0.001). Fourteen group I patients and 17 group II patients in whom VT was initially induced by one or two extrastimuli received chronic therapy with agents predicted effective during acute drug trials. At 18 months, the cumulative percent of patients free of arrhythmia recurrence by actuarial analysis was 79 +/- 14% in group I and 80 +/- 14% in group II (NS). Use of three extrastimuli during drug trials is associated with a lower incidence of acute drug efficacy. Limited data suggest that prophylaxis against VT induction by three, rather than two, extrastimuli may not be a stronger predictor of chronic efficacy in patients whose VT is initially induced by one or two extrastimuli. Further study is needed to identify optimal pacing methods for antiarrhythmic drug assessment.

Anti-Arrhythmia Agents↗
PubMed1982

Programmed ventricular stimulation in predicting vulnerability to ventricular arrhythmias and their response to antiarrhythmic therapy.

In predicting vulnerability to ventricular arrhythmias and their response to antiarrhythmic therapy, several factors and questions need to be considered, including the following. (1) Ventricular tachycardia (VT) can be induced in most patients who have recurrent sustained VT. (2) Because induced VT can often be pace terminated, termination by pacing should be attempted before cardioversion is applied. (3) Acutely effective antiarrhythmic agents are no longer being found for the majority of patients undergoing electrophysiologic-pharmacologic study in our series. (4) Specific VT-induction programs affect both the inducibility of VT and acute efficacy of drugs at electrophysiologic study; this point requires examination. (5) Arrhythmia-induction studies may not product high yield in patients with clinical ventricular fibrillation or unsustained VT. (6) It is as yet unclear whether some drugs, such as amiodarone, can be accurately evaluated by using arrhythmia-induction techniques. (7) Induction of the repetitive ventricular response by V2 stimulation is not a useful method for antiarrhythmic drug selection in patients with recurrent ventricular tachyarrhythmias. (8) Adequate data do not yet exist to identify either the ECG-monitoring technique or the arrhythmia-induction technique as the preferred method for selecting antiarrhythmic drugs for chronic therapy of patients with recurrent ventricular tachyarrhythmias. A study to compare the accuracies of the two techniques is both feasible and needed.

Amiodarone↗
PubMed1982

Relative efficacy of blind left ventricular aneurysm resection for the treatment of recurrent ventricular tachycardia.

Coronary arterial bypass grafting and left ventricular aneurysm resection and the two combined have been reported effective in control of refractory ventricular tachyarrhythmias; 82 percent of a pool of 127 patients (from 22 reports) survived after surgery. However, the follow-up period in this group is short and the extent of medical therapy is not well defined. Actuarial analysis of results of conventional left ventricular aneurysm resection in 32 Stanford patients with well documented ventricular tachyarrhythmias shows an arrhythmia recurrence rate of 50 +/- 9 percent (mean +/- standard error of the mean) during the postoperative hospitalization. In contrast, after 10 months only 11 +/- 9 percent of 18 patients who underwent myocardial resection guided by intraoperative electrical activation sequence mapping experienced arrhythmia recurrence. These data demonstrate that simple left ventricular aneurysm resection is less effective in preventing ventricular tachyarrhythmias than originally believed. Preliminary data suggest that surgery of the left ventricle guided by intraoperative mapping may provide more effective control of ventricular tachyarrhythmias. However, intraoperative mapping has many technical and interpretive problems. Investigations are needed to determine the roles of conventional and new operative approaches to treatment of medically refractory ventricular tachyarrhythmias.

Aged↗
PubMed1982

Circular dichroism studies on conformational transitions of phytohemagglutinins effected by some alcohols.

The effects of methanol, ethanol, 1-propanol and 2,2,2,-trifluoroethanol (TFE) on conformation of 10 phytohemagglutinins (lectins) were examined by applying the circular dichroism (CD) method. Concanavalin A and the lectins isolated from pea (Pisum sativum), lentil (Lens culinaris), soybean (Glycine max), peanut (Arachis hypogaea), Dolichos biflorus, Sophora japonica, Lotus tetragonolobus, Ulex europaeus I, and Phaseolus vulgaris (leucoagglutinin) were used. Slight changes in the structure of these proteins were observed at relatively low concentrations (5-20 vol. %, pH 7.2-8.2, at 22-25 degrees) of the perturbants, and the effectiveness of the alcohols increased with their concentration and molecular weight. The circular dichroism bands related to the aromatic side chain chromophores decreased in the presence of the alcohols. The secondary structure was reorganized by high concentrations (30-80 vol. %) of the alcohols, as indicated by CD at 187-250 nm. Curves typical for proteins of relatively high alpha-helix content (strong positive CD bands at 191 nm and negative bands at 206-208 and 222 nm) were recorded in the presence of high concentrations of trifluoroethanol.

Alcohols↗
PubMed1982

Cycle length alternation in circus movement tachycardia using an atrioventricular accessory pathway. A study of the role of the atrioventricular node using a computer model of tachycardia.

The possible role of the atrioventricular nodal (AVN) function curve during tachycardia as a cause of cycle length alternation was investigated using a computer model of circus movement tachycardia utilizing an atrioventricular accessory pathway. Two types of AVN function curves during tachycardia were entered into the computer: straight lines of various gradients and representative examples of patient-based AVN function curves obtained during clinical electrophysiologic studies. Perturbations of the tachycardia model were induced by introducing a short cycle, by suddenly prolonging a conduction interval, or by moving the AVN function curve relative to that in stable tachycardia. Using the straight line AVN function curves, stable, sustained cycle length alternation could be induced by perturbation of the tachycardia cycle if the gradient of the line was -1 (slope = 45 degrees). If the gradient was more than -1 (slope less than 45 degrees), the perturbation was damped. If the gradient was less than -1 (slope greater than 45 degrees), the perturbation was amplified, leading to termination of tachycardia by block in the AVN. Similar but more complex responses to perturbation of tachycardia were found using patient-based AVN function curves. Thus, sustained cycle length alternation and amplification or damping of perturbation could be produced. Using physiologic AVN function curves, the response to perturbation of tachycardia depended on the interrelationship of the shape of the AVN function curve, the location of the cycle length of tachycardia on the curve, the magnitude and direction of the perturbation, and the AVN effective refractory period. We conclude that cycle length alternation during tachycardia may be explained by the characteristics of a single antegrade AVN function curve without postulating the presence of additional AVN pathways. The stability of circus movement tachycardias depends on the interaction of several variables.

Atrioventricular Node↗