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Biomedical subjects

A B Simon

Publications and source records attributed to A B Simon.

At least 19 recordsLinked to original sources
PubMed1992

Effect of digitalis on norepinephrine kinetics in congestive heart failure.

OBJECTIVE: The aim of this study was to test the hypothesis that digitalis glycosides would reduce sympathetic activity as reflected by forearm venous norepinephrine kinetics in patients with congestive heart failure. BACKGROUND: Digitalis glycosides have been reported to decrease sympathetic nervous system activity with baroreceptor sensitization in experimental animals. Such effects could be of therapeutic importance in congestive heart failure. METHODS: Double-blind randomized assessment was made of the effects of low dose intravenous deslanoside (Cedilanid-D, 0.002 mg/kg body weight) and vehicle on heart rate, arterial pressure, forearm blood flow, plasma norepinephrine, norepinephrine clearance and norepinephrine spillover in nine patients with stable congestive heart failure, New York Heart Association functional class II or III. Open label assessment of the responses to 0.6 mg of deslanoside was made in an overlapping group of seven patients. All measurements were made 30 and 60 min after intravenous injection of drug or vehicle and after 15 min of 30 degrees head-down tilt as a test of the sympathetic response to baroreceptor loading. RESULTS: Heart rate, arterial pressure and forearm blood flow were unchanged by low dose deslanoside. Heart rate decreased slightly with the 0.6 mg dose with the patients in the supine position. Norepinephrine spillover and clearance decreased with time on each study day in the supine position, but no effect was attributable to digitalis. Plasma norepinephrine and norepinephrine clearance and spillover all remained unchanged during head-down tilt on each study day. CONCLUSIONS: Nonpressor doses of deslanoside do not suppress sympathetic activity as reflected by venous norepinephrine and norepinephrine spillover in patients with congestive heart failure. Further, deslanoside did not normalize the sympathetic response to mild baroreceptor loading produced by head-down tilt. These data do not support sympathoinhibition through baroreceptor sensitization as a likely effect of digitalis in congestive heart failure.

Deslanoside↗
PubMed1984

Plasma norepinephrine as a guide to prognosis in patients with chronic congestive heart failure.

Hemodynamics, plasma norepinephrine, and plasma renin activity were measured at supine rest in 106 patients (83 men and 23 women) with moderate to severe congestive heart failure. During follow-up lasting 1 to 62 months, 60 patients died (57 per cent); 47 per cent of the deaths were sudden, and 45 per cent were related to progressive heart failure. Statistically unrelated to the risk of mortality were cause of disease (60 patients had coronary disease, and 46 had cardiomyopathy), age (mean, 54.8 years), cardiac index (mean, 2.11 liters per minute per square meter of body-surface area), pulmonary wedge pressure (mean, 24.5 mm Hg), and mean arterial pressure (mean, 83.2 mm Hg). A multivariate analysis of the five significant univariate prognosticators--heart rate (mean, 84.4 beats per minute), plasma renin activity (mean, 15.4 ng per milliliter per hour), plasma norepinephrine (mean, 700 pg per milliliter), serum sodium (mean, 135.7 mmol per liter), and stroke-work index (mean, 21.0 g-meters per square meter)--found only plasma norepinephrine to be independently (P = 0.002) related to the subsequent risk of mortality. Norepinephrine was also higher in patients who died from progressive heart failure than in those who died suddenly. These data suggest that a single resting venous blood sample showing the plasma norepinephrine concentration provides a better guide to prognosis than other commonly measured indexes of cardiac performance.

Age Factors↗
PubMed1984

Abnormalities in myocardial perfusion during tachycardia in dogs with left ventricular hypertrophy: metabolic evidence for myocardial ischemia.

This study tested the hypothesis that in the chronically hypertrophied left ventricle pacing stress may cause abnormalities of perfusion that result in myocardial ischemia. Left ventricular hypertrophy (LVH) was produced by banding the ascending aorta of 10 dogs at 6 weeks of age, and studies were carried out after the animals had reached adulthood and when mean left ventricular/body weight ratio was 74% greater than in eight control dogs. Myocardial blood flow was measured with microspheres during pacing at 100, 200, and 250 beats/min, while aortic and coronary sinus blood samples were obtained for determination of concentrations of lactate and the adenosine metabolites inosine and hypoxanthine. In the control dogs, increasing heart rates were associated with an increase in mean myocardial blood flow while subendocardial flow was maintained at a level equal to or greater than subepicardial flow. Myocardial lactate uptake ranged from +60% to -5%, and adenosine metabolites were not detected in coronary sinus blood (less than 0.5 microM/l). In four dogs that underwent aortic banding no production of lactate or adenosine metabolites was observed at any heart rate; in these animals subendocardial flow was maintained at a level equal to or greater than subepicardial flow at all pacing rates. The remaining six dogs with LVH demonstrated net lactate production significantly greater than control during pacing at 250 beats/min; five of these six animals also produced adenosine metabolites.(ABSTRACT TRUNCATED AT 250 WORDS)

Adenosine↗
PubMed1982

Long-term intravenous infusion of antiarrhythmic drugs using a totally implanted drug delivery system.

In vitro and in vivo testing was performed to establish the feasibility of a totally implantable pump system to deliver antiarrhythmic agents. In vitro flow characteristics suggested predictable day to day delivery with acceptably small variations in flow with changes in reservoir volume or temperature. During 3 months of in vitro testing, procainamide and bretylium were found suitable for long-term delivery. Delivery of lidocaine was limited by high viscosity and corrosion of steel elements within the pump. The pump was implanted in a subcutaneous pocket in four dogs. Procainamide (0.5 g/ml), delivered at 4 ml/day (70 mg/kg body weight per day), provided a mean steady state drug concentration of 5.3 micrograms/ml. Bretylium (50 mg/ml), delivered at 8 ml/day (13 mg/kg per day), provided a steady state concentration of 0.8 micrograms/ml (range 0.4 to 1.4). Long-term intravenous administration of therapeutic doses of bretylium and procainamide with this delivery system has been demonstrated in dogs and appears to be feasible in human subjects.

Animals↗
PubMed1982

Symptomatic bradyarrhythmias in the adult: natural history following ventricular pacemaker implantation.

The preimplantation arrhythmias, coexistent medical conditions, the causes of death, and survival course are described for 399 patients who received their initial ventricular pacemaker implantation for a bradyarrhythmia (AV block, sinus node disease, and hypersensitive carotid sinus syndrome) at the University of Michigan from 1961 to 1979. Factors which correlated with a poor survival are elucidated. Survival for those with sinus node disease was virtually identical to those with AV block, with only 63% surviving over five years. Advanced age and congestive heart failure prior to implantation, and underlying ischemic or hypertensive heart disease portended a poorer survival in both groups. Patients with hypersensitive carotid sinus syndrome had a distinctly better prognosis--no deaths occurred until the eight year after pacing. Patients with no underlying heart disease and those with valvular disease did remarkably better than those with an ischemic or myopathic etiology. Apparent progression or complications of the underlying heart disease was the major cause of mortality. Sudden death, congestive heart failure, myocardial infarction, and major arrhythmias were the causes of death in 48% of those who died. Implications of improved pacing modalities on late complications and death are discussed.

Aged↗
PubMed1982

Ventricular pacing in children.

Ventricular pacing was performed in forty-one children ranging from one day to twenty years of age (median age = 10). Weight of the recipient at implant ranged from 2 kg. to 86 kg. Indications included presyncope, syncope, dyspnea on exertion, congestive heart failure, postoperative infra-Hisian heart block, and inadequate cardiac rate during pharmacotherapy. Four patients died during follow-up, but no deaths were attributable to pacemaker management. In contrast, 66% of the patients required more than one pacemaker related-operative procedure, and 43% of leads implanted failed by 48 hours. Indications for permanent cardiac pacing in this population at this time are symptomatic congenital AV block, symptomatic sinus node disease, and AV block in the postoperative period. Technological developments which might reduce complications seen in this population and electrophysiologic techniques which may better define indications for pacing in children are also reviewed.

Adolescent↗
PubMed1980

Suicide attempt by pacemaker system abuse: a case report with comments on the psychological adaptation of pacemaker patients.

Thirty patients selected at random from a pacemaker clinic were interviewed to gain an understanding of how psychological symptoms in these patients related to their cardiac condition. In 20% veiled depression or even a wish to die was elicited. Joking, fantasies, and denial were common psychological mechanisms used to adapt to their illness and the pacemaker itself. A dramatic example of attempted suicide in which the patient tried to cut the subcutaneously implanted pacemaker leads is presented and illustrated.

Adaptation, Psychological↗
PubMed1980

A comparison of sodium, chloride, thiocyanate, and sucrose spaces as estimates of extracellular fluid volume.

Sodium, chloride, thiocyanate, and sucrose spaces were measured in whole body and different tissues of rat. For each analytical method, when all tissue spaces were added the sum was in good agreement with corresponding total body fluid space obtained by dilution methods. There was surprisingly good agreement among the three ionic space measures in the total body, when one considers that there were discrepancies as large as 2- to 8-fold within certain of the different tissues. Some differences could be explained by the facts that sodium is a constituent of bond mineral and that there are marked differences between these four measures when observed in the water of the gastrointestinal contents.

Animals↗
PubMed1979

Symptomatic sinus node disease: natural history after permanent ventricular pacing.

Fifty-nine patients between the ages of 13 and 88 with sinus node disease, who received a permanent ventricular pacemaker between 1965 and 1976 at one institution, were followed to determine the natural history of the disorder after permanent pacing. Nineteen had ischemic heart disease, six had primary myocardial disease, and eight valvular heart disease. In 26, no etiology for the arrhythmia was apparent. The one- and five-year survival was 85.5% and 73.1%, respectively. Patients with underlying heart disease had a significantly poorer survival when compared to those without (58% versus 94% at 36 months) and all but 3 of 13 deaths in the first 36 months were in those with ischemic heart disease. There was a distinct trend toward poor survival in those with heart failure prior to pacemaker implant and those over age 65. Patients with sinus bradycardia alone did best (91% survival three years after implant), while those with bradycardia-tachycardia syndrome and those with sinoatrial arrest alone did distinctly worse (76% and 65% survival at three years, respectively). Twelve of 18 deaths were due to progression of underlying heart disease. The long-term prognosis with symptomatic sinus node disease can be predicted in part by (1) etiology of the underlying heart disease, (2) pre-implant arrhythmia, and (3) ventricular function prior to implant.

Adolescent↗
PubMed1978

Atrioventricular block: natural history after permanent ventricular pacing.

The preimplantation status, postimplantation morbidity and causes of late mortality were summarized for 246 patients who underwent pacing for atrioventricular (A-V) block at the University of Michigan for the 14 years from 1961 to 1974. The survival rate at 1, 5 and 10 years was 88, 61 and 49 percent, respectively. Risk of death was greatest among patients with antecedent ischemic or hypertensive heart disease or congestive heart failure in the period before pacemaker implantation, patients older than 74 years at initial implantation and those receiving a pacemaker before 1965. Forty-two percent of the 109 deaths were related to apparent progression of underlying cardiac disease. Pacing system malfunction was a contributing documented cause of only 3 deaths. Even with permanent pacemaker implantation, patients with A-V block have a higher age-specific mortality rate than the general U.S. population. Survival improved steadily over the period of study. This change is attributed to apparent improvements in treatment of cardiovascular disease including more effective treatment of congestive heart failure and valve replacement for selected patients as well as elimination of immediate postoperative mortality.

Aged↗
PubMed1976

Candida myocarditis without valvulitis.

Thirty-one patients with systemic candidiasis at postmortem examination were found to have Candida involvement of the myocardium without valvulitis. Retrospective examination of their clinical course demonstrated that a new conduction disturbance was seen in 10, supraventricular arrhythmias in 5,QRS changes mimicking myocardial infarction in 3, and pronounced T wave changes in 13. Hypotension or shock was seen in 13 patients and could not be explained by coexistent bacteremia or blood loss in 8. One patient died suddenly. Of 19 patients with systemic candidiasis without myocardial invasion, 4 had minor T wave changes and one had a supraventricular arrhythmia. Candida invasion of the heart significantly complicates the clinical course in systemic candidiasis and should be suspected when a young person without preexistent heart disease has cultures positive for a Candida organism, a significant arrhythmia, conduction distrubance or other dramatic QRS change. The effect of therapy on Candida invasion of the heart is unknown.

Adult↗
PubMed1976

Radiographic aspects of permanent cardiac pacemakers.

Radiographic findings in patients with permanent cardiac pacemakers are described, and recent advances in pulse generator and lead design are presented. Emphasis is placed on those findings which are related to (a) complications of cardiac pacing, (b) radiographic configurations of new energy sources and lead/electrode systems, and (c) a new system of pulse generator identification.

Bioelectric Energy Sources↗
PubMed1976

Coarctation of the aorta. Roentgenographic assessment after operative correction.

Persistent abnormalities in the cardiac silhouette and aortic arch are frequent in the late follow-up of patients operated upon for coarctation of the aorta. These abnormalities for the most part can be correlated with age at operation, the presence of a coexistent uncorrected congenital anomaly, or a persistent hemodynamic defect. This group of patients requires continuing clinical and roentgenologic assessment, as these abnormalities are frequently the hallmarks of additional significant cardiovascular disease despite correction of the primary congenital defect.

Adolescent↗
PubMed1975

Prodromata of myocardial infarction and sudden death.

A sample of 160 hospitalized, acute myocardial infarction patients and 138 individuals who died prior to hospitalization from acute coronary heart disease were studied to determine the incidence and duration of prodromal symptoms and action taken to cope with the symptoms. Seventy percent of the in-hospital subsample (IHS) and 64% of the out-hospital subsample (OHS) reported prodromata. The OHS reported a significantly longer median duration of symptoms than the IHS (29 versus 10.5 days). Sixty-seven percent of the IHS reported new or accelerated anginal symptoms as the most frequently occurring symptom, in contrast to 35% for the OHS. Twenty-seven percent of the IHS and 36% of the OHS consulted a physician about symptoms. Individuals in both subgroups, especially chronically diseased patients, considered their symptoms manageable. Likewise, when contacted, their physicians may have viewed these symptoms as manageable. Patients with a high risk of myocardial infarction and sudden death were significantly more likely to have consulted physicians during the prodromal phase than low-risk patients. A clearly delineated prodromal syndrome is needed so that both lay and medical communities can effectively respond to and intervene during the prodromal phase of acute myocardial infarction and sudden cardiac death.

Acute Disease↗
PubMed1975

The individual with a pacemaker in the dental environment.

A systematic examination of the potential hazards of electromagnetic interference with pacemakers in patients in the dental environment was carried out with the use of several pulse generators of three manufacturers. Only one model was affected by the dental operatory equipment tested. In two of three patients 2-second periods of asystole were noted: this was accompanied by symptoms in one. Permanent pacemakers implanted in three dogs were unaffected by short or sustained stimulation with pulp vitality testers. A permanent pacemaker implanted in one dog was unaffected by short or sustained stimulation with an ultrasonic cleaner. Reliance on severe symptoms alone is a poor method of assessing interference in the clinical situation. Guidelines for protection of the patient wearing a pacemaker in the dental environment are given.

Animals↗