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Biomedical subjects

D Tepper

Publications and source records attributed to D Tepper.

At least 19 recordsLinked to original sources
PubMed1992

Adenosine and its cardiovascular effects.

Adenosine is a new antiarrhythmic agent recently released with the permission of the Food and Drug Administration. It is an endogenously occurring nucleoside indicated for use in the diagnosis and treatment of supraventricular tachycardia. Its greatest utility is in patients with AV nodal reentry. Its antiarrhythmic action is mediated at the cellular level through the potassium channel, causing hyperpolarization of the myocyte membrane potential. In addition to its current indication as an antiarrhythmic agent, adenosine is now being used under an investigational protocol for pharmacologic stress testing. It can be given in conjunction with thallium or used in echocardiography as an imaging tool for patients who can not be adequately exercised. Adenosine's side effect profile is relatively benign and the agent's extremely short half-life makes most adverse reactions clinically insignificant. In this report we attempt to highlight this agent's clinical utility and discuss its future in the cardiovascular pharmacopeia.

Adenosine↗
PubMed1992

The radioprotective effects of WR-2721 on radiation-induced goblet cell loss.

We assessed the efficacy of the radioprotective effects of WR-2721 in radiation-induced goblet cell loss. Fourteen female New Zealand white rabbits were divided into radioprotected, radiounprotected, and control groups. Ten rabbits received 5,000 rad of beta irradiation to the temporal conjunctiva of both eyes. The right eyes were pretreated with topical applications of WR-2721 30 minutes and 1 minute before irradiation. The left eyes received irradiation only. Four additional rabbits received neither irradiation nor pretreatment with WR-2721. After a 2-month waiting period, each animal was killed and goblet cell densities per high-power field (GCD/HPF) were determined over the areas in question and compared using paired sample t tests. The mean GCD/HPF for the radioprotected, unprotected, and control groups were 10.93, 4.68, 23.15 (right eye), and 26.25 (left eye). Paired sample t tests showed a significant radioprotective effect when comparing WR-2721-treated animals with those receiving radiation only (p less than 0.003). Independent sample t tests showed significant goblet cell loss in both the radioprotected (p less than 0.018) and radiounprotected eyes (p less than 0) when compared with control groups. These data suggest a radioprotective effect of WR-2721 in radiation-induced goblet cell loss.

Amifostine↗
PubMed1991

Determinants of pace-terminable ventricular tachycardia: implications for implantable antitachycardia devices.

The next generation of implantable antitachycardia devices incorporate antitachycardia pacing for the treatment of ventricular tachycardia. To evaluate the potential determinants of pace terminability, we analyzed 62 episodes of induced monomorphic ventricular tachycardia. We found that the tachycardia cycle length and cycle length variability are the major determinants of pace terminability. These findings should be considered in the designing of ventricular tachycardia detection and termination algorithms.

Aged↗
PubMed1990

Prevalence, incidence and prognosis of recognized and unrecognized myocardial infarction in persons aged 75 years or older: The Bronx Aging Study.

The prevalence, incidence and prognosis of recognized and unrecognized Q-wave myocardial infarction (MI) was assessed in an 8-year prospective study of 390 community-based subjects (age 75 to 85 years at entry, mean 79 years). Subjects were studied at baseline and with annual follow-up electrocardiographic (ECG) exams. At baseline, 7.9% had a history of MI without ECG evidence, 6.4% had ECG evidence of Q-wave MI without clinical history, 4.1% had both clinical history and ECG evidence and 81.5% had neither history nor ECG evidence (control subjects). After an average follow-up period of 76.2 months, the total mortality rate was 5.9/100 person-years for subjects with some evidence of MI at baseline versus 3.9 in the control group (p = 0.059). The incidence of cardiovascular disease in subjects with evidence of MI was 8.8/100 person-years versus 4.7 among control subjects (p = 0.002). During the follow-up period, 115 new Q-wave MIs occurred (50 unrecognized, rate 2.4/100; 65 recognized, rate 3.2/100). There was no difference in mortality and morbidity outcome between subjects with recognized and unrecognized MIs. Those with only a history of MI at baseline had a threefold greater risk of a new MI (recognized and unrecognized) than the control group (p = 0.003). Unrecognized Q-wave MI is a common occurrence in the "old old" with subsequent morbidity and mortality prognosis comparable to that of recognized MI. History of MI alone in this age group is also associated with an increased risk of MI, suggesting the need for better diagnostic markers of myocardial ischemia in the old.

Aged↗
PubMed1990

Betaxolol: a new long-acting beta 1-selective adrenergic blocker.

Betaxolol (Searle, Skokie, Illinois) is a new beta 1-selective adrenergic blocker with no partial agonist action and minimal membrane stabilizing activity. Its pharmacokinetic profile is characterized by a long serum half-life and excellent oral bioavailability, with little first-pass metabolism. The mean 16-hour half-life of betaxolol has been shown to provide full 24-hour control of blood pressure and heart rate. Betaxolol has been proven to be a safe and effective antihypertensive agent, and was recently approved for clinical use in the United States for this indication.

Adult↗
PubMed1990

Driving safety after brain damage: follow-up of twenty-two patients with matched controls.

Driving after brain damage is a vital issue, considering the large number of patients who suffer from cerebrovascular and traumatic encephalopathy. The ability to operate a motor vehicle is an integral part of independence for most adults and so should be preserved whenever possible. The physician may estimate a patient's ability to drive safely based on his own examination, the evaluation of a neuropsychologist, and a comprehensive driving evaluation--testing, driving simulation, behind-the-wheel observation--with a driving specialist. This study sought to evaluate the ability of brain-damaged individuals to operate a motor vehicle safely at follow-up. These patients had been evaluated (by a physician, a neuropsychologist, and a driving specialist) and were judged able to operate a motor vehicle safely after their cognitive insult. Twenty-two brain-damaged patients who were evaluated at our institution were successfully followed up to five years (mean interval of 2.67 years). Patients were interviewed by telephone. Their driving safely was compared with a control group consisting of a close friend or spouse of each patient. Statistical analysis revealed no difference between patient and control groups in the type of driving, the incidence of speeding tickets, near accidents, and accidents, and the cost of vehicle damage when accidents occurred. The patient group was further divided into those who had, and those who had not experienced driving difficulties so that initial neuropsychologic testing could be compared. No significant differences were noted in any aspect of the neuropsychologic test battery. We conclude that selected brain-damaged patients who have passed a comprehensive driving assessment as outlined were as fit to drive as were their normal matched controls.(ABSTRACT TRUNCATED AT 250 WORDS)

Accidents, Traffic↗
PubMed1987

Evaluation of dosing interval and optimum dose of cibenzoline.

Fifteen patients with ventricular premature complexes (VPCs) were included in this open study designed to assess the relative efficacy of bid (two times daily) and tid (three times daily) dosing regimens for cibenzoline as compared with qid (four times daily) administration. Patients started therapy with qid administration; this was followed in sequence by tid and bid administration at the maximum effective total daily dose determined during the qid administration. Of the nine patients evaluated for efficacy for suppression of VPCs, eight demonstrated a 75% or greater suppression of VPCs with cibenzoline administered qid (total daily dose of 130-325 mg). This effectiveness was maintained in four patients with a bid regimen and in three with a tid regimen. All four patients who had ventricular tachycardia (VT) had a decrease in the number of VT episodes while receiving cibenzoline (only one of these patients had satisfactory suppression of VPCs at the same dosage regimen). Twelve patients continued to receive extended therapy with cibenzoline for up to two years, as this was considered to be the optimum antiarrhythmic treatment for these patients. Two patients had to be removed from the study and two had the dosage lowered because of adverse reactions (dry mouth, blurred vision, dizziness, congestive heart failure) although in one instance, the congestive heart failure was subsequently considered to be unrelated to cibenzoline. One patient was able to complete the short-term phase of the trial, but was not given extended treatment because of persistent dry mouth. Two patients had treatment discontinued during the extended therapy phase because of adverse reactions (fever, nausea, vomiting, asthenia).(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1987

Chronic flecainide therapy selected by electrophysiology testing of intravenous flecainide.

The utility of flecainide acetate was evaluated in 93 patients by means of electrophysiologic studies before and after intravenous flecainide administration to determine long-term efficacy. Twenty patients had a prior history of at least one cardiac arrest and 73 patients had sustained ventricular tachycardia (VT). The mean radionuclear ejection fraction was 32 +/- 5%. Flecainide was evaluated in 93 patients, with 44 patients no longer having VT following flecainide (47% efficacy). Procainamide was evaluated in 69 patients; 24 patients had an adverse reaction to reaction to procainamide and 28 of the 69 patients were protected on procainamide (40% efficacy). The mean serum concentration of flecainide achieved in the protected group was 298 +/- 36 ng/ml and 4.3 micrograms/ml for procainamide. Both flecainide and procainamide significantly prolonged refractoriness, lengthened QRS duration, while only procainamide increased the QT interval. All 93 patients were discharged on antiarrhythmic therapy, 42 on flecainide, 27 on other antiarrhythmic therapy guided by electrophysiologic testing, and 24 on amiodarone (when all other agents failed). Six of the 42 patients on flecainide complained of adverse side effects, but none were severe enough to warrant stopping therapy. Of the 42 patients on flecainide, four (9%) died suddenly over 18 +/- 4 months. Twenty-seven patients were on other therapy; eight of these have died, three suddenly (11%), four with myocardial infarctions, and one due to congestive heart failure. Twenty-four patients started amiodarone; 11 have died, five (21%) suddenly, four of congestive heart failure, one of pulmonary fibrosis, and one with myocardial infarction.(ABSTRACT TRUNCATED AT 250 WORDS)

Aged↗
PubMed1987

Use of the Israeli Standardized Denver Developmental Screening Test in the maternal and child health services--assessment of its predictive value.

The translated version of the Denver Developmental Screening Test (DDST) for screening a total population of infants at 6 months of age was used in the Maternal and Child Health Services of the Department of Social Medicine. The failure rate was 18%. In subsequent birth cohorts, the Israeli Standardized Denver Developmental Screening Test (IDDST) was applied, and the failure rate was 3%. The results of 176 infants tested with the IDDST were transcribed on the DDST forms. Sensitivity and predictive values were appraised in relation to the developmental quotient (DQ) at age 2 as assessed by the Brunet-Lezine Developmental Test. Using a cutoff point of 2 SD below the mean DQ as the criterion, sensitivity and predictive value were 25 and 13%, respectively. The sensitivity and predictive value of the IDDST increased when the cutoff point was changed to -1 SD. The biserial correlation coefficient between the DDST at 6 months of age and the DQ score at 2 years was 0.37 and that between the IDDST and the DQ was 0.28. The predictive value of infant tests and the need for reevaluation of the IDDST for 6-month-old infants is discussed.

Child Development↗
PubMed1986

Flecainide: a new antiarrhythmic agent.

PVCs (trigger mechanisms) and the vulnerability of the myocardium to sustain a life-threatening ventricular tachycardia (substrate) are two variables in the sudden death equation. Physicians treating patients at risk for sudden death should consider PVC frequency and vulnerability as interrelated variables. Risk assessment must take into consideration both variables. Antiarrhythmic drug efficacy can be assessed in terms of a reduction in trigger mechanisms (PVCs) as well as decreasing myocardial vulnerability (induction of VT at PES). Flecainide acetate, at a reduced dosage of 100 mg twice daily, is effective in both aspects, markedly decreasing PVC frequency and preventing VT induction at PES testing. Holter monitoring and electrophysiologic testing evaluate different aspects of the problem. With the addition of an agent as potent as flecainide, which is devoid of many of the bothersome side effects previously limiting antiarrhythmic therapy, an agent is now available that may be useful to treat both the trigger mechanism and the substrate in sudden death. We must be careful not to worsen the situation through the profound effects of flecainide on depolarization and refractoriness that in some patients cause life-threatening arrhythmias to be more frequent.

Animals↗
PubMed1986

QT prolongation and the antiarrhythmic efficacy of amiodarone.

Amiodarone is an antiarrhythmic agent known to cause prolongation of action potential duration which is reflected in the electrocardiogram as a prolongation of the QT interval. Prolongation of the QT interval in patients dying suddenly was compared with that in patients who remained alive to determine whether a difference existed between these two groups. The electrocardiogram and amiodarone levels were evaluated in 33 patients who presented with cardiac arrest and symptomatic ventricular tachycardia in whom no other antiarrhythmic agent was found effective in preventing induction of ventricular tachycardia during electrophysiologic studies. There were 30 men and 3 women (mean age 52 +/- 10 years). Twenty-three are alive after a mean follow-up period of 12 +/- 7 months. Ten died: six suddenly, three of non-cardiac causes and one of congestive heart failure. Using a two-way analysis of variance, the percent change in QT, QTc, JT and JTc intervals before and after amiodarone therapy was analyzed. Marked prolongation in the QT interval was present in patients who remained alive with amiodarone therapy. A significant difference in percent QT prolongation was seen between the latter patients and those who died suddenly (p less than 0.005). No difference was observed in the percent change in QRS interval between the two groups. The levels of amiodarone (2.5 versus 3.2 micrograms/ml) and its metabolite (desethylamiodarone) were not significantly different between the living patients and those who died suddenly. These findings suggest that a prolongation of the QT interval may be a marker for the therapeutic antiarrhythmic effect of amiodarone.

Aged↗
PubMed1986

Excitation-contraction coupling in rat myocardium: alterations with long term ethanol consumption.

The mechanical and electrical effects of chronic ethanol consumption were studied in rats maintained on 40% ethanol and water solution (40% of caloric intake) for a 30 week period and in controls. Left ventricular papillary muscles from male Wistar rats were studied by myography at 30 degrees C, 0.1 Hz stimulation, and external calcium concentration of 2.4 mmol X litre-1. No significant difference was found between alcoholic and control rats with regard to resting tension. Developed tension, time to peak tension, time to one half relaxation, and time to peak shortening were, however, significantly decreased in preparations from the study animals. Velocity of shortening and relengthening at all relative loads studied were depressed in alcoholic preparations. No significant difference was found in action potential between the two groups with regard to resting membrane potential, action potential amplitude, overshoot, or maximum rate of rise of the upstroke. In contrast, the duration at 50% (APD50) and 75% (APD75) of total repolarisation was significantly shorter for action potential in the alcoholic group than in the controls. Thus chronic ethanol ingestion results in an inability to develop normal levels of force, depressed force-velocity relation, and shortening of action potential duration.

Action Potentials↗
PubMed1986

Effects of hypothyroidism and hypoparathyroidism on rat myocardium: mechanical and electrical alterations.

The mechanical and electrical effects of hypoparathyroidism (Px), hypothyroidism (Tx), and hypothyroidism combined with hypoparathyroidism (TPx) were investigated by comparing simultaneously recorded transmembrane action potentials and isometric and isotonic contractions recorded from the myocardium. Left ventricular papillary muscles from male Wistar rats were studied electrically and mechanically in a muscle bath at 30 degree C, stimulated at 0.1 Hz and external calcium = 2.4 mM. No significant difference was found between control (C), Px, Tx, and TPx preparations with regard to resting tension and developed tension. However, time to peak tension, time to one half relaxation and time to peak shortening were significantly increased in preparations from animals that were Px, Tx, and TPx as compared with age-matched controls. Maximum velocities of shortening (Vs) and relengthening (Vr) at all relative loads studied were significantly depressed in Px preparations when compared with those of C muscles. A greater depression was found in the Tx muscle and still greater depression of these indices was noted in TPx muscles. No significant difference was found between C, Px, Tx, and TPx action potential with regard to resting membrane potential (RMP), action potential amplitude (AMP), overshoot (OS), or maximum rate of rise of the upstroke (Vmax).(ABSTRACT TRUNCATED AT 250 WORDS)

Action Potentials↗
PubMed1985

Prolonged repolarization: a historical perspective.

This symposium will more fully discuss QT prolongation--an area of controversy--prolonged QT syndromes, and new groups of agents that prolong repolarization and the QT interval (calcium blockers and antiarrhythmic agents). This is an important evolving field with old biases confronting a new and more thorough understanding of the phenomenon of prolonged repolarization.

Anti-Arrhythmia Agents↗