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Biomedical subjects

D Flowers

Publications and source records attributed to D Flowers.

35 records · Page 2Linked to original sources
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↗
PubMed1985

Electrophysiologic evaluation of the antiarrhythmic effects of N-acetylprocainamide for ventricular tachycardia secondary to coronary artery disease.

Antiarrhythmic properties of N-acetylprocainamide (NAPA), an active metabolite of procainamide, were studied in 12 patients with coronary artery disease who presented with cardiac arrest or documented sustained ventricular tachycardia (VT). Programmed electrical stimulation (PES) studies were performed in 10 men and 2 women, aged 52 to 80 years (mean 63), who had a left ventricular ejection fraction of 16 to 69% (mean 33). All patients tested had inducible VT provoked by PES without antiarrhythmic therapy. Patients were then tested with procainamide, 1,000 mg administered intravenously. VT could be provoked after procainamide treatment in 8 of 10 patients. Twenty-four to 36 hours later NAPA was administered, 18 mg/kg body weight intravenously, and PES was performed after 20 minutes. NAPA did not significantly change heart rate, mean arterial blood pressure, electrocardiographic intervals and AH or HV conduction times. The QT interval lengthened, but not significantly. The mean serum NAPA levels were 15.7 +/- 4 micrograms/ml in the group protected by NAPA and 16.2 +/- 4 micrograms/ml in the group not protected by NAPA. Five patients were discharged with NAPA therapy, 1.5 g orally every 8 hours. Two patients have been maintained with chronic NAPA therapy (10 +/- 3 months), and 2 patients had breakthrough VT on follow-up Holter monitoring and alternative therapy was given. One patient died while taking oral therapy. NAPA demonstrates antiarrhythmic efficacy in preventing induction of VT by PES in a high-risk group of patients. During chronic oral therapy in some patients, NAPA appears to be well tolerated, with antiarrhythmic efficacy that may be enhanced with further upward dose titration.

Acecainide↗
PubMed1985

Flecainide: long-term treatment using a reduced dosing schedule.

Flecainide was initially prescribed at a dose of 200 mg twice daily, but after early toxicity in patients with ventricular tachycardia (VT), the dosage was reduced to 100 mg twice daily. The effects of flecainide were studied in 40 patients (29 men and 11 women, mean age 62 +/- 2 years, ejection fraction 45 +/- 3%) who underwent programmed electrical stimulation to determine the efficacy of flecainide in preventing VT chronically at the reduced dose. Sustained VT was induced in 21 patients and nonsustained VT in 19. Flecainide prevented VT induction in 26 patients (65%). At a mean dose of 1.5 +/- 0.1 mg/kg, prolongation occurred in the effective refractory period of the first (280 +/- 5 vs 249 +/- 5 ms) and second (254 +/- 6 vs 209 +/- 9 ms) extrastimuli (p less than 0.01). In the patients protected by flecainide, the effective refractory periods increased by a 17 +/- 2% and 21 +/- 3%, in contrast to only a 7 +/- 3% and 6 +/- 4% increase in the nonprotected group (p less than 0.05), despite a higher mean dose (1.9 +/- 0.1 vs 1.35 +/- 0.1 mg/kg). Twenty-one patients were discharged on flecainide therapy, 100 mg twice daily, and were followed for a mean of 11 months. Sixteen patients are alive and well, 1 died suddenly, 1 died from a noncardiac cause and 1 had a "breakthrough" arrhythmia. Two were switched to quinidine therapy by their referring physicians, but were without problems while receiving flecainide.(ABSTRACT TRUNCATED AT 250 WORDS)

Anti-Arrhythmia Agents↗
PubMed1985

How useful are serum and CSF interferon levels as a rapid diagnostic aid in virus infections?

Specimens from a total of 162 patients were studied prospectively using a rapid nucleic acid synthesis inhibition assay and a plaque-reduction assay to detect interferon levels in serum and cerebrospinal fluid. The specificity, consistency, and diagnostic applications of the rapid assay were evaluated by intensively investigating each patient for possible viral illness. Forty-one percent of patients with proven acute virus infections (excluding those with acute hepatitis and infectious mononucleosis) had unequivocal detectable interferon in serum or cerebrospinal fluid, compared with only two patients with bacterial infections (7%) who had equivocal interferon in the serum. Retrospective analysis showed the test to have high specificity for virus infections, but in patients with clinical syndromes of uncertain aetiology the test was not a particularly sensitive indicator of the presence of subsequently detected virus. The presence of interferon was not related to the time during the illness at which the sample was taken, nor to the numbers of lymphocytes in the cerebrospinal fluid, nor to the patients' general symptoms.

Biological Assay↗
PubMed1985

Prolongation of QT interval and antiarrhythmic action of bepridil.

Studies were undertaken with bepridil, a new calcium blocker that prolongs the QT interval, to determine the antiarrhythmic and possible arrhythmogenic properties of this agent. The technique of programmed electrical stimulation was employed to evaluate bepridil in 15 patients with symptomatic ventricular tachycardia (VT). Bepridil prevented VT induction in 7 of 15 patients. Bepridil prolonged the QT and refractoriness and a linear correlation could be demonstrated between the percent change in QTc and refractory period prolongation for the bepridil-protected group. Bepridil in one patient reduced by one the number of stimuli required to induce VT, but no spontaneous arrhythmias were noted. Bepridil thus possesses antiarrhythmic properties with a minimal proarrhythmic effect.

Aged↗
PubMed1985

Long-term lorcainide therapy in patients with ventricular tachycardia.

One hundred patients inducible at electrophysiologic studies underwent serial drug testing with procainamide, lidocaine, and lorcainide to determine comparative efficacy. Acute intravenous administration was followed by repeat programmed electrical stimulation (PES) studies on separate days for each antiarrhythmic drug. Lorcainide prevented ventricular tachycardia (VT) induction in 69% of the 100 patients studied, procainamide was effective in 50% of the 75 patients studied, and lidocaine prevented VT induction in 30% of 53 patients. Following PES and serial drug testing, 46 patients were started on lorcainide, nine patients on procainamide, and 45 patients were started on other antiarrhythmic drug regimens. Seventy percent of the patients have remained on lorcainide therapy, while 47% have continued on other drug therapies started over a 20.5 +/- 3.2-month mean follow-up period. Despite sleep-wake disturbances and a need for sedation at night, lorcainide therapy was tolerated well in this population and remained an effective antiarrhythmic with prolonged administration.

Benzeneacetamides↗
PubMed1985

The clinical significance of polymorphic ventricular tachycardia provoked at electrophysiologic testing.

Ventricular tachycardia (VT) induced at electrophysiologic studies is felt to be clinically significant if the morphology of the induced arrhythmia and the spontaneous arrhythmia are similar. Yet many times in referral patients, an adequate 12-lead ECG does not exist to permit determination of the VT morphology. Since the significance of differences in induced and spontaneous arrhythmias has not been clearly established, we reviewed the records of 153 patients and correlated induced VT morphology with the incidence of sudden death. Polymorphic VT was induced in 88 patients (57%) and monomorphic VT was induced in 65 patients (43%). The total mortality and sudden death rates were similar in the two groups in spite of antiarrhythmic therapy, 12% and 7% (polymorphic) versus 10% and 5% (monomorphic). All the sudden deaths occurred in patients who presented with cardiac arrest and hemodynamically symptomatic VT and none in the asymptomatic VT group, regardless of VT morphology (p less than 0.005). The induced VT morphology cannot be used to predict the potential efficacy of antiarrhythmic drugs, since patients with either morphology are as likely to respond to conventional or experimental agents. Thus, induced polymorphic VT can be a useful index of electrical instability in high-risk patients (cardiac arrest and hemodynamically symptomatic VT) and may be of utility in guiding antiarrhythmic therapy.

Aged↗
PubMed1985

Long term lorcainide therapy guided by electrophysiology studies.

One hundred patients inducible at electrophysiologic studies underwent serial drug testing with procainamide, lidocaine and lorcainide to determine comparative efficacy. Acute intravenous administration was followed by repeat programmed electrical stimulation (PES) studies on separate days for each antiarrhythmic drug. Lorcainide prevented VT induction in 69% of the 100 patients studied, procainamide was effective in 50% of the 75 patients studied, and lidocaine prevented VT induction in 30% of 53 patients. Following PES and serial drug testing, 46 patients were started on lorcainide, 9 patients on procainamide, and 45 patients were started on other antiarrhythmic drug regimens. Seventy percent of the patients have remained on lorcainide therapy, while 47% have continued on other drug therapies started over a 20.5 +/- 3.2 month mean follow-up period. Despite sleep-wake disturbances and a need for sedation at night, lorcainide therapy was tolerated well in this population and remained an effective antiarrhythmic with prolonged administration.

Administration, Oral↗
PubMed1984

Lorcainide therapy for the high-risk patient post myocardial infarction.

Nonsustained ventricular tachycardia (VT) in the late period (7 to 21 days) after myocardial infarction (MI) is reported to be a predictor of sudden death. Patients with 3-beat VT on Holter monitoring in the late infarction period would be suspected to demonstrate electrical instability on electrophysiologic studies. Forty-seven patients were identified as having at least 3-beat VT on Holter monitoring. Eighteen patients refused electrophysiologic studies or were not referred. Eight patients died; 3 were sudden deaths in 13 +/- 5 months, a 17% incidence. Twenty-nine patients underwent invasive electrophysiologic studies and 28 had inducible VT, 18 sustained and 10 nonsustained. Lorcainide prevented VT induction in 21 of the 28 patients, whereas 12 of the 22 patients studied on procainamide were protected. Lidocaine, tested in 21 patients, prevented VT induction in only 5. Lorcainide and procainamide prolonged refractoriness in those patients protected at programmed electrical stimulation (PES), whereas the QT interval was prolonged in patients in whom VT could still be induced. Twenty-seven of the 28 patients were placed on drugs predicted to be effective by PES studies, 19 on lorcainide. After a mean follow-up of 12.5 +/- 4 months the patient with noninducible arrhythmia is alive and 26 of the 28 patients with inducible arrhythmia are alive and well. Two patients died, 1 of stroke and 1 of pump failure after a second MI. No sudden deaths were observed in this group. Two patients had breakthrough arrhythmias and were treated by alternative antiarrhythmic therapy that was also effective on initial electrophysiologic studies.(ABSTRACT TRUNCATED AT 250 WORDS)

Aged↗
PubMed1984

Evaluation of lorcainide in patients with symptomatic ventricular tachycardia.

One hundred patients with inducible ventricular tachycardia (VT) on electrophysiologic studies underwent serial drug testing with procainamide, lidocaine and lorcainide to determine comparative efficacy. Acute intravenous administration was followed by repeat programmed electrical stimulation (PES) studies on separate days for each antiarrhythmic agent. Lorcainide prevented VT induction in 69% of the 100 patients studied, procainamide in 50% of the 75 patients studied and lidocaine in 30% of 53 patients. After PES and serial drug testing, 46 patients were started on lorcainide, 9 on procainamide and 45 on other antiarrhythmic drug regimens. Eighty percent of the patients have remained on lorcainide therapy, whereas 47% have continued on other drug therapies started over 17.5-month mean follow-up period. Despite sleep-wake disturbances and a need for sedation at night, lorcainide therapy was well tolerated in this population and remained an effective antiarrhythmic agent with prolonged administration.

Anti-Arrhythmia Agents↗
PubMed1984

Comparison of noninvasive arrhythmia induction techniques with electrophysiologic studies and evaluation of lorcainide in patients with symptomatic ventricular tachycardia.

Twenty-six patients (19 men and 7 women) with symptomatic ventricular tachycardia (VT) were studied using invasive and noninvasive techniques to induce VT. Of the study population, 12% had syncope and VT on Holter monitoring, 30% had cardiac arrest and 58% had symptomatic VT. All patients had antiarrhythmic agents stopped 5 half-lives before evaluation and then had autonomic profile (upright tilt, cold pressor test, exercise testing and hand grip) as well as programmed electrical stimulation studies performed. Autonomic profile testing induced VT in 5 of 26 patients (19%) and in only 1 patient was the arrhythmia reproducibly induced. All 26 patients had VT induced on electrophysiologic testing; 9 patients had nonsustained and 17 had sustained VT. Lorcainide administered intravenously prevented VT induction in 20 of 26 patients tested, whereas procainamide was effective in 11 of 24 patients. Ten of the 13 not protected by procainamide were protected by lorcainide. Twenty patients were started on long-term lorcainide therapy and followed up for 29 +/- 3.4 months. Five patients have discontinued therapy, 2 because of breakthrough arrhythmias, 2 because of severe sleep-wake disturbances and 1 because of private physician preference. An additional 3 patients died during therapy because of myocardial infarction in 1, progressive myopathy in 1 and sudden death in 1. Sixty percent of patients started on lorcainide therapy have continued. In this patient population, noninvasive induction of VT is not a sensitive or reproducible technique in assessing antiarrhythmic therapy. Furthermore, when selected on the basis of electrophysiologic testing, lorcainide is a well-tolerated and effective antiarrhythmic agent.

Aged↗
PubMed1984

Antiarrhythmic action of bethanidine.

Studies were performed in 20 patients with symptomatic ventricular tachycardia (VT) to determine the efficacy of bethanidine compared with procainamide in preventing VT induced by programmed electrical stimulation. Before administering bethanidine, 5 to 10 mg/kg, the patients received 15 mg of protriptyline orally 24 and 2 hours before electrophysiologic studies to prevent the orthostatic hypotensive effects of bethanidine. Sustained VT (VT not spontaneously stopping) was induced in 8 and nonsustained VT (10 beats or more, terminating spontaneously) was induced in 4 patients. Bethanidine, 5 mg/kg, protected in 7 patients, and 10 mg/kg protected 1 additional patient. Procainamide, 1,000 and 1,500 mg intravenously, protected 8 of 16 patients. Bethanidine prevented VT induction in 50% of the patients not protected by procainamide. Bethanidine facilitated VT induction in 3 patients, while procainamide facilitated VT induction in 1 patient. Four patients with symptomatic VT have received bethanidine therapy for an average of 11 +/- 1.3 months, without clinical recurrence of their VT. Concomitant administration of protriptyline attenuated the acute hemodynamic changes caused by bethanidine and chronic combined therapy of protriptyline and bethanidine abolished the severe orthostatic changes in blood pressure caused by bethanidine. These studies show that bethanidine is effective in preventing VT induction and, thus, its use may not be restricted only to cases of primary ventricular fibrillation.

Bethanidine↗
PubMed1984

Intravenous quinidine by intermittent bolus for electrophysiologic studies in patients with ventricular tachycardia.

The safety and efficacy of intravenous quinidine gluconate, using intermittent boluses of 80 mg/cc every 5 minutes to a total dose of 800 mg, was evaluated in 61 patients referred for electrophysiologic studies (EPS). Patients were referred because of out-of-hospital cardiac arrest (12), symptomatic ventricular tachycardia (VT) (24), asymptomatic VT (18), syncope of unknown origin (6), and supraventricular arrhythmias (1). Clinical heart failure was present in 74% of patients, with a mean ejection fraction of 45 +/- 3 for all patients. Quinidine prevented VT induction in 78% of patients at a mean dose of 9.6 mg/kg and facilitated VT induction in 7% of patients. Quinidine failed to decrease mean arterial pressure in 14 patients, and in the remaining 47 patients arterial pressure decreased by 16%. Six patients had hemodynamically significant hypotension. Two patients had hypotension severe enough to require saline administration, while four had hypotension not needing fluid replacement. Sixteen percent of patients experienced other side effects. Quinidine can be administered safely by intermittent infusion and is effective in preventing programmed stimulation induction of VT. Carefully monitored, intravenous intermittent bolus administration of quinidine should be utilized more frequently in EPS, since significant adverse side effects are infrequent.

Adult↗
PubMed1983

Diagnosis of human coronavirus infections in children using enzyme-linked immunosorbent assay.

An enzyme-linked immunosorbent assay (ELISA) was developed for diagnosing human coronavirus (HCV) infections in children. One hundred and seventy seven nose swabs, throat swabs, and nasopharyngeal aspirates were collected from 30 children suffering from acute respiratory infections. These samples were tested for HCV antigens by ELISA and 28.2% of the samples were shown to be HCV positive. These results indicate that our ELISA should prove useful in the diagnosis of HCV infections in children. Further studies are in progress to extend the ELISA to detect HCVs in experimentally and naturally acquired infections in adults.

Antigens, Viral↗
PubMed1983

Epidemiology of coronavirus respiratory infections.

Human coronaviruses were found by enzyme linked immunosorbent assay in upper respiratory tract secretions taken during 30% of 108 acute respiratory infections experienced by 30 children under age 6 years with recurrent respiratory infections (index group), and during 29% of 51 acute infections experienced by their siblings. Lower respiratory tract infection--predominantly wheezy bronchitis--occurred in 30% of the index children's coronavirus positive infections but in none of their siblings' infections. Reinfections were common. Two peaks of infection were seen each year in the late autumn/early winter and in the early summer.

Acute Disease↗
PubMed1981

Toxicity of interferon.

The effects of partially purified human leucocyte interferon (PIF) and of a preparation purified by passage twice through a monoclonal antibody affinity chromatography column (NK21F) were compared with those of a control solution in healhty volunteers. After intramuscular injections both interferon preparations caused rises in pulse rate and body temperature, changes in circulating white cell counts, and various unpleasant symptoms, the most common of which were headache, malaise, and fever. Slightly lower doses of NK21F were given, and this was reflected in lower peak serum concentrations. Mean symptom scores, however, were not lower after NK21F than after PIF. Local inflammatory reactions eight hours after intradermal inoculations of these interferons were similar. Purification of interferon using a monoclonal antibody does not reduce the facets of its activity considered in this study. They are therefore inherent in the leucocyte interferon type selected by the antibody.

Adult↗