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At least 1,765 records · Page 98Linked to original sources
PubMed1995

Effects of class IA antiarrhythmic drugs on the reentrant circuit in common human atrial flutter.

In 9 patients with the common type of atrial flutter (AF), a zone of slow conduction was observed proximal to the coronary sinus orifice. Class IA antiarrhythmic drugs were administrated intravenously in all 9 patients. AF was converted to sinus rhythm in only 1 patient. In the remaining 8 patients, although IA drugs suppressed conduction velocity, this effect was not preferential with regard to the zone of slow conduction. Conversion of AF to sinus rhythm by rapid pacing was achieved in these 8 patients. At a critical pacing cycle length, AF was interrupted just after conduction block developed in the zone of slow conduction. A progressive decrease in conduction velocity was observed in the zone of slow conduction for several beats just before the onset of conduction block. In conclusion, class IA drugs facilitate the interruption of AF by rapid atrial pacing by inducing conduction block in the zone of slow conduction.

Adult↗
PubMed1988

Actions of a newly synthesized compound (711389-S) on various types of experimentally induced arrhythmias in mammalian species in situ.

We examined effects of 711389-S, a new antiarrhythmic agent, on ouabain-induced arrhythmias in dogs and guinea-pigs, aconitine-induced arrhythmias in dogs and mice, adrenaline-induced arrhythmias in dogs under an anesthetized condition, and arrhythmias induced by coronary artery ligation and occlusion by a glass bead in dogs under conscious and un-restrained conditions. 711389-S (1-3 mg/kg, i.v.) decreased the number of ventricular extrasystoles induced by ouabain in dogs, and the doses of ouabain required to induce various types of arrhythmias were increased by pretreatment of guinea-pigs with intraduodenal application of 711389-S (5-10 mg/kg). In mice, 711389-S (3 mg/kg, i.v. or 10 mg/kg, p.o.) significantly prolonged the time to onset of arrhythmias induced by aconitine infusion. Atrial fibrillation induced by a topical application of aconitine on the atrium was blocked by 711389-S (1 mg/kg, i.v.) in dogs. 711389-S (1-3 mg/kg, i.v.) depressed arrhythmias induced by adrenaline and restored the sinus rhythm by significantly decreasing the number of ventricular ectopic beats induced by coronary ligation or occlusion in dogs. Oral administration of 711389-S (10-30 mg/kg) in dogs markedly depressed the ventricular ectopic beats induced by coronary ligation. The half decay time of 711389-S after a single bolus injection of 711389-S ranged from 60 to 80 min. Results indicate that 711389-S has similar antiarrhythmic effects to those of other Class I antiarrhythmic agents in situ, and they suggest that this compound might have potential usefulness as a new type of antiarrhythmic agent for clinical use.

Aconitine↗
PubMed1996

Clinical characteristics and EPS-guided therapy in 142 cases of sustained ventricular tachycardia.

One hundred and forty-two consecutive patients with sustained monomorphic ventricular tachycardia (VT) were investigated. Only 26.1% of VTs were associated with ischemic heart disease (IHD). The induction rate of sustained VT upon electrophysiologic study (EPS) was 82.9% in patients with IHD and 65.3% in non-IHD. Of 76 inducible sustained VTs, pharmacologic therapy was finally selected in 35 cases, ablative therapy in 25 and surgical therapy in 12. Long-term prognosis was compared between groups divided according to type of ventricular arrhythmia induced at final EPS after antiarrhythmic therapy as follows: Group A: complete suppression of VT, Group B: clinical or non-clinical nonsustained VT, Group C: clinical sustained VT. The event rate in IHD was 6.3% in Group A, 44.4% in Group B and 100% in Group C. In non-IHD, the event rate was 24.0%, 25.0% and 75.0% (Groups A, B and C, respectively). Complete suppression of VT showed a good prognosis in IHD, however, a slightly higher recurrence rate was observed in non-IHD. In ablative therapy, some recurrences and sudden deaths were observed in spite of complete suppression of both VTs in both the IHD and non-IHD groups. Review of the efficacy of antiarrhythmic procedures is recommended during the follow-up period.

Aged↗
PubMed1998

Reentrant ventricular tachycardia. Interpretations of electrophysiologic findings and its applications.

Monomorphic sustained ventricular tachycardia (MSVT) was revisited in relation to the electrophysiologic findings and their relation to the drug efficacy. Old myocardial infarction is less common cause of MSVT in Japan, and the majority (about 2/3) of MSVT is unrelated to coronary artery disease but, the mechanism shared a common mechanism: reentry with an excitable gap as others. The reentrant mechanism was supported from the inducibility, the terminability of VT by electrical stimulation, and by the ability to entrain with rapid pacing. In MSVT associated with underlying heart diseases, diseased myocardium showed low amplitude and fragmented electrograms and the area was considered to participate as the central common pathway of reentrant circuit. The area of slow pathway showed a decremental conduction or all-or-nothing conductive property. The width of the excitable gap seemed to be determined by the maximal conductive frequency but not by the duration of action potential: effective refractory period. As to the drug efficacy, there was no baseline characteristics in predicting the efficacy. However, the significant narrowing of the width of the excitable gap was associated with the drug efficacy and VT became non-inducible after addition of the same drug. The response pattern of the excitable gap to specific drug including class III, was not predictable. Further electropharmacological studies will be warranted.

Anti-Arrhythmia Agents↗
PubMed1990

Clinical features of sustained ventricular tachycardia among various underlying heart diseases.

Clinical findings of 52 patients with sustained ventricular tachycardia (VT) were analyzed to assess the importance of the underlying etiology. Among patients with organic heart diseases, no differences were found in the VT rate, the incidence of syncope, and the number of patients who required DC shock, regardless of the difference of the underlying organic heart diseases. Patients without organic heart disease had usually more benign clinical presentations. The electrophysiologic findings of VT such as inducibility, a mode of induction and incidence of pleomorphism were similar in patients who had organic heart disease of various causes. Neither the incidence of pleomorphism nor occurrence of acceleration of VT rate was found in patients with idiopathic VT, and the incidence of VT induction was low in patients with idiopathic VT of RV origin. Patients with organic heart diseases often died suddenly, and patients when their VT rate was 200/min or higher, developed syncope, even who had normal LV function.

Adult↗
PubMed2002

Strategy for the management of vasovagal syncope.

The disorders of autonomic control associated with orthostatic intolerance are a diverse group of syndromes that can result in syncope and near-syncope. A basic understanding of the pathophysiology of these disorders is essential to diagnosis and proper treatment. It is especially important to recognise the difference between the effect of prolonged upright posture on a failing autonomic nervous system (a hyposensitive or dysautonomic response) and the vasovagal response (which may be a hypersensitive response). Vasovagal syncope is the most common abnormal response to upright posture and occurs in all age groups. The advent of tilt table testing has helped define a population with an objective finding during provocative testing that has enabled researchers to study the mechanism of vasovagal syncope and to evaluate the efficacy of treatments. In most patients, vasovagal syncope occurs infrequently and only under exceptional circumstances and treatment is not needed. Treatment may be indicated in patients with recurrent syncope or with syncope that has been associated with physical injury or potential occupational hazard. Based on study data, patients with vasovagal syncope can now be risk stratified into a high-risk group likely to have recurrent syncope and a low-risk group. Many patients with vasovagal syncope can be effectively treated with education, reassurance and a simple increase in dietary salt and fluid intake. In others, treatment involves removal or avoidance of agents that predispose to hypotension or dehydration. However, when these measures fail to prevent the recurrence of symptoms, pharmacological therapy is usually recommended. Although many pharmacological agents have been proposed and/or demonstrated to be effective based on nonrandomised clinical trials, there is a remarkable absence of data from large prospective clinical trials. Data from randomised placebo-controlled studies support the efficacy of beta-blockers, midodrine, serotonin reuptake inhibitors and ACE inhibitors. There is also considerable clinical experience and a consensus suggesting that fludrocortisone is effective. Encouraging new data suggest that a programme involving tilt training can effectively prevent vasovagal syncope. For patients with recurrent vasovagal syncope that is refractory to these treatments, implantation of a permanent pacemaker with specialised sensing/pacing algorithms appears to be effective. A number of larger clinical trials are underway which should help further define the efficacy of a number of different treatments for vasovagal syncope.

Adrenergic alpha-Agonists↗
PubMed1984

Potential applications of free drug level monitoring in cardiovascular therapy.

Cardiovascular drugs, as a class, have low therapeutic indices, but also have great therapeutic potential. Plasma concentration information is therefore often of value when using these drugs. Unfortunately, the total plasma concentration may not reflect the concentration of pharmacologically active free drug, since a number of factors including disease states, heparin anticoagulation, non-linear binding characteristics, and in vitro artefacts can affect the protein binding of these agents. This may also explain their poor dose-response relationships and great interindividual variability in plasma concentration data. Careful studies relating bound and free drug concentration to pharmacological response may provide the clinician with a better guide to therapy, and enhance the usefulness of these drugs.

Anti-Arrhythmia Agents↗
PubMed1997

Bioequivalence of chiral drugs. Stereospecific versus non-stereospecific methods.

Guidelines for bioequivalence of non-racemic pharmaceuticals are abundant in the literature. However, few guidelines exist for the bioequivalence of racemic drugs which consist of 2 or more stereoisomers. The aim of this article is to address the question of whether the bioequivalence of racemic drugs should be based on the measurement of the individual enantiomers or that of the total drug. Several pharmacokinetic-pharmacodynamic cases are examined to test the validity of extrapolating the bioequivalence of racemic drugs to that of their individual enantiomers after administration of the racemate; simulation and experimental data are presented to support these cases. It is shown that for drugs which exhibit non-linear pharmacokinetics, the results of bioequivalence studies based on the total drug may differ from those based on the individual enantiomers. Similar discrepancies can be shown for a racemic drug with linear pharmacokinetics whose enantiomers substantially differ from each other in their pharmacokinetic parameters. Therefore, it is suggested that stereospecific assays be used for these drugs. Additionally, it is recommended that for racemic drugs which undergo chiral inversion, and for most products with modified release characteristics, the bioequivalence be assessed using stereospecific assays. Conversely, for racemic drugs with linear pharmacokinetics and minimal to modest stereoselectivity in their kinetic parameters, and for those with non-stereoselective pharmacodynamics, the use of stereospecific analytical methods are not warranted. Finally, the limited, controversial literature in favour of or against the use of stereospecific assays in bioequivalence of chiral drugs are reviewed and a preliminary guideline is proposed.

Adrenergic Uptake Inhibitors↗
PubMed1985

Aggravation of ventricular arrhythmia. A drug-induced complication.

Each antiarrhythmic agent can cause side effects, but most of these are easily recognised by the patient or physician. However, one potentially serious side effect common to all of these drugs is aggravation of ventricular arrhythmia. Often this is without symptoms and goes unrecognised by the patient. It occurs in 11 to 16% of drug tests depending upon the method of drug evaluation employed. There are no ECG changes which predict its occurrence and blood concentrations of drug are usually within a therapeutic range. There are no clinical patient features which are associated with this toxic reaction and it does not correlate with the presence or extent of underlying heart disease, the nature of the presenting arrhythmia or the known electrophysiological properties of the antiarrhythmic drug. Careful evaluation of these drugs is therefore essential.

Anilides↗
PubMed1980

Acute intoxication with diisopyramide: clinical and experimental study by hemoperfusion an Amberlite XAD 4 resin.

Diisopyramide overdose induces an early and severe cardiogenic shock; hemoperfusion on resin (Amberlite XAD 4) is the most efficient treatment. In vitro, 92% of the drug is adsorbed in 240 min. In dog, the plasmatic epuration is 66% with a mean plasma clearance of 74% plasmatic flow. A woman who had absorbed 4.50 g diisopyramide showed an idioventricular rhythm. The cardiac electrical stimulation and positive inotrope drugs were inefficient. Hemoperfusion on resin Amberlite XAD 4 corrected hemodynamic and ECG disturbances in 4 h. The epuration was proved by the decrease of diisopyramide plasma level: 24.4 micrograms/mL before epuration, 1.9 micrograms/mL after epuration, and a mean plasma clearance of 107.8 mL/min (61% of the plasmatic flow). Hemoperfusion of resin (Amberlite XAD 4) is more efficient than hemodialysis (cuprophan) and hemofiltration (polyacrylonitrile). The system that we have used is well tolerated and of low cost.

Animals↗