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Biomedical subjects

H Garan

Publications and source records attributed to H Garan.

At least 109 records · Page 6Linked to original sources
PubMed1984

Serious adverse effects of amiodarone.

Amiodarone is an effective antiarrhythmic drug which has been used successfully to treat a variety of cardiac arrhythmias. Early reports emphasized both the striking efficacy of this agent and the relative paucity of side effects necessitating discontinuing treatment with this drug. As amiodarone has been used more widely and in more diverse patient populations, reports of serious thyroid, pulmonary, cardiovascular, and other adverse reactions have appeared in the literature. In this paper, we review the serious adverse effects that have been reported to date. The incidence of these reactions varies considerably in different series, and cannot be explained solely by different doses employed or by varying methods of drug administration. The final role of amiodarone in the therapy of cardiac arrhythmias cannot be determined until the long-term toxicity has been more thoroughly investigated.

Amiodarone↗
PubMed1984

Oral mexiletine in the treatment of refractory ventricular arrhythmias: the role of electrophysiologic techniques.

Mexiletine is a useful antiarrhythmic agent for the treatment of ventricular arrhythmias. Its efficacy in suppressing ventricular arrhythmias during serial electrophysiologic evaluation has come under investigation only recently. Experience to date in more than 300 patients suggests that suppression of inducible ventricular arrhythmias by mexiletine either alone or in combination with another antiarrhythmic agent may be achieved in approximately 30% of patients. Furthermore, suppression sometimes may be achieved when mexiletine is tested in combination with a type IA antiarrhythmic or beta-adrenergic blocking agent in patients for whom neither agent alone has been effective. The likelihood of suppressing inducible ventricular tachycardia (VT) with mexiletine therapy alone or in combination may vary as a function of the spontaneous ventricular arrhythmia with which a patient presents at the time of electrophysiologic study; patients presenting with sustained VT appear to have inducible arrhythmias that are more difficult to suppress. A significant incidence of adverse effects attributable to mexiletine has been observed, particularly gastrointestinal and neurologic effects. These side effects, although common, are frequently eliminated by reducing the dosage of the drug and administering the drug with food. A facilitation of arrhythmia induction has also been observed in a small percentage of patients. Early experience suggests that selected patients with ventricular arrhythmias that are refractory to conventional antiarrhythmic agents may derive long-term benefit from chronic therapy with oral mexiletine.

Administration, Oral↗
PubMed1984

Localized reentry. Mechanism of induced sustained ventricular tachycardia in canine model of recent myocardial infarction.

This study was undertaken to investigate the mechanism underlying sustained monomorphic ventricular tachycardia (VT) in late experimental canine myocardial infarction. The hypothesis that sustained and "organized" continuous electrical activity (CEA) displaying a reproducible pattern with recurrent components recorded by bipolar endocardial, intramural, or epicardial electrodes in 10 animals during electrically induced sustained monomorphic VT represented reentrant excitation in an anatomically small area of the ventricle, was evaluated in the light of the following observations: Organized CEA always preceded the first monomorphic ventricular complex (QRS) of VT as well as the discrete local electrograms from closely surrounding sites during the initiation of VT. The site of organized CEA corresponded to the site of origin of sustained VT determined by iso-chronous contour map analysis of activation sequence. Ventricular pacing at rates more rapid than that of VT failed to terminate VT despite ventricular capture unless it transformed CEA into discrete local electrograms. VT could be terminated in three animals, with a single, critically timed premature stimulus delivered at a critically located focus close to the site of CEA, which would result in local capture and interrupted CEA. In six animals, surgical ablation of the site of organized CEA effectively prevented the reinitiation of sustained VT by programmed cardiac stimulation. These data showed that organized CEA and sustained VT were closely associated phenomena and suggested that organized CEA probably represented an important component of the tachycardia circuit.

Animals↗
PubMed1983

Role of electrophysiologic techniques in the selection of antiarrhythmic drug regimens for ventricular arrhythmias.

Programmed electrical stimulation of the heart provides a useful new technique for guiding the selection of antiarrhythmic drug regimens in selected patients with ventricular tachycardia (VT) or ventricular fibrillation. The technique of programmed electrical stimulation has been applied successfully in patients with recurrent sustained VT, out-of-hospital ventricular fibrillation and unexplained syncope in the presence of structural heart disease. The complete suppression of VT induced by programmed electrical stimulation by a drug regimen is highly predictive of freedom from both recurrent VT and sudden death. In addition, this technique may hold promise as a means of assessing the arrhythmogenic effects of antiarrhythmic drugs in selected patients.

Anti-Arrhythmia Agents↗
PubMed1983

Adverse reactions during treatment with amiodarone hydrochloride.

Amiodarone was administered to 80 patients with recurrent cardiac tachyarrhythmias previously resistant to drug treatment. Forty nine patients were treated for ventricular tachycardia or fibrillation and 31 for supra-ventricular arrhythmias. The mean (range six days to 51 months), permitting a total of 100 patient years of observation. Adverse reactions were observed in 69 patients. Severe side effects were encountered in 13: four patients developed interstitial pneumonitis, four patients developed incessant ventricular tachycardia, three patients taking amiodarone and digoxin sustained sinus node arrest with depression of escape foci, one patient developed hepatitis, and one patient developed hypercalcaemia with renal failure. Furthermore, a rise in the serum concentration of digoxin and potentiation of warfarin anticoagulation occurred in cases in which these agents were combined with amiodarone. Amiodarone was stopped in 14 patients because of side effects. Although amiodarone is effective in suppressing arrhythmias in most patients in whom extensive use of antiarrhythmic drugs has been unsuccessful, it is associated with diverse and serious toxicity. These observations suggest that at present the use of amiodarone should be reserved for patients with life threatening or seriously disabling arrhythmias in whom longer established drugs have been ineffective or are contraindicated.

Adult↗
PubMed1983

Quinidine for ventricular arrhythmias: value of electrophysiologic testing.

Quinidine was evaluated during serial electrophysiologic testing with programmed ventricular stimulation in 89 patients with life-threatening ventricular arrhythmias. In 30 of the 89 patients, quinidine therapy prevented the initiation of ventricular tachycardia (VT) during programmed ventricular stimulation. In 8 additional patients no single drug tested was effective, and quinidine in combination with either mexiletine (7 patients) or propranolol (1 patient) prevented the initiation of VT during electrophysiologic testing. The mean serum concentrations of quinidine in the patients who responded and those who failed to respond were 2.9 +/- 0.8 and 2.8 +/- 1.1 micrograms/ml, respectively; however, but nonresponders were characterized by more severe congestive heart failure and an increased incidence of digitalis use. During chronic therapy (24 +/- 3 months) with quinidine either alone or in combination with a second antiarrhythmic drug in the 38 patients whose arrhythmia had been suppressed during electrophysiologic testing, 32 (84%) remain symptom-free while 3 have had recurrent arrhythmia and 3 discontinued quinidine because of adverse effects. These data demonstrate that quinidine, when selected on the basis of electrophysiologic testing, provides effective long-term prophylaxis against recurrent ventricular arrhythmia and that approximately 40% of patients tested are likely to respond either to quinidine alone or quinidine in combination with another antiarrhythmic agent.

Aged↗
PubMed1983

Electrophysiologic studies before and after myocardial revascularization in patients with life-threatening ventricular arrhythmias.

Electrophysiologic studies with programmed cardiac stimulation were performed in a selected group of 17 patients with severe proximal coronary artery disease involving at least 2 major vessels and left ventricular ejection fractions greater than 30% who were undergoing coronary artery bypass graft surgery after prehospital cardiac arrest or ventricular tachycardia (VT) unassociated with acute myocardial infarction. Before surgery and without antiarrhythmic drug therapy, programmed cardiac stimulation induced ventricular fibrillation (VF) in 4 patients, and VT (greater than or equal to 5 beats) in 11 patients. Inducible VT or VF was suppressed by antiarrhythmic drugs in 7 of 13 patients in whom they were tried. Patients underwent coronary artery bypass graft surgery unassociated with perioperative myocardial infarction. When studied again an average of 19 days after surgery, 10 patients had no inducible VT or VF without antiarrhythmic drug therapy; 6 had induced VT. One patient had spontaneous VT. An effective antiarrhythmic regimen that suppressed inducible or spontaneous VT, or both, was defined by serial electrophysiologic studies in 4 patients, whereas 3 patients continued to manifest electrically inducible VT with all antiarrhythmic regimens tested. All but 1 patient, in whom postoperative VT could not be suppressed, are free of arrhythmias after a mean follow-up period of 23 months (range 6 to 53). It is concluded that myocardial revascularization alone may improve the abnormal electrophysiologic findings in certain patients; however, this effect of coronary artery bypass graft surgery is unpredictable, and pre- and postoperative electrophysiologic studies are recommended as part of the evaluation of these patients.

Aged↗
PubMed1982

Complications in patients undergoing cardiac electrophysiologic procedures.

Complications were seen in 20 of 359 patients having programmed electrical stimulation during 1062 cardiac electrophysiologic procedures. No deaths occurred. Direct current countershock was used to end arrhythmias with serious hemodynamic consequences on 107 occasions. Countershock was effective in all cases and not associated with morbidity. The complications in 20 patients were related to intravascular catheterization and included thromboembolism (nine patients), local or systemic infections (six patients), and pneumothorax (five patients). All 20 patients recovered from these complications without long-term sequelae. Intracardiac electrophysiologic procedures can be done with an acceptably low risk in patients with life-threatening or disabling arrhythmias.

Arrhythmias, Cardiac↗
PubMed1981

Mexiletine for refractory-ventricular arrhythmias: results using serial electrophysiologic testing.

Mexiletine was administered during serial drug testing to 35 patients with electrically inducible ventricular arrhythmias and to 6 with recurrent ventricular tachycardia that could not be induced or terminated by programmed cardiac stimulation. All patients had arrhythmias resistant to all conventionally available agents. Electrically induced arrhythmias were completely suppressed during mexiletine therapy in 13 patients. In 12 patients no antiarrhythmic regimen was completely suppressive and in 7 of these mexiletine favorably modified the response to programmed stimulation. In four of six patients with frequent episodes of spontaneous ventricular tachycardia that were not inducible by programmed cardiac stimulation, arrhythmia was controlled by mexiletine. The presence of complete arrhythmia suppression with mexiletine during acute testing accurately predicted long-term freedom from recurrent arrhythmia in 16 of 17 patients over a mean follow-up period of 12.6 +/- 6 months. Severe adverse neurologic effects were noted early during mexiletine therapy in three patients, but no patient discharged on such therapy experienced major adverse effects. The study demonstrates that mexiletine can provide well tolerated effective prophylaxis against recurrent ventricular arrhythmias in a significant proportion of patients resistant to conventional drugs.

Aged↗
PubMed1981

Nonsustained polymorphic ventricular tachycardia induced by electrical stimulation in 3 week old canine myocardial infarction.

To study the electrophysiology of ventricular tachycardia 3 to 4 weeks after myocardial infarction in a canine model, an anteroapical transmural infarct was created in 40 dogs by ligation of the left anterior descending coronary artery. An average of 25 days after myocardial infarction 32 dogs that survived the infarction and 4 control dogs with a sham operation underwent open chest electrophysiologic study. No ventricular arrhythmias could be induced by any mode of ventricular stimulation in any of the four control animals. Twenty-seven of 32 dogs with myocardial infarction had reproducible ventricular arrhythmias in response to ventricular stimulation. In 17 animals sustained uniform ventricular tachycardia could be reproducibly initiated by programmed ventricular stimulation. In another 10 dogs with myocardial infarction, the same modes of ventricular stimulation reproducibly initiated ventricular fibrillation. Seven of these 10 dogs also manifested reproducible nonsustained polymorphic ventricular tachycardia, characterized by beat to beat variation in QRS complex configuration and cycle length, in response to programmed ventricular stimulation. Nonsustained polymorphic ventricular tachycardia and sustained uniform ventricular tachycardia were rarely observed in the same dog and appeared to have different underlying mechanisms.

Animals↗