Safety and efficacy of intravenous diltiazem in atrial fibrillation or atrial flutter

This study examines the efficacy of various doses of intravenous diltiazem to control the ventricular response during atrial fibrillation or atrial flutter. Control of the ventricular response of patients with atrial fibrillation and a rapid ventricular response can provide patients with relief of symptoms and improve hemodynamics. Eighty-four consecutive patients with atrial fibrillation or atrial flutter, or both, received an intravenous bolus dose of diltiazem followed by a continuous infusion of diltiazem at 5, 10, and 15 mg/hour. The mean ventricular response and blood pressure were monitored. Overall, 94% of patients (79 of 84) responded to the bolus dose with a > 20% reduction in heart rate from baseline, a conversion to sinus rhythm, or a heart rate < 100 beats/min. Seventy-eight patients received the continuous infusion. After 10 hours of infusion, 47% of patients (confidence interval [CI]: 36%, 59%) had maintained response with the 5 mg/hour infusion, 68% (CI: 57%, 79%) maintained response after the infusion was titrated to 10 mg/hour, and 76% (CI: 66%, 85%) after titration from the 5 and 10 mg/hour infusion to the 15 mg/hour dose. For the 3 diltiazem infusions studied, mean (+/- SD) heart rate was reduced from a baseline value of 144 +/- 14 beats/min to 98 +/- 19, 107 +/- 25, 107 +/- 22, 101 +/- 22, 91 +/- 17, and 88 +/- 18 beats/min at infusion times 0, 1, 2, 4, 8, and 10 hours, respectively. By the end of the infusion, 18% of patients (14 of 78) had conversion to sinus rhythm.(ABSTRACT TRUNCATED AT 250 WORDS)

Intravenous amiodarone vs propafenone for atrial fibrillation and flutter after cardiac operation

The safety and efficacy of amiodarone and propafenone in converting atrial fibrillation or flutter after cardiac surgery were compared in a randomized double-blind trial. Eighty-four patients with sustained atrial tachyarrhythmias of more than 30 min' duration, stable hemodynamic status and neither preoperative atrial arrhythmias nor treatment with other antiarrhythmis drugs, were randomized to receive amiodarone (46 patients: 5 mg/kg over 15 min and then 15 mg/kg over the subsequent 24 h for non-converting) or propafenone (38 patients: 2 mg/kg over 15 in and then 10 mg/kg over the subsequent 24 h for non-converting). Nine of the 46 patients (19.5%) receiving amiodarone converted to sinus rhythm within 1 h following bolus injection compared with 17 of 38 patients (44.7%) treated with propafenone (P < 0.05). Within the 24 h study, 38 of 46 patients (82.6%) given amiodarone and 26 of 38 patients (68.4%) given propafenone were converted to sinus rhythm (P = NS). A significantly progressive reduction in ventricular response, already evident at 10th min from the start of treatment, was achieved in both groups of patients. Side effects occurred in six patients given propafenone (15.7%) and in five given amiodarone (10.8%) (P = NS). The two drugs were equally effective in converting postoperative atrial fibrillation and/or flutter after 24 h although propafenone was superior within the first hour.

[Results of oral sotalol therapy in children with supraventricular and ventricular arrhythmias]

Experience with oral sotalol, a beta-blocker with class III-antiarrhythmic properties, is limited in the pediatric population. Sotalol was administered to 32 patients with a mean age of 8.7 years (range 1 day-19.9 years). Mean dosage was 4.6 (1.5-9.4) mg/kg or 122.1 (52-306) mg/m2, respectively. In 27/32 patients, at least 1 antiarrhythmic agent had failed to control the dysrhythmia before sotalol was started. Cardiac diagnoses included normal heart (n = 16), status after correction of congenital heart disease (n = 13), and cardiomyopathy (n = 3). Success (based on symptoms and 24-h electrocardiogram) was achieved in 16/18 patients with reentry supraventricular tachycardia, in 7/8 patients with atrial flutter, and in 4/6 patients with ventricular tachycardia. During a mean follow-up of 15.6 (2-78) months, proarrhythmia occurred in five (16%) patients (symptomatic bradycardia n = 2, QT-prolongation and ventricular extrasystoles n = 1, ventricular extrasystoles n = 1, 2 degrees av-block n = 1), requiring dosage reduction (n = 3), cessation of treatment (n = 1) and pacemaker implantation in one patient, respectively. Symptomatic hypotension was noted in two patients, in whom therapy had to be stopped. Sotalol was a very effective agent for the treatment of various pediatric cardiac dysrhythmias. However, incidence of proarrhythmic effects warrants close electrocardiographic monitoring.

Intravenous diltiazem for the treatment of patients with atrial fibrillation or flutter and moderate to severe congestive heart failure

The objective of this multicenter, randomized, double-blind, placebo-controlled study was to determine the safety and efficacy of intravenous diltiazem in the treatment of 37 patients with rapid (ventricular rate, mean +/- SD 142 +/- 17 beats/min) atrial fibrillation or flutter and moderate to severe congestive heart failure (ejection fraction, mean +/- SD 36 +/- 14%; New York Heart Association class III [23 patients], class IV [14 patients]). During the double-blind portion of the study, patients received either intravenous diltiazem, 0.25 mg/kg over 2 minutes, or placebo followed 15 minutes later by diltiazem or placebo, 0.35 mg/kg over 2 minutes, if the first dose was tolerated but ineffective. Placebo nonresponders were given open-label intravenous diltiazem in a similar fashion as in the double-blind portion of the study. In the double-blind part of the study, 21 (18 with 0.25 mg/kg, 3 with an additional 0.35 mg/kg) of the 22 patients (95%) responded to diltiazem, and 0 of 15 patients (0%) responded to placebo (p < 0.001). All 15 patients (13 with 0.25 mg/kg and 2 with an additional 0.35 mg/kg) who received placebo during the double-blind period had a therapeutic response to diltiazem during open-label therapy. Overall, 36 of 37 patients (97%) had a therapeutic response to intravenous diltiazem. Heart rate response to diltiazem after the 2-minute bolus infusions consisted of a > or = 20% decrease in heart rate from baseline in 36 patients; in addition, 17 patients also had heart rates decreased to < 100 beats/min, whereas no patient had conversion to sinus rhythm.(ABSTRACT TRUNCATED AT 250 WORDS)

Management outcome and follow-up of fetal tachycardia

OBJECTIVES

The aim of this study was to evaluate fetal tachycardia and the efficacy of maternally administered antiarrhythmic agents and the effect of this therapy on delivery and postpartum management.

BACKGROUND

Sustained fetal tachycardia is a potentially life-threatening condition in which pharmacologic therapy is reported to be effective. There is ongoing discussion about optimal management.

METHODS

A group of 51 patients with M-mode echocardiographically documented fetal tachycardia was studied retrospectively.

RESULTS

Thirty-three fetuses had supraventricular tachycardia; 15 had atrial flutter; 1 had two episodes of both; and 2 had ventricular tachycardia. Fetal hydrops was seen in 22 patients. Thirty-four fetuses received maternal therapy with either digoxin or flecainide as the first administered drug (additional drugs were given in 12). Drug treatment was successful in establishing acceptable rhythm control in 82% (84% without, 80% with hydrops). In the latter group the median number of drugs and number of days to conversion were higher. Three patients with fetal hydrops died. In 50% of cases, tachycardia reappeared at delivery: 9 neonates presented with atrial flutter, 14 with supraventricular tachycardia and 1 with ventricular tachycardia. Seventy-eight percent of the group had pharmacologic therapy by 1 month of age and 14% by 3 years.

CONCLUSIONS

Fetal tachycardia can be treated adequately in the majority of patients, even in the presence of hydrops, and therefore emergency delivery might not be indicated. Digoxin and flecainide were drugs of first choice and produced no serious adverse effects in this series of patients. The majority of patients do not require prolonged therapy.

A clinical study of amiodarone as a single oral dose in patients with recent-onset atrial tachyarrhythmia

Forty-five patients with recent-onset sustained atrial tachyarrhythmia (mean heart rate at entry; 140.0 +/- 3.5 beats.min-1) associated with various cardiovascular diseases were treated by oral amiodarone, given as a single loading dose of 25.7 +/- 0.9 mg.kg-1 body weight. Conversion to sinus rhythm was observed in 29 patients during the first 24 h of treatment, leading to a success rate of 64.4%. Five additional patients converted to sinus rhythm with continuation of oral amiodarone, (10-15 mg.kg-1 by day) with a mean delay of 4.2 days. A similar population of 27 patients (mean heart rate at entry; 140 +/- 3 beats.min-1) was treated by intravenous amiodarone, given as a bolus infusion of 3-5 mg.kg-1 over 30 min (mean; 4.1 +/- 0.2 mg.kg-1), followed by a continuous infusion of 10-15 mg.kg-1 for 24 h (mean; 11.1 +/- 0.7 mg.kg-1). Eighteen patients converted to sinus rhythm during the first 24 h of therapy, leading to a success rate of 66.7%. Minor adverse effects of therapy were observed in two patients given oral amiodarone, and in seven given intravenous amiodarone. No major effect was observed. We suggest that amiodarone given as a single oral loading dose of 25-30 mg.kg-1 body weight is an effective, simple and well-tolerated therapy, suitable for most patients with recent-onset ATA.

Atrial flutter can be terminated by a class III antiarrhythmic drug but not by a class IC drug

In atrial flutter, chemical conversion with class I drugs is often unsuccessful, whereas class III drugs seem more promising. The different electrophysiological effects of these drugs may explain this discrepancy. To date, only experimental data show the differential effects of these drugs on conversion rate and atrial flutter cycle length. This study evaluates the effects of the class IC antiarrhythmic drug flecainide, and of dofetilide, a new class III drug, on conversion rate and flutter cycle length in patients with atrial flutter. Flecainide (11 patients) was given as an intravenous bolus of 2 mg.kg-1 in 10 min and dofetilide (10 patients) as a maximum intravenous bolus of 8 micrograms.kg-1 in 15 min. Baseline characteristics were comparable between both groups. Only one patient treated with flecainide converted to sinus rhythm. This patient showed the largest flutter cycle length increase (280 to 420 ms). By contrast, seven of the 10 patients treated with dofetilide converted to sinus rhythm. Patients treated with flecainide showed a significantly larger increase in atrial flutter cycle length at the end of the infusion compared to the dofetilide-treated patients (from 226 +/- 28 to 317 +/- 52 ms vs from 221 +/- 26 to 239 +/- 39 ms, respectively). In conclusion, dofetilide is more effective than flecainide in the conversion of atrial flutter to sinus rhythm, despite the fact that flecainide produced a more prolonged flutter cycle length. Thus, action potential prolongation in the absence of conduction slowing seems more effective in terminating human atrial flutter than depression of the excitability.

Clinical experience with propafenone for cardiac arrhythmias in the young

Seventy-two children were treated with propafenone between 1980 and 1990. The mean age was 34 months (range 0-192). Arrhythmias included atrioventricular re-entry tachycardia in 32 patients (44%), atrial flutter in 16 (22%), atrial or junctional ectopic tachycardia in 10 (14%), atrial re-entry tachycardias in three (4%) and ventricular arrhythmias in 11 patients (16%). The efficacy of oral treatment was good in patients with atrio-ventricular re-entry tachycardia (80%), atrial flutter (71%) and atrial ectopic tachycardia (83%); it was poor in ventricular arrhythmias (40%). The mean oral dose was 13.5 mg.kg-1. day-1. Dosage and serum levels of propafenone did not differ whether the patients were treated successfully or not. No correlation between dosage and serum level was observed. Intravenous propafenone administration was only partially successful in suppressing supraventricular tachycardias (6 of 11 patients). The presence of a congenital heart defect and the time of onset of the arrhythmias had a significant influence on the efficacy of propafenone. Better results were observed in patients with normal hearts and in whom onset of arrhythmia was pre-natal (success 80%) as well as in patients with arrhythmias seen early after surgery for congenital heart defects (success 87%). Success (65%) was also observed in patients without congenital heart defects and postnatal onset of supraventricular arrhythmias. Patients with ventricular or supraventricular arrhythmias late after corrective surgery showed the poorest response (31%).

Clinical decision analysis modeling: short-term control of ventricular response rate in atrial fibrillation or atrial flutter-digoxin versus diltiazem

OBJECTIVE

To develop a clinical decision model to compare the outcome of therapy with digoxin versus diltiazem for short-term control of ventricular response rate (VRR) in patients with atrial fibrillation or atrial flutter.

DESIGN

Review of data from two studies that examined the percentages of response and frequency of adverse reactions in patients treated with intravenous digoxin or diltiazem to control VRR in atrial fibrillation or flutter. We constructed a clinical decision model and performed sensitivity analysis to determine if the model's predictions could be altered.

SETTING

Large teaching, university hospitals.

PARTICIPANTS

Adults age 18 years or older treated with intravenous digoxin or intravenous diltiazem for atrial fibrillation or flutter (VRR > or = 120 beats/min). Patients with severe heart failure New York Heart Association class III or IV, a surgical procedure prior to the exacerbation, or an acute myocardial infarction were excluded.

MEASUREMENTS AND MAIN RESULTS

We measured VRR control after 1 and 24 hours of therapy (VRR < 100 beats/min or decrease of > or = 20%) and assessed the likelihood that a patient would suffer an adverse drug reaction. Initial assumptions were that the probability digoxin would achieve VRR control was 0.10 (95% confidence interval 0.04-0.20) at 1 hour and 0.70 (95% CI 0.56-0.80) at 24 hours; the probability that diltiazem would achieve VRR control was 0.94 (95% CI 0.82-0.99) at 1 hour and 0.83 (95% CI 0.68-0.94) at 24 hours; and the probability of no serious adverse drug reaction would be 0.90 (95% CI 0.80-0.96) for digoxin and 0.96 (95% CI 0.86-0.98) for diltiazem.

RESULTS

Diltiazem was superior to digoxin with respect to the composite end point score at 1 hour (91.20 vs 17.29) and 24 hours (81.65 vs 66.43). Digoxin was superior to diltiazem at 24 hours only if the VRR was assumed to be at the highest 95% CI limit for digoxin and simultaneously at the lowest 95% CI for diltiazem (74.62 vs 68.63).

CONCLUSIONS

Clinical decision analysis suggests that intravenous diltiazem is superior to intravenous digoxin in controlling VRR in patients with atrial fibrillation or flutter.

Effects of procainamide and propafenone on the composition of the excitable gap in canine atrial reentry tachycardia

The effects of procainamide and propafenone on the composition of the excitable gap (EG) were studied in a canine model of atrial flutter (AFI) around the tricuspid valve. In 14 open-chest, chloralose-anesthetized dogs, a Y-shaped incision was made in the intercaval area extending to the right atrial appendage. Atrial effective refractory period (ERP) was measured at constant stimulation cycle lengths (CLs) (200 and 300 msec) at each of five recording sites around the tricuspid valve. The EG as defined by the reset-response curve was determined by introducing premature stimuli during AFI induced by burstpacing. Seven dogs each received procainamide or propafenone as a bolus followed by infusion. At constant plasma levels, both drugs increased ERP at constant paced CL and prolonged the reentry CL. In the absence of drug, reset-response curves were mixed, demonstrating an EG composed of both partially (increasing portion) and fully (flat portion) excitable tissue. Procainamide and propafenone shifted the curve upward and to the right and prolonged ERP during AFI, but did not change the duration of the EG. On procainamide, fully excitable tissue was preserved, but on propafenone, in some cases, the fully excitable part of the gap was reduced markedly or even eliminated. In conclusion, both drugs can prolong AFI CL by a direct effect on conduction velocity in fully excitable tissue. In addition, propafenone's effect on refractoriness can contribute significantly in some cases to slowing of AFI.

Mechanism-specific effects of adenosine on atrial tachycardia

BACKGROUND

Recent reports suggest that adenosine, in addition to terminating supraventricular tachycardia involving the atrioventricular (AV) node, may have antiarrhythmic effects on atrial tachycardia. The electrophysiological effects of adenosine on supraventricular tissue include shortening of action potential duration in atrial myocytes mediated by the potassium current, IKACh,Ado; shortening of action potential duration and hyperpolarization in sinus node cells; and anti-adrenergic electrophysiological effects resulting from inhibition of adenylyl cyclase. We therefore hypothesized that the response of atrial tachycardia to adenosine would be mechanism specific, with termination of atrial tachycardia due to sinus node reentry or cAMP-mediated triggered activity, transient suppression of automatic atrial tachycardia, and an absence of antiarrhythmic effect on tachycardia due to intraatrial reentry.

METHODS AND RESULTS

Adenosine (mean +/- SD, 143 +/- 54 micrograms/kg IV) was administered to 27 patients (55 +/- 19 years) in atrial tachycardia whose mechanism was confirmed by electrophysiological study. Adenosine terminated sinus node reentrant tachycardia in 6 of 6 patients and terminated atrial tachycardia due to triggered activity in the 1 patient in whom it was identified. Adenosine transiently suppressed automatic atrial tachycardia in 7 of 7 patients and had no effect in 13 patients with intra-atrial reentrant tachycardia, including 8 patients with atrial flutter.

CONCLUSIONS

These findings demonstrate that adenosine's effects on atrial tachycardia are mechanism specific and can be used to differentiate between reentrant tachycardia confined to the region of the sinus node or atria and between nonreentrant atrial tachycardia due to either triggered activity or automaticity.

Mechanism of interruption of atrial flutter by moricizine. Electrophysiological and multiplexing studies in the canine sterile pericarditis model of atrial flutter

BACKGROUND

Moricizine is said to have potent effects on cardiac conduction but little or no effect on cardiac refractoriness.

METHODS AND RESULTS

The effects of moricizine (2 mg/kg IV) on induced atrial flutter were studied 2 to 4 days after the creation of sterile pericarditis in 11 dogs. Ten episodes of stable atrial flutter before and after the administration of moricizine were studied in 9 dogs in the conscious, nonsedated state, and 7 episodes were studied in 6 dogs in the anesthetized, open chest state. In the conscious state, the effects of moricizine on atrial excitability, atrial effective refractory period, and intra-atrial conduction times were studied by recording during overdrive pacing of sinus rhythm from epicardial electrodes placed at selected atrial sites. Moricizine prolonged the atrial flutter cycle length in all the episodes, from a mean of 133 +/- 9 to 172 +/- 27 milliseconds (P < .001), and then terminated 7 of the 10 episodes. Moricizine increased the atrial threshold of excitability from a mean of 2.3 +/- 1.4 to 3.3 +/- 2.2 mA (P < .01) and prolonged intra-atrial conduction times (measured from the sulcus terminalis to the posteroinferior left atrium) from a mean of 58 +/- 6 to 64 +/- 5 milliseconds (P < .005). Prolongation of the atrial effective refractory period from 166 +/- 20 to 174 +/- 24 milliseconds (P < .05) was observed only at the sulcus terminalis site. In the open chest studies, administration of moricizine prolonged the atrial flutter cycle length from a mean of 150 +/- 15 to 216 +/- 30 milliseconds (P < .001) and then terminated the atrial flutter in all 7 episodes. As demonstrated by simultaneous multisite mapping from 95 bipolar sites on the right atrial free wall, the atrial flutter cycle length prolongation was either due to further slowing of conduction in an area of slow conduction in the reentrant circuit of the atrial flutter (5 episodes) or further slowing of conduction in an area of slow conduction plus the development of a second area of slow conduction (2 episodes). The change in conduction times in the rest of the reentrant circuit was negligible (10.9 +/- 8.7% of the total change). In all 7 episodes, the last circulating reentrant wave front blocked in an area of slow conduction.

CONCLUSIONS

Moricizine (1) prolongs the atrial flutter cycle length, primarily by slowing conduction in an area of slow conduction in the reentrant circuit, (2) terminates atrial flutter by causing block of the circulating reentrant wave front in an area of slow conduction of the reentrant circuit, and (3) effectively interrupts otherwise stable atrial flutter in this canine model. The reason for these effects of moricizine are not readily explained by its effects on global atrial conduction times and refractoriness studied during sinus rhythm. Local changes in conduction in an area(s) of slow conduction are responsible for both cycle length prolongation and atrial flutter termination rather than the traditional wavelength concept of head-tail interaction.

Preliminary investigation of the efficacy of sublingual verapamil in the management of acute atrial fibrillation and flutter

The antiarrhythmic properties of sublingual verapamil were investigated in seven patients with acute fast atrial flutter (n = 2) or fibrillation (n = 5). A rapid and significant (P < 0.05) reduction in the ventricular rate was achieved in all seven patients. The ventricular rate at peak plasma verapamil concentration (+/- s.d.) was significantly slower than on admission (101.6 +/- 11.3 and 159 +/- 5.3 beats min-1 respectively, P < 0.01). The ventricular rate remained controlled for over 4 h. Sublingual verapamil was rapidly absorbed with the maximum peak plasma concentration (153.3 +/- 15.5 ng ml-1) being achieved after 1.21 +/- 0.18 h. Side-effects of sublingual verapamil were limited to one report of a bitter taste. The sublingual administration of verapamil may provide an alternative method for the control of acute fast atrial fibrillation and flutter in selected patients.

Efficacy of rapid atrial pacing for conversion of atrial flutter in medically treated patients

To determine factors affecting the success rate of rapid atrial pacing in converting atrial flutter to sinus rhythm in medically treated patients, we prospectively used this technique for 120 consecutive episodes in a total of 110 patients (94 male, 16 female, mean age 63 +/- 14 years). Structural heart disease was present in 77%, and all patients were receiving antiarrhythmic drugs at the time of the procedure. Atrial flutter type I was present in 92 of 110 patients (84%), and atrial flutter type II in 18 of 110 (16%). Primary success rate (return to sinus rhythm either immediately or after < 10 min of atrial fibrillation) was 70% (71/102) for flutter type I, and 6% (1/18) for flutter type II (p < 0.001). Delayed success (conversion to sinus rhythm in > 10 min but < 24 h) was observed in 15 additional episodes of flutter type I (15%) and in 1 additional episode of flutter type II (6%). The only clinical factors predicting primary success were (a) characteristics of flutter waves on the 12-lead surface electrocardiogram, (b) duration of flutter (primary success rate of 81% if flutter < 1 month vs. 57% if > 1 month, p < 0.05), and (c) flutter rate (primary success rate of 78% if < 260/min vs. 56% if > 260/min, p < 0.05). In 6/71 episodes of flutter type I (8%), prolonged sinus pauses or severe bradyarrhythmias occurred after conversion to sinus rhythm.(ABSTRACT TRUNCATED AT 250 WORDS)

New antiarrhythmic drugs in pediatric use: amiodarone

Amiodarone, a class III antiarrhythmic agent, prolongs action potential duration and refractoriness of all cardiac structures. The drug is more rapidly metabolized in pediatric patients than in adults, but its kinetics are still unique compared with other drugs. Due to the unusual pharmacokinetic characteristics of amiodarone, treatment has to be started by administering loading doses, and there is a significant delay both in the achievement of the full anti-arrhythmic effect and in the development of side effects. Amiodarone is a highly effective agent in pediatric patients with automatic and reentrant supraventricular tachycardia as well as in refractory atrial flutter. Efficacy in ventricular tachycardia has been shown to be variable depending on the underlying anatomical substrate. The incidence of side effects is lower than that observed in adult studies with similar duration of therapy but their incidence is still significant. Amiodarone treatment is associated with a significant risk of proarrhythmic effects, requiring hospitalization of the patient during the loading period.

Successful conversion of fetal atrial flutter with digoxin: report of one case

A fetus suffering from tachycardia of more than 200 beats per minute was found to have an atrial flutter with two-to-one atrioventricular conductional block by the fetal ultrasonogram at 33 weeks of gestation. The tachycardia was successfully converted to sinus rhythm with maternal digitalization. The heart rate stayed in a normal sinus rhythm after the baby was born, however, an incomplete form of cor triatriatum was noted on the echocardiogram examination.

Benefits and risks of antiarrhythmic drug therapy after DC electrical cardioversion of atrial fibrillation or flutter

Electrical cardioversion is the method of choice to restore sinus rhythm in patients with chronic atrial fibrillation. After cardioversion, long-term maintenance of sinus rhythm is troublesome since many patients relapse. In addition, haemodynamic complications associated with recurrence and hazards of prophylactic antiarrhythmic drug therapy are among the problems threatening these patients. Several new antiarrhythmics have become available but their safety remains to be established. Advantages of prophylactic antiarrhythmic treatment must be carefully weighed against the hazards. As a consequence, non-pharmacological modalities like serial electrical cardioversions (no drugs) and His bundle ablation may become important treatment modalities. The present report summarizes current antiarrhythmic strategies, focusing primarily on feasibility of prophylactic treatment and on early and late proarrhythmia.

[Efficacy of intravenous propafenone in the management of arterial flutter and fibrillation of recent onset]

We assessed the safety and efficacy of intravenous propafenone in the treatment of atrial fibrillation and flutter of recent onset (1-10 days). The drug was administered, at a dosage of 2 mg/kg, to 46 consecutive patients (with age variable from 35 to 86 years), 36 with atrial fibrillation, 10 with atrial flutter. The efficacy of propafenone was influenced by the interval from the onset of the arrhythmia and the start of therapy. All patients underwent echocardiographic control: mean left atrial dimensions were non significantly different in responders and non responders. Serious hypotension developed in two patients, regressed with appropriate therapy. Non responders showed a significant reduction of ventricular rate. By synthesis, propafenone is a safe and effective drug for treatment of atrial fibrillation or flutter of recent onset, in refractory patients it allows however an adequate control of ventricular rate.

A comparison of amiodarone and digoxin for treatment of supraventricular arrhythmias after cardiac surgery

Despite the widespread use of amiodarone in non-surgical patients, its role in the management of supraventricular tachyarrhythmias after cardiac surgery is not clear. We set out to compare the relative efficacy of amiodarone and digoxin in the management of atrial fibrillation and flutter in the early postoperative period. This prospective randomised trial comprised 30 patients, previously in sinus rhythm, who developed sustained atrial fibrillation or flutter following myocardial revascularisation, valve surgery or combined procedures. Amiodarone was administered as an intravenous loading dose followed by a continuous infusion. Digoxin was given as an intravenous loading dose followed by oral maintenance therapy. Electrocardiographic and haemodynamic monitoring was continued for 24 h after the commencement of treatment. There was a marked reduction in heart rate in both groups, mainly in the first 6 h, from 146 to 89 beats per minute in the amiodarone group and from 144 to 95 in the digoxin group. At the end of the 24 h, one of the 15 patients in the amiodarone group and 3 of the 15 patients in the digoxin group remained in atrial fibrillation. No patient in either group developed adverse reactions. We conclude that intravenous amiodarone therapy is safe and at least as effective as digoxin in the initial management of arrhythmias after cardiac surgery.

Endocardial mapping of reentry around an anatomical barrier in the canine right atrium: observations during the action of the Class IC agent, flecainide

INTRODUCTION

Flecainide is effective in terminating stable atrial flutter in the conscious dog with a Y-shaped right atrial lesion. In this model, flutter is due to circus movement of the impulse around a fixed anatomical barrier.

METHODS AND RESULTS

To investigate the mechanism of flecainide-induced termination of this type of reentry, we determined the pattern of endocardial activation of the right and left atria before and during administration of flecainide by recording simultaneously from 192 electrode pairs in the isolated blood perfused heart. At least five consecutive flutter beats were analyzed before and during flecainide for each of eight termination episodes in five hearts. In all, flecainide increased flutter cycle length (164 +/- 24 msec) by 89% to 309 +/- 77 msec (P < 0.05) before termination. Atrial refractory period and conduction time during paced beats were also increased by flecainide. In five episodes, termination was due to conduction block of the impulse at critical sites within the reentrant circuit (mode 1). Cycle length oscillations (+/- 30 msec) at sites proximal to site of block preceded termination in three of these episodes. In three other episodes, interruption of the original circuit occurred when there was failure of a lateral boundary, giving rise to an impulse that reset the original circuit (mode 2). In these episodes, long-short cycle length oscillations led to return reexcitation by the impulse within the primary path and subsequent termination.

CONCLUSION

In summary, similar to our previous findings with the Class III agent, d-sotalol, two different modes of termination of atrial reentry were observed with flecainide.

Multiple modes of termination of re-entrant excitation around an anatomic barrier in the canine atrium during the action of d-sotalol

In the chronically-instrumented animal and the isolated blood perfused heart, atrial re-entry via a fixed path around an anatomic obstacle has been described and is terminated by the class III antiarrhythmic agent d-sotalol. The precise mechanism by which d-sotalol terminates this arrhythmia is not known. In the present study, right atrial (RA) activation sequences in the isolated, coronary artery perfused canine heart (n = 5) during episodes of sustained flutter and drug administration were determined. A fixed array of bipolar electrodes was used to record endocardial electrograms from 96 sites on the RA simultaneously. Maps of all control flutters showed that the rhythm was due to persistent circus movement of the impulse around the tricuspid valve ring. d-Sotalol was effective in terminating atrial re-entry in this model. In all episodes, block of the excitatory impulse in a specific region of the re-entrant circuit accompanied these terminations. However, the events preceding the occurrence of block of the impulse were not similar. Two different modes of termination are described. The class III antiarrhythmic agent d-sotalol can terminate atrial re-entry in several ways. In one mode, complete conduction block of the re-entering impulse within the fixed path occurs to terminate the rhythm. In the other mode, interruption of the original re-entrant circuit occurs when there is failure of a lateral boundary. In both modes cycle length (CL) oscillations are observed.

Clinical role of d-sotalol and d,l-sotalol in supraventricular arrhythmias, including pre-excitation

Numerous trials performed over the last 20 years, although uncontrolled, have shown the racemic d,l-sotalol is effective for the acute conversion and for long-term prevention of recurrences of supraventricular tachyarrhythmias. Sotalol appeared to be moderately effective in atrial fibrillation or atrial flutter, having somewhat greater efficacy in the case of atrioventricular (AV) nodal re-entrant tachycardia due to Wolff-Parkinson-White syndrome or concealed accessory pathway. These effects may stem from the combined class II and class III electrophysiologic properties of this drug. However, studies comparing d,l-sotalol to pure beta blockers in different 'models', especially postsurgical arrhythmias and Wolff-Parkinson-White syndrome, have suggested that the observed clinical benefit may be related to d,l-sotalol's class III properties. Thus, d-sotalol may be efficacious in these indications. Its precise efficacy should be defined in controlled clinical trials.

[Paroxysmal atrial fibrillation and flutter and "occult" arterial hypertension. The importance of the ambulatory monitoring of the blood pressure. Apropos 2 cases]

The authors describe two hypertensive patients with paroxysmal auricular flutter or fibrillation. The arterial hypertension was suspected because of a hypertensive response in a treadmill stress test, confirmed by a 24-hour blood pressure ambulatory monitoring and there was no damage in target organs. They focus that auricular flutter/fibrillation may be related to "occult hypertension".

Atrial fibrillation and atrial flutter

The epidemiology, pathophysiology, diagnosis, evaluation, and treatment of atrial fibrillation (AF) and atrial flutter (AFl) are reviewed, and recent developments and controversies in the approach to these arrhythmias are addressed. AF and AFl are the arrhythmias most frequently encountered in clinical practice. Although occasionally unaware of their arrhythmia, patients usually complain of palpitations, weakness, dyspnea, and decreased exercise tolerance. The initial goal of therapy is control of the ventricular rate. Rate control is accomplished with atrioventricular node-blocking agents such as digoxin, calcium-channel blockers, or beta-adrenergic blockers. Along with a rapid, irregular ventricular response, other detrimental outcomes of AF and AFl include compromised hemodynamics and increased vulnerability to thromboembolism. After the cause of the patient's arrhythmia has been evaluated, pharmacologic treatment is directed at converting the rhythm to normal sinus rhythm and maintaining it. Antiarrhythmic drugs have proved effective in about 50% of cases but may be associated with increased mortality. More effective and safer forms of drug therapy for AF and AFl are needed. Nonpharmacologic alternatives to antiarrhythmic medications for refractory AF and AFl include radio-frequency catheter ablation of the bundle of His with pacemaker placement and surgery. Patients who remain in AF despite therapy should receive long-term warfarin treatment. Drugs may be used to control the ventricular response in patients with AF and AFl, terminate and prevent the arrhythmias, and prevent thromboembolism. Nonpharmacologic treatments are reserved for patients whose arrhythmias are poorly controlled by drugs.

Amiodarone given by three routes to terminate fetal atrial flutter associated with severe hydrops

BACKGROUND

We describe the concurrent administration of amiodarone using three different routes in order to provide: 1) rapid and adequate fetal loading without giving unduly high doses to the mother, and 2) a maintenance dose to the fetus without risking repeated invasive procedures.

CASE

Rapid atrial flutter was seen on ultrasound in a fetus with severe hydrops at 27 weeks' gestation. Following failed transplacental therapy with sotalol and flecainide, amiodarone was administered to the fetus via the intravenous, intraperitoneal, and transplacental routes. Conversion to sinus rhythm and resolution of hydrops followed this treatment.

CONCLUSION

Combined triple-route administration of amiodarone to the fetus can be effective in treating supraventricular tachycardia and may have a role in the management of life-threatening fetal arrhythmias refractory to transplacental therapy.