Reversal of flecainide-induced ventricular arrhythmia by hypertonic sodium bicarbonate in dogs

Management of life-threatening flecainide overdose: a case report of an infant

Flecainide overdose is associated with an approximately 10% mortality rate. The drug's slow rate of elimination and high oral bioavailability make successful management extremely challenging. I present the management of a life-threatening flecainide overdose of an infant who had a protracted course due to the exposure to the drug in both the fetal and neonatal periods.

Flecainide Toxicity Secondary to Accidental Overdose: A Pediatric Case Report of Two Brothers

Flecainide is a class 1C antiarrhythmic with a narrow therapeutic window and thereby a high-risk medication for causing acute toxicity. Dysrhythmias secondary to flecainide ingestion are often refractory to antiarrhythmics and cardioversion, and patients commonly require extracorporeal support. We review the successful resuscitation of two brothers aged 2 and 4 who presented two years apart with unstable wide-complex tachyarrhythmia suspicious for severe flecainide toxicity. Each patient received sodium bicarbonate and 20% intravenous lipid emulsion with a full recovery. While extracorporeal support is often required following flecainide ingestion, we present two cases where it was avoided due to aggressive multimodal management with sodium bicarbonate, electrolyte repletion, and 20% intravenous lipid emulsion. In addition, avoidance of agitation-induced tachycardia may be beneficial.

[Flecainid intoxication: Evolution, complications and care of]

This report presents the case of a young man of 24 years old with Asperger syndrome who ingest quantities of medication whose flecainide. Resume of his stay in intensive care unit, notably serious adverse effect which ventricular tachycardia with membrane stabilizing effect and lengthening of stay in intensive care unit. Study of literature of different take care already published, with notion of mid-term leaching of flecainide which were ingest days before, at different levels all over the world.

Review on Flecainide Poisoning

Flecainide acetate is a Vaughn-Williams class IC antiarrhythmic. It is used mainly for treatment of supraventricular arrhythmias due to reentry and is highly effective in suppressing frequent premature ventricular depolarization and nonsustained ventricular tachycardia (VT). Although less than 1% of drug overdoses are fatal, severe intoxication with Vaughn-Williams class IC antiarrhythmics is associated with average mortality of 22.5% and the rate of mortality after flecainide overdose is approximately 10%. Severe flecainide overdose is frequently fatal because of the rapid onset of hypotension and ventricular arrhythmias. Its cardiotoxicity is mainly due to its sodium and potassium channels blocking effects. Commonly recommended therapies like haemolysis or haemoperfusion is not helpful because of its large volume of distribution. As a result, the treatment goals are to decrease the amount of blockade; correct aggravating conditions for arrhythmias, such as electrolytes disturbances or hypoxia; avoid drugs with sodium channels blocking effects. Recently, there are some successful data on using peripheral cardiopulmonary bypass technique in the treatment of severe flecainide intoxication. This may be a promising treatment option in this type of drug overdose.

Flecainide toxicity in a preterm neonate with permanent junctional reciprocating tachycardia

We report a case of flecainide toxicity in a premature neonate with permanent junctional reciprocating tachycardia which was managed successfully by reversal of the sodium blockade with intravenous sodium bicarbonate and supportive care. This report highlights the importance of strict supervision and monitoring while administering antiarrhythmic drugs in neonates and prompt institution of appropriate remedial action for treatment when toxicity is suspected.

A case of near-fatal flecainide overdose in a neonate successfully treated with sodium bicarbonate

BACKGROUND

Flecainide is a class IC antidysrhythmic primarily indicated for ventricular dysrhythmias and supraventricular tachycardia (SVT). Class IC antidysrhythmic overdose has a reported mortality of 22%, and death results from dysrhythmias and cardiovascular collapse. We report a near-fatal flecainide overdose in an 18-day-old treated successfully with sodium bicarbonate.

CASE REPORT

An 18-day-old, 2 weeks premature, 4-kg boy developed persistently high heart rates (220-240 beats/min) and electrocardiographic changes consistent with SVT. There was minimal response to vagal maneuvers, adenosine, and esmolol, and a transthoracic echocardiogram showed no underlying structural abnormality. The patient was then started on flecainide 4 mg orally every 8 h (Q8h). After the fourth dose he developed lethargy, cold clammy skin, and a heart rate of 40 beats/min with no palpable pulse. The patient was given 0.1 mg of atropine intravenously, with an increase of the heart rate to 160 beats/min. The child's cardiac monitor revealed a wide-complex tachycardia with left bundle branch morphology, with associated pallor and poor capillary refill. Sodium bicarbonate was administered intravenously due to suspected flecainide toxicity. Approximately 5 min after intravenous administration of 10 mEq of 8.4% sodium bicarbonate twice, his rhythm converted to a narrow-complex tachycardia. A serum flecainide concentration was 1360 μg/L (therapeutic, 200-1000 μg/L) drawn 1 h before the cardiac arrest. It was later discovered that a twofold dosing error occurred: the patient received 8 mg Q8h instead of 4 mg Q8h for four doses.

CONCLUSION

Flecainide toxicity in children is rare, especially in neonates. It is important for clinicians to be able to identify and treat this uncommon poisoning.

Managing cardiovascular collapse in severe flecainide overdose without recourse to extracorporeal therapy

Flecainide overdose can rapidly result in profound cardiovascular collapse, and is associated with a relatively high mortality. A case is described where a woman with major toxicity and high serum levels was managed without recourse to invasive modalities such as cardiopulmonary bypass or extracorporeal therapies. Hypertonic sodium bicarbonate is recognized as effective therapy for hypotension and arrhythmias. More recent case reports have concentrated on the use of cardiopulmonary bypass. In this report and other reports describing successful resuscitation, the total dose of sodium bicarbonate is conspicuously higher than in reports describing extracorporeal interventions. Sodium bicarbonate should be given early in the resuscitation, and re-administered as frequently as required, targeting an alkaline pH and improved cardiac output, while accepting hypernatraemia. This case demonstrates the maxim that the correct dose of hypertonic sodium bicarbonate is 'enough'. Cardiopulmonary bypass support can be considered as a salvage therapy.

Extracellular acidosis modulates drug block of Kv4.3 currents by flecainide and quinidine

INTRODUCTION

As a molecular model of the effect of ischemia on drug block of the transient outward potassium current, the effect of acidosis on the blocking properties of flecainide and quinidine on Kv4.3 currents was studied.

METHODS AND RESULTS

Kv4.3 channels were stably expressed in Chinese hamster ovary cells. Whole-cell, voltage clamp techniques were used to measure the effect of flecainide and quinidine on Kv4.3 currents in solutions of pH 7.4 and 6.0. Extracellular acidosis attenuated flecainide block of Kv4.3 currents, with the IC50 for flecainide (based on current-time integrals) increasing from 7.8 +/- 1.1 microM at pH 7.4 to 125.1 +/- 1.1 microM at pH 6.0. Similar effects were observed for quinidine (IC50 5.2 +/- 1.1 microM at pH 7.4 and 22.1 +/- 1.3 microM at pH 6.0). Following block by either drug, Kv4.3 channels showed a hyperpolarizing shift in the voltage sensitivity of inactivation and a slowing in the time to recover from inactivation/block that was unaffected by acidosis. In contrast, acidosis attenuated the effects on the time course of inactivation and the degree of tonic- and frequency-dependent block for both drugs.

CONCLUSION

Extracellular acidosis significantly decreases the potency of blockade of Kv4.3 by both flecainide and quinidine. This change in potency may be due to allosteric changes in the channel, changes in the proportion of uncharged drug, and/or changes in the kinetics of drug binding or unbinding. These findings are in contrast to the effects of extracellular acidosis on block of the fast sodium channel by these agents and provide a molecular mechanism for divergent modulation of drug block potentially leading to ischemia-associated proarrhythmia.

Flecainide test in Brugada syndrome: a reproducible but risky tool

The flecainide test is widely used in Brugada syndrome. However, its reproducibility and safety remain ill-defined. This study included 22 patients (18 men, mean age 34 years). Mutations in the SCN5A gene were found in eight patients. Two patients had aborted sudden cardiac death, 8 had syncope/presyncope, and 12 were asymptomatic. The ECG was diagnostic in 19 patients and suggestive in 3. At baseline, 21 of 22 patients underwent a flecainide test (2 mg/kg IV bolus over 10 minutes). In 21 of 21 patients the test was diagnostic or amplified the typical ECG pattern. At the end of drug infusion, sustained VT lasting 7-10 minutes developed in two patients. A second flecainide test was performed within 2 months in 20 patients. The test was not repeated in the two patients with prior development of VT. The flecainide test was diagnostic in 20 of 20 patients. Sustained VT occurred in one patient and recurrent VF in another. The reproducibility of the flecainide test was 100%. In 4 (18%) of 22 patients major VAs were documented after the end of flecainide infusion. VA occurred in 3 (43%) of 7 patients with, versus 1 (7%) 15 without SCN5A gene mutation (P < 0.05). No diagnostic ECG changes or arrhythmias developed in 25 control patients without structural heart disease who underwent the same study protocol. This study shows a high flecainide reproducibility, supporting its diagnostic value in Brugada syndrome. However, the occurrence of major VA, significantly higher in patients with documented SCN5A gene mutation, including in asymptomatic patients, mandates the performance under appropriate medical supervision. Whether a slower rate of drug infusion can lower the risk of VA induction, while maintaining the sensitivity of the test should be explored.

Buffering hypercapnic acidosis worsens acute lung injury

Hypoventilation, associated with hypercapnic acidosis (HCA), may improve outcome in acute lung injury (ALI). We have recently reported that HCA per se protects against ALI. The current study explored whether the mechanisms of protection with HCA were related to acidosis versus hypercapnia. Because CO(2) equilibrates rapidly across cell membranes, we hypothesized that (1) HCA would afford greater protection than metabolic acidosis. We further hypothesized that (2) buffering HCA would attenuate its protection. Forty isolated perfused rabbit lung preparations were randomized to: control (normal pH, PCO(2)); HCA; metabolic acidosis; or buffered hypercapnia. After ischemia-reperfusion (IR) injury wet:dry ratio was greatest with control and buffered hypercapnia, and rank order of capillary filtration coefficient was: control approximately buffered hypercapnia > metabolic acidosis > HCA. Isogravimetric pressure reduction was greatest with buffered hypercapnia. Despite comparable injury, pulmonary artery pressure elevation was less with buffered hypercapnia versus control. In vitro xanthine oxidase (XO) activity depended on pH, not PCO(2). We conclude that: (1) HCA and metabolic acidosis are protective, but HCA is the most protective; (2) buffering HCA attenuates its protection; (3) buffering HCA causes pulmonary vasodilation; (4) because metabolic acidosis and HCA similarly inhibit in vitro XO activity, the differential effects cannot be explained solely on the basis of extracellular XO activity.

Direct effects of class I antiarrhythmic drugs on epicardial electrograms in dogs

The effects of class I antiarrhythmic drugs on epicardial electrograms during regular atrial pacing were investigated in anesthetized, open-chest dogs. Lidocaine, flecainide or disopyramide was infused selectively into the distal site of the left-anterior descending artery. Lidocaine produced a dose-dependent elevation of ST segment without changing the amplitude of R wave. Flecainide produced a dose-dependent increase of R-wave amplitude accompanied by the augmentation of negative T. The ST segment was elevated at the high dose. The QRST area did not change at the low dose but significantly increased at the high dose, indicating that the ST-T change at the low dose was secondary to changes in ventricular depolarization. The effects of disopyramide on R wave and ST segment were between those of lidocaine and flecainide. The major action of lidocaine was the acceleration of ventricular repolarization while that of flecainide was the deceleration of ventricular conduction. Disopyramide had an action that was intermediate between the two drugs.

Fatal flecainide intoxication

Flecainide acetate is a potent class 1C antiarrhythmic agent used mainly for the treatment of supraventricular arrhythmias. Acute overdose of this drug is rare but frequently fatal. The clinical course of a patient that ingested a large quantity of flecainide as a suicide attempt is described and current therapeutic strategies discussed.

Poisoning by sodium channel blocking agents

Poisoning by drugs that block voltage-gated sodium channels produces intraventricular conduction defects, myocardial depression, bradycardia, and ventricular arrhythmias. Human and animal reports suggest that hypertonic sodium bicarbonate may be effective therapy for numerous agents possessing sodium channel blocking properties, including cocaine, quinidine, procainamide, flecainide, mexiletine, bupivacaine, and others.

Electrophysiologic effects of sodium channel blockade on anisotropic conduction and conduction block in canine myocardium: preferential slowing of longitudinal conduction by flecainide versus disopyramide or lidocaine

OBJECTIVES

The purpose of this study was to determine the effects of sodium channel blockade on anisotropic excitation propagation in the intact canine left ventricle.

BACKGROUND

Anisotropic ventricular conduction- electric conductivity dependent on the myocardial fiber direction-is one of the important mechanisms of ventricular arrhythmia. However, the effects of sodium channel blockade, especially the differential effect of a subclass of this agent, on the anisotropic properties remain unknown.

METHODS

In 28 anesthetized, open chest dogs, a small cannula was inserted into the left anterior descending coronary artery. Saline (control), disopyramide, lidocaine or flecainide was infused selectively into the cannula. An array of 64 epicardial electrodes was placed on the anterior surface of the ventricle. Activation time (AT) was measured along the longitudinal (L) and transverse (T) directions.

RESULTS

High dose flecainide (100 microg/kg body weight per min) delayed the AT along the L direction markedly (mean [+/-SE] 227 +/- 38%, p < 0.02) and mildly (121 +/- 10%, p < 0.02) along the T direction in regular beats (p < 0.007, L vs. T). Lidocaine and disopyramide did not show direction-dependent prolongation of the AT on regular beats. When examined on premature beats, AT was delayed, depending on the coupling interval and the fiber direction when saline, flecainide or lidocaine was infused. The conduction blocks along the L direction were observed in three of seven dogs on regular beats after flecainide and ventricular fibrillation ensued in two of these three dogs.

CONCLUSIONS

A peculiar slowing of L conduction by flecainide may relate to the character of proarrhythmia.

Sodium bicarbonate to correct widened QRS in a case of flecainide overdose

A 16-yr-old male attempted suicide by ingesting approximately 4000 mg of flecainide. He developed coma, hypotension, and ventricular tachycardia. In addition to supportive care and antidysrhythmics, he received intravenous sodium bicarbonate for the wide complex dysrhythmia. Animal studies and anecdotal human experience have suggested that increasing the extracellular sodium improves cardiac conduction in flecainide toxicity. The patient's QRS narrowed immediately following sodium bicarbonate infusion. Sodium bicarbonate may be useful in the treatment of widened QRS and ventricular ectopy resulting from flecainide toxicity.