Prospective, randomized comparison of conventional and high dose loading regimens of amiodarone in the treatment of ventricular tachycardia

Amiodarone-induced pulmonary toxicity--a fatal case report and literature review

Amiodarone is a widely used and very potent antiarrhythmic substance. Among its adverse effects, pulmonary toxicity is the most dangerous without a causal treatment option. Due to a very long half-life, accumulation can only be prevented by strict adherence to certain dosage patterns. In this review, we outline different safe and proven dosing schemes of amiodarone and compare the incidence and description of pulmonary toxicity. Reason for this is a case of fatal pulmonary toxicity due to a subacute iatrogenic overdosing of amiodarone in a 74-year-old male patient with known severe coronary artery disease, congestive heart failure and ectopic atrial tachycardia with reduced function of kidneys and liver but without preexisting lung disease. Within 30 days, the patient received 32.2 g of amiodarone instead of 15.6 g as planned. Despite early corticosteroid treatment after fast exclusion of all other differential diagnoses, the patient died another month later in our intensive care unit from respiratory failure due to bipulmonal pneumonitis.

Technetium-99m hexamethylpropylene amine oxime lung scintigraphy findings in low-dose amiodarone therapy

Amiodarone (AD)-induced pulmonary toxicity is one of the major complications of long-term AD therapy. Technetium-99m-labeled D: ,L: -hexamethylpropylene amine oxime (Tc-99m HMPAO) scintigraphy has been used to assess lung injury. We designed this study to clarify lung uptake changes of Tc-99m HMPAO using low doses of AD (5 mg/kg/day) during long-term therapy in a rabbit model. Group 1 consisted of 7 rabbits fed with AD by gavage for 6 months. To investigate the effect of ketamine on Tc-99m HMPAO uptake, 5 rabbits were included in Group 2 as a control group. Tc-99m HMPAO scintigraphy was performed in both Group 1 and Group 2 at baseline and after 2, 4, 6, 8, and 12 weeks of AD intake. After 16, 20, and 24 weeks of drug intake, Tc-99m HMPAO scintigraphy was repeated only in group 1. One-min anterior images were acquired 30 min after the injection of 37 MBq of Tc-99m HMPAO. For semiquantitative evaluation, the mean count values were obtained and lung/background and liver/background ratios were calculated. Histopathologic evaluation was performed. No increase in lung and liver uptake of Tc-99m HMPAO was found 2, 4, 6, 8, and 12 weeks after drug intake. There was no significant increase in L/B and H/B ratios of Tc-99m HMPAO in Group 1 compared with Group 2. Both scintigraphic studies and histopathologic examinations showed nonspecific changes. Longitudinal studies investigating Tc-99m HMPAO lung uptake may be planned in patients carrying risk factors for AD-induced lung toxicity.

The International Liaison Committee on Resuscitation (ILCOR) consensus on science with treatment recommendations for pediatric and neonatal patients: pediatric basic and advanced life support

This publication contains the pediatric and neonatal sections of the 2005 International Consensus on Cardiopulmonary Resuscitation and Emergency Cardiovascular Care Science With Treatment Recommendations (COSTR). The consensus process that produced this document was sponsored by the International Liaison Committee on Resuscitation (ILCOR). ILCOR was formed in 1993 and consists of representatives of resuscitation councils from all over the world. Its mission is to identify and review international science and knowledge relevant to cardiopulmonary resuscitation (CPR) and emergency cardiovascular care (ECC) and to generate consensus on treatment recommendations. ECC includes all responses necessary to treat life-threatening cardiovascular and respiratory events. The COSTR document presents international consensus statements on the science of resuscitation. ILCOR member organizations are each publishing resuscitation guidelines that are consistent with the science in this consensus document, but they also take into consideration geographic, economic, and system differences in practice and the regional availability of medical devices and drugs. The American Heart Association (AHA) pediatric and the American Academy of Pediatrics/AHA neonatal sections of the resuscitation guidelines are reprinted in this issue of Pediatrics (see pages e978-e988). The 2005 evidence evaluation process began shortly after publication of the 2000 International Guidelines for CPR and ECC. The process included topic identification, expert topic review, discussion and debate at 6 international meetings, further review, and debate within ILCOR member organizations and ultimate approval by the member organizations, an Editorial Board, and peer reviewers. The complete COSTR document was published simultaneously in Circulation (International Liaison Committee on Resuscitation. 2005 International Consensus on Cardiopulmonary Resuscitation and Emergency Cardiovascular Care Science With Treatment Recommendations. Circulation. 2005;112(suppl):73-90) and Resuscitation (International Liaison Committee on Resuscitation. 2005 International Consensus Conference on Cardiopulmonary Resuscitation and Emergency Cardiovascular Care Science With Treatment Recommendations. Resuscitation. 2005;67:271-291). Readers are encouraged to review the 2005 COSTR document in its entirety. It can be accessed through the CPR and ECC link at the AHA Web site: www.americanheart.org. The complete publication represents the largest evaluation of resuscitation literature ever published and contains electronic links to more detailed information about the international collaborative process. To organize the evidence evaluation, ILCOR representatives established 6 task forces: basic life support, advanced life support, acute coronary syndromes, pediatric life support, neonatal life support, and an interdisciplinary task force to consider overlapping topics such as educational issues. The AHA established additional task forces on stroke and, in collaboration with the American Red Cross, a task force on first aid. Each task force identified topics requiring evaluation and appointed international experts to review them. A detailed worksheet template was created to help the experts document their literature review, evaluate studies, determine levels of evidence, develop treatment recommendations, and disclose conflicts of interest. Two evidence evaluation experts reviewed all worksheets and assisted the worksheet reviewers to ensure that the worksheets met a consistently high standard. A total of 281 experts completed 403 worksheets on 275 topics, reviewing more than 22000 published studies. In December 2004 the evidence review and summary portions of the evidence evaluation worksheets, with worksheet author conflict of interest statements, were posted on the Internet at www.C2005.org, where readers can continue to access them. Journal advertisements and e-mails invited public comment. Two hundred forty-nine worksheet authors (141 from the United States and 108 from 17 other countries) and additional invited experts and reviewers attended the 2005 International Consensus Conference for presentation, discussion, and debate of the evidence. All 380 participants at the conference received electronic copies of the worksheets. Internet access was available to all conference participants during the conference to facilitate real-time verification of the literature. Expert reviewers presented topics in plenary, concurrent, and poster conference sessions with strict adherence to a novel and rigorous conflict of interest process. Presenters and participants then debated the evidence, conclusions, and draft summary statements. Wording of science statements and treatment recommendations was refined after further review by ILCOR member organizations and the international editorial board. This format ensured that the final document represented a truly international consensus process. The COSTR manuscript was ultimately approved by all ILCOR member organizations and by an international editorial board. The AHA Science Advisory and Coordinating Committee and the editor of Circulation obtained peer reviews of this document before it was accepted for publication. The most important changes in recommendations for pediatric resuscitation since the last ILCOR review in 2000 include: Increased emphasis on performing high quality CPR: "Push hard, push fast, minimize interruptions of chest compression; allow full chest recoil, and don't provide excessive ventilation" Recommended chest compression-ventilation ratio: For lone rescuers with victims of all ages: 30:2 For health care providers performing 2-rescuer CPR for infants and children: 15:2 (except 3:1 for neonates) Either a 2- or 1-hand technique is acceptable for chest compressions in children Use of 1 shock followed by immediate CPR is recommended for each defibrillation attempt, instead of 3 stacked shocks Biphasic shocks with an automated external defibrillator (AED) are acceptable for children 1 year of age. Attenuated shocks using child cables or activation of a key or switch are recommended in children <8 years old. Routine use of high-dose intravenous (IV) epinephrine is no longer recommended. Intravascular (IV and intraosseous) route of drug administration is preferred to the endotracheal route. Cuffed endotracheal tubes can be used in infants and children provided correct tube size and cuff inflation pressure are used. Exhaled CO2 detection is recommended for confirmation of endotracheal tube placement. Consider induced hypothermia for 12 to 24 hours in patients who remain comatose following resuscitation. Some of the most important changes in recommendations for neonatal resuscitation since the last ILCOR review in 2000 include less emphasis on using 100% oxygen when initiating resuscitation, de-emphasis of the need for routine intrapartum oropharyngeal and nasopharyngeal suctioning for infants born to mothers with meconium staining of amniotic fluid, proven value of occlusive wrapping of very low birth weight infants <28 weeks' gestation to reduce heat loss, preference for the IV versus the endotracheal route for epinephrine, and an increased emphasis on parental autonomy at the threshold of viability. The scientific evidence supporting these recommendations is summarized in the neonatal document (see pages e978-e988).

Electrophysiologically guided amiodarone therapy versus the implantable cardioverter-defibrillator for sustained ventricular tachyarrhythmias after myocardial infarction: results of long-term follow-up

OBJECTIVES

We sought to compare the long-term survival rates of patients with sustained ventricular tachyarrhythmia after myocardial infarction (MI) who were treated according to the results of electrophysiological (EP) study either with amiodarone or an implantable cardioverter-defibrillator (ICD).

BACKGROUND

Patients with sustained ventricular tachyarrhythmias after MI are at high risk of sudden cardiac death (SCD). However, data comparing the long-term survival rates of patients treated with amiodarone or ICD, according to the results of EP testing, are lacking.

METHODS

Patients underwent a first EP study at baseline and a second one after a loading dose of amiodarone of 14 +/- 2.9 g. According to the results of the second EP study, patients were classified either as responders or non-responders to amiodarone; non-responders were eventually treated with an ICD.

RESULTS

Eighty-four consecutive patients with MI (78 men; 21-77 years old; mean left ventricular (LV) ejection fraction 36 +/- 11%) were consecutively included. Forty-three patients (51%) were responders, and 41 patients (49%) were non-responders to amiodarone therapy. During a mean follow-up period of 63 +/- 30 months, SCD and total mortality rates were significantly higher in the amiodarone-treated patients (p = 0.03 and 0.02, respectively).

CONCLUSIONS

The long-term survival of patients with sustained ventricular tachyarrhythmias after MI, with depressed LV function, is significantly better with an ICD than with amiodarone therapy, even when stratified according to the results of the EP study. These patients should benefit from early ICD placement, and any previous amiodarone treatment seems to have no additional value.

Acute electrophysiologic effects of amiodarone in patients with congestive heart failure

Patients with severe congestive heart failure (CHF) are at increased risk for atrial and ventricular arrhythmias and sudden cardiac death. Amiodarone is generally well tolerated by this population and has a low proarrhythmic potential. Because of its peculiar kinetics, amiodarone requires a prolonged loading period, necessitating lengthy hospitalizations in a monitored setting. This study was planned prospectively to assess the electrophysiologic effects of an abbreviated high-dose oral load of amiodarone in patients with severe CHF and known or suspected life-threatening ventricular arrhythmias. Fifteen patients with stable CHF and known or suspected life-threatening ventricular arrhythmias underwent baseline electrophysiologic study. The study was repeated after administration of oral amiodarone, 50 mg/kg/day for 2 days in 8 divided doses (mean dose 6.9 +/- 0.4 g). After amiodarone administration, there was prolongation in virtually all conduction times and refractory periods. The prolongation of refractoriness was most pronounced in the atrium. Ventricular effective refractory periods demonstrated reverse frequency dependence. We conclude that a brief high-dose oral load of amiodarone is well tolerated by patients with CHF. It has marked and diffuse electrophysiologic actions suggestive of class I and III effects in addition to antiadrenergic and calcium blocking action. These effects are especially pronounced in the atrium.

Sympatholytic action of intravenous amiodarone in the rat heart

BACKGROUND

Amiodarone is a commonly used antiarrhythmic agent with complex pharmacological effects. Although ventricular arrhythmias can be suppressed soon after intravenous amiodarone, the mechanisms responsible for this action are unclear. We studied the effects of acute treatment with amiodarone on the metabolism and release of norepinephrine (NE) in intact rats and in perfused rat hearts.

METHODS AND RESULTS

Experiments were performed in anesthetized rats and in perfused, innervated hearts with amiodarone administered intravascularly. NE release was induced by electrical stimulation of the sympathetic ganglion. Concentrations of NE and its intraneuronal metabolite dihydroxyphenylglycol (DHPG) in hearts, plasma, and coronary venous effluent were measured by high-performance liquid chromatography. Acute administration of amiodarone induced dose-dependent increases in DHPG concentrations in plasma (5 mg/kg, +48%; 15 mg/kg, +84%; and 50 mg/kg, +467%) and in coronary venous effluent (1 mumol/L, +37%; 3 mumol/L, +510%; and 10 mumol/L, +1100%) together with an unchanged basal overflow of NE. In perfused hearts, NE release evoked by nerve stimulation was inhibited by infusion of amiodarone (1 mumol/L, -16%; 3 mumol/L, -24%; and 10 mumol/L, -64%) or by intravenous amiodarone (50 mg/kg) given 1 hour before heart perfusion (-70%), and the extent of this suppression correlated well with levels of DHPG overflow present immediately before nerve stimulation. When given in vitro and in vivo, amiodarone also significantly reduced NE and increased DHPG content in the heart, leading to a raised DHPG/NE ratio. All these effects of amiodarone were similar to those found with reserpine but less potent. In contrast, oral amiodarone produced none of these effects.

CONCLUSIONS

Acute administration of amiodarone in perfused hearts or intact rats induces partial NE depletion in the heart by interfering with vesicular NE storage and enhancing intraneuronal NE metabolism, effects associated with an impaired NE release during sympathetic activation. Oral dosing with amiodarone has no such effect. Further study is required to test whether this novel sympatholytic effect of amiodarone contributes to its antiarrhythmic action after intravenous administration.

Electrophysiologic effects of sotalol and amiodarone in patients with sustained monomorphic ventricular tachycardia

No prospective studies have compared sotalol and amiodarone during electropharmacologic testing. The purpose of this prospective, randomized study was to compare the electrophysiologic effects of sotalol and amiodarone in patients with coronary artery disease and sustained monomorphic ventricular tachycardia (VT). Patients with coronary artery disease and sustained monomorphic VT inducible by programmed stimulation were randomly assigned to receive either sotalol (n = 17) or amiodarone (n = 17). The sotalol dose was titrated to 240 mg twice daily over 7 days. Amiodarone dosing consisted of 600 mg 3 times daily for 10 days. An electrophysiologic test was performed in the baseline state and at the end of the loading regimen. An adequate response was defined as the inability to induce VT or the ability to induce only relatively slow hemodynamically stable VT. During the follow-up electrophysiologic test, 24% of patients taking sotalol and 41% of those taking amiodarone had an adequate response to therapy (p = 0.30). Amiodarone lengthened the mean VT cycle length to a greater degree than sotalol (28% vs 12%, p < 0.01). There were no significant differences in the effects of sotalol and amiodarone on the ventricular effective refractory period. In patients with coronary artery disease, amiodarone and sotalol are similar in efficacy in the treatment of VT as assessed by electropharmacologic testing. The effects of the 2 drugs on ventricular refractoriness are similar, but amiodarone slows VT to a greater extent than sotalol.