Effect of antiarrhythmic therapy on mortality in survivors of myocardial infarction with asymptomatic complex ventricular arrhythmias: Basel Antiarrhythmic Study of Infarct Survival (BASIS)

Sudden Cardiac Death Risk Stratification and Prevention in Chagas Disease: A Non-systematic Review of the Literature

Chagas disease is an important public health problem in Latin America. However, migration and globalisation have resulted in the increased presence of Chagas disease worldwide. Sudden cardiac death is the leading cause of death in people with Chagas disease, most often due to ventricular fibrillation. Although more common in patients with documented ventricular arrhythmias, sudden cardiac death can also be the first manifestation of Chagas disease in patients with no previous symptoms or known heart failure. Major predictors of sudden cardiac death include cardiac arrest, sustained and non-sustained ventricular tachycardia, left ventricular dysfunction, syncope and bradycardia. The authors review the predictors and risk stratification score developed by Rassi et al. for death in Chagas heart disease. They also discuss the evidence for anti-arrhythmic drugs, catheter ablation, ICDs and pacemakers for the prevention of sudden cardiac death in these patients. Given the widespread global burden, understanding the risk stratification and prevention of sudden cardiac death in Chagas disease is of timely concern.

Ventricular Tachycardia with ICD Shocks: When to Medicate and When to Ablate

PURPOSE OF REVIEW

Ventricular tachycardia occurrence in implantable cardioverter defibrillator (ICD) patients may result in shock delivery and is associated with increased morbidity and mortality. In addition, shocks may have deleterious mechanical and psychological effects. Prevention of ventricular tachycardia (VT) recurrence with the use of antiarrhythmic drugs or catheter ablation may be warranted. Antiarrhythmic drugs are limited by incomplete efficacy and an unfavorable adverse effect profile. Catheter ablation can be effective but acute complications and long-term VT recurrence risk necessitating repeat ablation should be recognized. A shared clinical decision process accounting for patients' cardiac status, comorbidities, and goals of care is often required.

RECENT FINDINGS

There are four published randomized trials of catheter ablation for sustained monomorphic VT (SMVT) in the setting of ischemic heart disease; there are no randomized studies for non-ischemic ventricular substrates. The most recent trial is the VANISH trial which randomly allocated patients with ICD, prior infarction, and SMVT despite first-line antiarrhythmic drug therapy to catheter ablation or more aggressive antiarrhythmic drug therapy. During 28 months of follow-up, catheter ablation resulted in a 28% relative risk reduction in the composite endpoint of death, VT storm, and appropriate ICD shock (p = 0.04). In a subgroup analysis, patients having VT despite amiodarone had better outcomes with ablation as compared to increasing amiodarone dose or adding mexiletine. There is evidence for the effectiveness of both catheter ablation and antiarrhythmic drug therapy for patients with myocardial infarction, an implantable defibrillator, and VT. If sotalol is ineffective in suppressing VT, either catheter ablation or initiation of amiodarone is a reasonable option. If VT occurs despite amiodarone therapy, there is evidence that catheter ablation is superior to administration of more aggressive antiarrhythmic drug therapy. Early catheter ablation may be appropriate in some clinical situations such as patients presenting with relatively slow VT below ICD detection, electrical storms, hemodynamically stable VT, or in very selected patients with left ventricular assist devices. The optimal first-line suppressive therapy for VT, after ICD implantation and appropriate programming, remains to be determined. Thus far, there has not been a randomized controlled trial to compare catheter ablation to antiarrhythmic drug therapy as a first-line treatment; the VANISH-2 study has been initiated as a pilot to examine this question.

Treatment of Ventricular Arrhythmias and Use of Implantable Cardioverter-Defibrillators to Improve Survival in Older Adult Patients with Cardiac Disease

Ventricular arrhythmia (VA) and sudden cardiac death (SCD) are well-recognized problems in the overall heart failure population, but treatment decisions can be more complex and nuanced in older patients. Sustained VA does not always lead to SCD, but identifies a higher risk population and may cause significant symptoms. Antiarrhythmic drugs (AAD) and catheter ablation are the mainstays for prevention of VA, but have not been shown to improve mortality. The value of implantable cardiac defibrillators (ICDs) may be influenced by patient age. This article discusses long-term treatment of VA and the use of ICDs in the elderly.

Recognition and Management of Cardiac Arrhythmias: Part II. Ventricular Arrhythmias and Bradyarrhythmias

This review discusses the treatment of ventricular arrhythmias and bradyarrhythmias. Recent studies addressing the management of nonsustained ventricular arrhythmias in patients with congestive heart failure and those recovering from myocardial infarction are discussed. Determination of the origin of wide QRS complex tachycardia is usually possible at the bedside and the diagnostic criteria are provided. Therapy to prevent recurrent ventricular tachycardia or ventricular fibrillation is difficult and controversial. A widely accepted approach based on electrophysiologic testing and implantable defibrillators appears to be the most effective. Recognition and management of common bradyarrhythmias including the indications for pacemakers are discussed.

Medical therapy to prevent recurrence of ventricular arrhythmia in normal and structural heart disease patients

INTRODUCTION

Recurrent ventricular arrhythmias (VA) are a source of significant morbidity in patients without structural heart disease (SHD) and also mortality in patients with SHD. The treatment goals for these two patient populations differ greatly. Areas covered: The secondary prevention of recurrent VA in patients without and with SHD will be reviewed, focusing on clinical data (especially randomized, controlled trials) in the literature as determined through searches in PubMed and ClinicalTrials.gov. This will include β blockers, non-dihydropyridine calcium channel blockers and antiarrhythmic drugs in both subgroups and non-antiarrhythmic medications in SHD. Expert commentary: The available options for medical therapy for VA in both normal hearts and SHD are insufficient, due to substandard efficacy and toxicities. While non-pharmacologic therapies may provide an excellent option, further drug development and randomized trials are needed, as is a reappraisal of the current mode of utilization.

Relationship Between Early and Late Nonsustained Ventricular Tachycardia and Cardiovascular Death in Patients With Acute Coronary Syndrome in the Platelet Inhibition and Patient Outcomes (PLATO) Trial

BACKGROUND

Nonsustained ventricular tachycardia (NSVT) is common after acute coronary syndrome (ACS) and a marker of increased risk of arrhythmogenic death. However, the prognostic significance of NSVT when evaluated with other contemporary risk markers and at later time points after ACS remains uncertain.

METHODS AND RESULTS

In the Platelet Inhibition and Patient Outcomes (PLATO) trial, continuous ECGs were performed during the first 7 days after ACS (n=2866) and repeated for another 7 days at day 30 (n=1991). Median follow-up was 1 year. There was a time-varying interaction between NSVT and cardiovascular death such that NSVT was significantly associated with increased risk within the first 30 days after randomization (22/999 [2.2%] versus 16/1825 [0.9%]; adjusted hazard ratio, 2.84; 95% confidence interval, 1.39-5.79; P=0.004) but not after 30 days (28/929 [3.0%] versus 42/1734 [2.4%]; P=0.71). Detection of NSVT during the convalescent phase (n=428/1991; 21.5%) was also associated with an increased risk of cardiovascular death, and was most marked within the first 2 months after detection (1.9% versus 0.3%; adjusted hazard ratio, 5.48; 95% confidence interval, 1.07-28.20; P=0.01), and then decreasing over time such that the relationship was no longer significant by ≈5 months after ACS.

CONCLUSIONS

NSVT occurred frequently during the acute and convalescent phases of ACS. The risk of cardiovascular death associated with NSVT was the greatest during the first 30 days after presentation; however, patients with NSVT detected during the convalescent phase were also at a significantly increased risk of cardiovascular death that persisted for an additional several months after the index event.

CLINICAL TRIAL REGISTRATION

http://www.clinicaltrials.gov. Unique identifier: NCT00391872.

Amiodarone versus other pharmacological interventions for prevention of sudden cardiac death

BACKGROUND

Sudden cardiac death (SCD) is one of the main causes of cardiac death. There are two main strategies to prevent it: managing cardiovascular risk factors and reducing the risk of ventricular arrhythmias. Implantable cardiac defibrillators (ICDs) constitute the standard therapy for both primary and secondary prevention; however, they are not widely available in settings with limited resources. The antiarrhythmic amiodarone has been proposed as an alternative to ICD.

OBJECTIVES

To evaluate the effectiveness of amiodarone for primary or secondary prevention in SCD compared with placebo or no intervention or any other antiarrhythmic drugs in participants at high risk (primary prevention) or who have recovered from a cardiac arrest or a syncope due to Ventricular Tachycardia/Ventricular Fibrillation, or VT/VF (secondary prevention).

SEARCH METHODS

We searched the Cochrane Central Register of Controlled Trials (CENTRAL), MEDLINE (OVID), EMBASE (OVID), CINAHL (EBSCO) and LILACS on 26 March 2015. We reviewed reference lists of included studies and selected reviews on the topic, contacted authors of included studies, screened relevant meetings and searched in registers for ongoing trials. We applied no language restrictions.

SELECTION CRITERIA

Randomised and quasi-randomised trials assessing the efficacy of amiodarone versus placebo, no intervention, or other antiarrhythmics in adults. For primary prevention we considered participants at high risk for SCD. For secondary prevention we considered participants recovered from cardiac arrest or syncope due to ventricular arrhythmias.

DATA COLLECTION AND ANALYSIS

Two authors independently assessed the trials for inclusion and extracted relevant data. We contacted trial authors for missing data. We performed meta-analyses using a random-effects model. We calculated risk ratios (RR) for dichotomous outcomes with 95% confidence intervals (CIs). Three studies included more than one comparison.

MAIN RESULTS

We included 24 studies (9,997 participants). Seventeen studies evaluated amiodarone for primary prevention and six for secondary prevention. Only three studies used an ICD concomitantly with amiodarone for the comparison (all of them for secondary prevention).For primary prevention, amiodarone compared to placebo or no intervention (17 studies, 8383 participants) reduced SCD (RR 0.76; 95% CI 0.66 to 0.88), cardiac mortality (RR 0.86; 95% CI 0.77 to 0.96) and all-cause mortality (RR 0.88; 95% CI 0.78 to 1.00). The quality of the evidence was low.Compared to other antiarrhythmics (three studies, 540 participants), amiodarone reduced SCD (RR 0.44; 95% CI 0.19 to 1.00), cardiac mortality (RR 0.41; 95% CI 0.20 to 0.86) and all-cause mortality (RR 0.37; 95% CI 0.18 to 0.76). The quality of the evidence was moderate.For secondary prevention, amiodarone compared to placebo or no intervention (two studies, 440 participants) appeared to increase the risk of SCD (RR 4.32; 95% CI 0.87 to 21.49) and all-cause mortality (RR 3.05; 1.33 to 7.01). However, the quality of the evidence was very low. Compared to other antiarrhythmics (four studies, 839 participants) amiodarone appeared to increase the risk of SCD (RR 1.40; 95% CI 0.56 to 3.52; very low quality of evidence), but there was no effect in all-cause mortality (RR 1.03; 95% CI 0.75 to 1.42; low quality evidence).Amiodarone was associated with an increase in pulmonary and thyroid adverse events.

AUTHORS' CONCLUSIONS

There is low to moderate quality evidence that amiodarone reduces SCD, cardiac and all-cause mortality when compared to placebo or no intervention for primary prevention, and its effects are superior to other antiarrhythmics.It is uncertain if amiodarone reduces or increases SCD and mortality for secondary prevention because the quality of the evidence was very low.

Implantable defibrillators versus medical therapy for cardiac channelopathies

BACKGROUND

Sudden cardiac death is a significant cause of mortality in both the US and globally. However, 5% to 15% of people with sudden cardiac death have no structural abnormalities, and most of these events are attributed to underlying cardiac ion channelopathies. Rates of cardiac ion channelopathy diagnosis are increasing. However, the optimal treatment for such people is poorly understood and current guidelines rely primarily on expert opinion.

OBJECTIVES

To compare the effect of implantable cardioverter defibrillators (ICD) with antiarrhythmic drugs or usual care in reducing the risk of all-cause mortality, fatal and non-fatal cardiovascular events, and adverse events in people with cardiac ion channelopathies.

SEARCH METHODS

We searched the Cochrane Central Register of Controlled Trials (CENTRAL, 2015, Issue 6), EMBASE, MEDLINE, Conference Proceedings Citation Index - Science (CPCI-S), ClinicalTrials.gov, and the World Health Organization (WHO) International Clinical Trials Registry Platform (ICTRP) in July 2015. We applied no language restrictions.

SELECTION CRITERIA

We included all randomized controlled trials of people aged 18 years and older with ion channelopathies, including congenital long QT syndrome, congenital short QT syndrome, Brugada syndrome, or catecholaminergic polymorphic ventricular tachycardia. Participants must have been randomized to ICD implantation and compared to antiarrhythmic drug therapy or usual care.

DATA COLLECTION AND ANALYSIS

Two authors independently selected studies for inclusion and extracted the data. We included all-cause mortality, fatal and non-fatal cardiovascular events, and adverse events for our primary outcome analyses and non-fatal cardiovascular events, rates of inappropriate ICD firing, quality of life, and cost for our secondary outcome analyses. We calculated risk ratios (RR) and associated 95% confidence intervals (CIs) for dichotomous outcomes, both for independent and pooled study analyses.

MAIN RESULTS

From the 468 references identified after removing duplicates, we found two trials comprising 86 participants that met our inclusion criteria. Both trials included participants with Brugada syndrome who were randomized to ICD versus β-blocker therapy for secondary prevention for sudden cardiac death. Both studies were small, were performed by the same investigators, and exhibited a high risk of bias across multiple domains. In the group randomized to ICD therapy, there was a nine-fold lower risk of mortality compared with people randomized to medical therapy (0% with ICD versus 18% with medical therapy; RR 0.11, 95% CI 0.01 to 0.83; 2 trials, 86 participants). There was low quality evidence of a difference in the rates of combined fatal and non-fatal cardiovascular events, and the results were imprecise (26% with ICD versus 18% with medical therapy; RR 1.49, 95% CI 0.66 to 3.34; 2 trials, 86 participants). The rates of adverse events were higher in the ICD group, but these results were imprecise (28% with ICD versus 10% with medical therapy; RR 2.44, 95% CI 0.92 to 6.44; 2 trials, 86 participants). For secondary outcomes, the risk of non-fatal cardiovascular events was higher in the ICD group, but these results were imprecise and were driven entirely by appropriate ICD-termination of cardiac arrhythmias (26% with ICD versus 0% with medical therapy; RR 11.4, 95% CI 1.57 to 83.3; 2 trials, 86 participants). Approximately 25% of the ICD group experienced inappropriate ICD firing, all of which was corrected by device reprogramming. No data were available for quality of life or cost. We considered the quality of evidence low using the GRADE methodology, due to study limitations and imprecision of effects.

AUTHORS' CONCLUSIONS

Among people with Brugada syndrome who have survived a prior episode of sudden cardiac death, ICD therapy appeared to reduce mortality when compared to β-blocker therapy, but the true magnitude may be substantially different from the estimate of the effect because of study limitations and imprecision. Due to the large magnitude of effect, it is unlikely that there will be additional studies evaluating the role of ICDs for secondary prevention in this population. Further studies are necessary to determine the optimal treatment, if any, to prevent an initial episode of sudden cardiac death in people with cardiac ion channelopathies.

Clinical management and prevention of sudden cardiac death

Despite the revolutionary advancements in the past 3 decades in the treatment of ventricular tachyarrhythmias with device-based therapy, sudden cardiac death (SCD) remains an enormous public health burden. Survivors of SCD are generally at high risk for recurrent events. The clinical management of such patients requires a multidisciplinary approach from postresuscitative care to a thorough cardiovascular investigation in an attempt to identify the underlying substrate, with potential to eliminate or modify the triggers through catheter ablation and ultimately an implantable cardioverter-defibrillator (ICD) for prompt treatment of recurrences in those at risk. Early recognition of low left ventricular ejection fraction as a strong predictor of death and association of ventricular arrhythmias with sudden death led to significant investigation with antiarrhythmic drugs. The lack of efficacy and the proarrhythmic effects of drugs catalyzed the development and investigation of the ICD through several major clinical trials that proved the efficacy of ICD as a bedrock tool to detect and promptly treat life-threatening arrhythmias. The ICD therapy is routinely used for primary prevention of SCD in patients with cardiomyopathy and high risk inherited arrhythmic conditions and secondary prevention in survivors of sudden cardiac arrest. This compendium will review the clinical management of those surviving SCD and discuss landmark studies of antiarrhythmic drugs, ICD, and cardiac resynchronization therapy in the primary and secondary prevention of SCD.

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.

Management of ventricular tachycardia in heart failure

Ventricular tachyarrhythmias are common in patients with congestive heart failure. The clinical presentation ranges from an asymptomatic incidental electrocardiographic finding to palpitations, syncope, and sudden cardiac death. Although implantable cardioverter defibrillators successfully prevent sudden cardiac death associated with ventricular fibrillation and ventricular tachycardia, recurrent implantable cardioverter defibrillators shocks remain a clinical management challenge. In this review, we discuss management strategies of ventricular tachycardia in congestive heart failure, including drug therapy, radiofrequency catheter ablation (RFCA), and recent RFCA advances.

Neurohormonal, structural, and functional recovery pattern after premature ventricular complex ablation is independent of structural heart disease status in patients with depressed left ventricular ejection fraction: a prospective multicenter study

OBJECTIVES

This study aimed to assess the benefit after ablation of premature ventricular complexes (PVC) in patients with frequent PVC and left ventricular (LV) dysfunction, regardless of previous structural heart disease (SHD) diagnosis, PVC morphology, or estimated site of origin.

BACKGROUND

Ablation of PVC in patients with LV dysfunction is usually restricted to patients with suspected PVC-induced cardiomyopathy.

METHODS

Consecutive patients with frequent PVC and LV dysfunction accepted for ablation at 4 centers were prospectively included. Of the 80 patients included, 27 (34%) had a diagnosis of SHD.

RESULTS

Successful sustained ablation (SSA) was achieved in 53 (66%) patients, and LVEF improved in these patients from 33.7 ± 8% to 43.8 ± 9.4% and 45.8 ± 10.9% at 6 and 12 months, respectively (p < 0.05), without differences related to previous diagnosis of SHD (p = 0.69). BNP decreased from 109 [64 to 242] pg/ml to 60 [25 to 170] pg/ml, 50 [14 to 130] pg/ml, and 60 [19 to 81] pg/ml at 1, 6, and 12 months (p < 0.05). Patients in NYHA class I increased from 12 (23%) to 42 (79%) at 12 months (p < 0.05). A 13% baseline PVC burden had 100% sensitivity and 85% specificity to predict an absolute increase ≥ 5% in LVEF after SSA. Although 20 patients with >13% PVC and SSA had class I indication for cardioverter defibrillator implantation, these indications were absent at 6 months post-ablation.

CONCLUSIONS

Independently of the presence of SHD, the SSA of frequent PVC in patients with depressed LVEF induced a progressive clinical and functional improvement. Improvement in heart failure parameters was related to baseline PVC burden and persistence of ablation success.

Examining the safety of amiodarone

INTRODUCTION

Amiodarone is the most widely used antiarrhythmic agent, with demonstrated effectiveness against all the spectrum of cardiac tachyarrhythmias. The risk of adverse effects acts as a limiting factor to its utilization especially in the long term. This article systematically reviews the published evidence on amiodarone versus placebo to examine its safety as an antiarrhythmic drug.

AREAS COVERED

Authors collected data on adverse effects reported in 49 randomized placebo-controlled trials with amiodarone. Adverse effects were classified according to the organ/system involved. Pooled estimates of the number needed to treat (NNT) and to harm (NNH) versus placebo were calculated.

EXPERT OPINION

Amiodarone is effective for both the acute conversion of atrial fibrillation (AF) (11 trials, NNT = 4 at 24 h; p = 0.003) and the prevention of postoperative AF (18 trials, NNT = 8; p < 0.001), although with an increased risk of bradycardia, hypotension, nausea or phlebitis (pooled NNH = 4; p < 0.001). Amiodarone administration for the maintenance of sinus rhythm has a favorable net clinical benefit (pooled NNT = 3; p < 0.001 versus pooled NNH for either thyroid toxicity, gastrointestinal discomfort, skin toxicity or eye toxicity = 11; p < 0.001). Treatment with amiodarone for the prophylaxis of sudden cardiac death has less favorable net clinical benefit (15 trials, NNT = 38; p < 0.001 versus NNH for either thyroid toxicity, hepatic toxicity, pulmonary toxicity or bradycardia = 14; p < 0.001). Amiodarone treatment in this setting should be used in only selected cases.

Acute Antiarrhythmic Therapy of Ventricular Tachycardia and Ventricular Fibrillation

Ventricular arrhythmias (ventricular tachycardia and ventricular fibrillation) are often associated with underlying structural heart disease and require prompt assessment and treatment. Acute treatment involves initial hemodynamic stabilization of the patient followed by suppressive treatment with pharmacologic and nonpharmacologic approaches for reducing the risk of recurrence of ventricular arrhythmias and potential development of sudden cardiac death. This article reviews acute antiarrhythmic drug therapy for ventricular arrhythmias based on the clinical presentation.

Drug-induced arrhythmias

The objective of this review is to characterize the mechanisms, risk factors, and offending pharmacotherapeutic agents that may cause drug-induced arrhythmias in critically ill patients. PubMed, other databases, and citation review were used to identify relevant published literature. The authors independently selected studies based on relevance to the topic. Numerous drugs have the potential to cause drug-induced arrhythmias. Drugs commonly administered to critically ill patients are capable of precipitating arrhythmias and include antiarrhythmics, antianginals, antiemetics, gastrointestinal stimulants, antibacterials, narcotics, antipsychotics, inotropes, digoxin, anesthetic agents, bronchodilators, and drugs that cause electrolyte imbalances and bradyarrhythmias. Drug-induced arrhythmias are insidious but prevalent. Critically ill patients frequently experience drug-induced arrhythmias; however, enhanced appreciation for this adverse event has the potential to improve prevention, treatment, patient safety, and outcomes in this patient population.

Relationship between nonsustained ventricular tachycardia after non-ST-elevation acute coronary syndrome and sudden cardiac death: observations from the metabolic efficiency with ranolazine for less ischemia in non-ST-elevation acute coronary syndrome-thrombolysis in myocardial infarction 36 (MERLIN-TIMI 36) randomized controlled trial

BACKGROUND

Most studies examining the relationship between ventricular tachycardia (VT) after acute coronary syndrome and sudden cardiac death (SCD) were performed before widespread use of reperfusion, revascularization, or contemporary medical therapy and were limited to ST-elevation myocardial infarction. The incidence and prognostic implications of VT in patients with non-ST-elevation acute coronary syndrome receiving contemporary care have not been examined.

METHODS AND RESULTS

The Metabolic Efficiency With Ranolazine for Less Ischemia in Non-ST-Elevation Acute Coronary Syndrome-Thrombolysis in Myocardial Infarction 36 (MERLIN-TIMI 36) trial randomized 6560 patients hospitalized with a non-ST-elevation acute coronary syndrome to ranolazine or placebo in addition to standard therapy. Continuous ECG recording was performed for the first 7 days after randomization and evaluated in a blinded core laboratory. SCD (n=121) was assessed over a median follow-up of 1 year. A total of 6345 patients (97%) had continuous ECG recordings evaluable for analysis. Compared with patients with no VT (n=2764), there was no increased risk of SCD in patients with only ventricular triplets (n=1978, 31.2%) (1.4% versus 1.2%); however, the risk of SCD was significantly greater in patients with VT lasting 4 to 7 beats (n=1172, 18.5%) (SCD, 2.9%; adjusted hazard ratio, 2.3; P<0.001) and in patients with VT lasting at least 8 beats (n=431, 6.8%) (SCD, 4.3%; adjusted hazard ratio, 2.8; P=0.001). This effect was independent of baseline characteristics and ejection fraction. VT occurring within the first 48 hours after admission was not associated with SCD.

CONCLUSIONS

Nonsustained VT is common after admission for non-ST-elevation acute coronary syndrome, and even short episodes of VT lasting 4 to 7 beats are independently associated with the risk of SCD over the subsequent year. Clinical Trial Registration- URL: http://www.clinicaltrials.gov. Unique identifier: NCT00099788.

Amiodarone: what have we learned from clinical trials?

Amiodarone is an antiarrhythmic agent commonly used in the treatment of supraventricular and ventricular tachyarrhythmias. This paper reviews clinical trials in which amiodarone was used in one of the treatment arms. Key post-myocardial infarction trials include EMIAT and CAMIAT, both of which demonstrated that amiodarone reduced arrhythmic but not overall mortality. In patients with congestive heart failure (CHF), amiodarone was associated with a neutral survival in CHF/STAT and improvement in survival in GESICA. In patients with nonsustained ventricular tachycardia, the MADIT trial demonstrated that therapy with an implantable cardioverter-defibrillator (ICD) improved survival compared with the antiarrhythmic drug arm in such patients, most of whom were taking amiodarone. In sustained VT/VF patients, the CASCADE trial demonstrated that empiric amiodarone lowered arrhythmic recurrence rates compared with other drugs guided by serial Holter or electrophysiologic studies. Several trials including AVID, CIDS, and CASH have demonstrated the superiority of ICD therapy compared with empiric amiodarone in improving overall survival. Clinical implications of these trials are discussed.

Amiodarone inhibits arterial thrombus formation and tissue factor translation

BACKGROUND

In patients with coronary artery disease and reduced ejection fraction, amiodarone reduces mortality by decreasing sudden death. Because the latter may be triggered by coronary artery thrombosis as much as ventricular arrhythmias, amiodarone might interfere with tissue factor (TF) expression and thrombus formation.

METHODS AND RESULTS

Clinically relevant plasma concentrations of amiodarone reduced TF activity and impaired carotid artery thrombus formation in a mouse photochemical injury model in vivo. PTT, aPTT, and tail bleeding time were not affected; platelet number was slightly decreased. In human endothelial and vascular smooth muscle cells, amiodarone inhibited tumor necrosis factor (TNF)-alpha and thrombin-induced TF expression as well as surface activity. Amiodarone lacking iodine and the main metabolite of amiodarone, N-monodesethylamiodarone, inhibited TF expression. Amiodarone did not affect mitogen-activated protein kinase activation, TF mRNA expression, and TF protein degradation. Metabolic labeling confirmed that amiodarone inhibited TF protein translation.

CONCLUSIONS

Amiodarone impairs thrombus formation in vivo; in line with this, it inhibits TF protein expression and surface activity in human vascular cells. These pleiotropic actions occur within the range of amiodarone concentrations measured in patients, and thus may account at least in part for its beneficial effects in patients with coronary artery disease.

The role of antiarrhythmic drug therapy for the prevention of sudden cardiac death

Sudden cardiac death (SCD) accounts for more than 300,000 deaths annually in the United States alone. The utility of antiarrhythmic drugs in survivors of SCD (secondary prevention) is limited because of their incomplete efficacy and long-term toxicity. Efforts to target primary prevention of SCD have focused on left ventricular dysfunction in conjunction with congestive heart failure. Antiarrhythmic drugs are not able to decrease mortality in this patient population either; in fact, certain drugs may actually increase overall mortality. In both primary and secondary prevention patients, only implantable cardioverter-defibrillator implantation is associated with improved survival. Antiarrhythmic drugs like azimilide, dofetilide, sotalol, and amiodarone can be used as adjunct treatment for management of atrial arrhythmias and to decrease implantable cardioverter-defibrillator shocks. There is an unmet need for more effective and less toxic antiarrhythmic medications.

Amiodarone use after acute myocardial infarction complicated by heart failure and/or left ventricular dysfunction may be associated with excess mortality

BACKGROUND

We sought to assess the association of amiodarone use with mortality during consecutive periods in patients with post-acute myocardial infarction with left ventricular systolic dysfunction and/or HF treated with a contemporary medical regimen.

METHODS

This study used data from VALIANT, a randomized comparison of valsartan, captopril, or both in patients with acute myocardial infarction with HF and/or left ventricular systolic dysfunction. We compared baseline characteristics of 825 patients treated with amiodarone at randomization with 13,875 patients not treated with amiodarone. Using Cox models, we examined the association of amiodarone use with subsequent mortality during consecutive periods after randomization (days 1-16, 17-45, 46-198, and 199-1096).

RESULTS

Patients treated with amiodarone were older, had higher Killip class, and were more likely to have a history of diabetes mellitus and hypertension. Adjusting for baseline predictors of mortality, we found that amiodarone use was associated with a significant increase in mortality during 3 of the 4 periods: hazard ratio 1.5, 95% CI (1.1-2.0), P = .02, for days 1 to 16; 2.1 (1.5-2.9), P < .001, for days 17 to 45; 1.1 (0.83-1.46), P = .51, for days 46 to 198; and 1.4 (1.2-1.6), P < .001, for days 199 to 1096.

CONCLUSION

In this study, amiodarone use was associated with excess early and late all-cause and cardiovascular mortality. These observational findings are in contrast to earlier randomized trials of amiodarone and need to be validated prospectively.

Serum amiodarone and desethylamiodarone concentrations following nasogastric versus oral administration

OBJECTIVE

Hospitalized patients unable to ingest anything by mouth require nutritional support by enteral feeding and administration of drugs through a nasogastric tube inserted into the digestive tract. Nasogastric administration of amiodarone may not always be equivalent to oral administration of amiodarone.

METHODS

We collected 162 observations of serum amiodarone and desethylamiodarone metabolite concentrations from 93 patients within 60 days of starting treatment with amiodarone. Eight patients were given the drug nasogastrically and 85 patients, orally. The two groups, were compared in terms of their serum concentration/(dose/weight) (C/D) value. A ratio of serum amiodarone concentration to serum desethylamiodarone concentration (AMD/DEA) was calculated for each sample. In addition, the percentage drug recovery after nasogastric administration of amiodarone was analysed.

RESULTS

Significant differences were observed in C/D values of amiodarone and desethylamiodarone and in AMD/DEA values of patients given amiodarone orally when compared with those given the drug nasogastrically. The C/D values of patients who received their medication nasogastrically were approximately 30% of the C/D values of patients who received their medication orally. Approximately 70% of the drug was recovered after it had passed through the nasogastric tube.

CONCLUSIONS

To achieve similar concentrations, an approximately 3-fold increase in dosage of amiodarone was required when patients were given the drug nasogastrically rather than orally. This suggests that the absorption of amiodarone following nasogastric administration is poor when compared with oral administration. Therapeutic drug monitoring is necessary to optimize dose particularly during the early stages of amiodarone therapy.

Pro-arrhythmic effects of amiodarone and concomitant rate-control medication

AIMS

Amiodarone is one of the most efficient and safe antiarrhythmic drugs in the treatment of atrial fibrillation (AF). Although pro-arrhythmic effects of amiodarone therapy are rare, the aim of the present study was to identify clinical constellations which may lead to amiodarone-associated pro-arrhythmia.

METHODS AND RESULTS

Sixty-three consecutive patients (pts) (49 males; 64+/-10.3 years; 35 with coronary heart disease, 17 with lone AF) were retrospectively included in this study. All received an oral (92.1%) or i.v. (7.9%) loading dose of amiodarone for the treatment of AF. Cardiac diseases, concomitant medical treatment, and incidence of pro-arrhythmic effects were analysed. Three pts (4.8% of the total population) developed a clinical relevant, polymorphic ventricular tachyarrhythmia, 3-48 h after initiation of amiodarone loading. Coronary heart disease was present in all of these pts, and in two of them left ventricular ejection fraction was severely reduced. The mean QTc in these pts was only slightly prolonged; mean heart rate was significantly decreased compared with the total study population (61.0+/-7.5 vs. 74.5+/-24.1 bpm; P < or = 0.05). In all pts with pro-arrhythmia, amiodarone (two pts i.v., one patient oral) was initiated during concomitant beta-blocker/digitalis therapy. Twenty-five per cent of the patients receiving this 'triple' therapy developed ventricular arrhythmia.

CONCLUSION

The present study implies that initiation of amiodarone therapy in pts with structural heart disease and AF that are concomitantly treated with beta-blockers and digitalis may have an increased risk of amiodarone-associated pro-arrhythmia.

Determinants of Recurrent Ventricular Arrhythmia or Death in 300 Consecutive Patients with Ischemic Heart Disease Who Experienced Aborted Sudden Death: Data from the Leiden Out-of-Hospital Cardiac Arrest Study

OBJECTIVE

Evaluation of the relation between clinical characteristics and incidence of recurrent ventricular arrhythmias (VAs) or death during long-term follow-up in a cohort of 300 consecutive ischemic heart disease (IHD) patients who had survived an episode of sudden cardiac arrest (SCA).

BACKGROUND

Survivors of life-threatening VA are at high risk for recurrent events.

METHODS

A total of 300 consecutive survivors of SCA with IHD were included in a standardized screening and evaluation protocol. Multivariable Cox regression analysis was performed to determine the relation between clinical variables at baseline and the incidence of recurrent VA, all-cause mortality and the composite of both (composite endpoint).

RESULTS

The presenting arrhythmia was VT in 156 (52%) patients and VF in 144 (48%) patients. Revascularization was performed in 78 (26%) patients and an ICD was implanted in 216 (72%) patients. During follow-up (mean 30 +/- 21 months) 37 (12%) patients died and 88 (29%) patients experienced a recurrence. Advanced age (adjusted hazard ratio (HR) 2.0; 1.2-3.3), history of heart failure (HR 1.8; 1.2-2.6), and amiodarone use (HR 3.1; 2.1-4.6) were independent predictors for the composite endpoint. VT as presenting arrhythmia was an independent predictor for all-cause mortality only (HR 2.4; 1.2-4.8). A decreased risk of recurrences was determined by beta-blocker use (HR 0.5; 0.4-0.8) and coronary revascularization (HR 0.3; 0.2-0.6).

CONCLUSION

In a cohort of 300 consecutive survivors of SCA the incidence of recurrent VA and death is dependent on patient age, history of heart failure, and use of amiodarone. In contrast, use of beta-blockers and aggressive coronary revascularization improve the outcome.

Device based treatment of heart failure

As the population ages and survival from ischaemic heart disease improves, the incidence and prevalence of congestive cardiac failure has increased dramatically. Medical treatments including ACE inhibitors, beta blockers, and aldosterone antagonists have improved the outlook for most patients. However, despite optimal medical treatment there is a significant group of patients who continue to suffer poor morbidity and mortality. Device based treatment consisting of implantable cardioverter defibrillators (ICD) and cardiac resynchronisation therapy (CRT) devices offer new modes of treatment to patients with symptomatic heart failure despite optimal medical therapy. ICDs have been shown to reduce mortality in patients with severe heart failure while CRT leads to an improvement in functional class, quality of life scores, physiological measures such as peak Vo(2), and reduce hospitalisations. Combination devices, which provide both ICD and CRT functions, have now been seen to provide synergistic benefits in selected patients.

Acute cardiodepressant effects induced by bolus intravenous administration of amiodarone in rabbits

Amiodarone is a potent anti-arrhythmic with a large pharmacological spectrum that shares the mechanisms of action of all classes of anti-arrhythmic drugs. Originally used in the treatment of supraventricular arrhythmias, it has also been used to treat ventricular tachyarrhythmias. The recent inclusion of amiodarone in the Advanced Cardiac Life Support protocols warrants the characterization of the hemodynamic profile resulting from the rapid venous administration of the drug. Thus, the main purpose of the present study was to investigate the acute hemodynamic profile resulting from the bolus i.v. injection of amiodarone, compared with bolus i.v. administration of lidocaine. We investigated the acute hemodynamic effects of amiodarone and lidocaine, in an experimental model of open-chest pentobarbital-anesthetized rabbits (n = 24). Amiodarone (5 mg/kg) induced immediate reductions in mean arterial pressure (MAP) of 32 +/- 5% (P < 0.001), accompanied by reductions in cardiac contractility and relaxation, as assessed by left ventricular (LV) +dP/dt(max) and -dP/dt(max) (40 +/- 4 and 36 +/- 4% respectively) (P < 0.001), heart rate (HR) 10 +/- 1% (P < 0.05), cardiac output (CO) 24 +/- 5% (P < 0.001) and systemic vascular resistance (SVR) 19 +/- 3.5% (P < 0.05). Lidocaine (3 mg/kg) induced reductions in: MAP of 18 +/- 7% (P < 0.001), LV +dP/dt(max) and -dP/dt(max) (40 +/- 5 and 22 +/- 7% respectively) (P < 0.001), HR 7 +/- 1% (P < 0.01) and CO of 23 +/- 6% (P < 0.001). SVR increased by 9 +/- 1.5% (P > 0.05). It is concluded that rapid i.v. administration of both amiodarone and lidocaine induces significant cardiovascular depression mainly characterized by immediate reductions in cardiac contractility.

A benefit–risk assessment of class III antiarrhythmic agents

The prevalence of arrhythmia in the population is increasing as more people survive for longer with cardiovascular disease. It was once thought that antiarrhythmic therapy could save life, however, it is now evident that antiarrhythmic therapy should be administrated with the purpose of symptomatic relief. Since many patients experience a decrease in physical performance as well as a diminished quality of life during arrhythmia there is still a need for antiarrhythmic drug therapy. The development of new antiarrhythmic agents has changed the focus from class I to class III agents since it became evident that with class I drug therapy the prevalence of mortality is considerably higher. This review focuses on the benefits and risks of known and newer class III antiarrhythmic agents. The benefits discussed include the ability to maintain sinus rhythm in persistent atrial fibrillation patients, and reducing the need for implantable cardioverter defibrillator shock/antitachycardia therapy, since no class III antiarrhythmic agents have proven survival benefit. The risks discussed mainly focus on pro-arrhythmia as torsade de pointes ventricular tachycardia.

Effects of amiodarone on mutant Na+/Ca2+ exchangers expressed in CCL 39 cells

Using the whole cell voltage clamp, we reported previously that amiodarone acutely inhibits Na+/Ca2+ exchange current (INCX) in guinea pig cardiac ventricular myocytes. Intracellular application of trypsin via the patch pipette attenuated the blocking effect of amiodarone, suggesting that amiodarone affects the Na+/Ca2+ exchanger (NCX) from the cytoplasmic side. Here, we attempted to detect the site of amiodarone inhibition using wild type NCX1, mutants, and NCX3 expressed in CCL39 fibroblasts. INCX was recorded by ramp pulses. Amiodarone at 30 microM inhibited INCX by 80% in cells expressing wild type NCX1. However, 30 microM amiodarone inhibited INCX by about 55% in cells expressing mutant NCX1 with amino acids 217-671 (DeltaXIP) or 247-671 (Delta247-671) deleted in the long intracellular loop between the transmembrane segments (TM) 5 and 6. INCXs from NCX mutants deleted of cytoplasmic TM1-2, TM3-4 or the C-terminus were inhibited by amiodarone to a similar extent as the wild type. Amiodarone also inhibited INCX of NCX3 by 76%. These results suggest that a long intracellular loop may be involved in the inhibition of NCX1 by amiodarone, but that other intracellular loops, XIP region or C terminus are not involved in the amiodarone inhibition of NCX1.

Disruption of hepatic lipid homeostasis in mice after amiodarone treatment is associated with peroxisome proliferator-activated receptor-alpha target gene activation

Amiodarone, an efficacious and widely used antiarrhythmic agent, has been reported to cause hepatotoxicity in some patients. To gain insight into the mechanism of this unwanted effect, mice were administered various doses of amiodarone and examined for changes in hepatic histology and gene regulation. Amiodarone induced hepatomegaly, hepatocyte microvesicular lipid accumulation, and a significant decrease in serum triglycerides and glucose. Northern blot analysis of hepatic RNA revealed a dose-dependent increase in the expression of a number of genes critical for fatty acid oxidation, lipoprotein assembly, and lipid transport. Many of these genes are regulated by the peroxisome proliferator-activated receptor-alpha (PPARalpha), a ligand-activated nuclear hormone receptor transcription factor. The absence of induction of these genes as well as hepatomegaly in PPARalpha knockout [PPARalpha-/-] mice indicated that the effects of amiodarone were dependent upon the presence of a functional PPARalpha gene. Compared to wild-type mice, treatment of PPARalpha-/- mice with amiodarone resulted in an increased rate and extent of total body weight loss. The inability of amiodarone to directly activate either human or mouse PPARalpha transiently expressed in human HepG2 hepatoma cells indicates that the effects of amiodarone on the function of this receptor were indirect. Based upon these results, we conclude that amiodarone disrupts hepatic lipid homeostasis and that the increased expression of PPARalpha target genes is secondary to this toxic effect. These results provide important new mechanistic information regarding the hepatotoxic effects of amiodarone and indicate that PPARalpha protects against amiodarone-induced hepatotoxicity.

Diminishing proportional risk of sudden death with advancing age: implications for prevention of sudden death

BACKGROUND

Advances in primary and secondary prevention of sudden death have led to a wide array of potentially beneficial therapies. Identification of patients most likely to benefit would be of use when considering costly interventions such as an implantable defibrillator. We sought to determine the effect of advancing age on the mode of death in the Amiodarone Trialists Metanalysis.

METHODS AND RESULTS

Patients (n = 6252; age, 61.2+/-10.5 years; 83% men) were included in an analysis of predictors of sudden death (SD) and all-cause death (ACD), based on baseline variables at enrollment. Patients were divided into 5 age groups: < or =50 years, 51 to 60 years, 61 to 70 years, 71 to 80 years, and >80 years. During a mean of 16.8+/-10.3 months of follow-up, there were 1023 deaths, with an annual overall mortality rate of 11.7%. Both sudden death and nonsudden death rates increased with age, although the increase of nonsudden death with age was more dramatic. The overall proportion of death that was sudden (SD/ACD ratio) was 0.41, falling from 0.51 before age 50 years to 0.26 after age 80 years (P =.002 for trend). The SD/ACD ratio was not affected by sex, New York Heart Association Class, or left ventricular ejection fraction.

CONCLUSIONS

Although the incidence of sudden death increases with age, the proportion of death that is sudden diminishes markedly. This finding may influence the yield of interventions targeted at prevention of sudden death.

Indications for an implantable cardioverter defibrillator (ICD)

Since the first clinical use of implantable defibrillator in human, the technology and the function of implantable cardioverter-defibrillator (ICD) have been much improved and now, ICD can be implanted within the chest wall. ICD is the most reliable therapy to prevent sudden cardiac death (SCD) in patients with documented VT/VF and the efficacy is most clear in patients with depressed heart function. It is now extended as a tool of the primary prevention of SCD in high risk patients after myocardial infarction. However, such beneficial effect is not applicable to DCM though patients might have depressed heart function. ICD is not free from procedure- or device-related problems which need to be resolved. From unknown causes, VT/VF might recur in an incessant form and an emergency admission is needed. Therefore, even during ICD therapy, patients often require antiarrhythmic drugs or catheter ablation.