Interaction of ischaemia and encainide/flecainide treatment: a proposed mechanism for the increased mortality in CAST I

Prevalence and incidence of arrhythmias and sudden death in heart failure

Patients with heart failure are prone to a variety of arrhythmias, symptomatic and asymptomatic, that are prognostically significant and have an important bearing on the management of these patients. However there are some inherent problems in assessing the frequency of these arrhythmias within a large patient population, due to a lack of uniformity in defining heart failure and the transient nature of these rhythms. Patients with heart failure commonly die suddenly. The causes of these deaths are difficult to ascertain accurately and are often presumed arrhythmic. With the advent of effective interventions to prevent sudden death, accurately defining the causal relationship between the arrhythmias and sudden death has assumed great importance to appropriately target therapy. Several attempts have been made to predict such deaths on the basis of non-invasive and invasive diagnostic investigations with variable success. In this article we review the incidence and prevalence of atrial and ventricular arrhythmias and sudden deaths in epidemiological studies, surveys and randomised control trials of patients with heart failure. We discuss the prognostic significance of these arrhythmias, the inherent problems in their diagnosis and whether their presence predicts the risk of sudden deaths and the mode of such deaths in the heart failure population. The role of various investigations in risk stratification of sudden death has also been discussed.

Limited antifibrillatory effectiveness of clinically relevant concentrations of class I antiarrhythmics in isolated perfused rat hearts

The Langendorff-perfused rat heart with regional ischemia is increasingly used for evaluating drugs for prevention of phase-1, ischemia-induced ventricular fibrillation (VF). Surprisingly, the effectiveness of Class I antiarrhythmics has not been characterized in this model. One lower and one higher concentration of quinidine (0.79 and 7.90 microM), lidocaine (3.88 and 12.93 microM), and flecainide (0.74 and 1.48 microM), representing the peak unbound plasma and total blood concentrations, respectively, at "therapeutic" dosage, were evaluated. The left main coronary artery was occluded for 30 min to elicit phase-1 VF, after which reperfusion-induced VF was examined. In hearts perfused with Krebs' solution containing 3 mM K(+), the higher concentrations of quinidine and lidocaine reduced the incidence of phase-1 VF from 92% to 0% and 17% respectively, (each p < 0.05). The lower drug concentrations were ineffective. Flecainide was equi-effective at low and high concentrations, with VF incidence reduced from 92% to 17% (p < 0.05). Neither low nor high concentrations of any of the drugs affected the incidence of reperfusion-induced VF. Using hearts perfused with Krebs' containing 5 mM K(+), sufficient to substantially reduce control phase-1 VF incidence, the experiment was repeated to test for possible proarrhythmic activity. None of the three drugs increased arrhythmia incidence. In this model, it was not possible to suppress ischemia-induced and reperfusion-induced VF with flecainide, lidocaine, or quinidine at concentrations equivalent to peak unbound plasma levels after clinical administration. This may explain the lack of clinical benefit with these drugs against sudden cardiac death. Because none of the drugs were proarrhythmic in ischemic hearts in which arrhythmia susceptibility had been lowered by high K(+), it would seem that clinical proarrhythmia seen with these drugs may not be related to exacerbation of phase-1, ischemia-induced VF.

Is aspirin "the weakest link" in cardiovascular prophylaxis? The surprising lack of evidence supporting the use of aspirin for cardiovascular disease

It is currently fashionable to prescribe aspirin, long-term to people with or at high risk of vascular events due to atherosclerosis. There is a moderately conclusive evidence for a short-term benefit after an acute vascular event. However, there is remarkably little evidence that long-term aspirin is effective for the prevention of vascular events and managing side effects may be expensive. Reductions in nonfatal vascular events may reflect an ability of aspirin to alter cosmetically the presentation of disease without exerting real benefit. Cardiovascular medicine appears prone to fads and fashions that are poorly substantiated by evidence. The current fashion for prescribing aspirin is reminiscent of the now discredited practice of widespread prescription of class I anti-arrhythmic drugs for ventricular ectopics. We should learn from experience.

Does aspirin attenuate the effect of angiotensin-converting enzyme inhibitors in hypertension or heart failure?

There is a wealth of data that suggests an important interaction between aspirin and angiotensin-converting enzyme inhibitors in patients with chronic stable cardiovascular disease. The interaction is less obvious in the postinfarction setting, possibly reflecting the fact that many patients stop their aspirin therapy within a few months of such an event. An interaction is biologically plausible, because there is considerable evidence that angiotensin-converting enzyme inhibitors exert important effects through increasing the production of vasodilator prostaglandins, whereas aspirin blocks their production through inhibition of cyclooxygenase, even at low doses. There is some evidence that low-dose aspirin may raise systolic and diastolic blood pressure. There is also considerable evidence that aspirin may entirely neutralize the clinical benefits of angiotensin-converting enzyme inhibitors in patients with heart failure. In addition, aspirin may have an adverse effect on outcome in patients with heart failure that is independent of any interaction with angiotensin-converting enzyme inhibitors, possibly by blocking endogenous vasodilator prostaglandin production and enhancing the vasoconstrictor potential of endothelin. The evidence is not sufficient to justify advising long-term aspirin therapy for patients with cardiovascular disease in general, and for those with heart failure in particular. Thus, the lack of evidence of benefit with aspirin in patients with heart failure and coronary disease, along with growing evidence that aspirin is directly harmful in patients with heart failure and that aspirin may negate the benefits of angiotensin-converting enzyme inhibitors suggest that, unless there is an opportunity to randomize the patient into a study of antithrombotic strategies, then aspirin should be withdrawn or possibly substituted with an anticoagulant or an antiplatelet agent that does not block cyclooxygenase. In contrast, there is fairly robust evidence for a benefit of both aspirin and angiotensin-converting enzyme inhibitors during the first 5 weeks after a myocardial infarction, with little evidence of an interaction. The combination of aspirin and angiotensin-converting enzyme inhibitors is warranted during this period, after which discontinuation or substitution of aspirin with another agent should be considered.

Defibrillation energy requirements and electrical heterogeneity during total body hypothermia

OBJECTIVE

Determine the effects of hypothermia on defibrillation energy requirements and cardiac electrophysiology.

DESIGN

Prospective randomized acute intervention trial.

SETTING

Medical center animal laboratory.

SUBJECTS

Fifteen domestic farm swine.

INTERVENTIONS

Swine were randomized to a hypothermia group (n = 8) or a control group (n = 7). All animals were instrumented with a transvenous defibrillation system connected to a defibrillator that delivers a biphasic-truncated waveform. Values for defibrillation energy requirements were measured at baseline (normothermia, 38-40 degrees C) and during treatment with total body hypothermia (30 degrees C) or no temperature change (sham). Hypothermia was induced by circulating ice-water through anterior and posterior surgical thermal blankets.

MEASUREMENTS AND MAIN RESULTS

Defibrillation energy requirement values at 20%, 50%, and 80% were determined by using an up/down method. In the hypothermia group, defibrillation energy requirement values at baseline did not significantly change during hypothermia (defibrillation energy requirements 50% = 14 +/- 2 J vs. 15 +/- 2 J, respectively). Similarly, the defibrillation energy requirement values in the control group did not change from baseline to sham phase (defibrillation energy requirements 50% = 12 +/- 1 J vs. 13 +/- 1 J, respectively). Hypothermia profoundly affected cardiac electrophysiology, decreasing ventricular fibrillation threshold by 72%, conduction velocity by 25% (p < .01), and tissue excitability, while it prolonged ventricular repolarization and refractoriness by 7.5% to 15%, respectively (p < .05).

CONCLUSIONS

Total body cooling to 30 degrees C was highly arrhythmogenic, although this unstable electrophysiological state did not alter ventricular defibrillation energy requirements. These data suggest that hypothermia may be used to slow metabolic processes without concern over the ability to successfully defibrillate and treat hypothermia-induced arrhythmias.

What is the optimal medical management of ischemic heart failure?

Ischemic heart disease is an important and common contributor to the development of heart failure. Theoretically, all patients with heart failure may benefit from treatment designed to retard progressive ventricular dysfunction and arrhythmias. Patients with ischemic heart disease may also theoretically benefit from the relief of ischemia, the prevention of coronary occlusion, and revascularization. However, there is little evidence to show that the presence or absence of coronary disease modifies the benefits of effective treatments such as angiotensin-converting enzyme inhibitors and beta-blockers. Moreover, there is no evidence that treatment directed specifically at myocardial ischemia or coronary disease alters outcome in patients with heart failure. Treatments aimed at relieving painless myocardial ischemia have not been shown to alter prognosis. Lipid-lowering therapy is theoretically attractive for patients with heart failure and coronary disease; however, theoretical concerns also exist about the safety of such agents, and patients with heart failure have been excluded from large outcome studies very effectively. Some agents, such as aspirin, designed to reduce the risk of coronary occlusion seem ineffective or harmful in patients with heart failure, although warfarin may be safe and possibly effective. There is no evidence yet that revascularization improves prognosis in patients with heart failure, even in patients who are shown to have extensive myocardial hibernation. On current evidence, revascularization should be reserved for the relief of angina. Large-scale, randomized controlled trials are currently underway that are investigating the role of specific treatments targeted at coronary syndromes. The Carvedilol Hibernation Reversible Ischemia Trial: Marker of Success study is investigating the effects of carvedilol in a large cohort of patients with and without hibernating myocardium. The Warfarin and Antiplatelet Therapy in Chronic Heart Failure study is comparing the efficacy of aspirin, clopidogrel, and warfarin. The Heart Revascularization Trial-United Kingdom study is assessing the effect of revascularization on mortality in patients with heart failure and myocardial hibernation. Smaller scale studies are assessing the safety and efficacy of statin therapy in patients with heart failure. Only once the outcomes to these and other planned trials are known can the medical community know how best to treat their patients.

Duration of preoperative electrocardiographic QRS complex and the incidence of heart arrest after aorto coronary bypass surgery

Sudden heart arrest (HA) in the early phase after aorto coronary bypass surgery represents a serious event necessitating resuscitation, and for those who survive usually also an extra stay in the coronary care unit. Since such episodes of heart standstill may be related to conduction defects, a study was conducted to determine whether the duration of the QRS complex on the preoperative ECG is a marker for this morbid event. A cohort of 1011 consecutive patients operated on between 1982 and 1986 and followed to January 1st, 1993 were included in the study. Incidence of lethal or non-lethal HA during the first 4 weeks after surgery was considered as the primary endpoint and total mortality as the secondary endpoint. The incidence of HA was 40/1011 = 4%, with the majority of events (60%) being lethal. Independent risk factors of HA using the multivariate logistic model were previous coronary artery bypass surgery, presence of mitral regurgitation, left ventricular ejection fraction and the intraoperative cross-clamp time of aorta. Adjusting for the effect of confounder variables showed that the gradient effect of QRS complex duration on the endpoint HA was still present (p = 0.012). The duration of the QRS complex taken from the preoperative ECG had a gradient effect on the incidence of HA. With a baseline level of QRS <70 ms, the following odds ratios (OR) for HA were found: OR = 1.38 (95% CI 0.60-3.31) for QRS 70-80 ms; OR = 2.27 (95% CI 0.87-5.90) for QRS >90-120 ms; and OR = 3.38 (95% CI 1.06-11.50) for QRS > 120 ms, when adjusting for the risk factors. Cumulative survival at 5 years after surgery was 28+/-7.1% for patients experiencing HA versus 87+/-1.2% for patients free from this event. Our results underline the importance of the QRS complex duration as a preoperative marker for HA after aorta coronary bypass surgery, when adjusting for other risk factors. Although the one-year survival is poor for patients experiencing HA, there is no increase in mortality during the late follow-up.

What is the optimal medical management of ischaemic heart failure?

Ischaemic heart disease is probably the most important cause of heart failure. All patients with heart failure may benefit from treatment designed to retard progressive ventricular dysfunction and arrhythmias. Patients with heart failure due to ischaemic heart disease may also, theoretically, benefit from treatments designed to relieve ischaemia and prevent coronary occlusion and from revascularisation. However, there is little evidence to show that effective treatments, such as angiotensin converting enzyme (ACE) inhibitors and beta-blockers, exert different effects in patients with heart failure with or without coronary disease. Moreover, there is no evidence that treatment directed specifically at myocardial ischaemia, whether or not symptomatic, or coronary disease alters outcome in patients with heart failure. Some agents, such as aspirin, designed to reduce the risk of coronary occlusion appear ineffective or harmful in patients with heart failure. There is no evidence, yet, that revascularisation improves prognosis in patients with heart failure, even in patients who are demonstrated to have extensive myocardial hibernation. On current evidence, revascularisation should be reserved for the relief of angina. Large-scale, randomised controlled trials are currently underway investigating the role of specific treatments targeted at coronary syndromes in patients who have heart failure. The CHRISTMAS study is investigating the effects of carvedilol in a large cohort of patients with and without hibernating myocardium. The WATCH study is comparing the efficacy of aspirin, clopidogrel and warfarin. The HEART-UK study is assessing the effect of revascularisation on mortality in patients with heart failure and myocardial hibernation. Smaller scale studies are currently assessing the safety and efficacy of statin therapy in patients with heart failure. Only when the results of these and other studies are known will it be possible to come to firm conclusions about whether patients with heart failure and coronary disease should be treated differently from other patients with heart failure due to left ventricular systolic dysfunction.

Can antiarrhythmic agents be selected based on mechanism of action?

When selecting an antiarrhythmic agent the clinician needs to be able to accurately predict the probability that a particular drug will serve its intended purpose in a given patient. This is difficult because of the complexity of variables which govern the relationship between drug administration and clinical outcome. The efficacy of a drug may potentially be predicted from its mechanism of action. At least two classifications of antiarrhythmic agents based on mechanism of action have been proposed. The Vaughan Williams classification is based on the predominant electrophysiological effects of a drug on the action potential. In the Sicilian Gambit approach, a number of potential targets ('vulnerable parameters') for drug action are identified and antiarrhythmic drugs or substances that affect cardiac electrophysiology are characterised by their actions on each of these. The usefulness of these classification systems in predicting antiarrhythmic drug efficacy are limited. Furthermore, in the Vaughan Williams classification not all drugs in the same class have identical effects, whereas some drugs in different classes have overlapping actions. The Sicilian Gambit requires in-depth knowledge regarding cellular and molecular targets of antiarrhythmic agents which may make it intimidating or simply impractical for regular clinical use. Surrogate measures such as 24-hour Holter monitoring and programmed electrical stimulation have been used to predict anti-arrhythmic drug efficacy. However, studies such the Cardiac Arrhythmia Suppression Trial (CAST) have shown that suppression of ventricular ectopy on Holter monitoring does not necessarily correlate with improved survival and may in fact be dangerous. Conversely, studies using programmed electrical stimulation to assess drug effect on variables such as tachycardia inducibility, refractory period and ventricular tachycardia cycle length show that suppression of tachycardia inducibility, prolongation of refractory period and prolongation of ventricular tachycardia cycle length, are all associated with reduced recurrence of tachycardia and possibly improved survival. The most practical use of the current classification systems applied to antiarrhythmic agents may be in their ability to predict with reasonable accuracy, the risk and type of proarrhythmia based on the mechanism of action of an agent.

Treating electrical storm : sympathetic blockade versus advanced cardiac life support-guided therapy

BACKGROUND

Electrical storm (ES), defined as recurrent multiple ventricular fibrillation (VF) episodes, often occurs in patients with recent myocardial infarction. Because treating ES according to the Advanced Cardiac Life Support (ACLS) guidelines yields a poor outcome, we evaluated the efficacy of sympathetic blockade in treating ES patients and compared their outcome with that of patients treated according to the ACLS guidelines.

METHODS AND RESULTS

Forty-nine patients (36 men, 13 women, mean age 57+/-10 years) who had ES associated with a recent myocardial infarction were separated into 2 groups. Patients in group 1 (n=27) received sympathetic blockade treatment: 6 left stellate ganglionic blockade, 7 esmolol, and 14 propranolol. Patients in group 2 (n=22) received antiarrhythmic medication as recommended by the ACLS guidelines. Patient characteristics were similar in the 2 groups. The 1-week mortality rate was higher in group 2: 18 (82%) of the 22 patients died, all of refractory VF; 6 (22%) of the 27 group 1 patients died, 3 of refractory VF (P<0.0001). Patients who survived the initial ES event did well over the 1-year follow-up period: Overall survival in group 1 was 67%, compared with 5% in group 2 (P<0.0001).

CONCLUSIONS

Sympathetic blockade is superior to the antiarrhythmic therapy recommended by the ACLS guidelines in treating ES patients. Our study emphasizes the role of increased sympathetic activity in the genesis of ES. Sympathetic blockade-not class 1 antiarrhythmic drugs-should be the treatment of choice for ES.

Ischemia-induced action potential shortening is blunted by d-sotalol in a pig model of reversible myocardial ischemia

The purpose of this study was to investigate, in an anesthetized pig model of low-flow myocardial ischemia, the electrophysiologic effects of the class III drug d-sotalol during myocardial ischemia. Serial monophasic action potential (MAPD90) recordings and refractory period determinations from the anterior and posterior left ventricular wall were taken in 25 pigs during baseline, after low-flow posterior wall ischemia, after d-sotalol infusion under nonischemic conditions, and after repeated posterior wall ischemia while continuing the drug. Measurements were done at 60 and 150 beats/min after radiofrequency ablation of atrioventricular conduction. At baseline, MAPD90 and refractory periods were comparable in the anterior and posterior wall (323 +/- 15 vs. 318 +/- 10 ms, and 267 +/- 10 vs. 262 +/- 11 ms at 60 beats/min, respectively). In the absence of d-sotalol, low-flow regional ischemia was associated with a significant shortening of MAPD90 in the posterior versus the anterior wall (267 +/- 20 vs. 317 +/- 20 ms at 60 beats/min; p = 0.006). Similarly, ischemia-induced shortening of the refractory periods in the posterior wall was apparent (230 +/- 16 ms in the posterior wall vs. 274 +/- 14 ms in the anterior wall at 60 beats/min). In contrast, ischemia was no longer associated with shortening of MAPD90 (360 +/- 17 ms posterior wall and 360 +/- 20 ms anterior wall at 60 beats/min) and refractory periods (304 +/- 19 ms posterior wall vs. 316 +/- 15 ms anterior wall at 60 beats/min) during combined posterior wall ischemia and d-sotalol infusion. Similar findings were obtained during pacing at 150 beats/min. d-Sotalol attenuates ischemia-induced action potential shortening. This property should decrease dispersion of cardiac repolarization and be antiarrhythmic. On the other hand, longer APD under ischemic conditions may favor calcium overload, which may trigger new arrhythmias.

Evolution, mechanisms, and classification of antiarrhythmic drugs: focus on class III actions

Since the use of cinchona bark to treat heart palpitations in the 1700s, antiarrhythmic drug therapy has developed with the discovery of new compounds and the identification of ionic, cellular, and tissue mechanisms of action. Classifications have been developed that organize the large amount of information available about antiarrhythmic drugs around groups of compounds with common mechanisms of action. Despite important and well-recognized limitations, antiarrhythmic drug classification is still widely used. In particularly broad use is the system developed by Singh and Vaughan Williams in the early 1970s and subsequently modified by Singh and Hauswirth and by Harrison. This classification divides drug actions into class I for sodium-channel blockade (with subclasses IA, IB and IC), class II for adrenergic antagonism, class III for action-potential prolongation, and class IV for calcium-channel blockade. The development of class I drugs was curtailed when studies showed that potent sodium-channel blockers (particularly IC agents) can increase mortality in patients with active coronary artery disease. The emphasis in drug development shifted to class III agents, but their use has been limited by the risk of ventricular tachyarrhythmia induction associated with QT prolongation. Current research focuses on the development of new class III drugs that may have improved safety by virtue of greater selectivity of action at faster rates (like those of arrhythmia) or for atrial tissue. Alternative approaches include the modification of existing molecules (like amiodarone) to maintain positive properties while removing undesirable ones, and treatments that target development of the arrhythmia substrate instead of the final electrical product.

Treating depression in patients with ischaemic heart disease: which agents are best to use and to avoid?

There are a number of dimensions to the complex relationship between cardiovascular disease and affective disorders including: (i) patients with depression are at an increased risk of dying from sudden cardiovascular death compared with the general population; (ii) patients with depression over the course of a lifetime have a higher rate of symptomatic and fatal ischaemic heart disease compared with a control group without depression; and, (iii) patients after either a myocardial or a cerebrovascular infarction who are depressed have a higher mortality rate than their medically comparable nondepressed counterparts. The deleterious impact of depression on the prognosis of cardiac disease and the suggestion that treatment of depression may reduce cardiac mortality has led clinicians to seek safe and effective treatment for patients with comorbid depression and ischaemic disease. Though they are robustly effective, the tricyclic antidepressants are type 1A antiarrhythmic agents and presumably carry the same risk in patients with ischaemic disease as treatment with other type 1 antiarrhythmics such as moricizine. Short term studies of the safety of other antidepressant agents, specifically amfebutamone (bupropion) and the selective serotonin (5-hydroxytryptamine; 5-HT) reuptake inhibitors (SSRIs) fluoxetine, paroxetine and sertraline, suggest that these medications have a benign cardiovascular profile in patients with depression and pre-existing cardiac disease. However, given the methodological limitations of study design and the relatively small number of patients included, it is premature to conclude that SSRIs are a 'safe' treatment in patients with heart disease. Thus, clinicians must still make treatment decisions on a case by case basis, considering the type and severity of depression and cardiovascular disease, as well as what is known about the cardiovascular effects and therapeutic profile of the different classes of antidepressant medications.

Optimal management with Class I and Class III antiarrhythmic drugs should be done in the outpatient setting: protagonist

It has been suggested that patients be admitted for the initiation of Class I and Class III antiarrhythmic drugs to avoid serious proarrhythmic consequences. The most clinically significant proarrhythmic response to Class IC agents is likely due to an interaction with acute ischemia, and hospitalization for initiation of drug therapy has little predictive or preventive value. Amiodarone has a low risk of proarrhythmia, and any proarrhythmic reactions are generally delayed. Class IA and Class III antiarrhythmic drugs cause acquired long QT syndrome arrhythmias, which can occur soon after initiation of therapy; however, only about half of the arrhythmic events occur within 3 days of initiation of therapy. It could be argued that all patients should be hospitalized to begin Class IA or Class III drugs; however, this approach has a low yield and is extremely expensive. An alternative is to use Class IA and Class III drugs for patients at low risk of torsades de pointes (e.g., males without heart failure, ventricular tachyarrhythmias, or active coronary disease), in whom hospitalization for drug initiation is not warranted. Higher risk patients are probably better treated with other agents, such as Class IC drugs or amiodarone for women without organic heart disease and amiodarone for patients with heart failure, a history of ventricular tachycardia, or active coronary disease. When a Class IA or Class III drug is required for patient with an increased risk of torsades de pointes, hospital admission for drug initiation may be indicated.

The molecular and ionic specificity of antiarrhythmic drug actions

Virtually all clinical antiarrhythmic agents act by reducing ion channel conductance, with sodium (Na+), potassium (K+), and calcium (Ca++) channels the primary targets. Na+ channel blockers increase the risk of ischemic ventricular fibrillation and are relatively contraindicated in the presence of active coronary heart disease. Ca++ channel blockers suppress AV nodal conduction and are used to terminate reentrant supraventricular arrhythmias and control the ventricular response to atrial fibrillation. K+ channels constitute the most diverse group of cardiac ion channels. They are the primary targets of Class III antiarrhythmic drugs, the category of such agents presently undergoing the most active development. The rapid delayed rectifier, IKr, plays a key role in repolarization of all cardiac tissues and is the most common (and often only) target of action potential-prolonging drugs. Unfortunately, because of the ubiquity of IKr and the reverse use-dependent action potential prolongation that results from blocking it, IKr blockers are likely to cause torsades de pointes ventricular proarrhythmia. K+ channel blockers, such as amiodarone and azimilide, that affect the slow delayed rectifier IKs as well as IKr, appear to produce a more desirable rate-dependent profile of Class III action. Recently, much has been learned about the molecular basis of K+ channels based on their role in the congenital long QT syndrome. The availability of molecular clones that encode many of the channels in the human heart allows for the rapid screening of many potential new drugs, making possible the development of "designer" antiarrhythmic drugs with specific profiles of channel-blocking selectivity.

Antiarrhythmic therapies for the prevention of sudden cardiac death

Despite remarkable advances in cardiovascular therapeutics, sudden cardiac death remains a significant problem. In this review, data from clinical trials and other studies on antiarrhythmic therapies have been evaluated in order to determine effective strategies for the prevention of sudden cardiac death in high risk patients. Overall, routine prophylactic use of class I antiarrhythmic agents in high risk patients, mostly survivors of acute myocardial infarction, is associated with increased risk of death [61 trials, 23,486 patients: odds ratio (OR) 1.13; 95% confidence interval (CI) 1.01 to 1.27, p < 0.05]. Conversely, beta-blockers are associated with highly significant reductions in risk of death in postinfarction patients (56 trials, 53,521 patients: OR 0.81; 95% CI 0.75 to 0.87, p < 0.00001). Overall data from the amiodarone trials on high risk patients, including postinfarction patients, patients with congestive heart failure or survivors of cardiac arrest, suggest that this agent is effective in reducing the risk of death (14 trials, 5713 patients: OR 0.83; 95% CI 0.72 to 0.95, p = 0.01) although further studies are needed to better define which types of patients will potentially benefit most from this agent. No benefits were seen with calcium channel blockers (26 trials, 21,644 patients: OR 1.03; 95% CI 0.94 to 1.13, p = NS). The implantable cardioverter-defibrillator is a promising option for high risk patients, but definition of its role awaits the completion of ongoing clinical trials. Since causes of sudden death are heterogeneous, the clinician should pursue a multifactorial approach to its prevention. Primary and secondary prevention of cardiac ischaemia, through the treatment of cardiovascular risk factors and maximising the use of aspirin, beta-blockers, lipid-lowering drugs, and angiotensin converting enzyme inhibitors after acute myocardial infarction, should lead to a future decrease in the incidence of sudden cardiac death.

Randomised trial of effect of amiodarone on mortality in patients with left-ventricular dysfunction after recent myocardial infarction: EMIAT. European Myocardial Infarct Amiodarone Trial Investigators

BACKGROUND

Ventricular arrhythmias are a major cause of death after myocardial infarction, especially in patients with poor left-ventricular function. Previous attempts to identify and suppress arrhythmias with various antiarrhythmic drugs failed to reduce or actually increase mortality. Amiodarone is a powerful antiarrhythmic drug with several potentially beneficial actions, and has shown benefit in several small-scale studies. We postulated that this drug might reduce mortality in patients at high risk of death after myocardial infarction because of impaired ventricular function, irrespective of whether they had ventricular arrhythmias.

METHODS

The European Myocardial Infarct Amiodarone Trial (EMIAT) was a randomised double-blind placebo-controlled trial to assess whether amiodarone reduced all-cause mortality (primary endpoint) and cardiac mortality and arrhythmic death (secondary endpoints) in survivors of myocardial infarction with a left-ventricular ejection fraction (LVEF) of 40% or less. Intention-to-treat and on-treatment analyses were done.

FINDINGS

EMIAT enrolled 1486 patients (743 in the amiodarone group, 743 in the placebo group). Median follow-up was 21 months. All-cause mortality (103 deaths in the amiodarone group, 102 in the placebo group) and cardiac mortality did not differ between the two groups. However, in the amiodarone group, there was a 35% risk reduction (95% CI 0-58, p = 0.05) in arrhythmic deaths.

INTERPRETATION

Our findings do not support the systematic prophylactic use of amiodarone in all patients with depressed left-ventricular function after myocardial infarction. However, the lack of proarrhythmia and the reduction in arrhythmic death support the use of amiodarone in patients for whom antiarrhythmic therapy is indicated.