Treatment and prophylaxis of ventricular arrhythmias in acute myocardial infarction

Prophylactic lidocaine for myocardial infarction

BACKGROUND

Coronary artery disease is a major public health problem affecting both developed and developing countries. Acute coronary syndromes include unstable angina and myocardial infarction with or without ST-segment elevation (electrocardiogram sector is higher than baseline). Ventricular arrhythmia after myocardial infarction is associated with high risk of mortality. The evidence is out of date, and considerable uncertainty remains about the effects of prophylactic use of lidocaine on all-cause mortality, in particular, in patients with suspected myocardial infarction.

OBJECTIVES

To determine the clinical effectiveness and safety of prophylactic lidocaine in preventing death among people with myocardial infarction.

SEARCH METHODS

We searched the Cochrane Central Register of Controlled Trials (CENTRAL) (2015, Issue 3), MEDLINE Ovid (1946 to 13 April 2015), EMBASE (1947 to 13 April 2015) and Latin American Caribbean Health Sciences Literature (LILACS) (1986 to 13 April 2015). We also searched Web of Science (1970 to 13 April 2013) and handsearched the reference lists of included papers. We applied no language restriction in the search.

SELECTION CRITERIA

We included randomised controlled trials assessing the effects of prophylactic lidocaine for myocardial infarction. We considered all-cause mortality, cardiac mortality and overall survival at 30 days after myocardial infarction as primary outcomes.

DATA COLLECTION AND ANALYSIS

We performed study selection, risk of bias assessment and data extraction in duplicate. We estimated risk ratios (RRs) for dichotomous outcomes and measured statistical heterogeneity using I(2). We used a random-effects model and conducted trial sequential analysis.

MAIN RESULTS

We identified 37 randomised controlled trials involving 11,948 participants. These trials compared lidocaine versus placebo or no intervention, disopyramide, mexiletine, tocainide, propafenone, amiodarone, dimethylammonium chloride, aprindine and pirmenol. Overall, trials were underpowered and had high risk of bias. Ninety-seven per cent of trials (36/37) were conducted without an a priori sample size estimation. Ten trials were sponsored by the pharmaceutical industry. Trials were conducted in 17 countries, and intravenous intervention was the most frequent route of administration.In trials involving participants with proven or non-proven acute myocardial infarction, lidocaine versus placebo or no intervention showed no significant differences regarding all-cause mortality (213/5879 (3.62%) vs 199/5848 (3.40%); RR 1.02, 95% CI 0.82 to 1.27; participants = 11727; studies = 18; I(2) = 15%); low-quality evidence), cardiac mortality (69/4184 (1.65%) vs 62/4093 (1.51%); RR 1.03, 95% CI 0.70 to 1.50; participants = 8277; studies = 12; I(2) = 12%; low-quality evidence) and prophylaxis of ventricular fibrillation (76/5128 (1.48%) vs 103/4987 (2.01%); RR 0.78, 95% CI 0.55 to 1.12; participants = 10115; studies = 16; I(2) = 18%; low-quality evidence). In terms of sinus bradycardia, lidocaine effect is imprecise compared with effects of placebo or no intervention (55/1346 (4.08%) vs 49/1203 (4.07%); RR 1.09, 95% CI 0.66 to 1.80; participants = 2549; studies = 8; I(2) = 21%; very low-quality evidence). In trials involving only participants with proven acute myocardial infarction, lidocaine versus placebo or no intervention showed no significant differences in all-cause mortality (148/2747 (5.39%) vs 135/2506 (5.39%); RR 1.01, 95% CI 0.79 to 1.30; participants = 5253; studies = 16; I(2) = 9%; low-quality evidence). No significant differences were noted between lidocaine and any other antiarrhythmic drug in terms of all-cause mortality and ventricular fibrillation. Data on overall survival 30 days after myocardial infarction were not reported. Lidocaine compared with placebo or no intervention increased risk of asystole (35/3393 (1.03%) vs 14/3443 (0.41%); RR 2.32, 95% CI 1.26 to 4.26; participants = 6826; studies = 4; I(2) = 0%; very low-quality evidence) and dizziness/drowsiness (74/1259 (5.88%) vs 16/1274 (1.26%); RR 3.85, 95% CI 2.29 to 6.47; participants = 2533; studies = 6; I(2) = 0%; low-quality evidence). Overall, safety data were poorly reported and adverse events may have been underestimated. Trial sequential analyses suggest that additional trials may not be needed for reliable conclusions to be drawn regarding these outcomes.

AUTHORS' CONCLUSIONS

This Cochrane review found evidence of low quality to suggest that prophylactic lidocaine has very little or no effect on mortality or ventricular fibrillation in people with acute myocardial infarction. The safety profile is unclear. This conclusion is based on randomised controlled trials with high risk of bias. However (disregarding the risk of bias), trial sequential analysis suggests that additional trials may not be needed to disprove an intervention effect of 20% relative risk reduction. Smaller risk reductions might require additional higher trials.

Feasibility of targeting ischaemia-related ventricular arrhythmias by mimicry of endogenous protection by endocannabinoids

BACKGROUND AND PURPOSE

The hypothesis that endocannabinoids protect hearts against ventricular fibrillation (VF) induced by myocardial ischaemia and reperfusion was examined, and the concept that cannabinoids may represent a new class of anti-VF drug was tested.

EXPERIMENTAL APPROACH

In rat isolated hearts (Langendorff perfusion), VF evoked by reperfusion after 60 min regional ischaemia is known to be exacerbated by inhibitors of endogenous protectants such as nitric oxide. This preparation was used to assay the effects of cannabinoid agonists and antagonists, and the protocols were varied to examine mechanisms.

KEY RESULTS

Reperfusion-induced VF was not facilitated by relatively selective CB1 (1 μM AM251) or CB2 (1 μM AM630) antagonists. VF evoked during early (30 min) acute ischaemia was also unaffected. However, AM251 significantly increased the incidence of VF and the duration of VF episodes occurring during the later stage of acute ischaemia (30-60 min). AM630 had no such effects. In a separate study, cannabinoid perfusion (anandamide or 2-arachidonoylglycerol, both 0.01-1 μM) failed to reduce VF incidence concentration-dependently during 30 min ischaemia. In all these studies, changes in ancillary variables (QT, PR, heart rate) were unrelated to changes in VF.

CONCLUSIONS AND IMPLICATIONS

Endocannabinoids are not endogenous anti-VF mediators during reperfusion, but may have a weak protective effect during the late stages of ischaemia, mediated via CB1 agonism. This does not suggest endocannabinoids are important endogenous protectants in these settings, or that CB1 (or CB2) receptors are useful novel targets for developing drugs for VF.

Possible mechanisms of sudden cardiac death in top athletes: a basic cardiac electrophysiological point of view

Sudden death among athletes is very rare (1:50,000-1:100,000 annually) but it is still 2-4 times more frequent than in the age-matched control population and attracts significant media attention. We propose a mechanism underlying sudden cardiac death in athletes that does not relate to myocardial ischemia but is based on repolarization abnormalities due to potassium channel downregulation and can also be best explained by the concurrent presence of several factors such as cardiac hypertrophy (athlete's heart), and/or hypertrophic cardiomyopathy, increased sympathetic tone, genetic defects, drugs, doping agents, food, or dietary ingredients. These factors together can increase the repolarization inhomogeneity of the heart ("substrate") and an otherwise harmless extrasystole ("trigger") occurring with a very unfortunate timing may sometimes induce life-threatening arrhythmias. The effective and possible prevention of sudden cardiac death requires the development of novel cost effective cardiac electrophysiological screening methods. Athletes identified by these tests as individuals at higher proarrhythmic risk should then be subjected to more costly genetic tests in order to uncover possible underlying genetic causes for alterations in ionic channel structure and/or function.

Druggable targets for sudden cardiac death prevention: lessons from the past and strategies for the future

Sudden cardiac death (SCD) is most commonly caused by ventricular fibrillation (VF). The single largest cohort of victims is the population with little or no prior overt heart disease. Effective prevention will require long-term prophylaxis by drugs in large numbers of people identified by risk factors. This means that safe as well as effective drugs are required. Drugs with overt effects on cardiac electrophysiology have failed in the clinic owing to poor effectiveness and/or adverse effects. This article examines possible new drug targets. We have focused on acute myocardial ischaemia as it is the most strikingly proarrhythmic pathology, and the most common cause of coronary artery disease-related VF and SCD according to inferences from epidemiology, drug trials and decades of animal research. To set the scene we have briefly explored drugs that have failed in the clinic in order to identify possible targets that have been overlooked or underexploited. We conclude that the best strategy is identification of pathology-specific targets that render drugs active only where and when their action is required.

Phase 2 ventricular arrhythmias in acute myocardial infarction: a neglected target for therapeutic antiarrhythmic drug development and for safety pharmacology evaluation

Ventricular fibrillation (VF), a cause of sudden cardiac death (SCD) in the setting of acute myocardial infarction (MI), remains a major therapeutic challenge. In humans, VF may occur within minutes or hours after the onset of chest pain, so its precise timing in relation to the onset of ischaemia is variable. Moreover, because VF usually occurs unobserved, out of hospital, and is usually lethal in the absence of intervention, its precise timing of onset is actually unknown in most patients. In animal models, the timing of susceptibility to VF is much better characterised. It occurs in two distinct phases. Early VF (defined as phase 1 VF, with possible subphases 1a and 1b in some animal species) occurs during the first 30 min of ischaemia when most myocardial injury is still reversible. Late VF, defined as phase 2 VF, occurs when myocardial necrosis is becoming established (after more than 90 min of ischaemia). Although much is known about the mechanisms and pharmacology of phase 1 VF, little is known about phase 2 VF. By reviewing a range of different types of data we have outlined the likely mechanisms and clinical relevance of phase 2 VF, and have evaluated possible future directions to help evolve a strategy for its suppression by drugs. The possibility that a proarrhythmic effect on phase 2 VF contributes to the adverse cardiac effects of certain cardiac and noncardiac drugs is also discussed in relation to the emerging field of safety pharmacology. It is concluded that suppression of phase 2 as well as phase 1 VF will almost certainly be necessary if drugs of the future are to achieve what drugs of the past and present have failed to achieve: full protection against SCD. Likewise, safety will require avoidance of exacerbation of phase 2 as well as phase 1 VF.

Ventricular fibrillation in acute myocardial infarction in Spanish patients: Results of the ARIAM database

OBJECTIVE

The aim of this study has been to investigate the factors predisposing to primary or secondary ventricular fibrillation (VF) and the prognosis in Spanish patients with acute myocardial infarction (AMI) during their admission to the intensive care unit or the coronary care unit.

DESIGN

A retrospective, observational study.

SETTING

The intensive care units and coronary care units of 119 Spanish hospitals.

PATIENTS

A retrospective cohort study including all the AMI patients listed in the ARIAM registry (Analysis of Delay in Acute Myocardial Infarction), a Spanish multicenter study. The study period was January 1995 to January 2001.

MEASUREMENTS AND MAIN RESULTS

Factors associated with the onset of VF were studied by univariate analysis. Multivariate analysis was used to evaluate the independent factors for the onset of VF and for mortality. A total of 17,761 patients with AMI were included in the study; 964 (5.4%) developed VF (primary in 735 patients, secondary in 229). In multivariate analysis, the variables that continued to show an association with the development of VF were the Killip and Kimball class, peak creatine kinase, APACHE II score, age, and time from the onset of symptoms to the initiation of thrombolysis. The mortality in the patients with any VF was 31.8% (27.8% in patients with primary VF and 49.1% in patients with secondary VF). The development of VF is an independent predictive factor for mortality in patients with AMI, with a crude odds ratio of 5.12 (95% confidence interval, 4.41-5.95) and an adjusted odds ratio of 2.73 (95% confidence interval, 2.12-3.51).

CONCLUSIONS

Despite the considerable improvement in the treatment of AMI in recent years, the onset of either primary or secondary VF is associated with a poor prognosis. It is usually accompanied by extensive necrosis.

Ventricular arrhythmias in trials of thrombolytic therapy for acute myocardial infarction. A meta-analysis

BACKGROUND

Although thrombolytic therapy reduces long-term mortality in acute myocardial infarction, many clinicians remain concerned about an increased risk of ventricular arrhythmias associated with the use of these agents.

METHODS AND RESULTS

To determine whether thrombolytic therapy increases the risk of ventricular tachyarrhythmias and whether an increase in arrhythmias could be responsible for the increased mortality seen in the first 24 hours after lytic therapy, we performed a meta-analysis of 15 randomized trials of thrombolysis in acute myocardial infarction in which the odds of developing in-hospital ventricular fibrillation (VF) and ventricular tachycardia (VT) in patients receiving thrombolysis was compared with that of patients receiving placebo. For trials that reported the incidence of VF during the first 6 hours after thrombolysis, the summary odds ratio for developing VF in the thrombolytic group was 0.98 (95% confidence interval [CI], 0.6 to 1.6; P = .94). For trials that reported the incidence of VF during the first hospital day, the summary odds ratio for developing VF was 1.00 (95% CI, 0.85 to 1.2; P = .95). The summary odds ratio for the development of VF at any time during hospitalization in the thrombolytic group was 0.83 (95% CI, 0.76 to 0.90; P < .0001). In trials that reported the incidence of VT any time during hospitalization, the summary odds ratio for the development of VT in the thrombolytic group was 1.34 (95% CI, 1.15 to 1.55; P < .0001).

CONCLUSIONS

The likelihood of developing VF in the early hours after thrombolysis for acute myocardial infarction is similar in patients receiving thrombolytics or placebo. However, throughout the hospital course, the risk of VF is greater in patients receiving placebo, whereas the risk of VT is higher in patients receiving thrombolysis.

Prognosis of acute myocardial infarction complicated by primary ventricular fibrillation. Principal Investigators of the SPRINT Study

In 5,839 consecutive patients with acute myocardial infarction (AMI), hospitalized between July 1981 and July 1983 in 14 coronary care units in Israel, the incidence of primary ventricular fibrillation (VF) was 2.1%. Patients with primary VF resembled counterparts without VF in terms of age, gender, frequency of previous AMI and past cigarette smoking habits. The hospital course of patients with primary VF revealed increased incidence of primary atrial fibrillation and atrioventricular block. Increased serum levels of glutamic oxaloacetic transaminase and lactic dehydrogenase were noted among the patients with primary VF. In-hospital mortality rate was 18.8% in 122 patients with primary VF compared with 8.5% in 3,707 patients forming the reference group (p less than 0.01). Adjustment by age using logistic function yielded an estimate of 2.86 for relative mortality odds associated with primary VF, and further adjustment by gender, history of AMI, systemic hypertension, and by enzymatically estimated infarct size slightly reduced the estimated odds, at 2.52 (95% confidence interval, 1.42 to 4.46). Prognosis after discharge from the hospital was independent of primary VF. In conclusion, primary VF exerts an independent, significant effect on in-hospital mortality.

Prophylactic lidocaine for postoperative coronary artery bypass patients, a double-blind, randomized trial

This double-blind controlled study examined the frequency of ventricular arrhythmias (premature ventricular contractions (PVCs) greater than 5.min-1, bigeminy, couplets, ventricular tachycardia, and ventricular fibrillation) in coronary artery bypass graft (CABG) patients during the first 24 hr postoperatively to determine the effect of prophylactic lidocaine on reducing the frequency of ventricular arrhythmias. Patients were included in the study if they had undergone CABG only, and had not received treatment for ventricular arrhythmias before coming off cardiopulmonary bypass. A total of 83 patients were studied and were randomly allocated to 43 in the placebo control group and 40 in the lidocaine-treated group. The results showed that 67 per cent of patients in the placebo group and 33 per cent of patients in the lidocaine treated group had ventricular arrhythmias (P less than 0.005). There was also a significant reduction in ventricular fibrillation and ventricular tachycardia in the lidocaine treated group (P less than 0.01). It is recommended that a routine infusion of lidocaine, 100 mg bolus followed by 2 mg.kg-1, be given to every postoperative coronary artery bypass patient for at least the first 24 hours.

In-hospital prognosis of patients with acute myocardial infarction complicated by primary ventricular fibrillation

The in-hospital prognosis of patients with acute myocardial infarction complicated by primary ventricular fibrillation has not been satisfactorily defined. We addressed this question by studying patients with primary ventricular fibrillation derived from a large study (11,712 patients) of intravenous streptokinase in the treatment of acute myocardial infarction. Ventricular fibrillation was considered to be primary when it complicated a first myocardial infarction not associated with heart failure or shock and occurred within 48 hours of hospital admission. The 332 patients with primary ventricular fibrillation represented an overall incidence of 2.8 percent. A significant excess of in-hospital deaths was found in the patients with primary ventricular fibrillation as compared with those in the reference group (10.8 percent vs. 5.9 percent; relative risk, 1.94; 95 percent confidence interval, 1.35 to 2.78). Thrombolytic treatment with intravenous streptokinase did not afford protection against primary ventricular fibrillation. We observed that being over 65 years old had a protective effect against primary ventricular fibrillation (relative risk, 0.6; 95 percent confidence interval, 0.45 to 0.80). Our data do not indicate whether primary ventricular fibrillation is simply a marker for patients at increased risk of death or a direct cause of the increase in mortality. Our results do show, however, that primary ventricular fibrillation occurring in a coronary care unit is a negative predictor of short-term survival in patients with acute myocardial infarction.

Therapeutic trends in the management of patients with acute myocardial infarction (1975-1984): the Worcester Heart Attack Study

As part of an ongoing community-wide study of time trends in the incidence and case-fatality rates of patients hospitalized with acute myocardial infarction (MI) in all 16 Worcester, Massachusetts, metropolitan hospitals during the years 1975, 1978, 1981, and 1984, changes over time in the therapeutic management of 3263 patients with validated acute myocardial infarction were examined. Beta-blocker (21%, 1975; 52%, 1984) and nitrate (56%, 1975; 93%, 1984) therapy use increased dramatically over time. Use of antiplatelet agents was inconsistent over time, while use of digoxin remained stable, being used in approximately 40% of all patients over the four periods studied. Use of antiarrhythmic medications other than lidocaine decreased consistently over time (31%, 1975; 22%, 1984). Lidocaine use increased between 1975 (31%) and 1978 (52%) and then leveled off to being used in approximately 45% of hospitalized patients with acute MI in 1981 and 1984. A variety of demographic (e.g., age, sex, teaching hospital) and clinical characteristics (e.g., MI order, MI type, MI location, peak CPK findings, occurrence of acute clinical complications) were also associated with the use of these therapies for the combined study periods. The results of this population-based study suggest considerable changes over time in the therapeutic management of patients hospitalized with acute myocardial infarction and of numerous patient demographic and clinical factors associated with their use.