Prevention of ventricular fibrillation during acute myocardial infarction by intravenous propranolol

Handling of Ventricular Fibrillation in the Emergency Setting

Ventricular fibrillation (VF) and sudden cardiac death (SCD) are predominantly caused by channelopathies and cardiomyopathies in youngsters and coronary heart disease in the elderly. Temporary factors, e.g., electrolyte imbalance, drug interactions, and substance abuses may play an additive role in arrhythmogenesis. Ectopic automaticity, triggered activity, and reentry mechanisms are known as important electrophysiological substrates for VF determining the antiarrhythmic therapies at the same time. Emergency need for electrical cardioversion is supported by the fact that every minute without defibrillation decreases survival rates by approximately 7%–10%. Thus, early defibrillation is an essential part of antiarrhythmic emergency management. Drug therapy has its relevance rather in the prevention of sudden cardiac death, where early recognition and treatment of the underlying disease has significant importance. Cardioprotective and antiarrhythmic effects of beta blockers in patients predisposed to sudden cardiac death were highlighted in numerous studies, hence nowadays these drugs are considered to be the cornerstones of the prevention and treatment of life-threatening ventricular arrhythmias. Nevertheless, other medical therapies have not been proven to be useful in the prevention of VF. Although amiodarone has shown positive results occasionally, this was not demonstrated to be consistent. Furthermore, the potential proarrhythmic effects of drugs may also limit their applicability. Based on these unfavorable observations we highlight the importance of arrhythmia prevention, where echocardiography, electrocardiography and laboratory testing play a significant role even in the emergency setting. In the following we provide a summary on the latest developments on cardiopulmonary resuscitation, and the evaluation and preventive treatment possibilities of patients with increased susceptibility to VF and SCD.

Beta-blockers for suspected or diagnosed acute myocardial infarction

BACKGROUND

Cardiovascular disease is the number one cause of death globally. According to the World Health Organization, 7.4 million people died from ischaemic heart diseases in 2012, constituting 15% of all deaths. Acute myocardial infarction is caused by blockage of the blood supplied to the heart muscle. Beta-blockers are often used in patients with acute myocardial infarction. Previous meta-analyses on the topic have shown conflicting results ranging from harms, neutral effects, to benefits. No previous systematic review using Cochrane methodology has assessed the effects of beta-blockers for acute myocardial infarction.

OBJECTIVES

To assess the benefits and harms of beta-blockers compared with placebo or no intervention in people with suspected or diagnosed acute myocardial infarction.

SEARCH METHODS

We searched CENTRAL, MEDLINE, Embase, LILACS, Science Citation Index Expanded and BIOSIS Citation Index in June 2019. We also searched the WHO International Clinical Trials Registry Platform, ClinicalTrials.gov, Turning Research into Practice, Google Scholar, SciSearch, and the reference lists of included trials and previous reviews in August 2019.

SELECTION CRITERIA

We included all randomised clinical trials assessing the effects of beta-blockers versus placebo or no intervention in people with suspected or diagnosed acute myocardial infarction. Trials were included irrespective of trial design, setting, blinding, publication status, publication year, language, and reporting of our outcomes.

DATA COLLECTION AND ANALYSIS

We followed the Cochrane methodological recommendations. Four review authors independently extracted data. Our primary outcomes were all-cause mortality, serious adverse events according to the International Conference on Harmonization - Good Clinical Practice (ICH-GCP), and major adverse cardiovascular events (composite of cardiovascular mortality and non-fatal myocardial infarction during follow-up). Our secondary outcomes were quality of life, angina, cardiovascular mortality, and myocardial infarction during follow-up. Our primary time point of interest was less than three months after randomisation. We also assessed the outcomes at maximum follow-up beyond three months. Due to risk of multiplicity, we calculated a 97.5% confidence interval (CI) for the primary outcomes and a 98% CI for the secondary outcomes. We assessed the risks of systematic errors through seven bias domains in accordance to the instructions given in the Cochrane Handbook. The quality of the body of evidence was assessed by GRADE.

MAIN RESULTS

We included 63 trials randomising a total of 85,550 participants (mean age 57.4 years). Only one trial was at low risk of bias. The remaining trials were at high risk of bias. The quality of the evidence according to GRADE ranged from very low to high. Fifty-six trials commenced beta-blockers during the acute phase of acute myocardial infarction and seven trials during the subacute phase. At our primary time point 'less than three months follow-up', meta-analysis showed that beta-blockers versus placebo or no intervention probably reduce the risk of a reinfarction during follow-up (risk ratio (RR) 0.82, 98% confidence interval (CI) 0.73 to 0.91; 67,562 participants; 18 trials; moderate-quality evidence) with an absolute risk reduction of 0.5% and a number needed to treat for an additional beneficial outcome (NNTB) of 196 participants. However, we found little or no effect of beta-blockers when assessing all-cause mortality (RR 0.94, 97.5% CI 0.90 to 1.00; 80,452 participants; 46 trials/47 comparisons; high-quality evidence) with an absolute risk reduction of 0.4% and cardiovascular mortality (RR 0.99, 95% CI 0.91 to 1.08; 45,852 participants; 1 trial; moderate-quality evidence) with an absolute risk reduction of 0.4%. Regarding angina, it is uncertain whether beta-blockers have a beneficial or harmful effect (RR 0.70, 98% CI 0.25 to 1.84; 98 participants; 3 trials; very low-quality evidence) with an absolute risk reduction of 7.1%. None of the trials specifically assessed nor reported serious adverse events according to ICH-GCP. Only two trials specifically assessed major adverse cardiovascular events, however, no major adverse cardiovascular events occurred in either trial. At maximum follow-up beyond three months, meta-analyses showed that beta-blockers versus placebo or no intervention probably reduce the risk of all-cause mortality (RR 0.93, 97.5% CI 0.86 to 0.99; 25,210 participants; 21 trials/22 comparisons; moderate-quality evidence) with an absolute risk reduction of 1.1% and a NNTB of 91 participants, and cardiovascular mortality (RR 0.90, 98% CI 0.83 to 0.98; 22,457 participants; 14 trials/15 comparisons; moderate-quality evidence) with an absolute risk reduction of 1.2% and a NNTB of 83 participants. However, it is uncertain whether beta-blockers have a beneficial or harmful effect when assessing major adverse cardiovascular events (RR 0.81, 97.5% CI 0.40 to 1.66; 475 participants; 4 trials; very low-quality evidence) with an absolute risk reduction of 1.7%; reinfarction (RR 0.89, 98% CI 0.75 to 1.08; 6825 participants; 14 trials; low-quality evidence) with an absolute risk reduction of 0.9%; and angina (RR 0.64, 98% CI 0.18 to 2.0; 844 participants; 2 trials; very low-quality evidence). None of the trials specifically assessed nor reported serious adverse events according to ICH-GCP. None of the trials assessed quality of life. We identified two ongoing randomised clinical trials investigating the effect of early administration of beta-blockers after percutaneous coronary intervention or thrombolysis to patients with an acute myocardial infarction and one ongoing trial investigating the effect of long-term beta-blocker therapy.

AUTHORS' CONCLUSIONS

Our present review indicates that beta-blockers for suspected or diagnosed acute myocardial infarction probably reduce the short-term risk of a reinfarction and the long-term risk of all-cause mortality and cardiovascular mortality. Nevertheless, it is most likely that beta-blockers have little or no effect on the short-term risk of all-cause mortality and cardiovascular mortality. Regarding all remaining outcomes (serious adverse events according to ICH-GCP, major adverse cardiovascular events (composite of cardiovascular mortality and non-fatal myocardial infarction during follow-up), the long-term risk of a reinfarction during follow-up, quality of life, and angina), further information is needed to confirm or reject the clinical effects of beta-blockers on these outcomes for people with or suspected of acute myocardial infarction.

Do Patients need Lifelong β-Blockers after an Uncomplicated Myocardial Infarction?

The lifelong use of β-adrenoceptor antagonists (β-blockers) after a myocardial infarction (MI) has been the standard of care based on trials performed before the era of revascularization, when heart failure was common. Large randomized trials in the mid-1980s demonstrated that β-blockers played a major role in improving the in-hospital and long-term survival of patients admitted for MI. However, the implementation of rapid myocardial reperfusion led to a substantial survival benefit and a reduction of heart failure because of reduced infarct size. Modern large longitudinal registries did not provide sufficient evidence to support long-term β-blocker therapy in patients with uncomplicated acute MI. The long-term prescription of this therapy has become a matter of debate given the lack of contemporary evidence, frequent side effects, and treatment adherence issues. Furthermore, this shift into the reperfusion era led to a downgraded recommendation for the use of β-blockers in post-MI patients (class IIa B recommendation) in the 2017 European Society of Cardiology (ESC) recommendations for the treatment of ST-segment elevation MI (STEMI). Three large ongoing multicenter randomized trials (AβYSS, REDUCE-SWEDEHEART, and REBOOT-CNIC) are evaluating early discontinuation of β-blockers after an uncomplicated acute MI. The tested hypothesis is that β-blocker withdrawal is safe versus major adverse cardiovascular events and improves quality of life by reducing side effects. Thus, the present review summarizes the exhaustive evidence-based data for long-term β-blocker use after uncomplicated MI and the ongoing trials.

Early intravenous beta-blockers in patients undergoing primary percutaneous coronary intervention for ST-segment elevation myocardial infarction: A patient-pooled meta-analysis of randomized clinical trials

BACKGROUND

Conflicting evidence is available on the efficacy and safety of early intravenous beta-blockers before primary percutaneous coronary intervention for ST-segment elevation myocardial infarction. We performed a patient-pooled meta-analysis of trials comparing early intravenous beta-blockers with placebo or routine care in ST-segment elevation myocardial infarction patients undergoing primary percutaneous coronary intervention.

AIM

The aim of this study was to evaluate the clinical and safety outcomes of intravenous beta-blockers in ST-segment elevation myocardial infarction patients undergoing primary percutaneous coronary intervention.

METHODS

Four randomized trials with a total of 1150 patients were included. The main outcome was one-year death or myocardial infarction. Secondary outcomes included biomarker-based infarct size, left ventricular ejection fraction during follow-up, ventricular tachycardia, and a composite safety outcome (cardiogenic shock, symptomatic bradycardia, or hypotension) during hospitalization.

RESULTS

One-year death or myocardial infarction was similar among beta-blocker (4.2%) and control patients (4.4%) (hazard ratio: 0.96 (95% confidence interval: 0.53-1.75, p=0.90, I²=0%). No difference was observed in biomarker-based infarct size. One-month left ventricular ejection fraction was similar, but left ventricular ejection fraction at six months was significantly higher in patients treated with early intravenous beta-blockade (52.8% versus 50.0% in the control group, p=0.03). No difference was observed in the composite safety outcome or ventricular tachycardia during hospitalization.

CONCLUSION

In ST-segment elevation myocardial infarction patients undergoing primary percutaneous coronary intervention, the administration of early intravenous beta-blockers was safe. However, there was no difference in the main outcome of one-year death or myocardial infarction with early intravenous beta-blockers. A larger clinical trial is warranted to confirm the definitive efficacy of early intravenous beta-blockers.

Beta-blockers use from the general to the hemodialysis population

Beta-blockers have numerous indications in the general population and are strongly recommended in heart failure, post-myocardial infarction and arrhythmias. In hemodialysis patients, their use is based on weak evidence because of the lack of a sufficient number of randomized clinical trials. The strongest evidence is based on two trials. The first showed better survival with carvedilol in hemodialysis patients with four sessions per week and systolic heart failure. The second found reduced cardiovascular morbidity with atenolol compared to lisinopril in mostly black hypertensive hemodialysis patients. No clinical trials exist regarding myocardial infarction. Large retrospective studies have assessed the benefits of beta-blockers in hemodialysis. A large cohort of hemodialysis patients with new-onset heart failure showed better survival when treated with carvedilol, bisoprolol or metoprolol. Another recent one of 20,064 patients found out that metoprolol compared to carvedilol was associated with less all-cause mortality. There is still uncertainty also regarding the impact of dialysability of beta-blockers on patient's survival. On top of that, many observations suggested that beta-blockers were associated with a reduced rate of sudden cardiac death in hemodialysis patients but recent data show a link between bradycardia and sudden cardiac death questioning the benefit of beta-blockade in this population. Finally, what we know for sure so far is that beta-blockers should be avoided in patients with intradialytic hypotension associated with bradycardia.

Oxidation of ryanodine receptor after ischemia-reperfusion increases propensity of Ca2+ waves during β-adrenergic receptor stimulation

β-Adrenergic receptor (β-AR) activation produces the main positive inotropic response of the heart. During ischemia-reperfusion (I/R), however, β-AR activation can trigger life-threatening arrhythmias. Because I/R is frequently associated with oxidative stress, we investigated whether ryanodine receptor (RyR) oxidation contributes to proarrythmogenic Ca²⁺ waves during β-AR activation. Measurements of contractile and electrical activity from Langendorff-perfused rabbit hearts revealed that I/R produces tachyarrhythmias. Ventricular myocytes isolated from I/R hearts had an increased level of oxidized glutathione (i.e., oxidative stress) and a decreased level of free thiols in RyRs (i.e., RyR oxidation). Furthermore, myocytes from I/R hearts were characterized by increased sarcoplasmic reticulum (SR) Ca²⁺ leak and enhanced fractional SR Ca²⁺ release. In myocytes from nonischemic hearts, β-AR activation with isoproterenol (10 nM) produced only a positive inotropic effect, whereas in myocytes from ischemic hearts, isoproterenol at the same concentration triggered spontaneous Ca²⁺ waves. β-AR activation produced a similar effect on RyR phosphorylation in control and I/R myocytes. Treatment of myocytes from I/R hearts with the reducing agent mercaptopropionylglycine (100 μM) attenuated RyR oxidization and decreased Ca²⁺ wave frequency during β-AR activation. On the other hand, treatment of myocytes from nonischemic hearts with H₂O₂ (50 μM) increased SR Ca²⁺ leak and triggered Ca²⁺ waves during β-AR activation. Collectively, these results suggest that RyR oxidation after I/R plays a critical role in the transition from positive inotropic to arrhythmogenic effects during β-AR stimulation. Prevention of RyR oxidation can be a promising strategy to inhibit arrhythmias and preserve positive inotropic effect of β-AR activation during myocardial infarction. NEW & NOTEWORTHY Oxidative stress induced by ischemia plays a critical role in triggering arrhythmias during adrenergic stimulation. The combined increase in sarcoplasmic reticulum Ca²⁺ leak (because of ryanodine receptor oxidation) and sarcoplasmic reticulum Ca²⁺ load (because of adrenergic stimulation) can trigger proarrythmogenic Ca²⁺ waves. Restoring normal ryanodine receptor redox status can be a promising strategy to prevent arrhythmias and preserve positive inotropic effect of adrenergic stimulation during myocardial infarction.

Adrenergic Blockade Bi-directionally and Asymmetrically Alters Functional Brain-Heart Communication and Prolongs Electrical Activities of the Brain and Heart during Asphyxic Cardiac Arrest

Sudden cardiac arrest is a leading cause of death in the United States. The neurophysiological mechanism underlying sudden death is not well understood. Previously we have shown that the brain is highly stimulated in dying animals and that asphyxia-induced death could be delayed by blocking the intact brain-heart neuronal connection. These studies suggest that the autonomic nervous system plays an important role in mediating sudden cardiac arrest. In this study, we tested the effectiveness of phentolamine and atenolol, individually or combined, in prolonging functionality of the vital organs in CO₂-mediated asphyxic cardiac arrest model. Rats received either saline, phentolamine, atenolol, or phentolamine plus atenolol, 30 min before the onset of asphyxia. Electrocardiogram (ECG) and electroencephalogram (EEG) signals were simultaneously collected from each rat during the entire process and investigated for cardiac and brain functions using a battery of analytic tools. We found that adrenergic blockade significantly suppressed the initial decline of cardiac output, prolonged electrical activities of both brain and heart, asymmetrically altered functional connectivity within the brain, and altered, bi-directionally and asymmetrically, functional, and effective connectivity between the brain and heart. The protective effects of adrenergic blockers paralleled the suppression of brain and heart connectivity, especially in the right hemisphere associated with central regulation of sympathetic function. Collectively, our results demonstrate that blockade of brain-heart connection via alpha- and beta-adrenergic blockers significantly prolonged the detectable activities of both the heart and the brain in asphyxic rat. The beneficial effects of combined alpha and beta blockers may help extend the survival of cardiac arrest patients.

β-Adrenergic Inhibition Prevents Action Potential and Calcium Handling Changes during Regional Myocardial Ischemia

β-adrenergic receptor (β-AR) blockers may be administered during acute myocardial infarction (MI), as they reduce energy demand through negative chronotropic and inotropic effects and prevent ischemia-induced arrhythmogenesis. However, the direct effects of β-AR blockers on ventricular electrophysiology and intracellular Ca²⁺ handling during ischemia remain unknown. Using optical mapping of transmembrane potential (with RH237) and sarcoplasmic reticulum (SR) Ca²⁺ (with the low-affinity indicator Fluo-5N AM), the effects of 15 min of regional ischemia were assessed in isolated rabbit hearts (n = 19). The impact of β-AR inhibition on isolated hearts was assessed by pre-treatment with 100 nM propranolol (Prop) prior to ischemia (n = 7). To control for chronotropy and inotropy, hearts were continuously paced at 3.3 Hz and contraction was inhibited with 20 μM blebbistatin. Untreated ischemic hearts displayed prototypical shortening of action potential duration (APD₈₀) in the ischemic zone (IZ) compared to the non-ischemic zone (NI) at 10 and 15 min ischemia, whereas APD shortening was prevented with Prop. Untreated ischemic hearts also displayed significant changes in SR Ca²⁺ handling in the IZ, including prolongation of SR Ca²⁺ reuptake and SR Ca²⁺ alternans, which were prevented with Prop pre-treatment. At 5 min ischemia, Prop pre-treated hearts also showed larger SR Ca²⁺ release amplitude in the IZ compared to untreated hearts. These results suggest that even when controlling for chronotropic and inotropic effects, β-AR inhibition has a favorable effect during acute regional ischemia via direct effects on APD and Ca²⁺ handling.

Prognostic Benefit of Beta-blockers After Acute Coronary Syndrome With Preserved Systolic Function. Still Relevant Today?

INTRODUCTION AND OBJECTIVES

The scientific evidence for using beta-blockers after acute coronary syndrome stems from studies conducted in the days before coronary revascularization and in patients with ventricular dysfunction. The aim of this study was to analyze the current long-term prognostic benefit of beta-blockers in patients with acute coronary syndrome and preserved left ventricular ejection fraction.

METHODS

We conducted a retrospective cohort study of 3236 patients with acute coronary syndrome and left ventricular ejection fraction ≥ 50%. We performed a propensity-matched analysis to draw up two groups of 555 patients paired according to whether or not they had been treated with beta-blockers. The prognostic value of beta-blockers to predict mortality during follow-up was analyzed using Cox regression.

RESULTS

During the follow-up (median, 5.2 years), 506 patients (15.6%) died. Patients treated with beta-blockers (n=2277 [70.4%]) had a lower mortality rate (11.6% vs 25.2%; P<.001). After propensity score matching, we found that mortality during follow-up was still lower in the beta-blocker group (14.4% vs 18.9%; P=.020). Therefore, this treatment was an independent protective factor after adjusting for confounding variables in the multivariate Cox regression analysis (hazard ratio=0.64; 95% confidence interval, 0.48-0.87; P=.004).

CONCLUSIONS

Beta-blocker treatment in patients with acute coronary syndrome and preserved left ventricular ejection fraction is associated with lower long-term mortality.

Protective and pathological roles of tissue factor in the heart

Tissue factor (TF) is expressed in the heart where it is required for haemostasis. High levels of TF are also expressed in atherosclerotic plaques and likely contribute to atherothrombosis after plaque rupture. Indeed, risk factors for atherothrombosis, such as diabetes, hypercholesterolaemia, smoking and hypertension, are associated with increased TF expression in circulating monocytes, microparticles and plasma. Several therapies that reduce atherothrombosis, such as statins, ACE inhibitors, beta-blockers and anti-platelet drugs, are associated with reduced TF expression. In addition to its haemostatic and pro-thrombotic functions, the TF : FVIIa complex and downstream coagulation proteases activate cells by cleavage of protease-activated receptors (PARs). In mice, deficiencies in either PAR-1 or PAR-2 reduce cardiac remodelling and heart failure after ischaemia-reperfusion injury. This suggests that inhibition of coagulation proteases and PARs may be protective in heart attack patients. In contrast, the TF/thrombin/PAR-1 pathway is beneficial in a mouse model of Coxsackievirus B3-induced viral myocarditis. We found that stimulation of PAR-1 increases the innate immune response by enhancing TLR3-dependent IFN-β expression. Therefore, inhibition of the TF/thrombin/PAR-1 pathway in patients with viral myocarditis could have detrimental effects.

CONCLUSION

The TF : FVIIa complex has both protective and pathological roles in the heart.

Clinical outcomes with β-blockers for myocardial infarction: a meta-analysis of randomized trials

BACKGROUND

Debate exists about the efficacy of β-blockers in myocardial infarction and their required duration of usage in contemporary practice.

METHODS

We conducted a MEDLINE/EMBASE/CENTRAL search for randomized trials evaluating β-blockers in myocardial infarction enrolling at least 100 patients. The primary outcome was all-cause mortality. Analysis was performed stratifying trials into reperfusion-era (> 50% undergoing reperfusion or receiving aspirin/statin) or pre-reperfusion-era trials.

RESULTS

Sixty trials with 102,003 patients satisfied the inclusion criteria. In the acute myocardial infarction trials, a significant interaction (Pinteraction = .02) was noted such that β-blockers reduced mortality in the pre-reperfusion (incident rate ratio [IRR] 0.86; 95% confidence interval [CI], 0.79-0.94) but not in the reperfusion era (IRR 0.98; 95% CI, 0.92-1.05). In the pre-reperfusion era, β-blockers reduced cardiovascular mortality (IRR 0.87; 95% CI, 0.78-0.98), myocardial infarction (IRR 0.78; 95% CI, 0.62-0.97), and angina (IRR 0.88; 95% CI, 0.82-0.95), with no difference for other outcomes. In the reperfusion era, β-blockers reduced myocardial infarction (IRR 0.72; 95% CI, 0.62-0.83) (number needed to treat to benefit [NNTB] = 209) and angina (IRR 0.80; 95% CI, 0.65-0.98) (NNTB = 26) at the expense of increase in heart failure (IRR 1.10; 95% CI, 1.05-1.16) (number needed to treat to harm [NNTH] = 79), cardiogenic shock (IRR 1.29; 95% CI, 1.18-1.41) (NNTH = 90), and drug discontinuation (IRR 1.64; 95% CI, 1.55-1.73), with no benefit for other outcomes. Benefits for recurrent myocardial infarction and angina in the reperfusion era appeared to be short term (30 days).

CONCLUSIONS

In contemporary practice of treatment of myocardial infarction, β-blockers have no mortality benefit but reduce recurrent myocardial infarction and angina (short-term) at the expense of increase in heart failure, cardiogenic shock, and drug discontinuation. The guideline authors should reconsider the strength of recommendations for β-blockers post myocardial infarction.

Left renal nerves stimulation facilitates ischemia-induced ventricular arrhythmia by increasing nerve activity of left stellate ganglion

INTRODUCTION

Renal sympathetic nerve (RSN) activity plays a key role in systemic sympathetic hyperactivity. Previous studies have shown that cardiac sympathetic hyperactivity, especially the left stellate ganglion (LSG), contributes to the pathogenesis of ventricular arrhythmias (VAs) after acute myocardial infarction (AMI).

METHODS AND RESULTS

Twenty-eight dogs received 3 hours of continuous left-sided electrical stimulation of RSN (LRS; Group-1, n = 9), sham RSN stimulation (Group-2, n = 9), or LSG ablation plus 3 hours of LRS (Group-3, n = 10) were included. AMI was induced by ligating the proximal left anterior descending coronary artery. LRS was performed using electrical stimulation on the adventitia of left renal artery at the voltage increasing the systolic blood pressure (BP) by 10%. BP, heart rate variability (HRV), serum norepinephrine (NE) level, and LSG function were measured at baseline and the end of each hour of LRS. C-fos and nerve growth factor (NGF) protein expressed in the LSG were examined in Group-1 and Group-2. Compared with baseline, 3 hours of LRS induced a significant increase in BP, sympathetic indices of HRV, serum NE level, and LSG function. The incidence of VAs in Group-1 was significantly higher than other groups. The expression of c-fos and NGF protein in the LSG was significantly higher in Group-1 than Group-2.

CONCLUSION

Three hours of LRS induces both systemic and cardiac sympathetic hyperactivity and increases the incidence of ischemia-induced VAs.

Beta-blocker use in ST-segment elevation myocardial infarction in the reperfusion era (GRACE)

BACKGROUND

Current guidelines recommend early oral beta-blocker administration in the management of acute coronary syndromes for patients who are not at high risk of complications.

METHODS

Data from patients enrolled between 2000 and 2007 in the Global Registry of Acute Coronary Events (GRACE) were used to evaluate hospital outcomes in 3 cohorts of patients admitted with ST-elevation myocardial infarction, based on beta-blocker use (early [first 24 hours] intravenous (IV) [± oral], only early oral, or delayed [after first 24 hours]).

RESULTS

Among 13,110 patients with ST-elevation myocardial infarction, 21% received any early IV beta-blockers, 65% received only early oral beta-blockers, and 14% received delayed (>24 hours) beta-blockers. Higher systolic blood pressure, higher heart rate, and chronic beta-blocker use were independent predictors of early beta-blocker use. Early beta-blocker use was less likely in older patients, patients with moderate to severe left ventricular dysfunction, and in those presenting with inferior myocardial infarction or Killip class II or III heart failure. IV beta-blocker use and delayed beta-blocker use were associated with higher rates of cardiogenic shock, sustained ventricular fibrillation/ventricular tachycardia, and acute heart failure, compared with oral beta-blocker use. In-hospital mortality was increased with IV beta-blocker use (propensity score adjusted odds ratio, 1.41; 95% confidence interval, 1.03-1.92) but significantly reduced with delayed beta-blocker administration (propensity adjusted odds ratio, 0.44; 95% confidence interval, 0.26-0.74).

CONCLUSIONS

Early beta-blocker use is common in patients presenting with ST-elevation myocardial infarction, with oral administration being the most prevalent. Oral beta-blockers were associated with a decrease in the risk of cardiogenic shock, ventricular arrhythmias, and acute heart failure. However, the early receipt of any form of beta-blockers was associated with an increase in hospital mortality.

Beta blocker use after acute myocardial infarction in the patient with normal systolic function: when is it "ok" to discontinue?

Beta-Blockers [BB] have been used extensively in the last 40 years after acute myocardial infarction [AMI] as part of therapy and in secondary prevention. The evidence for “routine” therapy with beta-blocker use post AMI rests largely on results of trials conducted over 25 years ago. However, there remains no clear recommendation regarding the appropriate duration of treatment with BBs in post AMI patients with normal left ventricular ejection fraction [LVEF] who are not experiencing angina, or who require BB for hypertension or dysrhythmia. Based on the latest ACC/AHA guidelines, BBs are recommended for early use in the setting of AMI, except in patients who are at low risk and then indefinitely as secondary prevention after AMI. This recommendation was downgraded to class IIa in low risk patients and the updated 2007 ACC/AHA guidelines suggest that the rationale for BB for secondary prevention is from limited data derived from extrapolations of chronic angina and heart failure trials. In this review, we examine the key trials that have shaped the current guidelines and recommendations. In addition, we attempt to answer the question of the duration of BB use in patients with preserved LVEF after acute MI, as well as which subgroups of patients benefits most from post AMI use of beta blockers.

Pharmacology of antiarrhythmic drugs in elderly patients

Bradyarrhythmias and tachyarrhythmias are common in elderly patients as a result of aging and acquired cardiac disease. Antiarrhythmic drugs are effective in elderly patients for the management of supraventricular and ventricular arrhythmias; however, dosing of drugs must be performed with care because of age-related changes in drug pharmacokinetics, the presence of concomitant disease, and frequent drug-drug interactions. Despite the large number of antiarrhythmic drugs having different electrophysiologic actions, as described in this article, only the β-blockers have been shown to be effective in reducing mortality and to lack proarrhythmic actions.

Early intravenous beta-blockers in patients with acute coronary syndrome--a meta-analysis of randomized trials

BACKGROUND

Intravenous (IV) beta-blockade is currently a Class IIa recommendation in early management of patients with acute coronary syndromes (ACS) without obvious contraindications.

METHODS

We searched the PubMed, EMBASE and the Cochrane Register for Controlled Clinical Trials for randomized clinical trials from 1965 through December, 2011, comparing intravenous beta-blockers administered within 12 hours of presentation of ACS with standard medical therapy and/or placebo. The primary outcome assessed was the risk of short-term (in-hospital mortality-with maximum follow up duration of 90 days) all-cause mortality in the intervention group versus the comparator group. The secondary outcomes assessed were ventricular tachyarrhythmias, myocardial reinfarction, cardiogenic shock, and stroke. Pooled treatment effects were estimated using relative risk with Mantel-Haenszel risk ratio, using a random-effects model.

RESULTS

Sixteen studies enrolling 73,396 participants met the inclusion ⁄ exclusion criteria. In- hospital mortality was reduced 8% with intravenous beta-blockers, RR=0.92 (95% CI, 0.86-1.00; p=0.04) when compared with controls. Moreover, intravenous beta-blockade reduced the risk of ventricular tachyarrhythmias (RR=0.61; 95 % CI 0.47-0.79; p=0.0003) and myocardial reinfarction (RR=0.73, 95 % CI 0.59-0.91; p=0.004) without increase in the risk of cardiogenic shock, (RR=1.02; 95% CI 0.77-1.35; p=0.91) or stroke (RR=0.58; 95 % CI 0.17-1.98; p=0.38).

CONCLUSIONS

Intravenous beta-blockers early in the course of appropriate patients with ACS appears to be associated with significant reduction in the risk of short-term cardiovascular outcomes, including a reduction in the risk of all-cause mortality.

A review and meta-analysis of studies on the effect and timing of β-blocker administration in patients with ST-segment elevation myocardial infarction

The utility of β-blockers during an evolving ST-segment elevation myocardial infarction (STEMI) has substantial theoretic physiological backing. This coupled with early successes using β-blockers in STEMI promulgated multiple guidelines expanding the use of this class of medication to all patients with acute coronary syndromes. However, recent studies have questioned the utility of β-blockers in the emergency department in these patients. The purpose of this article is to review the evidence behind the use of β-blockers in the emergency department for STEMI patients.

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.

Targeted ablation of cardiac sympathetic neurons reduces the susceptibility to ischemia-induced sustained ventricular tachycardia in conscious rats

The Cardiac Arrhythmia Suppression Trial demonstrated that antiarrhythmic drugs not only fail to prevent sudden cardiac death, but actually increase overall mortality. These findings have been confirmed in additional trials. The "proarrhythmic" effects of most currently available antiarrhythmic drugs makes it essential that we investigate novel strategies for the prevention of sudden cardiac death. Targeted ablation of cardiac sympathetic neurons may become a therapeutic option by reducing sympathetic activity. Thus cholera toxin B subunit (CTB) conjugated to saporin (a ribosomal inactivating protein that binds to and inactivates ribosomes; CTB-SAP) was injected into both stellate ganglia to test the hypothesis that targeted ablation of cardiac sympathetic neurons reduces the susceptibility to ischemia-induced, sustained ventricular tachycardia in conscious rats. Rats were randomly divided into three groups: 1) control (no injection); 2) bilateral stellate ganglia injection of CTB; and 3) bilateral stellate ganglia injection of CTB-SAP. CTB-SAP rats had a reduced susceptibility to ischemia-induced, sustained ventricular tachycardia. Associated with the reduced susceptibility to ventricular arrhythmias were a reduced number of stained neurons in the stellate ganglia and spinal cord (segments T(1)-T(4)), as well as a reduced left ventricular norepinephrine content and sympathetic innervation density. Thus CTB-SAP retrogradely transported from the stellate ganglia is effective at ablating cardiac sympathetic neurons and reducing the susceptibility to ventricular arrhythmias.

Does the early administration of beta-blockers improve the in-hospital mortality rate of patients admitted with acute coronary syndrome?

OBJECTIVES

Beta-blockade is currently recommended in the early management of patients with acute coronary syndromes (ACS). This was a systematic review of the medical literature to determine if early beta-blockade improves the outcome of patients with ACS.

METHODS

The authors searched the PubMed and EMBASE databases for randomized controlled trials from 1965 through May 2009 using a search strategy derived from the following PICO formulation of our clinical question: Patients included adults (18+ years) with an acute or suspected myocardial infarction (MI) within 24 hours of onset of chest pain. Intervention included intravenous or oral beta-blockers administered within 8 hours of presentation. The comparator included standard medical therapy with or without placebo versus early beta-blocker administration. The outcome was the risk of in-hospital death in the intervention groups versus the comparator groups. The methodologic quality of the studies was assessed. Qualitative methods were used to summarize the study results. In-hospital mortality rates were compared using a forest plot of relative risk (RR; 95% confidence interval [CI]) between beta-blockers and controls. Statistical analysis was done with Review Manager V5.0.

RESULTS

Eighteen articles (total N = 72,249) met the inclusion/exclusion criteria. For in-hospital mortality, RR = 0.95 (95% CI, 0.90-1.01). In the largest of these studies (n = 45,852), a significantly higher rate (p < 0.0001) of cardiogenic shock was observed in the beta-blocker (5.0%) versus control group (3.9%).

CONCLUSIONS

This systematic review failed to demonstrate a convincing in-hospital mortality benefit for using beta-blockers early in the course of patients with an acute or suspected MI.

Effect of early treatment with anti-hypertensive drugs on short and long-term mortality in patients with an acute cardiovascular event

BACKGROUND

Acute cardiovascular events represent a therapeutic challenge. Blood pressure lowering drugs are commonly used and recommended in the early phase of these settings. This review analyses randomized controlled trial (RCT) evidence for this approach.

OBJECTIVES

To determine the effect of immediate and short-term administration of anti-hypertensive drugs on all-cause mortality, total non-fatal serious adverse events (SAE) and blood pressure, in patients with an acute cardiovascular event, regardless of blood pressure at the time of enrollment.

SEARCH STRATEGY

MEDLINE, EMBASE, and Cochrane clinical trial register from Jan 1966 to February 2009 were searched. Reference lists of articles were also browsed. In case of missing information from retrieved articles, authors were contacted.

SELECTION CRITERIA

Randomized controlled trials (RCTs) comparing anti-hypertensive drug with placebo or no treatment administered to patients within 24 hours of the onset of an acute cardiovascular event.

DATA COLLECTION AND ANALYSIS

Two reviewers independently extracted data and assessed risk of bias. Fixed effects model with 95% confidence intervals (CI) were used. Sensitivity analyses were also conducted.

MAIN RESULTS

Sixty-five RCTs (N=166,206) were included, evaluating four classes of anti-hypertensive drugs: ACE inhibitors (12 trials), beta-blockers (20), calcium channel blockers (18) and nitrates (18). Acute stroke was studied in 6 trials (all involving CCBs). Acute myocardial infarction was studied in 59 trials. In the latter setting immediate nitrate treatment (within 24 hours) reduced all-cause mortality during the first 2 days (RR 0.81, 95%CI [0.74,0.89], p<0.0001). No further benefit was observed with nitrate therapy beyond this point. ACE inhibitors did not reduce mortality at 2 days (RR 0.91,95%CI [0.82, 1.00]), but did after 10 days (RR 0.93, 95%CI [0.87,0.98] p=0.01). No other blood pressure lowering drug administered as an immediate treatment or short-term treatment produced a statistical significant mortality reduction at 2, 10 or >/=30 days. There was not enough data studying acute stroke, and there were no RCTs evaluating other acute cardiovascular events.

AUTHORS' CONCLUSIONS

Nitrates reduce mortality (4-8 deaths prevented per 1000) at 2 days when administered within 24 hours of symptom onset of an acute myocardial infarction. No mortality benefit was seen when treatment continued beyond 48 hours. Mortality benefit of immediate treatment with ACE inhibitors post MI at 2 days did not reach statistical significance but the effect was significant at 10 days (2-4 deaths prevented per 1000). There is good evidence for lack of a mortality benefit with immediate or short-term treatment with beta-blockers and calcium channel blockers for acute myocardial infarction.

Clinical Review: Is the Perioperative Use of β-Blockers Still Recommended? A Critical Review of Recent Controversies

The optimal role of β-adrenergic receptor blockade in the perioperative period remains unclear in patients at risk for cardiovascular events. Cardiovascular complications continue to be the most common cause of perioperative morbidity and mortality, and cardioprotective properties of β-blockers are widely recognized, yet the results of the clinical trials investigating the use of different β-blockers in the perioperative period are controversial. The discrepancy might be related to differences in the design of studies, use of different agents, administration by different routes, and continuation for different time intervals. Evidently, perioperative mortality and morbidity seem to be related to heart rate, and the majority of complications are related to β-blockers’ side effects. Based on the observations from different studies, we propose an algorithm for perioperative β blockade.

Use of beta-blockers and effects on heart rate and blood pressure post-acute coronary syndromes: are we on target?

BACKGROUND

beta-blockers have been shown to benefit patients after myocardial infarction by decreasing mortality, sudden cardiac death, and reinfarction. Although beta-blockers are recommended for all patients with acute coronary syndromes (ACS) without contraindications, a target heart rate (HR) is recommended only for patients with unstable angina/non ST-elevation myocardial infarction. A contemporary series documenting trends in beta-blocker usage and achieved HR and blood pressures (BP) is not available. The study objectives were to monitor trends in HR and BP in relation to beta-blocker use in a contemporary series of patients with ACS.

METHODS

In this observational study, 300 consecutive patients with proven ACS had HR and BP values collected hourly from admission until hospital discharge and averaged at multiple intervals throughout hospital stay. Data on baseline demographic characteristics, beta-blocker doses, and titration schedules, procedures performed, cardiac regimens, concurrent medical issues, and contraindications to therapy were collected.

RESULTS

Only 5.3% achieved an average HR of 50 to 60 beat/min throughout the hospital stay. Overall, the average HR was 74 beat/min and average BP was 115/64 mm Hg. Admission daily doses of metoprolol averaged 58 mg compared to discharge daily doses of 88 mg; only 52% of patients had dosage increases.

CONCLUSIONS

Although effective levels of BP were maintained during hospitalization for an ACS, target HRs were generally not achieved. Future studies are needed to determine the relationship between treatment objectives and clinical outcomes in the present era of ACS management.

Cardiac autonomic neural remodeling and susceptibility to sudden cardiac death: effect of endurance exercise training

Sudden cardiac death resulting from ventricular tachyarrhythmias remains the leading cause of death in industrially developed countries, accounting for between 300,000 and 500,000 deaths each year in the United States. Yet, despite the enormity of this problem, both the identification of factors contributing to ventricular fibrillation as well as the development of safe and effective antiarrhythmic agents remain elusive. Subnormal cardiac parasympathetic regulation coupled with an elevated cardiac sympathetic activation may allow for the formation of malignant ventricular arrhythmias. In particular, myocardial infarction can reduce cardiac parasympathetic regulation and alter beta-adrenoceptor subtype expression enhancing beta(2)-adrenoceptor sensitivity that can lead to intracellular calcium dysregulation and arrhythmias. As such, myocardial infarction can induce a remodeling of cardiac autonomic regulation that may be required to maintain cardiac pump function. If alterations in cardiac autonomic regulation play an important role in the genesis of life-threatening arrhythmias, then one would predict that interventions designed to either augment parasympathetic activity and/or reduce cardiac adrenergic activity would also protect against ventricular fibrillation. Recently, studies using a canine model of sudden death demonstrate that endurance exercise training (treadmill running) enhanced cardiac parasympathetic regulation (increased heart rate variability), restored a more normal beta-adrenoceptor balance (i.e., reduced beta(2)-adrenoceptor sensitivity and expression), and protected against ventricular fibrillation induced by acute myocardial ischemia. Thus exercise training may reverse the autonomic neural remodeling induced by myocardial infarction and thereby enhance the electrical stability of the heart in individuals shown to be at an increased risk for sudden cardiac death.

Treatment of ventricular arrhythmias in the elderly

Underlying causes of ventricular tachycardia (VT) or complex ventricular arrhythmias (VA) should be treated if possible. Antiarrhythmic drugs should not be administered to treat asymptomatic individuals with complex VA and no heart disease. Beta-blockers are the only antiarrhythmic drugs that have been documented to reduce mortality in patients with VT or complex VA. Radiofrequency catheter ablation of VT has been beneficial in treating selected patients with arrhythmogenic foci of monomorphic VT. The automatic implantable cardioverter-defibrillator (AICD) is the most effective treatment for patients with life-threatening VT or ventricular fibrillation. Patients with AICDs should be treated with biventricular pacing, not with dual-chamber rate-responsive pacing at a rate of 70/min. Patients with AICDs should also be treated with beta-blockers, statins, and angiotensin-converting enzyme inhibitors or angiotensin blockers.

Adjunctive therapy after reperfusion therapy in acute myocardial infarction

The current era has witnessed dramatic improvement in the treatment of acute myocardial infarction, due in large part to the more widespread use of thrombolytic therapy aimed at quickly restoring perfusion in the infarct-related artery. This review addresses the role of adjunctive pharmacologic therapy in the thrombolytic era, recognizing that much of the available clinical trial data supporting the role of adjunctive pharmacologic treatment strategies was conducted in patient populations not widely exposed to reperfusion therapy. This review, therefore, explores the data supporting the incremental benefit of therapy with beta blockers, nitrates, angiotensin-converting enzyme inhibitors, or magnesium in addition to thrombolytic therapy. Heparin and aspirin will not be discussed.

Role of drug therapy for sustained ventricular tachyarrhythmias

Antiarrhythmic drug therapy, broadly defined, is the mainstay of treatment and prevention of ventricular tachycardia (VT)/ventricular fibrillation (VF), which can lead to sudden death. This article evaluates the evidence for and appropriate use of class I antiarrhythmic drugs, class III antiarrhythmic drugs, beta-blockers, nondihydropyridine calcium-channel blockers, statins, angiotensin enzyme inhibitors, angiotensin receptor blockers, aldosterone blockers, and digoxin for antiarrhythmic benefits in patients who have a propensity for VT/VF and therefore are at risk of sudden death.

β-Blockers for the treatment of cardiac arrest from ventricular fibrillation?

More than 160,000 people suffer sudden cardiac death each year in the US. It is estimated that ventricular fibrillation (VF) is the initial rhythm in approximately 30% of these cases. Ventricular fibrillation that does not respond to the first few defibrillation attempts is associated with mortality rates of up to 97%. Currently, no pharmacological intervention has been shown to increase long-term survival in patients with shock-refractory VF. The purpose of this review article is to evaluate whether beta-blocker administration during the resuscitation of cardiac arrest from VF or pulseless ventricular tachycardia (VT) improves outcome. We searched the MEDLINE and EMBASE databases for human clinical trials, animal experimental trials, review articles, case reports and abstracts published between 1966 and September 2006. No human prospective randomized controlled trial has studied the effects of beta-blocker administration during VF directly. Prospective trials of anti-arrhythmics with beta-blocking properties have been published, as well as several case reports/case series and experimental animal studies. The evidence thus far suggests that beta-blockade during resuscitation from VF may be associated with increasing rates of resuscitation, greater post-resuscitation survival, and improved post-resuscitation myocardial function. These positive effects on outcome may be mediated by a decrease in the oxygen requirements of the fibrillating heart, thus improving the overall balance between myocardial oxygen supply and demand during resuscitation. While no significant detrimental effects directly related to low dose beta-blockade during VF have been reported in the studies reviewed, concerns relating to possible loss of myocardial contractility and hypotension remain. To this day, high quality human trials are lacking. Preliminary human studies are needed to assess the effects of beta-blockers in the treatment of cardiac arrest from ventricular fibrillation or pulseless VT further.

Cardiovascular drug therapy in the elderly

Pharmacokinetic considerations in the elderly include absorption, bioavailablility, drug distribution, half-life, drug metabolism, and drug excretion. There are numerous physiologic changes with aging that affect pharmacodynamics with alterations in end-organ responsiveness. This article discusses use of cardiovascular drugs in the elderly including digoxin, diuretics, beta-adrenergic blockers, angiotensin-converting enzyme inhibitors, angiotensin-II receptor blockers, nitrates, calcium channel blockers, alpha-adrenergic blockers, antiarrhythmic drugs, lipid-lowering drugs, and anticoagulants. This article also discusses the adverse effects of cardiovascular drugs in the elderly, medications best to avoid in the elderly, and the prudent use of medications in the elderly.

Beta blockers as anti-arrhythmic agents

Although beta-adrenergic blocking agents are not always considered anti-arrhythmic drugs, the results of several recent trials have suggested an anti-arrhythmic mechanism for at least part of their mortality benefit in the treatment of chronic congestive heart failure. We review background experimental and clinical evidence for the anti-arrhythmic actions of beta-blockers and then review the results of published beta-blocker heart failure trials. A majority of trials showed improvement in overall survival as well as reduction in sudden death and ventricular arrhythmias with beta-blocker treatment. Although different effects were seen with different specific agents, these trials overall support a clinically significant anti-arrhythmic effect of several beta-blockers.

Ventricular fibrillation in acute myocardial infarction before and during primary PCI

BACKGROUND

There are scarce and sometimes contradictory data about ventricular fibrillation (VF) during the acute phase of MI. In-hospital VF most often occurs with inferior MI, when treated with fibrinolytics. Out-of-hospital VF seems to be associated with anterior MI. We studied characteristics of patients with VF during reperfusion therapy by primary angioplasty (PCI) versus patients with VF before PCI.

METHODS

From January 1995 until December 2001, we treated 2826 patients for acute MI and reviewed clinical records of all patients who developed VF and classified the patients according to the first episode of VF: either before or during the angioplasty procedure.

RESULTS

VF developed in 219 (8%) patients. Patients with VF during reperfusion therapy (n=74, 3%) were older (p=0.03), more frequently female (0.04), less often had heart failure (p=0.04), when compared with patient with VF before PCI (n=145, 5%). Patients with VF during PCI experienced more often preinfarction angina (p=0.009) and suffered more often from inferior MI (p=0.001), when compared with patients with VF before PCI.

CONCLUSIONS

Patients with early VF before reperfusion have different characteristics when compared with patients with VF during reperfusion. Infarct location is a major determinant of timing of VF, when both groups are compared (p<0.001).

Arrhythmic complications of acute coronary syndromes

Cardiac arrhythmias routinely manifest during or following an acute coronary syndrome (ACS). Although the incidence of arrhythmia is directly related to the type of ACS the patient is experiencing, the clinician needs to be cautious with all patients in these categories. As an example, nearly 90% of patients who experience acute myocardial infarction (AMI) develop some cardiac rhythm abnormality and 25% have a cardiac conduction disturbance within 24 hours of infarct onset. In this patient population, the incidence of serious arrhythmias, such as ventricular fibrillation (4.5%) ,is greatest in the first hour of an AMI and declines rapidly thereafter. This article addresses the identification and treatment of arrhythmias and conduction disturbances that complicate the course of patients who have ACS, particularly AMI and thrombolysis. Emphasis is placed on mechanisms and therapeutic strategies.

The cardiovascular implications of hypokalemia

The role of potassium in the progression of cardiovascular disease is complex and controversial. Animal and human data suggest that increases in dietary potassium, decreases in urinary potassium loss, or increases in serum potassium levels through other mechanisms have benefits in several disease states. These include the treatment of hypertension, stroke prevention, arrhythmia prevention, and treatment of congestive heart failure. Recently, the discovery that aldosterone antagonists not only decrease sodium reabsorption and decrease potassium secretion in the nephron, but also decrease pathological injury of such nonepithelial tissues as the myocardium and endothelium, has generated great controversy regarding the actual mechanisms of benefit of these agents. We review the available data and draw conclusions about the relative benefits of modulating potassium balance versus nonrenal effects of aldosterone blockade in patients with cardiovascular disease.

Management of the Elderly Person After Myocardial Infarction

Elderly persons after myocardial infarction should have their modifiable coronary artery risk factors intensively treated. Hypertension should be treated with beta blockers and angiotensin-converting enzyme inhibitors. The blood pressure should be reduced to &lt;140/85 mmHg and to ≥130/80 mmHg in persons with diabetes or renal insufficiency. The serum low-density lipoprotein cholesterol should be reduced to &lt;100 mg/dl with statins if necessary. Aspirin or clopidogrel, beta blockers, and angiotensin-converting enzyme inhibitors should be given indefinitely unless contraindications exist to the use of these drugs. Long-acting nitrates are effective antianginal and antiischemic drugs. There are no Class I indications for the use of calcium channel blockers after myocardial infarction. Postinfarction patients should not receive Class I antiarrhythmic drugs, sotalol, or amiodarone. An automatic implantable cardioverter-defibrillator should be implanted in postinfarction patients at very high risk for sudden cardiac death. Hormonal therapy should not be used in postmenopausal women after myocardial infarction. The two indications for coronary revascularization are prolongation of life and relief of unacceptable symptoms despite optimal medical management.

Effects of prior beta-blocker therapy on clinical outcomes after primary coronary angioplasty for acute myocardial infarction

We hypothesized that pretreatment with beta blockers may improve clinical outcomes after primary angioplasty for acute myocardial infarction. We pooled clinical, angiographic, and outcomes data on 2,537 patients enrolled in the Primary Angioplasty in Myocardial Infarction (PAMI), PAMI-2, and Stent PAMI trials. We classified patients into a beta group (n = 1,132) if they received beta-blocker therapy before primary angioplasty or a no-beta group (n = 1,405) if they did not. We evaluated procedural complications and in-hospital and 1-year outcomes (death and major adverse cardiac events [death, reinfarction, target vessel revascularization, or stroke]) between groups. Beta patients were younger, had higher systolic blood pressure and heart rate, and were more likely to be in Killip class I at admission. They had lower left ventricular ejection fraction, greater door-to-balloon time, greater likelihood of having a left anterior descending artery culprit lesion, but a similar incidence of Thrombolysis In Myocardial Infarction 3 flow after angioplasty (92.6% vs 92.7%, p = 0.91). The beta group had less procedural complications (23% vs 34%, p <0.0001) and a lower incidence of death (1.8% vs 3.7%, p = 0.0035) and major adverse cardiac events (5.5% vs 7.8%, p = 0.027) during hospitalization. At 1 year, mortality remained lower in beta patients (4.9% vs 6.7%, log-rank p = 0.055). After adjustment for baseline differences, beta patients had significantly lower in-hospital mortality (odds ratio 0.41; 95% confidence interval 0.20 to 0.84; p <0.0148) and nonsignificantly lower 1-year mortality (odds ratio 0.72; 95% confidence interval 0.47 to 1.08; p = 0.11). Thus, pretreatment with beta blockers has an independent beneficial effect on short-term clinical outcomes in patients undergoing primary angioplasty for acute myocardial infarction.

Aerobic exercise conditioning: a nonpharmacological antiarrhythmic intervention

Sudden, unexpected cardiac death due to ventricular fibrillation is the leading cause of death in most industrially developed countries. Yet, despite the enormity of this problem, the development of safe and effective antiarrhythmic therapies has proven to be an elusive goal. In fact, many initially promising antiarrhythmic medications were subsequently found to increase rather than to decrease cardiac mortality. It is now known that cardiac disease alters cardiac autonomic balance and that the patients with the greatest changes in this cardiac neural regulation (i.e., decreased parasympathetic coupled with increased sympathetic activity) are also the patients at the greatest risk for sudden death. A growing body of experimental and epidemiological data demonstrates that aerobic exercise conditioning can dramatically reduce cardiac mortality, even in patients with preexisting cardiac disease. Conversely, the lack of exercise is strongly associated with an increased incidence of many chronic debilitating diseases, including coronary heart disease. Because it is well established that aerobic exercise conditioning can alter autonomic balance (increasing parasympathetic tone and decreasing sympathetic activity), a prudently designed exercise program could prove to be an effective and nonpharmacological way to enhance cardiac electrical stability, thereby protecting against sudden cardiac death.

Optimal treatment and current situation in reperfusion after thrombolysis for acute myocardial infarction

Acute myocardial infarction is the leading cause of death in the industrialized world and the paramount goal is establishing early, complete, and sustained reperfusion at the myocardial tissue level. For hospitals without the capacity to perform emergent percutaneous coronary intervention, fibrinolytic therapy plays a critical role although it is limited by a 67% success rate. Despite promising pilot studies, reduced-dose fibrinolytic therapy with glycoprotein IIb/IIIa therapy (GUSTO-V) and full-dose fibrinolytic therapy with enoxaparin (ASSENT-3) or bivalirudin (HERO-2) provide only marginally improved clinical outcomes. Adjunctive in-hospital and secondary preventive measures should include an aspirin, a beta-blocker, an ACE inhibitor, and a statin, based on the Heart Protection Study, unless contraindicated. Patients should be risk stratified, participate in a cardiac rehabilitation program, cease smoking tobacco, and have an intracardiac defibrillator (ICD) implanted if their LV systolic function is < or = 30% at one month based on the MADIT-2 trial.

Treatment of the elderly post-myocardial infarction patient

Coronary risk factors should be modified in older persons after myocardial infarction (MI). Aspirin 160-325 mg daily and beta blockers should be administered indefinitely. Anticoagulants should be administered post-MI to patients unable to tolerate daily aspirin, to those with persistent atrial fibrillation, and to those with left ventricular thrombus. Nitrates, along with beta blockers, should be used to treat angina pectoris. Angiotensin-converting enzyme inhibitors should be administered after MI to patients who have congestive heart failure, an anterior MI, or a left ventricular ejection fraction of at or below 40%. There are no class I indications for the use of calcium channel blockers after MI. Complex ventricular arrhythmias should be treated with beta blockers. Persons with life-threatening ventricular tachycardia or ventricular fibrillation or who are at very high risk for sudden cardiac death after MI should receive an automatic implantable cardioverter-defibrillator. There are no class I indications for the use of hormonal therapy in postmenopausal women after MI. Indications for coronary revascularization after MI in older individuals are prolongation of life and relief of unacceptable symptoms despite optimal medical management.

Intravenous antiarrhythmic agents

Intravenous antiarrhythmic drugs can be used as diagnostic tools; for example, adenosine can be used to reveal the underlying rhythm in narrow QRS tachycardia. Newer class III antiarrhythmic agents, like ibutilide and dofetilide, are effective at the conversion of acute atrial fibrillation; however, electrical cardioversion is still the most effective method for restoration of sinus rhythm in persistent atrial fibrillation. Lidocaine and bretylium in the treatment and prevention of ventricular tachyarrhythmia are de-emphasized because of inefficacy, safety concerns (lidocaine), or shortage of drug (bretylium). Procainamide is effective for stable ventricular tachycardia, and amiodarone is effective in the treatment of shock-refractory ventricular fibrillation. Adrenergic blockade is likely important in the management of tachyarrhythmias, particularly in electrical storm, but more data will be necessary to establish its role.

Out-of-hospital ventricular fibrillation in patients with acute myocardial infarction: coronary angiographic determinants

OBJECTIVES

The study intended to compare the acute coronary anatomy of patients with acute myocardial infarction (AMI) complicated by out-of-hospital ventricular fibrillation (VF) versus patients with AMI without this complication.

BACKGROUND

More than half of the deaths associated with AMI occur out of the hospital and within 1 h of symptom onset. The angiographic determinants of out-of-hospital VF in patients with AMI have not been investigated in detail.

METHODS

Acute coronary angiographic findings of 72 consecutive patients with AMI complicated by out-of-hospital VF were compared with findings from 144 matched patients with AMI without this complication.

RESULTS

Patients with an acute occlusion of the left anterior descending coronary artery (LAD) or left circumflex coronary artery (LCx) had a higher risk for out-of-hospital VF compared with patients with an acute occlusion of the right coronary artery (RCA) (odds ratio and 95% confidence interval, respectively, 4.82 [2.35 to 9.92] and 4.92 [2.34 to 10.39]). With regard to extent of coronary artery disease (CAD), the location of the culprit lesion in the coronary arteries (proximal vs. mid or distal), the flow in the infarct related artery (IRA), the presence or absence of collaterals to the IRA and chronic occlusions, there were no differences between the two groups.

CONCLUSIONS

Acute myocardial infarction due to occlusion in the left coronary artery (LCA) is associated with greater risk for out-of-hospital VF compared to the RCA. The location of occlusion within LCA (LAD, LCx, proximal or distal), amount of myocardium at risk for necrosis and extent of CAD are not related to out-of-hospital VF.

Management of the older person with ventricular arrhythmias

OBJECTIVE

To review the prognosis and management of ventricular arrhythmias (VA) in persons with and without heart disease, with emphasis on older adults.

DATA SOURCES

A computer-assisted search of the English language literature (MEDLINE database) followed by a manual search of the bibliographies of pertinent articles.

STUDY SELECTION

Studies on the prognosis and management of VA in persons with and without heart disease were screened for review. Studies in older persons and recent studies were emphasized.

DATA EXTRACTION

Pertinent data were extracted from the reviewed articles. Emphasis was placed on studies involving older persons. Relevant articles were reviewed in depth.

DATA SYNTHESIS

Available data on the prognosis and management of VA in persons with and without heart disease, with emphasis on studies in older persons, were summarized.

CONCLUSIONS

Ventricular arrhythmias in older persons without heart disease should not be treated with antiarrhythmic drugs, nor should Class I antiarrhythmic drugs be used to treat VA in older persons with heart disease. Beta-blockers should be used to treat complex VA in older persons with ischemic or nonischemic heart disease without contraindications to beta-blockers. Amiodarone should be reserved for life-threatening ventricular tachyarrhythmias in older persons who cannot tolerate or who do not respond to beta-blockers. Angiotensin-converting enzyme inhibitors should be used to treat older persons with heart failure, an anterior myocardial infarction, or a left ventricular ejection fraction < or = 40%. If older persons have life-threatening recurrent ventricular tachycardia (VT) or ventricular fibrillation (VF) resistant to antiarrhythmic drugs, invasive intervention should be performed. The automatic implantable cardioverter-defibrillator is recommended in older persons who have medically refractory sustained VT or VF.

Sustained ventricular arrhythmias in patients receiving thrombolytic therapy: incidence and outcomes. The GUSTO Investigators

BACKGROUND

Sustained ventricular tachycardia (VT) and fibrillation (VF) occur in up to 20% of patients with acute myocardial infarction (MI) and have been associated with a poor prognosis. The relationships among the type of arrhythmia (VT versus VF or both), time of VT/VF occurrence, use of thrombolytic agents, and eventual outcome are unclear.

METHODS AND RESULTS

In the GUSTO-I study, we examined variables associated with the occurrence of VT/VF and its impact on mortality. Of the 40 895 patients with ventricular arrhythmia data, 4188 (10.2%) had sustained VT, VF, or both. Older age, systemic hypertension, previous MI, Killip class, anterior infarct, and depressed ejection fraction were associated with a higher risk of sustained VT and VF (P<0.001). In-hospital and 30-day mortality rates were higher among patients with sustained VT/VF than among patients without sustained ventricular arrhythmias (P<0.001). Both early (<2 days) and late (>2 days) occurrences of sustained VT and VF were associated with a higher risk of later mortality (P<0. 001). In addition, patients with both VT and VF had worse outcomes than those with either VT or VF alone (P<0.001). Among patients who survived hospitalization, no significant difference was found in 30-day mortality between the VT/VF and no VT/VF groups. However, after 1 year, the mortality rate was significantly higher in the VT alone and VT/VF groups (P<0.0001).

CONCLUSIONS

Despite the use of thrombolytic therapy, both early and late occurrences of sustained VT or VF continue to have a negative impact on patient outcome; patients with both VT and VF had the worst outcome; and among patients who survived hospitalization, the 1-year mortality rate was significantly higher in those who experienced VT alone or VT and VF.