Combination of calcium channel blocker and thrombolytic therapy in acute myocardial infarction

Protective effects of polydatin on experimental testicular torsion and detorsion injury in rats

Oxidative stress plays a critical role in the process of testicular torsion and detorsion (T/D). The purpose of the present study was to investigate the protective effect of polydatin (PD) on testicular T/D injury. Rats were randomly divided into three groups, a sham group, a group subjected to 2 h torsion followed by 24 h detorsion and a group subjected to T/D and injected i.p. with 20 mg kg−1 PD 30 min before detorsion. Unilateral orchiectomy was performed after 24 h of reperfusion. Half the testes were prepared for histological examination by haematoxylin–eosin staining and the terminal deoxyribonucleotidyl transferase-mediated dUTP–digoxigenin nick end-labelling (TUNEL) technique. In the remaining tissues, levels of malondialdehyde (MDA), catalase (CAT), glutathione peroxidase (GPx) and superoxide dismutase (SOD) were determined, as was the expression of several apoptosis-related proteins. Compared with the T/D group, PD pretreatment significantly ameliorated the morphological damage, lowered the Cosentino histological score and increased the mean number of germ cell layers and Johnsen’s testicular biopsy score. In addition, PD treatment markedly decreased MDA levels and upregulated CAT, GPx and SOD activity. Furthermore, PD decreased T/D-induced germ cell-specific apoptosis, attenuated the activation of caspase-3, caspase-8, caspase-9 and poly(ADP-ribose) polymerase and increased the Bcl-2/Bax ratio. The findings indicate that PD has a protective effect against testicular T/D injuries, especially at the histological, antioxidative stress and antiapoptotic levels.

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.

Intravenous diltiazem in acute myocardial infarction. Diltiazem as adjunctive therapy to activase (DATA) trial

OBJECTIVES

This study was defined as a pilot investigation of the usefulness and safety of intravenous diltiazem as adjunctive therapy to tissue plasminogen activator in acute myocardial infarction, followed by oral therapy for 4 weeks.

BACKGROUND

Experimental studies have documented that calcium antagonists protect the myocardial cell against the damage caused by coronary artery occlusion and reperfusion, yet no benefits have been conclusively demonstrated in acute myocardial infarction (AMI) in humans.

METHODS

In this pilot study, 59 patients with an AMI treated with tissue-type plasminogen activator (t-PA) were randomized, double blinded, to intravenous diltiazem or placebo for 48 h, followed by oral therapy for 4 weeks. The primary objective was to detect an effect on indices of regional left ventricular function and perfusion. Patients were also closely monitored for clinical events, coronary artery patency and indices of infarct size and of left ventricular function.

RESULTS

Creatine kinase elevation, Q wave score, global and regional left ventricular function and coronary artery patency at 48 h were not significantly different between the diltiazem and placebo groups. A greater improvement observed in regional perfusion and function with diltiazem was likely explained by initial larger defects. Diltiazem, compared to placebo, reduced the rate of death, reinfarction or recurrent ischemia at 35 days from 41% to 13% (p=0.027) and prevented the need for an urgent intervention. The rate of death or myocardial infarction was reduced by 65% (p=0.15). These benefits could not be explained by differences in baseline characteristics such as age, site and extent of infarction, time of inclusion or concomitant therapy. Heart rate and blood pressure were reduced throughout the study with active diltiazem treatment. Side effects of diltiazem were bradycardia and hypotension that required transient or permanent discontinuation of the study drug in 27% of patients, vs. 17% of patients with placebo.

CONCLUSIONS

A protective effect for clinical events related to early postinfarction ischemia and reinfarction was suggested in this study, with diltiazem administered intravenously with t-PA followed by oral therapy for 1 month, with no effect on coronary artery patency and left ventricular function and perfusion.

Diltiazem improves left ventricular systolic function following acute myocardial infarction treated with streptokinase. The Calcium Antagonist in Reperfusion Study (CARES) Group

The role of diltiazem on left ventricular systolic function was analyzed in 101 patients with acute myocardial infarction treated with streptokinase, being obtained, for the total of the population, higher LV global ejection fraction (p = 0.022), LV regional shortening (p = 0.046) and LV global shortening (p = 0.064) for the treated group, relative to the placebo group; the p values were, respectively, 0.005, 0.009, and 0.012, for patients that achieved TIMI-3 antegrade coronary flow. It is concluded that diltiazem is useful as adjuvant to streptokinase, especially when antegrade coronary blood flow TIMI-3 is obtained.

Calcium channel antagonists in the modern era of coronary thrombolysis: benefit or detriment?

Calcium channel antagonists are among the world's most widely prescribed class of drugs and are used most often in patients with hypertension and coronary artery disease. However, in the recent past serious questions have been raised concerning their potentially detrimental effects. One area of considerable clinical importance that deserves close inspection is the role of calcium channel antagonists following coronary reperfusion. Specifically, is there benefit or detriment?

Prognosis of patients with unstable angina or acute myocardial infarction treated with calcium channel antagonists

The safety of calcium channel antagonists has become a controversial issue among cardiologists. Thus, the role of calcium antagonists in the treatment of myocardial infarction is reviewed, and the differences among the 3 classes of calcium channel antagonists, phenylalkylamines, dihydropyridines, and benzothiazepines, are discussed.

Cardiac surgical implications of calcium dyshomeostasis in the heart

The prevalence of coronary artery disease renders myocardial ischemia a leading cause of morbidity and mortality. Both cardiac bypass operations and cardiac transplantation cause myocardial ischemia and reperfusion injury. Intracellular calcium transport and regulation are of paramount importance in both normal and pathologic myocardial states. Calcium regulation is integral to nearly every myocyte function, from early development to senescence. Normal intracellular calcium-mediated excitation-contraction coupling and abnormal patterns of calcium regulation leading to systolic/diastolic dysfunction are now therapeutically accessible to the cardiac surgeon. Additionally, altered Ca2+ transport protein gene expression is a mechanism of myocardial dysfunction. Therapeutic strategies involve receptor-mediated transduction of signals to intracellular metabolic sites. Evidence implicates protein kinase C as well as a potential therapeutic role for Ca2+. The potential for pharmacologic access to this protective state has abundant clinical appeal. The protective state (cardiac "preconditioning") is transient but is amenable as therapy against operation-related ischemic events.

Nifedipine. Dose-related increase in mortality in patients with coronary heart disease

BACKGROUND

The purpose of this study was to assess the effect of the dose of nifedipine, a dihydropyridine calcium antagonist, on the increased risk of mortality seen in the randomized secondary-prevention trials and to review the mechanisms by which this adverse effect might occur.

METHODS AND RESULTS

We restricted the dose-response meta-analysis to the 16 randomized secondary-prevention trials of nifedipine for which mortality data were available. Recent trials of any calcium antagonist and formulation were also reviewed for information about the possible mechanisms of action that might increase mortality. Overall, the use of nifedipine was associated with a significant adverse effect on total mortality (risk ratio, 1.16, with a 95% CI of 1.01 to 1.33). This summary estimate fails to draw attention to an important dose-response relationship. For daily doses of 30 to 50, 60, and 80 mg, the risk ratios for total mortality were 1.06 (95% CI, 0.89 to 1.27), 1.18 (95% CI, 0.93 to 1.50), and 2.83 (95% CI, 1.35 to 5.93), respectively. In a formal test of dose response, the high doses of nifedipine were significantly associated with increased mortality (P = .01). While the mechanism of this adverse effect is not known, there are several plausible explanations, including the established proischemic effect, negative inotropic effects, marked hypotension, recently reported prohemorrhagic effects attributed to antiplatelet and vasodilatory actions of calcium antagonists, and possibly proarrhythmic effects.

CONCLUSIONS

In patients with coronary disease, the use of short-acting nifedipine in moderate to high doses causes an increase in total mortality. Other calcium antagonists may have similar adverse effects, in particular those of the dihydropyridine type. Long-term safety data are lacking for most calcium antagonists.

Intravenous thrombolytic therapy in myocardial infarction: an analytical review

The properties and physiological effects of three currently FDA-approved thrombolytic agents, streptokinase (SK), tissue plasminogen activator (tPA), and anisoylated plasminogen activator complex (APSAC) are reviewed. All thrombolytic agents have been shown to reduce mortality postmyocardial infarction (MI). Comparative trials have failed to demonstrate a difference between the effects of tPA, SK, and APSAC on mortality. In addition, no consistent difference between the three agents on ejection fraction (EF) has been found despite a superior reperfusion rate with tPA at 90 min. Furthermore, reinfarction and interventional procedure rates were significantly higher after thrombolytic treatment, and the incidence of total strokes was higher with tPA than SK in some comparative studies. Based on analysis of the published megatrials, SK is a more cost-effective thrombolytic agent for patients with acute MI than tPA or APSAC.

Pharmacological management of acute myocardial infarction

The routine medical management of patients with acute myocardial infarction (AMI) has undergone major changes in the last decade. Several large-scale trials have firmly established the effectiveness of thrombolytic therapy, beta blockers, and aspirin in the treatment of AMI. The critical issues include reducing myocardial oxygen demand and restoring adequate blood supply to the ischemic regions of the myocardium. As a result, the ability to intervene in patients with AMI has improved significantly. The purpose of this review is to discuss briefly the results of major trials of primary and secondary pharmacological intervention which had a direct impact on the care of patients with AMI. It concludes with current recommendations for the management of patients with AMI.

The golden hours of the myocardial infarction: nonthrombolytic interventions

Emergency care of patients with acute myocardial infarction requires active decision making to use agents that may improve morbidity and mortality. Thrombolysis remains the primary tool to accomplish this goal. Other pharmacologic agents, including lidocaine, nitrates, calcium channel blockers, beta-blockers, and aspirin, have been used acutely in myocardial infarction in the hopes of preventing death and salvaging myocardium. The decision to select one or all of these agents requires a knowledge of the clinical evidence of their efficacy and risk-to-benefit ratios. The clinical studies of the use of these agents acutely in the management of myocardial infarction are reviewed.

Adjunctive use of beta-adrenergic blockers, calcium antagonists and other therapies in coronary thrombolysis

The availability of thrombolytic agents for use in the treatment of acute myocardial infarction is an important step in the management of a common, often debilitating, and potentially lethal disorder. However, despite the proven benefits of coronary thrombolysis, the importance of adjunctive treatment modalities is being increasingly recognized. Beta-adrenergic blockers, calcium antagonists, nitrates, magnesium, and angiotensin-converting enzyme inhibitors each exert favorable cardiovascular properties that may offer additional benefits. Clinical trials combining thrombolytic and adjunctive pharmacologic agents offer hope for further advances in the treatment of acute myocardial infarction.

Progress in cardioprotection: the role of calcium antagonists

Calcium antagonists are now widely used for the treatment of clinical hypertension and angina pectoris. They are efficacious for the treatment of vasospastic, fixed atherosclerotic and mixed angina; they reduce the incidence of silent ischemia; and they have been shown to reduce postmyocardial infarct angina. Experimental data suggest that they may have certain cardioprotective properties in cases of acute myocardial ischemia and infarction, stunned myocardium, diastolic dysfunction, left ventricular hypertrophy and atherosclerosis. Moreover, they have been shown to improve exercise performance, as well as the diastolic abnormalities in patients with hypertrophic cardiomyopathy. In animals, they may delay or reduce the extent of myocardial necrosis after coronary occlusion or coronary occlusion followed by reperfusion, and in low doses that do not alter the hemodynamic profile, they have been shown to enhance the return of ventricular function in animals with stunned myocardium. However, the early first-generation calcium antagonists (nifedipine, verapamil, diltiazem) have not been shown to reduce myocardial infarct size or to enhance survival in patients with acute myocardial infarction. There now are clinical studies that suggest that, unlike beta blockers or nitrates, nifedipine may slow the development of atherosclerotic progression in humans over a 2-year period, and it seems likely that in the 1990s there will be further expansion of the use of calcium antagonists for not only angina and hypertension but also for aspects of cardioprotection. That calcium antagonists may delay, prevent or possibly regress atherosclerotic lesions is an exciting possibility.

Left ventricular ejection fraction may not be useful as an end point of thrombolytic therapy comparative trials

In the era of comparative and adjunctive trials in reperfusion therapy, the need to develop alternative end points for mortality reduction is clear. Left ventricular ejection fraction, which has been commonly used as a surrogate, is problematic due to missing values, technically inadequate studies, and lack of correlation with mortality results in controlled reperfusion trials performed to date. In this paper, we present a composite clinical end point that includes, in order, severity of adverse outcome death, hemorrhagic stroke, nonhemorrhagic stroke, poor ejection fraction (less than 30%), reinfarction, heart failure, and pulmonary edema. Such a composite index may be useful to detect true therapeutic benefit in reperfusion trials without necessitating greater than 20-30,000 patient enrollment.

Management of the patient following coronary thrombolysis

Myocardial salvage can be maximized by the early institution of thrombolytic therapy and aspirin. Certain patients may benefit from the administration of intravenous heparin, beta blockers, or nitroglycerin. The routine use of percutaneous transluminal coronary angioplasty (PTCA) or calcium-channel blockers does not appear to be warranted. Recurrent myocardial ischemia should be vigorously treated with medical therapy and there may be value in cardiac catheterization, followed by PTCA or bypass surgery, depending upon the extent of myocardium at risk and the underlying coronary anatomy. Long-term morbidity and mortality may be reduced by instituting aspirin and beta blockers as well as by modifying risk factors. There is no evidence for the long-term benefit from any calcium-channel blocker. Oral anticoagulation may be warranted in those patients with a mural thrombus, congestive heart failure, or atrial fibrillation. ACE inhibitors may be of value in the presence of left ventricular dysfunction and certainly in the presence of symptomatic congestive heart failure. Antiarrhythmic therapy is generally indicated only for symptomatic or life-threatening arrhythmias. Residual myocardial ischemia should be sought by exercise testing, and those patients with poor exercise tolerance generally warrant cardiac catheterization in consideration for revascularization.

Cardiac rupture, mortality and the timing of thrombolytic therapy: a meta-analysis

This study examined the relation between the risk of cardiac rupture and the timing of thrombolytic therapy for acute myocardial infarction. To test the hypothesis that cardiac rupture is prevented by early thrombolytic therapy but is promoted by late treatment, randomized controlled trials of thrombolytic agents for myocardial infarction were pooled. A logistic regression model including 58 cases of cardiac rupture among 1,638 patients from four trials showed that the odds ratio (treated/control) of cardiac rupture was directly correlated with time to treatment (p = 0.01); at 7 h, the odds ratio was 0.4 (95% confidence limits 0.17 to 0.93); at 11 h, it was 0.93 (0.53 to 1.60) and at 17 h, it was 3.21 (1.10 to 10.1). Analysis of data from the Gruppo Italiano per lo Studio della Streptochinasi nell'Infarto Miocardico (GISSI) trial independently confirmed the relation between time to thrombolytic therapy and risk of cardiac rupture (p = 0.03). Analysis of 4,692 deaths in 44,346 patients demonstrated that the odds ratio of death was also directly correlated with time to treatment (p = 0.006); at 3 h, the odds ratio for death was 0.72 (0.67 to 0.77); at 14 h, it was 0.88 (0.77 to 1.00) and at 21 h, it was 1 (0.82 to 1.37). Thrombolytic therapy early after acute myocardial infarction improves survival and decreases the risk of cardiac rupture. Late administration of thrombolytic therapy also appears to improve survival but may increase the risk of cardiac rupture.

Possible survival benefit from concomitant beta-but not calcium-antagonist therapy during reperfusion for acute myocardial infarction

To test the hypothesis that long-term beta- or calcium-antagonist therapy begun before the time of myocardial infarction and coronary reperfusion might improve patient in-hospital survival compared with reperfusion alone, 424 consecutive patients successfully reperfused with coronary angioplasty within 12 hours of infarct symptom onset were carefully and retrospectively characterized. Forty-seven patients (11%) were taking beta antagonists and 74 patients (17%) were taking calcium antagonists at the time of infarction. Patients receiving beta antagonists had a more frequent history of hypertension (p less than or equal to 0.001) and prior infarction (p less than or equal to 0.01) than those not so treated and patients receiving calcium antagonists had a more frequent history of prior infarction, prior angina, hypertension and diabetes (all p less than or equal to 0.001) than their nontreated counterparts. Stepwise logistic regression analysis found significant independent correlations between in-hospital death and the following variables: recurrent ischemia (p less than or equal to 0.001); proximal left anterior descending coronary infarct (p less than or equal to 0.001); 3-vessel disease (p = 0.002); patient age (p = 0.004); and initial total occlusion of the infarct artery (p = 0.022). After adjustment for these factors, beta antagonist use (mortality = 0 vs 8% without treatment) was still significantly correlated with improved survival (p = 0.048), whereas calcium-antagonist therapy made no difference in survival. Heart rate and left ventricular end-diastolic pressure upon presentation were significantly lower in patients treated with beta antagonists. Thus, beta-antagonists therapy, but probably not calcium-antagonist therapy, taken before reperfusion for acute myocardial infarction, may improve early survival compared to reperfusion alone. Larger studies will be required to confirm or refute these observations.

Antiplatelet antibody [7E3 F(ab')2] prevents rethrombosis after recombinant tissue-type plasminogen activator-induced coronary artery thrombolysis in a canine model

Coronary artery rethrombosis can complicate initially effective thrombolytic therapy. Platelets interacting with injured vascular endothelium in a region along the coronary artery with reduced luminal cross-sectional area contribute to rethrombosis. The purpose of this study was to investigate the potential of the F(ab')2 fragment of the murine monoclonal antibody 7E3 [7E3 F(ab')2] to prevent rethrombosis after intracoronary clot lysis with recombinant tissue-type plasminogen activator (rt-PA) in an experimental model. The 7E3 F(ab')2 binds to the platelet glycoprotein IIb/IIIa complex (GPIIb/IIIa), thereby preventing platelet-fibrinogen interaction and intravascular thrombus formation. Experimental coronary artery thrombosis was produced in the anesthetized dog by application of direct anodal current to the intimal surface of the left circumflex coronary artery in the region of an external stenosis. Lysis of the established intracoronary thrombus was achieved with the intravenous administration of rt-PA (25 mg) after which the animals were randomized into two groups. Group 1 (n = 10) served as the control, receiving the saline diluent, and group 2 (n = 9) received 7E3 F(ab')2, given as a single intravenous injection (0.8 mg/kg). The times required for occlusive thrombus formation, rt-PA-induced thrombolysis, and rethrombosis (if it occurred) were similar in the animals treated with saline and those treated with 7E3 F(ab')2. The initial left circumflex coronary artery blood flow was similar in both groups but decreased to a negligible level in group 1. In group 2, left circumflex coronary artery blood flow declined modestly (24 +/- 2 to 10 +/- 2 ml/min). Rethrombosis occurred in all animals in group 1 but in only two of nine animals in group 2 (p less than 0.05). Oscillations in coronary blood flow preceded rethrombosis in group 1, whereas 7E3 F(ab')2 stabilized left circumflex coronary artery blood flow patterns during the course of teh experimental protocol (5.2 +/- 0.9 vs. 0.7 +/- 0.4 oscillations, respectively; p less than 0.05). Thrombus mass recovered from the left circumflex coronary artery at the conclusion of each experiment was greater in group 1 as compared with group 2 (7.0 +/- 2.3 vs. 1.5 +/- 0.7 mg, respectively; p less than 0.05). The area of left ventricle at risk for infarction was similar in both groups but infarct size, infarction/at risk assessed histochemically, was larger in group 1 than group 2 (35 +/- 9% vs. 6 +/- 4%, respectively; p less than 0.05). Platelet aggregation induced by ADP and arachidonic acid was similar at baseline for all of the animals.(ABSTRACT TRUNCATED AT 400 WORDS)

Calcium channel blockers in acute myocardial infarction and unstable angina: an overview

OBJECTIVE

To assess the effects of calcium channel blockers on development of infarcts, reinfarction, and mortality.

DESIGN

A systematic overview of all randomised trials of calcium channel blockers in myocardial infarction and unstable angina.

PATIENTS

19,000 Patients in 28 randomised trials.

RESULTS

In the trials of myocardial infarction 873 deaths occurred among 8870 patients randomised to active treatment compared with 825 deaths among 8889 control patients (odds ratio of 1.06, 95% confidence interval of 0.96 to 1.18). There was no evidence of a beneficial effect on development and size of infarcts or rate of reinfarction. The results were similar in short term trials in which treatment was confined to the acute phase and those in which treatment was started some weeks later and continued for a year or two. There was no evidence of heterogeneity among different calcium channel blockers in their effects on any end point. The results were similar in the unstable angina trials (110 out of 561 patients treated with calcium channel blocker compared with 104 out of 548 controls developed a myocardial infarction; 14 out of 591 treated compared with nine out of 578 controls died).

CONCLUSIONS

Calcium channel blockers do not reduce the risk of initial or recurrent infarction or death when given routinely to patients with acute myocardial infarction or unstable angina.

Reperfusion injury and its pharmacologic modification

Reperfusion injury includes a spectrum of events, such as reperfusion arrhythmias, vascular damage and no-reflow, and myocardial functional stunning. The concept of reperfusion injury remains controversial with many proposed mechanisms when applied to humans, whereas in animal models, there are two main proposed mechanisms: calcium over-load and formation of oxygen free radicals. To prove that reperfusion injury is specifically caused by reperfusion would require evidence that an intervention given at the time of reperfusion can diminish or abolish the injury as in the case of arrhythmias, which are thought to be mediated by excess recycling of cytosolic calcium with delayed afterdepolarizations and ventricular automaticity. In the case of myocardial stunning, the phenomenon may be mediated, at least in part, by a burst of free radicals formed within the first minute of reperfusion and improved by free radical scavengers given at the time of reperfusion. The alternate hypothesis is that cytosolic calcium overload damages mechanisms for normal intracellular calcium regulation so that the stunned myocardium responds to agents that are thought to increase intracellular cytosolic calcium, such as beta-receptor agonists. A further component of reperfusion injury, under active investigation, is microvascular damage with alterations at the level of platelets, leukocytes, and endothelial integrity. From the therapeutic point of view, the divergent results of experimental interventions and the possibility that the abrupt onset of reperfusion in animals differs from the situation in humans with thrombolysis means that the best way currently available to limit reperfusion injury is by minimizing the ischemic period by early reperfusion and by optimizing the metabolic status of the ischemic myocardium at the end of the ischemic period.

Calcium-channel blockers in acute myocardial infarction

The calcium-channel blockers are useful in treating a variety of cardiovascular disorders. Due to their antiischemic and spasmolytic properties, these agents have been studied in the prophylaxis and treatment of acute myocardial infarction. This article reviews this application with respect to reduction of mortality, infarct size, and reinfarction rate. Of the agents currently available for clinical use, nifedipine has been studied most extensively. This agent shows no beneficial effects in this setting and its use may in fact be harmful. Of the few trials that have been conducted with verapamil, none have shown decreased mortality. Verapamil may reduce infarct size although further confirmation is required. Diltiazem is the only agent that has been shown to have short- and long-term benefits in the patient with acute myocardial infarction. Proper patient selection is of utmost importance in ensuring successful therapy. In particular, those patients with non-Q-wave infarctions and/or normal left ventricular function can be expected to derive the most benefit in terms of reducing mortality and reinfarction rate associated with the acute event.

Beta-adrenergic blockade and calcium channel blockade in myocardial infarction

Because of their hemodynamic and antiarrhythmic actions, beta-adrenergic blockers and calcium-entry blockers have been suggested for use in patients with myocardial infarction (MI) for reducing infarct size, preventing ventricular ectopy, and for prolonging life in survivors of acute MI. Experimental studies have suggested their usefulness in these areas. Clinical studies have demonstrated a role for beta-blockers in the hyperacute phase of MI, and in longterm treatment of infarct survivors. Calcium channel blockers appear to have somewhat less utility in patients with Q wave MIs, but may have an important role in therapy of the non-Q wave infarct.