Verapamil in acute myocardial infarction

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.

Attenuation of the Negative Inotropic Effects of Metoprolol at Short Cycle Lengths in Humans

OBJECTIVES

This study sought to compare the influence of changes in systolic interval on the negative inotropic effects of metoprolol, sotalol, and verapamil in patients with ischemic heart disease.

BACKGROUND

The long-term symptomatic and prognostic effects of antiarrhythmic agents are not easily predicted on the basis of acute hemodynamic actions at rest, but may be unmasked during tachycardia. However, this has not been studied extensively in vivo.

METHODS

The force-interval relationship of the intact human left ventricle was examined before and 10 min after intravenous bolus administration of the negatively inotropic agents metoprolol, sotalol, or verapamil in patients undergoing diagnostic cardiac catheterization.

RESULTS

All three drugs similarly reduced maximal rate of increase of left ventricular pressures (LV+dP/dt(max)) by approximately 10%, but diversely modified the force-interval relationship. The parameter c (the reduction in LV+dP/dt(max) of a fixed premature stimulus on mechanical restitution) was significantly reduced by metoprolol (by 9+/- 4%, p < 0.05), was increased by verapamil (by 6 +/- 2%, p < 0.05), and was not significantly changed by sotalol. Similarly, metoprolol had a minimal effect on the extent of frequency potentiation, whereas sotalol and verapamil attenuated frequency potentiation (the relative response to 10 s of rapid pacing was 1.19 +/- 0.58-fold, 0.07 +/- 0.35-fold, and 0.03 +/- 0.17-fold of the baseline response after 10 min of metoprolol, sotalol, or verapamil, respectively).

CONCLUSIONS

These results show that the negative inotropic effects of metoprolol are attenuated and those of verapamil are accentuated at short cycle lengths; sotalol is intermediate between the two. These properties may contribute to the relative safety of these agents in patients prone to hemodynamic deterioration during sustained tachycardia.

Acute myocardial infarction. Then and now

Dramatic changes in the management of acute myocardial infarction (AMI) have occurred in the past decade. While previous management strategies were primarily supportive, current strategies focus on achieving and maintaining patency of the infarct-related artery restoring blood flow to jeopardized myocytes, preserving left ventricular function, and preventing recurrences and complications in addition to promoting healing. Restoration of blood flow can be achieved pharmacologically with thrombolytic agents or mechanically with percutaneous transluminal coronary angioplasty (PTCA). Early use of antiplatelet agents and anticoagulants helps maintain patency of the infarct-related arteries and prevents thromboembolic complications. Administration of beta-blockers and angiotensin enzyme inhibitors are more specific means of conserving myocardium and preserving ventricular function. Additionally, several strategies for preventing arrhythmias such as prophylactic lidocaine use and routine long-term suppression of premature ventricular contractions with antiarrhythmic drugs are no longer routinely advocated. Basically, in the era prior to the eighth decade of this century, the primary direction of the therapeutic strategy for AMI was to reduce the oxygen demands in the infarcted myocardium; whereas in the subsequent years, the emphasis shifts to improvement in oxygen delivery, via thrombolysis, PTCA, and coronary artery bypass graft surgery. These interventional changes, when added to greater sophistication in the use of drugs to reduce oxygen demands, resulted in significant lowering of myocardial mortality.

Angiotensin-converting enzyme inhibitors and calcium antagonists after acute myocardial infarction

This article examines trials of the use of two types of drugs in the treatment of myocardial infarction: angiotensin-converting enzyme (ACE) inhibitors and calcium antagonists. ACE inhibitors are an established treatment for hypertension and heart failure and have been shown to reduce mortality from heart failure and after myocardial infarction. Six large studies have been carried out. In 1 in which an ACE inhibitor was given 3-16 days after infarction in patients with an ejection fraction < 40%, mortality was reduced by 17%. In a second study of patients who had evidence of heart failure and were followed up for 15 months, treatment with ACE inhibitors was given 3-10 days after myocardial infarction and mortality was reduced by 27%. Two other studies of 11,000 and 50,000 unselected patients with myocardial infarction showed only marginal clinical benefit. Calcium antagonists were introduced to treat hypertension and angina pectoris. In trials with patients with heart failure, the results have not been encouraging, and in some patients these agents seem to be harmful. Recently, long-acting calcium antagonists have become available, and these may avoid the deleterious effects of short-acting drugs. Since calcium antagonists act on smooth muscle, they may increase myocardial blood flow to improve function after "stunning" or "hibernation." This idea was investigated with a long-acting dihydroyridine calcium, antagonist in a randomized double-blind, placebo-controlled study (Doppler Flow, Echocardiography, and Functional Improvement Assessment of Nisoldipine Therapy-I--DEFIANT I), and a further study is being carried out. At present the widespread use of calcium antagonists after infarction is not recommended.

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.

Calcium antagonists and myocardial infarction

In vitro and in vivo studies have demonstrated many similarities between the three calcium antagonists verapamil, nifedipine, and diltiazem in relation to protection of the myocardium during hypoxia. Important clinical differences exist between the three drugs when they are used during or after an acute myocardial infarction with the purpose of preventing death and reinfarction. The balance between the negative inotropic and the vasodilator properties and concomitant treatment with beta blockers may explain the results of clinical trials with the three calcium antagonists. Patients not treated with beta blockers. Nifedipine has been demonstrated to be no better than placebo both during and after an acute myocardial infarction. No placebo-controlled studies exist with diltiazem. Verapamil had no effect during the acute phase of a myocardial infarction. After a myocardial infarction, verapamil improved survival and reduced the reinfarction rate, an effect primarily found in patients without heart failure in the coronary care unit. Patients also treated with beta blockers. Nifedipine prevents the development of myocardial infarcts in patients with unstable angina. Diltiazem probably prevents reinfarction in the first two weeks after non-Q-wave infarction. Secondary prevention with diltiazem after an acute myocardial infarction had no overall effect on death or cardiac events (i.e., reinfarction or cardiac death). Subgroup analysis demonstrated in diltiazem-treated patients, compared with placebo-treated patients, a significant reduction of cardiac events in patients without and a significant increase of cardiac events in patients with heart failure. At present no indications exist for nifedipine during or after a myocardial infarction; further studies are needed with diltiazem, and verapamil may be used in secondary prevention of death and reinfarction.

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.

Secondary prevention with verapamil after myocardial infarction. The Danish Study Group on Verapamil in Myocardial Infarction

The effect of verapamil on death and major events (i.e., death or reinfarction) after an acute myocardial infarction was studied in a double-blind, randomized, placebo-controlled, multicenter trial, the Danish Verapamil Infarction Trial II (DAVIT II). Eight hundred seventy-eight patients started treatment with verapamil 360 mg/day and 897 patients with placebo. Treatment continued for up to 18 months (mean 16 months). Ninety-five deaths and 146 major events occurred in the verapamil group and 119 deaths and 180 major events in the placebo group. Eighteen-month mortality rates were 11.1 and 13.8% (hazard ratio 0.80, 95% confidence limits 0.63 to 1.05, p = 0.108), and major event rates 18.0 and 21.6% (0.80, 0.64 to 0.99, p = 0.027) in the verapamil and placebo groups respectively. When combining the results of this trial with the results of the first Danish study on verapamil in myocardial infarction, the meta-analysis demonstrated that treatment with verapamil from the second week after an acute myocardial infarction resulted in a reduction of pooled odds ratios of 0.22 (95% confidence interval 0.01 to 0.37, p = 0.04) for death, 0.21 (0.05 to 0.35, p = 0.02) for major events, and 0.27 (0.06 to 0.43, p = 0.02) for first reinfarctions. It is concluded that long-term treatment with verapamil after an acute myocardial infarction is associated with a significant reduction in overall mortality as well as major event and reinfarction rates.

Does verapamil limit myocardial infarct size in a heart deficient in xanthine oxidase?

1. The delay of ischaemic myocardial necrosis by verapamil has been reported in the dog heart, which contains a high level of xanthine oxidase, a potential source of cytotoxic free radicals. To test whether the retardation of ischaemic myocyte death by verapamil is not an isolated phenomenon in the xanthine oxidase rich heart, we assessed the effect of verapamil in the rabbit heart, which lacks xanthine oxidase. 2. Verapamil (200 micrograms/kg, i.v. bolus plus 40 micrograms/kg per min) was administered in a group of rabbits (n = 5) to test the haemodynamic response to this agent. The heart rate, blood pressure and left ventricular dp/dt max were reduced by 11, 25 and 57%, respectively, and the plasma concentration of verapamil was maintained at 300-400 ng/mL during the infusion. 3. In other groups of rabbits, the effect of the same dosage of verapamil on the size of myocardial infarct after 20 or 30 min ischaemia and 72 h reperfusion was examined. The verapamil was administered for 45 min, starting 15 min prior to ischaemia. The percentage of area at risk infarcted (%I/AAR) was 15.2 +/- 3.9% in the 20 min ischaemia control group and 15.4 +/- 4.5% in the 20 min ischaemia verapamil group, 49.1 +/- 3.4% in the 30 min ischaemia control group and 41.2 +/- 3.3% in the 30 min ischaemia verapamil group. The %I/AAR was significantly smaller in the 20 min ischaemia control groups and 15.4 +/- 4.5% in the 20 min ischaemia there was no difference in %I/AAR between the control and verapamil treated animals in either the 20 or the 30 min ischaemia groups. 4. These results suggest that verapamil does not delay the transition from reversible to irreversible myocardial injury during coronary occlusion in the rabbit, which like the human, lacks myocardial xanthine oxidase.

Calcium Channel Blockers

Calcium is an integral component in numerous physiological processes and functions. As such, drugs that interfere with the movement of calcium into or out of cells, or the activity of intracellular calcium are useful in treating a variety of disease states. This article will review the calcium channel blockers currently available, along with their approved indications, as well as select dihydropyridine investigational agents and nonapproved indications for their use.

Effect of verapamil on mortality and major events after acute myocardial infarction (the Danish Verapamil Infarction Trial II--DAVIT II)

The effect of verapamil on death and major events (i.e., death or reinfarction) after an acute myocardial infarction was studied in a double-blind, randomized, placebo-controlled multicenter trial. Eight hundred seventy-eight patients started treatment with verapamil, 360 mg/day, and 897 patients with placebo. Treatment started in the second week after admission and continued for up to 18 months (mean 16 months). Ninety-five deaths and 146 major events occurred in the verapamil group and 119 deaths and 180 major events in the placebo group. The 18-month mortality rates were 11.1 and 13.8% (p = 0.11, hazard ratio, 0.80; 95% confidence limits, 0.61 to 1.05), and major event rates 18.0 and 21.6% (p = 0.03, hazard ratio, 0.80; 95% confidence limits, 0.64 to 0.99) in the verapamil and placebo groups, respectively. In patients without heart failure in the coronary care unit the mortality rates were 7.7% in the verapamil group and 11.8% in the placebo group (p = 0.02, hazard ratio, 0.64; 95% confidence limits, 0.44 to 0.94), and major event rates 14.6 and 19.7% (p = 0.01, hazard ratio 0.70; 95% confidence limits (0.52 to 0.93). In patients with heart failure the mortality rates were 17.9 and 17.5% (p = 0.79, hazard ratio, 1.05; 95% confidence limits, 0.72 to 1.54), and major event rates 24.9 and 24.9% (p = 1.0, hazard ratio 0.98; 95% confidence limits 0.72 to 1.39). Long-term treatment with verapamil after an acute myocardial infarction caused a significant reduction in major events, and the positive effect was found in patients without heart failure.

Advantages of beta blockers versus antiarrhythmic agents and calcium antagonists in secondary prevention after myocardial infarction

Patients who have sustained greater than or equal to 1 myocardial infarcts are at high risk for sudden death or reinfarction; the risk is highest for those with lowest ventricular ejection fraction, continuing myocardial ischemia and asymptomatic high-density and complex premature ventricular contractions. At present, beta blockers when given prophylactically are the only agents that reduce the incidence of sudden death and reinfarction in survivors of myocardial infarction (MI) in the first 2 years. The beneficial effect was shown to correlate with a reduction in heart rate, the effect being absent or deleterious with beta blockers with marked sympathomimetic activity. The effects of beta blockers on ventricular fibrillation appeared to be dissociated from those on premature ventricular contractions. Trials with calcium antagonists indicate that these drugs had no effect or increased the mortality rate. The divergent effect of beta blockers and calcium antagonists is unexplained but may be due in part to a lack of bradycardiac effect of calcium antagonists; there were no differences in effect among different calcium antagonists. Data from trials involving class I antiarrhythmic agents indicate that agents acting by depression of cardiac conduction are either devoid of effect or produce a modest increase in mortality. Results of the Cardiac Arrhythmia Suppression Trial, employing the newer class I agents flecainide and encainide, were used to determine whether the suppression of premature ventricular contractions in the survivors of acute MI reduces mortality. Flecainide and encainide suppressed premature ventricular contractions greater than 80%, but resulted in an increased mortality rate undoubtedly due to a marked proarrhythmic effect. Whether these data can be extrapolated to all class I agents is uncertain. Preliminary data with class III antiarrhythmic agents suggest that these agents, especially amiodarone, similarly to beta blockers, have the potential to reduce mortality in survivors of MI. Evolving data suggest that in the secondary prevention of morbid events in the survivors of acute MI, the focus must shift away from antiarrhythmic agents that delay conduction and toward beta blockers and antifibrillatory actions resulting from a prolongation of refractoriness.

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.

Pharmacologic management of ischemic heart disease with beta-blockers and calcium channel blockers

In myocardial ischemia beta-blockers reduce myocardial oxygen demand, improve flow toward ischemic regions, and have mild antiplatelet and antiarrhythmic effects. These agents are effective in chronic stable angina and unstable angina. In chronic myocardial ischemia, the beta-blockers timolol, metoprolol, atenolol, and propranolol have cardioprotective effects, reducing overall mortality and the incidence of recurrent myocardial infarction. Calcium channel blockers, which reduce myocardial oxygen demand and improve oxygen supply, are effective in the treatment of chronic stable angina, vasospastic angina, and unstable angina. Although calcium channel blockers generally have no effect or adverse effects when used as primary therapy for acute myocardial infarction, diltiazem (when used concomitantly with nitrates or beta-blockers) has been shown to reduce the incidence of reinfarction in patients after non-Q wave myocardial infarction.

Acute myocardial infarction: initial manifestations, management, and prognosis

In patients with suspected acute myocardial infarction (AMI), obtaining a thorough history is important for identifying both the cause of chest pain and any concurrent conditions that may complicate the management. Physical examination--including cardiac auscultation and determining the status of the peripheral vasculature--is important as a guide to immediate management and as a baseline for future comparison. The differential diagnosis of AMI is extensive, and various laboratory tests, such as electrocardiography, cardiac enzymes, radionuclide techniques, echocardiography, and cardiac catheterization, can aid in the diagnosis. The routine management of patients with AMI can include medical therapy with antithrombotic agents, nitrates, beta-adrenergic blockers, or calcium channel blocking agents. The major differences between Q-wave and non-Q-wave infarction are discussed. Some factors that affect early and late prognosis in patients with AMI are age of the patient, residual left ventricular function, residual myocardial ischemia, and substrates for sustained ventricular arrhythmias. Although much of the current enthusiasm in management of AMI is related to revascularization strategies, other important aspects of diagnosis and treatment should not be overlooked.

Early estimation of risk by echocardiographic determination of wall motion index in an unselected population with acute myocardial infarction

In a prospective series of 201 consecutive patients with creatine kinase-MB--documented acute myocardial infarction (AMI), postadmittance and predischarge echocardiographic wall motion indexes (WMI) were determined (median 45 hours vs 14 days after AMI). No significant change of left ventricular systolic performance was found between postadmittance and predischarge examinations in 179 survivors (WMI 1.3 +/- 0.4 vs 1.4 +/- 0.4, p greater than 0.05). Hospital mortality was 11% (22 of 201), cumulated 2-month mortality 15% (31 of 201) and cumulated 1-year mortality 26% (52 of 201). Mortality increased rapidly with decreasing left ventricular function as determined by WMI. When early WMI was less than 1.0, 1-year mortality was 51% (28 of 55) versus 8% (7 of 83) when WMI was greater than 1.3 (p less than 0.0001). Ventricular fibrillation (n = 24) and cardiogenic shock (n = 27) carried a much better prognosis when WMI showed good left ventricular function. When WMI was less than 1.0, 1-year mortality was 83% (10 of 12) versus 93% (13 of 14) in ventricular fibrillation and cardiogenic shock, respectively, whereas it was 0% (0 of 4) versus 33% (2 of 6) when WMI was greater than 1.3. In 15% of patients major discrepancies between early Killip class and WMI were noted. WMI showed much smaller fluctuations during the hospital course of AMI than did Killip class and appeared to be a more stable prognostic marker. Large-scale, early risk stratification by echocardiography has now become available and appears to facilitate a rational, individualized discharge policy in the coronary care unit and to provide an improved basis for randomization of patients in controlled studies aimed at tailoring new treatment in AMI.

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.

Myocardial infarction: is bepridil, a new calcium antagonist, able to improve the course of the acute phase?

Several calcium antagonists are useful in the treatment of ischemic heart disease. This open randomized study was designed to determine the effects of bepridil, a new long-acting calcium antagonist with antiarrhythmic properties, on the course of acute myocardial infarction (AMI). Two hundred patients with AMI of less than 48 hours duration (average 10.9 hours) were randomly assigned to two treatment groups: The first one was treated with bepridil (BEP, n = 100), and the second one was considered as a control group, using isosorbide dinitrate at a low dosage (ISDN, n = 100). BEP was administered intravenously for 48 hours at a dosage of 4 mg/kg/day; at the same time, an oral dose of 200 mg t.i.d. was started and continued for 21 days. In the control group, ISDN was given orally at the low dosage of 5 mg every 4 hours for 21 days. An uneventful course was seen in 28 BEP patients versus 15 in the control group (p less than 0.05). Mortality and recurrence of angina were lower in the BEP group than in the control group, but the difference is not significant. On the other hand, moderate and severe hemodynamic complications did not occur in 80 BEP patients versus 65 in the control group (p less than 0.05). Ventricular arrhythmias occurred in 36 BEP patients versus 50 in the control group (p less than 0.05). Antiarrhythmic therapy was required in 14 BEP patients versus 61 in the control group (p less than 0.001). These results show that bepridil seems capable of improving the hemodynamics and arrhythmologic course of AMI.

Calcium antagonists in acute myocardial infarction

Calcium antagonists have proved effective in stable angina, unstable angina and vasospastic angina. However, despite a strong theoretical rationale for their use and promising experimental data, these agents have not reduced infarct size in acute myocardial infarction (AMI) in the large clinical trials performed to date. Their role as adjunctive therapy in combination with reperfusion needs to be examined. Diltiazem has been demonstrated to reduce angina and reinfarction in the 2-week period after AMI in patients receiving multidrug therapy. Results of the single large trial of a calcium antagonist (verapamil) for secondary prevention after AMI were negative; however, several well-designed studies are currently ongoing.

Myocardial infarct expansion, infarct extension, and reinfarction: pathophysiologic concepts

Infarct expansion and infarct extension are events early in the course of myocardial infarction with serious short- and long-term consequences. Infarct expansion, disproportionate thinning, and dilatation of the infarct segment probably begin within hours of acute infarction and usually reach peak extent within seven to 14 days. Clinical data suggest that infarct expansion occurs in approximately 35% to 45% of anterior transmural myocardial infarctions and to a lesser extent in infarctions at other sites. Although expansion usually develops in large infarcts, the extent of transmural necrosis rather than absolute infarct size predicts its occurrence. Expansion has an adverse effect on infarct structure and function for several reasons. Functional infarct size is increased because of infarct segment lengthening, and expansion results in over-all ventricular dilatation. Thus, patients with expansion of an infarct have poorer exercise tolerance, more congestive heart failure symptoms, and greater early and late mortality than those without expansion. Infarct rupture and late aneurysm formation are two additional structural consequences of infarct expansion. Experimental and clinical data suggest that the incidence and severity of expansion can be modified by interventions. Increased ventricular loading conditions and steroidal and nonsteroidal antiinflammatory agents make expansion more severe. Reperfusion of the infarct segment and pharmacologic interventions that decrease ventricular afterload lessen the severity of expansion. Previous myocardial infarction and preexisting ventricular hypertrophy may also limit the development of infarct expansion. Infarct extension is defined clinically as early in-hospital reinfarction after a myocardial infarction. The pathologic finding of infarct extension is necrotic and healing myocardium of several different recent ages within the same vascular territory. Although this pathologic criterion usually cannot be verified, studies employing invasive and noninvasive assessment of patients with early reinfarction provide evidence that the new myocardial injury is usually in the same vascular risk region as the original infarction. A variety of different criteria have been applied in the clinical diagnosis of infarct extension, and this has resulted in a large range of estimated frequencies from under 10% to as high as 86%. High estimates are found in studies using one or two nonspecific criteria such as ST segment shift or reelevation of total CK. The lowest rates have been found when combinations of criteria are used.(ABSTRACT TRUNCATED AT 400 WORDS)

Calcium antagonists and the ischemic myocardium

Recent laboratory studies have shown that the calcium antagonists (slow channel blockers) can protect the myocardium against the consequences of experimentally induced ischemia and reperfusion. With one recent exception, however, clinical trials relating to the effectiveness of these drugs in the management of patients with myocardial infarction have been disappointing. This paper explores this apparent discrepancy.

Effects of calcium antagonists on infarcting myocardium

Numerous studies have been conducted over the past 10 years on the effects of calcium antagonists on regional myocardial ischemia and infarct size. Verapamil, for example, reduced the degree of adenosine triphosphate degradation during 15 minutes of coronary occlusion followed by reperfusion in an anesthetized canine preparation. It also preserved the ultrastructural appearance of mitochondria in myocardium subjected to 1 hour of ischemia. Using an 8-hour permanent coronary artery occlusion model in which risk zone was assessed with radioactive microspheres and infarct size determined by tetrazolium staining, verapamil, administered 1 hour after occlusion, resulted in a modest decrease in infarct size. In a reperfusion model in which anesthetized dogs were subjected to 3 hours of coronary artery occlusion followed by 3 hours of reperfusion, verapamil decreased infarct size when it was administered during the period of ischemia, but failed to decrease infarct size when administered only during the reperfusion phase, i.e., after 3 hours of ischemia. Although verapamil is known to have negative inotropic effects, the newer calcium antagonist agent nisoldipine is less negatively inotropic, and might therefore be preferable in the situation of compromised hemodynamics. In a 6-hour permanent coronary artery occlusion model, nisoldipine decreased infarct size without decreasing left ventricular contractility. Most published reports support the concept that calcium antagonists decrease infarct size in models of experimental infarction. Of 4 major clinical studies, only 1 has shown that calcium antagonists are capable of reducing infarct size in man. However, in most of these studies, drug therapy commenced relatively late--4 or more hours after symptoms. In order for these drugs to demonstrate beneficial effects, the risk zone may have to be small and the degree of collateral flow adequate, the drug may have to be given very early or even before coronary occlusion (in a prophylactic fashion) and administration of the drug may have to be coupled to early coronary reperfusion.

Diltiazem and reinfarction in patients with non-Q-wave myocardial infarction. Results of a double-blind, randomized, multicenter trial

We performed a multicenter, double-blind, randomized study to evaluate the effect of diltiazem on reinfarction after a non-Q-wave myocardial infarction. Nine centers enrolled 576 patients: 287 received diltiazem (90 mg every six hours) and 289 received placebo. Treatment was initiated 24 to 72 hours after the onset of infarction and continued for up to 14 days. The primary end point, reinfarction, was defined as an abnormal reelevation of MB creatine kinase in plasma within 14 days. Reinfarction occurred in 27 patients in the placebo group (9.3 percent) and in 15 in the diltiazem group (5.2 percent)--a 51.2 percent reduction in cumulative life-table incidence (P = 0.0297; 90 percent confidence interval, 7 to 67 percent). Diltiazem reduced the frequency of refractory postinfarction angina (a secondary end point) by 49.7 percent (P = 0.0345; 90 percent confidence interval, 6 to 73 percent). Mortality was similar in the two groups (3.1 and 3.8 percent, respectively, in the placebo and diltiazem groups), but adverse drug reactions (most of which were mild) were more common in the diltiazem group. Nevertheless, the drug was well tolerated, despite concurrent treatment with beta-blockers in 61 percent of the patients. We conclude that diltiazem was effective in preventing early reinfarction and severe angina after non-Q-wave infarction and that it was also safe and generally well tolerated.

Management of acute myocardial infarction

This article presents plans of therapy based on current knowledge of pathophysiologic mechanisms, taking into consideration the rapid changes in availability of new drugs (or new experiences with old drugs) and new therapeutic interventions. Persistence of ischemic pain in the acute phase, or its recurrence during early convalescence, is a signal of a high-risk state for additional coronary events, and aggressive measures are required to prevent them. The indications, and the role of invasive hemodynamic monitoring in the treatment of left ventricular failure and/or hypotension, are discussed.