Secondary prevention after myocardial infarction: a review of short-term acute phase trials

Changing patterns of medical treatment in acute myocardial infarction

TYPE OF STUDY

Descriptive study of trends in the drug therapy for acute myocardial infarction.

SETTING

Population-based register of acute coronary events compiled for the years 1984 to 1990 in the course of the Perth MONICA project.

CASES

5294 cases meeting clinical criteria for acute myocardial infarction.

RESULTS

Striking changes were seen in the use of aspirin before admission to hospital (from 4% to 18%). During the stay in hospital the use of beta-blockers increased steadily from 52% to 76%, while the use of aspirin increased 3.5-fold from 25% to 88% and the use of streptokinase increased 13.5-fold from 2.4% to 32.4%. The proportion of patients prescribed beta-blockers on discharge from hospital increased from 46% to 65% and that for aspirin rose from 16% to 83%. There were also major relative increases in the use of lipid-lowering agents and declines in the use of antiarrhythmic drugs.

CONCLUSION

These trends in the pharmacological management of myocardial infarction mirror the emerging evidence from clinical trials, although the increases in the use of certain types of drugs antedated publication of the results of major randomised studies. The changes in therapy would partly explain observed improvements in case fatality and may have contributed to the decline in coronary mortality observed in the Perth community.

Systematic reviews in context: highlighting systematic reviews relevant to Africa in the Pan African Medical Journal

Health research serves to answer questions concerning health and to accumulate facts (evidence) required to guide healthcare policy and practice. However, research designs vary and different types of healthcare questions are best answered by different study designs. For example, qualitative studies are best suited for answering questions about experiences and meaning; cross-sectional studies for questions concerning prevalence; cohort studies for questions regarding incidence and prognosis; and randomised controlled trials for questions on prevention and treatment. In each case, one study would rarely yield sufficient evidence on which to reliably base a healthcare decision. An unbiased and transparent summary of all existing studies on a given question (i.e. a systematic review) tells a better story than any one of the included studies taken separately. A systematic review enables producers and users of research to gauge what a new study has contributed to knowledge by setting the study’s findings in the context of all previous studies investigating the same question. It is therefore inappropriate to initiate a new study without first conducting a systematic review to find out what can be learnt from existing studies. There is nothing new in taking account of earlier studies in either the design or interpretation of new studies. For example, in the 18th century James Lind conducted a clinical trial followed by a systematic review of contemporary treatments for scurvy; which showed fruits to be an effective treatment for the disease. However, surveys of the peer-reviewed literature continue to provide empirical evidence that systematic reviews are seldom used in the design and interpretation of the findings of new studies. Such indifference to systematic reviews as a research function is unethical, unscientific, and uneconomical. Without systematic reviews, limited resources are very likely to be squandered on ill-conceived research and policies. In order to contribute in enhancing the value of research in Africa, the Pan African Medical Journal will start a new regular column that will highlight priority systematic reviews relevant to the continent.

Depression and medication adherence in outpatients with coronary heart disease: findings from the Heart and Soul Study

BACKGROUND

Depression leads to adverse outcomes in patients with coronary heart disease (CHD). Medication nonadherence is a potential mechanism for the increased risk of CHD events associated with depression, but it is not known whether depression is associated with medication nonadherence in outpatients with stable CHD.

METHODS

We examined the association between current major depression (assessed using the Diagnostic Interview Schedule) and self-reported medication adherence in a cross-sectional study of 940 outpatients with stable CHD.

RESULTS

A total of 204 participants (22%) had major depression. Twenty-eight (14%) of 204 depressed participants reported not taking their medications as prescribed compared with 40 (5%) of 736 nondepressed participants (odds ratio [OR], 2.8; 95% confidence interval [CI], 1.7-4.7; P<.001). Twice as many depressed participants as nondepressed participants (18% vs 9%) reported forgetting to take their medications (OR, 2.4; 95% CI, 1.6-3.8; P<.001). Nine percent of depressed participants and 4% of nondepressed participants reported deciding to skip their medications (OR, 2.2; 95% CI, 1.2-4.2; P = .01). The relationship between depression and nonadherence persisted after adjustment for potential confounding variables, including age, ethnicity, education, social support, and measures of cardiac disease severity (OR, 2.2; 95% CI, 1.2-3.9; P = .009 for not taking medications as prescribed).

CONCLUSIONS

Depression is associated with medication nonadherence in outpatients with CHD. Medication nonadherence may contribute to adverse cardiovascular outcomes in depressed patients.

Modification of high blood pressure after myocardial infarction

The treatment of high blood pressure (BP) after myocardial infarction is extremely important to decrease reinfarction and mortality. BP should be controlled more strictly in this high-risk hypertensive population. Recently, many clinical trials have demonstrated the benefits of lifestyle modification and antihypertensive agents, particularly beta-blockers and angiotensin-converting-enzyme inhibitors for the treatment of acute myocardial infarction. Treatment with these agents that modify BP may benefit even normotensive patients after a myocardial infarction, although the benefit is greater in hypertensives.

Secondary prevention of myocardial infarction: role of beta-adrenergic blockers and angiotensin-converting enzyme inhibitors

beta-Blockers reduce cardiovascular death and reinfarction in patients with a history of myocardial infarction (MI), and angiotensin-converting enzyme (ACE) inhibitors provide an overall survival benefit in patients with signs or symptoms of left ventricular (LV) dysfunction and a history of acute MI. Despite this, these agents remain underused in clinical practice. Appropriate patient selection in standard clinical practice should be encouraged in order to achieve a mortality rate reduction comparable to that seen in clinical trials. It appears from the findings of recent studies that the greatest benefit from beta-blocker therapy is achieved in patients who are more than 60 years of age and in patients at moderate or high risk for reinfarction and death (eg, patients with LV dysfunction or arrhythmias or both). Patients with class I-IV heart failure treated with ACE inhibitors have fewer recurrent infarctions, a lower incidence of severe congestive heart failure, and a reduced incidence of total cardiovascular death and sudden cardiac death. In addition to the studies completed in patients with MI, there are ongoing studies evaluating whether or not ACE inhibitors can reduce myocardial ischemic events in patients without a prior infarction who have coronary artery disease or hypertension and preserved LV function. There is also growing evidence that concomitant therapy with a beta-blocker and an ACE inhibitor may reduce mortality rates beyond that observed with ACE inhibitors alone in survivors of MI who have LV dysfunction.

Can antiarrhythmic drugs survive survival trials?

Sudden cardiac death due to arrhythmic events is the major cause of mortality among early post-myocardial infarction (MI) patients, accounting for > 250,000 deaths annually in the United States alone. Antiarrhythmic drugs can be used in such patients as well as in those who have not had a recent MI but are at high risk for sudden cardiac death (e.g., those with ventricular tachycardia/fibrillation, or who have survived cardiac arrest). Most antiarrhythmic drugs available, however, have limitations arising from their toxic and proarrhythmic potential. Thus, research and development of new agents and treatment modalities are desirable. This article seeks to enumerate the lessons of past clinical trials with these agents and to provide guidelines for future trials. That a variety of antiarrhythmic drugs have been associated with an increased mortality has been a disturbing observation. It is therefore imperative that candidates for antiarrhythmic therapy be selected appropriately. We recommend that future clinical trials use stringent criteria for the identification of patients at "high risk" for arrhythmia or sudden cardiac death, and limit recruitment to such patients. Traditional markers, such as the increased frequency and complexity of ventricular premature beats, and low left ventricular ejection fraction, have not been successful in identifying these high-risk patients. However, decreased heart rate variability and cardiac late potentials recorded on a signal-over-aged electrocardiogram appear to be more specific markers of post-MI arrhythmia or sudden cardiac death and may, in conjunction with the traditional markers, be used to improve selection of trial populations. Since the risk of sudden cardiac death diminishes with time after MI, it is also recommended that the temporal window of treatment with antiarrhythmic agents be limited to 1 year post-MI. It is also important to define clearly the endpoints of efficacy evaluations. A short-term reduction on markers like ventricular ectopic beats, for example, does not translate into a long-term decrease in arrhythmia-related mortality. Therefore, a reduction in overall mortality is the only meaningful endpoint to define the true risk-benefit ratio. To limit exposure to the potentially adverse effects of these agents, target populations for prophylactic antiarrhythmic drugs should be limited to recent post-MI patients at high risk for sudden cardiac death due to arrhythmia. Avoiding exposure of low-risk patients to antiarrhythmic drugs is equally imperative. "Low risk" of all-cause mortality includes the group of post-MI patients with a left ventricular ejection fraction >36%. Risk must be continuously evaluated in the setting of other pharmacologic (angiotensin-converting enzyme [ACE] inhibitors, aspirin, 3-hydroxy-3-methylglutaryl coenzyme A reductase inhibitors ["statins"], and others) and/or nonpharmacologic interventions (coronary artery bypass graft, angioplasty, implantable cardioverter/defibrillator). There is also a need to improve noninvasive techniques for identifying patients in the high-risk category-at present, the presence of ventricular premature beats and a left ventricular ejection fraction <36% is considered somewhat predictive of sudden cardiac death. Thus, patients with a recent MI and moderately low left ventricular ejection fraction (< or = 36% but not <20%) may be considered for antiarrhythmic therapy. A subset analysis of patients with low heart rate variability can provide valuable additional information. It is important to note that although all-cause mortality is a valid endpoint for such trials, stratification by specific cause of mortality is desirable.

Antiarrhythmic versus antifibrillatory actions: inference from experimental studies

Pathophysiology of the coronary circulation is a major contributor to altering the myocardial substrate, rendering the heart susceptible to the onset of arrhythmias associated with sudden cardiac death. Antiarrhythmic drug therapy for the prevention of sudden cardiac death has been provided primarily on the basis of trial and error and in some instances based on ill-suited preclinical evaluations. The findings of the Cardiac Arrhythmia Suppression Trial (CAST) requires a reexamination of the manner in which antiarrhythmic drugs are developed before entering into clinical testing. The major deficiency in this area of experimental investigation has been the lack of animal models that would permit preclinical studies to identify potentially useful or deleterious therapeutic agents. Further, CAST has emphasized the need to distinguish between pharmacologic interventions that suppresses nonlethal disturbances of cardiac rhythm as opposed to those agents capable of preventing lethal ventricular tachycardia or ventricular fibrillation. Preclinical models for the testing of antifibrillatory agents must consider the fact that the superimposition of transient ischemic events on an underlying pathophysiologic substrate makes the heart susceptible to lethal arrhythmias. Proarrhythmic events, not observed in the normal heart, may become manifest only when the myocardial substrate has been altered. We describe a model of sudden cardiac death that may more closely simulate the clinical state in humans who are at risk. The experimental results show a good correlation with clinical data regarding agents known to reduce the incidence of lethal arrhythmias as well as those showing proarrhythmic actions.

Frequency and prognostic significance of secondary ventricular fibrillation complicating acute myocardial infarction. SPRINT Study Group

The incidence of secondary ventricular fibrillation (VF) complicating acute myocardial infarction (AMI) was 2.4% in a large cohort of unselected patients with AMI (142 of 5,839). Secondary VF was more frequent in patients with recurrent AMI (4%) than in those with a first AMI (1.9%) (p < 0.01). The hospital course was more complicated and in-hospital mortality was significantly higher in patients with secondary VF than in those with the same clinical hemodynamic condition but without VF (56 vs 16%; p < 0.0001). Multivariate analyses confirmed secondary VF complicating AMI as an independent predictor of high in-hospital mortality, with an odds ratio of 7 (95% confidence interval 4.6-10.6). However, long-term mortality after discharge (mean follow-up 5.5 years) was not increased in patients with as compared with those without secondary VF (39 vs 42%). These findings were also true when patients receiving beta blockers and antiarrhythmic therapy were excluded from analysis. Thus, this life-threatening arrhythmia occurring during hospitalization is not a marker of recurrent susceptibility to VF or an indicator of increased mortality after discharge from the hospital.

Reperfusion-induced arrhythmias and myocardial ion shifts: a pharmacologic interaction between pinacidil and cicletanine in isolated rat hearts

Pinacidil is a member of the new antihypertensive drug family possessing an action that involves an increased potassium efflux in vascular and cardiac muscle. We investigated the contribution of opening of ATP-sensitive potassium channel to the development of reperfusion-induced arrhythmias and myocardial ion shifts, particularly that of Na+, K+, Ca2+, and Mg2+ in isolated rat hearts. After 30 min of normothermic global ischemia, pinacidil with 1 to 60 mumol/l failed to reduce the incidence of reperfusion-induced arrhythmias, even on the postischemic/reperfused myocardium in a subset of hearts unresponsive to reperfusion-induced arrhythmias (the duration of ischemia was reduced to 25 min), pinacidil treatment was associated with a greater incidence of reperfusion-induced arrhythmias (100%) as compared to the control value (50%). These proarrhythmic effects of pinacidil were also reflected in a maldistribution of myocardial ion contents both in nonischemic and ischemic/reperfused hearts. Cicletanine, a furopyridine antihypertensive agent that has no effect on coronary resistance, reduced the incidence of reperfusion arrhythmias, and its antiarrhythmic effect was antagonized by pinacidil. The same observation was made in relation to myocardial ion content, e.g., pinacidil-induced K+ loss and Ca2+ gain were antagonized by cicletanine, both in nonischemic and ischemic/reperfused hearts. It is hypothesized that the increased tendency to develop reperfusion-induced ventricular fibrillation is associated with the pinacidil-induced K+ efflux. The present study does not attempt to address the question of specific ionic currents; however, it has been suggested that proarrhythmic and antiarrhythmic effects of pinacidil and cicletanine, respectively, may relate to same receptor sites in which the latter may reflect a specific blockade of the outward K+ ion current via ATP-sensitive K+ channels. If this is so, the use of K+ channel openers as antihypertensive agents may be of particular concern in that population of postinfarction patients who are known to be at high risk of sudden coronary death.

Metabolic, hemodynamic, and electrocardiographic responses to increased circulating adrenaline: effects of pretreatment with class 1 antiarrhythmics

In order to study the effects of treatment with class 1 antiarrhythmics on the metabolic, hemodynamic, and electrocardiographic responses to adrenaline, 12 healthy volunteers were infused on four occasions, after pretreatment with placebo, disopyramide, mexiletine, and flecainide, respectively, with adrenaline at a rate producing serum adrenaline concentrations comparable with those seen in acute myocardial infarction. After pretreatment with placebo adrenaline caused significant falls in serum potassium, serum magnesium, serum calcium, and serum phosphate and a significant increase in blood glucose. Adrenaline also caused a significant increase in heart rate and systolic blood pressure and a significant fall in diastolic blood pressure. On the electrocardiogram a significant prolongation of QTc duration and a flattening of the T-wave amplitude were seen. Pretreatment with disopyramide had no effect on the hemodynamic response to adrenaline but caused a significant prolongation of Qtc duration before the adrenaline infusion. Pretreatment with mexiletine was associated with a significantly greater fall in serum potassium during adrenaline infusion, and pretreatment with flecainide with a greater fall in serum magnesium, as compared with placebo pretreatment Flecainide also caused a significant prolongation of the QRS duration before adrenalin infusion, and after all the active pretreatments a prolongation of QRS duration was seen during adrenaline infusion. The metabolic and hemodynamic changes during adrenaline infusion may not only reduce the antiarrhythmic efficacy of antiarrhythmics but may also increase the risk of proarrhythmic effects in a clinical setting. These results may help to explain why treatment with antiarrhythmics seems to be without beneficial effect on mortality in post-myocardial infarction patients.

Noninvasive and invasive testing after myocardial infarction

Recurrent myocardial ischemia, moderate to marked depression of left ventricular systolic function, and late-occurring or recurrent cardiac arrhythmia indicate increased risk for patients with acute myocardial infarction. Some patients, on the basis of high risk and/or unsuccessful response, will be early candidates for early aggressive diagnostic and therapeutic procedures. Others will have clinical indicators of increased risk during hospitalization that warrant diagnostic coronary arteriographic assessment before discharge. Still other patients with low risk clinical characteristics can be further stratified by predischarge or early postdischarge stress testing for myocardial ischemia, left ventricular functional reserve, and/or likely occurrence of arrhythmias. Some stratified to low risk patients will be treated only with secondary prevention measures. Others at higher risk will undergo more aggressive evaluation and subsequent medical or surgical therapy.

Reduction of mortality, sudden death and non-fatal reinfarction with beta-adrenergic blockers in survivors of acute myocardial infarction: a new hypothesis regarding the cardioprotective action of beta-adrenergic blockade

Beta-adrenergic blockers have been shown definitely to reduce the incidence of total mortality, cardiovascular mortality, sudden death and nonfatal reinfarction in survivors of an acute myocardial infarction. The mechanisms to explain this protective action of beta blockers have never been elucidated conclusively, and include the antiarrhythmic and myocardial oxygen demand-reducing effects of the drugs. An antithrombotic mechanism has also been suggested. However, beta blockers have relatively weak antiplatelet activity, suggesting that their antithrombotic effects may be related to prevention of coronary artery plaque rupture and the subsequent propagation of an occlusive arterial thrombus rather than direct anticoagulant action. The therapeutic ability of beta blockers to attenuate the hemodynamic consequences of catecholamine surges, may protect a vulnerable atherosclerotic plaque from fracture, thereby reducing risk of coronary thrombosis, myocardial infarction and death.

A method for monitoring the effectiveness of allopurinol pretreatment in the prevention of ischemic/reperfusion injury

The protective actions of allopurinol in ischemic/reperfusion injury seem critically determined by the drug pretreatment regimen and may involve generalized alterations in tissue antioxidant status. In the present study, 12 male swine to be used as donors and recipients in a heart-lung transplantation study were treated with allopurinol given orally at a dose of 50 mg/kg for 4 days prior to surgery. Red cells from allopurinol-treated animals showed a progressive decrease in susceptibility to in vitro peroxidative challenge. Although the degree and time-course of protection showed some degree of interanimal variation, maximal effects were obtained in most animals after 2-3 days. The extent of red cell protection in both donor and recipient animals correlated significantly with the functional viability of the transplanted lung, as assessed by tissue water content. It is suggested that the susceptibility of red cells to in vitro oxidative damage may provide a useful functional assessment of generalized alterations in antioxidant status produced by pharmacological interventions.

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.

Atenolol, but not mexiletine, protects against stimulus-induced ventricular tachycardia in a chronic canine model

1. In a placebo-controlled study of the antiarrhythmic and electrophysiological properties of atenolol and mexiletine, programmed electrical stimulation (PES) was performed in three groups of six conscious greyhounds, 7-30 days after coronary artery ligation. 2. In the placebo group, repeated PES challenge resulted in the consistent induction of ventricular tachycardias (VT) in 4/6 dogs and ventricular fibrillation in 2/6. Atenolol prevented arrhythmia induction in 4/6 dogs, one continued to demonstrate a VT and one died (P less than 0.05 compared with placebo). In the mexiletine group 5/6 dogs continued to demonstrate a VT and one died. 3. Electrocardiographic parameters were not affected by any treatment. There was no change in blood pressure in any group but when compared with placebo, heart rate fell (P less than 0.05) after atenolol (256 micrograms kg-1) and increased (P less than 0.05) after mexiletine (16 mg kg-1). Effective (ERP) and functional (FRP) refractory periods did not change after mexiletine, but ERP was prolonged (P less than 0.05) after atenolol. 4. The results indicate that atenolol but not mexiletine is effective in preventing re-entrant arrhythmias in this conscious canine model. Antiarrhythmic efficacy may be related to a fall in heart rate and/or a prolongation of refractoriness.

Resolving conflicting clinical trials: guidelines for meta-analysis

Contradictory results among randomized clinical trials addressing similar questions are common and occur when the conclusions of different groups of investigators disagree, or when the results of several trials are statistically inconclusive. Meta-analysis, a term used to describe the process of evaluating and combining the results of conflicting studies, has been proposed as a method for reconciling the contradictory results. In this review of meta-analyses, we distinguish between the pooled and methodologic techniques, described the highly variable strategies used, and propose guidelines for improving the conduct of meta-analyses. In pooled analyses the results of multiple clinical trials are combined and the outcome is compared for patients receiving the principal and comparative therapy. In methodologic analyses the clinical trials are judged according to a set of standards used to assess scientific validity and clinical applicability. Since neither technique alone appeared satisfactory for resolving the conflicting results, we propose an approach to meta-analysis that requires methodologic criteria to identify scientifically valid studies, and pooling criteria to combine data from each of the studies. We believe this new strategy of meta-analysis will have enhanced scientific validity and clinical applicability.

Metoprolol in acute myocardial infarction reduces ventricular arrhythmias both in the early stage and after the acute event

Fifty three of the 5778 patients included in the MIAMI (Metoprolol in Acute Myocardial Infarction) trial were investigated with long-term ECG recordings in order to evaluate the effect of acute beta-blockade on premature ventricular complexes in and after acute myocardial infarction. Twenty five patients were given placebo and 28 metoprolol in a double-blind randomized fashion for 15 days. After this period the patients were put on open beta-blockade without breaking individual study codes. The mean number of premature ventricular complexes during the inclusion day (day 0) was the same in the two groups. The median numbers were also similar in the two groups: 190 and 154 in the placebo and metoprolol groups, respectively. Metoprolol significantly reduced the median number of premature ventricular complexes in the randomized period. The median numbers on days 1, 2 and 15 were 146, 101, 84 in the placebo group and 73, 59 and 10 in the metoprolol group, respectively (P less than 0.05). Also during the further follow-up, when investigated 1, 3 and 6 months after the infarction, the median number of premature ventricular complexes was lower in the metoprolol group (74, 257, 142 in the placebo group and 7, 5 and 11 in the metoprolol group, P less than 0.05). This indicates that metoprolol treatment in the acute phase of myocardial infarction reduces ventricular arrhythmias both in the early stage and also after the acute event.

Methods for combining randomized clinical trials: strengths and limitations

Methods for combining data from several studies exist and appear to be quite useful. None satisfactorily addresses the question of what studies should be combined. This issue is the most serious methodological limitation. Even studies with statistically significant interaction might still be combined if the effect were in the same direction. Thus, substantial scientific input is required as to what criteria must be met by each potential study. Much can be learned from combining or pooling data but it must be done cautiously. Pooling exercises do not replace well designed prospective clinical trials. Efforts for establishing basic design criteria to allow for multicentre and multicountry trials to be more easily combined might be useful.

Long-term prognosis of patients with acute myocardial infarction: is mortality and morbidity as low as the incidence of ischemic heart disease in Japan

Long-term prognosis of hospital survivors with myocardial infarction (MI) was investigated to assess the validity of previous reports on the low incidence of ischemic heart disease in Japan. Among 686 patients with acute MI, 115 (16.8%) died during hospitalization and eight were lost to follow-up. The cumulative mortality rate of the 563 hospital survivors was 6.2% in the first year, 12.0% in the third year, and 19.1% in the fifth year, with cardiac death accounting for 63% of the deaths. Cumulative rates for recurrent MI were 4.4% in the first year, 11.0% in the third year, and 13.2% in the fifth year. Parameters influencing long-term mortality rates obtained by stepwise discriminant analysis were arteriosclerosis-related factors, presence of congestive heart failure at admission, age, and presence of previous MI, while parameters influencing the recurrence of MI were congestive heart failure, arteriosclerosis-related factors, and ischemic findings at discharge. Our findings indicate that the prognosis for patients with MI is far better in Japan than in Western countries and support the previous reports on the low incidence of ischemic heart disease in Japan, while factors influencing the prognosis are similar to those previously reported.

Lessons from overviews of cardiovascular trials

Overviews of clinical trials in the cardiovascular field have been critically reviewed. Six reasons for the overviews were identified. An impression, at least from a scientific viewpoint, is that the pooled analyses have been valuable. Six potential problems are discussed and recommendations given based on lessons learned. These include the avoidance of three types of biases--publication bias, overviewer bias and investigator bias. The role of time-dependent treatment effects, the complex issue of 'mixing of apples and oranges' and the problem of errors are also addressed.

Coronary artery thrombus as a risk factor for acute vessel occlusion during percutaneous transluminal coronary angioplasty: improving results

Early experience with percutaneous transluminal coronary angioplasty (from October 1979 to March 1983 inclusive) showed that pre-existing coronary artery thrombus was associated with a significant increase in the incidence of acute coronary occlusion during angioplasty. Acute occlusion occurred in 11 (73%) of 15 patients with pre-existing thrombus compared with 18 (8%) of 223 patients without thrombus. The effect of improved technology (steerable guiding systems) and altered dilatation strategy (full intravenous heparinisation for 24 hours after the procedure and more intensive use of antiplatelet medications) was studied by review of angiograms from 297 consecutive patients without evidence of acute myocardial infarction who underwent angioplasty from April 1983 to March 1985 inclusive. Coronary artery thrombus was present in 34 (11%) patients, eight (24%) of whom had complete occlusion during or immediately after the procedure compared with 34 (13%) of 263 patients without thrombus. Patients with pre-existing coronary artery thrombus continue to be at greater risk of complete occlusion than patients without thrombus, but this risk has declined significantly since the modification of the angioplasty procedure.

Prediction of coronary events following myocardial infarction using a discriminant function analysis

This study was undertaken to derive an index for predicting coronary events in the first year after a myocardial infarction in "low-risk" patients enrolling in a Cardiac Rehabilitation Program. Data from 145 consecutive patients were analysed. The events were classified as follows: angina requiring further therapy, re-infarction and coronary death. Seventy patients had events: Angina--52, Re-infarction--8, Coronary Death--10. A discriminant function analysis was performed to predict such events using data available at the time of discharge from hospital. The following were significant predictors: (1) previous infarction/angina, (2) radiological evidence of cardiomegaly or lung congestion in the Coronary Care Unit, (3) Non-Q wave infarction and (4, 5 and 6) angina, atrial arrhythmias and a decrease in R wave amplitude in V5 during a pre-discharge exercise test. The jack-knife method classified correctly 71.2% of those with events and 72.6% of those without events. In patients with discriminant scores greater than +0.2, 82% developed events.

Use of beta-adrenergic blocking agents after myocardial infarction

Long-term clinical trials have been carried out to evaluate the effectiveness of beta-adrenergic blocking agents in modifying the natural history of myocardial infarction (MI). In most of these studies, a lower mortality rate was documented in patients receiving a beta-blocker than in those receiving placebo. The drugs may have both antiarrhythmic and antiischemic effects. In patients without contraindications to beta-blocker treatment, a relative reduction in mortality of 25% can be expected for at least one to two years, with the reduction higher in older patients or patients having complications at infarction. Study results indicate benefit from starting beta-blocker therapy early after infarction, and some benefit from starting late seems a reasonable assumption. Evidence also points to a benefit from prolonged therapy. Beta-blockers are well tolerated in most patients; those major side effects that do occur are often cardiovascular.

Percutaneous transluminal coronary angioplasty after intracoronary streptokinase in evolving acute myocardial infarction

To achieve optimal myocardial revascularization and prevent rethrombosis of the infarct-related coronary artery, percutaneous transluminal coronary angioplasty (PTCA) was attempted in 18 patients with evolving acute myocardial infarction (9 anterior and 9 inferior) after administration of intracoronary streptokinase. PTCA was attempted 338 +/- 151 minutes after the onset of symptoms. After thrombolytic therapy, 11 patients had a severe residual stenosis and 7 a persistent total occlusion of the infarct-related coronary artery. PTCA was successful in 13 of 18 patients: in 9 of 11 with coronary stenoses and in 4 of 7 with total coronary occlusions. PTCA reduced the severity of the coronary lesion from 91 +/- 2% to 27 +/- 7% (p less than 0.001), and the transstenotic pressure gradient from 38 +/- 5 to 6 +/- 2 mm Hg (p less than 0.01). One patient in cardiogenic shock died during urgent coronary surgery after unsuccessful PTCA. After PTCA, all patients received heparin and antiplatelet agents. One patient had reinfarction with reocclusion of the infarct-related artery 5 days after PTCA. The other 12 patients had an uneventful hospital course, and cardiac catheterization before hospital discharge (8 to 17 days) revealed reocclusion of the infarct-related coronary artery in 3 and persistent patency in 9. Persistent patency of the infarct-related artery was associated with preservation of left ventricular end-diastolic volume (initial 86 +/- 6 ml/m2, follow-up 91 +/- 6 ml/m2), and improvement in left ventricular ejection fraction in some patients.

International mexiletine and placebo antiarrhythmic coronary trial: I. Report on arrhythmia and other findings. Impact Research Group

The antiarrhythmic effects of the sustained release form of mexiletine (Mexitil-Perlongets) were evaluated in a double-blind placebo trial in 630 patients with recent documented myocardial infarction. The primary response variable was based on central reading of 24 hour ambulatory electrocardiographic recordings and was defined as the occurrence of 30 or more single premature ventricular complexes in any two consecutive 30 minute blocks or one or more runs of two or more premature ventricular complexes in the entire 24 hour electrocardiographic recording. Large differences, regarded as statistically significant, between the mexiletine and placebo groups were noted in that end point at months 1 and 4, but only trends were observed at month 12. These differences were observed even though the serum mexiletine levels obtained in this study were generally lower than those observed in studies that have used the regular form of the drug. There were more deaths in the mexiletine group (7.6%) than in the placebo group (4.8%); the difference was not statistically significant. The incidence of coronary events was similar in both groups. Previously recognized side effects, particularly tremor and gastrointestinal problems, were more frequent in the mexiletine group than in the placebo group.

Rationale of therapy in the patient with acute myocardial infarction and life-threatening arrhythmias: a focus on bretylium

Experimental evidence suggests a number of pathologic and electrophysiologic mechanisms that may help initiate ventricular arrhythmias accompanying myocardial ischemia and infarction. Early and late phase events are associated with reentry or an enhancement of focal mechanisms, or both. These can initiate ventricular tachycardia (VT) or ventricular fibrillation (VF), or both. The presence of distinct mechanisms that may initiate and maintain life-threatening dysrhythmias early in myocardial ischemia suggest different pharmacologic approaches for their prevention or suppression. Another consideration concerns patients subjected to coronary artery angioplasty or thrombolytic therapy and the development of arrhythmias associated with reperfusion of the once ischemic myocardium. The electrophysiologic mechanisms associated with reperfusion arrhythmias are unknown, and little is known about appropriate therapy for each episode of cardiac dysrhythmia. Ventricular extrasystoles or VT usually precedes VF. These premonitory arrhythmias are poor criteria for the institution of antiarrhythmic drug therapy, because VF develops within 1 to 10 minutes after the appearance of the rhythmic disturbances. Some authorities suggest that all patients with acute myocardial infarction should receive prophylactic antiarrhythmic therapy, because warning arrhythmias either do not occur at all or provide insufficient time to intervene pharmacologically. Many of the new class I antiarrhythmic agents effectively reduce the frequency of premature ventricular depolarizations, but lack specific antifibrillatory activity. However, the recent introduction of bretylium into clinical cardiology opens a new approach to preventing life-threatening ventricular dysrhythmias. Along with other members of class III, bretylium exerts different cardiac electrophysiologic effects than do the other 3 classes of drugs.(ABSTRACT TRUNCATED AT 250 WORDS)

Effect of long-term prophylactic treatment on survival after myocardial infarction

Survivors of the acute phase of a myocardial infarction still have an increased risk of dying, primarily due to causes directly attributable to their coronary heart disease. This review of randomized clinical trials of various interventions with the potential to prolong life in these patients is an attempt to answer a vitally important question. What, if anything, can be done to improve the long-term prognosis in patients who have survived the initial one or two weeks after suffering an acute myocardial infarction? Seven classes of intervention are considered: anticoagulants, platelet-active drugs, lipid-lowering regimens, antiarrhythmic agents, physical exercise, calcium antagonists and beta-blockers. So far only beta-blockers have been shown to have a favorable effect on long-term survival. Many of the trials reviewed had design limitations; in particular, the sample size was often too small for the results to be conclusive.