Beta-adrenergic blockade for survivors of acute myocardial infarction

Cardioprotective and antiarrhythmic effects of beta-blockers, propranolol, bisoprolol, and nipradilol in a canine model of regional ischemia

Cardioprotective and antiarrhythmic effects of three beta-blockers with different pharmacological properties were investigated in 33 anesthetized dogs with a 2-h coronary occlusion. Dogs were divided into 4 groups and received physiological saline or one of the following drugs using a 10-min infusion at 25 min before the occlusion: saline or control (n = 12), propranolol (0.3 mg/kg, n = 7), bisoprolol (0.05 mg/kg, n = 7), and nipradilol (0.2 mg/kg, n = 7) groups. Blood pressure did not significantly differ among the 4 experimental groups throughout the entire observation period. On the contrary, the postocclusion change (fall) in heart rate from the preocclusion value was significantly (P less than 0.05-0.01) greater in the drug-treated groups than in the control group. Each of the beta-blockers effectively prevented the development of ventricular arrhythmias associated with the 2-h coronary occlusion. In terms of assessing a cardioprotective effect, the respiratory control index and rate of oxygen consumption in State III in mitochondria, and lysosomal enzyme activities (N-acetyl-beta-glucosaminidase or beta-glucuronidase) in myocardial tissues, all prepared from both ischemic and non-ischemic areas, were measured using the respective, established methods. The 2-h coronary occlusion induced a mitochondrial dysfunction and leakage of lysosomal enzymes in the control group, whereas each beta-blocker significantly (P less than 0.05-0.01) protected mitochondria against ischemia and prevented the lysosomal enzyme leakage. The results indicate that the antiarrhythmic effects of beta-blockers on ischemic myocardium are, at least in part, due to their cardioprotective action, and these effects appear to be unrelated to the ancillary pharmacological properties of these drugs.

Long-term propranolol administration alters myocyte and ventricular geometry in rat hearts with and without infarction

To determine the effects of long-term beta-adrenergic receptor blockade on adult rats with myocardial infarction, we studied 24 female Sprague-Dawley rats with myocardial infarction induced at 20-22 weeks of age. Two days after surgery, the animals were randomized to receive either propranolol (750 mg/l) in their drinking water or water alone for 5 weeks. Plastic, embedded, longitudinal and cross sections of septum (1 micron thick) were prepared for morphometric measurements. In untreated rats, infarction was followed by myocardial hypertrophy, as shown by significant increases in septal area (23%), myocyte length (19%), cross-sectional area (20%), and volume (43%) (p less than or equal to 0.05). In rats with and without infarction, beta-blockade resulted in decreased myocyte dimensions and increased left ventricular cavity dimensions. Propranolol had special effects in rats with infarction, resulting in significant blunting of increased cross-sectional area (15% less, p = 0.04) and a greater increase in left ventricular cavity dimensions (38% more, p = 0.04). Thus, propranolol blunts myocardial hypertrophy and increases left ventricular cavity dimensions in rats with myocardial infarction.

Beta-blocker therapy in patients with ventricular tachyarrhythmias in the setting of left ventricular dysfunction

Although several studies suggest beta blockers (BB) are effective in suppressing ventricular arrhythmias, less is known about their role in the treatment of patients with ventricular tachyarrhythmias associated with impaired left ventricular function. To assess the tolerance and efficacy of these agents, 32 patients presenting with either ventricular fibrillation (18) or sustained ventricular tachycardia (14) were studied during BB therapy. Left ventricular dysfunction (mean ejection fraction 29%) was present as a consequence of coronary artery disease (26) or cardiomyopathy (6). Baseline arrhythmia assessment revealed recurrent ventricular tachycardia in all patients. Antiarrhythmic drug therapy including BB was guided by programmed stimulation (10), exercise testing (8), ambulatory monitoring (12), or was given empirically (2). Beta blockers were well tolerated, as measured by exercise duration, which improved significantly, and by long-term maintenance, which continued in 23 of 32 (72%) patients. Over a mean follow-up of 668 days, patients treated with BB had a relatively low incidence of both sudden (3%) and nonsudden (9%) death. Thus, BB can be effective and well tolerated adjunct therapy in patients with a history of ventricular tachyarrhythmias in the setting of impaired left ventricular function.

The effect of timolol given five minutes after coronary occlusion on plasma catecholamines

The reported study determined whether timolol would afford a protective effect by preventing the coronary occlusion-induced arrhythmias associated with the increase in plasma norepinephrine (NE) and epinephrine (E). Ten anesthetized cats received saline or timolol (5 mg/kg, IV) five minutes after coronary occlusion of the left anterior descending coronary artery 10 to 14 mm below its origin. Coronary occlusion produced arrhythmia in three of the cats that received saline and in four of the cats that received timolol. Three of the saline-treated cats died in cardiogenic shock; two were sacrificed six hours postocclusion. Four of the timolol-treated cats died in congestive heart failure postcoronary occlusion. There was a gradual increase in NE (P greater than .05) and E (P less than .05) in both groups after coronary occlusion. Death produced a significant increase in NE and E levels. Timolol did not modify the occurrence of arrhythmias and the associated increase in plasma NE and E that developed after coronary occlusion and at death.

Ultra-short-acting beta-adrenergic blockers

The ultra-short-acting beta-adrenergic blockers are parenteral agents that can be rapidly titrated in clinical situations where immediate beta-adrenergic blockade is warranted. The effects of those drugs rapidly dissipate after termination of treatment, providing an important safety feature. Esmolol, the prototype drug of this class, is approved for treatment of supraventricular tachyarrhythmias but also has potential use in treatment of patients with perioperative hypertension and acute myocardial ischemia.

Platelets and antiplatelet therapy in ischemic heart disease

Blood platelets have been shown to play an important role not only in thrombosis, but also in the pathogenesis of coronary artery disease and its complications. Drugs that affect platelets have been shown to reduce mortality in survivors of acute myocardial infarction, to reduce the risk of myocardial infarction in patients with unstable angina, and to preserve the potency of saphenous venous grafts used to bypass obstructed coronary arteries. The drugs may also play a role in the primary prevention of arteriosclerosis and in preventing thrombotic complications following coronary angioplasty.

Beta-adrenergic blockers

beta-Adrenergic blocking drugs have been available for several years to treat ischemic heart disease and other cardiovascular and noncardiovascular disorders. There are multiple drugs in this class with various pharmacodynamic and pharmacokinetic properties that may be important in specific clinical situations and in avoiding certain adverse reactions. These drugs have been shown to be efficacious in relieving anginal symptoms and prolonging exercise tolerance, in reducing high blood pressure, for treating various arrhythmias, in therapy of hypertrophic cardiomyopathy, and for prolonging life in many survivors of acute myocardial infarction.

Multiple risk factors for coronary artery disease: behavioral factors in preventive cardiology

The prevention of ischemic heart disease requires intervention on the natural history of coronary artery disease (CAD). Because a variety of so-called risk factors influence that natural history, it is logical to consider modification of these risk factors as a way to prevent CAD. Although this approach is effective in both the primary and secondary prevention of CAD, this presentation will focus on behavioral intervention on multiple risk factors in the secondary prevention of CAD (i.e., after the initial cardiac event). A number of studies have suggested that lifestyle modification plays an important role in preventing CAD recurrence or death. Risk factors that require this modification of human behavior include: low-density lipoprotein cholesterol, high-density lipoprotein cholesterol, cigarette smoking, obesity, hypertension, physical activity and, although controversial, coronary prone personality. The assessment of these multiple factors can be performed in most acute care settings. The intervention on the factors requires a structured approach to the patient, taking advantage of the heightened awareness and concern at the time of a cardiac event. Often, several behaviors require modification simultaneously and other disciplines (behavioral medicine, nutrition, exercise physiology) are often useful when integrated into a single treatment plan. Involvement of the patient's social support network is essential. The effectiveness of the modification of each risk factor is assessed, as a means of recognizing behavior change as a way to prevent recurrence of the disease.

Prevention of recurrent myocardial infarction and sudden death with aspirin therapy

In October 1985, the Food and Drug Administration approved a new indication of aspirin for the secondary prevention of recurrent myocardial infarction (MI) and death in patients with MI or unstable angina. Clinical trials have demonstrated the efficacy of this drug, especially when treatment is begun soon after the initial event. The antiplatelet actions of aspirin seem to be the most plausible explanation for its efficacy in reducing mortality and the rate of reinfarction. A single daily 325-mg tablet is effective and produces side-effect incidences of only zero to two percent above those produced by placebo. This article assesses the current state of knowledge regarding the value of aspirin therapy in survivors of acute MI and the implications for clinical practice.

Beta blockers in combination with class I antiarrhythmic agents

The hemodynamic and antiarrhythmic interactions between nadolol and a commonly used class I antiarrhythmic agent, quinidine or procainamide, were evaluated in 18 patients with ventricular arrhythmias in a double-blind, parallel study. Patients qualified for entry into the study if their ventricular arrhythmias remained poorly controlled (greater than or equal to 10 ventricular premature complexes/hr) with the class I agent alone and they had a left ventricular ejection fraction greater than 30%. Patients received their usual therapeutic doses of quinidine or procainamide throughout the study, which consisted of 3 treatment periods; a 2-week placebo treatment period, a 2-week open-label oral nadolol dose titration period, during which the dosages of nadolol were gradually increased from 40 mg daily to a maximum tolerated dose up to 120 mg daily, and a 4-week randomized, parallel comparison period during which patients were treated with either a class I agent alone or a combination of a class I agent and nadolol. Left ventricular ejection fractions by radionuclide ventriculography and 24-hour ambulatory electrocardiographic (Holter) recordings were obtained at the end of each treatment period. A positive treatment response was defined as greater than or equal to 75% reduction in ventricular premature complex frequency. During the dose titration phase, combination therapy with nadolol (mean dose 94 mg daily) and class I agents produced a mean decrease in ventricular premature complexes of 79% (p less than 0.01), and a mean decrease in ventricular couplets of 95% (p less than 0.01). A positive response was observed in 57% of patients treated with nadolol plus a class I agent.(ABSTRACT TRUNCATED AT 250 WORDS)

Clinical differences between beta-adrenergic blocking agents: implications for therapeutic substitution

The beta blockers exhibit clinically significant differences in beta-receptor selectivity, intrinsic sympathomimetic activity, and alpha-adrenergic blocking activity. These agents also show important differences in their pharmacokinetic profiles, including gastrointestinal absorption, first-pass hepatic metabolism, lipid solubility, protein binding, hepatic biotransformation, pharmacologic activity of metabolites, and renal clearance of unchanged drug and metabolites. These many differences determine the appropriateness of administering a given beta blocker in a given clinical situation. The selection of beta blockers must also take into account concurrent therapy with other agents. Concurrent administration of beta blockers with drugs that alter gastric, hepatic, or renal function may affect blood levels, duration of action, or efficacy of beta-blocker action. The beta blockers vary in the extent to which their action is altered when they are given with other agents, and therapeutic substitution may produce unwanted side effects and toxicity. Elderly patients should be carefully monitored following interchange among beta blockers, since the probability of drug interaction, impact of adverse effects, unpredictability of response, and physiologic variability of renal and liver function is greater than for younger individuals. Therapeutic substitution among beta blockers in patients already stabilized on a given agent will require careful monitoring. Retitration with the new beta blocker will be required in many cases to assure therapeutic equivalence. Beta blockers are currently used for over 20 medical conditions. There is wide variation in the strength of the clinical evidence supporting the use and efficacy of specific beta blockers for specific conditions.(ABSTRACT TRUNCATED AT 250 WORDS)

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.

Results of sympathetic denervation in the canine heart: supersensitivity that may be arrhythmogenic

Latex-induced transmural myocardial infarction or epicardial application of phenol interrupts sympathetic fibers innervating myocardium apical to the infarction or to the phenol-painted area. These denervated regions subsequently show supersensitive shortening of effective refractory period (ERP) in response to the infusion of norepinephrine (denervation supersensitivity). The purpose of this study was to test the hypothesis that such denervation supersensitivity is arrhythmogenic. Ventricular arrhythmias were elicited by programmed ventricular stimulation (PVS) during a control period, during bilateral stimulation of the ansae subclaviae (4 msec pulses, 4 Hz and 3 mA), and during the infusion of norepinephrine (0.5 microgram/kg/min). Study groups consisted of 14 sham-operated dogs, 16 dogs with phenol painted over a diagonal branch, 13 dogs with latex embolization of a diagonal branch that resulted in transmural myocardial infarction, 14 dogs with a one-stage ligation of a diagonal branch producing nontransmural myocardial infarction, and 12 dogs undergoing both phenol painting and one-stage ligation of a diagonal branch. Four to 22 days after the first operation, PVS was performed in anesthetized, open-chest dogs after neural decentralization of the heart. Dogs with phenol painting on the epicardium and dogs in which latex was injected into a diagonal branch showed supersensitive shortening of ERP to infused norepinephrine at apical sites. PVS resulted in ventricular fibrillation more often during stimulation of the ansae subclaviae (p less than .001) and infusion of norepinephrine (p less than .001) than during the control state in dogs treated with phenol alone. The incidence of ventricular fibrillation was highest in dogs with ligation-induced infarction that received phenol compared with all other groups during control (p less than .001), stimulation of the ansae subclaviae (p less than .002), and the infusion of norepinephrine (p less than .01). Propranolol (0.5 mg/kg or 10 mg iv at maximum) attenuated supersensitive shortening of ERP and decreased the incidence of induction of ventricular fibrillation.(ABSTRACT TRUNCATED AT 400 WORDS)

Platelet function in patients admitted with a diagnosis of myocardial infarction

Platelet function and thromboxane A2 release were measured in 71 patients admitted to a coronary care unit with a provisional diagnosis of acute myocardial infarction (AMI). All measurements were carried out within twenty-four hours of admission. Of these, 35 patients had the diagnosis of AMI confirmed. The remainder (n = 36), who did not have AMI (NMI), were divided into two groups: those (n = 18) with an unequivocal history of previous vascular disease and those without vascular disease (n = 18). Platelet aggregation and thromboxane A2 (TXA2) release were significantly increased in the AMI group when compared with those in the NMI without vascular disease group or a healthy control group with similar age and sex distribution. Aggregation and TXA2 release in the NMI patients with vascular disease were greater than those in controls and did not differ significantly from those in the AMI group. Patients in the AMI or NMI with vascular disease groups who were taking beta-blockers or calcium channel antagonists at the time of admission showed significantly less platelet aggregation than those who were not taking these drugs. Heparin, added in vitro at therapeutic concentrations, induced significantly more aggregation in patients in the AMI and NMI with vascular disease groups than in the NMI without vascular disease group. We conclude that: platelets obtained from patients with AMI are hyperaggregable and release more TXA2; platelets from patients with significant vascular disease are hyperaggregable, even in the absence of AMI, although they are not as hyperaggregable as those from AMI; treatment with nifedipine and beta-blockers protects these patients from platelet hyperaggregability; heparin induces significant aggregation of platelets from patients with AMI and NMI with vascular disease. These observations are of importance in considering the pathogenesis and treatment of AMI and ischemic heart disease.

Beta-adrenergic receptor properties of canine myocardium: effects of chronic myocardial infarction

To determine the effects of chronic myocardial infarction on beta-adrenergic properties of canine myocardium, the hearts of nine mongrel dogs were studied 3 weeks after acute myocardial infarction. Infarction was produced by ligating the left anterior descending coronary artery in five dogs and the circumflex artery in four dogs. The heart was divided into normal and infarct zones (either anterior or posterior, depending on the vessel ligated) and marginal zones (septal and lateral), each zone being subdivided into epicardial and endocardial portions. Myocardial blood flow (microsphere technique) was markedly reduced in the infarct zone. In eight endocardial infarct samples after left anterior descending ligation, the maximal number (+/- SD) of binding sites assessed by 125I-iodocyanopindolol was 3.9 +/- 1.9 pmol/mg deoxyribonucleic acid (DNA) and was reduced from normal endocardial values (9.7 +/- 9.4 pmol/mg DNA, p less than 0.05). The dissociation constant (Kd), which is a measure of the affinity of the iodinated antagonist for the receptor, did not differ (304 +/- 222 versus 338 +/- 219 pM, p = NS). In the epicardium, the maximal number of beta-adrenergic receptors was also reduced (p less than 0.05), without a change in Kd. In the lateral and septal zones neither the maximal number of binding sites nor Kd values differed from those of normal endocardium. In nine endocardial infarct zones, (-)-isoproterenol-stimulated adenylate cyclase activity was reduced compared with control (34,870 +/- 29,430 versus 88,660 +/- 63,640 pmol/mg DNA/30 minutes, p less than 0.01), but the ratio of (-)-isoproterenol-stimulated to maximal (sodium fluoride-stimulated) adenylate cyclase activity was unchanged between normal and infarct zones.(ABSTRACT TRUNCATED AT 250 WORDS)

Long-term use of probucol in the multifactorial primary prevention of vascular disease

Over 1,200 middle-aged men with no apparent vascular disease participated in a 5-year multifactorial primary prevention trial, in which 612 received dietetic, hygienic and--when indicated--pharmacologic treatment for the following risk factors: hyperlipidemia, hypertension, smoking, obesity and abnormal glucose tolerance. Pharmacologic therapy included hypolipidemic agents (mainly probucol and clofibrate) and antihypertensive drugs (mainly diuretics and beta blockers). At the end of the 5 years, results in these men were compared with findings in 610 high risk and 593 low risk control subjects, none of whom had received treatment. Although intervention decreased the mean risk factor status of the treated men by 33%, their 5-year coronary incidence exceeded that of the high risk control subjects (3.1% vs 1.5%). Stroke incidence, however, was markedly reduced in the treated subjects (0% vs 1.3%). Multivariate analysis showed that the coronary events occurred in patients taking beta blockers or clofibrate, while few occurred in those receiving probucol or the diuretics. The decrease in mean serum cholesterol was 15% in men receiving only probucol, and ranged from 0% to 13% in those receiving different drug combinations, including clofibrate plus probucol (11%). Probucol also markedly decreased high density lipoprotein cholesterol levels, especially when combined with clofibrate. It is possible that adverse drug effects offset the probable benefit of an improved risk profile in the treated men, thereby explaining the greater than expected occurrence of cardiac events in this group. The probucol data, however, suggest that it may not be harmful to lower the high density lipoprotein cholesterol level when there is a significant decrease in total cholesterol as well.

Effect of beta blockade on ventricular fibrillation- and ventricular tachycardia-induced circulatory arrest in acute myocardial infarction

The risk of developing circulatory arrest secondary to ventricular fibrillation or tachycardia in acute myocardial infarction (AMI) is greatly increased in patients with hypokalemia, whether diuretic induced or not. In a retrospective study of 5,877 infarctions during an 8-year period, hypokalemia was more common (22.5%) in diuretic-treated AMI patients than in those not treated with diuretics (12.9%). Thus, hypokalemia should be avoided in diuretic-treated patients with increased risk of myocardial infarction. Circulatory arrest occurred in 13% of hypokalemic patients treated with nonselective beta blockers on admission compared with 26% in those treated with selective beta blockers. No difference was found in normokalemic patients. The mean serum potassium value was 4.07 mM/liter in the patients treated with nonselective beta blockers compared with 4.0 and 4.01 in those treated with selective and no beta blockade, respectively. In a separate study, adrenaline infusion in healthy volunteers produced a decrease not only in serum potassium but also in serum magnesium, although the latter occurred later. Pretreatment with verapamil exaggerated the decrease in serum potassium. When starting beta-blocker treatment in patients at risk of developing AMI, consideration should be given to commencing with a nonselective instead of a selective beta blocker.

Calcium-channel blockers for combined angina pectoris and systemic hypertension

Calcium-channel blockers have been successfully used in the treatment of angina of effort and systemic hypertension. Many patients present with concomitant angina pectoris and hypertension. Controlled clinical trials demonstrate that the calcium-channel blockers are safe and effective as monotherapy in the treatment of these patients, and that their use compares favorably with that of propranolol. The effectiveness of these agents in hypertension appears to be primarily due to their ability to induce systemic vasodilation. Calcium-channel blockers have several therapeutic effects in angina pectoris. Beneficial actions on the major determinants of oxygen consumption, i.e. heart rate, blood pressure and contractility, are generally seen. The potent coronary vasodilating actions of these agents allow for increased coronary blood flow. Improvements in ventricular compliance, regression of left ventricular hypertrophy and cardioprotection appear to be additional effects of the calcium-channel blockers; their contribution to the drugs' overall therapeutic efficacy is presently being evaluated. Calcium-channel blockers are a welcome addition to drug regimens available for the management of patients with coexisting angina pectoris and hypertension.

Effect of propranolol in patients with myocardial infarction and ventricular arrhythmia

The Beta-Blocker Heart Attack Trial was a placebo-controlled, randomized, double-blind clinical trial of the long-term administration of propranolol hydrochloride to patients who had had at least one myocardial infarction. Among 3,837 patients followed up for an average of 25 months, 3,290 (85.7%) had 24 hour ambulatory electrocardiograms performed at the baseline examination. Four classifications of arrhythmia were examined. One of these, the presence of complex ventricular arrhythmias (at least 10 ventricular premature beats/h, or at least one pair or run of ventricular premature beats or multiform ventricular premature beats) was the subgroup of major interest. Regardless of the classification, the presence of arrhythmia identifies a group of patients with a higher risk of total mortality, coronary heart disease mortality, sudden cardiac death and instantaneous cardiac death. The a priori subgroup hypothesis that sudden death would be preferentially reduced by propranolol in patients with complex ventricular arrhythmias was not supported. The relative benefit of propranolol in reducing sudden death for this subgroup was 28 versus 16% for the subgroup without ventricular arrhythmia (relative risk of 0.72 versus 0.84, a nonsignificant relative difference of 14%). There were similar findings for two of the three other classifications of arrhythmia and for the other response variables. Although propranolol does not appear to be of special relative benefit in patients with ventricular arrhythmia, the presence of the arrhythmia does identify a high-risk group. The mechanism by which propranolol reduces mortality is still unclear, but is probably not solely an antiarrhythmic one.

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.

Six-year follow-up of the Norwegian Multicenter Study on Timolol after Acute Myocardial Infarction

The original Norwegian Multicenter Study on Timolol after Myocardial Infarction was a double-blind, randomized study comparing the effect of timolol with that of placebo for up to 33 months after acute myocardial infarction. The initial results showed that the cumulated mortality rate was 39.4 per cent lower among 945 patients randomly assigned to timolol treatment than among 939 patients randomly assigned to placebo (P = 0.0003). After the end of the double-blind period the majority of participating patients in the timolol group continued to receive beta-adrenergic blockade, whereas the majority of placebo-treated patients continued without such blockade. During an extended follow-up of participating patients up to 72 months after randomization, the mortality curves of the two groups continued to rise in parallel. Cumulated mortality rates were 32.3 per cent in the placebo group and 26.4 per cent in the timolol group (P = 0.0028). We conclude that the previously observed early beneficial effect of beta-adrenergic blocking therapy is maintained for at least six years after infarction.

The place of coronary artery bypass surgery: an appraisal

The enthusiasm for performing coronary artery bypass graft (CABG) surgery in Australia is increasing. The results of a number of careful trials which have compared surgical with medical treatment have now appeared. While there is agreement on both the increased survival provided by CABG surgery in those with left main coronary artery stenosis and the relief of symptoms in patients in whom medical therapy has failed to control severe angina, there is debate about the value of surgery in other types of disease. With improvements in medical therapy, the most recent trials have failed to show a significant overall survival benefit from surgery, although it is generally considered that surgery can relieve angina and that, in at least some groups of persons with stenosis of all three main coronary vessels (triple-vessel disease), surgery may prolong life. Alternative methods of prolonging survival among people with ischaemic heart disease include the reduction of risk factors (such as hypertension, raised blood cholesterol levels and cigarette smoking), as well as treating patients with beta-blocking agents after a myocardial infarction. We suggest it is likely that a combination of these approaches could be more effective in terms of lives saved than is CABG and may be less expensive. The current expansion of CABG surgery in Australia should be viewed in this light.

Prediction of sudden death and spontaneous ventricular tachycardia in survivors of complicated myocardial infarction: value of the response to programmed stimulation using a maximum of three ventricular extrastimuli

The prognostic significance of ventricular arrhythmias induced by programmed electrical stimulation was evaluated in 50 survivors of acute myocardial infarction complicated by a major new conduction disturbance (38 patients), congestive heart failure (33 patients) or sustained ventricular tachyarrhythmias (22 patients), alone or in combination. Programmed stimulation was performed in patients in stable condition 7 to 36 days (mean 16) after infarction using one to three extrastimuli at four times diastolic threshold at a maximum of two right ventricular sites. Two groups were identified by the response to programmed stimulation: 17 patients with sustained (greater than 15 seconds) or nonsustained (greater than 7 beats but less than or equal to 15 seconds) ventricular tachycardia (group I), and 33 patients with 0 to 7 intraventricular reentrant complexes in response to maximal stimulation efforts (group II). Group I patients had a higher incidence of anterior infarction than that of patients in group II (71 versus 42%), had lower left ventricular ejection fraction (mean 0.35 versus 0.48) and were more often treated with antiarrhythmic drugs (47 versus 18%, p less than 0.05). There were no significant differences between groups in the occurrence of congestive failure, new conduction disorders or sustained ventricular arrhythmias with infarction, or in the proportions treated with a beta-receptor blocking agent, coronary bypass grafting or a permanent pacemaker. Total cardiac mortality was 24% during a mean follow-up period of 23 months and did not differ between groups; however, the response to programmed stimulation identified a group at high risk of late sudden death or spontaneous ventricular tachycardia: 7 (41%) of 17 group I patients compared with 0 of 33 group II patients (p less than 0.001). The induction of sustained or nonsustained ventricular tachycardia identified all patients who died suddenly or had spontaneous tachycardia (sensitivity 100%), but triple extrastimuli were required to induce prognostically significant arrhythmias in five of these seven patients; the specificity of this protocol was only 57%. When the clinical variables of the group were evaluated individually, the response to programmed stimulation had a stronger association with occurrence of late sudden death than did any other factor (Fisher's exact test, p less than 0.001); however, a type II error could not be excluded.(ABSTRACT TRUNCATED AT 400 WORDS)

Considerations in the long-term management of survivors of cardiac arrest

The heterogeneity of resuscitated patients at risk of recurrent cardiac arrest serves to make their management difficult and complex. It is logical that therapy should be tailored to each patient and certainly to the mechanism whereby sudden cardiac death occurred. It is important, also, to recognize that not all resuscitated victims are at high risk for recurrence and that aggressive interventions are not necessarily mandatory. In the patient with cardiac arrest related to transient myocardial ischemia, a direct approach toward relieving ischemia seems appropriate. Antiarrhythmic agents may have a role in the treatment of some patients, but to this date the efficacy of such therapy is speculative, at best. The development and testing of agents that have "antifibrillatory" properties seems a logical approach at this time. Clearly, efforts to lessen the mortality of patients who have been resuscitated from out-of-hospital cardiac arrest are important, not only for the particular patients themselves, but also in an effort to develop rational, prophylactic interventions for the large numbers of patients with coronary heart disease who are at risk for the development of sudden cardiac death.

Mechanisms contributing to precipitation of unstable angina and acute myocardial infarction: implications regarding therapy

Clinical and autopsy studies indicate that most patients who present with unstable angina or an acute myocardial infarction (AMI) have significant underlying coronary atherosclerosis. This review discusses 4 mechanisms that may contribute to the precipitation of these acute ischemic clinical syndromes: progression of atherosclerosis, acute coronary thrombosis, coronary artery spasm, and platelet aggregation. Numerous clinical trials using thrombolytic agents early during AMI have shown the incidence of thrombosis to be at least 60%. Other studies suggest that platelet aggregation frequently contributes to the evolution of AMI from unstable angina and that spasm may occasionally play a similar role. The therapeutic implications of these mechanisms are also considered in light of their potential to restore coronary artery blood flow (vs conventional methods thought mainly to reduce myocardial oxygen demand) and thereby limit the infarct process. The role of vasodilators, thrombolytic agents, antiplatelet drugs and beta-adrenergic blocking drugs are discussed. Finally, therapeutic guidelines for the treatment of acutely ill patients are constructed that emphasize the need for a comprehensive yet time-efficient treatment strategy that uses nitrates, calcium channel-blocking drugs, streptokinase, heparin, aspirin and, in selected patients in an unstable condition, emergency percutaneous transluminal coronary angioplasty and coronary artery bypass grafting.