Evolution of infarct size during the early use of nifedipine in patients with acute myocardial infarction: the Norwegian Nifedipine Multicenter Trial

Functional arrays of human pluripotent stem cell-derived cardiac microtissues

To accelerate the cardiac drug discovery pipeline, we set out to develop a platform that would be capable of quantifying tissue-level functions such as contractile force and be amenable to standard multiwell-plate manipulations. We report a 96-well-based array of 3D human pluripotent stem cell (hPSC)-derived cardiac microtissues - termed Cardiac MicroRings (CaMiRi) - in custom 3D-print-molded multiwell plates capable of contractile force measurement. Within each well, two elastomeric microcantilevers are situated above a circumferential ramp. The wells are seeded with cell-laden collagen, which, in response to the gradual slope of the circumferential ramp, self-organizes around tip-gated microcantilevers to form contracting CaMiRi. The contractile force exerted by the CaMiRi is measured and calculated using the deflection of the cantilevers. Platform responses were robust and comparable across wells, and we used it to determine an optimal tissue formulation. We validated the contractile force response of CaMiRi using selected cardiotropic compounds with known effects. Additionally, we developed automated protocols for CaMiRi seeding, image acquisition, and analysis to enable the measurement of contractile force with increased throughput. The unique tissue fabrication properties of the platform, and the consequent effects on tissue function, were demonstrated upon adding hPSC-derived epicardial cells to the system. This platform represents an open-source contractile force screening system useful for drug screening and tissue engineering applications.

The calcium-channel blocker controversy: historical perspective and important lessons for future pharmacotherapies. An international society of pharmacoepidemiology 'hot topic'

Reports of adverse events in association with calcium-channel blockers led to heated controversy over the safety and efficacy of these drugs, as well as to panic among the general public. At the 1998 International Conference of Pharmacoepidemiology, four experts were asked to summarize, and draw lessons from, the controversy's development. We conducted our own review in order to provide a broader historical perspective on the subject and to present the discussants' views within the framework of additional published opinions. Several years after the controversy's onset, many uncertainties still remain about the merits of CCBs. Yet the media scare generated by a few studies might have been prevented had investigators placed greater emphasis, particularly in their reports to the media, on the limitations of their observational and meta-analytic designs. These studies, however, did call attention to the persistent use of CCBs for off-label indications, and the imperative to improve clinician prescribing practices. Moreover, they showed the pitfalls of reliance on surrogate endpoints, stressing the need for data on major clinical outcomes-with funding a responsibility of the pharmaceutical industry-before approving drugs destined for widespread, long-term use. Attention to these lessons will do us well as we evaluate emerging pharmacotherapies. Copyright (c) 2000 John Wiley & Sons, Ltd.

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.

Pharmacological profile of survivors of acute myocardial infarction at Turkish academic hospitals

AIM

The purpose of this study was to document treatment profiles in 850 patients surviving acute myocardial infarction at 17 academic hospitals in Turkey.

METHODS AND RESULTS

Pharmacological management data of acute myocardial infarction survivors were collected and divided into three categories: drugs which patients received before hospitalization, during the hospitalization, and at hospital discharge. Data regarding medical history, complications during hospitalization, MI extent (Q wave or non-Q wave), infarct location and diagnostic and revascularization procedures were also recorded. This study is based on the 850 patients who met the diagnostic criteria for initial acute MI in the period examined. Among 850 patients with myocardial infarction enrolled 408 (48%) received thrombolytic therapy. The median time interval from symptom onset to initiation of thrombolytic therapy was 196 min. The most commonly used thrombolytic agent was streptokinase (93%). Thrombolytic recipients were younger, and presented sooner after onset of symptoms. Among patients receiving thrombolytic therapy, concomitant pharmacotherapy included aspirin (95%), intravenous heparin (93%), intravenous nitroglycerin (91%), oral beta-blockers (44%), calcium channel antagonists (13%), and angiotensin converting enzyme inhibitors (41%). The lipid lowering therapy was only used in 4% of all patients, and was given to 18% of patients with hyperlipidemia.

CONCLUSION

Current usage rates of thrombolytic therapy in Turkey are lower than expected, but when compared with previous reports it increased. Although adjunctive treatment with intravenous heparin and intravenous nitroglycerin is usually used, beta-blockers appear to be underused and calcium channel blockers appear to be overused. The lipid reducing therapies were infrequently prescribed.

Unstable angina and non-Q wave myocardial infarction: does the clinical diagnosis have therapeutic implications?

OBJECTIVES

The goal of this review is to reevaluate the unstable coronary syndromes in the setting of new therapies and biochemical markers.

BACKGROUND

Patients with acute coronary syndromes comprise a large subset of many cardiology practices. Patients with unstable angina (UA) and non-Q wave myocardial infarction (NQMI) may sustain a small amount of myocardial loss but have significant amounts of viable, yet ischemic, myocardium, placing them at high risk for future cardiac events. In the past, enzyme differentiation of NQMI from UA was considered important to assess prognosis and direct therapy.

METHODS

Manuscripts published in peer-reviewed journals over the past three decades were reviewed and selected for this review. Recent abstracts were also considered and cited where appropriate.

RESULTS

In the late 1990's, although UA and NQMI remain parts of a spectrum, it is apparent that the distinction between these two entities is no longer sufficient to identify high risk patients; rather, specific electrocardiographic changes, aspects of the clinical history, newer biochemical markers, and angiographic findings help to better distinguish higher risk individuals from a large patient population with unstable coronary syndromes and these factors usually determine therapy.

CONCLUSIONS

Based on these results, it is likely that newer therapies such as glycoprotein IIb/IIIa receptor antagonists, low molecular weight heparins, and coronary stents will be directed toward these high risk patients.

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

OBJECTIVES

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

BACKGROUND

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

METHODS

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

RESULTS

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

CONCLUSIONS

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

CP-060S, a novel cardioprotective drug, limits myocardial infarct size in anesthetized dogs

The myocardial infarct size (IS)-limiting effect of CP-060S, a novel cardioprotective drug that prevents Na+-, Ca2+-overload and has Ca2+ channel-blocking activity, was compared with that of diltiazem, a pure Ca2+ antagonist, to determine whether the prevention of Na+-, Ca2+-overload contributes to this IS-limiting effect. Dogs were subjected to 90 min of left circumflex coronary artery (LCx) occlusion followed by 5 h of reperfusion. Either CP-060S (300 microg/kg) or diltiazem (600 microg/kg) was administered intravenously 20 min before the occlusion. CP-060S significantly limited IS compared with that of vehicle (percentage of the area at risk: vehicle, 50.64 +/- 6.08%; CP-060S, 21.13 +/- 3.75%; p < 0.01 vs. vehicle). Although diltiazem exerted a significant decrease in rate-pressure product (RPP; an index of myocardial oxygen consumption) during occlusion equal to that of CP-060S, diltiazem did not significantly reduce IS (33.90 +/- 4.30%). Regional myocardial blood flow (RBF) was not significantly different between any of the groups. Therefore the IS-limiting effect of CP-060S cannot be explained in terms of changes in RPP or RBF. Thus the IS limitation induced by CP-060S is probably the consequence of a direct cardioprotective effect on myocytes. The prevention of Na+-, Ca2+-overload may be the primary reason for this IS-limiting effect.

Interrelationship between cellular calcium homeostasis and free radical generation in myocardial reperfusion injury

This review describes the interrelationship between two important biological factors, intracellular calcium overloading and oxygen-derived free radicals, which play a crucial role in the pathogenesis of myocardial ischemic reperfusion injury. Free radicals are generated during the reperfusion of ischemic myocardium, and polyunsaturated fatty acids in the membrane phospholipids are the likely targets of the free radical attack. On the other hand, activation of phospholipases can provoke the breakdown of membrane phospholipids which results in the activation of arachidonate cascade leading to the generation of prostaglandins, and oxygen free radicals can be produced during the interconversion of the prostaglandins. In conclusion, it has been emphasized that the two seemingly different causative factors of reperfusion injury, intracellular calcium overloading and free radical generation are, in fact, highly interrelated.

Re-examining the clinical safety and roles of calcium antagonists in cardiovascular medicine

Despite recent analyses questioning the safety of calcium antagonists, evidence and clinical practice strongly support a major role for these drugs in the management of many cardiovascular diseases such as arrhythmia, vascular spasm, hypertension, diastolic dysfunction, stable angina, and myocardial infarction. These agents are a heterogeneous class of drugs with each formulation possessing unique properties and clinical applications. This article presents a review of the available literature and discusses the recommended use of various calcium antagonists in the treatment of diseases of the heart and vascular system.

Pharmacologic therapies after myocardial infarction

Despite the availability and use of effective methods for limiting infarct size with thrombolytic agents and primary angioplasty, patients experiencing a myocardial infarction (MI) are at increased risk for a second cardiac event in the post-MI period (e.g., reinfarction, heart failure, and sudden death). For this reason, postinfarction risk management is crucial. An extensive data base has firmly established the efficacy of beta blockers in reducing cardiovascular risk following acute MI. The full advantages of angiotensin-converting enzyme (ACE) inhibitors have only recently begun to emerge as the result of a growing understanding of the mechanisms of adverse outcomes following MI. The importance of lipid-lowering agents, in particular the "statins," should be considered in all post-MI patients, especially since recent studies have conclusively shown improved survival and reduced rates of MI and coronary artery bypass surgery in this population with this therapy. Aspirin is now considered a standard part of the early management of the acute infarct patient as well as for secondary prevention in post-MI patients. At present, chronic anticoagulation with warfarin should be reserved for selected patients. The nondihydropyridine calcium antagonists diltiazem and verapamil can be considered for post-MI use only in patients in whom beta blockers are contraindicated and who have preserved systolic function and/or those without clinical heart failure. In contrast, the dihydropyridine calcium antagonists, particularly nifedipine, have no role in secondary prevention. Although long-term benefits are minimal, nitrates continue to be useful in post-MI patients with residual ischemia (angina or silent ischemia), heart failure (systolic or diastolic), or postinfarction hypertension. Antiarrhythmic agents, except amiodarone, are relatively contraindicated in post-MI patients. Recent data show that vitamin E reduces the rate of nonfatal MI. Its role in cardiovascular death and overall mortality remains to be clarified. Despite their demonstrated value, agents used in secondary prevention generally appear to be underutilized. In addition, when pharmacologic therapies are administered for secondary prevention, they are often prescribed at lower doses than those tested and proved in trials. A greater appreciation for the efficacy and safety profiles of these agents could lead to more widespread use and more pronounced reductions in morbidity and mortality among post-MI patients.

Actions of CP-060S on veratridine-induced Ca2+ overload in cardiomyocytes and mechanical activities in vascular strips

CP-060S, (-)-(S)-2-[3,5-bis(1, 1-dimethylethyl)-4-hydroxyphenyl]-3-[3-[N-methyl-N-[2-(3, 4-methylenedioxyphenoxy)ethyl]amino]propyl]-1,3-thiazolidin- 4-one hydrogen fumarate, is a novel cardioprotective drug which is designed to prevent Ca2+ overload and cause vasorelaxation. The effects of this compound were evaluated and compared with those of CP-060R (enantiomer of CP-060S,) and diltiazem (Ca2+ channel antagonist) in a veratridine-induced model of Ca2+ overload and vasorelaxation. After 5-min superfusion of veratridine (74 microM), intracellular free calcium concentrations ([Ca2+]i) of rat single cardiomyocytes, as measured with the fura-2 procedure, were greatly elevated, from 44 +/- 5 nM to 3705 +/- 942 nM, and subsequently generated cell contracture. Pretreatment of cardiomyocytes with more than 300 nM of CP-060S or CP-060R for 30 min provided almost complete protection against the veratridine-induced cell contracture; in CP-060S(1 microM)-treated myocytes, [Ca2+]i were minimal and partially elevated from 42 +/- 5 nM to 72 +/- 14 nM after 5 min of veratridine superfusion. In comparison, diltiazem showed no protection below 1 microM and only partial protection at 10 microM. CP-060S, CP-060R and diltiazem all shifted the concentration-response curve for CaCl2 to the right in a competitive manner in depolarized rat thoracic aorta. The pA2 values of CP-060S, CP-060R and diltiazem were 9.16 +/- 0.18, 8.24 +/- 0.14 and 7.66 +/- 0.09, respectively. Our results indicate that CP-060 behaves stereoselectively as a Ca2+ channel antagonist and non-stereo-selectively to protect against veratridine-induced contracture. The latter effect suggests that Ca2+ entry blockade is not the mechanism by which CP-060S exerts cardioprotection.

Calcium channel antagonists should be among the first-line drugs in the management of cardiovascular disease

There are a number of cardiovascular conditions in which calcium channel antagonists (CCAs) are accepted as first-line therapy, including Prinzmetal's angina and Raynaud's phenomenon. The real issue is whether symptomatic relief of angina or effective reduction of blood pressure (BP) is matched by a good safety record. In effort angina, verapamil is as safe as metoprolol, and nifedipine (tablet form) is as safe as atenolol. In unstable angina, intravenous diltiazem is better than intravenous nitroglycerin; there are no similar data on beta-blockade. Short-acting nifedipine is contraindicated in unstable angina. There is no place for CCAs in acute phase myocardial infarction and short-acting nifedipine is contraindicated. In the post-MI phase, two specific groups of patients benefit from diltiazem or verapamil: (1) those who had non-Q-wave infarcts and (2) those who are hypertensive. The DAVIT studies argue for the safety and efficacy of verapamil but do not allow comparisons with standard beta-blocker therapy. In the treatment of hypertension, the recommendation often made that a low-dose diuretic should be first-line therapy holds for the elderly with systolic hypertension but is not based on prospective studies in the case of younger patients. High-dose diuretics may have adverse effects, as reported in two case-controlled studies. Prospective outcome data favoring beta-blocker monotherapy as first-line therapy are limited, especially in the elderly, while case-control studies suggest an increased incidence of cardiac death in those treated by beta-blockers. CCAs may be the preferred first-line antihypertensive treatment for those groups in whom low-dose diuretics are unlikely to work as monotherapy.

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

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

Age and severe adverse drug reactions caused by nifedipine and verapamil. Gruppo Italiano di Farmacovigilanza nell' Anziano (GIFA)

The association of age with risk for severe adverse drug reactions (SADRs) was studied in 2371 and 862 hospitalized patients taking nifedipine and verapamil, respectively. Nifedipine caused hypotension (n = 22), tachycardia (n = 3), and acute renal failure (n = 1) (total SADR rate, 1.1%, 26/2371). Verapamil caused hypotension (n = 3), bradycardia (n = 9), and atrioventricular blocks (n = 2) (total SADR rate, 1.6%, 14/862). The mean age of patients with and without SADRs was for nifedipine 77.1 +/- 1.7 and 71.8 +/- 0.8 years, respectively (p < 0.05), and for verapamil 73.4 +/- 2.9 and 73.1 +/- 0.4 years, respectively. Sex, length of stay, comorbidity, polypharmacy, intake of slow-release preparations, daily dosage, and new intake of calcium antagonists were examined as potential confounders of the age-SADR association. After adjusting for potential confounders, age was significantly and independently associated with SADRs caused by nifedipine, but not with SADRs caused by verapamil (OR = 1.69, 95% CI = 1.05-2.72 and OR = 1.06, 95% CI = 0.63-1.68 for 10-year increase, respectively). Although nifedipine and verapamil did not have significantly different rates of SADRs, an age-related gradient was found only for nifedipine.

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

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

Pharmacologic profile of survivors of acute myocardial infarction at United States academic hospitals

Optimal drug therapy for patients with acute myocardial infarction (AMI) is well described in the medical literature. However, data on the actual pharmacologic management of patients surviving AMI at academic hospitals is unavailable. The purpose of this study was to document treatment profiles in 500 patients surviving AMI at 12 academic hospitals in the United States. These profiles were compared with established guidelines and were evaluated for trends. Overall, thrombolytics (streptokinase > or = tissue-type plasminogen activator) were administered in 29% of the patients, with a greater proportion of patients receiving beta-blockers than calcium channel antagonists in the initial 72 hours (61% vs 40%; p < 0.005) and at discharge (51% vs 35%; p < 0.005). Further, women were less likely than men to receive thrombolytic therapy (odds ratio [OR] = 0.61; confidence interval [CI], 0.54 to 0.69) or beta-blocker therapy within the first 72 hours (OR = 0.61; CI, 0.55 to 0.67) or at hospital discharge (OR = 0.53; CI, 0.48 to 0.58). Overall, improvements could still be made in the number of patients who receive thrombolytic and acute and chronic beta-blocker therapies after AMI, particularly in women. Changes in treatment profiles may be a reflection of the publication of large clinical trials.

Medical therapy of acute myocardial infarction: Part II. The role of adjunctive medical therapy

The second part of this review summarizes the role of other classes of pharmacological therapy in treatment of acute myocardial infarction (MI). The goals of pharmacological therapy are to alleviate symptoms, to stabilize hemodynamic status, and to prevent arrhythmias. These agents have been utilized primarily because of their ability to limit infarct size. Other beneficial properties may include their effects on neurohormonal activation, hemodynamics, and arrhythmias. In an individual patient, age, associated medical conditions, and hemodynamic status are important considerations in choosing a specific class of drug therapy. The beta-adrenergic blocking agents have modest effects on mortality, and they are useful when used alone and in combination with thrombolytic agents. Calcium antagonists have a limited role in acute MI. Diltiazem reduces the incidence of reinfarction in patients with non-Q MI. Oral nitrate therapy has not been shown to reduce mortality. Data from recent trials suggest that prophylactic administration of antiarrhthymic therapy is also not useful in acute MI. The role of angiotensin-converting enzyme inhibitors when administered in the acute phase of MI needs to be evaluated further. These agents are safe and well tolerated, and they offer greatest benefit when given in patients with left ventricular dysfunction.

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.

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.

Sustained release nifedipine formulations. An appraisal of their current uses and prospective roles in the treatment of hypertension, ischaemic heart disease and peripheral vascular disorders

Nifedipine antagonises influx of calcium through cell membrane slow channels, and sustained release formulations of the calcium channel blocker have been shown to be effective in the treatment of mild to moderate hypertension and both stable and variant angina pectoris. Preliminary findings also indicate that these formulations are effective in the treatment of Raynaud's phenomenon and hypertension in pregnancy, and that they reduce the frequency of ischaemic episodes in some patients with silent myocardial ischaemia. The exact mechanism of action of nifedipine in all of these disorders has not been defined. However, its potent peripheral and coronary arterial dilator properties, together with improvements in oxygen supply/demand, are of particular importance. A major goal of sustained release therapy is to permit reductions in the frequency of nifedipine administration, preferably to once daily, and thus improve patient compliance. Two new once-daily formulations--the nifedipine gastrointestinal therapeutic system (GITS) and a fixed combination capsule comprising sustained release nifedipine 20 mg and atenolol 50 mg--have exhibited marked antihypertensive efficacy. The GITS preparation has also been used effectively in the treatment of stable angina pectoris, and both formulations appear to be well tolerated. Sustained release nifedipine formulations are generally better tolerated than their conventionally formulated counterparts, particularly with regard to reflex tachycardia. Adverse effects seem to be dose related, are mainly associated with the drug's potent vasodilatory action, and include headache, flushing and dizziness. Generally, these effects are mild to moderate in severity and transient, usually diminishing with continued treatment. Thus, sustained release nifedipine formulations are useful and established cardiovascular therapeutic agents which have demonstrable efficacy in various forms of angina, mild to moderate hypertension and Raynaud's phenomenon. Further, promising results shown by the nifedipine GITS formulation, with its advantage of once daily administration suggest that it is likely to become one of the preferred nifedipine formulations for the treatment of hypertension and the various forms of angina.

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

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

Comparison of dihydropyridine and phenylalkylamine calcium antagonists in patients with coronary heart disease

To evaluate possible differences between dihydropyridine and phenylalkylamine calcium antagonists in the setting of chronic stable angina, 2 placebo-controlled, double-blind, crossover trials were conducted comparing the effects of gallopamil and nifedipine on exercise tolerance and ischaemic ST depression, using standard as well as slow release formulations. In the first study, 30 patients received standard formulations of gallopamil (50mg 3 times daily) and nifedipine (20mg 3 times daily). This trial was stopped after 9 patients had been enrolled, because of severe exacerbation of angina in 3 nifedipine recipients. 21 patients then entered a second protocol in which the nifedipine dose was reduced to 10mg 3 times daily. Compared with the preceding placebo periods, time to angina onset and total exercise time were statistically significantly (p less than 0.01) prolonged by gallopamil (by 30 and 18%, respectively), and nonsignificantly prolonged by nifedipine (by 20 and 13%, respectively), after 4 weeks' treatment. Increases in heart rate and rate-pressure product at maximal comparable workloads were less with gallopamil than with nifedipine (p less than 0.01). In contrast to nifedipine, gallopamil was associated with very few side effects. The second trial comprised 24 patients who received slow release formulations of gallopamil (100mg twice daily) and nifedipine (20mg twice daily) over 2 weeks. Again, both drugs exhibited significant anti-ischaemic efficacy, as evidenced by reductions in ST depression at maximal comparable workloads and increases in exercise time compared with placebo, but the differences between the treatments were not statistically significant. Side effects were more frequent with nifedipine, but less severe than with the standard formulation.(ABSTRACT TRUNCATED AT 250 WORDS)

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.

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.

Use of heart rate spectral analysis to study the effects of calcium channel blockers on sympathetic activity after myocardial infarction

We used spectral analysis of heart rate variability (HRV) to study the effects of the calcium channel blockers diltiazem and nifedipine and the beta-blocker metoprolol on the sympathetic nervous system in patients following myocardial infarction. Energy in the low-frequency range (0.04 to 0.12 Hz) in the standing (tilt) position was used as a quantitative index of sympathetic activity. Twenty-seven male patients, mean age 62 +/- 13 years, were studied 2 to 6 weeks after myocardial infarction. Eight patients received metoprolol, 100 mg twice daily; nine patients received diltiazem, 60 mg three times daily; and 10 patients received nifedipine, 10 mg three times daily. HRV and arterial blood pressure were recorded before and 5 to 7 days after initiation of therapy. None of the drugs had significant effects on the systolic blood pressure, and only nifedipine significantly reduced the diastolic blood pressure. Metoprolol and diltiazem reduced the low-frequency HRV in all patients studied, but nifedipine had no consistent effects. Our results suggest that diltiazem had a depressant effect on sympathetic activity similar to beta-adrenergic blockers. This effect was not observed with nifedipine. The reduction in sympathetic activity by diltiazem may contribute to its therapeutic effects in the post-infarction period.

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

OBJECTIVE

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

DESIGN

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

PATIENTS

19,000 Patients in 28 randomised trials.

RESULTS

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

CONCLUSIONS

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

Calcium antagonists and myocardial protection

Painful and asymptomatic ischemia has been associated with left ventricular dysfunction, an important variable related to survival in patients with coronary artery disease. The treatment of patients with coronary artery disease with agents such as calcium channel blockers has been directed at reducing ischemia by restoring the balance between myocardial oxygen supply and demand, which ultimately serves to protect against myocardial dysfunction. Once ischemia has occurred, calcium channel blockers may protect myocardial cellular integrity and function. By reducing intracellular calcium overload during ischemia, mitochondrial function is preserved and adenosine triphosphate stores are maintained. Numerous in vitro and isolated heart preparations have shown that ischemia in the presence of calcium blockade is associated with less cellular dysfunction than in the situation of ischemia in the absence of calcium channel blockade.

Calcium-channel blockers in acute myocardial infarction

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

Prolonged protective effect of the calcium antagonist anipamil on the ischemic reperfused rabbit myocardium: comparison with verapamil

To assess whether pretreatment with the calcium antagonist anipamil protects the heart against ischemic and reperfusion damage and to establish how long the protection persists after cessation of the therapy, rabbits were injected subcutaneously twice daily for 5 days with 2 mg/kg body weight of this drug. The heart was then isolated 2, 6, or 12 hours after the last injection and was perfused by the Langendorff technique during a control period and 90 minutes of total ischemia (37 degrees C), followed by 30 minutes of reperfusion. Diastolic and developed pressure was monitored; coronary effluent was collected and assayed for creatine phosphokinase (CPK); mitochondria were harvested and assayed for respiratory activity, ATP production, and calcium content; and tissue concentration of adenosine triphosphate (ATP) and creatine phosphate were determined. The data obtained with anipamil were compared with those obtained with verapamil administered to the rabbit at the same dose and following the same procedure. Pretreatment with anipamil induced a negative inotropic effect under normoxic conditions; reduced the rate and extent of depletion of ATP and creatine phosphate during ischemia, with an incomplete restoration of the nucleotides after reperfusion; maintained mitochondrial function and calcium homeostasis during ischemia and reperfusion; reduced the rate of CPK release; and improved the recovery of ventricular function on reperfusion. The protective effects of anipamil persisted for as long as 12 hours after the last administration. In contrast, the protective and negative inotropic effects of verapamil were no longer apparent in heart isolated 6 or 12 hours after the last dose of the drug.(ABSTRACT TRUNCATED AT 250 WORDS)

Thrombolytic agents in early myocardial infarction

The current revolution in the treatment of acute myocardial infarction by means of thrombolytic therapy has as its underlying strategy 3 aims: early restoration of the blood flow in order to salvage jeopardized but still viable tissues, limitation of the ultimate infarct size, and preservation, as far as possible, of ventricular function. The hope is that these 3 achievements will result in reduced short- and long-term mortality rates. The techniques used in this overall strategy are still under investigation. Three leading pharmacologic compounds vie for supremacy: streptokinase as well as its anisoylated form, recombinant technique tissue-type plasminogen activator and urokinase with or without prourokinase. In addition, the underlying anatomy may require early, or delayed, percutaneous transluminal coronary angioplasty where needed backed by coronary artery bypass grafting. Thus, the tactics of the intervention may vary from case to case and indeed from center to center depending on experience and facilities, but the conclusion is clearly the same: Early reperfusion is a must if one wishes to save ischemic but viable tissue. This report summarizes the current evidence for this new strategy.

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.

The acute effects of intravenous nisoldipine on left ventricular function 24 to 72 hours after uncomplicated acute myocardial infarction

The acute effects on left ventricular function of nisoldipine were studied in six patients 56 +/- 12 hours (range 44 to 72 hours) after the onset of uncomplicated acute myocardial infarction. Nisoldipine was administered as a 4.5 micrograms/kg intravenous bolus over 3 minutes followed by an infusion of 0.2 microgram/kg during 60 minutes. Radionuclide angiography and two-dimensional echocardiography were performed before and during infusion with nisoldipine. The left ventricular ejection fraction increased significantly from 38% +/- 10% to 49% +/- 10% (P = 0.028) during nisoldipine infusion. Regional wall motion index was determined both by radionuclide and by two-dimensional echocardiography and showed a significant change during nisoldipine infusion from 1.9 +/- 0.3 to 1.5 +/- 0.3 (p = 0.028, radionuclide angiography) and from 0.7 +/- 0.2 to 0.3 +/- 0.2 (p = 0.043, two dimensional echocardiography). Heart rate increased significantly from 78 +/- 12 min-1 to 92 +/- 13 min-1 (p = 0.028), but mean double product did not change significantly during nisoldipine infusion. It is concluded that nisoldipine significantly improves global and regional left ventricular function in patients shortly after acute myocardial infarction. This beneficial effect may, however, be partially offset by an increase in heart rate. Since mean double product did not change, it is suggested that nisoldipine may improve coronary blood flow in patients with acute myocardial infarction.

Calcium metabolism, calcium-channel blocking agents, and hypertension management

Increasing evidence has suggested that a disturbance of cellular calcium metabolism may have a role in initiating and maintaining elevated systemic vascular resistance in essential hypertension. Controversy exists over whether calcium can alleviate or exacerbate the hypertensive process, and diversity of calcium metabolism in hypertensive patients has been proposed. Calcium-channel blocking agents are potent vasodilators capable of correcting the elevated systemic vascular resistance. Clinical studies have shown that these drugs have antihypertensive efficacy comparable to established agents. The elderly, blacks, and patients with low renin activity respond well to calcium-channel blockers. These drugs may also offer potential advantages over established antihypertensive agents in patients with other coexisting diseases. Sustained release formulations have been developed, and initial experience with long-term efficacy and tolerability is encouraging. The calcium-channel blockers may become first-line therapy for treatment of hypertension in selected patients.

The effect of diltiazem on mortality and reinfarction after myocardial infarction

We studied the effect of diltiazem on mortality and reinfarction in 2466 patients with previous infarction from 38 hospitals in the United States and Canada. The patients were randomly assigned to receive diltiazem (240 mg per day, n = 1234) or placebo (n = 1232) and followed for 12 to 52 months (mean, 25). Total mortality rates were nearly identical among the two treatment groups (167 and 166, respectively), as were cumulative mortality rates. There were 11 percent fewer first recurrent cardiac events (death from cardiac causes or nonfatal reinfarction) in the diltiazem group than in the placebo group (202 vs. 226; Cox hazard ratio, 0.90; 95 percent confidence limits, 0.74 and 1.08). A significant (P = 0.0042) bidirectional interaction between diltiazem and pulmonary congestion was observed on x-ray examination. In 1909 patients without pulmonary congestion, diltiazem was associated with a reduced number of cardiac events (hazard ratio, 0.77; 95 percent confidence limits, 0.61 and 0.98); in 490 patients with pulmonary congestion, diltiazem was associated with an increased number of cardiac events (hazard ratio, 1.41; 95 percent confidence limits, 1.01 and 1.96). A similar pattern was observed with respect to the ejection fraction, which was dichotomized at 0.40. Thus, diltiazem exerted no overall effect on mortality or cardiac events in this population of patients with previous infarction. This neutral effect reflected a diltiazem-related reduction in cardiac events in the majority of patients without left ventricular dysfunction and an increase in such events in the minority of patients with left ventricular dysfunction.

Effect of diltiazem on myocardial infarct size estimated by enzyme release, serial thallium-201 single-photon emission computed tomography and radionuclide angiography

Diltiazem is a calcium antagonist with demonstrated experimental cardioprotective effects. Its effects on myocardial infarct size were studied in 34 patients admitted within 6 hours after the first symptoms of acute myocardial infarction. These patients were randomized, double-blind to placebo or diltiazem (10-mg intravenous bolus followed by 15 mg/hr intravenous infusion during 72 hours, followed by 4 X 60 mg during 21 days). Myocardial infarct size was assessed by plasma creatine kinase and creatine kinase-MB indexes, perfusion defect scores using single-photon emission computed tomography with thallium-201 and left ventricular ejection fraction measured by radionuclide angiography. Tomographic and angiographic scanning was performed serially before randomization, after 48 hours and 21 days later. Groups were comparable in terms of age, sex, inclusion time and baseline infarct location and size. Results showed no difference in creatine kinase and creatine kinase-MB data between controls and treated patients, a significant decrease in the perfusion defect scores in the diltiazem group (+0.1 +/- 3.0 placebo vs -2.2 +/- 1.9 diltiazem, p less than 0.02) and a better ejection fraction recovery in the diltiazem group (-4.2 +/- 7.4 placebo vs +7.7 +/- 11.2 diltiazem, p less than 0.05). Myocardial infarct size estimates from perfusion defect scores and enzyme data were closely correlated. These preliminary results suggest that diltiazem may reduce ischemic injury in acute myocardial infarction.(ABSTRACT TRUNCATED AT 250 WORDS)

Secondary prevention after myocardial infarction: effects of beta blocking agents and calcium antagonists

Therapeutic interventions in patients with myocardial infarction, whether during the first hours after coronary occlusion or several days later, aim to reduce mortality and morbidity by several mechanisms: Prevention of fatal ventricular fibrillation, limitation of infarct size, and inhibition of platelet aggregation are some examples of such mechanisms. Results from early intervention trials with beta blocking agents, particularly from ISIS-I, suggest that 1-year mortality is significantly lower in selected patients randomized to active treatment. Late intervention studies also suggest a significant reduction in coronary mortality and morbidity with beta blockade, particularly when data are pooled. Studies with the calcium channel blockers nifedipine and verapamil were unable to demonstrate any beneficial effects of these drugs on mortality or reinfarction. In this review article, attention will be directed to the most recent information about the preventive value of beta adrenergic blocking drugs and slow calcium channel inhibitors.