Nifedipine in acute myocardial infarction: an assessment of left ventricular function, infarct size, and infarct expansion. A double blind, randomised, placebo controlled trial

Why Is Infarct Expansion Such an Elusive Therapeutic Target?

Myocardial infarct expansion has been associated with an increased risk of infarct rupture and progression to heart failure, motivating therapies such as infarct restraint and polymer injection that aim to limit infarct expansion. However, an exhaustive review of quantitative studies of infarct remodeling reveals that only half found chronic in-plane expansion, and many reported in-plane compaction. Using a finite element model, we demonstrate that the balance between scar stiffening due to collagen accumulation and increased wall stresses due to infarct thinning can produce either expansion or compaction in the pressurized heart-potentially explaining variability in the literature-and that loaded dimensions are much more sensitive to changes in thickness than in stiffness. Our analysis challenges the concept that in-plane expansion is a central feature of post-infarction remodeling; rather, available data suggest that radial thinning is the dominant process during infarct healing and may be an attractive therapeutic target.

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.

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.

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

BACKGROUND

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

METHODS AND RESULTS

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

CONCLUSIONS

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

Ventricular dilatation and remodeling after myocardial infarction

OBJECTIVE

To discuss the important predictors of ventricular enlargement after myocardial infarction and the appropriate time frame for the initiation of medical and pharmacologic therapy.

DESIGN

A review of the important contributions relative to the process known as "postinfarction ventricular remodeling" is provided; current clinical implications and areas for future investigation are discussed.

MATERIAL AND METHODS

Ventricular dilatation is an important factor in the prognosis after infarction. Stretching and thinning of the myocardium within the infarct region can be seen within hours after the acute event and may be accompanied by delayed but potentially progressive stretching and thinning in the noninfarct regions. Development of left ventricular hypertrophy in the nonischemic myocardium, in response to increased wall stress, can be observed but may be insufficient for proper compensation. This process is referred to as postinfarction remodeling and can result in progressive and long-term changes in ventricular architecture and function in the absence of additional ischemic injury.

RESULTS

The most effective way to limit the extent of postinfarction ventricular remodeling is to limit infarct size by prompt medical intervention within the first few hours. In addition to traditional post-infarction medications such as beta-blockers, nitrates, and aspirin, long-term benefit may be derived by use of adjunctive pharmacologic therapy such as angiotensin converting enzyme inhibitors, which have been shown to be valuable in limiting the extent of ventricular chamber dilatation after infarction. Studies in animal models and conclusions from clinical trials have shown that angiotensin converting enzyme inhibitors also decrease late mortality and cardiac morbidity after infarction, likely through favorable effects on both hemodynamic and neurohumoral factors specific to this class of medication.

CONCLUSION

These investigations notwithstanding, further studies are necessary for a complete understanding of the pathogenesis of postinfarction ventricular remodeling and the appropriate timing of specific pharmacologic therapy intended to limit ventricular dilatation. The hemodynamic and neurohumoral interactions on and within the heart must be thoroughly understood relative to microscopic and macroscopic changes in cardiac size, shape, and function after myocardial infarction.

Role of calcium antagonists in progression of arteriosclerosis. Evidence from animal experiments and clinical experience. Part I. Preventive effects of calcium antagonists in animal experiments

The quantitative predominance of free and total cholesterol over the amount of mural calcium is a most significant criterion of healthy human coronary arteries during the whole life span (0-90 years). However, this normal ratio increasingly changes as soon as arteriosclerotic alterations of the coronary walls set in. Accordingly, the mural calcium content steadily rises from fatty streaks over severe arteriosclerosis and, lastly, seems to reach a climax in plaques which caused lethal coronary infarction. Furthermore, the severe arteriosclerosis of human art. dorsalis pedis with gangrene (and amputation) is characterized by a tremendous calcium incorporation and absence of any mural cholesterol changes. Only in rare cases of human basilary plaques was a dangerous cholesterol incorporation in brain arterial wall found without significant elevation of serum cholesterol levels. The presented data indicate the existence of two different types of arteriosclerosis in one and the same patient and two basically different types of experimental coronary plaques according to their chemical composition, microscopic aspect and responsiveness to calcium antagonists: 1) the calcium type, developing in vitamin-D3-treated rats, and 2) the cholesterol type, represented by fatty coronary atheromata of cholesterol-fed rabbits. Coronary atheromata of cholesterol-fed New Zealand rabbits may be suitable models for coronary heart disease in rare cases of human familiar hypercholesterolemia. The formation of conventional human coronary artery plaques, however, essentially requires a progressive uptake of calcium, thereby representing a calcium dominated type of arteriosclerosis. Calcium antagonists specifically inhibit progredient mural calcium uptake in all experimental models of arteriosclerosis tested so far. However, neither in atheromatous arteries nor in afflicted organs (myocardium, liver, kidneys) of cholesterol-fed rabbits were we able to find any significant prevention of cholesterol accumulation by calcium antagonist.

Clinical experience in protecting the failing heart

Several large, carefully randomized studies of pharmaceutical agents in the treatment of patients with congestive heart failure (CHF) and left ventricular dysfunction have demonstrated conclusively that angiotensin-converting enzyme (ACE) inhibitors reduce mortality among patients with CHF, as well as the number of hospitalizations for heart failure, myocardial infarction (MI), and angina. ACE inhibitors also have been shown to prevent the development of heart failure in patients with asymptomatic left ventricular dysfunction. Phosphodiesterase inhibitors and the beta agonists have been shown to increase mortality with no beneficial effect on morbidity. The role of digitalis remains controversial. On the one hand, the limited data available suggest that digoxin prevents clinical deterioration in patients with heart failure, even in the presence of sinus rhythm. On the other hand, when administered after MI, digoxin has been associated with increased mortality. Such conclusions are unreliable, however, since it is impossible to adjust statistically for the fact that digoxin is used in sicker patients. This question will be addressed in a large randomized study currently being conducted by the Digitalis Investigation Group. Pharmacologic approaches to the reduction of sudden death currently being explored include amiodarone, oral magnesium supplements, and beta blockers. According to the Cardiac Arrhythmia Suppression Trial and other studies, the class I antiarrhythmic agents appear unpromising or even harmful. The calcium channel blockers also appear to be contraindicated as routine therapy for CHF.

Role of nitrates in acute myocardial infarction

In patients with acute myocardial infarction, intravenous nitroglycerin lowers left ventricular filling pressure and systemic vascular resistance. At lower infusion rates (less than 50 micrograms/min) nitroglycerin is principally a venodilator, whereas at higher infusion rates more balanced venous and arterial dilating effects are seen. Patients with left ventricular failure demonstrate increased or maintained stroke volumes, whereas patients without failure show a decrease in stroke volume. All hemodynamic subgroups show a decrease in left ventricular filling pressures and a reduction in electrocardiographic evidence of regional myocardial ischemia. Longer-term infusions (24-48 hours) have been shown to result in myocardial preservation, as assessed by global and regional left ventricular function and laboratory indices of infarct size. Comparison of intravenous nitroglycerin and sodium nitroprusside reveals increased intercoronary collateral flow with nitroglycerin, in contrast to a decrease with nitroprusside, compatible with a "coronary steal." Short-term administration of intravenous nitroglycerin with or without chronic administration of long-acting nitrates have been found both to reduce short-term mortality and to have long-term beneficial effects on left ventricular remodeling in patients with anterior transmural infarctions. Current clinical practice would utilize intravenous nitroglycerin as initial therapy for patients receiving intravenous thrombolytic therapy and/or acute percutaneous transluminal coronary angioplasty within 4-6 hours of the onset of symptoms of acute myocardial infarction, in order to optimize intercoronary collateral flow until reperfusion can be accomplished. Patients reaching the hospital greater than 6 hours but less than 14 hours after symptom onset can still benefit from intravenous nitroglycerin for 24-48 hours.(ABSTRACT TRUNCATED AT 250 WORDS)

Effects of amlodipine on myocardial infarction, infarct expansion, and ventricular geometry in the rat

Infarct expansion remains an important sequela of myocardial infarction. Both angiotensin converting enzyme inhibitors and intravenous nitrates reduce early infarct expansion in humans. This is believed to be caused by the reduction in left ventricular systolic wall stress that results from the arteriolar vasodilatation they produce. Patients are frequently already receiving calcium channel blockers at the time of infarction or these drugs are sometimes administered in the perimyocardial infarction period. The calcium blockers of the dihydropyridine class might be expected to modify infarct expansion. However, their effect on this process has not been studied. We therefore evaluated the effect of early treatment with the calcium blocker amlodipine, a potent arteriolar vasodilator with minimal negative inotropic properties, on chronic myocardial infarction in the rat. Permanent left coronary occlusion was created after pretreatment with amlodipine, 0.25 mg/kg (low dose) or 1.0 mg/kg (high dose), or placebo, intravenously twice a day, and continued for 7 days after infarction. Hearts (n = 50) were perfusion fixed 21 days after infarction and analyzed for infarct extent, scar thickness, left ventricular shape and size, and expansion index. Both doses decreased mean blood pressure (119 +/- 3 to 99 +/- 5 mm Hg low dose, p = 0.004; 110 +/- 5 to 84 +/- 4 mm Hg high dose, p = 0.0003), with reflex tachycardia only after the high dose (heart rate 395 +/- 9 to 434 +/- 11, p = 0.001). Infarct extent was equal in the three groups (39 +/- 2%, 41 +/- 2%, and 41 +/- 3% of left ventricular circumference for control, low, and high doses, respectively). The three groups did not differ significantly with regard to left ventricular cavity cross-sectional area (80 +/- 4, 77 +/- 3, and 87 +/- 3 mm2, control, low, and high doses, respectively; p = 0.07 high dose vs control), mean scar thickness (0.74 +/- 0.06, 0.73 +/- 0.05, and 0.65 +/- 0.06 mm, control, low, and high doses, respectively; p = NS), and expansion index (1.52 +/- 0.10, 1.58 +/- 0.12, and 1.95 +/- 0.19, control, low, and high doses, respectively; p = 0.08 high dose vs control). In the subgroup with larger infarcts (infarct extent greater than 0.39 of left ventricle), the expansion index was higher in the high-dose group (2.37 +/- 0.23 vs 1.64 +/- 0.17 control; p = 0.04). In this model, treatment with amlodipine does not limit infarct extent or reduce early infarct expansion and left ventricular dilatation, even when initiated before infarction.(ABSTRACT TRUNCATED AT 400 WORDS)

Effects of severity of the residual stenosis of the infarct-related coronary artery on left ventricular dilation and function after acute myocardial infarction

OBJECTIVES

This study was designed to evaluate the relation between the severity of the residual stenosis of the infarct-related artery and changes in left ventricular volume and function after a first anterior myocardial infarction.

BACKGROUND

Although thrombolytic therapy improves clinical outcome after acute myocardial infarction, the relations between the severity of the residual stenosis of the infarct-related artery and postinfarction left ventricular remodeling and function are unclear.

METHODS

Fifty-eight patients with a first anterior myocardial infarction and significant disease only in the left anterior descending coronary artery on arteriography performed after 7 to 10 days were evaluated. All patients received thrombolytic therapy. Residual stenosis of the infarct-related artery was measured with quantitative coronary arteriography. Left ventricular volumes and ejection fraction were measured by echocardiography and radionuclide angiography, respectively, 7 to 10 days, 6 months and 1 year after infarction. End-diastolic and end-systolic left ventricular volumes were measured by two-dimensional echocardiography and normalized to body surface area. Patients were classified into three groups according to baseline residual stenosis severity: total occlusion (Group I), minimal lesion diameter less than 1.5 mm (Group II) and minimal diameter greater than or equal to 1.5 mm (Group III).

RESULTS

Group I patients had significantly greater left ventricular end-diastolic and end-systolic volumes at 6 months and 1 year than did the other groups. Group II patients had greater end-diastolic and end-systolic volumes than did Group III patients at 1 year. In addition, Group I patients had a lower ejection fraction at 1 year than that of the other groups. The minimal lesion diameter was significantly correlated with percent change in end-diastolic volume at 1 year.

CONCLUSIONS

The severity of the baseline residual stenosis of the infarct-related artery is an important predictor of change in left ventricular volumes in the 1st year after infarction. Total occlusion of the infarct-related artery is associated with greater left ventricular dilation and functional impairment.

Hemodynamic effects of nisoldipine, a highly specific calcium antagonist, in patients with acute myocardial infarction

The aim of the study was to investigate the hemodynamic effects of a short-acting, potent, highly specific calcium antagonist, nisoldipine, in patients with acute myocardial infarction. Twenty-four patients were selected on the basis of an elevated wedge pressure and/or elevated blood pressure, less than 12 hours after the onset of symptoms. Patients were randomized to receive either placebo or low-dose nisoldipine (2 micrograms/kg) as a single intravenous injection over a 3-minute period. hemodynamic effects were monitored for 20 minutes, and thereafter patients were crossed over to the other agent after the preserved parameters had returned to baseline. An open-label study using double the dose of nisoldipine in 20 patients who had not reacted adversely to low-dose nisoldipine followed. Standard hemodynamic monitoring showed that peak effects of nisoldipine were reached at 5 minutes, with some residual effect at 20 minutes, and it took up to 60 minutes to return to baseline. Both doses of nisoldipine had similar effects: a fall in the systemic vascular resistance by about 600 units, variable tachycardia, little or no change in the wedge pressure, a decrease in the arterial pressure, an unchanged rate-pressure product, and an increase in ejection fraction. Tachycardia of more than 15 beats/min resulted in 5 of 24 patients with low-dose nisoldipine and 6 of 20 patients with high-dose nisoldipine. In view of the risk of tachycardia, nisoldipine seems unsuitable for use in the acute phase of myocardial infarction.

The golden hours of the myocardial infarction: nonthrombolytic interventions

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

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

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

Myocardial infarction. Secondary prevention with nifedipine

The rationale for the use of nifedipine in patients with acute myocardial infarction (MI) is based on the various cardiovascular actions of the compound: reduction of myocardial oxygen consumption by attenuation of cardiac and vascular smooth muscle tension; augmentation of oxygen and substrate supply after increased coronary blood flow with dilatation of epicardial coronary arteries (particularly in coronary obstructions) and dilatation of coronary resistance and collateral vessels; myocardial 'protection', i.e. reduction of myocardial damage via a complex intracellular mechanism, the primary outcome of which is the maintenance of an energy level sufficient to preserve the ionic homeostasis of the myocyte. The effect of nifedipine on reinfarction and mortality rates was evaluated in 6 well designed studies involving 8670 patients with evolving or established acute MI. Compared with placebo, short term therapy (for up to 6 months) with nifedipine 30 to 120 mg/day initiated, in some patients, as early as 3 hours after the onset of symptoms did not reduce either reinfarction rate or mortality. In one study (SPRINT I) [Israeli Sprint Study Group 1988], where a regimen of nifedipine 30 mg/day was only started 7 to 21 days after infarction, the exceptionally low mortality rate (5.7%) over 10 months in the placebo group precluded the demonstration of a beneficial effect of nifedipine. These results collectively suggest that nifedipine does not prevent the 'secondary' coronary events of plaque rupture and thrombus formation associated with MI and sudden cardiac death. However, the suppression of early lesions by nifedipine (as demonstrated in the INTACT study [Lichtlen et al. 1990]) might reduce 'primary' progression and improve the long term survival after MI.

Management of acute non-Q-wave myocardial infarction. The role of prophylactic diltiazem therapy and indications for predischarge coronary arteriography

Non-Q-wave myocardial infarction (MI) differs from Q-wave MI in 3 important respects: a smaller infarct size, possibly due to early reperfusion resulting from spontaneous thrombolysis, relief of spasm, or both; more frequency patency of the infarct-related artery; and a larger residual mass of viable but jeopardized myocardium within the perfusion zone of the infarct-related vessel. Left ventricular function is generally better unless impaired by previous MI. After the acute phase, the prognosis is worse when residual ischaemia is present, and reinfarction rates during hospitalisation and in the subsequent year of follow-up are higher. As myocardial ischaemia is potentially reversible, its presence should be actively sought in all patients with recognised non-Q-wave MI. On the basis of current knowledge and available data, the following guidelines for the management of non-Q-wave MI patients can be recommended: (1) diltiazem and aspirin should be administered to all patients as soon as the diagnosis is established, unless contraindications exist; (2) patients who develop early recurrent ischaemia on therapy (i.e. angina with associated ST-T-wave changes) should undergo prompt cardiac catheterisation and myocardial revascularisation; and (3) patients with entirely uncomplicated hospital histories who are asymptomatic should undergo exercise stress testing, preferably in conjunction with 201Tl perfusion scintigraphy, before hospital discharge. Only those patients with evidence of significant residual ischaemia need cardiac catheterisation and myocardial revascularisation.

Protective effects of calcium antagonists against ischaemia and reperfusion damage

The most positive results in this area have been those of the second Danish Study Group on Verapamil in Myocardial Infarction (1990) which assessed the benefit of treatment with verapamil from the second week after myocardial infarction. Verapamil produced a significant reduction in both mortality and reinfarction rates. Consequently, it may be concluded that treatment with calcium antagonists, such as verapamil and diltiazem, should not be used in the acute phase of myocardial infarction, but rather as prophylaxis to prevent reinfarction by protecting against myocardial ischaemia. The lack of reported cardioprotective efficacy with calcium antagonists, which contrasts with experimental predictions, can be explained by the inappropriate timing of administration and the use of dihydropyridine, which can be detrimental in myocardial infarction. These is little or no evidence to show that calcium antagonists are cardioprotective in patients with myocardial infarction or unstable angina. Thus, the randomised trials studying acute myocardial infarction reveal no overall effect of treatment on mortality in the short or long term. The prototype calcium antagonists differ in their effects on the reinfarction rate in these patients. With verapamil there is a small tendency for a reduction in reinfarction, with nifedipine a clear worsening, and with diltiazem a reduction almost reaching statistical significance. The general lack of protective efficacy is presumably a result of the drugs being administered too late after the onset of ischaemia.

Prevention of late ventricular dilatation after acute myocardial infarction by successful thrombolytic reperfusion

To examine the sequential changes in left ventricular volume after thrombolytic therapy for acute myocardial infarction, gated radionuclide ventriculography was performed within 12 hours of thrombolysis and at 1 and 6 weeks in 34 consecutive patients who received intravenous thrombolytic therapy in the Thrombolysis in Myocardial Infarction Trial. Angiographic confirmation of immediate reperfusion (mean 5.6 hours after onset of symptoms) that persisted at 24 hours was noted in 24 patients; 10 patients were not reperfused. A small (9.5%), but significant (p = 0.05), increase in end-diastolic volume index was noted in the reperfused group between 1 and 6 weeks; however, a marked degree of dilatation (35%) was noted in the non-reperfused group (p = 0.01). The change in left ventricular volume between 1 and 6 weeks differed in the 2 groups for both end-diastolic volume index and end-systolic volume index (p = 0.01 and p = 0.02, respectively). By 6 weeks, both end-diastolic volume index and end-systolic volume index were greater in the nonreperfused group (p less than 0.05). Between the acute and 6-week studies, definite increases in end-diastolic volume index (p less than 0.05) and end-systolic volume index (p less than 0.01) occurred commonly in the nonreperfused group but rarely in the reperfused group. Compared to the nonreperfused group, the reperfused group also had significantly higher ejection fractions at both 1 and 6 weeks (p less than 0.05). The change in end-diastolic volume index between 1 and 6 weeks correlated significantly and inversely with the ejection fraction at 1 week (r = -0.60, p less than 0.001).(ABSTRACT TRUNCATED AT 250 WORDS)

Mechanical and electrical complications of acute myocardial infarction

Although much of the current enthusiasm in the management of acute myocardial infarction is related to revascularization strategies, mechanical and electrical complications continue to pose a major threat to recovery in some patients. Some of the major complications of acute myocardial infarction are cardiogenic shock, rupture of the free wall and pseudoaneurysm, rupture of the ventricular septum, acute mitral regurgitation, right ventricular myocardial infarction, infarct expansion or extension, pericarditis and tamponade, peri-infarction hypertension, and tachyarrhythmias and bradyarrhythmias. For each of these complications, general guidelines for diagnosis and management are offered. Early, aggressive, and judicious treatment of these complications may substantially decrease the morbidity and mortality associated with acute myocardial infarction.

Identification of patients prone to infarct expansion by the degree of regional shape distortion on an early two-dimensional echocardiogram after myocardial infarction

Early detection of potential expanders (patients who develop clinically significant infarct expansion with acute left ventricular (LV) dilatation and failure but no necrosis) after acute myocardial infarction (AMI) is necessary in order to apply preventive therapy. To determine whether the degree of regional shape distortion (RSD), or dilatation, on early two-dimensional echocardiogram (2-D echo) after AMI can identify potential expanders, serial clinical and echocardiographic data were studied prospectively in 244 consecutive patients with a first Q-wave AMI. Initial (mean 2 days) and final (mean 10 days) two-dimensional echocardiograms were compared for regional LV asynergy, RSD, and conventional indices of expansion measured on endocardial diastolic outlines of mid-LV short-axis sections. Analysis of clinical and 2-D echo data revealed 51 expanders and 193 nonexpanders. Expanders showed greater LV dysfunction and more inhospital deaths (27% vs. 8%, p less than 0.001) compared with nonexpanders; conventional indices of expansion showed more marked increase between initial and final two-dimensional echo in expanders, but initial indices were not predictive. In contrast, the new RSD index Pk, a measure of the outward bulge, was markedly greater in expanders than nonexpanders on both initial (16.5 vs. 2.4 mm, p less than 0.001) and final echo. Furthermore, expanders with greater than or equal to 30% increase in Pk (to 21 mm) developed rupture of the ventricular septum (n = 10) or free wall (n = 2). Also, 50 of 51 expanders compared with 3 of 193 nonexpanders had a Pk greater than or equal to 10 mm on the initial echo. A simpler index, the depth of RSD (rd), provided similar discrimination as Pk. Thus, the degree of diastolic RSD on an early 2-D echo after AMI can identify potential expanders.

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-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.

Myocardial infarction in rats: effects of metabolic and pharmacologic interventions

Myocardial infarction was induced in rats by ligation of the descending branch of the left coronary artery. The time course of changes in heart function was recorded within the first nine days. There was a progressive decline in LVSP, in LV dP/dtmax and in the pressure-rate-product. LVEDP was elevated. Cardiac output and stroke volume index were depressed after two days. The ATP content in the nonischemic region was lower than control, but recovered spontaneously toward the normal value within the first four days. Three metabolic and pharmacologic interventions known to affect cardiac adenine nucleotide metabolism were applied. Continuous i.v. administration of ribose which stimulates further adenine nucleotide biosynthesis attenuated the fall and promoted the restoration of ATP in the nonischemic myocardium within four days after coronary artery ligation. The elevation of LVEDP was attenuated with ribose after two and four days. The calcium antagonist gallopamil administered as i.v. infusion for two days led to a further reduction of all parameters of left heart function, but did not influence the increase in adenine nucleotide and protein synthesis that occurred in the nonischemic heart. Coenzyme Q10 had only slight effects on LVSP, LVEDP, and LV dP/dtmax, but attenuated significantly the fall in cardiac output and stroke volume index after two days following coronary artery ligation. Thus, all interventions affected differently the infarct-induced changes in heart and circulatory function. An improvement was observed with ribose and with coenzyme Q10.

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.

Increased afterload aggravates infarct expansion after acute myocardial infarction

After acute transmural myocardial infarction, the heart may undergo major remodeling characterized by thinning and dilation of the infarct zone and overall enlargement of the heart. The effect of increased left ventricular pressure on infarct expansion and the extent to which it alters postinfarction remodeling were studied in a rat model. Rats with either aortic banding or a sham operation and a survival period of 3 weeks were further randomized to sham thoracotomy or left coronary ligation. Surviving rats were killed 7 days later and the hearts were fixed in diastole for morphologic analysis. Hearts with aortic banding had a mean peak to peak gradient of 20.7 +/- 4.9 mm Hg across the aortic band at death and a significantly thicker heart than that of the comparison group without an aortic band. Infarct size, as a percent of total left ventricular mass, at the time of death was less in the group with aortic banding, yet infarct expansion was more marked. However, when original infarct size was estimated taking into account the effects of aortic banding, scar formation, infarct expansion and infarct-induced hypertrophy, it was found to be similar in both infarct groups (45.50 +/- 4.2 versus 47.90 +/- 3.1%). Infarct expansion, as measured by cavity dilation and infarct thinning, occurred in both infarct groups but was greater in the group with aortic banding.(ABSTRACT TRUNCATED AT 250 WORDS)