Improved survival up to four years after early coronary thrombolysis

Effect of the stenosis location and severity on left ventricular function after single-vessel anterior wall myocardial infarction

BACKGROUND

The purpose of the current study was to determine how the location of the infarct-related lesion (IRL) and the degree of stenosis during the acute and chronic phases of infarction might affect left ventricular (LV) function in patients with acute anterior wall myocardial infarction.

METHODS

Ninety consecutive patients with a first single-vessel anterior wall myocardial infarction (male/female ratio 75:15, mean age 60+/-9 years) underwent coronary angiography (CAG) immediately and 1 month after infarction. Patients were grouped according to IRL location (proximal [Coronary Artery Surgery Study (CASS) No. 12] or distal [CASS No. 13] to the first diagonal branch of the left anterior descending artery) and according to the severity of stenosis at 1 month (severe stenosis [IRL >75%] and mild stenosis [IRL < or =75%]). At the time of infarction and 1 month and 1 year after infarction, total wall motion index (TWMI), left ventricular end-diastolic dimension (LVDd), left ventricular end-systolic dimension (LVDs), and fractional shortening (FS) were determined.

RESULTS

TWMI was greater and FS was lower for CASS No. 12 lesions than for CASS No. 13 lesions. CASS No. 12 lesions were associated with a greater LVDd at 1 year and a greater LVDs throughout 1 year of observation. The patients with mild stenoses had significant improvements in TWMI and FS over time, whereas those with severe stenoses showed no improvement. Multivariate analysis showed that the independent factors predicting left ventricular function were IRL location at CASS No. 12, initial TIMI 0-1 flow in the IRL at emergency coronary artery graft, and the presence of a severe stenosis at 1 month.

CONCLUSIONS

In patients with severe stenoses at 1 month at CASS No. 12, left ventricular functional recovery is delayed and the left ventricular chamber is enlarged. In patients with CASS No. 13 lesions, left ventricular function is preserved well, regardless of the severity of residual stenosis.

Influence of early prehospital thrombolysis on mortality and event-free survival (the Myocardial Infarction Triage and Intervention [MITI] Randomized Trial). MITI Project Investigators

The Myocardial Infarction Triage and Intervention Trial of prehospital versus hospital administration of thrombolytic therapy markedly reduced hospital treatment times, but the 2 groups had similar outcomes. However, patients treated < 70 minutes from symptom onset had better short-term outcomes. The purpose of this study was to determine the long-term influence of very early thrombolytic treatment for acute myocardial infarction. A total of 360 patients were followed for vital status and cardiac-related hospital admissions over a period of 34 +/- 16 months. Patients enrolled in the trial had symptoms for < or = 6 hours, ST-segment elevation on the prehospital electrocardiogram, and no risk factors for serious bleeding. They received aspirin and recombinant tissue plasminogen activator either before or after hospital arrival. Primary end points in this study included long-term survival and survival free of death or readmission to the hospital for angina, myocardial infarction, congestive heart failure, or revascularization. Two-year survival was 89% for prehospital- and 91% for hospital-treated patients (p = 0.46). Event-free survival at 2 years was 56% and 64% for prehospital- and hospital-treated patients, respectively (p = 0.42). In patients treated < 70 minutes from symptom onset, 2-year survival was 98%, and it was 88% for those treated later (p = 0.12). Two-year event-free survival was 65% for patients treated early and 59% for patients treated later (p = 0.80). In this trial, poorer long-term survival was associated with advanced age, history of congestive heart failure, and coronary artery bypass surgery performed before the index hospitalization, but not with time to treatment.

Importance of infarct-related artery patency for recovery of left ventricular function and late survival after primary angioplasty for acute myocardial infarction

OBJECTIVES

The purpose of this study was to evaluate the importance of late infarct-related artery patency for recovery of left ventricular function and late survival after primary angio-plasty for acute myocardial infarction.

BACKGROUND

Infarct-related artery patency is thought to improve late survival by its effect on preservation of left ventricular function. Patency may also enhance late survival by preventing left ventricular dilation and reducing arrhythmias, independent of myocardial salvage. However, most studies have not shown patency to be an independent predictor of survival when late left ventricular function is taken into account.

METHODS

We followed up 576 hospital survivors of acute myocardial infarction treated with primary angioplasty for 5.3 years. Ejection fraction and infarct-related artery patency were determined at follow-up catheterization at 6 months. Predictors of late cardiac survival were determined using Cox regression models.

RESULTS

Patients with patent arteries had more improvement and a better late ejection fraction than patients with occluded arteries (56.3% vs. 47.9%, p = 0.001). In patients with acute ejection fraction < 45%, late survival was better in those with patent versus occluded arteries (89% vs. 44%, p = 0.003), but patency was not a significant predictor after improvement in ejection fraction was taken into account. In patients with a large anterior infarction, patency was a significant independent predictor of late survival.

CONCLUSIONS

Infarct-related artery patency is important for recovery of left ventricular function, and in patients with acute ejection fraction < 45%, patency is important for late survival. Our data are consistent with the hypothesis that the survival benefit is due primarily to the effect of patency on recovery of left ventricular function. In patients with a large anterior infarction, patency appears to provide an additional late survival benefit independent of myocardial salvage. These observations support the need for additional clinical trials of late reperfusion in patients with a large anterior infarction.

Benefits of late coronary artery reperfusion on infarct expansion progressively diminish over time: relation to viable islets of myocytes within the scar

To define the time limit and mechanism of the effects of late coronary artery reperfusion on infarct expansion, rats were randomized into one of four groups: permanent left coronary artery occlusion; and 2, 8, and 16 hours of left coronary artery occlusion followed by reperfusion. Two weeks after coronary occlusion, morphometric and histologic analyses were performed. Benefits of late reperfusion on infarct expansion progressively diminished after increasingly long periods of coronary occlusion and were minimal but present after 16 hours of coronary occlusion. The extent of the benefits of late reperfusion on infarct expansion were related to preservation and hypertrophy of small islets of still viable myocytes located mainly in the subepicardium of the scar.

Clinical science review: current aspects of thrombolytic therapy in women with acute myocardial infarction

Acute myocardial infarction (AMI) remains the greatest threat to health in our society and is the most common cause of death in the United States and in many other Western industrialized countries. Recent data demonstrate that mortality from MI is continuing to decline. In these days of more aggressive management of acute MI (AMI) there has been a resurgence of interest in advances in thrombolytic therapy. However, observational studies of patients with AMI have shown that women sustaining an AMI have a worse prognosis than men. AMI is the number-one killer of women in the United States; approximately 247,000 of more than 520,000 deaths due to AMI that occur each year are among women, and almost one-third of the women are younger than forty-five years old. While there have been great advances in thrombolytic therapy, these advances have benefited men to a more significant degree than they have benefited women. The purpose of this paper is to critically review the efficacy of thrombolytic therapy in women with AMI with consideration of some of the key components of its effectiveness: mortality, bleeding risk, infarct-artery patency, ventricular function, and cardiac arrhythmia.

Long-term prognosis after thrombolytic therapy for acute myocardial infarction

In order to clarify the relationship between the patency of the infarcted arteries and subsequent long-term prognosis after thrombolytic therapy, we evaluated 116 patients with acute myocardial infarction treated with intracoronary (112 patients) or intravenous (four patients) urokinase. Patients treated with angioplasty after thrombolysis were excluded. The infarcted vessel was recanalized in 52 patients (patent group) and was not in the remaining 64 patients (occluded group). Five-year and 8-year follow up was conducted in 91% and 81% of the patients, respectively. The 1-, 5- and 8-year survival rate for the patent and occluded group was 91.8 and 80.9%, 80.8 and 79.2%, and 75.9 and 75.6%, respectively. The survival rate in the patent group tended to be higher than that in the occluded group up to 4 years. However, after 5 years, both groups showed similar survival rates. Therefore, reopening of the infarcted arteries with thrombolysis was not an independent predictor for late cardiac death (Cox regression analysis).

Rapid diagnosis of coronary reperfusion by measurement of myoglobin level every 15 min in acute myocardial infarction

OBJECTIVES

The purpose of this study was to examine whether coronary reperfusion can be diagnosed rapidly and accurately by myoglobin measurements.

BACKGROUND

When intravenous thrombolysis is used for acute myocardial infarction, it is important to determine coronary reperfusion rapidly and noninvasively so that further treatment can be initiated.

METHODS

We determined myoglobin, creatine kinase (CK) and creatine kinase, MB fraction (CK-MB) isoenzyme levels in 63 patients with acute myocardial infarction with total occlusion of the infarct-related artery that was confirmed by coronary angiography. Myoglobin was measured by turbidimetric latex agglutination, which has an assay time of 10 min. We measured myoglobin, CK and CK-MB every 15 min in 45 patients with and 18 patients without reperfusion. The condition of the infarct-related artery was confirmed every 5 to 8 min by coronary angiography.

RESULTS

The rate of increase in myoglobin, CK, and CK-MB at 15, 30, 45 and 60 min after treatment and reperfusion was significantly higher in the reperfused than in the nonreperfused group. In the reperfused group, the rate of increase in myoglobin was significantly higher than the corresponding rate of increase in CK and CK-MB at 15, 30 and 45 min after reperfusion. When reperfusion was evaluated on the basis of a cutoff level (myoglobin > or = 2.0, CK > or = 1.8, CK-MB > or = 1.5), the predictive accuracy of myoglobin (95%) was significantly higher than that of CK (68%) and CK-MB (73%) at 15 min after reperfusion.

CONCLUSIONS

Coronary reperfusion can be rapidly and accurately detected by measurement of the plasma myoglobin every 15 min.

Differences in clot lysis among patients demonstrated in vitro with three thrombolytic agents (tissue-type plasminogen activator, streptokinase and urokinase)

This study compares the ability of 3 thrombolytic drugs to promote clot lysis using a new in vitro testing procedure. Whole blood samples from 132 patients were tested using 5 different concentrations of tissue-type plasminogen activator (t-PA), streptokinase (SK) and urokinase. A mixture of blood and thrombolytic drug was placed on a dry-reagent test card containing reptilase, buffers and paramagnetic particles where clot formation occurred. Analysis of the motion of the clot-embedded paramagnetic particles caused by an oscillating magnetic field was used to define the lysis onset time. The slope of the linear regression plot of lysis onset time versus 1/[drug concentration] defined the kinetic rate constant (k) for each drug in each patient. Higher values of k indicated greater resistance to in vitro clot lysis. In the patients studied, there was a large range of k values for t-PA and SK (coefficient of variation 143 and 137%, respectively) but a smaller range of k for urokinase (coefficient of variation 32%). The coefficients of variation for t-PA and SK observed in the study group were five- to 10-fold greater than the coefficients of variation determined for replicate test measurements. Resistance to all SK concentrations tested was found in 9% of the patients. In vitro sensitivity to thrombolysis was compared among the drugs by correlating the derived k values. These comparisons indicated no relation for any of the drugs; many patients had a relatively low k value for 1 drug, while having a relatively high k value for a different drug.(ABSTRACT TRUNCATED AT 250 WORDS)

Earlier diagnosis and treatment of acute myocardial infarction necessitates the need for a 'new diagnostic mind-set'

Triaging patients suspected of myocardial infarction is performed primarily in the coronary care unit, with infarction determined within 12 to 24 hours, and only about 20% are subsequently shown to have myocardial infarction. Plasma MB CK is not elevated until 8 to 10 hours after onset, and the ECG is unreliable; thus, the need has arisen for a new "diagnostic mind-set." The need is threefold: (1) more effective triaging in the emergency room to prevent unnecessary use of hospital beds, particularly those in the intensive care units, (2) to administer thrombolytic therapy in the early hours, and (3) earlier detection of coronary reocclusion and reinfarction. Diagnostic imaging techniques such as pyrophosphate, thallium-201 technetium sestamibi, or positron emitting agents lack the necessary early diagnostic specificity, but echocardiography has potential although its specificity is limited. Plasma CK isoforms provide diagnostic sensitivity and specificity of 96% and 94%, respectively, within the initial 4 to 6 hours of onset and can be assayed within minutes. In a prospective study of 1100 patients suspected of infarction, with conventional MB CK, 22% of the patients admitted to the coronary care unit would have had infarction, whereas using the CK isoforms, 75% had infarction and about 50% were discharged home. A scenario for the future might be to initiate thrombolytic therapy outside the hospital (eg, recombinant tissue-type plasminogen activator [r-TPA] 20 mg bolus) and upon arrival, confirm or exclude infarction by the MB CK isoform which can be performed in the emergency room in 20 minutes to determine whether thrombolytic therapy and heparin should be continued.

Long-term prognostic importance of patency of the infarct-related coronary artery after thrombolytic therapy for acute myocardial infarction

BACKGROUND

After thrombolytic therapy, long-term patency of the infarct-related artery may reduce arrhythmias, limit ventricular dilatation, and provide collaterals to another infarct zone if further infarction occurs. However, independent long-term prognostic value of infarct artery patency has not been shown.

METHODS AND RESULTS

We followed 312 patients with first myocardial infarction treated < 4 hours after pain onset with thrombolysis (streptokinase [n = 188] or recombinant tissue-type plasminogen activator [n = 124]). At 28 +/- 11 days, cardiac catheterization was performed. Flow of the infarct-related artery was assessed by the TIMI scoring system, and a scoring system relating coronary stenoses and flow to the amount of myocardium supplied was also used. Follow-up was for 39 +/- 13 months. Cardiac death occurred in 5.8% of patients, and there were two noncardiac deaths. Revascularization was performed in 11.5% of patients. On univariate and multivariate analysis, ventricular function (ejection fraction, P = .006 and .02, or end-systolic volume index, P = .01 and .06) was the most important prognostic factor. Patency of the infarct-related artery measured as TIMI 3 flow was marginally significant on univariate analysis (P = .08) but not on multivariate analysis (P = .2). Patency was an independent prognostic factor in univariate and multivariate analysis when measured as an occlusion score (amount of myocardium supplied by an occluded artery, P = .01 and < .05). When the ejection fraction was > or = 50%, only occluded arteries supplying > 25% of the left ventricle affected prognosis adversely. If the ejection fraction was < 50%, occluded arteries supplying < 25% of myocardium also adversely affected prognosis. Treadmill exercise duration 4 weeks after infarction was the only other prognostic factor identified.

CONCLUSIONS

Ventricular function and infarct-related artery patency are independent prognostic factors after thrombolytic therapy for acute myocardial infarction.

Limitation of infarct expansion and ventricular remodeling by late reperfusion. Study of time course and mechanism in a rat model

BACKGROUND

Reperfusion of acutely infarcted myocardium may be beneficial in limiting infarct expansion and ventricular remodeling even if established after the time that salvage of ischemic myocardium is possible.

METHODS AND RESULTS

To examine the permanency, time course, and mechanism of this effect of late reperfusion, 200 rats were randomized into one of four groups: (1) infarction with reperfusion after 1 to 2 hours, (2) infarction with reperfusion after 6 to 8 hours, (3) infarction without reperfusion, and (4) sham operation. Surviving rats were killed at either 7 days, when infarct expansion has plateaued, or 21 days, when infarct healing is complete. In both 7- and 21-day analyses, late reperfusion did not reduce infarct size or degree of transmural necrosis but significantly limited infarct expansion, as measured by an index based on infarct endocardial segment lengthening and infarct wall thinning (expansion index at 7 days: no reperfusion, 2.73 +/- 0.25, n = 13; reperfusion after 1 to 2 hours, 1.56 +/- 0.13, n = 23, P < .001; reperfusion after 6 to 8 hours, 1.78 +/- 0.15, n = 16, P = .002; at 21 days: no reperfusion, 3.45 +/- 0.39, n = 13; reperfusion after 1 to 2 hours, 2.21 +/- 0.24, n = 15, P = .01; reperfusion after 6 to 8 hours, 2.02 +/- 0.20, n = 9, P = .01). Reperfusion after 6 to 8 hours was equally effective in limiting expansion as reperfusion after 1 to 2 hours. Late reperfusion also significantly reduced ventricular remodeling at 21 days, as measured by an index based on left ventricular cavity dilatation and noninfarcted myocardial hypertrophy (remodeling index at 21 days: no reperfusion, 2.67 +/- 0.15, n = 13; reperfusion after 1 to 2 hours, 2.20 +/- 0.15, n = 15, P = .035; reperfusion after 6 to 8 hours, 2.12 +/- 0.10, n = 9, P = .012). Histological examination revealed that reperfusion accelerated the clearance of residual dead myofibrils, suggesting an increase in the rate of healing, and increased the degree of myocytolysis but did not change the final degree of infarct healing, tissue density, or viable subepicardial cells.

CONCLUSIONS

Late reperfusion causes a permanent reduction in postinfarction expansion that is present even after complete infarct healing. The time after coronary occlusion in which reperfusion is of benefit in reducing subsequent expansion and remodeling is substantially longer than previously established. The mechanism by which late reperfusion limits expansion may involve changing the rate of healing and the nature of myocardial necrosis but does not involve preserving subepicardial cells.

Late outcome after percutaneous transluminal coronary angioplasty during acute myocardial infarction

Early reperfusion for acute myocardial infarction (AMI) results in improved ventricular function and survival. There is a dearth of data on long-term survival (> 5 years) after percutaneous transluminal coronary angioplasty (PTCA) performed either as a primary procedure or in conjunction with thrombolytic therapy. We studied 160 patients who underwent PTCA during AMI between 1981 and 1987 either with (n = 101) or without (n = 59) streptokinase therapy. Mean time to reperfusion was 4.6 hours, and patency was achieved in 134 patients (84%). Mean discharge ejection fraction was 46 +/- 14%. Coronary artery bypass grafting was performed before dismissal in 34 patients (21%), including 21 of 130 patients (16%) with 1- or 2-vessel disease and 13 of 30 patients (43%) with 3-vessel disease (p < 0.05). Eleven patients (7%) died in the hospital. The 149 hospital survivors were followed for a mean of 69 +/- 21 months (median 72). During follow-up, 22 patients (15%) died, 21 (14%) had reinfarction, 23 (15%) underwent coronary artery bypass grafting, and 21 (14%) underwent repeat PTCA of the infarct-related artery. On univariate analysis, age > or = 62 years, multivessel disease, ejection fraction < or = 40%, previous AMI, and being a nonsmoker at the time of AMI were predictive of late mortality (p < 0.05 each variable). On multivariate analysis, only ejection fraction < or = 40% and prior AMI were predictive of late death. In patients treated with PTCA for AMI, late survival is excellent. Early surgical revascularization of high-risk patients may contribute to these encouraging results.

Prognosis in cardiogenic shock after acute myocardial infarction in the interventional era

OBJECTIVES

The purpose of this study is to describe the outcome in cardiogenic shock treated with aggressive reperfusion therapy and to identify factors predictive of in-hospital and long-term mortality.

BACKGROUND

Cardiogenic shock is the most common cause of death in patients admitted to the coronary care unit. Although studies have reported lower mortality rates in shock treated with angioplasty, few studies have described a cohort of patients with shock who were not selected because they were most likely to benefit from reperfusion therapy.

METHODS

A consecutive series of 200 patients admitted with acute myocardial infarction complicated by cardiogenic shock were studied.

RESULTS

The in-hospital mortality rate was 53%. Variables with significant univariable association with in-hospital death included patency of the infarct-related artery, patient age, lowest cardiac index, highest arteriovenous oxygen difference and left main coronary artery disease. The most important independent predictors of in-hospital death were patency of the infarct-related artery, cardiac index and peak creatine kinase, MB fraction. The mortality rate in patients with patent infarct-related arteries was 33% versus 75% in those with closed arteries and 84% in those in whom arterial patency was unknown. Patients who survived to hospital discharge were followed up for a median of 2 years, with a mortality rate of 18% after 1 year. The best descriptors of the relation between these variables and postdischarge mortality included age, peak creatine kinase, ejection fraction and patency of the infarct-related artery.

CONCLUSIONS

In a large consecutive series of patients with cardiogenic shock with complete follow-up, patency of the infarct-related artery was most strongly associated with in-hospital and long-term mortality. This finding supports an aggressive interventional strategy in patients with cardiogenic shock.

Long-term survival in 618 patients from the Western Washington Streptokinase in Myocardial Infarction trials

OBJECTIVES

The aim of this study was to determine whether streptokinase treatment improves long-term survival in patients with acute myocardial infarction.

BACKGROUND

Thrombolytic treatment for acute myocardial infarction reduces early mortality and improves the 1-year survival rate, but the long-term (3 to 8 years) survival benefits of treatment and the relation between survival and baseline clinical characteristics, infarct size and ventricular function have not been established.

METHODS

We assessed survival status at a minimum of 3 and a mean of 4.9 +/- 2.3 years in 618 patients randomized between 1981 and 1986 to receive conventional treatment (n = 293) or thrombolysis with streptokinase (n = 325) in the Western Washington Intracoronary (n = 250) and Intravenous (n = 368) Streptokinase in Myocardial Infarction trials. The relation between long-term survival and thrombolytic treatment, admission baseline clinical characteristics and late radionuclide tomographic thallium-201 infarct size and ejection fraction was assessed in a subset of patients.

RESULTS

Survival at 6 weeks was 94% in patients who received streptokinase versus 88% in the control group (p = 0.01). However, survival at 3 years was 84% in the streptokinase group and 82% in the control group and for the total period of follow-up, there was no significant survival benefit (p = 0.16). Analysis by infarct location showed a higher survival rate at 3 years for patients treated with anterior infarction (76% vs. 67% for the control group), but no overall survival benefit (p = 0.14). Survival at 3 years for patients with an inferior infarction was 89% in the streptokinase group and 91% in the control group (p = 0.62). By stepwise Cox regression analysis, admission clinical variables associated with decreased long-term survival were anterior infarction, advanced age, history of prior infarction and the presence of pulmonary edema or hypotension. Although streptokinase therapy was associated with improved survival, it was not an independent determinant of survival (p = 0.069). Ejection fraction and thallium-201 infarct size measured approximately 8 weeks after enrollment had a strong association with long-term survival. Univariate analysis in a subgroup of 289 patients with complete data selected infarct size, ejection fraction, age and history of prior infarction as predictors of survival. In the multivariate model, only ejection fraction (p < 0.0001), age (p = 0.008) and prior myocardial infarction (p = 0.02) remained strong predictors.

CONCLUSIONS

In these early trials of thrombolytic therapy for acute myocardial infarction, streptokinase improved early survival, but there was little long-term survival benefit. This failure to show an improvement in the 3- to 8-year survival rate may also reflect the need to study a larger group of patients or to initiate treatment earlier after symptom onset.

Heparin-induced prolongation of partial thromboplastin time after thrombolysis: relation to coronary artery patency. HART Investigators

Having previously shown in the Heparin Aspirin Reperfusion Trial that the empiric use of early intravenous heparin after recombinant tissue-type plasminogen activator (rt-PA) is an important component in the overall treatment strategy, we examine in this report the specific relation between the degree of prolongation of activated partial thromboplastin time and coronary artery patency. To evaluate the hypothesis that arterial patency after administration of rt-PA for acute myocardial infarction is sustained by effective anticoagulation, activated partial thromboplastin time of heparin recipients was determined 8 and 12 h after the start of thrombolysis. Mean activated partial thromboplastin time was higher among patients with an open infarct-related artery than in those with a closed artery (81 +/- 4 vs. 54 +/- 9 s, p less than 0.02). Only 45% of patients with values less than 45 s at both 8 and 12 h had Thrombolysis in Myocardial Infarction (TIMI) flow grade 2 or 3 in the infarct-related artery at 18 h. In contrast, 88% of patients with activated partial thromboplastin time greater than 45 s and 95% of those with values greater than 60 s had an open infarct-related artery at 18 h (p = 0.003 and 0.0006, respectively). Among patients with an initially patent infarct-related artery who underwent repeat angiography at 7 days, activated partial thromboplastin time was similar in those with a persistently patent artery and those with late reocclusion. Excessive anticoagulation did not appear to increase hemorrhagic risk except that access site-related hemorrhage was more common in patients with activated partial thromboplastin time greater than 100 s at 8 h.(ABSTRACT TRUNCATED AT 250 WORDS)

Recombinant tissue-type plasminogen activator and immediate angioplasty in acute myocardial infarction. One-year follow-up. The European Cooperative Study Group

BACKGROUND

The European Cooperative Study Group conducted two randomized trials in patients with suspected myocardial infarction to assess the effect of 100 mg single-chain recombinant tissue-type plasminogen activator (rt-PA, alteplase) on enzymatic infarct size, left ventricular function, morbidity and mortality relative to placebo (alteplase/placebo trial) and to assess the effect of immediate percutaneous transluminal coronary angioplasty (PTCA) in addition to alteplase (alteplase/PTCA trial). One-year follow-up results are reported.

METHODS AND RESULTS

In the alteplase/placebo trial, 721 patients with chest pain of less than 5 hours and extensive ST-segment elevation were allocated at random to 100 mg alteplase or placebo (double-blind) over 3 hours. In the alteplase/PTCA trial, 367 similar patients received alteplase and subsequently were allocated at random to immediate coronary angiography and angioplasty of the infarct-related vessel or control. All patients received aspirin and intravenous heparin. In the alteplase/placebo trial, mortality during the first year was reduced by 36% with alteplase (from 9.3% to 5.6%; difference, -3.7%; 95% confidence interval, -7.5% to 0.2%). Revascularization was performed more frequently after alteplase, and more patients in the alteplase group were in New York Heart Association functional class I or II. Reinfarction tended to occur more frequently after alteplase than after placebo. In the alteplase/PTCA trial, reinfarction was less common after immediate PTCA, and revascularization procedures were less frequent. However, this benefit was offset by a high rate of immediate reocclusion and early recurrent ischemia and by higher mortality at 1 year (9.3% versus 5.4%; difference, 3.9%; 95% confidence interval, -1.5% to 9.2%) in the invasive group. In a multivariate analysis of 1,043 hospital survivors, mortality after discharge was related to coronary anatomy, left ventricular function, age, and previous infarction but not to initial treatment allocation. Reinfarction after hospital discharge tended to be more common after alteplase and related to coronary anatomy.

CONCLUSIONS

Benefit from treatment with alteplase, heparin, and aspirin is not diminished at 1 year. Routine immediate PTCA does not confer additional benefit. Prognosis after hospital discharge mainly is determined by coronary anatomy and residual left ventricular function and is unrelated to initial treatment assignment.

Six-year survival after coronary thrombolysis and early revascularization for acute myocardial infarction

Six-year follow-up was conducted in a consecutive series of 192 patients receiving thrombolytic therapy for acute myocardial infarction (AMI) with ST-segment elevation. Cardiac catheterization was performed within a day, and patients with an open infarct artery routinely had early revascularization: 99 (67%) underwent coronary bypass surgery and 18 (12%) coronary angioplasty. With this treatment strategy, 6-year cardiac mortality was 14.5%, 6% (12 patients) in hospital and 9% (16 patients) for survivors of hospitalization. Multivariate analysis showed that predictors of cardiac death among survivors of hospitalization were a closed infarct artery at catheterization (p less than 0.01), diabetes (p less than 0.01) and anterior myocardial infarction (p = 0.01). A subset of 146 patients underwent radionuclide angiography before hospital discharge; for them, predictors of mortality were a closed infarct artery at catheterization (p less than 0.01), anterior wall AMI (p = 0.02), and Killip class III to IV on admission (p less than 0.06). Left ventricular ejection fraction was not a significant predictor of mortality for this subset of patients.

Thrombolytic therapy: adjuvant mechanical intervention for acute myocardial infarction

Following successful pharmacologic thrombolysis, early coronary angiography frequently shows a tight residual stenosis in the infarct-related artery at the site of recent occlusion. Approaches to the management of the residual stenosis have undergone a gradual evolution from an aggressive strategy of immediate balloon dilation to a more conservative approach. Randomized, controlled trials have indicated that immediate percutaneous transluminal coronary angioplasty (PTCA) is associated with no greater recovery in regional or global left ventricular function, and a tendency toward an increased incidence of complications, including the need for emergency coronary artery surgery and blood transfusion. The role of immediate rescue PTCA for failed thrombolysis has not been as rigorously investigated, but selected patients, including those with evidence of ongoing myocardial ischemia or hemodynamic instability, may benefit from this approach. A major source of current controversy is the value of routine coronary angiography after uncomplicated myocardial infarction. Two carefully conducted trials have indicated that a conservative strategy of clinically indicated, predischarge cardiac catheterization may be associated with an increased need for readmission and late, elective cardiac catheterization when compared with a more invasive strategy of routine coronary angiography, but that the conservative approach is not associated with an increased incidence of death or reinfarction. Provision was not made in these studies, however, for evaluating the positive economic and psychologic impact of early coronary angiography, early hospital discharge, and early return to work of patients with a favorable postinfarction prognosis. It is concluded that early mechanical revascularization following thrombolysis should be considered for ongoing myocardial ischemia, but should otherwise be deferred pending the results of predischarge functional studies. For most patients, routine coronary angiography is likely to remain an important diagnostic tool and an integral component of the management of the convalescent phase of acute myocardial infarction.

The role of thrombolytic therapy in patients with acute myocardial infarction presenting later than six hours after the onset of symptoms

Thrombolytic therapy clearly reduces mortality in patients with acute myocardial infarction, especially when initiated within 6 hours of onset of symptoms. Some studies have also suggested that thrombolytic therapy may improve survival even when initiated 6-24 hours after the onset of symptoms by mechanisms other than infarct size limitation, such as reduced expansion, reduced electrical instability, and improved healing of the infarct. However, in view of the possibility that late thrombolytic therapy may also be associated with an increased risk of cardiac rupture, the risk-benefit ratio needs to be more clearly defined. Ongoing randomized trials are expected to clarify the situation in the near future. In the meantime, efforts to initiate reperfusion as soon after the onset of myocardial infarction as possible should continue, since early treatment is still the best treatment.

Goals of thrombolytic therapy

In the past decade, mortality associated with acute myocardial infarction has been reduced to between 5% and 9% in selected groups of patients, largely due to use of early reperfusion. Thrombolytics combined with aggressive mechanical revascularization reduce the likelihood of death both during hospitalization and in the ensuing several years. Overall morbidity is also lessened, although salvage of patients with severe left ventricular dysfunction may make this difficult to demonstrate. Foremost among issues remaining unresolved is the relationship between patency of the infarct vessel and survival. Survival associated with reperfusion is limited primarily to patients with successful reperfusion. Myocardial salvage is more likely in these patients, but the correlation between myocardial salvage and mortality reduction is not determined. Late spontaneous reperfusion occurs in greater than 50% of patients who do not receive a thrombolytic; survival seems to be greater when vessels undergo spontaneous reperfusion. Only a minority of patients can be treated within the first hour after chest pain onset. It is not clear that the time window in which early reperfusion can be accomplished allows benefit to be clinically evident. Resources need to be directed toward agents to augment the rate of lysis and toward improvement of delivery. Mortality is highest in the first 24 hours after thrombolytic administration. Understanding of the underlying mechanisms may promote further reductions in mortality. Intravenous thrombolytic therapy can be given on average 2-3 hours after pain onset. If the myocardial salvage versus time curve is steepest immediately after occlusion, early administration of thrombolytics, such as by paramedics in the field, may be indicated.(ABSTRACT TRUNCATED AT 250 WORDS)

Risk stratification in survivors of acute myocardial infarction: routine cardiac catheterization and angiography is a reasonable approach in most patients

Noninvasive risk assessment in survivors of AMI can effectively subdivide patients into groups with differing risk profiles after hospital discharge, but some patients at risk for late death or recurrent AMI may be incorrectly identified; data from cardiac catheterization and angiography provide complementary and generally more powerful prognostic information. Many patients may derive particular benefit from early cardiac catheterization and angiography, including: (1) patients with AMI complicated by recurrent myocardial ischemia, congestive heart failure, and/or complex ventricular arrhythmias; (2) patients with abnormal or inconclusive results of noninvasive testing or those patients unable to perform an exercise test; (3) patients with abnormal left ventricular global systolic function and those with increased left ventricular end-systolic volume; (4) "young" patients (younger than 50 years of age?); (5) older patients (older than 65 to 70 years of age?); (6) patients with non-Q wave AMI; and (7) patients who are receiving thrombolytic therapy. Performance of early cardiac catheterization and angiography in virtually all survivors of AMI, with selective use of appropriate noninvasive tests, may provide a more efficacious means of risk assessment after AMI; if all tests are performed judiciously, the cost of such an approach need not be excessive. A combination of invasive and selected noninvasive tests probably provides optimal information. The risks to the routine performance of diagnostic cardiac catheterization and angiography in all survivors of AMI are: (1) adequate care and attention may not be paid to proper performance of the procedure(s) and to detailed and proper analyses of the data; (2) the need for additional noninvasive testing in selected patients may be ignored; and most importantly, (3) premature or unnecessary revascularization procedures may be performed subsequently. For optimal patient care, the clinician must obtain all necessary data, avoid unnecessary and repetitive tests, know the accuracy of individual tests at his or her own facility, interpret all data in proper context, and then counsel patients objectively about available management strategies. With this approach, all patients who might appropriately benefit from coronary artery revascularization will be correctly identified, and patients who are truly at very low risk (minimal residual coronary artery disease and preserved left ventricular function particularly if associated with a patent infarct-related artery) may be similarly identified and managed appropriately with elimination of unnecessary additional testing and pharmacologic therapy. Finally, whatever approach to risk stratification one chooses for an individual patient, the importance of and the need to correct and/or ameliorate risk factors for coronary artery disease must be recognized and undertaken.

A comparison between heparin and low-dose aspirin as adjunctive therapy with tissue plasminogen activator for acute myocardial infarction. Heparin-Aspirin Reperfusion Trial (HART) Investigators

BACKGROUND

We report the results of the Heparin-Aspirin Reperfusion Trial, a collaborative study comparing early intravenous heparin with oral aspirin as adjunctive treatment when recombinant tissue plasminogen activator (rt-PA) is used for coronary thrombolysis during acute myocardial infarction.

METHODS

Two hundred five patients were randomly assigned to receive either immediate and then continuous intravenous heparin (starting with a 5000-unit bolus; n = 106) or immediate and then daily oral aspirin (80 mg; n = 99) together with rt-PA (100 mg intravenously over a six-hour period) initiated within six hours of the onset of symptoms. We evaluated the patency of the infarct-related artery by angiography 7 to 24 hours after beginning rt-PA infusion, the frequency of reocclusion of the artery by repeat angiography on day 7, and ischemic or hemorrhagic complications during the hospital stay.

RESULTS

At the time of the first angiogram, 82 percent of the infarct-related arteries in the patients assigned to heparin were patent, as compared with only 52 percent in the aspirin group (P less than 0.0001). Of the initially patent vessels, 88 percent remained patent after seven days in the heparin group, as compared with 95 percent in the aspirin group (P not significant). The numbers of hemorrhagic events (18 in the heparin and 15 in the aspirin group) and recurrent ischemic events (8 in the heparin and 2 in the aspirin group) were similar in the two groups.

CONCLUSIONS

Coronary patency rates associated with rt-PA are higher with early concomitant systemic heparin treatment than with concomitant low-dose oral aspirin. This observation has important implications for clinical practice and should be considered in the design and interpretation of clinical trials involving coronary thrombolytic therapy.

Two-year outcome after angiographically documented myocardial reperfusion for acute coronary occlusion. Thrombolysis and Angioplasty Study Group

Reperfusion therapy has been clearly shown to decrease the early mortality after acute myocardial infarction, but the impact of this therapy on long-term survival has been less extensively evaluated. This study reports the extended follow-up of a large cohort of 810 patients treated with intravenous thrombolytic therapy combined, when considered necessary to maintain or augment infarct vessel patency, with mechanical reperfusion therapies. Each patient underwent coronary angiography within 2 hours of the initiation of the thrombolytic infusion. Coronary angioplasty was performed in 62% of the patients before hospital discharge and 21% underwent coronary artery bypass graft surgery. Follow-up was obtained in 96% to a mean of 18.8 months (range, 1.5 to 48 months). All-cause mortality over this period was 3.3%; 2.1% died from cardiac causes. Nonfatal reinfarction occurred in 5.1%. Although the low event rate limits the validity of statistical comparisons, the patients who survived the follow-up period tended to be younger (56 +/- 10 vs 65 +/- 7 years), to have better predischarge left ventricular function (left ventricular ejection fraction, 52 +/- 11 vs 46 +/- 13%) and to have a lower prevalence of multivessel coronary artery disease (45 vs 67%). This excellent long-term survival may, in part, reflect the exclusion of high-risk patients from enrollment in the Thrombolysis and Angioplasty in Myocardial Infarction (TAMI) studies. It may also be attributable, however, to the frequent use of combined thrombolysis and mechanical revascularization in this population.

Should thrombolytic therapy be administered in the mobile intensive care unit in patients with evolving myocardial infarction? A pilot study

The growing recognition of the importance of early thrombolysis in evolving myocardial infarction was the basis for the present study, which evaluated the effectiveness, feasibility and safety of prehospital thrombolytic therapy. In a relatively small study, 118 patients were allocated to receive either prehospital treatment with recombinant tissue-type plasminogen activator (rt-PA) in the mobile intensive care unit (group A, 74 patients) or hospital treatment (group B, 44 patients). A total of 120 mg of rt-PA was infused over a period of 6 h. All patients were fully heparinized and underwent radionuclide left ventriculography and coronary angiography during hospitalization. Although group A was treated significantly earlier than group B after onset of symptoms (94 +/- 36 versus 137 +/- 45 min, respectively; p less than 0.001), no significant differences were observed between the groups in 1) extent of myocardial necrosis, 2) global left ventricular ejection fraction at discharge, 3) patency of infarct-related artery, 4) length of hospital stay, and 5) mortality at 60 days. However, a trend to a lower incidence of congestive heart failure at hospital discharge was observed in the prehospital-treated compared with the hospital-treated group (7% versus 16%, respectively; p = NS). No major complications occurred during transportation. It is concluded that myocardial infarction can be accurately diagnosed and thrombolytic therapy initiated relatively safely during the prehospital phase by the mobile intensive care team, thus instituting a beneficial clinical trend in favor of prehospital thrombolysis.

Single photon emission computed tomography with technetium-99m hexakis 2-methoxyisobutyl isonitrile in acute myocardial infarction before and after thrombolytic treatment: assessment of salvaged myocardium and prediction of late functional recovery

Single photon emission computed tomography (SPECT) with technetium-99m hexakis 2-methoxyisobutyl isonitrile was investigated as a method to evaluate the results of intravenous thrombolytic treatment in 14 patients (11 men and 3 women) with acute myocardial infarction admitted to the coronary care unit within 4 h of the onset of symptoms. All patients received an injection of 740 MBq of the tracer before starting the thrombolytic therapy, and isonitrile tomography was performed 3 to 4 h later. The tomographic study was repeated 5 days after the acute event. The results of thrombolytic treatment were independently evaluated taking into account the clinical, electrocardiographic (ECG) and enzymatic data and the findings of left ventricular and coronary angiography. Furthermore, all patients were studied with two-dimensional echocardiography on admission, 5 days later and 1 month later. The site and extent of the perfusion defects on admission scintigraphy were consonant with the ECG and echocardiographic findings. A good correlation could be established between the 5 day scintigraphic estimate of infarct dimension and the enzymatic infarct size (r = 0.907, p less than 0.00002). The comparison between pre- and postthrombolytic treatment images enabled the identification of successful and unsuccessful reperfusion even in patients whose other noninvasive findings were inconclusive. Finally, the reduction in defect size predicted late functional improvement that was demonstrated by echocardiography performed 1 month later (r = 0.89, p less than 0.00005). The results of the study suggest the feasibility and the possible usefulness of isonitrile tomography in demonstrating the presence and size of myocardial damage and in assessing the extent of myocardial salvage after thrombolytic therapy in acute myocardial infarction.

Long-term benefit of early thrombolytic therapy in patients with acute myocardial infarction: 5 year follow-up of a trial conducted by the Interuniversity Cardiology Institute of The Netherlands

Patients (n = 533) who participated in the Interuniversity Cardiology Institute of the Netherlands Trial were followed up for 3 to 7 years. The 5 year survival rate after thrombolytic therapy with intracoronary streptokinase was 81% (269 patients) compared with 71% after conventional therapy (264 patients). The greatest improvement in survival was observed in patients with anterior infarction (81% versus 64% with thrombolytic therapy or conventional therapy, respectively), in those with heart failure on admission or a previous infarction and in those with extensive myocardial ischemia on admission. Left ventricular ejection fraction at the time of hospital discharge was better after thrombolytic therapy. In the hospital survivors, long-term outcome was related to left ventricular function at the time of discharge and, to a lesser extent, to the underlying coronary artery disease. The initial therapy (thrombolysis or conventional) was not an independent additional determinant of long-term survival when left ventricular function and coronary status at the time of hospital discharge were taken into account. Thus, the salutary effects of thrombolytic therapy appear to be the result of myocardial salvage. Reinfarction within 3 years was observed more frequently after thrombolytic therapy, particularly in patients with inferior wall infarction and those with greater than or equal to 90% stenosis of the infarct-related vessel at discharge. Coronary bypass surgery and coronary angioplasty were performed more frequently after thrombolytic therapy than in conventionally treated patients. At 5 years, approximately 40% of patients in both groups had an uneventful course without reinfarction or additional revascularization procedures. These observations demonstrate that the benefits of thrombolytic therapy are maintained throughout 5 years of follow-up.(ABSTRACT TRUNCATED AT 250 WORDS)

Emergency percutaneous transluminal coronary angioplasty during acute myocardial infarction for patients more than 70 years of age

Thirty-five patients greater than 70 years of age with acute myocardial infarction (AMI) were treated with emergency percutaneous transluminal coronary angioplasty (PTCA). Seventeen (49%) patients received previous thrombolytic therapy: streptokinase (10 patients), tissue plasminogen activator (6) and combined tissue plasminogen activator and urokinase (1). Infarct-related artery patency was achieved in 26 patients (74%) after PTCA. Total in-hospital mortality was 34%. Univariate analysis showed a higher in-hospital mortality in patients with an occluded vessel after PTCA (78%) than in those patients with a patient infarct-related artery (19%) (p = 0.003). Symptomatic coronary reocclusion occurred in 3 patients (15%) during the hospital stay. Compared with emergency PTCA in 200 consecutively treated patients less than 70 years of age, the in-hospital mortality was increased (34 vs 6%, p less than 0.001), and the primary success rate was reduced (66 vs 90%, p less than 0.001). At a mean follow-up of 28 months, there has been a 13% out-of-hospital mortality rate in the elderly patients (3 patients died). Of the 20 surviving patients, 14 are asymptomatic and 6 have class II angina. In conclusion, emergency PTCA for AMI in elderly patients is associated with a decreased success rate and a higher mortality rate. However, the in-hospital mortality rate is not dissimilar to that in elderly AMI patients treated with conventional therapy or thrombolytic therapy alone, and the postdischarge mortality rates are low.

Early recovery of left ventricular function after thrombolytic therapy for acute myocardial infarction: an important determinant of survival

Thrombolytic therapy for acute myocardial infarction reduces early mortality, but full recovery of left ventricular function after reperfusion is delayed. Therefore, the relations among reperfusion, survival and the time course of left ventricular functional recovery were examined in 226 patients treated with intracoronary streptokinase; 77% (134 patients) had sustained reperfusion and 31 patients had no reperfusion or had reocclusion by day 3. Wall motion was measured from contrast ventriculograms performed in the acute period and 3 days later in the central and peripheral infarct regions and the noninfarct region by the centerline method in 165 patients. Patients with reperfusion had better survival (p less than 0.05, mean follow-up 4.5 years) and a higher ejection fraction at 3 days (52 +/- 12 versus 46 +/- 10%, p less than 0.02) attributable to a significantly different change in peripheral infarct region function between the acute and 3 day studies (0.1 +/- 1.0 versus -0.3 +/- 0.9 SD, p less than 0.05). These early functional changes were significant in patients with anterior myocardial infarction and showed similar trends in those with inferior myocardial infarction. On Cox regression analysis, function measured at 3 days was more predictive of survival than was function measured acutely (chi square for acute ejection fraction = 11.48 versus 24.59 at 3 days). Although, as previously reported, greater than 45% of total recovery of left ventricular function occurs later, the ejection fraction achieved by day 3 is already predictive of survival. Thus, the mechanism by which successful thrombolytic therapy enhances survival is improvement of regional and global left ventricular function early after acute myocardial infarction.