Changes in left ventricular function after intracoronary streptokinase infusion in clinically evolving myocardial infarction

Analytic Review: Thrombolytic Therapy in Acute Myocardial Infarction

The salvage of myocardium in the setting of acute myocardial infarction has long been a goal of physicians involved in the care of patients with coronary artery disease. Understanding the role of thrombosis in the pathogenesis of acute myocardial infarction has led the way to an entirely new approach to the treatment of this entity. Thrombolytic therapy has now become a widely used form of treatment with encouraging results. Both intravenous and intracoronary administration of thrombolytic agents have been shown to promote recanalization of acutely occluded coronary arteries. Results of studies using the clot-specific agent, tissue plasminogen activator, intravenously have been most encouraging; successful reperfusion has been obtained in approximately 70% of patients treated. In addition, a recent large-scale trial has shown a reduction in morbidity and mortality with the early use of thrombolytic agents.

Ongoing trials should help delineate the precise role and timing of these agents as the initial form of therapy for acute myocardial infarction. Other issues that remain unresolved are the frequency of restenosis and the role of percutaneous transluminal coronary angioplasty in addition to thrombolytic therapy in the treatment of acute myocardial infarction.

Intracoronary streptokinase in acute myocardial infarction. A review

The attempt to salvage myocardium threatened by ischemia during temporary or permanent occlusion of one or more of the nutrient arteries, is based on the observation that the major determinant of survival is the extent to which myocardium has been lost through infarction. Modern clinical cardiology has therefore looked at various approaches which might limit unnecessary loss of potentially viable myocardium. These are attempts to reduce the oxygen consumption through pharmacological means, attempts at restoring the blood supply and oxygen delivery at an early stage by manipulations on the coronary arteries and interventions aimed at "protecting" cardiac cells threatened by ischemia or reperfusion. Endpoints considered to be proof of improved left ventricular function will be wall motion and ejection fraction measurements as well as reduction in death rate and other serious cardiovascular complications. Although final proof from prospective randomized studies, one of which is carried out at this institution with intracoronary streptokinase in over 300 patients, will not be available at the time of this presentation, arguments will be provided which indicate that restoration of blood supply at an early stage, preferably supported by pharmacological therapy with beta-blockade and calcium antagonists, is to be preferred inasmuch as current data indicate improved function, and in certain subsets, improved life expectancy.

Intravenous streptokinase in acute myocardial infarction (I.S.A.M.) trial: serial evaluation of left ventricular function up to 3 years after infarction estimated by radionuclide ventriculography. I.S.A.M. Study Group

The Intravenous Streptokinase in Acute Myocardial Infarction (I.S.A.M.) trial was a prospective, placebo-controlled, double-blind multicenter trial of high-dose short-term intravenous streptokinase in acute myocardial infarction administered within 6 h after the onset of symptoms. Global and regional left ventricular ejection fractions were determined by radionuclide ventriculography in a subset of 120 patients 3 days, 4 weeks, 7 months, 18 months and 3 years after acute myocardial infarction. In patients with anterior myocardial infarction, left ventricular ejection fraction was higher in the streptokinase than in the placebo group 3 days after acute infarction (49 +/- 14% vs. 40 +/- 11%, p = 0.02). This difference of about 10% units in ejection fraction persisted during the 3 year follow-up period. Among streptokinase-treated patients, regional left ventricular ejection fraction was higher within the infarct zone as well as in remote myocardium throughout the follow-up period. Among patients with inferior infarction, no significant differences between the treatment and control groups were demonstrable with respect to global and regional left ventricular ejection fraction. Thus, intravenous administration of streptokinase within 6 h after the onset of symptoms of acute myocardial infarction preserves left ventricular function over a period of greater than or equal to 3 years in patients with acute anterior myocardial infarction. It improves regional myocardial function within the infarct zone as well as in remote areas. In patients with acute inferior myocardial infarction, benefit from intravenous streptokinase is of only minor degree.

Late variation in ventricular function after myocardial infarction

To assess the possible role of variables not related to early infarct artery reperfusion in predicting late changes in ventricular function after infarction, paired early (mean 6.6 +/- 3.5 days after admission) and late (12.7 +/- 7.0 months later) cross-sectional echocardiograms from 54 infarction survivors were retrospectively reviewed. Ejection fraction was calculated from digitized biapical echocardiographic views on a graphics tablet. Changes of 0.10 or more in LVEF were correlated with 23 clinical variables. By stepwise regression analysis, Q-wave infarction and low early LVEF independently predicted late improvement in function. Early high LVEF and interval infarction were the only independent predictors of late declines in function. Overall, when patients were indexed by early left ventricular systolic function, a pronounced late "regression to the mean" was noted with initially high values tending to fall and low values to rise (r = -0.44, p less than 0.001). This effect must be accounted for in any acute intervention trial in myocardial infarction. The occurrence of Q-wave infarction does not exclude late improvement in ventricular function.

Early beneficial effect of streptokinase on left ventricular function in acute myocardial infarction

The effect of intravenous streptokinase therapy on the time course of functional recovery was investigated in a controlled study of 64 patients randomized within 3 hours after the onset of acute myocardial infarction (AMI). Contrast ventriculography was performed 1 to 4 days after AMI and repeated 5 weeks later. Wall motion was analyzed by the centerline method in the central infarct, peripheral infarct and noninfarct regions. In patients with ventriculographic data at the early catheterization, streptokinase-treated patients had less severe hypokinesia in the central infarct region than control patients (-2.9 +/- 0.9 [n = 29] vs -3.4 +/- 0.7 standard deviations below normal [n = 21], p less than 0.05). The benefit of streptokinase was more marked in the peripheral infarct region (-1.5 +/- 0.7 vs -2.1 +/- 0.6, p less than 0.001). As a result, the ejection fraction was slightly higher in treated versus control groups (46 +/- 10 vs 43 +/- 7%, respectively; difference not significant). At 5 weeks, function in the streptokinase and control groups had diverged further because of continued improvement in the streptokinase-treated patients. This study shows that streptokinase benefits left ventricular (LV) function by 1 to 4 days after AMI, earlier than previously reported. The benefit was not limited to the peripheral infarct region, where ischemia might have been less severe, but was also seen in the central infarct region. The implication is that thrombolytic therapy can improve LV function during the period of myocardial stunning, while myocardial function is still recovering.

Prediction of preserved flow to the infarct area based on admission electrocardiogram in anterior wall acute myocardial infarction

To determine whether preserved flow to the infarct area could be predicted from the admission electrocardiogram and to define the effect of preserved flow on the late results after reperfusion, 20 anterior myocardial infarction patients who were successfully reperfused were studied. Patients were divided into 3 groups: (1) no-flow group (8 patients), with an occluded infarct-related artery and no easily visible collaterals; (2) intact collateral group (6 patients); and (3) subtotal obstruction group (6 patients). From the admission electrocardiogram, the sum of ST-segment elevation (sigma ST), the sum of R-wave amplitude (sigma R) in leads V1 through V6 and the ratio of these (sigma R/sigma ST) were measured. There was no significant difference in sigma R among the 3 groups. The no-flow group had significantly lower sigma R/sigma ST and higher sigma ST than the intact collateral group or subtotal obstruction group. All patients (6 of 6) with subtotal obstruction and all except 1 patient (5 of 6) with intact collateral showed sigma R/sigma ST greater than 2.5 or sigma ST less than 2.0 mV. All patients (8 of 8) with no flow showed sigma R/sigma ST less than or equal to 2.5 and all except 1 patient with no flow (7 of 8) showed sigma ST greater than or equal to 2.0 mV. The regional wall motion was assessed by the radial method at 4 weeks. The mean percentage systolic shortening in the anterior and apical regions was significantly correlated with sigma R/sigma ST (r = 0.75, p less than 0.001) and sigma ST (r = -0.65, p less than 0.005).(ABSTRACT TRUNCATED AT 250 WORDS)

Value of immediate angioplasty after intravenous streptokinase in acute myocardial infarction

To improve reperfusion, immediate percutaneous transluminal coronary angioplasty (PTCA) was considered after intravenous streptokinase (0.75 to 1.5 million U) was administered to 98 patients with acute myocardial infarction less than 4 hours after the onset of chest pain. Thirty-four culprit arteries were occluded (group A); 42 arteries were patent with residual stenosis of more than 70% (group B). Twenty-two patients had residual stenosis of less than 70% (group C); eight of these had severe disease of the remaining vessels. Group C patients were either treated conservatively or underwent bypass surgery. Immediate PTCA was attempted in 74 patients (32 in group A, 42 in group B) and was successful in 68 (92%). Emergency bypass surgery for acute occlusion after PTCA was required in two patients. Follow-up averaged 23 months (range, 16 to 47 months). Asymptomatic occlusion recurred in three patients. Restenosis occurred in five patients: four had early restenosis (one in group A, three in group B) and one had late restenosis (group B). These arteries were successfully redilated. Late reinfarction occurred in two patients. They were treated with intravenous urokinase and repeat PTCA. Elective bypass surgery was performed in three patients because of recurrent angina. They had severe three-vessel disease as revealed by control angiography. The mortality rate was 2.7% (two patients; one in group B had early reinfarction, and one patient in group A died suddenly after 17 months). Eighty-five percent of patients treated with PTCA alone remain free of symptoms. This approach has a high success rate and low morbidity and mortality rates. Long-term results are superior to thrombolysis alone.

Comparison of regional and global left ventricular function by serial echocardiograms after reperfusion in acute myocardial infarction

Fifty patients undergoing successful reperfusion therapy (percutaneous transluminal coronary angioplasty 20, thrombolysis 10, combined 20) for acute myocardial infarction were evaluated with serial two-dimensional echocardiograms performed early (less than 24 hours, mean 8 hours) and late (greater than 3 days, mean 6 days) after presentation. Treatment occurred within 12 hours of the onset of symptoms with most patients achieving reperfusion in less than 6 hours (mean 4.7 hours) from the onset of pain. Reperfusion was demonstrated short-term by angiography in 42 of 50 patients (84%). Four patients had clinical signs of reperfusion and subsequent angiographic confirmation. An additional four patients with "stuttering" infarct courses were treated late by percutaneous transluminal coronary angioplasty. Echocardiograms were analyzed for global performance by calculation of fractional area change at the papillary muscle level and ejection fraction (biplane Simpson's rule) in 18 patients in whom this analysis could be performed. Measurements of regional function included fractional shortening at the base (n = 37), regional wall motion index (n = 50) and percent of normal functioning myocardium (n = 50). Overall there was a significant improvement in regional wall scores and percent of functioning myocardium (regional wall motion index 1.73 to 1.43, p less than 0.001 and percent of functioning myocardium 0.61 to 0.70, p less than 0.001) but only a trend toward improvement when global function was assessed by ejection fraction (0.42 to 0.48, p less than 0.14).(ABSTRACT TRUNCATED AT 250 WORDS)

The thrombolytic effects of native tissue-type plasminogen activator (AK-124) on experimental canine coronary thrombosis

To evaluate the thrombolytic effects of the native tissue-type plasminogen activator (t-PA), the authors used a thrombus model simulating clinical situations. The native t-PA (AK-124) was obtained from human-derived normal cells. Experimental canine coronary thrombosis was produced by partial constriction and endothelial denudation of the vessel. In 19 dogs, coronary occlusive thrombus was produced. Three hours after total occlusion of the coronary artery with thrombus, the authors attempted the thrombolytic therapy in 16 dogs. Histologically, three-hour thrombus was composed of a mixture of platelet aggregates, fibrin, and blood cells. They infused 0.375 mg/kg t-PA intravenously in 7 dogs and 20,000 IU/kg urokinase (UK) in 9. Coronary recanalization was achieved in 5 (71%) with t-PA infusion and 6 (67%) with UK infusion. Plasma fibrinogen levels decreased to 76% of preinfusion value in the dogs with t-PA infusion and to 34% in those with UK infusion. Coronary reocclusion occurred in 2 dogs with t-PA and 3 with UK. Thus, the native t-PA (AK-124) can provide coronary thrombolysis without severe depletion of plasma fibrinogen levels.

Variables predictive of good functional outcome following thrombolytic therapy in the Thrombolysis in Myocardial Infarction phase II (TIMI II) pilot study

Before commencing the randomized Thrombolysis in Myocardial Infarction phase II (TIMI II) study, 370 patients were administered intravenous recombinant tissue plasminogen activator (rt-PA) within 4 hours of onset of acute myocardial infarction (AMI) and assigned to 2-hour (immediate) percutaneous transluminal angioplasty (n = 33), 18- to 48-hour (delayed) angioplasty (n = 288) or no angioplasty (n = 49) in a nonrandomized, observational pilot study. Left ventricular ejection fraction at rest and during exercise was assessed by gated equilibrium radionuclide ventriculography at hospital discharge and again at 6 weeks. At hospital discharge, ejection fraction averaged 50% at rest and 56% at peak exercise. At 6-week follow-up, ejection fraction averaged 50% at rest and 53% at peak exercise. At 6-week follow-up, resting ejection fraction average 49% in the 2-hour angioplasty group, 49% in the 18- to 48-hour angioplasty group and 55% in the no-angioplasty group. Variables independently predicting "good functional outcome" at 6-week follow-up (survival with resting ejection fraction greater than equal to 50% and no decrease with exercise) in the 18- to 48-hour angioplasty group were fewer leads with ST-segment elevation greater than or equal to 0.1 mV, younger age, rapid normalization during rt-PA infusion of ST segments or dramatic relief of chest pain, absence of arrhythmias within the first 24 hours of treatment initiation, no prior infarction and not a cigarette smoker at entry. Thus, the TIMI II pilot study demonstrates that most patients with AMI of less than or equal to 4-hour duration treated with rt-PA have good ventricular function after AMI.(ABSTRACT TRUNCATED AT 250 WORDS)

Enhancement of arterial thrombolysis with native tissue type plasminogen activator by pretreatment with heparin or batroxobin: an angioscopic study

The enhancement of canine arterial thrombolysis with native tissue type plasminogen activator (nt-PA) obtained from human-derived normal cells by pretreatment with heparin or the defibrinogenating agent, batroxobin, was evaluated with angioscopy. The nt-PA, 0.25 mg/kg, was infused intravenously to lyse 1-hour-old thrombus (eight thrombosed arteries without medication, seven with nt-PA alone, seven with nt-PA and heparin, and seven with nt-PA plus batroxobin). Angioscopy provided a cross-sectional view of the vessel lumen with clear visualization of the thrombus. Thirty minutes after nt-PA infusion, the percent luminal obstruction decreased from 74 to 61 in nt-PA alone (p less than .025), from 77 to 37 in nt-PA plus heparin (p less than .005), and from 79 to 25 in nt-PA plus batroxobin (p less than .005). Fifteen minutes after drug infusion, plasma fibrinogen levels decreased to 89% of preinfusion value in nt-PA alone, to 84% in nt-PA plus heparin, and to less than 5% in nt-PA plus batroxobin. Thus rapid infusion of nt-PA alone provided slight thrombolytic effects. However, heparin and batroxobin showed marked enhancement of thrombolytic effects of nt-PA.

Daily serial evaluation of left ventricular function with equilibrium radionuclide ventriculography following thrombolysis during acute myocardial infarction

The changes in ventricular function after reperfusion by coronary thrombolysis are important when deciding about further definitive treatment necessary to ensure long-term vessel patency. The purpose of this study was to evaluate the early changes in left ventricular function after reperfusion. Left ventricular function was serially evaluated for 10 days in a group of 18 patients receiving intracoronary thrombolytic therapy for an acute myocardial infarction. Comparison of the global ventricular function in the successfully and unsuccessfully reperfused groups of patients showed significantly better function in the successful group than the unsuccessful group after the first day, which was maintained for the entire study period. Global and regional ventricular function in the successfully reperfused patients showed significant early improvement during the initial 72 h with maintenance of this improvement for the study period of 10 days. In the patients in whom reperfusion was unsuccessful, regional ventricular function showed no change, while the global function declined from day 5 to day 8 of the study period. This study then confirms the significant improvement in ventricular function after successful reperfusion. The time course pattern of the change in ventricular function indicates that the most significant improvement occurs within the first 72 h after reperfusion. These changes are similar to those previously reported in experimental animals.

Six- and twelve-month follow-up of the phase I Thrombolysis in Myocardial Infarction (TIMI) trial

The Thrombolysis in Myocardial Infarction (TIMI) trial Phase I was designed to compare the efficacy and side effects of intravenous recombinant tissue-type plasminogen activator (rt-PA) and intravenous streptokinase (SK) in patients with acute myocardial infarction (AMI). As previously reported, rt-PA led to a reperfusion rate of 62% of totally occluded coronary arteries compared with 31% for SK (p less than 0.001). This study was not designed to determine if intravenous thrombolytic therapy decreases the mortality of AMI; however, the findings in these patients after 1 year of follow-up do permit certain insights into the impact of early reperfusion and reocclusion on the clinical course of patients with AMI. The mortality rate at 6 and 12 months was not significantly different in patients treated with rt-PA compared with SK (7.7% and 10.5% rt-PA vs 9.5% and 11.6% for SK). The frequency of recurrent AMI, coronary artery bypass grafting (CABG) and percutaneous transluminal coronary angioplasty (PTCA) was similar in the 2 treatment groups. There was no significant difference in 6- and 12-month mortality or in the rate of recurrent AMI in patients who received thrombolytic therapy before compared with after 4 hours of the onset of AMI symptoms. When the results were analyzed on the basis of the patency of the infarct-related artery, irrespective of thrombolytic agent used, for those patients with patent arteries 90 minutes after the initiation of therapy, there was a trend toward a lower 6-month (5.6% vs 12.5%) and 12-month mortality (8.1% vs 14.8%) (p = 0.07).(ABSTRACT TRUNCATED AT 250 WORDS)

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.

Limitation of myocardial infarction by early infusion of recombinant tissue-type plasminogen activator

In a double-blind randomized trial involving five Sydney hospitals and the city ambulance paramedical service, 145 patients with a first evolving myocardial infarction and with onset of pain less than 2.5 (mean 1.9 +/- 0.5 [SD]) hr previously were allocated to intravenous infusion of 100 mg recombinant tissue-type plasminogen activator (rt-PA) or placebo over 3 hr. The groups at entry were similar. At assessment 21 days later, left ventricular ejection fraction measured both by contrast and radionuclide ventriculography was higher in the rt-PA compared with the placebo group (61 +/- 13%, n = 64, vs 54 +/- 14%, n = 62, contrast, 2p = .006; 52 +/- 13%, n = 66, vs 48 +/- 13%, n = 62 isotope, 2p = .08). This indicates limitation of myocardial infarction by rt-PA.

Prognostic significance of angina pectoris before first acute myocardial infarction

To delineate the clinical significance and prognostic importance of a history of chronic or new onset angina pectoris before acute myocardial infarction (AMI), 732 consecutive patients admitted for a first AMI were studied and divided into 3 groups. Two hundred patients (27%) had chronic angina before AMI (greater than 1 month); 247 patients (34%) had new onset angina before AMI (less than 1 month) and the 285 remaining patients (39%) never had angina before AMI. All clinical characteristics were similar in the group of patients with chronic angina and in the group of patients with new onset angina, including in-hospital mortality (10 vs 9%) and 3-year post-hospital mortality (16 vs 16%). Compared to the 285 patients without angina, the 447 patients with angina before AMI were older, more likely to be women, and had a higher frequency of anterior AMI and early post-infarction angina. Both groups had a similar in-hospital mortality (10 vs 8%, not significant), but patients with angina had a higher 3-year post-hospital mortality (16 vs 7%, p less than 0.001). In the group of patients with angina before AMI who were discharged from the hospital, the comparison of nonsurvivors and survivors showed that the patients who died were older, presented more frequently with a non-Q-wave myocardial infarct and more often had left ventricular failure and complete bundle branch block during hospital stay. Chronic and new onset angina before AMI have the same clinical characteristics and deleterious long-term prognostic significance.

Preventive effects of batroxobin on experimental canine coronary thrombosis

The thrombolytic effects of urokinase (UK) and preventive effects of batroxobin, heparin, and aspirin on the recurrence of thrombosis in the coronary artery were studied in 118 anesthetized dogs with severe endothelial denudation and luminal stenosis of the coronary artery. Occlusive thrombi developed in 68 (58%) preparations (dogs), accompanied by a decrease of coronary blood flow and pressure, an electrocardiographic ST elevation, and epicardial cyanosis. An intravenous infusion of 20,000 IU/kg of UK reopened the occluded coronary artery in all 32 preparations with 1-h-old thrombi, in 6 (86%) of 7 preparations with 2-h-old thrombi, and in 5 (83%) of 6 preparations with 3-h-old thrombi. However, recanalization was not observed in preparations with thrombi more than 4-h-old. Occlusion recurred within 6 h after recanalization in 2 (18%) of 18 preparations pretreated with batroxobin (1-2 BU/kg) (p less than .005 vs. control UK group), in 1 (14%) of 7 preparations administered a continuous infusion of 30 U/kg per h of heparin (p less than .05 vs. control UK group), in 4 (57%) of 7 preparations pretreated with 2 mg/kg of aspirin, and in 7 (64%) of 11 preparations not pretreated (control UK group). Complete prevention was observed only in the group administered 2 BU/kg of batroxobin. Histologically, these thrombi closely simulated clinical arterial thrombi. Myocardial hemorrhage and contraction band necrosis were observed in the reperfused hearts. In conclusion, experimental canine coronary thrombi more than 4-h-old were resistant to thrombolytic therapy, and batroxobin and heparin were effective in the prevention of coronary reocclusion.

Thrombolytic therapy in acute myocardial infarction: Part I

Thrombolytic therapy with pharmacologic agents is an exciting approach to the treatment of myocardial infarction. The results of several clinical studies indicate that perfusion can be restored with intravenous therapy and may be associated with a reduction in infarct size and improved left ventricular function. In a trial involving more than 11,000 patients, thrombolytic therapy reduced acute and long term mortality. Pharmacologic thrombolysis, however, is not without problems. When administered intravenously, the agents currently available, streptokinase and urokinase, are associated with a relatively low recanalization rate as well as a risk of adverse effects, most commonly a systemic lytic state and risk of bleeding complications. Although intracoronary administration is associated with a higher rate of recanalization, the need for cardiac catheterization limits its applicability and results in a delay in the initiation of thrombolytic therapy (which diminishes salvage of myocardium). The trials assessing the existing agents have shown that time is a critical variable in the success of thrombolytic therapy. This had led investigators to focus more attention on intravenous agents that can be administered rapidly. The newer agents now under investigation, acylated streptokinase and single-chain urokinase, may represent improvements of currently available products and may offer potentially increased benefits. A fibrinogen-sparing agent, such as t-PA, in addition to being highly effective, may offer advantages through minimizing the systemic lytic effect. Additional randomized, controlled clinical trials currently are underway to determine the effect on mortality of this "fibrinolytic" therapy as part of a total treatment regimen. The current status of our knowledge concerning thrombolytic therapy in acute myocardial infarction can be summarized as follows: 1. Transmural (that is, Q wave) myocardial infarction usually is caused by an obstructing coronary thrombus. 2. The thrombus can be lysed with intravenous therapy in the majority of cases, particularly with newer, well-tolerated fibrin-specific agents. 3. There is considerable evidence suggesting that reperfusion reduces the acute morbidity and mortality when therapy is administered successfully within the initial 3 to 4 hours (and possibly up to 6 hours) after onset of symptoms. 4. Data on long term prognosis after thrombolysis are very encouraging, although limited. 5. Conventional agents lead to significant fibrinogen depletion and therefore an increased risk of bleeding; the new fibrin-selected agents cause less fibrinogen degradation and may reduce the risk of hemorrhagic complications.(ABSTRACT TRUNCATED AT 400 WORDS)

Factors that predict improvement in left ventricular ejection fraction after coronary angioplasty for acute myocardial infarction

Acute and follow-up angiograms were analyzed in 75 patients with acute myocardial infarction treated with emergency coronary angioplasty to determine factors that might predict improvement in left ventricular ejection fraction. Ejection fraction improved 8.4 +/- 8.2% in 60 patients who maintained patent infarct vessels at follow-up angiography, compared with -4.1 +/- 6.0% in 15 patients who developed reocclusion (p less than .001). In patients with patent infarct vessels, univariate analysis revealed the following significant predictors of improvement in ejection fraction: initial ejection fraction (r = -.38, p less than .003) subtotal vs total stenosis (12.9 +/- 9.3% vs 6.9 +/- 7.3%, p less than .02), infarct vessel (left anterior descending 11.0 +/- 8.4%, right 6.8 +/- 6.4%, circumflex 2.6 +/- 7.5%, p less than .02), and time to follow-up study (less than or equal to 15 days vs greater than 15 days) (4.8 +/- 5.8% vs 9.8 +/- 8.6%, p less than .03). Reperfusion time (less than or equal to 2 hr vs greater than 2 hr) predicted improvement when subtotal stenoses and stuttering infarctions were excluded (10.6 +/- 7.0% vs 4.9 +/- 6.9, p less than .03). Multivariate analysis showed initial ejection fraction and subtotal vs total stenosis to be independent predictors. Patients with anterior infarctions, low initial ejection fractions, and subtotal stenoses or reperfusion times less than or equal to 2 hr are likely to benefit most from coronary angioplasty for acute myocardial infarction.

Paradoxic elevation of fibrinopeptide A after streptokinase: evidence for continued thrombosis despite intense fibrinolysis

Elevated levels of fibrinopeptide A, a marker of thrombin activity associated with acute myocardial infarction, have been found to decrease after administration of streptokinase when reperfusion occurs. In contrast, in patients without reperfusion and those with reocclusion after streptokinase therapy, fibrinopeptide A remains elevated. In the present study early serial measurements of fibrinopeptide A were used to further characterize this paradoxic increase in thrombin activity after streptokinase and to characterize its response to heparin. In 19 patients with acute myocardial infarction fibrinopeptide A was elevated to 82.3 +/- 43.5 ng/ml (mean +/- SE) before therapy. Thirty minutes after the initiation of streptokinase, fibrinopeptide A increased to 300.1 +/- 117.4 ng/ml (p less than 0.01), consistent with extensive thrombin activity. Fibrinopeptide A remained elevated until 15 minutes after a heparin bolus injection when levels decreased to 15% of the poststreptokinase value (49.2 +/- 13.3 ng/ml) (p less than 0.001). These data document a prompt paradoxic increase in thrombin activity after administration of streptokinase that may be responsible for failure of therapy in some patients.

Early reperfusion therapy improves left ventricular function after acute inferior myocardial infarction associated with right coronary artery disease

Quantitative global and regional ventriculographic analysis was performed acutely and 1 week later in 46 patients undergoing reperfusion procedures within 6 hours of acute inferior myocardial infarction due to right coronary artery disease. While serial improvement in global left ventricular ejection fraction was not demonstrated for the group, infarct zone regional wall motion did improve (-2.7 +/- 0.9 vs -2.3 +/- 1.4 SD/chord, p less than 0.007). Serial improvement in global ejection fraction was demonstrated in the subgroup of patients treated within 2 hours of symptom onset (55 +/- 10 vs 62 +/- 10%; n = 5; p less than 0.03). Infarct zone regional wall motion improved serially only in the subgroup of patients treated within 3 hours of symptom onset (-2.4 +/- 1.1 vs -1.3 +/- 1.7 SD/chord; n = 11; p less than 0.007). Patients with initially patent arteries had a higher ejection fraction on follow-up catheterization than did those with initially occluded vessels (61 +/- 11 vs 55 +/- 7%; p less than 0.02), and patients with patent arteries at follow-up had a higher ejection fraction than did those whose arteries were occluded (60 +/- 9 vs 48 +/- 4%; p less than 0.0001). We conclude that significant improvement in global and regional left ventricular function in patients with inferior myocardial infarction is possible when reperfusion therapy is begun early or when arterial patency is achieved.

Value of immediate coronary angioplasty following intracoronary thrombolysis in acute myocardial infarction

A total of 533 patients with acute myocardial infarction of less than 4-h duration were enrolled in the multicenter randomized trial of intracoronary thrombolysis compared to conventional treatment. In two of the five participating centers, an additional coronary angioplasty immediately after thrombolysis was attempted in 46 patients. According to the treatment allocation and early and late patency of the infarct related vessel, patients were subdivided into three groups: conventionally treated (group A); successful coronary angioplasty following thrombolysis with persistent patent infarct related vessel (group B); and late patency of the infarct related vessel postthrombolytic therapy without angioplasty (group C). The highest global ejection fractions were observed in group B (54% +/- 10%) and group C (55% +/- 13%), while the lowest ejection fraction was found in group A (47% +/- 14%). The sequential changes in global ejection fraction from the acute to the chronic stage was + 4% (p = 0.05) in group B, while no significant changes could be demonstrated in group C. Furthermore, in the group successfully treated by angioplasty, the improvement in global ejection fraction was more pronounced and persisted up to three months after the intervention. This was supported by analysis of regional myocardial function of the infarct zone (+ 16% improvement, p = 0.01). The long-term clinical follow-up (median 24 months) of the patients successfully treated by combined procedure of thrombolysis and angioplasty (group B) was most favourable with a lower incidence of re-infarction (6%), and late coronary bypass surgery (13%) and/or (re)-percutaneous transluminal coronary angioplasty (3%) was performed less frequently. These results suggest that reperfusion may need to be supplemented by additional revascularization procedures in order to optimize the changes of obtaining full functional recovery and so to improve the prognosis.

Experimental canine arterial thrombus formation and thrombolysis: a fiberoptic study

We produced arterial thrombi that simulated the clinical condition in canine iliac arteries by endothelial denudation and partial occlusion. The processes of thrombus formation and thrombolysis were examined by vascular fiberscope. Laminar mural thrombi developed in all 21 preparations 10 minutes after blood reperfusion, with stenosis formation. Over 50% luminal obstruction with thrombi occurred in 10 preparations 30 minutes after inducing stenosis. Total occlusion with thrombi occurred in four preparation (31%) at 1 hour, and in all nine at 3 hours after inducing stenosis. Usually, red thrombus at the denudated region grew in size distal to the sited of stenosis. Histologically, thrombi of less than 1 hour duration consisted of a loose fibrin network and those of over 3 hours' duration consisted of a dense fibrin network. Infusion of 144,000 IU of urokinase (UK) reduced the size of thrombi less than 1 hour old during fiberoptic observation. However, UK infusion of similar dose failed to recanalize two of four preparations with 3-hour-old thrombi. In conclusion, arterial thrombi that closely simulate those observed clinically can be made by endothelial denudation and partial occlusion, and the vascular fiberscope provides a useful method for analysis of thrombosis and thrombolysis.

Quantitation of fragment X formation during thrombolytic therapy with streptokinase and tissue plasminogen activator

We have determined the extent of fragment X formation during thrombolytic therapy by integration over time of the plasma fibrinopeptide B beta 1-42 concentration. This peptide is quantitatively released when fragment X is formed by plasmin action on fibrinogen or fibrin I. In response to streptokinase (SK) and rt-PA, 264 +/- 54 and 95 +/- 12 mg/dl respectively of fibrinogen was converted to fragment X. By immunoblotting, fragment X was demonstrated as early as 5 min after SK and 30 min after rt-PA, and was still evident 24 h after treatment. Patients treated with SK showed extensive further plasmin degradation of fragment X to fragments Y and D. Thus fragment X concentrations tend to be more similar in the two groups than would be expected from the extent of fibrinogen breakdown. Fragment X forms clots, but these have lower tensile strength and are more susceptible to further plasmin lysis than clots of fibrin. Thus the similar bleeding observed in the two treatment groups might be a reflection of their similar plasma fragment X concentrations.

Recurrent early ischemic events after thrombolysis for acute myocardial infarction

Myocardium salvaged by early thrombolysis and then perfused through a residual stenosis may be at risk for ischemic events. To investigate this possibility, the short-term (2-week) clinical course of 81 consecutive patients managed within a randomized intracoronary thrombolysis trial was reviewed. All patients underwent coronary angiography within 5 hours of symptoms of acute myocardial infarction and were stratified into the following 3 outcome groups: patients with initially subtotal occlusion (subtotal group, n = 17), those with initial total occlusion and infarct artery reperfusion (reperfused group, n = 24) and those with continued infarct artery occlusion (occluded group, n = 40). Recurrent ischemic events were defined as spontaneous typical angina, provokable angina on predischarge exercise testing, and reinfarction. Eleven of 17 patients (65%) in the subtotal and 11 of 23 patients (48%) in the reperfused groups had an ischemic event (difference not significant). In contrast, 4 of 37 patients (11%) with occlusion had an ischemic event (p less than 0.01 compared with patients in the subtotal or reperfused groups). Four patients were excluded because of early (within 72 hours) elective coronary bypass surgery or death from pump failure. To eliminate the impact of multivessel coronary artery disease (CAD), 39 patients with 1-vessel CAD were analyzed separately. Five of 9 patients (56%) in the subtotal group, 3 of 10 (30%) in the reperfused group and only 2 of 20 (10%) in the occluded group had an ischemic event. These observations suggest the need for a more definitive revascularization strategy for acute myocardial infarction.

The effect of intravenous thrombolytic therapy on left ventricular function: a report on tissue-type plasminogen activator and streptokinase from the Thrombolysis in Myocardial Infarction (TIMI Phase I) trial

In Phase I of the NHLBI trial of Thrombolysis in Myocardial Infarction (TIMI), 290 patients admitted within 7 hr after onset of acute infarction were randomly assigned to intravenous treatment with either streptokinase (SK) or recombinant tissue-type plasminogen activator (rt-PA). Left ventricular function was measured from contrast ventriculograms in 145 patients with both pretreatment and predischarge studies analyzable. Regional wall motion in the infarct site was measured by the centerline method and expressed in units of standard deviations (SDs) from the mean motion in 52 normal subjects. Patients treated with rt-PA (n = 77) achieved a significantly higher reperfusion rate after 90 min of treatment. Perfusion of the infarct-related artery improved from visual grade 0 or 1 (total occlusion or penetration without perfusion) to grade 2 or 3 (partial or full reperfusion) in 62% receiving rt-PA vs 31% receiving SK (n = 68) (p less than .001). However, the ejection fraction did not change significantly from before treatment to before discharge in either treatment group (+0.7 +/- 6.7% vs +1.0 +/- 8.3%, respectively). A small but significant increase in regional wall motion was observed in each of the two groups (+0.4 +/- 0.8 vs +0.3 +/- 0.8 SD/chord, respectively; each p less than .001 compared with baseline). This was countered by declines in the hyperkinesis of the noninfarct region (-0.3 +/- 1.0 SD/chord [p = .01] compared with baseline and -0.2 +/- 1.0 SD/chord [p = .23], respectively). Analysis of the combined groups revealed that the ejection fraction increased only in patients who achieved reperfusion by 90 min after onset of therapy or who had subtotal occlusions initially. There was greater recovery of left ventricular function in patients who achieved reperfusion earlier vs later than 4 hr after symptom onset and in patients with vs without some collateral circulation to the infarct-related artery.

Determinants of improved left ventricular function after thrombolytic therapy in acute myocardial infarction

Many studies have been performed to evaluate the efficacy of thrombolytic therapy in achieving reperfusion, salvaging myocardium and enhancing survival. This review discusses the concordance between the results of these clinical studies and the observations made in experimental animals of the effect of reperfusion on the recovery of left ventricular function. The evaluation of functional recovery is affected by the timing of the measurement and the sensitivity of the method for detecting regional abnormalities. In addition, the underlying coronary anatomy also determines outcome, so that infarct location, collateral circulation and the degree of coronary obstruction merit consideration. Two factors are of paramount importance in determining the amount of myocardium salvaged, the recovery of left ventricular function and the reduction in mortality. These factors are: the time delay until reperfusion is achieved and the adequacy of the coronary reflow. The close agreement between studies measuring the effect of reperfusion on left ventricular function and studies with mortality as the end point provides indirect evidence that enhancement of survival in patients treated with thrombolytic agents is mediated by recovery of ventricular function.

Early intervention in acute myocardial infarction: significance for myocardial salvage of immediate intravenous streptokinase therapy followed by coronary angioplasty

Sixteen patients with acute myocardial infarction underwent treatment with streptokinase up to 3 hours after the onset of chest pain. Nine patients (group I) received streptokinase within 1 hour of the onset of pain, and seven patients (group II) received it within 2 to 3 hours. All underwent multigated radionuclide ventriculography after streptokinase therapy and 1 week later. Percutaneous transluminal coronary angioplasty of the infarct artery was performed within 24 hours in all patients. An effort-limited treadmill stress test was performed before discharge. There was no mortality or serious complication. Mean peak total creatine kinase was 521 +/- 289 mU/ml in group I, and 1,614 +/- 709 mU/ml in group II (p less than 0.05). The mean initial left ventricular ejection fraction was 47 +/- 11% in group I and 37 +/- 10% in group II. After early angioplasty (within 24 hours) and at 1 week recovery, left ventricular ejection fraction increased to 53 +/- 9% in group I (p less than 0.05) and to 40 +/- 7% in group II (p = NS). Seven of the nine patients in group I had normal radionuclide ventriculograms at discharge compared with none of the seven patients in group II. Thrombolytic therapy administered less than 1 hour after the onset of symptoms of acute myocardial infarction followed by angioplasty of the infarct artery results in preservation of left ventricular function, whereas therapy given after 2 hours has only a limited effect.

Effect of spontaneous reperfusion on myocardial infarct size

The effect of perfusion of the infarct artery on myocardial infarct size was studied in 39 patients who had not received interventive therapy. At predischarge coronary angiography, 19 patients had subtotal and 20 total occlusion of the infarct artery. The early ST-segment elevation recorded on a 12-lead electrocardiogram was used as an index of the amount of initially jeopardized myocardium. Infarct size was estimated by peak serum creatine kinase and, at discharge, by a QRS score, sigma Q and sigma R on a 12-lead electrocardiogram, and by radionuclide global and infarct segment left ventricular ejection fraction. Despite a similar degree of initial ischemia (sigma ST), infarct size was smaller in the 11 patients with anterior infarction and subtotal occlusion than in the 9 patients with anterior infarction and total occlusion when measured by peak serum creatine kinase (2114 +/- 1192 U/l vs. 3653 +/- 1059 U/l, p less than 0.02), QRS score (5.0 +/- 2.7 vs. 9.6 +/- 3.5, p less than 0.01), sigma Q (3.25 +/- 2.74 mV vs. 5.92 +/- 3.56 mV, p less than 0.10), sigma R (4.36 +/- 1.25 mV vs. 2.16 +/- 0.91 mV, p less than 0.001), global left ventricular ejection fraction (45.0 +/- 12.2% vs. 33.4 +/- 6.7%, p less than 0.05), and infarct segment ejection fraction (40.4 +/- 8.2% vs. 30.3 +/- 5.4%, p less than 0.05). In the inferior infarct patients, both the degree of initial ischemia and final infarct size were similar in the 8 patients with subtotal and in the 11 patients with total occlusion.(ABSTRACT TRUNCATED AT 250 WORDS)

[Echocardiographic evaluation of intravenous streptokinase in myocardial infarction in the acute phase]

The effects of intravenous fibrinolysis on left ventricular function in acute myocardial infarction were investigated by two-dimensional echocardiography in patients aged less than 70 for whom fibrinolysis was not contra-indicated and who were admitted less than 6 hours after the onset of a first myocardial infarction without heart failure. The 12 patients thus recruited were male; their mean age was 55 years and the infarct was anterior in 6 cases and posterior in 6 cases. Streptokinase was administered first by bolus intravenous injection (250,000 IU over 20 min), then by intravenous infusion (100,000 IU over 12 hours); this was followed by heparin. No other medication was given, except for intravenous lidocaine and oral nifedipine. Two-dimensional echocardiography was performed after 24 hours and on the 21st day, using the apical, two-cavities projection. The ejection fraction and the percentage of shortening in 16 ventricular segments (8 in the anterior and 8 in the inferior territories) were evaluated from systolic and diastolic ventricular contours. Ventricular angiography and coronary arteriography were performed concomitantly with echocardiography. No significant improvement in ejection fraction was observed. On both day 1 and day 21, the kinetics of the lower segments was improved and that of the anterior segments was distinctly reduced in inferior infarcts. The kinetics of all segments, irrespective of their territory, was significantly improved in anterior infarcts.

Which patients benefit most from early thrombolytic therapy with intracoronary streptokinase?

The effect of thrombolysis in acute myocardial infarction on enzymatic infarct size, left ventricular function, and early mortality was studied in subsets of patients in a randomized trial. Early thrombolytic therapy with intracoronary streptokinase (152 patients) or with intracoronary streptokinase preceded by intravenous streptokinase (117 patients) was compared with conventional treatment (264 patients). All 533 patients were admitted to the coronary care unit within 4 hr after onset of symptoms indicative of acute myocardial infarction. Four hundred eighty-eight patients were eligible for this detailed analysis, and 245 of these were allocated to thrombolytic therapy and 243 to conventional treatment. Early angiographic examinations were performed in 212 patients allocated to thrombolytic therapy. Patency of the infarct-related artery was achieved in 181 patients (85%). Enzymatic infarct size, as measured from cumulative alpha-hydroxybutyrate dehydrogenase release, was smaller in patients allocated to thrombolytic therapy (median 760 vs 1170 U/liter in control patients, p = .0001). Left ventricular ejection fraction measured by radionuclide angiography before discharge from the hospital was higher after thrombolytic therapy (median 50% vs 43% in control patients, p = .0001). Three month mortality was lower in patients allocated to thrombolytic therapy (6% vs 14% in the control group, p = .006). With the use of multivariate regression analysis, infarct size limitation, improvement in left ventricular ejection fraction, and three month mortality were predicted by sum of the ST segment elevation, time from onset of symptoms to admission, and Killip class at admission. Thrombolysis was most effective in patients admitted within 2 hr after onset of symptoms and in patients with a sum of ST segment elevation of 1.2 mV or more. On the other hand, no beneficial effects of streptokinase on enzymatic infarct size, left ventricular function, or mortality were observed in the subset of patients with a sum of ST segment elevation of less than 1.2 mV who were admitted between 2 and 4 hr after onset of symptoms.

Effects of early intracoronary streptokinase on infarct size estimated from cumulative enzyme release and on enzyme release rate: a randomized trial of 533 patients with acute myocardial infarction

The effects of early intracoronary streptokinase (SK) on enzymatic infarct size and rate of enzyme release were studied in a randomized multicenter trial. A total of 533 patients with acute myocardial infarction (AMI) were allocated to either the SK treatment group (n = 269) or the conventional (control) treatment group (n = 264). Enzymatic infarct size was represented by the cumulative quantity of alpha-hydroxybutyrate dehydrogenase (HBDH) released by the heart per liter of plasma in the first 72 hours. Rate of enzyme release was represented by the ratio of HBDH quantities released in 24 hours and 72 hours. On an "intention to treat" basis, the SK group had a smaller (by 30%; p = 0.0001) median enzymatic infarct size and a higher (by 35%; p = 0.0001) median rate of enzyme release than the control group. Limitation of infarct size was less apparent in patients treated with intracoronary SK only (25%) than in patients treated with intravenous plus intracoronary SK (34%). Compared to the control group, the enzyme release rate in patients treated with intracoronary SK only was slightly less (34%) than that in patients treated with intravenous plus intracoronary SK (38%). Patients with a patent infarct-related coronary artery at acute angiography had a median infarct size which was 55% (p = 0.0001) smaller than the median infarct size of the control group, and the median rate of enzyme release was 38% (p = 0.001) higher than the median release rate of the control group. Patients with successful recanalization during intracoronary SK infusion had a median infarct size which was 31% (p = 0.002) smaller than the median infarct size of the control group and a median rate of enzyme release which was 42% (p = 0.0001) higher than the median release rate of the control group. Patients with persistent coronary occlusion in spite of thrombolytic therapy had a median infarct size which was 11% (NS) higher than the median infarct size of the control group, although the median rate of enzyme release was still 23% (p = 0.02) higher than the median release rate of the control group. It is concluded that thrombolysis in the early phase of AMI limits infarct size and that intracoronary SK treatment itself accelerates the process of enzyme release from infarcted myocardium, independent of the angiographic result.

Methodology and results of intravenous thrombolysis in acute myocardial infarction

For the vast majority of patients with acute myocardial infarction, intravenous thrombolysis is at present the only therapeutic approach aimed at early reperfusion of the ischemic myocardium. Rapid recanalization of the infarct-related coronary artery is achieved in at least 50-60% of the patients by short-term high-dose infusions of streptokinase or urokinase with a low risk of bleeding. A substantial reduction of infarct size, however, can be expected in only a minority of patients, mostly in those who are treated very early. The effects of intravenous thrombolysis on early and late mortality from acute myocardial infarction are still equivocal; more conclusive data may be expected from ongoing randomized trials.

Thrombolytic therapy followed by early revascularization for acute myocardial infarction

During a 24-month period, 192 patients with acute myocardial infarction were treated with intracoronary or intravenous streptokinase (SK). In 147 patients (77%) an open infarct artery was demonstrated by coronary angiography; 117 of these 147 patients were judged to have viable myocardium supplied by a critically narrowed coronary artery and underwent revascularization 3 +/- 2 days after SK therapy. In-hospital mortality was 6% (12 of 192). The mortality rate over the subsequent 20 +/- 7 months of follow-up was lower for those in whom SK therapy was successful (1 of 137, 0.7%) than in those in whom it was not (6 of 43, 14%) (p less than 0.001), and tended to be lower for those treated with intravenous (2 of 111, 2%) rather than intracoronary SK (5 of 69, 7%, p = 0.11). Reinfarction occurred in 3% of the 180 survivors of hospitalization, angina pectoris in 11% and congestive heart failure in 7%. Clinical outcome was similar for patients treated with intravenous and intracoronary SK and for patients treated in community hospitals and the referral center.

A randomized controlled trial of intravenous streptokinase in evolving acute myocardial infarction

To determine the efficacy of intravenous streptokinase in acute myocardial infarction, 52 patients were randomized to intravenous streptokinase or control groups. Time from onset of infarction to randomization was similar in the streptokinase group and control group, 4.9 +/- 2.1 hours vs 5.4 +/- 2.4 hours, respectively. The 28 streptokinase patients received an intravenous infusion of 700,000 units of streptokinase followed by full-dose anticoagulation. The 24 control patients received normal saline solution followed by full-dose anticoagulation. Of 28 streptokinase patients, 12 (43%) had noninvasive evidence of reperfusion by early peaking of serum creatine kinase (peak creatine kinase less than 16 hours after onset of infarction) vs 3 of 24 control patients (13%), p less than 0.02. Two streptokinase patients (7%) had reperfusion arrhythmias during streptokinase infusion. One streptokinase patient (4%) and two control patients (8%) died during hospitalization. At angiography (16 +/- 5 days after infarction) 22 of 26 streptokinase patients (85%) had a patent infarct-related coronary artery compared to 8 of 20 control patients (40%), p less than 0.01. Comparison of radionuclide left ventricular ejection fraction assessed acutely (28 +/- 10 hours after infarction) with left ventricular ejection fraction at hospital discharge (15 +/- 3 days after infarction) showed no significant improvement in either the streptokinase or control group, 0% and +1%, respectively. At follow-up 13 +/- 7 months after infarction, total mortality rate was similar in the streptokinase group and control group, 17.8% (5 of 28 streptokinase patients) and 20.8% (5 of 24 control patients), respectively.(ABSTRACT TRUNCATED AT 250 WORDS)

Combined thrombolytic therapy and coronary angioplasty for acute myocardial infarction

From September, 1983, to August, 1984, combined thrombolytic therapy and percutaneous transluminal coronary angioplasty was used to treat 22 cases of acute myocardial infarction. Initial coronary angiograms showed total obstruction in 13 and severe stenosis in 9. Intracoronary infusion of urokinase reopened 7 of 13 totally occluded lesions but left a residual severe stenosis. Coronary angioplasty opened all of the remaining totally obstructed lesions and decreased the stenosis in 14 of 16 stenosed lesions. These procedures were performed 0.5 to 24 hours after the onset of chest pain. Lesions were not successfully dilated in two patients, because of arterial dissection in one and rethrombus formation in the other. One patient died from progressive hypotension beginning during the procedure, despite technically successful coronary angioplasty. Eighteen of the 20 successfully dilated lesions were patent at repeat angiography performed 1 to 3 weeks later. One successfully dilated lesion occluded 8 days after the procedure and was redilated by a larger sized balloon.

Percutaneous transluminal coronary angioplasty in evolving acute myocardial infarction

In 29 patients with evolving acute myocardial infarction, acute reperfusion of the infarct-related coronary artery was attempted using percutaneous transluminal coronary angioplasty (PTCA). Before PTCA, angiography showed 23 totally occluded and 6 severely stenotic infarct-related coronary arteries. PTCA was initially successful in 25 of 29 patients (86%). Reocclusion occurred in 4 patients within 12 hours after successful PTCA and was associated with new electrocardiographic changes or recurrence of symptoms. In 17 patients the infarct-related coronary artery remained patent at early follow-up; late stenosis occurred in 4 patients. Recurrence of stenosis was accompanied by development of angina. No clinical or angiographic features distinguished those with ultimate vessel patency, occlusion or recurrence of stenosis. On follow-up, ventricular function appeared better preserved or improved in those with a patent infarct-related coronary artery than in those with an occluded infarct-related coronary artery. Further studies are warranted to compare PTCA and streptokinase as primary reperfusion modalities in evolving acute myocardial infarction.

Acute coronary reocclusion after thrombolysis with recombinant human tissue-type plasminogen activator: prevention by a maintenance infusion

Twenty-nine patients with acute myocardial infarction were treated with recombinant human tissue-type plasminogen activator (rt-PA). The incidence of acute coronary reocclusion and its prevention by a maintenance infusion of rt-PA were studied. Intravenous rt-PA was given at a rate of 0.4 to 0.75 mg/kg over 60 to 120 min after angiographic documentation of complete coronary occlusion. Reperfusion was accomplished within 1 hr in 24 of 29 patients (83%) and was associated with a decrease of the plasma fibrinogen level by 20%. In a first group of 13 patients, 11 of whom were successfully reperfused, prevention of reocclusion was attempted with heparin anticoagulation. However, acute reocclusion within 1 hr after cessation of rt-PA was demonstrated angiographically in five of these patients (45%). Quantitative angiographic analysis indicated that acute reocclusion only occurred in patients with 80% or greater residual stenosis. In patients with less than 80% residual stenosis, heparin anticoagulation was sufficient to maintain patency during the hospital stay in four of five patients. In a second group of patients (n = 16), 13 of whom underwent reperfusion with intravenous rt-PA, seven demonstrated a residual stenosis of 80% or greater. These patients were given heparin and, in addition, 10 mg of rt-PA per hour for 4 hr. None developed acute angiographic reocclusion or clinical signs of reocclusion during the hospital stay. Repeat angiography at 10 to 14 days confirmed persistent patency in six of the seven patients. The maintenance infusion resulted in only a moderate additional drop in fibrinogen, while a steady-state plasma rt-PA level of 750 +/- 250 ng/ml was maintained.(ABSTRACT TRUNCATED AT 250 WORDS)

Collateral flow in patients with acute myocardial infarction

To assess the change in angiographically visualized collaterals in evolving acute myocardial infarction (AMI), coronary arteriograms from 53 patients obtained 6.2 +/- 0.2 hours after onset of AMI symptoms were compared with follow-up angiograms obtained 14 +/- 1 days later. Collaterals were graded according to intensity score and percent of distal infarct-related artery visualized. Collateral intensity score and the percent of distal infarct vessel visualized by collaterals at baseline were low, and there was a significant increase in both values at follow-up angiography. The group of 20 patients with occluded infarct vessels at follow-up study accounted for these increases. In 33 patients with patent infarct vessels at repeat angiography, collateral intensity score and percent of segment visualized were unchanged. Among the patients with occluded infarct vessels at baseline and subsequent improvement in left ventricular (LV) ejection fraction (EF), baseline collateral score and percent of segment visualized were significantly greater than in patients in whom LVEF did not improve. Thus, in patients with evolving AMI, (1) angiographically visible collaterals are not extensive within the early hours of AMI, (2) the extent of collaterals on follow-up angiography may not be representative of that on the day of AMI, (3) collaterals are considerably more common 2 weeks after AMI, especially in patients with occluded infarct arteries during follow-up, and (4) collaterals present at the time of AMI are associated with improved LVEF at 2 weeks.