A randomized trial of intravenous and intracoronary streptokinase in patients with acute 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.

Effect of very early intravenous streptokinase infusion in patients with evolving myocardial infarction

The effect of very early infusion of 1.5 X 10(6) U of streptokinase intravenously was studied in 29 patients with nitroglycerin-resistant chest pain and ST-segment elevation. Infarct size was estimated from maximal LD1 isoenzyme levels, and the diagnosis confirmed by CK-MB determination. Thrombolytic therapy was started within 1 hour of pain onset in 11 patients (group A), between 1 and 2 hours in 10 (group B), and later than 2 hours in eight patients (group C). Marked differences appeared between the groups. Thus, three patients in group A and one patient in group B did not develop infarction, all had critical LAD stenoses. Three patients in group C died in shock without bleeding. Further, the average maximal LD1 values in the 22 patients who survived their infarction differed significantly between the groups, and were 12.6, 19.1 and 36.2 mu kat/l in groups A, B and C, respectively. In conclusion, very early intravenous streptokinase infusion probably reduces myocardial necrosis, and possible prevents infarction in some patients.

Thrombolytic therapy use for acute myocardial infarction and outcome in Qatar

OBJECTIVE

Data on the outcome of patients treated with thrombolytic therapy in the Arab world is scarce. The main objective of this study is to study the 7-day morbidity and mortality rate and the rate of use of thrombolytic therapy in patients presenting with acute myocardial infarction treated with thrombolytic therapy in the Middle East.

METHODS

We conducted a retrospective analysis of prospectively collected data for all patients who were admitted to Coronary Care Unit in Cardiology Department in Hamad Medical during the period (1991-2001). Patients were divided into two groups in relation to ethnicity whether they received thrombolysis or not. In each group, the number of patients, age at the time of admission, gender, cardiovascular risk profile, therapy and outcome in regard of in-hospital complication and 7-day death as primary end point were analyzed.

RESULTS

Of the total 5388 patients admitted with acute myocardial infarction during the 10-year period, 66.3% (3567) with STE MI were found, 61.4% (2190) of them received thrombolytic therapy while 38.6% (1377) were not eligible for thrombolytic therapy. The remaining 33.7% (1821) were admitted with non-STE MI. In consideration of ethnic variation, patients with STE MI eligible for thrombolytic therapy, 29.6% (1598) were Qataris and 70.4% (3792) were non-Qataris. Thrombolytic therapy was administered to 25.9% (414) of Qatari patients and 51.3% (1947) of non-Qataris. The mortality rate of Qatari patients who received thrombolytic therapy was 9.2% (38) vs. 19.5% (231) who did not receive thrombolytic therapy (p<0.001). In non-Qatari patients, the mortality rate was 5.2% (102) for those who received thrombolytic therapy, while it was 8.6% (159) for those with no thrombolytic therapy (p<0.001). When compared to male patients, female patients with thrombolytic therapy had higher mortality rates (in both Qataris and non-Qataris) (20.5% vs. 6.1%; p value<0.001 and 16.1% vs. 9.4%; p<0.001, respectively), there were no significant differences between the ethnic groups in regard to in-hospital complications. Patients treated with thrombolytic therapy had lower incidence of in-hospital complication regarding acute heart failure, post-myocardial angina, heart block and arrhythmia. Thrombolytic therapy reduced mortality rate in acute myocardial infarction by 69%. Logistic regression analysis had shown that arrhythmia, acute heart failure, heart block, cardiogenic shock, diabetes mellitus and stroke were independent predictors of increased mortality. Thrombolysis was used in 61.4%, which is still underutilized when compared to a few available studies in the Gulf area, and to other studies in the developed world.

CONCLUSION

In the current study, use of thrombolysis in acute myocardial infarction was associated with significant decrease in in-hospital mortality and morbidity. Mortality rate was higher in the Qatari nationals when compared to non-Qataris. Reperfusion therapy may be underutilized in the developing world. Increased use of reperfusion therapy would result in reduced mortality rate. Global measures to encourage the use of reperfusion therapy including patients' education, and strategies to improve the health care system are needed.

23Na MRI combined with contrast-enhanced1H MRI provides in vivo characterization of infarct healing

Although (23)Na MRI has been shown to delineate acute myocardial infarction (MI), the time course of in vivo (23)Na MRI during infarct healing remains unknown. In this study (23)Na MRI was combined with contrast-enhanced (CE) (1)H MRI to noninvasively characterize infarct healing in vivo. Serial in vivo 3D (23)Na MRI and (1)H MRI were performed for up to 9 weeks postinfarction in 10 dogs. Radioactive microspheres were used to measure myocardial perfusion, and Hematoxylin-Eosin (H&E) and Masson's trichrome (MT) staining were used to assess interstitial cell infiltrate and collagen content. In vivo (23)Na MRI accurately delineated infarct size up to day 5 postinfarction in comparison with (1)H MRI (8.9% +/- 8.1% vs. 8.6% +/- 7.9% on day 1 postinfarction, P = NS; and 6.3% +/- 6.2% vs. 6.2% +/- 6.2% on days 4/5 postinfarction, P = NS). The in vivo (23)Na MRI signal intensity, expressed as the signal intensity ratio of infarcted tissue vs. noninfarcted tissue (MI/R) peaked on day 1 of infarction (2.04 +/- 0.23) but decreased significantly to 1.27 at 9 weeks postinfarction (P < 0.05) due to granulation tissue infiltrate and collagen deposition. To confirm the MI/R decrease during scar formation ex vivo, we performed (23)Na MRI in 12 rats on day 3 post-MI (N = 5) and after 6 weeks (N = 7). H&E and Picrosirius Red staining confirmed granulation tissue infiltrate on day 3 and scar formation after 6 weeks. MI/R decreased significantly from 1.91 +/- 0.45 on day 3 post-MI to 1.3 +/- 0.09 after 6 weeks. Thus, in vivo (23)Na MRI accurately delineates infarct size up to day 5 postinfarction. In vivo (23)Na MRI signal intensity decreases during infarct healing as a result of the underlying infarct healing process.

[Non-invasive methods for evaluating reperfusion in acute myocardial infarct: enzymes and MIBI-SPECT cardiac gammagraphy]

INTRODUCTION

Several studies point out the importance of what is called rescue angioplasty or fibrinolysis when thrombolysis has been ineffective in acute myocardial infarction. Therefore, it is necessary to make use of new non-invasive methods to asses reperfusion and to safely establish that such a treatment has not been effective.

PATIENTS AND METHOD

We present a work which is based on the assessment of patients with acute myocardial infarction treated with or without fibrinolysis. After determining cardiac enzymatic profiles of creatine kinase and MB isoform (time course, peak, appearance rate constant time-activity: K1). With cardiac imaging gammagraphies 99mTc-isonitrile-single-photon emission computed tomography pre and post treatment after to calculating myocardium at risk, salvage and relationship.

RESULTS

In patients treated with fibrinolysis, the salvage myocardium was higher (8.3% vs 3.0%; p < 0.05). Considering that an improvement in perfusion defect (salvaged myocardium/myocardium at risk) higher than 30% can be viewed as an effective reperfusion, we can see that the percentage in the group treated with fibrinolysis being 45.8%, and the percentage in the group under conventional treatment being just 6.7%. Patients with acute myocardial infarction treated with fibrinolysis show much shorter start of rise-peak time and pain-peak time, all this with very significant differences for the creatine kinase (p < 0.0001) as well as for the MB (p < 0.001). Patients with reperfusion show a rapid increase in activity enzymatic, as demonstrated by the pain-peak time variable and the appearance rate constant time-activity (K1), with very significant differences in the latter (p < 0.0001). In relation with gammagraphy, values of K1 higher or equal to 0.19 for the creatine kinase and 0.14 for the MB isoform, achieved a sensibility of 83% and 91%, and a specificity of 85% and 80% respectively, to asses reperfusion.

CONCLUSION

We think that cardiac imaging gammagraphy with isonitriles as well as as determination of the appearance rate enzymatic constant time-activity, can be useful in monitoring treatment with fibrinolysis in infarction patients. New studies are needed to assess these same aspects, with a lesser number of enzymatic determinations.

Basic and clinical aspects of myocardial stunning

Although the pathogenesis of myocardial stunning has not been definitively established, the two major hypotheses are that it is caused by the generation of oxygen-derived free radicals on reperfusion and by a loss of sensitivity of contractile filaments to calcium. These hypotheses are not mutually exclusive and are likely to represent different facets of the same pathophysiological cascade. For example, a burst of free radical generation after reperfusion could alter contractile filaments in a manner that renders them less responsive to calcium. Increased free radical formation could also cause cellular calcium overload, which would damage the contractile apparatus of the myocytes. There is now considerable evidence that myocardial stunning occurs clinically in various situations in which the heart is exposed to transient ischemia, such as unstable angina, acute myocardial infarction with early reperfusion, exercise-induced ischemia, cardiac surgery, and cardiac transplantation. Recognition of myocardial stunning is clinically important and may impact patient treatment. Although no ideal diagnostic technique for myocardial stunning has yet been developed, thallium-201 scintigraphy or dobutamine echocardiography are available and can be useful to identify viable myocardium with reversible wall motion abnormalities. An intriguing possibility is that so-called chronic hibernation may in fact be the result of repetitive episodes of stunning, which have a cumulative effect and cause protracted postischemic left ventricular dysfunction. A better understanding of myocardial stunning will expand our knowledge of the pathophysiology of myocardial ischemia and provide a rationale for developing new therapeutic strategies designed to prevent postischemic dysfunction.

Thrombolytic therapy does not change the release ratios of enzymatic and non-enzymatic myocardial marker proteins

Measurements of cardiac marker proteins in plasma from patients with acute myocardial infarction (AMI) have become important in the evaluation of recanalization therapy. The validity of this approach has however been questioned, because it was claimed that coronary reperfusion may increase the recovery in plasma of cardiac enzymes, such as creatine kinase (CK). In the present study, possible effects of thrombolytic therapy on the release of enzymatic and nonenzymatic marker proteins were investigated. Activities of CK and lactate dehydrogenase (LDH), and concentrations of myoglobin (Mb) and fatty acid-binding protein (FABP) were determined in serial plasma samples obtained from 50 patients with confirmed AMI, of whom 36 received thrombolytic therapy, and 14 did not. Treatment delay was 2.8+/-1.6 (mean+/-SD) h, and hospital delay in untreated patients was 2.7+/-1.8 h. Average infarct size, expressed in gram-equivalents of heart muscle per litre of plasma (g-eq/l), varied between 5.5 and 7.2 g-eq/l for the four marker proteins in patients treated with thrombolytic therapy, and between 4.6 and 6.4 g-eq/l in untreated patients, with a tendency to larger infarct sizes for Mb and FABP than for CK and LDH. Thrombolytic therapy, although significantly accelerating protein release rates, did not influence the release ratios. These results indicate that thrombolytic therapy has no significant effects on the recovery of cardiac marker proteins in plasma.

Prevalence of spontaneous reperfusion and associated myocardial salvage in patients with acute myocardial infarction

This study sought to determine the prevalence of spontaneous reperfusion of an infarct-related artery (IRA) and associated myocardial salvage in the absence of thrombolysis or angioplasty. Twenty-one patients with acute myocardial infarction received only heparin and aspirin. At a median of 18 hours after presentation, 12 patients (57%) had angiographic patency of the IRA. Technetium-99m sestamibi was injected acutely on presentation and again at hospital discharge. Acute and final perfusion defect sizes were measured. Their difference, myocardial salvage, was calculated along with salvage index (myocardial salvage/acute defect). Comparing patients with a patent versus occluded IRA, myocardium at risk was similar (16% +/- 12% vs 12% +/- 9% left ventricle, p = NS); however, myocardial salvage (9% +/- 9% vs -2% +/- 7% left ventricle, p = 0.01), and salvage index (0.62 +/- 0.37 vs 0.19 +/- 0.33, p = 0.01) were greater in patients with spontaneous reperfusion. Resolution of chest pain was greater in patients with a patent IRA (100% vs 55%, p = 0.003). Spontaneous reperfusion of the IRA occurs frequently in patients with acute myocardial infarction and is associated with significant myocardial salvage.

Cumulative troponin T release after acute myocardial infarction. Influence of reperfusion

For troponin T a characteristic biphasic change in the plasma time-concentration curve has been described, especially in patients with early reperfusion after thrombolytic therapy. As troponin T is bound to myofibrillar structures, treatment strategy or treatment outcome could influence the cumulative plasma release of this protein in a different way compared to the cumulative release of free cytoplasmic cardiac enzymes. The present study is the first study comparing the total quantity of troponin T released by the heart during the first 168 hours after acute myocardial infarction, both in patients treated with thrombolytic therapy (n = 16) and in patients not treated with thrombolytic therapy (n = 7). On the basis of clinical symptoms and coronary arteriogram within 24 hours, the patients treated with thrombolytic therapy were divided into two groups, reperfused (n = 9) and non-reperfused (n = 7). In the patients not treated with thrombolytic therapy, absence of spontaneous early reperfusion was judged only from clinical symptoms. Cumulative troponin T release into plasma was compared to the cumulative release of the cytoplasmic cardiac enzymes creatine kinase (EC 2.7.3.2) and hydroxybutyrate dehydrogenase (EC 1.1.1.27). Cumulative release, i. e., infarct size, was calculated using a two-compartment model for circulating proteins. Mean tissue contents, per gram wet weight, of 156 U/g for hydroxybutyrate dehydrogenase, 2.163 U/g for creatine kinase and 234 microg/g for troponin T, were used to express infarct size in gram-equivalents of healthy myocardium per litre plasma (g-eq/l). Release rates were represented by the ratio of cumulative quantities released in 10 hours and 72 hours for creatine kinase and hydroxybutyrate dehydrogenase and in 10 hours and 168 hours for troponin T.

CONCLUSIONS

- Plasma time-concentration curves and release rates of troponin T in patients treated with thrombolytic therapy showing reperfusion differ significantly from those of patients not treated with thrombolytic therapy, showing no reperfusion. - Creatine kinase and hydroxybutyrate dehydrogenase release is completed within 72-100 hours in all patients, whereas troponin T release still continues after 168 hours. - Cumulative troponin T release at 168 hours is only a fraction (around 8%) of cumulative cytoplasmic enzyme release and the percentage released is not influenced by the treatment strategy or outcome, i. e., vessel patency. - Although troponin T release is only a fraction of the cumulative enzyme release (infarct size) there is a highly significant correlation between both, independent of the treatment strategy or treatment outcome.

TIMI grade 3 flow and reocclusion after intravenous thrombolytic therapy: a pooled analysis

Early and sustained flow of grade 3 according to Thrombolysis in Myocardial infarction (TIMI) criteria and reocclusion rates are the key measures that define the physiologic efficacy of thrombolytic agents in the treatment of acute myocardial infarction. We performed a systematic overview of angiographic studies after intravenous thrombolysis with accelerated and standard-dose tissue-plasminogen activator (TPA), anisoylated plasminogen streptokinase activator complex (APSAC), and streptokinase. There were 5475 angiographic observations from 15 studies for TIMI flow analysis and 3147 angiographic observations from 27 studies for reocclusion. At 60 and 90 minutes, the rates of TIMI grade 3 flow were 57.1% and 63.2%, respectively, with accelerated TPA, 39.5% and 50.2% with standard-dose TPA, 40.2% and 50.1% with APSAC, and 31.5% at 90 minutes with streptokinase. Overall reocclusion with standard-dose TPA was 11.8% versus 6.0% for accelerated TPA, 4.2% for streptokinase, and 3.0% for APSAC. Although the incidence of TIMI grade 3 flow increased over time with all thrombolytic regimens, decreased patency was observed at 180 minutes with accelerated TPA. Still, accelerated TPA is the most effective agent to establish early (90-minute) TIMI grade 3 flow.

Cardiac troponin T release into plasma after acute myocardial infarction: only fractional recovery compared with enzymes

After acute myocardial infarction (AMI) cardiac enzymes and proteins are released into plasma and are used as biochemical markers of cardiac muscle injury. We studied the completeness of the release of troponin T, a cardiac protein that is largely bound to myofibrillar structures and compared it with the release of cytoplasmic cardiac enzymes in 22 patients with AMI, who were treated with thrombolytic therapy. Creatine kinase (CK; EC 2.7.3.2), hydroxybutyrate dehydrogenase (HBDH), lactate dehydrogenase (LDH; EC 1.1.1.27) and troponin T were assayed serially in plasma samples obtained frequently and for at least 168 h after the start of thrombolytic therapy. Cumulative release of enzymes and troponin T in plasma were calculated by using a two-compartment model for circulating proteins. In order to express the cumulative plasma releases in gram equivalent (g-eq) healthy myocardium per litre plasma (infarct size), we determined HBDH, LDH and total troponin T contents per gram net weight of tissue in 17 human hearts obtained post-mortem from patients who died from non-cardiac causes. Mean (SD) tissue contents per gram wet weight of, respectively, 156 +/- 25 U/g, 385 +/- 59 U/g and 234 +/- 65 micrograms/g were found. For the cardiac enzymes CK, HBDH and LDH the mean (SEM, n = 22) total release over 72 h, was, respectively, 5.9 +/- 1.5, 5.9 +/- 1.6 and 6.1 +/- 1.7 g-eq/L. There was no further increase after 72 h and the differences between enzymes were not significant. The mean (SEM) cumulative troponin T release, expressed in gram equivalents of myocardium per litre of plasma was only 0.30 +/- 0.09 g-eq/L after 72 h and 0.51 +/- 0.61 g-eq/L after 168 h. After 72 h total recovery of troponin T in g-eq/L was only 5% and after 168 h only 8.5% of the total recovery of cytoplasmic cardiac enzymes after 72 h. Cumulative troponin T release after 72 h and after 168 h correlates well with infarct size, estimated from cumulative cytoplasmic enzyme release. However, quantification of infarct size should preferably be performed from plasma release curves of cytoplasmic cardiac enzymes or proteins in order to prevent underestimation of infarct size, caused by incomplete release of the non-cytoplasmic proteins.

Q wave and Non-Q wave myocardial infarction after thrombolysis

OBJECTIVES

We studied the clinical outcome of Q wave and non-Q wave infarction after thrombolytic therapy.

BACKGROUND

Controversy exists over the clinical significance of Q waves after thrombolysis.

METHODS

We studied postthrombolytic angiographic results and short- and long-term clinical outcome in 150 patients with acute myocardial infarction classified as Q wave and non-Q wave on the 24-h and discharge electrocardiograms (ECGs). The results from the two groups were then compared.

RESULTS

Eighty percent of patients had a Q wave and 20% a non-Q wave infarction on the 24-h ECG. The latter patients had lower peak creatine kinase (CK) levels (p < 0.001), but the two groups did not differ significantly otherwise. In 18 patients with a Q wave infarction on the 24-h ECG, pathologic Q waves disappeared. However, in seven patients with a non-Q wave infarction on the 24-h ECG, pathologic Q waves appeared throughout the hospital period. Q wave regression was associated with lower peak CK levels (p < 0.001) and an improvement in left ventricular ejection fraction (p < 0.01). Thus, only 72% of patients had a Q wave and 28% a non-Q wave infarction on the discharge ECG. Patients with a non-Q wave infarction on the discharge ECG had higher patency of the infarct-related artery (p < 0.04), lower mean peak CK levels (p < 0.0001), a higher ejection fraction (p = 0.001) and a lower incidence of heart failure (p = 0.06) than patients with a Q wave infarction on the discharge ECG. Although the 2-year incidence of reinfarction and revascularization was higher in patients with a non-Q wave infarction on the discharge ECG (p < 0.05), 2-year mortality was lower (p = 0.08).

CONCLUSIONS

Although the early postthrombolytic distinction between Q wave and non-Q wave infarction conveys no significant information, during the hospital period, non-Q wave infarction is associated with a smaller infarct area, improved left ventricular function and lower mortality.

A pooled analysis of coronary arterial patency and left ventricular function after intravenous thrombolysis for acute myocardial infarction

Individual studies of patency rates and left ventricular (LV) function after thrombolysis have generally been limited by small numbers of observations, wide confidence intervals, and limited numbers of time points. To obtain a more reliable estimate of patterns of patency and LV ejection fraction, a systemic overview of angiographic studies was performed after intravenous thrombolytic therapy. A total of 14,124 angiographic observations from 58 studies evaluating patency after no thrombolytic agent, streptokinase, standard dose tissue-type plasminogen activator (t-PA), accelerated dose t-PA, or anistreplase (anisoylated plasminogen streptokinase activator complex [APSAC]) were included. At 60 and 90 minutes, streptokinase had the lowest patency rates of 48% and 51%, respectively, standard dose t-PA and APSAC had similar intermediate rates of approximately 60% and 70%, and accelerated t-PA had the highest patency rates of 74% and 84%. By 2 to 3 hours and longer, the patency rates were similar for the various regimens. Reocclusion rates in studies including 1,172 patients randomized to t-PA versus a nonfibrin-specific agent were higher after t-PA (13.4% vs 8.0%, p = 0.002). Ten studies enrolling 4,088 patients treated with thrombolytic therapy versus control demonstrated a modest improvement in mean LV ejection fraction in the thrombolytic group at each of the times after thrombolytic therapy: hour 4, day 1, day 4, day 7 to 10, and day 10 to 28 after thrombolysis. By 4 days, mean ejection fraction was 53% versus 47% (thrombolytic vs control therapy, p < 0.01); by 10 to 28 days it was 54.1% and 51.5%, respectively.(ABSTRACT TRUNCATED AT 250 WORDS)

Pre-dosing antibody levels and efficacy of thrombolytic drugs containing streptokinase

OBJECTIVE

To evaluate the influence of pretreatment streptokinase resistance titre and the concentration of IgG antibodies to streptokinase on the efficacy of thrombolytic drugs containing streptokinase in restoring coronary patency in acute myocardial infarction.

DESIGN

Comparative observational study.

SETTING

City general hospital.

PATIENTS

One hundred and twenty four previously unexposed patients presenting within six hours of onset of acute myocardial infarction.

INTERVENTIONS

Streptokinase, 1.5 MIU as intravenous infusion over 60 minutes (60 patients), or anistreplase, 30 units as intravenous injection over five minutes (64 patients).

MAIN OUTCOME MEASURES

Pretreatment streptokinase resistance titre and concentration of IgG antibodies to streptokinase were measured in 96 and 124 patients respectively and coronary patency assessed angiographically at 90 minutes and 24 hours.

RESULTS

Pretreatment streptokinase resistance titre and concentrations of IgG antibodies to streptokinase were low and skewed towards higher values. Those patients with coronary occlusion at 24 hours had a significantly higher median streptokinase resistance titre (100 v 50 streptokinase IU ml-1, P = 0.02). There were trends towards a higher streptokinase resistance titre in those patients with coronary occlusion at 90 minutes (50 v 20 streptokinase IU ml-1, P = 0.06) and higher concentrations of IgG antibodies to streptokinase in those with coronary occlusion at both 90 minutes and 24 hours (1.53 v 0.925, P = 0.03; 1.65 v 1.04 micrograms streptokinase binding ml-1, P = 0.06). Coronary patency rates were similar in the two treatment groups.

CONCLUSIONS

In the range measured in previously unexposed patients the streptokinase resistance titre has a small, but significant, negative influence on the efficacy of streptokinase and anistreplase. This effect should be considered if retreatment with streptokinase or anistreplase is proposed.

Early T wave inversion after thrombolytic therapy predicts better coronary perfusion: clinical and angiographic study

OBJECTIVES

This study was undertaken to test the hypothesis that early inversion of T waves after thrombolytic therapy for acute myocardial infarction predicts patency of the infarct-related artery with high Thrombolysis in Myocardial Infarction (TIMI) perfusion flow and better in-hospital outcome.

BACKGROUND

Although numerous studies have demonstrated a strong association between early resolution of ST segment elevation after acute myocardial infarction and successful thrombolysis, little is known about early changes in T waves after thrombolytic therapy.

METHODS

Ninety-four consecutive patients with acute myocardial infarction treated with recombinant tissue-type plasminogen activator (rt-PA) were studied with admission and predischarge radionuclide ventriculography and with coronary angiography within 72 h of admission. Patient stratification was based on the presence or absence of early (within 24 h) T wave inversion.

RESULTS

Early T wave inversion was associated with a higher patency rate of the infarct-related artery (90% vs. 65%, p < 0.02) and less severe residual stenosis ([mean +/- SD] 73 +/- 27 vs. 83 +/- 22, p = 0.06), and when only TIMI perfusion grade 3 was considered, the difference was even greater (77% vs. 41%, p < 0.001). Patients with early inversion of T waves had a lower peak creatine kinase value ([mean +/- SD] 678 +/- 480 vs. 1,076 +/- 620, p < 0.01), and although a similar percent of patients with and without early T wave inversion had a normal ejection fraction (> or = 55%) on admission, a higher percent of patients with early inversion had a normal ejection fraction at hospital discharge (71% vs. 44%, p < 0.03). Early T wave inversion anticipated a more benign in-hospital clinical course with a lower incidence of adverse cardiac events (10% vs. 33%, p < 0.02).

CONCLUSIONS

Early inversion of T waves in patients with acute myocardial infarction treated with thrombolytic therapy suggests patency of the infarct-related artery, better perfusion grade and left ventricular function and a more benign in-hospital course.

Left ventricular dysfunction due to stunning and hibernation in patients

Left ventricular dysfunction is in most cases the consequence of myocardial ischemia. It may occur transiently during an attack of angina and usually it is reversible. It may persist over hours or even days in patients after an episode of ischemia followed by reperfusion, leading to the so-called condition of stunning. In patients with persistent limitation of coronary flow, left ventricular dysfunction may be present over months and years, or indefinitely in subjects with fibrosis, scar formation, and remodeling after myocardial infarction. However, chronic left ventricular dysfunction does not mean permanent or irreversible cell damage. Hypoperfused myocytes can remain viable but akinetic. This type of dysfunction has been called hibernating myocardium. The dysfunction due to hibernation can be partially or completely restored to normal by reperfusion. It is, therefore, important to clinically recognize a hibernating myocardium. In the present article we evaluate stunning and hibernation with respect to clinical decision making and, when possible, we refer to our ongoing clinical experience.

Frequency of inclusion of patients with cardiogenic shock in trials of thrombolytic therapy

The purpose of this study was to determine the extent to which patients with cardiogenic shock have participated in trials of thrombolytic therapy, to examine factors associated with their exclusion from these trials, and to summarize data on the efficacy of thrombolysis in these patients. Previous publications were searched for all randomized, controlled studies involving the use of thrombolytic medications used in the treatment of acute myocardial infarction. Data were abstracted for year of trial publication, performance location, sample size, maximal allowable delay between symptom onset and treatment, and exclusion criteria. Of the 94 trials included in the analysis, 22% included patients with cardiogenic shock, 37% excluded them, and the remainder contained no information on their inclusion or exclusion. Only 2 trials provided data on the efficacy of thrombolytic therapy in patients with cardiogenic shock. Multivariate analysis revealed that studies conducted exclusively in the U.S. were significantly more likely to exclude patients in cardiogenic shock than those conducted outside of the U.S., as were studies that excluded patients with a previous myocardial infarction, studies published more recently, and smaller trials. Patients with cardiogenic shock have frequently been excluded from clinical trials of thrombolytic agents. As a result, data on the efficacy of thrombolytic agents in these patients is extremely limited.

Detection of acute myocardial infarction with digital image processing of two-dimensional echocardiograms

We have previously described the ability of a computer-based image digitizing system to assess early textural changes in acute canine myocardial infarction. To determine whether this technique could be applied to human beings, we studied 12 patients with a first acute transmural myocardial infarction and five normal subjects. Two-dimensional echocardiograms were performed on days 1 and 8 in normal subjects and on days 1 (day of admission), 2, 3, 5, and 14 in the patient population. All recording parameters on the echocardiography machine were kept identical for serial studies. The mean period between hospitalization and first echocardiogram was 11.1 hours (range 4 to 20 hours). End-diastolic frames from the two-dimensional echocardiographic images were digitized and displayed on a monitor. The mean pixel intensity (MPI) (+/- SD) in the region of asynergy (area of myocardial infarction) and a normal area were determined. In normal volunteers, no significant change in MPI was noted between anteroseptal and lateral areas on two separate two-dimensional echocardiographic studies, which were performed 7 days apart (anteroseptal: MPI, 21.6 +/- 1.1 vs 21.8 +/- 0.4, p = not significant) and (lateral: MPI, 21.5 +/- 1.2 vs 21.4 +/- 1.4, p = not significant). In patients with myocardial infarction, a significant increase in MPI was noted on the first day of myocardial infarction between normal and infarcted myocardium (20.4 +/- 2.0 vs 24.3 +/- 2.3, p less than 0.05) and progressively increased thereafter until day 14 (20.5 +/- 1.7 vs 31.9 +/- 3.7, p less than 0.05).(ABSTRACT TRUNCATED AT 250 WORDS)

Aggregation of washed platelets by plasminogen and plasminogen activators is mediated by plasmin and is inhibited by a synthetic peptide disulfide

Plasmin is known to activate platelets. However, it is not clear whether plasminogen activators as used in thrombolytic therapy can aggregate platelets and how this relates to the ability of each activator to convert plasminogen to plasmin. Urokinase (UK) and streptokinase (SK) activated purified plasminogen (2 microM) in a concentration-dependent manner. The rates of aggregation of washed platelets by the above plasminogen activators and plasminogen were similar to the extent of activation of plasminogen to plasmin in the absence of platelets. UK or SK (0.2 microM) and plasminogen (2 microM) aggregated platelets modified by an ADP affinity analog, 5'-p-fluorosulfonylbenzoyladenosine (FSBA), and cleaved aggregin, a putative ADP receptor, in [3H]FSBA-modified platelets. These results suggest that the effect was independent of ADP. In contrast, incubation mixtures containing only plasminogen (2 microM) and single chain tissue plasminogen activator (sc-tPA) (less than or equal to 0.12 microM) neither activated the zymogen to an appreciable extent nor aggregated platelets. But, in the presence of fibrin(ogen) fragments (tPA-stimulator), a mixture of plasminogen and sc-tPA aggregated unmodified and FSBA-modified platelets, and cleaved aggregin. The results imply that platelets, in the presence of t-PA stimulator, potentiate activation of plasminogen to plasmin by t-PA, as previously reported. P1, Phe-Gln-Val-Val-Cys-(NpyS)-Gly-NH2, (NpyS = 3-nitro-2-thiopyridine), a synthetic hexapeptide capable of binding to and inhibiting calpain, has been shown to inhibit platelet aggregation induced by purified plasmin. P1 inhibited platelet aggregation by plasminogen and any of the three plasminogen activators. Our results show that at plasma concentrations of plasminogen and at levels of UK and SK attained after infusion of these agents during thrombolysis, these mixtures can cause maximum aggregation which may contribute to reocclusion and stenosis following infarct therapy. P1 can effectively inhibit platelet aggregation under such conditions.

Intracranial hemorrhage in association with thrombolytic therapy: incidence and clinical predictive factors

In a period of 18 months, 2,469 patients with acute myocardial infarction treated with a thrombolytic agent were prospectively registered in 61 hospitals. Most patients (73%) were treated with streptokinase. Intracranial hemorrhage was observed in 24 patients, corresponding to an incidence rate of 1% (95% confidence interval 0.6% to 1.3%). The median time interval between the start of thrombolytic therapy and the first clinical signs of intracranial bleeding was 16 h (range 3 to 36). In total, 16 (66%) of the 24 patients died as a result of cerebral hematoma. To determine clinical predictive factors, a case-control study was conducted. For every patient with intracranial hemorrhage, two control patients who received thrombolytic therapy because of acute infarction in the same hospital and in the same period were selected. Detailed clinical characteristics of 22 of the 24 patients as well as of 7 other patients with documented intracerebral bleeding from the European Cooperative Study Group and of 2 patients who sustained intracranial hemorrhage outside the registry period were compared with 62 control patients. The results of multivariate logistic regression analysis indicate that patients taking an oral anticoagulant before admission, patients with a body weight less than 70 kg and those greater than 65 years old are at higher risk for intracranial hemorrhage during thrombolytic therapy.

Overview of patency as an end point of thrombolytic therapy

Underlying the use of thrombolytic therapy is the hypothesis that reestablishment and maintenance of coronary blood flow (coronary patency) are the primary mechanisms of therapeutic benefit in patients with acute myocardial infarction. Early achievement and maintenance of adequate coronary blood flow (patency) in the infarct-related artery are the primary goals of thrombolytic therapy. One third of patients may achieve spontaneous patency within a few days following acute myocardial infarction. When antithrombotic therapy (i.e., heparin) is administered, this rate increases to greater than 50%, but patency is achieved only gradually and mortality reductions comparable to thrombolytic therapy are not achieved. After administration of a thrombolytic agent, early (90-minute) patency rates are greater with alteplase or anistreplase than with streptokinase. However, patency rates for alteplase decline by 10-30% if intravenous heparin is not given concurrently. When patency is assessed greater than 24 hours following thrombolytic therapy, no significant difference exists among the agents. A single angiographic observation of the artery at 90 minutes, although useful, may be inadequate to distinguish among the beneficial clinical effects of different thrombolytic regimens. The overall reperfusion or patency profile is probably a better basis for assessing relative benefits. Intravenous thrombolytic regimens that are increasingly effective in rapidly achieving and maintaining coronary patency are now available and in further development.

Effects of early thrombolytic therapy (anistreplase versus streptokinase) on enzymatic and electrocardiographic infarct size in acute myocardial infarction. TEAM-2 Investigators

The effects of thrombolytic therapy on enzymatic and electrocardiographic indexes of myocardial infarction were examined in 370 patients who were enrolled within 4 hours of onset of symptoms and were randomized to blinded therapy with intravenous anistreplase (30 U/5 min, n = 188) or streptokinase (1.5 million IU/1 hour, n = 182). Creatine kinase and its MB isoenzyme were initially measured every 4 to 6 hours, and lactic dehydrogenase (LDH) and its cardiac isoenzyme (LDH-1) every 8 to 12 hours. Electrocardiograms were obtained before, and at 90 minutes and 8 hours after starting thrombolysis, and on discharge. Enzymatic and electrocardiographic measures of infarction were compared between drug treatment and patency groups. Early patency was associated with significant reductions in peak values for each of 4 cardiac enzymes (averaging 21 to 25%, p less than 0.01 to 0.001), even though later rescue procedures were often used in the nonpatient group; times to peaks were also reduced for 3 of the enzymes. Treatment with anistreplase was associated with enzymatic peaks that tended to be lower than with streptokinase (6 to 16%), approaching or reaching significance for LDH (p less than or equal to 0.07) and LDH-1 (p less than or equal to 0.04); times to peaks were similar. Early patency favorably affected electrocardiographic indexes. Summed ST-segment elevations resolved more rapidly (p less than or equal to 0.04), summed Q-wave amplitude was reduced by 32% (p less than or equal to 0.01), and total QRS infarct score on discharge was 22% less (p less than or equal to 0.006) in those achieving early patency. Small differences in electrocardiographic indexes between the 2 drug treatment groups were not significant. These results support use of early reperfusion to reduce infarct size in acute myocardial infarction with administration of streptokinase and anistreplase.

Early exercise test in acute myocardial infarction treated with intravenous streptokinase

The aim of this study was to assess the value of the early exercise test (ET) in patients with acute myocardial infarction (AMI) treated with IV streptokinase (SK). The authors studied 70 patients with first AMI; 31 were treated with SK and 39 were not. Before discharge everyone was given early exercise up to 5-6 METs and catheterized within 22.9 +/- 7.2 days. There was no significant difference in the number of positive ETs between the two groups (11/31 and 14/39 respectively). There was significant difference in favor of: (1) the recanalization of the infarct-related artery in the SK group, (2) the negative ET in patients with recanalized vessels in both groups, (3) the positive ET in patients with multi-vessel coronary disease. It is concluded that the results of early ET in patients with AMI are related to the recanalization of the infarct-related artery and the coexistence of multi-vessel coronary artery disease, regardless of SK treatment. Patients with successful thrombolysis have negative ET more frequently.

The effect of streptokinase on chest pain in acute myocardial infarction

Treatment with intravenous streptokinase is known to restore blood flow to the ischaemic myocardium in patients with acute myocardial infarction. However, little is known about its effect on chest pain. In a retrospective cohort study, 76 patients treated with streptokinase were compared to 76 patients not treated with streptokinase. All patients had acute myocardial infarction and less than 6 h of cardiac symptoms. Patients treated with streptokinase had a significantly lower need for nicomorphine (median 20 mg) than patients not treated with streptokinase (median 41 mg). Correspondingly, the median duration (3.5 h) of pain was reduced significantly in patients treated with streptokinase compared to patients not treated (24 h). We conclude that intravenous streptokinase given in the acute phase of myocardial infarction is effective in reducing the duration of cardiac chest pain.

A comparison of the pharmacokinetic properties of streptokinase and anistreplase in acute myocardial infarction

1. The pharmacokinetics of streptokinase (SK) and anistreplase in conventional dosage regimens of 1.5 x 10(6) i.u. of SK infused over 60 min and 30 units of anistreplase over 5 min were studied in 24 consecutive patients presenting with acute myocardial infarction, using a functional bioassay to assess concentrations. 2. The two agents were found to have similar volumes of distribution (5.68 and 5.90 l), but SK was cleared significantly more rapidly than anistreplase, resulting in a shorter terminal phase half-life (0.61 vs 1.16 h) and a shorter mean residence time (0.76 vs 1.55 h).

Changes in standard electrocardiographic ST-segment elevation predictive of successful reperfusion in acute myocardial infarction

The ability of the electrocardiographic ST segment to predict successful reperfusion after thrombolytic therapy remains controversial. To evaluate whether angiographically determined reperfusion could be predicted from changes in ST-segment elevation, the sum of ST-segment elevation in affected leads of the electrocardiogram was compared before and after thrombolytic therapy in 53 patients with acute myocardial infarction (AMI). Reperfusion status of the infarct-related artery was determined angiographically less than 8 hours from onset of symptoms. According to the Thrombolysis in Myocardial Infarction trial (TIMI) criteria, 33 patients had successful reperfusion (TIMI grade 2 to 3 flow) after thrombolytic therapy and 20 patients did not (TIMI grade 0 to 1 flow). Logistic multiple regression analysis showed that the proportional value for the shift in the sum of ST elevation, termed the "% ST change," was more strongly associated with reperfusion than the absolute measured difference in millimeters (chi-square = 11.34 vs 9.22). The entire spectra of sensitivities and specificities were determined to identify a level of the percent ST change with simultaneous high sensitivity and specificity. A 20% decrease in ST elevation provided such a level (88% sensitivity, 80% specificity). The positive and negative predictive values of a 20% decrease in ST elevation were 88 and 80%, respectively. These results suggest that a decrease of only 20% in the sum of ST elevation in the standard electrocardiogram after thrombolytic therapy is a useful noninvasive predictor of reperfusion status in patients with evolving AMI.

Plasmin-induced platelet aggregation is accompanied by cleavage of aggregin and indirectly mediated by calpain

We recently reported that thrombin-induced platelet aggregation 1) is accompanied by cleavage of aggregin, a 100-kDa membrane protein and a putative ADP receptor, 2) is indirectly mediated by intracellularly activated calpain, and 3) requires the occupancy of high-affinity thrombin receptors. Because of the similarities between responses after platelet activation induced by thrombin and plasmin (greater than or equal to 1.0 casein unit/ml), we investigated whether or not plasmin-induced platelet aggregation proceeds by the same mechanism that underlies thrombin-induced platelet aggregation. We found that the rate of plasmin-induced aggregation of washed intact platelets and that of platelets modified by 5'-p-fluorosulfonylbenzoyladenosine (FSBA, an affinity analogue of ADP, which covalently modifies aggregin) were similar, indicating that the aggregation is independent of the ADP effect. Plasmin completely cleaved [3H]FSBA-labeled aggregin in intact platelets. A mixture of metabolic inhibitors (2-deoxy-D-glucose, gluconolactone, and antimycin A) completely inhibited plasmin-induced platelet aggregation and plasmin-induced cleavage of aggregin, demonstrating that an energy-requiring step is involved in the reaction. The synthetic hexapeptide affinity reagent Phe-Gln-Val-Val-Cys(NpyS)-Gly-NH2 (NpyS = 3-nitro-2-thiopyridine), a potent and specific inhibitor of thrombin-induced platelet aggregation and platelet calpain, completely inhibited plasmin-induced platelet aggregation and plasmin-induced cleavage of aggregin. These results suggest that, like thrombin, plasmin-induced platelet aggregation is accompanied by the cleavage of aggregin and these responses are indirectly mediated by the intracellularly activated calpain.(ABSTRACT TRUNCATED AT 250 WORDS)

Preventive strategies in management of acute myocardial infarction

Recent studies on pathogenetic mechanisms, supplemented by findings in clinical trials point the way to a logical approach to acute evolving myocardial infarction. This is designed in the earliest stage to limit infarction through reduction in myocardial oxygen demands, improvement in collateral blood supply and dissolution of coronary thrombus, to prevent in a later stage coronary reocclusion through administration of antiplatelet agents, and then to prevent infarct expansion through reduction in ventricular wall tension throughout the period of repair. Application of such an approach holds the promise of reducing infarct size and all the complications of infarction, as well as short and long-term mortality. The approach is active and aggressive, and contrasts with the approach applied a decade ago, where infarction was accepted as inevitable and therapies were reserved for managing its complications.

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.

Clinical and laboratory signs of reperfusion: are they reliable?

We studied 101 patients (88 men and 13 women, mean age 54.5 +/- 10 years) who arrived at the hospital during the first 6 hours of acute myocardial infarction evolution. Our objective was to assess the reliability of clinical and laboratory signs of recanalization using intravenous streptokinase as a thrombolytic agent. The mean time between the beginning of infusion and coronary arteriography was 53.83 +/- 43 hours. The positive predictive values for pain, arrhythmia, ST segment and enzymes were 97.9%, 94.2%, 91.8% and 90.8%, respectively; the negative predictive values were 46.8%, 40.8%, 37.2%, and 50% in the same order. Sensitivity was 65.7%, 62.8%, 58.4% and 77.6% and specificity 95.6%, 86.9%, 82.6% and 73.9%, respectively. The positive predictive value, calculated on the basis of the presence of each variable alone or in association showed a probability of recanalization of 76.9% for one sign, 84% for two, 96.3% for three and 100% for all four. When we compared the positive predictive values of each variable according to the interval between the beginning of pain and admission to the hospital (during the first 3 hours or between 3 and 6 hours) our results were 100%/94% for pain (P = NS), 97%/88% for arrhythmia (P = NS), 100%/75% for ST segment (P = 0.004), and 97%/80% for enzymes (P = 0.019). The same analysis applied to negative predictive values showing 22%/62% (P = 0.007), 17%/55% (P = 0.008), 21%/47% (P = NS), 27%/61% (P = NS) for pain, arrhythmia, ST segment and enzymes, respectively.(ABSTRACT TRUNCATED AT 250 WORDS)

Acute myocardial infarction-related coronary artery residual narrowing after intravenous streptokinase: relationship with previous coronary symptoms

In 72 patients who received streptokinase within 6 hours of the onset of an acute myocardial infarction (AMI), the relationship between the presence of a previous coronary event and the severity of the residual coronary artery stenosis was studied. Fifty-five patients were either asymptomatic or had recent onset angina (less than 5 days) before AMI (group A) and 17 patients had chronic angina (greater than 1 year) before AMI (group B). Coronary angiograms were performed at 20 days (range 15 to 25 days). Patency of the infarct-related artery was greater in group A: 43 of 55 patients (78%) versus 8 of 17 patients (47%) in group B (p less than 0.05). Residual stenosis was less than 70% in 21 patients of group A (49% of patent arteries), whereas it manifested in none of eight patients with patent arteries in group B (p less than 0.01). This suggests that thrombosis was a major component of the coronary artery narrowing in group A patients, while it is more likely that thrombus only completes a previously severe (greater than 70%) coronary artery stenosis in patients with long-standing angina before AMI.

Long-term results of thrombolytic therapy with and without percutaneous transluminal coronary angioplasty

The effects of combined intravenous and intracoronary streptokinase without (Group I, n = 103) or with (Group II, n = 103) immediate coronary angioplasty were evaluated during a long-term (3 year) follow-up of 206 patients with acute transmural myocardial infarction. There were no baseline differences between the groups with regard to gender, age, infarct location, serum creatine kinase levels, time between onset of symptoms and treatment and coronary artery patency rate. Angioplasty was performed with a success rate of 69% and a reocclusion rate of 2%. Elective angioplasty was performed in 22 (21%) of 103 patients in Group I and 9 (9%) of 103 patients in Group II, with a success rate of 86% and 100%, respectively, reflecting the higher incidence of angina pectoris and antianginal therapy in Group I. Coronary bypass surgery was performed in 21 (20%) of 103 patients in Group I and 20 (19%) of 103 patients in Group II; there was one operative death in each group. During follow-up, coronary reocclusion or reinfarction, or both, occurred in 25 (29%) of 87 patients in Group I and in 16 (18%) of 87 patients in Group II with reperfused vessels (p = NS). Heart failure occurred in 40% of the patients in both groups who had increased end-diastolic and end-systolic volumes. The survival rate after 3 years was 78% in Group I and 80% in Group II (p = NS). Thus, long-term follow-up of patients with acute transmural infarction treated with and without immediate angioplasty does not demonstrate any difference with regard to clinical outcome and mortality.

Is aeromedical transport of patients during acute myocardial infarction safe?

The emergence of coronary artery thrombolysis and angioplasty have raised new questions about the transfer of patients with acute myocardial infarction (AMI). Since these modalities are generally limited in their availability, and since the success of thrombolysis is strongly time-dependent, the interfacility transfer of patients during AMI has become more common. Study of a relatively small number of patients indicates that aeromedical helicopter transport can be conducted in a safe manner, and that the outcome of management is of benefit to the patients. Reperfusion events, however, must be anticipated during transport of patients in whom thrombolysis is initiated preflight. Furthermore, initiation of thrombolytic therapy may be problematic if begun in patients with events mimicking AMI, particularly aortic dissection or Prinzmetal's angina.

Treatment of pain in acute myocardial infarction

The treatment of pain in acute myocardial infarction varies with local practice. Narcotic analgesics are still the usual treatment in many hospitals. Knowledge of optimal doses, duration of pain relief, and time between drug administration and pain relief is inadequate. Many studies indicate that the relief of pain is often incomplete after treatment with narcotic analgesics. There is often a need for alternative treatments. Large randomised studies consistently show that beta blockade, initially given intravenously and then orally, relieves pain and reduces the need for analgesics. Studies also indicate that early administration of streptokinase and glyceryl trinitrate relieves pain. There is evidence that drugs that limit ischaemic damage also relieve pain.

A system approach to intravenous thrombolysis in acute myocardial infarction in community hospitals: the influence of paramedics

During a 3-year period, intravenous streptokinase (IV STK) was given to 110 consecutive patients ages 34-78 in the course of acute myocardial infarction (AMI) in three community hospitals served by the same paramedic system. 1.5 million units of IV STK was given over 30 minutes. Half of the patients were brought to the hospital by paramedics. The average time from onset of pain to administration of IV STK was 107 minutes in the paramedic group and 182 minutes for the others. Of 110 patients, 98 (89%) showed clinical evidence of reperfusion and 94 of 106 patients (89%) showed angiographic reperfusion. Angiography was performed from 1 to 10 days post-AMI. Mean time to angiography was 6 days for the first 58 patients and 2 days for the last 52 patients. In-hospital mortality was 2 of 110 patients and there was 1 late death at 8 months for an overall 3-year mortality 2.7%. Of 86 patients, 83 (96%) working before their infarct are working now. Of 107 survivors, 96 (90%) are Functional Class I.

CONCLUSIONS

(1) IV STK is safely administered in a high percentage of AMI patients. (2) IV STK is safely administered in community hospitals. (3) Paramedics act as an early warning system and allow for earlier treatment than patients presenting without paramedic involvement. (4) Successful coronary reperfusion with IV STK results in low mortality rates and minimizes functional disability. (5) A system-wide approach to reducing time to treatment in AMI may be the most influential factor in affecting morbidity and mortality.

Left ventricular topographic alterations in the completely healed rat infarct caused by early and late coronary artery reperfusion

Topographic changes in the completely healed (6 weeks) left ventricle of the rat, caused by early (30 minutes) and delayed (90 minutes) coronary artery reperfusion, were examined. With early reperfusion the extent of the scar, as a percentage of left ventricular (LV) circumference, was reduced compared to the extent of the scar in rats with permanent occlusion (27 +/- 3% vs 42 +/- 2%, p less than 0.01). Early reperfusion also preserved LV topography by preventing dilation of the LV cavity and thinning of the healed free wall. Late reperfusion (90 minutes) did not reduce the extent of the scar (35 +/- 3% vs 42 +/- 2% of LV circumference, p = NS) or prevent dilation of the LV cavity compared with permanent occlusion. However, the healed free wall/noninfarcted septum ratio was significantly greater in rats with late reperfusion than in those with permanent occlusion (0.98 +/- 0.06 vs 0.73 +/- 0.07, p less than 0.05). Thus early reperfusion completely inhibited scar thinning and dilation of the LV cavity, maintaining normal LV topography. Late reperfusion, too late to reduce infarct size, still contributed to improved healing of the myocardium by resulting in a thicker scar.

Do different doses of intravenous streptokinase alter the frequency of coronary reperfusion in acute myocardial infarction?

This study assessed the relative efficacy of 3 doses of intravenous streptokinase in causing hypofibrinogenemia and coronary reperfusion in patients with acute myocardial infarction. Accordingly, 56 patients (50 men and 6 women, ages 58 +/- 10 years [mean +/- standard deviation]) with evolving acute myocardial infarction and chest pain less than or equal to 5 hours in duration were assigned to receive varying doses of streptokinase. Twenty were administered 500,000 units during 145 minutes, 18 were given 750,000 units during 30 minutes and 18 received 1.5 million units in 60 minutes of streptokinase. Serum creatine kinase was measured on admission and 6, 12, 18 and 24 hours after the initiation of streptokinase. The time intervals from onset of pain to peak creatine kinase and from streptokinase administration to peak creatine kinase were used to determine the occurrence of reperfusion. The plasma fibrinogen concentration was measured 30, 60, 90 and 120 minutes after the initiation of streptokinase. For the 3 groups, the time from onset of pain to peak creatine kinase was less than 17 hours and the time from streptokinase to peak creatine kinase was 6 or 12 hours in 15 (75%), 16 (89%) and 12 patients (67%), respectively (differences not significant). The plasma fibrinogen concentration decreased to 45 +/- 34 mg/dl, 19 +/- 14 mg/dl and 29 +/- 43 mg/dl, respectively, during the 2 hours after streptokinase was begun (p less than 0.05 for the first versus the second and third values).(ABSTRACT TRUNCATED AT 250 WORDS)

Effect of reperfusion on electrocardiographic and enzymatic infarct size: results of a randomized multicenter study of intravenous anisoylated plasminogen streptokinase activator complex (APSAC) versus intracoronary streptokinase in acute myocardial infarction

The effect of early coronary artery reperfusion on ECG and enzymatic parameters was examined in 240 patients with acute myocardial infarction. These patients had participated in a randomized trial comparing intravenous anisoylated plasminogen streptokinase activator complex (APSAC) (n = 123) and intracoronary streptokinase (n = 117) therapy. Reperfusion occurred in 59 of 115 (51%) patients receiving APSAC and 67 of 111 (60%) patients receiving streptokinase (p = NS). There was greater early resolution of ST segment elevation in the reperfused than in the nonreperfused patients (p less than or equal to 0.003) and more rapid Q wave evolution (p less than or equal to 0.03). Sigma Q was lower in reperfused than in nonreperfused patients at 8 hours (1.41 +/- 1.18 versus 2.11 +/- 2.10 mV; p less than or equal to 0.05) and at 24 hours (1.43 +/- 1.25 mV versus 2.08 +/- 1.88 mV; p less than or equal to 0.02). Time to peak level was shorter in the reperfused patients for creatine kinase (CK) (10.7 +/- 5.5 hours versus 14.9 +/- 5.9 hours; p less than 0.0001) and lactic acid dehydrogenase (LDH) (29.6 +/- 13.6 hours versus 34.4 +/- 10.5 hours; less than or equal to 0.03) enzymes. Peak LDH-1 was lower in the reperfused group (274 +/- 149 U/L versus 341 +/- 173 U/L; p less than or equal to 0.04). Reperfusion at a mean of 3.9 hours after the onset of infarction was associated with more rapid resolution of ST segment elevation, faster Q wave evolution, smaller ECG infarct size, earlier cardiac enzyme release, and smaller enzymatic infarct size than later or no reperfusion.

Electrocardiographic prediction of coronary artery patency after thrombolytic treatment in acute myocardial infarction: use of the ST segment as a non-invasive marker

The predictive value of the measurement of changes in ST segment elevation was assessed as a non-invasive marker of coronary artery reperfusion after thrombolytic treatment. Forty five patients with acute myocardial infarction (23 anterior, 22 inferior) of less than six hours' duration were given thrombolytic treatment by either the intravenous (n = 28) or the intracoronary route (n = 17). A proportional value for the shift in ST segment, termed the fractional change, was calculated both from 12 lead electrocardiograms and from the Holter tape for each patient. Coronary artery patency in an initial group of 22 patients (training group) was associated with a fractional change value of greater than or equal to 0.5 (100% specific, 88% sensitive by Holter analysis; 100% specific, 94% sensitive by 12 lead electrocardiogram). This rule performed well when it was applied to a test group of 17 patients (100% specific, 93% sensitive by Holter analysis; and 67% specific, 93% sensitive by 12 lead electrocardiogram). Linear discriminant analysis was then used to determine which features gave the best separation of those in whom there was reperfusion and those in whom there was not. This gave 100% specificity and 100% sensitivity when applied to the training group for either the 12 lead electrocardiogram or Holter monitoring. When it was applied to the test group, the sensitivity was maintained at 100%, but the specificity dropped to 33% irrespective of whether the basis of the test was Holter monitoring or the 12 lead electrocardiogram. These results suggest that a fractional change of >/= 0.5 calculated from a single lead showing myocardial injury is a useful non-invasive marker of reperfusion. The technique can be applied to either 12 lead electrocardiograms or Holter monitoring. The use of a more complex classification increased the sensitivity of the test at the expense of its specificity.

Evolving concepts in the treatment of acute myocardial infarction

Recent studies in patients with transmural acute myocardial infarction have demonstrated that intravenous thrombolytic therapy with streptokinase or tissue plasminogen activator improves left ventricular function and reduces mortality. To accomplish this, these agents must be infused early, ie, within 3 to 4 hours of the onset of chest pain; later administration of the agents exerts no significant beneficial effect. Tissue plasminogen activator appears to be the most effective and safest of the available thrombolytic agents: its intravenous administration is followed by coronary reperfusion in about 70% of patients, and its use is not associated with allergic reactions, a systemic fibrinolytic state, or a prolonged fibrinolytic effect. Once reperfusion has been established with an intravenous thrombolytic agent, intravenous heparin is given for several days, followed by oral aspirin to prevent reocclusion. Since many of these patients have a residual high-grade coronary artery stenosis in the infarct-related artery, mechanical alleviation of the residual stenosis with angioplasty or bypass surgery is an attractive therapy 2 to 4 days after reperfusion, and preliminary data indicate that elective coronary angioplasty 3 days after thrombolytic therapy is beneficial. However, further studies are needed to assess more definitively the use of such an aggressive therapeutic strategy.