Hemodynamic, mechanical, and metabolic determinants of thrombolytic efficacy: a theoretic framework for assessing the limitations of thrombolysis in patients with cardiogenic shock

Management of Cardiogenic Shock Due to Acute Coronary Syndromes

Despite advances in the treatment of patients with acute coronary syndromes, there has been no significant decrease in the incidence of cardiogenic shock, while its mortality remains frustratingly high. Shock is a progressive state of hypotension (systolic blood pressure <90 mm Hg) lasting at least 30 minutes, which leads to systemic hypoperfusion. It is more common in patients with ST-segment elevation myocardial infarction than in patients with other acute coronary syndromes. Revascularization is associated with better outcomes than intensive medical therapy, especially in patients <75 years of age with cardiogenic shock. Adjunctive therapies include inotropes, vasopressor therapy, intra-aortic balloon pump counterpulsation, and IIb/IIIa blockade to prevent no-reflow phenomenon during primary percutaneous transluminal coronary angioplasty. Other adjunctive therapies which are investigated are improved mechanical support devices, and as medical therapy for myocyte protection nicorandil, glucose/insulin/potassium infusions and direct inhibition of Na+/H+ exchanger.

Lytic failure in the current pharmacointensive ST-elevated acute myocardial infarction care: insights from a pilot real-world study

BACKGROUND

Thrombolysis remains a very acceptable reperfusion option for ST-elevated acute myocardial infarction (STEMI); however, it fails relatively frequently and unpredictably.

AIM AND METHODS

To investigate correlates of lytic failure (according to the standard ST resolution criterion) in current pharmacointensive STEMI care (dual antiplatelets with antithrombin), we analyzed retrospectively clinical data and echocardiographic left ventricular systolic function before initiation of reperfusion treatment in Killip I-III STEMI patients admitted to our 'spoke' intensive cardiac care unit between 1 January and 31 December 2010.

RESULTS

Of the 53 STEMI patients enrolled, 28% failed thrombolysis. Patients who did not reperfuse were less frequently active smokers (P < 0.05, odds ratio 4.33) and had a higher prevalence of hemodynamic instability [heart rate/SBP (i.e. shock index) >0.75; P < 0.05, odds ratio 13.45) and left ventricular systolic dysfunction (ejection fraction <45%; P < 0.005, odds ratio 11.14). In an exploratory multivariable logistic regression analysis, those variables were the only discriminators independently associated with lytic failure (adjusted odds ratio 8.74, 230.10, and 18.22, respectively, all P < 0.05). Moreover, the combined variables had a high accuracy for prediction of failed thrombolysis (all discriminators positive, 99% specificity and 83% positive predictive value).

CONCLUSION

Our pilot study indicates that thrombolysis still fails in about one-third of STEMI patients despite the current pharmacointensive approach and suggests that failed ST resolution might be independently associated with nonsmoking habit and pretreatment hemodynamic instability and left ventricular systolic dysfunction. Larger trials are needed to verify the potential clinical implications of our preliminary observation.

Percutaneous coronary intervention in cardiogenic shock complicating acute ST-elevation myocardial infarction-a single centre experience

BACKGROUND

Mortality in acute myocardial infarction (AMI) complicated by cardiogenic shock (CS) approaches 70 - 80%, regardless of the type of pharmacological treatment. Early revascularisation improves survival in AMI with CS. Our aim is to assess the predictors of mid-term outcome after percutaneous coronary intervention (PCI) in patients with ST-segment elevation myocardial infarction (STEMI) and CS.

METHODS

Forty-one patients who underwent primary or rescue PCI for CS were analysed comparing their baseline, angiographic, PCI data, 30-day and 1-year survival.

RESULTS

There were no significant differences between survivors and non-survivors in baseline characters, except for more number of transfer admissions (P= 0.0005), and cardiopulmonary resuscitations (P= 0.015) in the later group. The mean time between myocardial infarction (MI) onset to shock and MI onset to revascularisation were 12.8 ± 12.9 hours and 17.0 ± 16.8 hours, respectively. Patients with better pre-procedure thrombolysis in myocardial infarction (TIMI) flow in the infarct-related artery (IRA) had better survival (P= 0.0005). Successful PCI was achieved in 48.8% of patients. The 30-day mortality was 56.1% and all were prior to hospital discharge. Patients with successful PCI had better short-term survival in comparison with patients with failed PCI (80% vs 9.6%). Eighteen patients who survived at 30 days were followed up for 12-72 months (mean 28.5 ± 5.4 months). Fifteen patients survived at 1 year after PCI and all were in good functional status.

CONCLUSION

Mortality remains high even with PCI. Achieving IRA patency with TIMI 3 flow is the main determinant of survival. Survival and functional status are good in patients who are discharged from hospital.

Cardiogenic shock

The syndrome of cardiogenic shock (CS) comprises a constellation of symptoms and signs that define a subset of patients with inadequate tissue perfusion secondary to myocardial dysfunction. Careful attention to and rapid identification of patients at risk for the development of CS and those with impending CS by both hospitalists and subspecialists will help to implement the time-sensitive therapy that it requires. Physicians should gain a familiarity with the underlying pathophysiology of CS and available diagnostic tools as well as the importance of vasopressor therapy, inotropic therapy, rapid reperfusion therapy, and mechanical support.

Cardiogenic shock: therapy and prevention

Cardiogenic shock is defined as profound circulatory failure resulting in insufficient tissue perfusion to meet resting metabolic demands. It occurs in approximately 7.5% of patients with acute myocardial infarction. Treatment strategies include inotropic agents, use of intra-aortic balloon counterpulsation, and revascularization. Current evidence supports the use of primary angioplasty. Surgery should be considered in patients with triple-vessel disease. If early catheterization is not available, thrombolytic therapy should be given to eligible patients and transfer to an interventional facility should be considered. Effective therapy for shock must also include a prevention strategy. This requires identification of patients at high risk for shock development and selection of patients who are candidates for aggressive intervention.

Critical care aspects in the management of patients with acute coronary syndromes

The spectrum of acute coronary syndromes (ACS) includes several clinical complexes that frequently cause critical instability in affected patients. This article focuses on several critical care aspects of these unstable ACS patients. The management of cardiogenic shock can be particularly challenging because the mechanical defects are varied in cause, severity, and specific treatment. Complications of fibrinolytic therapy are potentially deadly and arrhythmias are relatively common in the ACS patients. Discussions on the management of these problems should help the emergency physician more effectively to treat critically ill patients with ACS.

Management of cardiogenic shock attributable to acute myocardial infarction in the reperfusion era

Cardiogenic shock is the leading cause of death among patients hospitalized with acute myocardial infarction. It is defined as tissue hypoperfusion resulting from ventricular pump failure in the presence of adequate intravascular volume. Rapid assessment and triage of patients presenting in cardiogenic shock followed by appropriate institution of supportive therapies including vasopressor and inotropic agents, mechanical ventilatory support, and intra-aortic balloon pump counterpulsation are critical for effective management of these patients. However, emergency percutaneous coronary intervention or coronary artery bypass graft surgery is required to decrease mortality rates. Novel approaches, including inhibition of nitric oxide synthase and new mechanical support devices, may further decrease mortality rates, which remain high despite reperfusion therapy.

Relation between hospital intra-aortic balloon counterpulsation volume and mortality in acute myocardial infarction complicated by cardiogenic shock

BACKGROUND

Increasing evidence suggests an inverse relationship between outcome and the total number of invasive cardiac procedures performed at a given hospital. The purpose of the present study was to determine if a similar relationship exists between the number of intra-aortic balloon counterpulsation (IABP) procedures performed at a given hospital per year and the in-hospital mortality rate of patients with acute myocardial infarction complicated by cardiogenic shock.

METHODS AND RESULTS

We analyzed data of 12 730 patients at 750 hospitals enrolled in the National Registry of Myocardial Infarction 2 from 1994 to 1998. The hospitals were divided into tertiles (low-, intermediate-, and high-IABP volume hospitals) according to the number of IABPs performed at the given hospital per year. The median number of IABPs performed per hospital per year was 3.4, 12.7, and 37.4 IABPs at low-, intermediate-, and high-volume hospitals, respectively. Of those patients who underwent IABP, there were only minor differences in baseline patient characteristics between the 3 groups. Crude mortality rate decreased with increasing IABP volume: 65.4%, lowest volume tertile; 54.1%, intermediate volume tertile; and 50.6%, highest volume tertile (P for trend <0.001). This mortality difference represented 150 fewer deaths per 1000 patients treated at the high IABP hospitals. In the multivariate analysis, high hospital IABP volume for patients with acute myocardial infarction was associated with lower mortality (OR=0.71, 95% CI=0.56 to 0.90), independent of baseline patient characteristics, hospital factors, treatment, and procedures such as PTCA.

CONCLUSIONS

Among the myocardial infarction patients with cardiogenic shock who underwent IABP placement, mortality rate was significantly lower at high-IABP volume hospitals compared with low-IABP volume hospitals.

The use of intra-aortic balloon counterpulsation in patients with cardiogenic shock complicating acute myocardial infarction: data from the National Registry of Myocardial Infarction 2

BACKGROUND

Cardiogenic shock complicating acute myocardial infarction (AMI) remains the leading cause of death in patients hospitalized with AMI. Although several studies have demonstrated the importance of establishing and maintaining a patent infarct-related artery, it remains unclear as to whether intra-aortic balloon counterpulsation (IABP) provides incremental benefit to reperfusion therapy. The purpose of this study was to determine whether IABP use is associated with lower in-hospital mortality rates in patients with AMI complicated by cardiogenic shock in a large AMI registry.

METHODS

We evaluated patients participating in the National Registry of Myocardial Infarction 2 who had cardiogenic shock at initial examination or in whom cardiogenic shock developed during hospitalization (n = 23,180).

RESULTS

The mean age of patients in the study was 72 years, 54% were men, and the majority were white. The overall mortality rate in all patients who had cardiogenic shock or in whom cardiogenic shock developed was 70%. IABP was used in 7268 (31%) patients. IABP use was associated with a significant reduction in mortality rates in patients who received thrombolytic therapy (67% vs 49%) but was not associated with any benefit in patients treated with primary angioplasty (45% vs 47%). In a multivariate model, the use of IABP in conjunction with thrombolytic therapy decreased the odds of death by 18% (odds ratio, 0.82; 95% confidence interval, 0.72 to 0.93).

CONCLUSIONS

Patients with AMI complicated by cardiogenic shock may have substantial benefit from IABP when used in combination with thrombolytic therapy.

Cardiogenic shock

Mortality rates in patients with cardiogenic shock remain frustratingly high. Its pathophysiology involves a downward spiral in which ischemia causes myocardial dysfunction, which in turn worsens ischemia. Areas of viable but nonfunctional myocardium can contribute to the development of cardiogenic shock. Rapid diagnosis and prompt initiation of supportive therapy to maintain blood pressure and cardiac output, followed by expeditious coronary revascularization, are crucial. The SHOCK multicenter randomized trial has provided important new data that support a strategy of emergent cardiac catheterization and revascularization with angioplasty or coronary surgery when feasible. This strategy can improve survival and represents standard therapy at this time. In hospitals without direct angioplasty capability, stabilization with IABP and thrombolysis followed by transfer to a tertiary care facility may be the best option.

Brief antecedent ischemia enhances recombinant tissue plasminogen activator-induced coronary thrombolysis by adenosine-mediated mechanism

BACKGROUND

Clinical studies have implicated preinfarct angina (brief antecedent ischemia/reperfusion [I/R]) as a predictor of more rapid thrombolysis and lower rates of reocclusion. However, the effects of antecedent ischemia on the efficacy of thrombolysis have not been rigorously assessed. Using a canine model of coronary thrombosis, we aimed to (1) reproduce these clinical findings and (2) determine whether release of adenosine (a potent inhibitor of platelet aggregation via stimulation of platelet A(2) receptors) during brief I/R contributes to this improved patency.

METHODS AND RESULTS

To address our first objective, we compared the time required to achieve lysis with recombinant tissue plasminogen activator and patency during the first 2 hours after lysis in dogs in which 1-hour thrombotic occlusion was preceded by brief I/R (10-minute coronary occlusion/10-minute reperfusion) versus 20-minute uninterrupted perfusion (controls). Time to lysis was accelerated in the I/R group versus the control group (11+/-1 versus 35+/-6 minutes, P=0.004). In addition, the duration of subsequent reocclusion was reduced (17+/-12 versus 30+/-11 minutes), and the area of the flow-time profile (normalized to baseline flow x 120 minutes) was increased (64+/-12% versus 35+/-7%, P=0.04) in the I/R cohort. The protocol was then repeated, but all dogs were pretreated with the adenosine A(2)/A(1) antagonist CGS 15943 (CGS, 1.5 mg/kg). Time to lysis (38 versus 39 minutes) and subsequent patency were comparable in the CGS+control group versus the CGS+I/R group.

CONCLUSIONS

Brief antecedent I/R enhances the efficacy of coronary thrombolysis in this canine model, which is due, at least in part, to an adenosine-mediated mechanism.

Thrombolysis in Acute Myocardial Infarction Complicated by Cardiogenic Shock

The adverse impact of the development of cardiogenic shock in the setting of acute myocardial infarction was first described by Killip and Kimball in 1967. While the in-hospital mortality rate in patients with myocardial infarction and no evidence of heart failure was only 6%, the mortality rate in those patients who developed cardiogenic shock was 81%. Despite advances in cardiovascular care and therapy since that initial report, including universal institution of cardiac care units, advances in hemodynamic monitoring, new inotropic and vasodilating agents, and even increasing utilization of thrombolytic therapy, the mortality from acute myocardial infarction, when complicated by cardiogenic shock, remains disturbingly high, and cardiogenic shock remains the leading cause of death of hospitalized patients following acute myocardial infarction.The grave prognosis associated with this condition has resulted in increased interest in potential therapeutic interventions, particularly in the area of reperfusion therapy. Several studies suggest that, in contrast to the beneficial effects of thrombolytic therapy in most patient populations suffering acute myocardial infarction, mortality rates are not decreased in those patients with cardiogenic shock at the time of lytic administration. Thrombolytic administration does, however, appear to lead to a modest reduction in the percent of patients with myocardial infarction who will subsequently develop cardiogenic shock during hospitalization.Reperfusion rates with lytic therapy in patients with cardiogenic shock are disappointingly low, in the range of 42-48%, significantly lower than those achieved in patients without cardiogenic shock. These low perfusion rates may, in part, be explained by decreased coronary blood flow and perfusion pressure in patients with left ventricular pump failure.Although promising as adjunctive therapy, it is unclear whether institution of balloon counterpulsation has any long-term benefit in patients with cardiogenic shock treated with thrombolytic therapy. Whether other or additional interventions, such as coronary angioplasty and coronary artery bypass graft (CABG), decrease mortality rates in patients with cardiogenic shock remains to be determined.

Acute myocardial infarction with cardiogenic shock on admission: incidence, prognostic implications, and current treatment strategies. Results from "the 60-Minutes Myocardial Infarction Project". ALKK ("Arbeitsgemeinschaft leitender Krankenhauskardiologen") Study Group

Little data exist about current treatment strategies the efficacy of thrombolytic therapy and outcome of patients with acute myocardial infarction (AMI) presenting in cardiogenic shock (CS). Data from the German multicenter "60 Minutes Myocardial Infarction Project" were used to analyze a large number of patients with AMI and CS on admission and to compare those to patients without CS. Between July 1993 and September 1994 a total of 7,085 patients with AMI were registered. Out of these, 179 patients (2.5%) presented in CS (systolic blood pressure < 100 and heart rate > 100/min, resuscitated patients were excluded). Patients in CS were significantly older than patients without CS. Their in-hospital mortality was 47.1% compared with 12.4% in patients without CS (p = 0.001). The prevalence of the following clinical parameters was significantly higher in patients with CS than in those without CS: bundle branch block, prior MI, and a non-diagnostic ECG (all p < 0.05). Thrombolytic therapy was used in 36.3% of patients in CS and in 50.8% of those without CS (p = 0.001). The in-hospital mortality in patients with CS receiving thrombolytic therapy was significantly lower than in patients with CS who did not receive thrombolytic agents (33.3% versus 55.1%; p = 0.006). In daily clinical practice in Germany thrombolytic treatment is used in only 36.3% of patients with AMI presenting in CS on admission. The use of thrombolysis in CS on admission is associated with a lower in-hospital mortality.

Echocardiography's Role in Cardiogenic Shock After Acute Myocardial Infarction

Cardiogenic shock is an emergent condition that requires immediate diagnosis. Assessment and evaluation of potential complications that often accompany shock must also be made. These complications may be seen individually or in concert. Echocardiography has emerged in the last two decades as the single most important procedure in this effort. The authors reviewed four cases of cardiogenic shock after acute myocardial infarction: two with ventricular septal rupture, one with papillary muscle rupture, and one with severe global left ventricular dysfunction. Each patient was evaluated emergently with echocardiography. Results were compared with electrocardiography, arteriography, right heart catheterization studies, and surgical reports.

Clinical predictors of early infarct-related artery patency following thrombolytic therapy: importance of body weight, smoking history, infarct-related artery and choice of thrombolytic regimen: the GUSTO-I experience. Global Utilization of Streptokinase and t-PA for Occluded Coronary Arteries

OBJECTIVES

The purpose of this study was to determine patient characteristics that are a priori predictors of early infarct related artery patency following thrombolytic therapy, and to provide a paradigm which may identify patients who would be most likely to achieve restoration of normal (TIMI 3) coronary flow in response to thrombolytic therapy.

BACKGROUND

Restoration of infarct-related artery perfusion in acute myocardial infarction is necessary for preservation of ventricular function and mortality reduction. Clinical variables that are a priori predictors of early patency with currently available thrombolytic regimens have not been fully characterized.

METHODS

The probability of early infarct-related artery patency (TIMI 3 flow) was determined by multivariable logistic regression. We determined a reduced (parsimonious) model for predicting early (90 min) infarct-related artery patency (TIMI grade 3) based on data from 1,030 patients in the GUSTO-I Angiographic study.

RESULTS

Predictors of 90 min TIMI 3 flow are use of an accelerated t-PA regimen (vs. streptokinase containing regimens) (chi2=39.1; p < or = 0.0001), infarct related artery (RCA/Lcx vs. LAD) (chi2=12.7; p=0.0004), body weight (chi2=10.3; p=0.001) and history of smoking (chi2=7.4; p=0.007). Time from symptom onset to treatment was not significant (p=0.71).

CONCLUSIONS

The efficacy of currently available thrombolytic regimens is chiefly dependent on choice of thrombolytic regimen, body weight, infarct-related coronary artery and smoking history. Clinical variables alone correctly predict a priori TIMI 3 flow in the infarct-related artery 64% of the time. Patients with body weights greater than 85 kg are at a significant disadvantage with regard to achieving successful thrombolysis compared to those with lesser body weights.

[Differential characteristics and survival of women with acute myocardial infarction. Registry of Acute Myocardial Infarctions of the City of Valencia (RICVAL). Researchers of the RICVAL]

INTRODUCTION AND OBJECTIVES

The prevalence of women who are admitted to the hospital after acute myocardial infarction is lower to that of men and their prognosis is worse. The reason for these differences is unclear. We studied the demographic and historical variables, the evolution, treatment and early survival in 269 women included in the Register of Acute Myocardial Infarctions of the City of Valencia (RICVAL) and compared them with the 855 men included in the same Register.

PATIENTS AND METHODS

Register of patients admitted into a Coronary Care Unit in the City of Valencia since December, 1st, 1993 until November 30th, 1994.

RESULTS

23.9% of the patients were women with a mean age of 71.9 +/- 9 years; 46.8% of them were diabetics, 55.4% hypertensives, and 6.7% smokers. The women arrived for treatment later than men and 34.9% of them were thrombolised. The incidence in women of severe heart failure (Killip III and IV) was 40.1% and the mortality 29.7%. In women with thrombolytic treatment the mortality was 29.8%. In the logistic regression model performed, female sex predicted a higher mortality rate (odds ratio [OR] = 1.30; confidence interval [CI], 1.05-1.61).

CONCLUSIONS

Early mortality in women after acute myocardial infarction is higher than in men in the RICVAL Register. The longer delay in initiating medical care and thrombolysis might be the cause for the higher proportion of heart failure among women and explain their worse prognosis after an acute myocardial infarction compared to men.

One-year results from the Global Utilization of Streptokinase and TPA for Occluded Coronary Arteries (GUSTO-I) trial. GUSTO-I Investigators

BACKGROUND

In the randomized Global Utilization of t-PA and Streptokinase for Occluded Coronary Arteries (GUSTO-I) trial, 41021 patients received one of four thrombolytic regimens. Patients treated with accelerated tissue plasminogen activator (TPA) had a lower 30-day mortality rate (6.3%) than those treated with the other regimens (7.3%, combined streptokinase groups).

METHODS AND RESULTS

Each patient who was alive at 30 days was sent a return postcard to ascertain vital status at 1 year. If the postcard was not returned, the patient (or an alternate specified at randomization) was contacted by telephone. A locator service was used in the United States for patients who could not be located by these methods. Final follow-up was 96% worldwide. One-year mortality rates remained in favor of accelerated TPA (9.1%) over streptokinase with subcutaneous heparin (10.1%, P = .011) and streptokinase with intravenous heparin (10.1%, P = .009). Combination therapy had an intermediate 1-year mortality (9.9%); this outcome was statistically indistinguishable from that with streptokinase (P = .47) but was marginally different from that with accelerated TPA (P = .05).

CONCLUSIONS

The 1-year results demonstrated a saving of 10 lives per 1000 patients treated with accelerated TPA versus streptokinase and subcutaneous or intravenous heparin. Combination thrombolytic therapy had an intermediate benefit but offered no advantage over accelerated TPA treatment alone.

Cardiogenic shock: thrombolysis or angioplasty?

Cardiogenic shock (CGS) occurs in 3 to 20% of patients presenting with acute myocardial infarction (MI), and it generally involves dysfunction of at least 40% of the total myocardial mass. Prior to the advent of balloon angioplasty and thrombolysis, in-hospital mortality was greater than 75%. This mortality rate has been consistent in reported series despite the advent of cardiac intensive care units, vasopressor, inotropic, and vasodilator therapy. Intra-aortic balloon counterpulsation therapy provides hemodynamic improvement, and it may provide some mortality benefit when used in conjunction with appropriate revascularization. Survival studies have shown that patency of the infarct-related artery is a strong predictor of survival. No randomized trials have been completed to examine which reperfusion therapy best treats this emergent situation. Subgroup analysis of large scale, multicenter trials, although underpowered, has shown no improvement in mortality with use of thrombolytic agents, leading many to advise use of mechanical intervention. In patients who present with acute MI with contraindications to thrombolysis, primary angioplasty is the treatment of choice. At selected centers, primary angioplasty is comparable to or better than thrombolytic therapy for patients presenting with acute MI, with or without CGS. Studies examining angioplasty in patients with CGS have shown high procedural success rates (75%) and reduced in-hospital mortality (44%), particularly in those patients with successful revascularization. Emergency bypass surgery may improve survival, but it is costly, unavailable to many, and often leads to excessive delays in therapy. If available, we believe that primary angioplasty is the treatment of choice for patients with CGS.

Contemporary reperfusion therapy for cardiogenic shock: the GUSTO-I trial experience. The GUSTO-I Investigators. Global Utilization of Streptokinase and Tissue Plasminogen Activator for Occluded Coronary Arteries

OBJECTIVES

This study sought to examine the incidence, temporal profile and clinical implications of shock in a large trial of thrombolytic therapy for acute myocardial infarction.

BACKGROUND

Despite advances in the treatment of acute ischemic syndromes, cardiogenic shock remains associated with significant morbidity and mortality.

METHODS

Patients who presented within 6 h of symptom onset were randomized to four treatment strategies: 1) streptokinase plus subcutaneous heparin; 2) streptokinase plus intravenous heparin; 3) accelerated recombinant tissue-type plasminogen activator (rt-PA) plus intravenous heparin; or 4) streptokinase and rt-PA plus intravenous heparin. The primary end point was 30-day all-cause mortality.

RESULTS

Shock occurred in 2,972 patients (7.2%): 315 (11%) had shock on arrival, and 2,657 (89%) developed shock after hospital admission. Reinfarction occurred in 11% of patients who developed shock compared with 3% of patients without shock. The mortality rate was significantly higher in patients who presented with (57%) or developed (55%) shock than in those without shock (3%) (p < 0.001). Shock developed significantly less frequently in patients receiving rt-PA. There were fewer deaths in patients who presented with shock and were treated with streptokinase plus intravenous heparin or who developed shock and were treated with streptokinase plus subcutaneous heparin. Patients who developed shock had a significantly lower 30-day mortality rate if angioplasty was performed.

CONCLUSIONS

Because cardiogenic shock occurred most often after admission and with recurrent ischemia and reinfarction, recognizing signs of incipient shock may improve outcome. Fewer patients treated with rt-PA developed shock, yet those developing shock had the same high mortality rate as those presenting with shock, regardless of treatment. Only angioplasty was associated with a significantly lower mortality rate.