Intraaortic balloon counterpulsation enhances coronary thrombolysis induced by intravenous administration of a thrombolytic agent

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.

Clinical outcomes of the intra-aortic balloon pump for resuscitated patients with acute myocardial infarction complicated by cardiac arrest

BACKGROUND

The aim of this study was to investigate the clinical effects of intra-aortic balloon pump (IABP) in patients who received cardiopulmonary resuscitation (CPR) before procedure.

METHODS AND RESULTS

Between November 2005 and April 2014, 49,542 patients were enrolled in a prospective cohort study for acute myocardial infarction (AMI) in Korea (KAMIR). CPR was performed in 1700 patients with cardiac arrest. Patients were excluded from the study if they had not undergone a coronary angiogram, if extracorporeal membrane oxygenation or thrombolysis was performed, and if mechanical complications presented. The primary end point was 1-month all-cause mortality. A total of 883 patients in the IABP group and 476 in the control group were included. During the 1-month follow-up, all-cause death occurred in 749 patients (55.1%). The IABP group was predominantly male and had a higher prevalence of ST-segment elevation MI and a higher risk of coronary lesions including left main disease and three-vessel disease. Glycoprotein IIb/IIIa inhibitor was administered less in the non-IABP group. In the total population, the IABP group had worse outcomes in terms of mortality rates after multivariate analysis [hazard ratio (HR) 1.22, 95% confidence interval (CI) 1.02-1.47, p=0.034] without increasing the incidence of recurrent MI, stroke, and major bleeding. After propensity matching with a pair of 452 patients, no significant differences were observed in baseline characteristics or clinical outcomes (HR 1.21, 95% CI 0.93-1.57, p=0.158).

CONCLUSION

The use of IABP did not show clinical benefits in patients with AMI complicated by severe cardiogenic shock after propensity matching analysis.

Cardiogenic Shock: Background, Shock Trial/Registry, Evolving Data, Changing Survival, Best Medical Therapy

Cardiogenic shock remains associated with unacceptably high mortality, but recent improvements with early revascularization, continued support with pharmacologic agents, and use of an intra-aortic balloon pump have led to improvements in the rate of mortality. Timely intervention with cardiac surgery in patients with mechanical complications, 3-vessel disease, and left main disease is beneficial. Continued research and ever-improving understanding of this once deadly condition have helped further in improving prognosis. Cutting-edge technologies, such as myocyte cell implantation and the use of a cooling system, will help in pushing the boundaries farther.

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.

What is the evidence for IABP in STEMI with and without cardiogenic shock?

Intraaortic balloon pump (IABP) is the most widely used left ventricular support device in a variety of indications. This review focuses on the current literature and discusses the evidence of IABP in ST-elevation myocardial infarction (STEMI) with and without cardiogenic shock. In high-risk STEMI patients without cardiogenic shock several randomized clinical trials have been performed. The majority of the studies could not demonstrate an efficacy benefit for IABP as adjunctive therapy in comparison to standard treatment alone. Hence, recent meta-analyses could not reveal diverging mortality rates at a higher incidence of stroke and major bleedings with IABP use independent of the type of reperfusion therapy. IABP in STEMI patients with cardiogenic shock is recommended according to current American College of Cardiology/American Heart Association (AHA/ACC) and European Society of Cardiology (ESC) guidelines. In recent meta-analyses, IABP in cardiogenic shock complicated by STEMI has been shown to be associated with decreased mortality. However, these beneficial effects are limited to patients treated with thrombolysis, whereas in patients undergoing mechanical revascularization IABP therapy is associated with an increase in mortality. Nevertheless, these data only arise from prospective and retrospective cohort studies, as up to date only one very small randomized clinical trial has been completed. In summary, in high-risk STEMI patients without cardiogenic shock, current data do not support the use of IABP and should only be considered as a standby and bailout strategy if patients develop haemodynamic instability. Current data on IABP in patients with cardiogenic shock complicated by STEMI are scarce and highly limited due to the nonrandomized design of previous trials. However, according to current AHA/ACC and ESC guidelines its use is recommended. Although recent meta-analyses challenge current AHA/ACC/ESC guidelines, adequately powered randomized studies are needed to elucidate the role of IABP in patients with acute myocardial infarction complicated by cardiogenic shock.

Guideline adjudicated fibrinolytic failure: incidence, findings, and management in a contemporary clinical trial

BACKGROUND

Rescue percutaneous coronary intervention (PCI) is efficacious after clinical failure of fibrinolytic therapy and is recommended for those with persistent ischemia, hemodynamic, or electrical instability. We sought to describe the frequency of fibrinolytic failure (rescue eligibility) as well as the patient characteristics associated with rescue eligibility, rescue referral, and PCI.

METHODS AND RESULTS

Eligibility, indication, and referral for guideline-based rescue PCI were adjudicated in 221 patients enrolled in the WEST trial. WEST treated patients at earliest medical contact and used a tenectaplase/enoxaparin regimen. Ninety patients (41%) were adjudicated with acute myocardial infarction as rescue eligible of whom 68 were referred for rescue PCI. Baseline characteristics did not predict rescue eligibility or referral. Emergency angiography before PCI performed a median of 82 minutes (interquartile range 50-99) after rescue referral showed TIMI flow grade 2 or 3 in 34 (50%). Percutaneous coronary intervention was adjudicated as successful in 58 of 60 attempts. Procedures began approximately 45 minutes sooner in patients initially admitted to PCI-capable hospitals. Compared to those with clinically successful fibrinolytic therapy, rescue eligible patients demonstrated higher median peak creatine phosphokinase (1889 [1243-3746] vs 999 [440-2048], P < .01) and 30-day median NT-proBNP levels (748 [391-1916] vs 431 [153-1016], P < .01).

CONCLUSIONS

Rescue eligibility determined by guideline criteria is common after contemporary fibrinolysis and is not predicted by conventional baseline characteristics. Half of rescue-referred patients are patent at angiography: although contemporary PCI success rates are high, rescue eligibility is associated with larger infarctions.

Cardiogenic shock: treatment

The treatment of cardiogenic shock complicating the acute coronary syndromes consists of medical therapy, percutaneous revascularization procedures, cardiac surgery, and the implantation of devices. Medical therapy is limited to different positive inotropic and vasoactive drugs, without any firm evidence of survival benefit using these drugs. Several new pharmacologic compounds are at different stages of clinical research, but are not yet routinely approved for the treatment of cardiogenic shock. The only evidence-based therapy with proven survival benefit is timely revascularization. Intra-aortic balloon pump counterpulsation maintains its central role as supportive treatment in cardiogenic shock patients. Anecdotal evidence is available about the use of ventricular assist devices, cardiac resynchronization therapy, and emergent heart transplantation.

Results of primary percutaneous coronary intervention in a consecutive group of patients with acute ST elevation myocardial infarction at a tertiary Australian centre

BACKGROUND

Multicentre randomized controlled trials (RCT) of primary percutaneous coronary intervention (PCI) for ST elevation myocardial infarction (STEMI) have consistently shown lower mortality compared with fibrinolysis, if carried out in a timely manner. Although primary PCI is now standard of care in many centres, it remains unknown whether results from RCT of selected patients are generalizable to a 'real-world' Australian setting. The primary goal of this study was to evaluate whether a strategy of routine invasive management for patients with STEMI can achieve 30-day and 12-month mortality rates comparable with multicentre RCT. Secondary goals were to determine 30-day mortality rates in prespecified high-risk subgroups, and symptom-onset- and door-to-balloon-inflation times.

METHODS

A retrospective observational study of 189 consecutive patients treated with primary PCI for STEMI in a single Australian centre performing PCI for acute STEMI.

RESULTS

All-cause mortality was 6.9% at 30 days, and 10.4% at 12 months. Mortality in patients presenting without cardiogenic shock was low (2.4% at 30 days; 5.0% at 12 months), whereas 12-month mortality in patients with shock was higher, particularly in the elderly (29.4% for patients <75 years; 85.7% for patients > or =75 years, P = 0.01). Symptom-onset-to-balloon-inflation time was < or =4 h in 56% of patients (median 231 min); however, a door-to-balloon time of <90 min was achieved in only 20% (median 133 min).

CONCLUSION

Mortality and symptom-onset-to-balloon-inflation times reported in RCT of primary PCI for STEMI are generalizable to 'real-world' Australian practice; however, further efforts to reduce door-to-balloon times are required.

Inverse relation between diastolic blood pressure and long-term outcomes in patients undergoing pharmacoinvasive therapy for myocardial infarction: the J-shaped relation in the contemporary era of revascularisation

OBJECTIVE

In the thrombolytic era, it was reported that in the presence of significant coronary stenosis, lowering diastolic blood pressure (DBP) below a critical threshold would result in a paradoxical increase in the occurrence of myocardial infarction (MI). We sought to re-evaluate this J-shaped relation in the era of pharmacoinvasive therapy.

METHODS

A total of 182 patients who underwent early (<1 week, mean 2.3 days) coronary angioplasty after thrombolysis were analysed.

RESULTS

Thrombolytic agents (streptokinase in 60%, tissue plasminogen activator in 40%) were administered in an average door-to-needle time of 66 min (<=30 min in 43 [24%] patients). A thrombolysis in myocardial infarction (TIMI) 3 flow was achieved in 56% of patients after thrombolysis, and it was enhanced to 92% after angioplasty. During an average follow-up period of 26 +/-13 months, the adverse event (death, re-MI, target vessel revascularisation or stroke) rate was 21%. Older age, low systolic blood pressure and DBP, fast heart rate, high creatine kinase, hypercholesterolaemia, thrombus-laden lesion, baseline TIMI 0-2 flow were associated with higher occurrence of adverse events. After adjusting for the differing clinical and procedural factors, low DBP (odds ratio 1.10, 95% confidence interval 1.01-1.20, P = 0.041), fast heart rate (odds ratio 1.08, 95% confidence interval 1.02-1.14, P = 0.008) and anterior MI (odds ratio 18.98, 95% confidence interval 2.13-169.19, P = 0.008) were all independent predictors of long-term adverse rate occurrence.

CONCLUSIONS

A low DBP is an independent predictor of long-term adverse event rates in patients undergoing routine early coronary angioplasty after thrombolysis. This suggests that excessive lowering of DBP may not be desirable before complete revascularisation.

Interhospital transfer for early revascularization in patients with ST-elevation myocardial infarction complicated by cardiogenic shock--a report from the SHould we revascularize Occluded Coronaries for cardiogenic shocK? (SHOCK) trial and registry

BACKGROUND

Early revascularization (ERV) in patients with ST-elevation myocardial infarction (STEMI) and cardiogenic shock (CS) reduces mortality rates. Patients admitted to hospitals without revascularization capability have high mortality rates and are not often transferred for ERV.

METHODS

Transfer and direct-admit patients with STEMI from the SHOCK Trial and Registry with left ventricular failure (N = 969) were analyzed to determine benefit of ERV in transfer patients.

RESULTS

Transfer patients (46%) were younger and less likely to have prior hypertension, myocardial infarction, and heart failure. They received more aggressive treatment, were revascularized later after CS (median 7.3 vs 3.9 hours, P = .0002), and had similar adjusted inhospital mortality compared with direct-admit patients (55% vs 56%). Inhospital mortality was lower in ERV than no/late revascularization (41% vs 53%, P = .017 for transfer patients; 55% vs 71%, P = .0003 for direct-admit patients). Multiple logistic regression showed that inhospital mortality was associated with age (odds ratio [OR] 1.50 per decade increase, 95% CI 1.31-1.73, P < .0001), mean arterial pressure (OR 0.98 per 1 mm Hg increase, 95% CI 0.97-0.99, P < .0001), fibrinolysis before CS (OR 0.65, 95% CI 0.52-0.96, P = .040), and ERV (OR 0.70, 95% CI 0.52-0.96, P = .028), but not transfer admission (OR 1.23, 95% CI 0.86-1.74, P = .26).

CONCLUSIONS

Despite longer time to treatment, transfer patients are a selected population with similar adjusted inhospital mortality and ERV benefit as direct-admit patients. Selected patients with STEMI and CS admitted to hospitals without revascularization capability should be transferred to centers with revascularization capability for immediate angiography.

Intra-aortic balloon counterpulsation

Intra-aortic balloon counterpulsation (IABP) is sometimes used in critically ill patients with cardiac disease. By increasing diastolic arterial pressure and decreasing systolic pressure, it reduces left ventricular afterload. IABP may be beneficial in subjects with cardiogenic shock, mechanical complications of myocardial infarction, intractable ventricular arrhythmias, or advanced heart failure or those who undergo "high-risk" surgical or percutaneous revascularization, but the evidence to support its use in these patient groups is largely observational. Contraindications to IABP include severe peripheral vascular disease as well as aortic regurgitation, dissection, or aneurysm. The potential benefits of IABP must be weighed against its possible complications (bleeding, systemic thromboembolism, limb ischemia, and, rarely, death).

Therapeutic strategies for cardiogenic shock, 2006

Cardiogenic shock, a devastating consequence of acute myocardial infarction, is associated with extremely high mortality. Treatment strategies should focus on prompt reperfusion and hemodynamic support. The primary approach for therapy is emergent angiography and revascularization using percutaneous coronary intervention or coronary artery bypass surgery, with the assistance of intra-aortic balloon pump counterpulsation. Several adjunctive pharmacologic agents, particularly inotropic drugs and vasopressors, are also helpful for hemodynamic support. However, these agents have not been shown to provide a survival benefit, and their use is primarily based on clinical experience. Since our last publication, several important advances have been made in the understanding and treatment of cardiogenic shock. Recent evidence suggests that a systemic inflammatory response, including the upregulation of inducible nitric oxide synthase, complement activation, and an inflammatory cytokine cascade, play a role in the development of cardiogenic shock. Newer therapeutic strategies, including C5 inhibitors and nitric oxide synthase inhibitors, are being combined with traditional strategies, such as inotropic agents, vasopressors, and circulatory assist, to treat cardiogenic shock.

Thrombolysis and Counterpulsation to Improve Survival in Myocardial Infarction Complicated by Hypotension and Suspected Cardiogenic Shock or Heart Failure: Results of the TACTICS Trial

BACKGROUND

Sustained hypotension, cardiogenic shock, and heart failure all imply a poor prognosis in acute myocardial infarction (MI). We assessed the benefit of adding 48 hours of intra-aortic balloon counterpulsation (IABP) to standard treatment for MI, in an international trial among hospitals without primary angioplasty capabilities.

METHODS

We randomized 57 patients with MI complicated by sustained hypotension, possible cardiogenic shock, or possible heart failure to receive either fibrinolytic therapy and IABP or fibrinolysis alone. The primary end point was all-cause mortality at 6 months.

RESULTS

In all, IABP was inserted in 27 of 30 assigned patients a median 30 minutes after fibrinolysis began and continued for a median 34 hours. Of the 27 patients assigned to fibrinolysis alone, 9 deteriorated such that IABP was required. The IABP group was at slightly higher risk at baseline, but the incidence of the primary end point did not differ significantly between groups (34% for combined treatment versus 43% for fibrinolysis alone; adjusted P = 0.23). Patients with Killip class III or IV showed a trend toward greater benefit from IABP (6-month mortality 39% for combined therapy versus 80% for fibrinolysis alone; P = 0.05).

CONCLUSIONS

While early IABP use was not associated with a definitive survival benefit when added to fibrinolysis for patients with MI and hemodynamic compromise in this small trial, its use suggested a possible benefit for patients with the most severe heart failure or hypotension. ABBREVIATED ABSTRACT: We assessed the benefit of adding 48 hours of intra-aortic balloon counterpulsation to fibrinolytic therapy among 57 patients with acute myocardial infarction complicated by sustained hypotension, possible cardiogenic shock, or possible heart failure. The primary end point, mortality at 6 months, did not differ between groups (34% for combined treatment versus 43% for fibrinolysis alone [n = 27]; adjusted P = 0.23), although patients with Killip class III or IV did show a trend toward greater benefit from IABP (39% for combined therapy versus 80% for fibrinolysis; P = 0.05).

ACCELERATED REPERFUSION OF POORLY PERFUSED RETINAL AREAS IN CENTRAL RETINAL ARTERY OCCLUSION AND BRANCH RETINAL ARTERY OCCLUSION AFTER A SHORT TREATMENT WITH ENHANCED EXTERNAL COUNTERPULSATION

BACKGROUND

To date, no satisfactory therapy has become available for patients with acute central retinal artery occlusion (CRAO) or branch retinal artery occlusion (BRAO). Enhanced external counterpulsation (EECP) is a new noninvasive procedure that increases perfusion of inner organs. In the current study, the authors measured the impact of EECP on reperfusion in ischemic retinal tissue.

METHODS

In a prospective, randomized study, 20 patients with CRAO or BRAO were included. Ten patients were given hemodilution therapy and 2 hours of EECP, and 10 patients were given regular hemodilution therapy only. Quantification of changes in retinal perfusion was carried out by means of scanning laser Doppler flowmetry (in arbitrary units).

RESULTS

Enhanced external counterpulsation caused no observable adverse events. A significant increase in perfusion occurred immediately after EECP in the ischemic retinal areas (57 +/- 19 arbitrary units versus 99 +/- 14 arbitrary units). In contrast, no change was measured in the group not treated with EECP (83 +/- 19 arbitrary units versus 89 +/- 44 arbitrary units). Forty-eight hours later, a significant increase in perfusion could be shown in the ischemic retina of both groups, and no significant difference of perfusion was found between the two groups any longer.

CONCLUSION

The current study suggests that EECP could be a clinically useful and safe procedure in patients with CRAO or BRAO to accelerate recovery of perfusion in ischemic retinal areas.

Therapeutic Strategies for Cardiogenic Shock

Cardiogenic shock is a devastating consequence of acute myocardial infarction; it is associated with an extremely high mortality. Treatment strategies should be focused on prompt reperfusion, as well as hemodynamic support. The optimal approach for therapy is emergent angiography and revascularization using percutaneous coronary intervention or coronary artery bypass surgery, with the assistance of intra-aortic balloon pump counterpulsation. Several adjunctive pharmacologic agents, particularly inotropic drugs and vasopressors, are also helpful for hemodynamic support. However, these agents have not been shown to provide a survival benefit, and their use is primarily based on clinical experience.

Engineering design of optimal strategies for blood clot dissolution

Blood clots form under hemodynamic conditions and can obstruct flow during angina, acute myocardial infarction, stroke, deep vein thrombosis, pulmonary embolism, peripheral thrombosis, or dialysis access graft thrombosis. Therapies to remove these clots through enzymatic and/or mechanical approaches require consideration of the biochemistry and structure of blood clots in conjunction with local transport phenomena. Because blood clots are porous objects exposed to local hemodynamic forces, pressure-driven interstitial permeation often controls drug penetration and the overall lysis rate of an occlusive thrombus. Reaction engineering and transport phenomena provide a framework to relate dosage of a given agent to potential outcomes. The design and testing of thrombolytic agents and the design of therapies must account for (a) the binding, catalytic, and systemic clearance properties of the therapeutic enzyme; (b) the dose and delivery regimen; (c) the biochemical and structural aspects of the thrombotic occlusion; (d) the prevailing hemodynamics and anatomical location of the thrombus; and (e) therapeutic constraints and risks of side effects. These principles also impact the design and analysis of local delivery devices.

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.

Percutaneous coronary intervention for cardiogenic shock in the SHOCK Trial Registry

BACKGROUND

The SHOCK Registry prospectively enrolled patients with cardiogenic shock complicating acute myocardial infarction in 36 multinational centers.

METHODS

Cardiogenic shock was predominantly attributable to left ventricular pump failure in 884 patients. Of these, 276 underwent percutaneous coronary intervention (PCI) after shock onset and are the subject of this report.

RESULTS

The majority (78%) of patients undergoing angiography had multivessel disease. As the number of diseased arteries rose from 1 to 3, mortality rates rose from 34.2% to 51.2%. Patients who underwent PCI had lower in-hospital mortality rates than did patients treated medically (46.4% vs 78.0%, P < .001), even after adjustment for patient differences and survival bias (P = .037). Before PCI, the culprit artery was occluded (Thrombolysis In Myocardial Infarction grade 0 or 1 flow) in 76.3%. After PCI, the in-hospital mortality rate was 33.3% if reperfusion was complete (grade 3 flow), 50.0% with incomplete reperfusion (grade 2 flow), and 85.7% with absent reperfusion (grade 0 or 1 flow) (P < .001).

CONCLUSIONS

This prospective, multicenter registry of patients with acute myocardial infarction complicated by cardiogenic shock is consistent with a reduction in mortality rates as the result of percutaneous coronary revascularization. Coronary artery patency was an important predictor of outcome. Measures to promote early and rapid reperfusion appear critically important in improving the otherwise poor outcome associated with cardiogenic shock.

Recent magnitude of and temporal trends (1994-1997) in the incidence and hospital death rates of cardiogenic shock complicating acute myocardial infarction: the second national registry of myocardial infarction

BACKGROUND

Limited recent data are available to describe the magnitude of, and temporal trends in, the incidence and case-fatality rates associated with cardiogenic shock complicating acute myocardial infarction. The purpose of this study was to examine recent (1994-1997) trends in the incidence of, and hospital death rates from, cardiogenic shock complicating acute myocardial infarction from a large, multihospital national perspective.

METHODS

An observational study was performed of 426,253 patients hospitalized with acute myocardial infarction in 1662 hospitals throughout the United States between 1994 and 1997.

RESULTS

The incidence rates of cardiogenic shock averaged 6.2%. There was evidence for a slight decline in these rates between 1994 (6.6%) and 1997 (6.0%). Results of a multivariable regression analysis controlling for factors that might affect the risk of development of cardiogenic shock indicated that patients hospitalized in more recent years were at significantly lower risk for shock. Patients with shock had a markedly increased risk for dying during hospitalization compared with patients not having shock (74% vs 10%). Significant, albeit small, absolute differences were observed in the risk of dying after cardiogenic shock over time (76% dying in 1997, 72% dying in 1994). These improving trends were magnified, however, after potentially confounding prognostic factors were controlled: patients having shock in 1997 were at approximately one fifth lower risk of dying (odds ratio 0.79, 95% confidence interval 0.71-0.87) than those hospitalized in 1994.

CONCLUSIONS

Our findings indicate a slight decline in the incidence rates of cardiogenic shock and improving trends in the hospital survival of patients with shock. Despite these trends, it remains of considerable importance to prevent this clinical syndrome, given its high lethality.

Medical treatment for acute coronary syndromes

The medical treatment of acute coronary syndromes with thrombolytic, antithrombin, and antiplatelet agents is a major area of research and a vast topic for clinical review. This review summarizes important recent findings on the background of existing pathological and clinical knowledge to provide an understanding of the basis of current therapy and the new therapies that are likely to be introduced in the near future. Current controversies regarding the management of these conditions and the choice between medical, interventional, and combined strategies in different situations are also discussed.

Cardiogenic shock complicating acute myocardial infarction--etiologies, management and outcome: a report from the SHOCK Trial Registry. SHould we emergently revascularize Occluded Coronaries for cardiogenic shocK?

OBJECTIVES

This SHOCK Study report seeks to provide an overview of patients with cardiogenic shock (CS) complicating acute myocardial infarction (MI) and the outcome with various treatments. The outcome of patients undergoing revascularization in the SHOCK Trial Registry and SHOCK Trial are compared.

BACKGROUND

Cardiogenic shock is the leading cause of death in patients hospitalized for acute MI. The randomized SHOCK Trial reported improved six-month survival with early revascularization.

METHODS

Patients with CS complicating acute MI who were not enrolled in the concurrent randomized trial were registered. Patient characteristics were recorded as were procedures and vital status at hospital discharge.

RESULTS

Between April 1993 and August 1997, 1,190 patients with CS were registered and 232 were randomized in the SHOCK Trial. Predominant left ventricular failure (78.5%) was most common, with isolated right ventricular shock in 2.8%, severe mitral regurgitation in 6.9%, ventricular septal rupture in 3.9% and tamponade in 1.4%. In-hospital Registry mortality was 60%, with ventricular septal rupture associated with a significantly higher mortality (87.3%) than all other categories (p < 0.01). The risk profile and mortality were lower for Registry patients who were managed with thrombolytic therapy and/or intra-aortic balloon counter-pulsation, coronary angiography, angioplasty and/or coronary artery bypass surgery. After adjusting for these differences, the extent to which survival was improved with early revascularization was similar to that observed in the randomized SHOCK Trial.

CONCLUSIONS

In this prospective Registry the etiology of CS was a mechanical complication in 12%. The similarity of the beneficial treatment effect in patients undergoing early revascularization in the SHOCK Trial Registry and SHOCK Trial provides strong support for the generalizability of the SHOCK Trial results.

Cardiogenic shock complicating acute coronary syndromes

Cardiogenic shock remains the major cause of death among patients with all types of acute coronary syndromes. Thus, there is a growing interest in the identification of patients who are at risk for developing cardiogenic shock, in the exploration of different therapeutic approaches to preventing its development, and in the improvement of outcome when it occurs. This article reviews the aetiology and pathophysiology of cardiogenic shock, its epidemiology, its treatment (including pharmaceutical agents, counterpulsation, and revascularisation), and its outcome. Algorithms are presented that predict its occurrence in both ST-segment-elevation myocardial infarction and unstable angina or non-ST-elevation myocardial infarction, and that predict its mortality in patients with ST-segment-elevation acute myocardial infarction. Such new areas as metabolic therapy and glycoprotein IIb/IIIa inhibitors are discussed, as are the economic implications of shock.

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.

[Reperfusion therapy and mechanical circulatory support in patients in cardiogenic shock]

Cardiogenic shock is a state of inadequate tissue perfusion due to cardiac dysfunction, which is most commonly caused by acute myocardial infarction. The pathophysiology of cardiogenic shock is characterized by a downward spiral: ischemia causes myocardial dysfunction, which, in turn, augments the ischemic damage and the energetical imbalance. With conservative therapy, mortality rates for patients with cardiogenic shock are frustratingly high reaching more than 80%. Additional thrombolytic therapy has not been shown to significantly improve survival in such patients. Emergency cardiac catheterization and coronary angioplasty, however, seem to improve the outcome in shock-patients, which most probably is due to rapid and complete revascularization generally reached by angioplasty. In addition to interventional therapy with rapid coronary revascularization, the use of mechanical circulatory support may interrupt the vicious cycle in cardiogenic shock by stabilizing hemodynamics and the metabolic situation. Different cardiac assist devices are available for cardiologists and cardiac surgeons: 1. intraaortic balloon counterpulsation (IABP), 2. implantable turbine-pump (Hemopump), 3. percutaneous cardiopulmonary bypass support (CPS), 4. right heart, left heart, or biventricular assist devices placed by thoracotomy, and 5. intra- and extrathoracic total artificial hearts. Since percutaneous application is possible with IABP, Hemopump and CPS, these devices are currently used in interventional cardiology. The basic goals of the less invasive intraaortic balloon counterpulsation (IABP; Figure 1) are to stabilize circulatory collapse, to increase coronary perfusion and myocardial oxygen supply, and to decrease left ventricular workload and myocardial oxygen demand (Figure 2). Since the advent of percutaneous placement, IABP has been used by an increasing number of institutions (Figure 3). In addition to cardiogenic shock, the system may be of use in a variety of other indications in the catheterization laboratory and intensive care unit, including weaning from percutaneous cardiopulmonary bypass, in ischaemic left ventricular failure, in unstable angina, in high risk PTCA, and in prophylactic support in patients with myocardial infarction and successful revascularization. Animal experimental data showed that IABP may improve success of thrombolysis and recent clinical data suggest that survival is enhanced and transfer for revascularization is facilitated when patients with myocardial infarction and cardiogenic shock undergo thrombolysis and IABP rather than thrombolysis alone. A lot of studies had demonstrated before, that combined use of counterpulsation and revascularization therapy (i.e. coronary bypass surgery or angioplasty) may improve prognosis in patients with myocardial infarction complicated by cardiogenic shock (Table 1). In such patients, early treatment with IABP is most important: Multivariate analysis identified early IABP-support with a duration of shock to IABP-treatment of > or = 4 hours as an independent predictor of a positive short-term outcome. In shock-patients with postinfarction ventricular septal defect, IABP provides a marked hemodynamic improvement, and a significant decrease in shunt-flow (Figure 5). However, despite initial stabilization with IABP, such patients need immediate surgical repair of the septal defect to avoid hemodynamic deterioration. The rate of complications related to percutaneous IABP was significantly attenuated by employing catheters of reduced size. Using 9.5-F catheters, a long duration of counterpulsation emerged as the most significant factor associated with complications. In our hospital, those patients with 9.5-F catheters in whom counterpulsation did not exceed 48 hours had a low complication rate of 3.9%. The Hemopump is a catheter-mounted transvalvular left ventricular assist device intended for surgical placement via the femoral artery (Figures 6 and 7). (ABSTRACT TRUNCATED)

Early revascularization in acute myocardial infarction complicated by cardiogenic shock. SHOCK Investigators. Should We Emergently Revascularize Occluded Coronaries for Cardiogenic Shock

BACKGROUND

The leading cause of death in patients hospitalized for acute myocardial infarction is cardiogenic shock. We conducted a randomized trial to evaluate early revascularization in patients with cardiogenic shock.

METHODS

Patients with shock due to left ventricular failure complicating myocardial infarction were randomly assigned to emergency revascularization (152 patients) or initial medical stabilization (150 patients). Revascularization was accomplished by either coronary-artery bypass grafting or angioplasty. Intraaortic balloon counterpulsation was performed in 86 percent of the patients in both groups. The primary end point was mortality from all causes at 30 days. Six-month survival was a secondary end point.

RESULTS

The mean age of the patients was 66+/-10 years, 32 percent were women and 55 percent were transferred from other hospitals. The median time to the onset of shock was 5.6 hours after infarction, and most infarcts were anterior in location. Ninety-seven percent of the patients assigned to revascularization underwent early coronary angiography, and 87 percent underwent revascularization; only 2.7 percent of the patients assigned to medical therapy crossed over to early revascularization without clinical indication. Overall mortality at 30 days did not differ significantly between the revascularization and medical-therapy groups (46.7 percent and 56.0 percent, respectively; difference, -9.3 percent; 95 percent confidence interval for the difference, -20.5 to 1.9 percent; P=0.11). Six-month mortality was lower in the revascularization group than in the medical-therapy group (50.3 percent vs. 63.1 percent, P=0.027).

CONCLUSIONS

In patients with cardiogenic shock, emergency revascularization did not significantly reduce overall mortality at 30 days. However, after six months there was a significant survival benefit. Early revascularization should be strongly considered for patients with acute myocardial infarction complicated by cardiogenic shock.

Reperfusion therapy in cardiogenic shock complicating acute myocardial infarction

The most frequent cause of cardiogenic shock complicating acute myocardial infarction is extensive myocardial damage involving a relevant amount of myocardium. Treatment is aimed at support for the circulation with the use of drugs and mechanical devices and at restoration of perfusion to the ischemic myocardium as soon as possible. Therefore, emergency coronary angiography is indicated in all patients. Coronary angioplasty is the first option in patients with suitable anatomy because it is the fastest available technique able to recanalize the infarct-related vessel. Stenting of the infarct artery must be considered because stent implantation has been shown to improve results in comparison with the balloon alone. Complete revascularization is likely to offer a better outcome in patients with multivessel disease. Coronary surgery is indicated as first-line intervention in patients who have a coronary anatomy not suitable for angioplasty; it may also serve to complete revascularization in patients with multivessel disease initially treated with emergency coronary angioplasty. In a hospital without facilities for emergency coronary interventions, mechanical circulatory support with an intra-aortic balloon pump should be instituted and thrombolysis started; then patients should be transferred immediately to a tertiary center to undergo coronary angiography and revascularization procedures, if needed. In patients not benefiting from this aggressive revascularization strategy who develop irreversible extensive myocardial damage, heart transplantation must be considered.

The use of intraaortic balloon counterpulsation as an adjunct to reperfusion therapy in cardiogenic shock

Modern coronary care unit interventions have not reduced the high mortality rate associated with cardiogenic shock due to acute myocardial infarction. Results with thrombolytic therapy have also been disappointing because of poor infarct artery patency rates in a low coronary flow state. Percutaneous transluminal coronary angioplasty appears to be a beneficial intervention, but the technique is not available at most hospitals. Intraaortic balloon counterpulsation provides temporary hemodynamic and clinical improvement in the majority of patients with cardiogenic shock. The use of intraaortic counterpulsation to augment patency rates with thrombolytic therapy or to stabilize patients for transfer to a hospital with angioplasty services appears to be a promising strategy for hospitals without an interventional cardiac catheterization laboratory.

Thrombolysis for acute myocardial infarction

Thrombolytic therapy has been a major advance in the management of acute myocardial infarction. Unfortunately, it continues to be underused or is administered later than is optimal. Thrombolytic therapy works by lysing infarct artery thrombi and achieving reperfusion, thereby reducing infarct size, preserving left ventricular function, and improving survival. The most effective thrombolytic regimens achieve angiographic epicardial infarct-artery patency in only approximately 50% of patients within 90 minutes. Bleeding requiring transfusion occurs in approximately 5% of patients and stroke in approximately 1.8% with these regimens, which include adjunctive aspirin and intravenous heparin. There are several ways in which reperfusion rates and thus patient outcomes might be improved, such as different dosing regimens of established agents; combinations of different agents; improved adjunctive therapy such as direct antithrombin agents, low-molecular-weight heparin, or glycoprotein IIb/IIIa receptor antagonists; or the development of novel thrombolytic agents with enhanced fibrin specificity, resistance to native inhibitors, or prolonged half-lives allowing bolus administration. All of these strategies are being tested in clinical trials. The best approach currently is to administer thrombolytic therapy as soon as possible to all patients without contraindications who present within 12 hours of symptom onset and have ST-segment elevation on the ECG or new-onset left bundle-branch block, unless an alternative reperfusion strategy is planned.

Use of intraaortic balloon counterpulsation in patients presenting with cardiogenic shock: observations from the GUSTO-I Study. Global Utilization of Streptokinase and TPA for Occluded Coronary Arteries

OBJECTIVES

We sought to examine the use, complications and outcomes with early intraaortic balloon counterpulsation (IABP) in patients presenting with cardiogenic shock complicating acute myocardial infarction and treated with thrombolytic therapy.

BACKGROUND

The use of IABP in patients with cardiogenic shock is widely accepted; however, there is a paucity of information on the use of this technique in patients with cardiogenic shock who are treated with thrombolytic therapy.

METHODS

Patients who presented within 6 h of chest pain onset were randomized to one of four thrombolytic regimens. Cardiogenic shock was not an exclusion criterion, and data for these patients were prospectively collected. Patients presenting with shock were classified into early IABP (insertion within one calendar day of enrollment) or no IABP (insertion on or after day 2 or never).

RESULTS

There were 68 (22%) IABP placements in 310 patients presenting with shock. Early IABP use occurred in 62 patients (20%) and none in 248 (80%). Most IABP use occurred in the United States (59 of 68 IABP placements) involving 32% of U.S. patients presenting with shock. Despite more adverse events in the early IABP group and more episodes of moderate bleeding, this cohort showed a trend toward lower 30-day and 1-year mortality rates.

CONCLUSIONS

IABP appears to be underutilized in patients presenting with cardiogenic shock, both within and outside the United States. Early IABP institution is associated with an increased risk of bleeding and adverse events but a trend toward lower 30-day and 1-year all-cause mortality.

Thrombolysis plus aortic counterpulsation: improved survival in patients who present to community hospitals with cardiogenic shock

OBJECTIVES

We sought to explore the potential benefit of combining intraaortic balloon counterpulsation (IABP) with thrombolysis for acute myocardial infarction (MI) complicated by cardiogenic shock.

BACKGROUND

In community hospitals, this condition is usually managed with thrombolysis alone.

METHODS

We reviewed the charts of 335 patients from two community hospitals who presented with acute MI and had cardiogenic shock between 1985 and 1995.

RESULTS

Of 46 patients who underwent thrombolysis within 12 h of acute infarction with confirmed cardiogenic shock, 27 underwent IABP and 19 did not. Age, systolic blood pressure with shock, pulmonary artery catheter use, pulmonary capillary wedge pressure and the incidence of diabetes mellitus and anterior MI did not differ between groups. Patients treated with IABP were somewhat more likely to have prior MI and had a significantly greater cardiac index (2.0 vs. 1.5 liters/min per m2, p = 0.04). Although no deaths occurred within 2 h of presentation, patients not treated with IABP tended to die earlier (6.8 +/- 5 vs. 23.8 +/- 19 h, p = 0.13). Patients treated with IABP had a significantly higher rate of community hospital survival (93% vs. 37%, p = 0.0002), and more of them were transferred for revascularization (85% vs. 37%). Of 30 patients transferred for revascularization, 27 underwent angioplasty or bypass surgery; hospital survival was 74%. Patients treated with IABP also had a significantly higher overall hospital and 1-year survival rate (67% vs. 32%, p = 0.019).

CONCLUSIONS

Survival may be enhanced and transfer for revascularization facilitated when community hospitals use both thrombolysis and IABP to treat patients with acute MI complicated by cardiogenic shock.

Effect of a mechanical vs a pharmacologic increase in aortic pressure on coronary blood flow and thrombolysis induced by IV administration of a thrombolytic agent

This study was designed to compare the effect of a mechanical vs a pharmacologic increase in BP on coronary artery blood flow and thrombolysis induced by IV administration of recombinant tissue plasminogen activator. We employed a canine model of coronary thrombosis induced by injection of radioactive blood clot in the left anterior descending coronary artery. Subsequently, all dogs underwent phlebotomy to decrease systolic BP to 75 mm Hg and this decreased coronary blood flow by 50%. BP was increased to 130 mm Hg by norepinephrine (NE) infusion or by inflation of a Fogarty catheter placed in the descending aorta. Interventions with NE or with a Fogarty balloon catheter increased coronary artery blood flow to similar values and rates of coronary thrombolysis were similar. However, cardiac output was significantly higher with NE. These results indicate coronary clot lysis is dependent on perfusion pressure and coronary blood flow, not cardiac output.

Aortic counterpulsation may improve late patency of the occluded coronary artery in patients with early failure of thrombolytic therapy

OBJECTIVES

Using a prospective, randomized design, we tested our hypothesis that the augmentation of diastolic pressure by intraaortic balloon counterpulsation (IABP) would improve the late patency of the occluded coronary artery in patients with early failure of thrombolytic therapy.

BACKGROUND

Rescue angioplasty is often performed in patients in whom thrombolysis has failed, although 30% to 60% of the infarct-related arteries that are closed early after thrombolytic therapy will open later with conservative therapy.

METHODS

The study included 45 patients in whom thrombolysis had failed, despite treatment with intravenous tissue-type plasminogen activator (alteplase 0.75 mg/kg body weight) delivered over 60 min within 12 h of the onset of symptoms. All patients underwent coronary angiography 60 min after initiation of thrombolytic therapy (baseline), and Thrombolysis in Myocardial Infarction (TIMI) grade 0, 1 or 2 flow was defined as failed thrombolysis. The patients were randomized to groups receiving IABP for 48 h (n = 23) or conservative therapy (n = 22, control subjects) at the end of cardiac catheterization. The late patency of the infarct-related artery, the primary end point of the study, was evaluated 3 weeks after myocardial infarction. Stenosis of the infarct-related artery was measured using a computer-assisted quantitative angiographic system in blinded manner. Data are expressed as mean value +/- SEM.

RESULTS

There was no difference with regard to the baseline value for TIMI flow grade between the groups. However, 3 weeks after myocardial infarction, the patients treated with IABP had a significantly higher frequency of TIMI flow grade 3, lower residual percent stenosis and larger minimal lumen diameter of the infarct-related artery than did the control subjects (74% vs. 32%, p < 0.05; 42 +/- 5% vs. 68 +/- 6%, p < 0.01; and 1.6 +/- 0.1 vs. 0.9 +/- 0.2 mm, p < 0.01, respectively).

CONCLUSIONS

These findings suggest that in patients with early failure of thrombolytic therapy, IABP may improve late patency of the occluded coronary artery, probably due to augmented perfusion pressure.

Computer simulation of systemic circulation and clot lysis dynamics during thrombolytic therapy that accounts for inner clot transport and reaction

BACKGROUND

We developed a computer model to predict lysis rates of thrombi for intravenous thrombolytic regimens based on the convective/diffusive penetration of reacting and adsorbing fibrinolytic species from the circulation into the proximal face of a dissolving clot.

METHODS AND RESULTS

Solution of a one-compartment plasma model provided the dynamic concentrations of fibrinolytic species that served as inlet conditions for stimulation of the one-dimensional spatiodynamics within a dissolving fibrin clot of defined composition. The model predicted the circulating levels of tissue plasminogen activator (TPA) and plasminogen levels found in clinical trials for various intravenous therapies. To test the model predictions under in vitro conditions, plasma clots were perfused with TPA (0.1 mumol/L) and plasminogen (1.0 mumol/L) delivered at constant permeation velocity of 0.1 or 0.2 mm/min. The model provided an accurate prediction of the measured lysis front movement. For TPA administration regimens used clinically, simulations predicted clot dissolution rates that were consistent with observed reperfusion times. For unidirectional permeation, the continual accumulation of adsorbing species at the moving lysis front due to prior rounds of solubilization and rebinding was predicted to provide for a marked concentration of TPA and plasmin and the eventual depletion of antiplasmin and macroglobulin in an advancing (approximately 0.25 mm thick) lysis zone.

CONCLUSIONS

Pressure-driven permeation greatly enhances and is a primary determinant of the overall rate of clot lysis and creates a complex local reaction environment at the plasma/clot interface. With simulation of reaction and transport, it becomes possible to quantitatively link the administration regimen, plasminogena activator properties, and thrombolytic outcome.

Optimizing coronary thrombolysis with i.v. administration of recombinant tissue plasminogen activator. Single bolus vs double bolus vs front-loading

This study was designed to compare the efficacy of coronary thrombolysis obtained with i.v. administration of three dose regimens of recombinant tissue plasminogen activator (rtPA). Although many studies have confirmed the efficacy of thrombolytic therapy in treatment of acute myocardial infarction, few prospective studies have been designed to determine which dose regimen optimizes the rate of coronary thrombolysis. A canine model was used. Coronary thrombosis was induced by injection of radioactive, autologous blood clots through a catheter placed in the left anterior descending coronary artery. Subsequently, 15 dogs were randomized into 3 groups of 5 dogs each. In group 1 dogs, 1.25 mg/kg of rtPA was administered i.v. as a bolus; in the group 2 dogs, 1.25 mg/kg of rtPA was administered over 60 min. The administration was "front loaded" so that 15% was administered as a bolus, 60% over 30 min, and 25% over 30 min; in group 3, 1.25 mg/kg of rtPA was divided into two i.v. boluses and administered 15 min apart. Coronary thrombolysis was assessed with a gamma camera. Despite differences in rate of administration of rtPA, at 15, 30, and 90 min after onset of treatment, extent of clot lysis was similar between groups. These results indicate that despite differences in dose regimens, rates of thrombolysis are similar when i.v. rtPA is relatively rapidly administered. Further, the similar rates of clot lysis over time between groups suggest both an effective upper limit to the dose-thrombolytic rate relationship and relatively high, sustained steady-state plasma concentrations of rtPA.

An increase in low aortic pressure increases coronary artery flow and coronary thrombolysis induced by intravenous administration of recombinant tissue plasminogen activator

PURPOSE

Our study investigated the effects of an increase in aortic pressure, induced by norepinephrine (NE) administration on coronary artery flow in a clotted artery, and rate of coronary thrombolysis induced by intravenous (i.v.) administration of recombinant tissue plasminogen activator (rtPA).

METHODS

A canine model of coronary thrombosis, induced by intracoronary injection of radioactive autologous blood clots, was used to test the hypothesis that an increase in aortic blood pressure will increase coronary artery flow and the rate of clot lysis induced by i.v. administration of rtPA.

RESULTS

After clot injection, 11 dogs were phlebotomized to decrease systolic aortic pressure to 75 mm Hg. Subsequently, .25 mg/kg of rtPA was administered intravenously over two 15-minute intervals, one during hypotension, and the other after NE infusion had increased systolic blood pressure to 130 mm Hg. In six dogs the hypotensive condition was studied first, and in five dogs the NE-induced normotensive condition was studied first. In all dogs, coronary artery flow and the rate of clot lysis were significantly increased in the normotensive condition.

CONCLUSIONS

These results indicate that an increase in a low coronary artery perfusion pressure may enhance coronary artery flow and the rate of thrombolysis.

Current spectrum of cardiogenic shock and effect of early revascularization on mortality. Results of an International Registry. SHOCK Registry Investigators

BACKGROUND

Cardiogenic shock remains the leading cause of death of patients hospitalized with acute myocardial infarction (MI). This study was conducted to examine (1) the current spectrum of cardiogenic shock, (2) the proportion of patients who are potential candidates for a trial of early revascularization, and (3) the apparent impact of early revascularization on mortality.

METHODS AND RESULTS

Nineteen participating centers in the United States and Belgium prospectively registered all patients diagnosed with cardiogenic shock. Two hundred fifty-one patients were registered. The mean age was 67.5 +/- 11.7 years, and 43% were women. Acute mitral regurgitation or ventricular septal rupture was the cause of shock in 8%. Concurrent conditions contributing to the development of shock were noted in 5%, and 2% had isolated right ventricular shock. Among the remaining 214 patients, nonspecific findings on the ECG associated with "nontransmural" MI were seen in 14%. The median time to shock diagnosis after MI was 8 hours. The overall in-hospital mortality was 66%. Patients clinically selected to undergo cardiac catheterization were significantly younger and had a lower mortality than those not selected (51% versus 85%, P < .0001) even if they were not revascularized (58%). Mortality for patients undergoing percutaneous transluminal coronary angioplasty (PTCA) was 60% (n = 55) and 19% (n = 16) for coronary artery bypass graft surgery (CABG). Sixty percent (n = 150) of registered patients were judged eligible for a trial of early revascularization. Trial-eligible patients were significantly younger (65.4 +/- 11.0 versus 70.6 +/- 11.9 years, P < .001), had an earlier median time to shock onset after MI (6.5 versus 17.5 hours, P = .003), and had lower mortality (62% versus 73%, P = .077) than ineligible patients.

CONCLUSIONS

Patients diagnosed with cardiogenic shock complicating acute MI are a heterogeneous group. Those eligible for a trial of early revascularization tended to have lower mortality. Patients selected to undergo cardiac catheterization had lower mortality whether or not they were revascularized. Emergent PTCA and CABG are promising treatment modalities for cardiogenic shock, but biased case selection for treatment may confound the data. Whether PTCA and CABG reduce mortality and which patient subgroups benefit most remain to be determined in a randomized clinical trial.