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

Comparative efficacy and safety of reperfusion therapy with fibrinolytic agents in patients with ST-segment elevation myocardial infarction: a systematic review and network meta-analysis

BACKGROUND

Fibrinolytic therapy offers an alternative to mechanical reperfusion for ST-segment elevation myocardial infarction (STEMI) in settings where health-care resources are scarce. Comprehensive evidence comparing different agents is still unavailable. In this study, we examined the effects of various fibrinolytic drugs on clinical outcomes.

METHODS

We did a network meta-analysis based on a systematic review of randomised controlled trials comparing fibrinolytic drugs in patients with STEMI. Several databases were searched from inception up to Feb 28, 2017. We included only randomised controlled trials that compared fibrinolytic agents as a reperfusion therapy in adult patients with STEMI, whether given alone or in combination with adjunctive antithrombotic therapy, against other fibrinolytic agents, a placebo, or no treatment. Only trials investigating agents with an approved indication of reperfusion therapy in STEMI (streptokinase, tenecteplase, alteplase, and reteplase) were included. The primary efficacy outcome was all-cause mortality within 30-35 days and the primary safety outcome was major bleeding. This study is registered with PROSPERO (CRD42016042131).

FINDINGS

A total of 40 eligible studies involving 128 071 patients treated with 12 different fibrinolytic regimens were assessed. Compared with accelerated infusion of alteplase with parenteral anticoagulants as background therapy, streptokinase and non-accelerated infusion of alteplase were significantly associated with an increased risk of all-cause mortality (risk ratio [RR] 1·14 [95% CI 1·05-1·24] for streptokinase plus parenteral anticoagulants; RR 1·26 [1·10-1·45] for non-accelerated alteplase plus parenteral anticoagulants). No significant difference in mortality risk was recorded between accelerated infusion of alteplase, tenecteplase, and reteplase with parenteral anticoagulants as background therapy. For major bleeding, a tenecteplase-based regimen tended to be associated with lower risk of bleeding compared with other regimens (RR 0·79 [95% CI 0·63-1·00]). The addition of glycoprotein IIb or IIIa inhibitors to fibrinolytic therapy increased the risk of major bleeding by 1·27-8·82-times compared with accelerated infusion alteplase plus parenteral anticoagulants (RR 1·47 [95% CI 1·10-1·98] for tenecteplase plus parenteral anticoagulants plus glycoprotein inhibitors; RR 1·88 [1·24-2·86] for reteplase plus parenteral anticoagulants plus glycoprotein inhibitors).

INTERPRETATION

Significant differences exist among various fibrinolytic regimens as reperfusion therapy in STEMI and alteplase (accelerated infusion), tenecteplase, and reteplase should be considered over streptokinase and non-accelerated infusion of alteplase. The addition of glycoprotein IIb or IIIa inhibitors to fibrinolytic therapy should be discouraged.

FUNDING

None.

Enzymes approved for human therapy: indications, mechanisms and adverse effects

Research and drug developments fostered under orphan drug product development programs have greatly assisted the introduction of efficient and safe enzyme-based therapies for a range of rare disorders. The introduction and regulatory approval of 20 different recombinant enzymes has enabled, often for the first time, effective enzyme-replacement therapy for some lysosomal storage disorders, including Gaucher (imiglucerase, taliglucerase, and velaglucerase), Fabry (agalsidase alfa and beta), and Pompe (alglucosidase alfa) diseases and mucopolysaccharidoses I (laronidase), II (idursulfase), IVA (elosulfase), and VI (galsulfase). Approved recombinant enzymes are also now used as therapy for myocardial infarction (alteplase, reteplase, and tenecteplase), cystic fibrosis (dornase alfa), chronic gout (pegloticase), tumor lysis syndrome (rasburicase), leukemia (L-asparaginase), some collagen-based disorders such as Dupuytren's contracture (collagenase), severe combined immunodeficiency disease (pegademase bovine), detoxification of methotrexate (glucarpidase), and vitreomacular adhesion (ocriplasmin). The development of these efficacious and safe enzyme-based therapies has occurred hand in hand with some remarkable advances in the preparation of the often specifically designed recombinant enzymes; the manufacturing expertise necessary for commercial production; our understanding of underlying mechanisms operative in the different diseases; and the mechanisms of action of the relevant recombinant enzymes. Together with information on these mechanisms, safety findings recorded so far on the various adverse events and problems of immunogenicity of the recombinant enzymes used for therapy are presented.

Diastolic Timed Vibrator: Noninvasive Pre-Hospitalization Treatment of Acute Coronary Ischemia

The speed of intervention is one of the major factors in increasing the survival rate of patients suffering from acute coronary ischemia. The two principal techniques currently in use: pharmacological and interventional, can be employed to re-canalize coronary arteries, but the former is slow acting and often leads to incomplete reperfusion, while the latter requires specialized personnel in a hospital with a cardiac catheterization laboratory. In this paper, we introduce a novel method intended for pre-hospitalization treatment of patients with acute coronary ischemia that can be safely applied by a minimally trained individual prior to or during patient transportation to hospital. It consists in applying low frequency mechanical vibrations to the left intercostal space of patient's chest during diastole of the heart cycle, to induce vibrations of the heart and thus of the coronary arteries. Mechanical vibrations stimulate mixing of blood which improves drug delivery to the occlusion site, applies mechanical force on the clot leading to its faster dissolution and finally acts as a strong vasodilator in case of spasms. We introduce the principle of operation and the architecture of the Diastolic Timed Vibrator (DTV), including a custom ECG processing algorithm, vibration pattern generator and active braking methods. Experimental results demonstrate the functionality of the DTV device and pave way for in-vivo tests necessary for clinical confirmation of the proposed method.

Spontaneous recovery of complete atrioventricular block complicating acute anterior wall ST elevation myocardial infarction

BACKGROUND

Complete atrioventricular block complicating acute anterior wall ST elevation myocardial infarction (MI) is classically considered one of the worst prognostic indicators.

METHODS

We present the case of a gentleman who developed complete atrioventricular block during the course of acute anterior wall ST elevation MI, and had spontaneous resolution of the same. Mechanisms of spontaneous resolution of complete atrioventricular block in the setting of acute MI are discussed. Attention is drawn to a subgroup of patients, albeit a minority, who have a better prognosis owing to reversible causes than classically expected and seen.

RESULTS

Clinical features suggested that this patient had reocclusion of the infarct-related artery after thrombolysis on presentation and spontaneous reperfusion.

CONCLUSION

Coronary angiography provides invaluable information for decision making in such clinical scenarios. Complete atrioventricular block due to reversible ischaemia produced by reocclusion of an infarct-related artery should be reversible by percutaneous coronary angioplasty of the infarct-related artery. We suggest that reversible causes be considered before attributing atrioventricular block to irreversible damage, which would require a permanent pacemaker implantation. This would be more significant in most of the developing world, where resources are scarce.

Excimer laser angioplasty in acute myocardial infarction (the CARMEL multicenter trial)

Patients with acute myocardial infarction (AMI) with thrombus-laden lesions constitute a revascularization challenge. Thrombus and atherosclerotic plaque absorb laser energy; thus, we studied the safety and efficacy of excimer laser in AMI. In a multicenter trial, 151 patients with AMI underwent excimer laser angioplasty. Baseline left ventricular ejection fraction was 44 +/- 13%, and 13% of patients were in cardiogenic shock. A saphenous vein graft was the target vessel in 21%. Quantitative coronary angiography and statistical analysis were performed by independent core laboratories. A 95% device success, 97% angiographic success, and 91% overall procedural success rate were recorded. Maximal laser gain was achieved in lesions with extensive thrombus burden (p <0.03 vs small burden). Thrombolysis In Myocardial Infarction (TIMI) trial flow increased significantly by laser: 1.2 +/- 1.1 to 2.8 +/- 0.5 (p <0.001), reaching a final 3.0 +/- 0.2 (p <0.001 vs baseline). Minimal luminal diameter increased by laser from 0.5 +/- 0.5 to 1.6 +/- 0.5 mm (mean +/- SD, p <0.001), followed by 2.7 +/- 0.6 mm after stenting (p <0.001 vs baseline and vs after laser). Laser decreased target stenosis from 83 +/- 17% to 52 +/- 15% (mean +/- SD, p <0.001 vs baseline), followed by 20 +/- 16% after stenting (p <0.001 vs baseline and vs after laser). Six patients (4%) died, each presented with cardiogenic shock. Complications included perforation (0.6%), dissection (5% major, 3% minor), acute closure (0.6%), distal embolization (2%), and bleeding (3%). In a multivariant regression model, absence of cardiogenic shock was a significant factor affecting procedural success. Thus, in the setting of AMI, gaining maximal thrombus dissolution in lesions with extensive thrombus burden, combined with a considerable increase in minimal luminal diameter and restoration of anterograde TIMI flow, support successful debulking by excimer laser. The presence of thrombus does not adversely affect procedural success; however, cardiogenic shock remains a predictor of major adverse events during hospitalization.

Call-to-needle times for thrombolysis in acute myocardial infarction in Victoria

OBJECTIVE

To determine the proportion of patients in Victoria treated within the British Heart Foundation 90-minute call-to-needle (CTN) time benchmark for thrombolysis of ST-elevation myocardial infarction (STEMI), and to validate the British Heart Foundation 90-minute benchmark with respect to mortality.

DESIGN

Cohort study.

SETTING

20 hospitals and two ambulance services in the State of Victoria, Australia.

PARTICIPANTS

1147 patients with STEMI transported to hospital by ambulance and eligible for thrombolysis.

MAIN OUTCOME MEASURES

CTN time, and in-hospital mortality.

RESULTS

Median CTN time was 83 minutes (mean, 93.2 min; range, 29-894 min). Median door-to-needle (DTN) time was 37 minutes (mean, 46.5 min; range, 0-853 min). 61% of patients received thrombolysis within the 90-minute benchmark. Patients with CTN times > 90 minutes had an increased risk of dying (relative risk, 1.8; 95% CI, 1.3-2.7). Factors associated with CTN time < 90 minutes were lower DTN time, prior notification of the receiving hospital and transport time less than 20 minutes.

CONCLUSION

The British Heart Foundation CTN time benchmark is being met for 61% of eligible STEMI patients in Victoria. Strategies to reduce CTN time should be region-specific, and should include attempts to reduce DTN and to enhance ambulance-hospital communication. Prehospital thrombolysis may be appropriate for some regions.

Major bleeding complications after cardiopulmonary resuscitation: impact of thrombolytic treatment

OBJECTIVE

The risk of bleeding complications caused by thrombolysis in patients with cardiac arrest and prolonged cardiopulmonary resuscitation is unclear. We evaluate the complication rate of systemic thrombolysis in patients with out-of-hospital cardiac arrest caused by acute myocardial infarction, especially in relation to duration of cardiopulmonary resuscitation.

DESIGN

The study was designed as retrospective cohort study, the risk factor being systemic thrombolysis and the end-point major haemorrhage, defined as life-threatening and/or need for transfusion. Over 10.5 years, emergency cardiac care data, therapy, major haemorrhage and outcome of 265 patients with acute myocardial infarction admitted to an emergency department after successful cardiopulmonary resuscitation were registered.

RESULTS

We observed major haemorrhage in 13 of 132 patients who received thrombolysis (10%, 95% confidence interval 5-15%), five of these survived to discharge, none died because of this complication. Major haemorrhage occurred in seven of 133 patients in whom no thrombolytic treatment had been given (5%, 95% confidence interval 1-9%), two of these survived to discharge. Taking into account baseline imbalances between the groups, the risk of bleeding was slightly increased if thrombolytics were used (odds ratio 2.5, 95% confidence interval 0.9-7.4) but this was not significant (P = 0.09). There was no clear association between duration of resuscitation and bleeding complications (z for trend = 1.52, P = 0.12). Survival was not significantly better in patients receiving thrombolysis (odds ratio 1.6, 0.9-3.0, P = 0.12).

CONCLUSIONS

Bleeding complications after cardiopulmonary resuscitation are frequent, particularly in patients with thrombolytic treatment, but do not appear to be related to the duration of resuscitation. In the light of possible benefits on outcome, thrombolytic treatment should not be withheld in carefully selected patients.

Low-dose dobutamine stress 99mTc tetrofosmin quantitative gated SPECT performed during the acute phase of myocardial infarction predicts subsequent myocardial viability and detects stunned myocardium

This study evaluated the ability of low-dose dobutamine stress 99mTc tetrofosmin (DSTF) quantitative gated single photon emission computed tomography (QGS) performed during the acute phase of myocardial infarction to predict subsequent myocardial viability and detect stunned myocardium. Twenty-four patients suffering their first acute myocardial infarction (AMI) underwent coronary angioplasty after coronary angiography (CAG) immediately following admission. Follow-up CAG and left ventriculography (LVG) were performed 10 days and 6 months later. All patients underwent DSTF QGS to measure left ventricular ejection fraction (LVEF) at rest and during dobutamine infusion (10 microg.kg(-1).min(-1)) 14 days after angioplasty. No patient suffered coronary restenosis. After 6 months, the LVEF measured by LVG improved >5% in 12 patients (group A), and did not improve in the remaining 12 patients (group B). The culprit coronary artery, the peak serum creatine phosphokinase concentration, the recanalization time, and the LVEF during the acute phase were similar in the two groups. However, the increase in the LVEF was greater in group A than in group B during dobutamine infusion (deltaLVEF) as measured by DSTF QGS (11.2+/-3.8% vs 2.9+/-4.7%, P <0.001). If a cut-off value of 6.5% for the deltaLVEF was used to predict the improvement in LVEF during the chronic phase, then the sensitivity of this test was 83.3% and its specificity was 83.3%. It is concluded that DSTF QGS during AMI can be used to predict myocardial viability and detect stunned myocardium.

Time Course of Erythrocyte Antioxidant Activity in Patients Treated by Thrombolysis for Acute Myocardial Infarction

The deleterious effects of free radicals in acute myocardial ischaemia/reperfusion are rather well known. However, the possibility that thrombolysis positively affects the recovery of blood antioxidant capacity in the later postinfarction period, and thus contributes to the better overall outcome of these patients, has not yet been investigated. We followed the time course of erythrocyte antioxidant activity in 45 patients with first acute myocardial infarction (AMI), who were treated with streptokinase. Success of thrombolysis was evaluated by noninvasive clinical signs of reperfusion using continuous vector cardiography. The patients were divided into two groups according to successful or unsuccessful, reperfusion, The control group consisted of 24 healthy subjects. Glutathione peroxidase (GPX) and superoxide dismutase (SOD) were determined immediately after admittance to the hospital (0 hours) and after subsequent thrombolytic therapy (1.5, 6, 12, and 24 hours after initiation of infusion of streptokinase), and 2, 4, and 8 days after AMI. Patients with AMI had decreased antioxidant enzyme activity at the time of admit- tance to the hospital, showing that the oxidative/antioxidative balance is disturbed early during the ischemic phase of AMI. In AMI patients without successful reperfusion, erythrocyte antioxidant enzyme activity remains low during the postinfarction period of 7 days. It can be concluded that prolonged ischemia reduces antioxidant enzyme activity. AMI patients with successful reperfusion have a significant rise in the activity of antioxidant enzymes within the first hours after thrombolysis, followed by a decrease until the third postinfarction day. During the subsequent postinfarction period, erythrocyte antioxidant activity gradually recovered and reached control levels. These beneficial effects of reperfusion on erythrocyte antioxidant status might contribute to the better overall prognosis of these patients.

Benchmarking ambulance call-to-needle times for thrombolysis after acute myocardial infarction in Australia: a pilot study

BACKGROUND

Thrombolysis for patients with acute myocardial infarction (AMI) is of greatest benefit when treatment is commenced as soon as possible after symptom onset. The British Heart Foundation (BHF) recently set a benchmark recommending that eligible patients with AMI receive thrombolytic therapy less than 90 min after calling for medical assistance.

AIMS

The purpose of this study was to compare the performance of an urban emergency service to this benchmark. A secondary objective was to determine whether patients treated outside this time were at a greater risk of mortality.

METHODS

This study consisted of an explicit retrospective analysis of medical records for all patients who presented by ambulance to the Emergency Department (ED) of Western Hospital and received thrombolysis for AMI within 12 h of symptom onset. The study was conducted for the 18-month period between 1 January 1999 and 30 June 2000. Information collected included times of: (i) symptom onset, (ii) call for ambulance, (iii) ambulance response, (iv) transport to hospital and (v) thrombolysis, as well as final diagnosis and in-hospital mortality. For the purposes of this study, call-to-needle time (CTN) was defined as the time between calling the ambulance and commencement of thrombolytic therapy.

RESULTS

One hundred and twenty-seven patients met the inclusion criteria. Median CTN was 81 min (range 42-279 min). Sixty-four per cent of patients were treated within the 90-min benchmark. The relative risk of mortality for patients treated outside the 90-min benchmark was 2.6 (95% CI 0.98-6.72).

CONCLUSION

This study showed that the BHF benchmark for CTN was not being met for over one-third of patients in the study region, with potential impact on mortality after AMI. Further research is needed to establish: (i) whether there is relationship between longer transportation times and mortality, (ii) whether the findings of this study may be applied to other regions and (iii) what strategies might be employed to reduce CTN.

Initial experience with hyperoxemic reperfusion after primary angioplasty for acute myocardial infarction: results of a pilot study utilizing intracoronary aqueous oxygen therapy

OBJECTIVES

The purpose of this study was to evaluate the feasibility and safety of intracoronary hyperoxemic reperfusion after primary angioplasty for acute myocardial infarction (MI).

BACKGROUND

Hyperoxemic therapy with aqueous oxygen (AO) attenuates reperfusion injury and preserves left ventricular (LV) function in experimental models of MI.

METHODS

In a multi-center study of patients with acute MI undergoing primary angioplasty (PTCA), hyperoxemic blood (pO(2): 600 to 800 mm Hg) was infused into the infarct-related artery for 60 to 90 min after intervention. The primary end points were clinical, electrical and hemodynamic stability during hyperoxemic reperfusion and in-hospital major adverse cardiac events. Global and regional LV function was evaluated by serial echocardiography after PTCA, after AO infusion, at 24 h and at one and three months.

RESULTS

Twenty-nine patients were enrolled (mean age: 58.9+/-12.6 years). Hyperoxemic reperfusion was performed successfully in all cases (mean infusion time: 80.8+/-18.2 min; mean coronary perfusate pO(2): 631+/-235 mm Hg). There were no adverse events during hyperoxemic reperfusion or the in-hospital period. Compared with baseline, a significant improvement in global wall motion score index was observed at 24 h (1.68+/-0.24 vs. 1.48+/-0.24, p < 0.001) with a trend toward an increase in ejection fraction (48.6+/-7.3% vs. 51.8+/-6.8%, p = 0.08). Progressive improvement in LV function was observed at one and three months, primarily due to recovery of infarct zone function.

CONCLUSIONS

Intracoronary hyperoxemic reperfusion is safe and well tolerated after primary PTCA. These preliminary data support the need for a randomized controlled trial to determine if hyperoxemic reperfusion enhances myocardial salvage or improves long-term outcome.

Application of excimer laser angioplasty in acute myocardial infarction

BACKGROUND AND OBJECTIVE

Patients presenting with acute myocardial infarction who fail to respond to standard therapy with thrombolytics or have contraindications for their use oftentimes need revascularization with a mechanical device for removal of an occlusive coronary thrombus and its underlying atherosclerotic plaque. As both thrombi and plaques absorb laser energy in the ultraviolet wavelength (308 nm), we studied the feasibility and safety of excimer laser angioplasty in selective patients with complicated acute myocardial infarction.

STUDY DESIGN/MATERIALS AND METHODS

Fifty patients with acute myocardial infarction complicated by continuous chest pain and/or ischemia who had a total of 54 obstructive lesions were treated with percutaneous excimer coronary laser angioplasty (ELCA). A Q-wave myocardial infarction was documented in 56% and a non-Q-wave myocardial infarction in 44%. The baseline left ventricular ejection fraction was reduced at 43 +/- 13% and six patients (12%) presented to the cardiac catheterization laboratory in cardiogenic shock. Twenty-nine patients failed to respond to thrombolytic therapy and 16 had contraindications for thrombolytics and IIb/IIIa receptor antagonists. Following laser debulking, all patients received adjunct balloon dilation and then stents were deployed in 83% of the target lesions. Quantitative coronary arteriography (QCA) was performed at an independent core laboratory.

RESULTS

Ninety-eight percent laser success and 100% procedural success were achieved. By QCA the minimal luminal diameter increased from baseline of 0.7 +/- 0.5 to 1.3 +/- 0.5 mm post-lasing and then to 2.0 +/- 0.6 with balloon dilation to a final of 3.0 +/- 0.5 mm. Pre-laser percent stenosis diameter of 77 +/- 17% was reduced to 51 +/- 22% post-laser to 3.0 +/- 17% post-balloon and to a final of 15 +/- 25%. An 83% laser-induced reduction of thrombus burden area was achieved as well as an increase in TIMI flow from baseline of 1.7 +/- 1.1 to 2.8 +/- 0.4 by laser to a 2.9 +/- 0.4 final. There were no deaths, emergency bypass surgery, cerebral vascular accident, neurologic injury, or major perforation. In one case, a laser-induced major dissection was successfully treated by stenting. All 50 patients survived the procedure, improved clinically, and were discharged.

CONCLUSION

Application of excimer laser coronary angioplasty is feasible and safe in selected patients with acute myocardial infarction who either fail to respond to thrombolytics or have contraindications to these agents. Intracoronary thrombus at the target lesion can be successfully dissolved with this wavelength laser energy without adverse effect on the procedure results.

Does primary stenting preserve cardiac function in myocardial infarction? A case-control study. NORTH-981 investigators. Network of revascularisation therapy in Hokkaido

OBJECTIVE

To investigate whether coronary stenting limits myocardial injury and preserves left ventricular function.

DESIGN AND SETTING

Prospective multicentre case-control study of primary percutaneous transluminal coronary angioplasty (PTCA) with and without stenting, performed in seven cardiovascular centres.

SUBJECTS AND METHODS

45 consecutive patients with acute myocardial infarction who were treated with successful primary stenting (Stent group) and did not have restenosis were paired with 45 matched control subjects with acute myocardial infarction treated by successful primary PTCA without stenting, also with no restenosis (POBA group).

RESULTS

In comparison with the POBA group, the Stent group-especially those patients with a left anterior descending coronary artery lesion-had a smaller hypokinesis area (mean (SD): 15. 1 (20.0) v 34.4 (24.3) chords), reduced hypokinesis area/risk area (25.2 (31.9)% v 58.8 (40.1)%), and a larger ejection fraction (63.3 (10.2)% v 51.7 (11.7)%) evaluated by quantitative left ventriculography using the centerline method. In the Stent group, the correlation between risk area and hypokinesis area was significantly shifted downward. Multiple logistic regression analysis on infarct size limitation (hypokinesis area/risk area < 50%) identified preinfarction angina in all subjects and preinfarction angina and stenting in patients with left anterior descending coronary artery lesions as explanatory factors.

CONCLUSIONS

Primary PTCA using a coronary stent is effective in preventing myocardial injury and restoring left ventricular function in patients with anterior acute myocardial infarction.

Reduction of congestive heart failure symptoms by very early fibrinolytic therapy in acute myocardial infarction: a long-term follow-up

BACKGROUND

In patients with acute myocardial infarction (MI), early fibrinolytic therapy results in improved survival and preservation of ventricular function. The purpose of the study was to determine whether very early treatment also reduces the development of congestive heart failure.

METHODS AND RESULTS

During the years 1984 to 1989, 358 consecutive patients with acute MI were treated with streptokinase, 161 within the first 1.5 hours from the onset of chest pain (group A) and 197 within 1.5 to 4.0 hours (group B). In 68, fibrinolysis was initiated in the prehospital setting pioneered by our group. Symptoms related to heart failure including dyspnea on exertion, fatigue, orthopnea, paroxysmal nocturnal dyspnea, nocturia, and peripheral edema, in addition to pulmonary edema events, were assessed during 5 years of follow-up. The evaluation was based on medical records and a detailed questionnaire, which was filled in by the investigators. A favorable significant effect of very early thrombolysis on the development of most of these limiting symptoms appeared 3 months after hospital discharge and persisted thereafter (P <.05). During hospitalization, pulmonary edema attacks occurred less frequently in patients from group A (23% vs 36.5%, P <.01). This difference persisted during 4 years of follow-up (13% vs 36%, P <.001).

CONCLUSIONS

Our data demonstrate that very early fibrinolytic therapy results in a significant long-term reduction of congestive heart failure-related symptoms and thereby improves the quality of life in patients after MI.

Ultrasound enhancement of thrombolytic therapy: observations and mechanisms

Fibrinolytic therapy is a proven approach for achieving reperfusion of occluded coronary arteries during myocardial infarction, resulting in reduced mortality and preservation of ventricular function. The amount of myocardial muscle loss is proportional to the duration of ischemia. Bleeding complications are not infrequent. Adjuvant therapy by ultrasound might enhance the rate of fibrinolysis and reduce the concentrations of lytic agents required to achieve an equivalent degree of clot lysis. Noninvasive ultrasound at low intensities and high frequencies, parameters that potentially could be applied and tolerated in vivo, have been proven to significantly accelerate the rate of fibrinolysis in both in vitro and in vivo models, in pure fibrin as well as whole blood clots. Such enhancement is not drug-specific. These effects were achieved by nonthermal mechanism. Ultrasound exposure did not cause mechanical fragmentation of the clot, did not alter the size of plasmatic derivates and degradation products. Ultrasound caused increased flow rate through thrombi, probably by cavitation-induced changes in fibrin ultrastructure; disaggregation of uncrosslinked fibrin fibers into smaller fibers has been shown. This resulted in increased transport of the lytic agent into the clot, alteration of binding affinity and increased maximum binding. Presence of echo-contrast agent induced further acceleration of thrombolysis by ultrasound.

[Nuclear cardiology: technical bases and clinical applications]

Although the role of nuclear cardiology is currently well consolidated, the addition of new radiotracers and modern techniques makes it necessary to continuously update the requirements, equipment and clinical applications of these isotopic tests. The characteristics of the radioisotopic drugs and examinations presently used are explained in the first part of this text. In the second, the indications of them in diagnostic and prognostic evaluation of the different coronary diseases are presented.

Physicians' Use of Heparin Following Thrombolytic Therapy: An International Perspective

Background: The current prevalence, timing, and route of heparin use after thrombolytic therapy for acute myocardial infarction both within and outside the United States (U.S.) have not been extensively studied. Method: An 18-item questionnaire was mailed to cardiologists and emergency medicine practitioners in the U.S. and to physicians in 5 countries considering participation in an international trial of thrombolytic therapy. Results: Almost all used some form of heparin after recombinant tissue-plasminogen activator; 8% withheld heparin after streptokinase. Non-U.S. physicians used subcutaneous heparin more frequently than did U.S. physicians (26% vs. 4%). Time to heparin initiation varied greatly. Most physicians used the activated partial thromboplastin time to monitor anticoagulation, although there was little consensus about the appropriate way to determine the efficacy of heparin therapy. Conclusions: This survey shows considerable disagreement about the preferred administration of heparin among physicians treating patients with myocardial infarction. This lack of agreement reflects uncertainty about how heparin therapy should be used. When the results of well-designed clinical trials examining the optimal dosing, timing, and monitoring of heparin therapy have been published, perhaps the clinical community can reach a consensus.

Complete atrioventricular block complicating acute myocardial infarction in the thrombolytic era. SPRINT Study Group and the Israeli Thrombolytic Survey Group. Secondary Prevention Reinfarction Israeli Nifedipine Trial

OBJECTIVES

We assessed the incidence, associated clinical parameters and prognostic significance of complete atrioventricular block (CAVB) complicating acute myocardial infarction (AMI) in the thrombolytic era and compared them to data from the prethrombolytic era.

BACKGROUND

The introduction of new therapeutic modalities to treat AMI, aimed to enhance coronary reperfusion and to limit myocardial necrosis, was expected to decrease the incidence of CAVB and to improve prognosis. However, there are only limited data regarding the incidence and the prognosis of AMI patients with CAVB in the thrombolytic era.

METHODS

Data from 3,300 patients from the Israeli Thrombolytic Surveys (prospective, nationwide surveys of consecutive patients with AMI in all 25 coronary-care units in Israel in 1992 and 1996) were analyzed and compared with data from 5,788 patients included in the SPRINT (Secondary Prevention Reinfarction Israeli Nifedipine Trial) Registry (1981 to 1983).

RESULTS

During the 1990s, the incidence of CAVB was 3.7% compared with 5.3% in the 1980s, p = 0.0007. In the 1990s, mortality of patients with CAVB was significantly higher than in those without CAVB at 7 days (odds ratio [OR] = 4.05 95% CI [confidence interval] 2.34 to 6.82, 30 days OR = 3.98 [95% CI 2.44 to 6.43] and one-year hazard ratio [HR] = 2.36, [95% CI 1.68 to 3.30]) and similar in thrombolysis-treated and not-treated patients. Mortality of patients with CAVB has not changed significantly between the two periods; seven-day OR = 0.82 (95% CI 0.46 to 1.43); 30-day OR = 0.78 (95% CI 0.45 to 1.33) and one-year HR = 0.79 (95% CI 0.54 to 1.56), respectively, in the 1990s as compared to a decade earlier.

CONCLUSIONS

The incidence of CAVB complicating AMI is lower in the thrombolytic era than in the prethrombolytic era. Mortality among patients with CAVB is still high and has not declined within the last decade. The AMI patients who develop CAVB in the thrombolytic era have significantly worse prognosis than do patients without CAVB.

Asynergy of the noninfarcted left ventricular inferior wall in anterior wall acute myocardial infarction secondary to isolated occlusion of the left anterior descending artery

There are patients in whom left ventricular (LV) wall motion decreases in the noninfarcted region and LV systolic function declines globally despite the presence of a localized myocardial infarct attributable to narrowing or occlusion of a single coronary artery. This study examines angiographic characteristics of patients with chronic hypokinesia of noninfarcted myocardium after anterior wall acute myocardial infarction (AMI) due to narrowing of a single coronary artery, namely, the left anterior descending (LAD) artery. The LV ejection fraction, abnormalities in the motion of the noninfarcted LV inferior wall (SD/chord value by Sheehan's technique), the angiographic characteristics of the infarct-related coronary artery, the effect of acute reperfusion therapy, and presence of coronary risk factors were examined in 85 consecutive patients. The SD/chord value in the noninfarcted region showed a positive correlation with the LV ejection fraction (r = 0.505, p <0.0001). By multivariate analysis, hypertension (odds ratio = 0.53, 95% confidence interval [CI] 0.36 to 0.80), an infarct-related narrowing proximal to the origin of the first diagonal branch (odds ratio = 0.56, 95% CI 0.38 to 0.84), and patency of the infarct-related lesion during AMI (odds ratio = 1.56, 95% CI 1.03 to 2.30) were independent predictors of wall motion in the noninfarct region. In some patients with single-vessel anterior wall AMI, the motion of the noninfarcted inferior LV wall decreases during the chronic stage and cardiac function declines severely. In most of these patients, the infarct-related narrowing or occlusion is proximal to the origin of the first diagonal branch of the LAD artery.

Myocardial salvage by reperfusion 12 hours after coronary ligation in dogs

It is not clear why late reperfusion therapy in patients with acute myocardial infarction is effective. An investigation was carried out as to whether or not reperfusion conducted 12 h after coronary occlusion causes myocardial salvage in dogs. Coronary arteries were occluded in 11 mongrel dogs and a portion of the occlusion (late reperfusion area; LR area) reperfused 12 h later; the other part was left occluded (permanent occlusion area; PO area). The dogs were maintained for 4 weeks after reperfusion. Regional myocardial blood flow (Qm) was measured by the non-radioactive colored microsphere method. In both areas, the transmurality of necrosis was measured by triphenyl tetrazolium chloride staining, and the amount of viable myocardium and the extent of fibrosis was determined by Azan-Mallory staining. Qm decreased markedly after coronary occlusion to similar levels in both areas until 12 h. Qm transiently increased in the LR area only following reperfusion after 12 h. The transmurality of necrosis in the PO area was 83.8+/-10.5%, but that in the LR area was 58.7+/-21.3%, a significant decrease (p<0.01). In the outer layer, the amount of viable myocardium was significantly greater, and the extent of myocardial fibrosis was significantly less in the LR area. Evaluation in the same heart of dogs confirmed the myocardial salvage effects of late reperfusion (12 h after coronary occlusion).

Approaches to informed consent

Informed consent (IC) is an indicator, or a pivotal point, in broader and more fundamental questions dealing with the way clinical experimentation and, more specifically, randomized controlled trials (RCTs) relate to routine clinical practice; the rules that characterize the doctor-patient relationship; the self-perception of medicine with respect to its capacity, duty, and autonomy in the production of new knowledge; and the role of medicine in society. The asymmetry of knowledge and power that characterizes the usual relationship between care providers and patients does not resolve when something experimental enters the relationship. The real world of clinical investigation is not uniformly distinct from clinical practice. Experimentation is more appropriately considered a continuum with respect to appropriate or recommended care. Fundamental patient rights come first and are more binding than compliance with procedures and regulations. The view that IC is the most important component of the "ethical" aspects of experimentation is highly misleading. The responsibility to foster well-informed decisions shapes the contents, the timing, the validity, and the credibility of IC. Documented, evaluable decisions are the natural substitute for individual IC when the patient is not able to handle information autonomously. Positive examples of IC practices and approaches suggest that IC may be important in improving the way medicine responds to its responsibilities and communicates with society.

Revisiting reperfusion therapy in inferior myocardial infarction

Although thrombolytic therapy for acute myocardial infarction (MI) is recommended without regard for infarct location, treatment results are less impressive for inferior than for anterior MI because the amount of myocardium at risk is smaller and less strategically located, and the mortality risk is lower. Whereas the risks associated with anterior MI are relatively constant, high risk subsets of patients with an inferior MI can be identified by simple electrocardiographic criteria, including left precordial ST segment depression, complete atrioventricular heart block and right precordial ST segment elevation. Unfortunately, none of the placebo-controlled, randomized trials have analyzed the benefit of thrombolytic therapy for inferior MI in high risk versus low risk subsets. Thrombolytic therapy should be more successful in reducing infarct size and decreasing mortality in high risk patients with an inferior MI. Thrombolytic therapy may not decrease hospital mortality in low risk patients (baseline risk 2% to 4%) or those with symptom duration > 6 h. Whereas it is arguable whether coronary angioplasty is superior to thrombolytic therapy in anterior MI, there are no mortality data to support using angioplasty as a primary or rescue reperfusion strategy instead of thrombolytic therapy in inferior MI, unless thrombolytic contraindications are present or the patient is in cardiogenic shock.

Induction of cytokine expression in leukocytes in acute myocardial infarction

OBJECTIVES

This study sought to investigate whether cytokine expression in leukocytes may be induced by plasma from the reperfused heart of patients with an acute myocardial infarction (MI).

BACKGROUND

Reperfusion in acute MI is associated with deleterious local and systemic inflammatory responses that are regulated by cytokines. Induction of cytokine expression in resident leukocytes could contribute to inflammatory responses of the ischemic and reperfused heart.

METHODS

Blood samples of 10 patients with an acute MI were obtained simultaneously from the coronary sinus and the aorta before and 5 min after recanalization of the coronary occlusion. Ten patients with elective percutaneous transluminal coronary angioplasty served as a control group. We incubated leukocytes from healthy donors with plasma samples and analyzed mRNA expression of interleukin (IL)-1 beta, IL-6, IL-8 and tumor necrosis factor-alpha (TNF-alpha) by Northern blot analysis.

RESULTS

In patients with an acute MI, plasma obtained from the coronary sinus after recanalization increased the mRNA expression of IL-1 beta and IL-8 compared with that of plasma before recanalization (median [quartiles] difference before vs. after recanalization: 34.5 [4, 137], p = 0.017, for IL-1 beta; 18.5 [4, 35], p = 0.032, for IL-8) and simultaneously obtained aortic plasma (median [quartiles] coronary sinus-aortic differences after recanalization: 45.5 [-3, 115], p = 0.021, for IL-1 beta; 16 [4, 52], p = 0.005, for IL-8). No induction of IL-6 and TNF-alpha expression could be observed. No changes found in the study patients were detectable in the control group.

CONCLUSIONS

Plasma from the ischemic and reperfused heart stimulates the expression of IL-1 beta and IL-8 in leukocytes. Therefore, leukocyte-derived cytokines may contribute to the regulation of cardiac inflammatory responses in patients with an acute MI.

Early thrombolytic treatment in acute myocardial infarction: reappraisal of the golden hour

BACKGROUND

There is conclusive evidence from clinical trials that reduction of mortality by fibrinolytic therapy in acute myocardial infarction is related to the time elapsing between onset of symptoms and commencement of treatment. However, the exact pattern of this relation continues to be debated. This paper discusses whether or not appreciable additional gain can be achieved with very early treatment.

METHODS

The relation between treatment delay and short-term mortality (up to 35 days) was evaluated using tabulated data from all randomised trials of at least 100 patients (n = 22; 50,246 patients) that compared fibrinolytic therapy with placebo or control, reported between 1983 and 1993.

FINDINGS

Benefit of fibrinolytic therapy was 65 (SD 14), 37 (9), 26 (6) and 29 (5) lives saved per 1000 treated patients in the 0-1, 1-2, 2-3, and 3-6 h intervals, respectively. Proportional mortality reduction was significantly higher in patients treated within 2 h compared to those treated later (44% [95% CI 32, 53] vs 20% [15, 25]; p = 0.001). The relation between treatment delay and mortality reduction per 1000 treated patients was expressed significantly better by a non-linear (19.4-0.6x(+)29.3x-1) than a linear (34.7 - 1.6x) regression equation (p = 0.03).

INTERPRETATION

The beneficial effect of fibrinolytic therapy is substantially higher in patients presenting within 2 h after symptom onset compared to those presenting later.

Comparison of dobutamine stress echocardiography with dipyridamole stress echocardiography for detection of viable myocardium after myocardial infarction treated with thrombolysis

OBJECTIVE

To compare the ability of dobutamine and dipyridamole stress echocardiography to detect functional recovery of stunned but viable myocardial regions early after acute myocardial infarction, and to predict late functional recovery of the reperfusion salvaged myocardium within the infarct area.

METHODS

Within 10 d of acute myocardial infarction, 51 patients--30 anterior and 21 inferior, 44 Q wave and seven non-Q-wave infarction--were submitted to a dobutamine echocardiography test at low dose (5-10 micrograms/kg/min over 5 min) and high dose (20-40 micrograms/kg/min over 3 min) and to dipyridamole echocardiography test (0.56 mg/kg over 4 min + 0.28 mg/kg over 2 min) on different days and in random order, after interruption of any vasoactive drug. Resting echocardiography was repeated at two months in 41 of 51 patients (80%). Regional wall motion of the left ventricle was analysed in a semiquantitative manner on a 14-segment model. Viability was defined as improvement of one grade or more of at least two basally asynergic segments in the infarcted area.

RESULTS

Regional functional recovery was detected by low dose dobutamine in 38/51 patients (75%) and in 147/308 (48%) of basally asynergic segments, compared to 25/51 patients (49%; P < 0.001) and 78/308 segments (25%; P < 0.001) only identified by dipyridamole. Late spontaneous functional recovery was detected in 24/41 patients (59%) and in 78/254 basally asynergic segments (31%). The sensitivity of dobutamine and dipyridamole echocardiography for predicting spontaneous functional recovery was 72% and 51% respectively (P < 0.001), specificity 68% and 82% (P < 0.001), positive predictive value 50% and 56%, and negative predictive value 85% and 79%.

CONCLUSIONS

In comparison with dipyridamole in patients with thrombolysed myocardial infarction, dobutamine induces regional functional recovery. This suggests that dobutamine is more sensitive in showing the presence of viable myocardium within the infarct zone, though it has a lower specificity in predicting delayed spontaneous functional recovery of non-contractile but still viable areas.

Thrombolytic therapy. From myocardial to cerebral infarction. The MAST-I Group. Multicentre Acute Stroke Trial

Thrombolysis is proposed for the acute treatment of cerebral infarction as it is able to recanalize occluded arteries and thus potentially restore normal perfusion of the cerebral parenchyma, but the results concerning the efficacy of this treatment are still inconclusive. However, it has been fully demonstrated that thrombolytic treatment, leads to a significant reduction in mortality, in patients with acute myocardial infarction. Data from all of the pilot studies using SK or tPA treatment in acute stroke are described in this review, which underlines the incidence of hemorrhagic transformation (hemorrhagic infart and parenchymal hematoma) and its possible correlation to clinical worsening. Pharmacological, experimental and clinical studies encourage the carrying out of large-scale clinical trials using thrombolytics in patients with acute cerebral infarction. Significant data relating to ongoing controlled clinical trials will be available in the near future; only after the analysis of these results will it be possible to confirm the efficacy of thrombolytics in acute stroke.

Myocardial salvage by the use of reperfusion and intraaortic balloon pump: experimental study

BACKGROUND

Thrombolytic therapy improves left ventricular ejection fraction and survival. The study was undertaken to evaluate the effects of intraaortic balloon pump used in conjunction with reperfusion in reducing infarct size.

METHODS

Twenty-two dogs were subjected to proximal left anterior descending coronary artery occlusion. In group 1 (n = 7) occlusion lasted for 6 hours. In group 2 (n = 6) 2 hours of occlusion was followed by reperfusion. In group 3 (n = 9) after 2 hours of occlusion the dogs were assisted with the intraaortic balloon pump throughout the 4 hours of reperfusion. At the end of 6 hours the infarcted myocardium of the left ventricle was determined and expressed as percentage of the myocardium at risk.

RESULTS

In group 1, the infarcted myocardium was 79.3 +/- 9.9% of the myocardium at risk, in group 2, 59.0 +/- 19.9% (p < 0.05 versus group 1), and in group 3, 37.1 +/- 16.7% (p < 0.001 versus group 1 and p < 0.05 versus group 2). Endocardial viability ratio was increased by the intraaortic balloon pump; in group 1 it was 1.02 +/- 0.14, in group 2, 1.25 +/- 0.24, and in group 3, 1.47 +/- 0.31 (p < 0.001 versus group 1 and p < 0.02 versus group 2).

CONCLUSIONS

Reperfusion and intraaortic balloon pump increased salvage of the ischemic myocardium over that achieved by reperfusion alone in a canine occlusion-reperfusion model.

Comparison of "accelerated" tissue plasminogen activator with streptokinase for treatment of suspected myocardial infarction

PURPOSE

A computerized decision analysis, based on the results of published clinical trials, assessed the risks, benefits, and costs of different thrombolytic regimens for suspected myocardial infarction (MI) throughout the likely range of clinical circumstances.

DATA SOURCE

Medline search and articles' bibliographies.

STUDY SELECTION

All studies reporting efficacy and side effects of thrombolysis.

DATA ANALYSIS

Life-expectancy outcomes of thrombolytic therapies for possible MI modeled by decision analysis.

RESULTS

The analysis allows a clinician to estimate the benefits, risks, and relative costs of thrombolytic therapies throughout the likely range of individual clinical circumstances. When applied, for example, to the average patient in ISIS-2, estimated gains are 150 quality-adjusted days of life (QALDs) from treatment with streptokinase (SK) and 255 QALDs with "accelerated" tPA (tPA). tPA costs $1,686 more than SK, taking into account the cost of lifelong care of the extra strokes incurred. Nevertheless, the chances of stroke above which thrombolysis is not preferred are 5.0% for SK and 8.0% for tPA, with tPA remaining the preferred treatment for six hours after symptom onset; thereafter, SK is marginally preferred, but at much lower cost. Both regimens are beneficial in older patients provided the chances of MI and death are "average" or greater.

CONCLUSION

When the chances of MI and death are known, decision analysis can be a useful bedside tool to guide thrombolytic therapy and subsequently, if needed, to review and defend the treatment decisions made.

Early remodelling of coronary stenoses after thrombolytic treatment in patients with acute myocardial infarction

OBJECTIVE

To assess the frequency of early remodelling of coronary stenosis morphology after thrombolytic treatment in patients with acute myocardial infarction.

DESIGN

Coronary angiograms were analysed by a computerised edge detection analysis system. Coronary stenosis severity was measured and morphology classified as smooth or complex.

PATIENTS

Coronary arteriograms were obtained approximately 90 min and 24 h after thrombolytic treatment from 40 patients with acute myocardial infarction.

MAIN RESULTS

Stenosis morphology was complex in 22 patients (65%) and smooth in 11 (32%) 90 min after thrombolysis. The morphology of 11 (50%) complex coronary stenoses and three (27%) smooth stenoses had changed at 24 h (P < 0.05). The transition from complex to smooth was associated with a reduction in stenosis severity from 65 (4)% to 51 (5)% (P < 0.05). The stenosis severity was 63 (4)% and 60 (5)% in those with persistently complex morphology, and 56 (7)% and 50 (5)% in those with persistently smooth morphology at 90 min and 24 h respectively (NS).

CONCLUSIONS

Transition of morphology from complex to smooth within 24 h is common. This transition is associated with a reduction in stenosis severity of a degree greater than that found in persistently smooth stenoses over the same interval. 50% of stenoses are smooth at 24 h.

Spinal epidural hematoma following coronary thrombolysis with tissue plasminogen activator. Report of two cases

Two cases of spinal epidural hematoma following intravenous administration of recombinant tissue-type plasminogen activator are presented. Both patients received thrombolytic therapy for acute myocardial infarction; back pain and progressive neurological dysfunction ensued, secondary to spinal cord compression caused by epidural hematoma. Both individuals underwent emergency surgery for decompression and hematoma evacuation, resulting in improvement in neurological function. The current status of thrombolytic therapy is reviewed, with emphasis on complications of therapy that require neurosurgical intervention.

Timing, mode, and predictors of death after direct angioplasty for acute myocardial infarction

The timing and mechanisms of early (30 day) mortality in 330 consecutive patients treated with direct angioplasty less than 12 hr after onset of myocardial infarction without antecedent thrombolysis were studied. There were 38 deaths (11.5% of pts), with a majority being due to cardiogenic shock (76%). Other causes included acute closure (11%), death after emergency bypass surgery (5%), ventricular arrhythmias (5%), and respiratory failure (3%). No deaths from stroke or cardiac rupture were seen, in contrast to trials of thrombolytic agents. Most deaths were seen early, with 47% occurring within 1 day, 35% from days 2-7, and 18% from days 8-30. Death from cardiogenic shock was the most common cause of death throughout this period: 83% of deaths in days 0-3, 88% of deaths in days 4-6, and 43% of deaths in days 8-30. Significant predictors of early death included older age (P < .0001), multi-vessel disease (P < .05), direct angioplasty failure (P < .05), reduced ejection fraction (P < .0001), and anterior myocardial infarction (P < .0005). Gender, prior myocardial infarction, and prior bypass surgery did not affect mortality. Cardiogenic shock is the most common cause of early death after direct angioplasty for myocardial infarction. Patients with one or more risk factors for early death may benefit from additional myocardial salvage or revascularization efforts in the early post-infarct period. Certain causes of death after direct angioplasty (cardiac, rupture, stroke) appear to be less common than data reported for lytic therapy for myocardial infarction.

Effect of age on myocardial infarction and thrombolysis

Thrombolytic therapy has emerged as the treatment of choice for patients presenting with an acute myocardial infarction. Myocardial infarction is a major cause of morbidity and mortality in the elderly. Advancing age has been considered a relative contraindication to thrombolytic therapy despite the potential for the elderly to derive the greatest benefit from this therapy. This trend not to treat the elderly has been based on a perceived increased risk of complications. Available data pooled from several studies clearly show that the elderly benefit from thrombolytic therapy.

Left ventricular function following thrombolytic therapy for myocardial infarction

1. The aim of this study was to evaluate the utility of measurement of left ventricular function in assessing the efficacy of thrombolytic agents. 2. All published studies were reviewed. 3. The major effect of the introduction of thrombolytic therapy on mortality after myocardial infarction has been a dramatic decrease in the number of patients dying from cardiac failure. In the thrombolytic era, left ventricular function has remained the most important prognostic factor after recovery from acute myocardial infarction. There are three trials with the statistical power to evaluate left ventricular function, where both left ventricular function and survival were improved compared to placebo or control treatment. The recent Global Utility of Streptokinase and Tissue Plasminogen Activator for Occluded Coronary Arteries (GUSTO) Trial supports these findings, with left ventricular function being strongly correlated with mortality reduction. Left ventricular function, measured at 90 min either as ejection fraction, end-systolic volume or infarct zone contractility, closely correlated with 30 day mortality, P < 0.01. 4. Left ventricular function remains an important factor in the evaluation of the efficacy of different thrombolytic and adjuvant regimens.

Determinants of left ventricular function two weeks and one year after an acute myocardial infarction

This study examines possible covariates of left ventricular function two weeks and sixteen months after an acute infarction. It was performed in a group of 312 patients randomized double blindly to recombinant tissue plasminogen activator (rt-PA) (n = 156) or placebo treatment and followed thereafter for at least one year. Two weeks after the infarction, enzymatic infarct size, infarct-related vessel, and number of diseased coronary arteries were significant determinants of the infarct-related regional wall motion (centerline method) (R2 = 0.25 to 0.60, P = 0.0001). Enzymatic infarct size, regional wall motion of both infarct-related and remote areas, reinfarction, and treatment allocation were significant independent correlates of ejection fraction (R2 = 0.76), end-diastolic volume (R2 = 0.20), and end-systolic volume (R2 = 0.69, P < 0.0001). Infarct-related coronary artery and predischarge end-systolic volume were significant independent covariates of ejection fraction at rest (R2 = 0.47) after sixteen months. Age, enzymatic infarct size, and predischarge end-diastolic volume were independent determinants of the maximal (R2 = 0.49, P < 0.0001) and peak exercise ejection fraction (R2 = 0.49, P < 0.0001).

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)

Myocardium at risk and infarct size after thrombolytic therapy for acute myocardial infarction: implications for the design of randomized trials of acute intervention

OBJECTIVES

The purpose of this study was to estimate the effect of an improved reperfusion therapy for acute myocardial infarction on myocardial salvage and ventricular function for anterior and inferior infarctions and to ascertain the sample size required to detect such an effect.

BACKGROUND

There are significant differences in myocardium at risk between anterior and inferior infarctions that affect the benefit of reperfusion therapy.

METHODS

We studied 58 patients with acute myocardial infarction (24 anterior, 34 inferior) treated with intravenous recombinant tissue-type plasminogen activator and angioplasty when necessary. Tomographic imaging with technetium-99m sestamibi was performed to measure myocardium at risk, final infarct size and myocardial salvage and to estimate the beneficial effects of an improved therapy.

RESULTS

A new therapy that was 30% more effective than existing therapy (with respect to salvage) would increase salvage (and reduce mean infarct size) by 5.2% of the left ventricle and increase late ejection fraction by only 0.012 (95% confidence interval [CI] 0.009 to 0.015) in inferior infarction and by 0.038 (95% CI 0.027 to 0.047) in anterior infarction. If anterior and inferior infarctions occurred with equal frequency, a sample size of 140 patients in each treatment group would be required to detect such a change with 80% power. In a trial of interior infarctions alone, a sample size of 236 patients in each treatment group would be required compared with only 98 patients in a trial of anterior infarctions alone.

CONCLUSIONS

The anticipated mean benefit from an improved reperfusion therapy in individual patients with inferior infarction is very small and of questionable clinical significance. The anticipated benefit in anterior infarction is greater and easier to detect. Future randomized trials should be stratified for infarct location and should consider the greater absolute benefit of treatment in anterior infarction.

Ultrasound accelerates urokinase-induced thrombolysis and reperfusion

We have shown that ultrasound accelerates TPA-induced thrombolysis in vitro as assessed by release of labeled fibrinogen from radioactive labeled clots. Others have shown that ultrasound shortens the time to recanalization of TPA treated thrombi in animal models. The aim of this study was to test the hypothesis that ultrasound enhances thrombolysis and reperfusion by using urokinase in an in vitro flow system. An in vitro flow system of a branching tubing circuit was developed. Flow in one branch was obstructed by a thrombus. Five control clots were exposed to continuous wave ultrasound at a frequency of 1 MHz and intensity of 2.5 W/cm2 only without any thrombolytic agent (group 1). Twenty clots were exposed to a bolus of 80,000 U of urokinase and randomized to either ultrasound exposure (group 2) or to urokinase only without ultrasound (group 3). Flow distal to the clot and the rate of release of radiolabeled fibrin were used as indexes of reperfusion and thrombolysis, respectively. Exposure to ultrasound significantly accelerated urokinase-mediated reperfusion, with 40.6% +/- 11.8% of maximal flow in group 2 versus 1.3% +/- 0.7% in group 3, p < 0.0015 after 25 min. The maximal difference in flow between groups 2 and 3 was achieved at 40 minutes (67.4% +/- 11.1% vs 13.1% +/- 5.6%, p < 0.0009). Thrombolysis was significantly higher after 25 minutes of ultrasound exposure (24.1% +/- 4.6% in the ultrasound-treated group vs 9.7% +/- 3.5% in group 3, p < 0.013). The maximal difference in thrombolysis between groups 2 and 3 was 60 minutes. (52.5% +/- 5.1% vs 18.7% +/- 6.2%, p < 0.00015).(ABSTRACT TRUNCATED AT 250 WORDS)

Thrombolytic therapy. Agents, indications, and laboratory monitoring

The patient must be educated to seek medical attention promptly when this malady strikes, and the physician must likewise be taught to institute this therapy as soon as the patient is seen. Less than 6 years ago, it was strongly expressed that there was no rationale for attempting to restore blood flow in the coronary arteries in the setting of myocardial infarction. It was believed that once the diagnosis of myocardial infarction was made, it was too late to relieve myocardial fibers and avert myocyte necrosis. If this thinking and advice of "the damage has already occurred" and "it is too late" prevailed, it would not be known today that treatment of myocardial infarction with thrombolytic therapy within 6 hours of onset of symptoms significantly reduces mortality in comparison with optimal medical treatment (including heparin) without thrombolytic therapy. The concept of thrombolytic therapy is correct. Persistent investigative work in this area will result in better thrombolytic agents and greater dexterity in their use. The thrombolytic agents available today are good, and they can be used safely. To state that agents that have been established to be capable of thrombus resolution should not be used in the treatment of thrombosis is a true example of how not to proceed toward improvement. To be content to remain in the past will not permit entrance into the future.

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.