Survival 12 years after randomization to streptokinase: the influence of thrombolysis in myocardial infarction flow at three to four weeks

A Systematic Review of the Efficacy and Safety of Tenecteplase Versus Streptokinase in the Management of Myocardial Infarction in Developing Countries

Myocardial infarction (MI) is a significant cause of morbidity and mortality in low- and middle-income countries. Fibrinolytic agents and percutaneous coronary intervention (PCI) are the main approaches for the recanalization and reperfusion of the myocardium following MI. Many studies have shown that PCI is superior to thrombolytics due to better outcomes and decreased mortality. Nevertheless, PCI's mortality gain over thrombolysis decreases as the time between presentation and PCI procedure increases. Furthermore, PCI is not widely available in most developing countries; thus, it cannot be delivered promptly. Most patients in developing countries cannot afford the cost of PCI. Thus, thrombolytic therapy remains essential to managing MI in developing countries and should not be disregarded. Tenecteplase (TNK) and streptokinase (SK) are the two most widely used fibrinolytics in managing MI in underdeveloped nations. Despite their widespread availability, comparative studies on them have been inconclusive. This study aims to review the available literature on the effectiveness and safety of TNK versus SK in managing MI in resource-poor nations. The study is reported according to the Preferred Reporting Items for Systematic Reviews and Meta-analysis (PRISMA) extension and analyzed according to Cochrane guidelines on synthesis without meta-analysis. A comprehensive literature search for studies comparing TNK and STK was conducted on EMBASE, Cochrane Library, Web of Science, CINAHL, Scopus, Google Scholar, and Ovid version of MEDLINE databases. A reference list of the eligible articles and systematic reviews was also screened. A narrative synthesis of the available data was done by representing the data on the effect direction plot, followed by vote counting. Of the 2284 references retrieved from the databases, only 17 studies met the inclusion criteria and were selected for final analysis. The study suggested that TNK is more effective in complete ST-segment resolution (80% vs 10% on the effect direction plot) and symptom relief (80% vs 20%) than SK. SK and TNK were comparable in achieving successful fibrinolysis (50% vs 50%). For the safety parameters, TNK is associated with a lesser risk of major bleeding than SK (88.9% vs 11.1%) and minor bleeding (25% vs 75%). SK was linked with a higher risk of hypotension/shock (77.8% vs 11.1%) and anaphylaxis/allergy (100% vs 0%). Long-term mortality was higher in the SK arm (100% vs 0%). In-hospital mortality is comparable between the two agents (37.5% vs 37.5%). There is conflicting evidence regarding other safety and efficacy endpoints. Compared to SK, TNK results in better complete ST-segment resolution and symptom relief. A higher risk of long-term mortality, increased risk of major and minor bleeding, hypotension, and allergy/anaphylaxis was observed in patients who received SK. Both agents were comparable in terms of in-hospital mortality and successful fibrinolysis. Controversy exists regarding which agent is linked with increased risk of 30-35-day mortality benefit and stroke. Randomized controlled trials (RCTs) with large sample sizes are needed to establish TNK vs SK superiority in efficacy and safety. The long-term duration of follow-up of the mortality rate of the two agents is also essential, as most patients in these regions cannot afford the recommended PCI post-fibrinolysis.

Acute myocardial infarction

Acute myocardial infarction has traditionally been divided into ST elevation or non-ST elevation myocardial infarction; however, therapies are similar between the two, and the overall management of acute myocardial infarction can be reviewed for simplicity. Acute myocardial infarction remains a leading cause of morbidity and mortality worldwide, despite substantial improvements in prognosis over the past decade. The progress is a result of several major trends, including improvements in risk stratification, more widespread use of an invasive strategy, implementation of care delivery systems prioritising immediate revascularisation through percutaneous coronary intervention (or fibrinolysis), advances in antiplatelet agents and anticoagulants, and greater use of secondary prevention strategies such as statins. This seminar discusses the important topics of the pathophysiology, epidemiological trends, and modern management of acute myocardial infarction, focusing on the recent advances in reperfusion strategies and pharmacological treatment approaches.

Rescue angioplasty for failed fibrinolysis--long-term follow-up of a large cohort

BACKGROUND

Fibrinolysis remains an important treatment for ST-elevation myocardial infarction, but fails to achieve adequate reperfusion in a significant proportion of cases. "Rescue" angioplasty is seen as the preferred treatment strategy in most contemporary centers although the literature provides conflicting evidence.

METHODS

We retrospectively reviewed all cases of rescue angioplasty performed at our cardiothoracic center from July 1999 to June 2008. The diagnosis of failed lysis was made on the basis of an ECG demonstrating failure of ST segment resolution >50% at 90 min. Periprocedural data was taken from a dedicated procedural database and mortality data obtained from the UK Office of National Statistics.

RESULTS

A total of 316 cases were performed. Patients were aged 61 ± 11 years. Thirty-day mortality was 8.9%. Thirty-day mortality in those presenting with cardiogenic shock was 50%, and in those requiring blood transfusion was also 50%. Thirty day mortality in those with TIMI III flow at the end of the procedure was significantly less than in those in whom this was not the case (6.6% vs. 23.3%; P < 0.001). One year mortality for the entire cohort was 10.1%. Longer-term follow-up revealed after 5.2 ± 2.3 years, survival in this cohort was 83%. Significant bleeding requiring blood transfusion occurred in 2.5% of cases.

CONCLUSIONS

We have shown that rescue angioplasty can be performed with good procedural success rates and excellent long-term results. Limiting bleeding complications and achieving TIMI III flow appear to be major determinants of achieving good long term results.

A novel percutaneous coronary intervention risk score to predict one-year mortality

Clinical and angiographic risk factors associated with adverse outcomes after percutaneous coronary intervention (PCI) have been included in previous validated risk scores. Complications after PCI are known to increase mortality and morbidity but have not been included in any model. Records of 6,932 consecutive patients who underwent PCI from 2000 to 2005 were reviewed. Patients presenting with cardiogenic shock were excluded. Logistic regression and bootstrap methods were used to build an integer risk score for estimating risk of death at 1 year after PCI using baseline, angiographic, and procedural characteristics and postprocedural complications. This risk score was validated in a set of consecutive patients who underwent PCI from 2006 to 2007. The following 8 variables were significantly correlated with outcome: older age, history of diabetes mellitus, chronic renal failure, heart failure, left main coronary artery disease, lower baseline hematocrit, greater hematocrit decrease after PCI, and Thrombolysis In Myocardial Infarction grade <3 flow after PCI. In the validation population (n = 973), average receiver operating characteristic curve area was 0.836. In conclusion, we developed and validated a simple integer risk score, including postprocedural variables that closely predict long-term mortality after PCI. This model emphasizes the significant impact of complications occurring after PCI on long-term outcomes.

Purification and characterization of a fibrinolytic subtilisin-like protease of Bacillus subtilis TP-6 from an Indonesian fermented soybean, Tempeh

We have isolated a bacterium (TP-6) from the Indonesian fermented soybean, Tempeh, which produces a strong fibrinolytic protease and was identified as Bacillus subtilis. The protease (TPase) was purified to homogeneity by ammonium sulfate fractionation and octyl sepharose and SP sepharose chromatography. The N-terminal amino acid sequence of the 27.5 kDa enzyme was determined, and the encoding gene was cloned and sequenced. The result demonstrates that TPase is a serine protease of the subtilisin family consisting of 275 amino acid residues in its mature form. Its apparent K (m) and V (max) for the synthetic substrate N-succinyl-Ala-Ala-Pro-Phe-pNA were 259 microM and 145 micromol mg(-1) min(-1), respectively. The fibrinogen degradation pattern generated by TPase as a function of time was similar to that obtained with plasmin. In addition, N-terminal amino acid sequence analysis of the fibrinogen degradation products demonstrated that TPase cleaves Glu (or Asp) near hydrophobic acids as a P1 site in the alpha- and beta-chains of fibrinogen to generate fragments D', E', and D' similar to those generated by plasmin. On plasminogen-rich fibrin plates, TPase did not seem to activate fibrin clot lysis. Moreover, the enzyme converted the active plasminogen activator inhibitor-1 to the latent form.

Rescue angioplasty after failed thrombolytic therapy for acute myocardial infarction

BACKGROUND

The appropriate treatment for patients in whom reperfusion fails to occur after thrombolytic therapy for acute myocardial infarction remains unclear. There are few data comparing emergency percutaneous coronary intervention (rescue PCI) with conservative care in such patients, and none comparing rescue PCI with repeated thrombolysis.

METHODS

We conducted a multicenter trial in the United Kingdom involving 427 patients with ST-segment elevation myocardial infarction in whom reperfusion failed to occur (less than 50 percent ST-segment resolution) within 90 minutes after thrombolytic treatment. The patients were randomly assigned to repeated thrombolysis (142 patients), conservative treatment (141 patients), or rescue PCI (144 patients). The primary end point was a composite of death, reinfarction, stroke, or severe heart failure within six months.

RESULTS

The rate of event-free survival among patients treated with rescue PCI was 84.6 percent, as compared with 70.1 percent among those receiving conservative therapy and 68.7 percent among those undergoing repeated thrombolysis (overall P=0.004). The adjusted hazard ratio for the occurrence of the primary end point for repeated thrombolysis versus conservative therapy was 1.09 (95 percent confidence interval, 0.71 to 1.67; P=0.69), as compared with adjusted hazard ratios of 0.43 (95 percent confidence interval, 0.26 to 0.72; P=0.001) for rescue PCI versus repeated thrombolysis and 0.47 (95 percent confidence interval, 0.28 to 0.79; P=0.004) for rescue PCI versus conservative therapy. There were no significant differences in mortality from all causes. Nonfatal bleeding, mostly at the sheath-insertion site, was more common with rescue PCI. At six months, 86.2 percent of the rescue-PCI group were free from revascularization, as compared with 77.6 percent of the conservative-therapy group and 74.4 percent of the repeated-thrombolysis group (overall P=0.05).

CONCLUSIONS

Event-free survival after failed thrombolytic therapy was significantly higher with rescue PCI than with repeated thrombolysis or conservative treatment. Rescue PCI should be considered for patients in whom reperfusion fails to occur after thrombolytic therapy.

Sustained Benefit 20 Years After Reperfusion Therapy in Acute Myocardial Infarction

OBJECTIVES

The goal of this research was to clarify whether the benefit of reperfusion therapy for myocardial infarction was sustained long-term and to assess the gain in life expectancy by reperfusion therapy.

BACKGROUND

Reperfusion therapy in acute myocardial infarction reduces infarct size and increases hospital survival.

METHODS

We analyzed the 20-year outcome of 533 patients (mean age 56 years; 82% men) who were randomized to either reperfusion therapy or conventional therapy during the years 1981 to 1985.

RESULTS

Mean follow-up was 21 years (range 19 to 23 years). At follow-up, 101 patients (36%) of the 269 patients allocated to reperfusion treatment and only 71 patients (26%) of the 264 conventionally treated patients were alive (p = 0.02). The cumulative 10-, 15-, and 20-year survival rates were 69%, 48%, and 37% after reperfusion therapy and 59%, 38%, and 27% in the control group, respectively (p = 0.005). Life expectancy of the reperfusion group was 15.2 years versus 12.4 years in the conventionally treated group (p < 0.0001). Myocardial re-infarction and subsequent coronary interventions were more frequent after reperfusion therapy, particularly during the first year. In multivariable analysis, reperfusion therapy was an important independent predictor of lower mortality at long-term follow-up (hazard ratio 0.7; 95% confidence interval 0.6 to 0.8). Other independent predictors of mortality were age, impaired left ventricular function, multivessel disease, infarct size, and inability to perform an exercise test at the time of discharge.

CONCLUSIONS

This is the first study demonstrating sustained (20-year) improved survival after reperfusion therapy. The gain in life expectancy was almost three years, representing about one-third of the life-years lost by myocardial infarction.

Primary angioplasty should be first line treatment for acute myocardial infarction: FOR

The UK government is considering establishing a national primary angioplasty service for patients with acute myocardial infarction. David Smith and Kevin Channer debate whether moving away from first line thrombolysis is appropriate or practical

Sympathetic Drive in Anterior and Inferior Uncomplicated Acute Myocardial Infarction

Background— The sympathetic activation that follows acute myocardial infarction (AMI) has been associated with increased morbidity and mortality. Because the prognosis after anterior AMI (ant-AMI) is worse than that after inferior AMI (inf-AMI), we planned to determine whether the magnitude of sympathetic hyperactivity differs between the two.

Methods and Results— Thirty-nine patients with uncomplicated AMI, comprising 2 matched groups of 17 patients with ant-AMI, and 22 patients with inf-AMI were examined. Measurements were obtained 2 to 4 days after AMI and compared with 20 normal subjects (NC) who were matched in terms of age and body weight to the AMI groups. Resting muscle sympathetic nerve activity was quantified from multiunit bursts (MSNA) and from single units (s-MSNA). Both groups of AMI patients were matched with regard to hemodynamic variables, left ventricular function, and infarct size. Both groups had greater (at least P <0.01) sympathetic nerve activity than NC (60±4.3 bursts/100 cardiac beats and 68±4.9 impulses/100 cardiac beats), but the magnitude of sympathetic nerve hyperactivity in ant-AMI (81±4.0 bursts/100 cardiac beats and 91±4.9 impulses/100 cardiac beats) was similar ( P >0.05) to that in inf-AMI (80±3.2 bursts/100 cardiac beats and 90±4.0 impulses/100 cardiac beats)

Conclusions— Both ant-AMI and inf-AMI resulted primarily in a similar magnitude of sympathetic nerve hyperactivity. These findings suggest that the worse prognosis after ant-AMI compared with after inf-AMI would not be related primarily to the degree of sympathetic hyperactivity.

Corrected TIMI frame counts correlate with stenosis severity and infarct zone wall motion after thrombolytic therapy

BACKGROUND

The majority of patients with patent infarct-related arteries after thrombolytic therapy have slower than normal flow, which relates to myocardial perfusion.

METHODS

To evaluate the relationships between blood levels of creatine kinase (CK) and the corrected Thrombolysis in Myocardial Infarction (TIMI) frame count (CTFC), infarct artery stenosis, and left ventricular function, we studied 397 patients with a first myocardial infarction who underwent angiography at 3 weeks. TIMI flow grades, the CTFC, infarct artery stenosis, and infarct zone wall motion (by contrast ventriculography using the centerline method) were assessed, and CK levels (in units per liter) were measured hourly for the first 4 hours after streptokinase (1.5 x 10(6) U over 30-60 minutes) and then every 4 hours over the next 20 hours, all blinded to treatment and outcome.

RESULTS

Infarct artery stenosis and the CTFC, assessed as continuous variables, correlated in patients with patent infarct arteries (r = 0.33, P <.001). Also, there was a significant correlation between the CTFC and the sum of hypokinetic chords in the infarct zone (r = 0.15, P =.01). Patients with total occlusion or markedly slowed infarct artery flow (CTFC >100) had a higher fraction of chords with wall motion >2 SDs below normal (0.65 [0.41, 0.80] vs 0.37 [0.0, 0.67]) compared with patients with normal flow (CTFC < or =27) (P <.001). The rates of increase of median CK levels with respect to TIMI flow grades were 342 U/L/h for TIMI 3 versus 212 U/L/h for TIMI 2 versus 140 U/L/h for TIMI 0-1 (P <.0001).

CONCLUSIONS

Prolonged corrected TIMI frame counts correlate with stenosis severity in the infarct artery after infarction, infarct zone regional wall motion, and CK levels.

Combined revascularization strategy for acute myocardial infarction in patients with intracoronary thrombus: preceding intracoronary thrombolysis and subsequent mechanical angioplasty

Thrombus in the infarct-related artery is one of the limitations for flow restoration in primary percutaneous transluminal coronary angioplasty (PTCA) treatment for acute myocardial infarction (AMI). The present study investigated the benefit of preceding intracoronary thrombolysis (ICT) by retrospectively analyzing acute phase flow restoration in 80 AMI patients with intracoronary thrombus: 40 undergoing primary PTCA alone (primary PTCA group) and 40 treated with preceding ICT plus PTCA (combined group). Acute phase Thrombolysis in Myocardial Infarction (TIMI) grade flow was as follows: TIMI 0/1: 35.0% vs 12.5% for the primary PTCA group and the combined group, p=0.06; TIMI 2: 7.5% vs 15.0%, p=NS; TIMI 3: 57.5% vs 72.5%, p=NS). In the subgroup analysis, it was also less in the combined group among 33 patients with a left anterior descending coronary artery (LAD) lesion (42.1 % vs 7.1%, p=0.08), but not among the remaining 47 with either a right coronary artery or left circumflex artery lesion. The combined therapy may potentially provide better acute phase flow restoration in AMI patients with an intracoronary thrombus in a LAD lesion.

The acute management of myocardial infarction

Acute myocardial infarction (AMI) is a common and potentially fatal condition. Primary prevention by reducing the risk of developing coronary atheroma disease has had an important effect on the incidence of the disease. However, for many, the first clinical presentation of their coronary atheroma is the development of acute coronary occlusion. The acute nature of such presentation is the result of the dynamic nature of the plaque event. Thus while measures such as increasing public education in areas of primary prevention are always important it needs to be recognised that real differences in outcome need to and can be made even once the event has occurred. Individuals developing chest pain need to be encouraged to present early, especially if they have a history of ischaemic heart disease. Once they have arrived at point of medical contact, rapid triage, early diagnosis and the institution of therapies designed to reduce the extent of myocardial damage are paramount.

A review of the long term effects of thrombolytic agents

Unequivocal evidence exists that reperfusion therapy, when given within 12 hours after onset of symptoms, saves the lives of patients with acute myocardial infarction (MI). As a result, the routine use of such treatment has increased rapidly since the mid-1980s but the rates of utilisation have been relatively static over the last decade at approximately 50% of patients with acute MI. The major question arising in this respect is: is the benefit of reperfusion therapy, which is achieved during the acute phase in evolving MI, maintained on the long term? The main thrombolytic agents currently in use are streptokinase, alteplase, anistreplase, urokinase and reteplase. Other studies compared coronary angioplasty with thrombolytic therapy and investigated the effect of an additional angioplasty procedure after failed thrombolytic therapy. Furthermore, several studies have been performed to investigate the effect of initiation of reperfusion therapy before hospital admission. It is generally agreed that, in particular, patients receiving early treatment within 6 hours from onset of symptoms and patients with ST elevation benefit most from thrombolytic therapy. One would theoretically expect that infarct size reduction achieved by reperfusion therapy would also have a beneficial effect on the survival, not only during the hospital stay but also afterwards, resulting in diverging survival curves between patients who received reperfusion therapy and those who did not. However, the survival curves run perfectly parallel after hospital discharge from 1 year up to year 10 in most studies. The explanation for a lack of extra benefit may be a net result of combining the results of several subgroups. For example, thrombolytic therapy results in more frequent reinfarction especially in the first year, or patients with low left ventricular ejection fraction could survive the hospital phase because of effective thrombolytic therapy, but they survive at high risk. Although several trials suggest that primary percutaneous transluminal coronary angioplasty may be more beneficial than thrombolytic therapy in acute MI, these data should be interpreted cautiously unless confirmed by larger studies with long term results. In addition, evidence exists to suggest that administration of fibrinolytic treatment, under certain conditions, before hospital admission may lead to further improvement of a patient's prognosis. Again, further investigation is warranted. The conclusion is that clear evidence exists that the early improved survival after thrombolytic therapy has been shown to be maintained beyond a decade. However, the expected theorectical additional benefit of reperfusion therapy after hospital discharge has not been observed.

Third-generation thrombolytic drugs

Several third-generation thrombolytic agents have been developed. They are either conjugates of plasminogen activators with monoclonal antibodies against fibrin, platelets, or thrombomodulin; mutants, variants, and hybrids of alteplase and prourokinase (amediplase); or new molecules of animal (vampire bat) or bacterial (Staphylococcus aureus) origin. These variations may lengthen the drug's half-life, increase resistance to plasma protease inhibitors, or cause more selective binding to fibrin. Compared with the second-generation agent (alteplase), third-generation thrombolytic agents such as monteplase, tenecteplase, reteplase, lanoteplase, pamiteplase, and staphylokinase result in a greater angiographic patency rate in patients with acute myocardial infarction, although, thus far, mortality rates have been similar for those few drugs that have been studied in large-scale trials. Bleeding risk, however, may be greater.

Relationship between corrected TIMI frame counts at three weeks and late survival after myocardial infarction

OBJECTIVES

To evaluate the corrected Thrombolysis in Myocardial Infarction (TIMI) frame count (CTFC) as a predictor of late survival after myocardial infarction.

BACKGROUND

Thrombolysis in Myocardial Infarction flow grades predict late survival after myocardial infarction. The CTFC provides a more reproducible measurement of infarct-related artery blood flow than the TIMI flow grade, and has been linked to 30-day outcomes, but it has not yet been established how the CTFC correlates with late survival.

METHODS

Of 1,001 patients with acute myocardial infarction presenting within 4 h of symptom onset, 882 underwent angiography at approximately three weeks. Infarct artery flow was assessed, blinded to clinical outcomes, according to the CTFC and TIMI flow grade. Late cardiac mortality and survival were determined in 97.5% of patients.

RESULTS

The mean CTFC was 40 +/- 29 in 644 patent infarct arteries (median, 34 [interquartile range, 24 to 47]). The CTFC, assessed as a continuous univariate variable, was found to be a predictor of five-year survival, as was the TIMI flow grade (both p < 0.001). On multivariate analysis, factors associated with five-year survival included the ejection fraction or end-systolic volume index (both p < 0.001); exercise duration (p = 0.005), age (p = 0.008), diabetes (p = 0.02) and CTFC (p = 0.02) or TIMI flow (p = 0.02). The same factors, except for the CTFC and TIMI flow grade, were predictors of 10-year survival.

CONCLUSIONS

The CTFC three weeks after myocardial infarction was an independent predictor of five-year survival, but not 10-year survival. Although the CTFC provided additional prognostic information within TIMI flow grades, its superiority was not demonstrated.