***TASK*** the task is to summarize an input biomedical literature in six sentences 
    ***INPUT*** the input is a biomedical literature 
    ***OUTPUT*** the output is the summary of an input biomedical literature in six sentences 
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    Input: BACKGROUND Although the short-term and long-term beneficial effects of early coronary revascularization by primary PTCA or thrombolytic therapy have been established for acute myocardial infa rct ion , thrombolytic therapy > 24 hours after the onset of acute myocardial infa rct ion has not been shown to improve clinical outcome . The purpose of this study was to assess the effect of late revascularization by primary PTCA over a 5-year period . METHODS AND RESULTS Eighty-three patients with initial Q-wave anterior myocardial infa rct ion > 24 hours after onset were r and omized into a PTCA group ( n=44 ) and a no-PTCA group ( n=39 ) . Long-term follow-up was conducted with regard to end points , which included cardiac death , nonfatal recurrence of myocardial infa rct ion , and development of congestive heart failure . Left ventricular ejection fraction and regional wall motion at 6 months after myocardial infa rct ion were similar in the 2 groups . Left ventricular end-diastolic and end-systolic volume indexes were significantly smaller in the PTCA group than in the no-PTCA group ( P<0.0001 ) . With cardiac events as end points , a 5-year Kaplan-Meier event-free survival analysis revealed that the no-PTCA group had a worse prognosis than the PTCA group ( P<0.0001 ) . Patency of the infa rct -related artery , left ventricular ejection fraction , end-diastolic volume index , and end-systolic volume index were significantly associated with cardiac events by a Cox proportional hazards analysis ( hazard ratios 0.120 , 0.845 , 1.065 , and 1.164 , respectively ) . CONCLUSIONS In initial Q-wave anterior myocardial infa rct ion , we conclude that even with late reperfusion , PTCA had beneficial effects on cardiac events over the 5-year period after myocardial infa rct ion , with the prevention of left ventricular dilation after myocardial infa rct ion being a possible mechanism Background After thrombolytic therapy for patients with acute myocardial infa rct ion ( MI ) , percutaneous transluminal coronary angioplasty ( PTCA ) is frequently performed because of the presence of a “ significant ” infa rct vessel stenosis demonstrated at predischarge coronary angiography . Several studies have shown PTCA performed early after thrombolysis to be unnecessary or even harmful . However , PTCA in these trials was generally performed 1–3 days after MI , when the milieu in the infa rct artery may be unsuited for PTCA , and the incidence of major ischemic complications was high . To date , no trial has assessed whether delayed PTCA ( 4–14 days ) should be performed in patients without evidence of ischemia on stress testing . Methods and Results To test the hypothesis that delayed PTCA might provide clinical benefit compared with medical therapy alone , 87 patients treated within 6 hours of chest pain onset with thrombolytic therapy and with negative functional test were r and omized between PTCA to be performed 4–14 days after MI versus no PTCA . Both groups received medical therapy . Patients with postinfa rct angina or prior Q wave infa rct ion in the infa rct distribution were excluded . The primary study end point was increase in left ventricular ejection fraction with exercise measured by radionuclide studies 6 weeks after MI , a parameter known from other studies to correlate inversely with future ischemic events . Clinical outcome was also monitored for 12 months . There were no differences between the study groups for any prer and omization variable recorded . Mean age was 57± 10 years , 84 % of patients were male , 21 % had prior MI , 36 % had anterior MI , 7 % had multivessel disease , and the infa rct stenosis measured 70±17 % before r and omization . PTCA was successful in 38 of 42 patients ( 88 % ) but result ed in non-Q wave MI due to acute closure of the treated site in three of 42 ( 9.5 % ) . There was no difference in 6-week resting ejection fraction or increase in ejection fraction with exercise between the two groups ( 47±12 % and 6±8 % , respectively , in the PICA group ; 49±10 % and 5±9%o in the no-PTCA group ; p = NS for both . ) There were no deaths in either group . Actuarial 12-month infa rct -free survival was 97.8 % in the no-PTCA group and 90.5 % in the PTCA group ( p=0.07 ) . Conclusions There was no functional or clinical benefit from routine late PTCA after MI treated with thrombolytic therapy in this relatively low-risk cohort of patients . These data strongly suggest that patients with an uncomplicated MI after thrombolytic therapy  , even if they have a “ significant ” residual stenosis of the infa rct vessel , should be treated medically if they are without evidence of ischemia on stress testing before hospital discharge Background Experimental and observational clinical studies of acute coronary occlusion have suggested that late reperfusion prevents infa rct expansion and facilitates myocardial healing . The purpose of this trial was to assess whether infa rct vessel patency could be achieved in late-entry patients and what benefit , if any , can be demonstrated . Methods and Results In a double-blind fashion , 197 patients with 6 to 24 hours of symptoms and ECG ST elevation were r and omly assigned to tissue-type plasminogen activator ( 100 mg over 2 hours ) or placebo . Coronary angiography within 24 hours was used to determine infa rct vessel patency status . Patients with infa rct -related occluded arteries were then eligible for a second r and omization to either angioplasty ( 34 patients ) or no angioplasty ( 37 patients ) . Ventricular function and cavity size were reassessed at 1 month by gated blood pool scintigraphy and at 6 months by repeat cardiac catheterization . The primary end point , infa rct vessel patency , was 65 % for plasminogen activator patients compared with 27 % in the placebo group ( p<0.0001 ) . There were no differences between these groups in ejection fraction or infa rct zone regional wall motion at 1 or 6 months . At 6 months , infa rct vessel patency was 59 % in both groups . In the placebo group , there was a significant increase in end-diastolic volume from acute phase of 127 ml to 159 ml at 6-month follow-up ( p=0.006 ) but no increase in cavity size for the plasminogen activator group patients . Coronary angioplasty was associated with an initial 81 % recanalization success and improved ventricular function at 1 month , but by late follow-up no advantage could be demonstrated for this procedure , and there was a 38 % spontaneous recanalization rate in the patients assigned to no angioplasty . Conclusions The study demonstrates that it is possible to achieve infa rct vessel recanalization in the majority of late-entry patients with either  thrombolytic therapy or angioplasty . Thrombolytic intervention had a favorable effect on prevention of cavity dilatation and left ventricular remodeling , but there are no late benefits on systolic function after thrombolysis or coronary angioplasty . The conclusions concerning overall potential benefit of applying late reperfusion therapy will require data from large-scale trials design ed to assess mortality reduction For nearly a decade , it has been appreciated that 1 ) thrombotic occlusion of an epicardial coronary artery is usually the proximate cause of acute myocardial infa rct ion ; 2 ) after sudden and sustained total occlusion of such a vessel , the course of myocardial necrosis is generally rapid and relentless ( in most cases , the process is completed within 3 or 4 hours of the coronary occlusion , in 6 hours at a maximum ) ; 3 ) infa rct size is a critical determinant of left ventricular function ; and 4 ) left ventricular function , in turn , is the most important determinant of early ( in-hospital ) and long-term ( postdischarge ) survival . Major efforts have been devoted to the development of techniques design ed to interfere with the sequence of events summarized above . Considerable attention has been directed to achieving timely reperfusion of occluded coronary arteries to interrupt the infa rct ion with the hope that the result ant limitation of infa rct size will improve ventricular function and thereby patient survival.1 Many techniques to achieve reperfusion have been used , including emergency coronary artery bypass surgery , emergency percutaneous transluminal coronary angioplasty ( PTCA ) , and the intracoronary and intravenous administration of a variety of thrombolytic agents ; the last of these approaches is particularly attractive because its simplicity makes it applicable to a large proportion of patients with acute myocardial infa rct ion . In some instances , combinations of these techniques , such as intravenous thrombolytic therapy followed by PTCA , have been used . These efforts to treat acute myocardial infa rct ion have been notably successful , as reflected in an improvement in survival noted in controlled r and omized trials.2 - 6 Also , the absolute mortality rates achieved in some recent trials of reperfusion therapy ( 3 - 5 % ) are far lower than those noted The TAMI-6 trial has demonstrated that coronary reperfusion > 6h after onset ( ie , late reperfusion ) in patients with acute myocardial infa rct ion ( AMI ) does not improve left ventricular ( LV ) function during the chronic phase of infa rct ion . However , the low patency rate ( only 60 % ) of the infa rct -related artery ( IRA ) during the chronic phase in the TAMI-6 trial raises a new hypothesis that late reperfusion with a higher patency rate may improve LV function during the chronic phase . Forty-four patients with AMI , who were admitted to hospital 6 - 24h after the symptom onset and in whom emergency coronary angiography revealed a total occlusion of the IRA , were r and omly assigned to either the late reperfusion group ( n=22 ) or the non-reperfusion group ( n=22 ) . The initial success rate of reperfusion therapy  in the late reperfusion group was 86 % and the chronic patency rate of the IRA was 91 % . The improvements in ejection fraction and chord shortening in the infa rct region from the acute phase to the chronic phase were significantly greater in the late reperfusion group than in the non-reperfusion group . Late reperfusion with a high patency rate of the IRA significantly improves LV global and regional function in patients with AMI Background —A recent l and mark report has demonstrated that plasma B-type natriuretic peptide ( BNP ) measured in acute coronary syndromes independently predicts mortality , heart failure , and new myocardial infa rct ion . After acute cardiac injury , left ventricular ejection fraction ( LVEF ) is also of prognostic significance and plays a major role in determining the therapeutic response . Methods and Results —The present report is the first from a substantial ( n=666 ) cohort of patients with acute myocardial infa rct ion to test the prognostic utility of concurrent measurements of BNP , amino-terminal BNP ( N-BNP ) , norepinephrine , and radionuclide LVEF .  The B-type peptides and LVEF were predictors of death , heart failure , and new myocardial infa rct ion ( all P < 0.001 ) independent of patient age , gender , previous myocardial infa rct ion , antecedent hypertension or diabetes , previous heart failure , plasma norepinephrine , creatinine , cholesterol , drug therapy , and coronary revascularization procedures . The combination of N-BNP ( or BNP ) with LVEF substantially improved risk stratification beyond that provided by either alone . Elevated N-BNP ( or BNP ) predicted new myocardial infa rct ion only in patients with LVEF < 40 % . LVEF < 40 % coupled to N-BNP over the group median conferred substantial 3-year risks of death , heart failure , and new myocardial infa rct ion of 37 % , 18 % , and 26 % , respectively . N-BNP and BNP were equivalent prognostic markers for these clinical outcomes . Conclusions —Plasma N-BNP ( or BNP ) and LVEF are complementary independent predictors of major adverse events on follow-up after myocardial infa rct ion . Combined measurement provides risk stratification substantially better than that provided by either alone Experimental and clinical studies have suggested that late opening of an infa rct -related artery ( IRA ) after myocardial infa rct ion ( MI ) could improve clinical outcome . However , the suggestive observational data are limited by selection biases . Indeed , most small r and omized studies have not demonstrated benefit . Thus , there is no recommendation for routine late opening of the IRA in current national guidelines for management of stable post-MI patients . The OAT is design ed to test the hypothesis that opening a totally occluded IRA 3 to 28 days after MI in high-risk asymptomatic patients will improve clinical outcome and be cost-effective . The primary end point is the first occurrence of recurrent MI , hospitalization/treatment of New York Heart Association class IV congestive heart failure , or death . Trial background , design , and preliminary baseline characteristics of 2027 r and omized patients are presented . Eligible patients are r and omly assigned in equal proportions to optimal evidence - 
    Output:
    
This meta- analysis suggests that late revascularization of an occluded IRA may improve left ventricular systolic function and remodeling , supporting the " open artery hypothesis . "