***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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    ***EXAMPLES*** 
    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 OBJECTIVE We sought to conduct a r and omized trial comparing late revascularization with conservative therapy in symptom-free patients after acute myocardial infa rct ion ( AMI ) . BACKGROUND In the absence of ischemia , the benefits of reperfusion late after AMI remain controversial . However , the possibility exists that an open infa rct related artery benefits healing post AMI . METHODS Of 223 patients enrolled with Q-wave anterior AMI , 66 with isolated persistent occlusion of the left anterior descending coronary artery ( LAD ) were r and omized to the following treatments : 1 ) medical therapy ( closed artery group ; n = 34 ) or 2 ) late intervention and stent to the LAD + medical therapy ( open artery group ; n = 32 ) . The study was powered to compare left ventricular ( LV ) end-systolic volume between the two groups 12 months post AMI . RESULTS Late intervention 26 + /- 18 days post AMI result ed in significantly greater LV end-systolic and end-diastolic volumes at 12 months than medical therapy alone ( 106.6 + /- 37.5 ml vs. 79.7 + /- 34.4 ml , p < 0.01 and 162.0 + /- 51.4 ml vs. 130.1 + /- 46.1 ml , p < 0.01 , respectively ) . Exercise duration and peak workload significantly increased in both groups from 6 weeks to 12 months post AMI , although absolute values were greater in the open artery group . Quality of life scores tended to deteriorate during this time interval in the closed artery patients but remained unchanged in the open artery patients . Coronary angiography at 1 year documented a low incidence of intergroup cross-over ( spontaneous recanalization in 19 % and closure in 11 % ) . CONCLUSIONS In the present study , recanalization of occluded infa rct -related arteries in symptom-free patients approximately 1 month post AMI had an adverse effect on remodeling but tended to increase exercise tolerance and improve quality of life Background —Percutaneous transluminal coronary angioplasty of the infa rct -related artery in stable survivors of acute myocardial infa rct ion is often performed , even in patients without any symptoms or residual ischemia . Despite the lack of r and omized studies , it is widely believed that this intervention will improve the clinical outcome of these patients . Methods and Results —Three hundred patients with single vessel disease of the infa rct vessel and no or minor angina pectoris in the subacute phase ( 1 to 6 weeks ) after an acute myocardial infa rct ion were r and omized to angioplasty ( n=149 ) or medical therapy ( n=151 ) . Primary end point was the survival free of reinfa rct ion , (re)intervention , coronary artery bypass surgery , or readmission for severe angina pectoris at 1 year . The event-free survival at 1 year was 82 % in the medical group and 90 % in the angioplasty group ( P = 0.06 ) . This difference was mainly driven by the difference in the need for ( re ) interventions ( 20 versus 8 , P = 0.03 ) . At long-term follow-up ( mean , 56 months ) , survival was 89 % and 96 % ( P = 0.02 ) . Survival free of reinfa rct ion , (re)intervention , or coronary artery bypass surgery was 66 % and 80 % in the medically and interventionally treated patients , respectively ( P = 0.05 ) . The use of nitrates was significantly lower in the angioplasty group , both at 1 year ( 38 % versus 67 % , P = 0.001 ) and at long-term follow-up ( 36 % versus 55 % , P = 0.006 ) . Conclusions —Percutaneous revascularization of the infa rct -related coronary artery in stable patients with single vessel disease improves clinical outcome at long-term follow-up and reduces the use of nitrates . The results of our study should be reproduced in a confirmatory study with a larger sample size before percutaneous coronary intervention in this low-risk patient subgroup , after myocardial infa rct ion can be recommended as routine treatment in clinical practice The aim of the present study was to investigate whether reperfusion by primary percutaneous coronary intervention ( PCI ) improves 12-month survival in late presenters with ST-segment elevation myocardial infa rct ion ( STEMI ) . We analyzed 2,036 patients with STEMI presenting 12 to 24 hours from onset of symptoms , without cardiogenic shock or pulmonary edema and not reperfused by thrombolysis , of 23,517 patients with STEMI enrolled in the Polish Registry of Acute Coronary Syndromes from June 2005 to August 2006 . An invasive approach was chosen in 910 ( 44.7 % ) of late presenters and 92 % of them underwent reperfusion by PCI . Patients with an invasive approach had lower mortality after 12 months than patients with a conservative approach ( 9.3 % vs 17.9 % , p < 0.0001 ) . The benefit of an invasive approach was also observed after multivariate adjustment with a relative risk 0.73 for 12-month mortality ( 95 % confidence interval 0.56 to 0.96 ) and in a sub population of patients selected by a propensity-score matching procedure with an adjusted relative risk 0.73 for 12-month mortality ( 0.58 to 0.99 ) . In conclusion , almost 1/2 of late presenters with STEMI were considered eligible for reperfusion by primary PCI . These patients had a lower 12-month mortality rate than they would have had if they had been treated conservatively , which supports the idea of late reperfusion in STEMI . However , whether all late presenters with STEMI should be treated invasively remains unanswered . Nevertheless , until a r and omized trial is undertaken , late presenters with STEMI could be considered for reperfusion by primary PCI The effect of late percutaneous transluminal coronary angioplasty ( PTCA ) of an occluded infa rct -related artery on left ventricular ejection fraction was studied in patients with a recent , first Q-wave myocardial infa rct ion in a prospect i ve , r and omized study . Forty-four patients ( 31 men and 13 women , mean age 58 + /- 12 years ) with an occluded infa rct -related coronary artery were r and omized to PTCA ( n = 25 ) or no PTCA ( n = 19 ) . Patients received acetylsalicylic acid , a beta blocker and an angiotensin-converting enzyme inhibitor unless contraindicated . Left ventricular ejection fraction was determined at baseline and 4 months . Coronary angiography was repeated at 4 months . Baseline ejection fraction measured 20 + /- 12 days after myocardial infa rct ion was 45 + /- 12 % in both groups . PTCA was performed 21 + /- 13 days after the event . The primary PTCA success rate was 72 % . One patient in each group died before angiographic follow-up , which was completed in 37 of the remaining 42 patients ( 88 % ; 21 with and 16 without PTCA ) . At 4 months , the infa rct -related artery was patent in 43 % of PTCA patients and in 19 % of no PTCA patients ( p = NS ) . Reocclusion occurred in 40 % of patients after successful PTCA . Secondary analyses showed that the change in left ventricular ejection fraction was significantly greater in patients with a patent infa rct -related artery ( + 9.4 + /- 6.2 % ) than in those with an occluded artery ( + 1.6 + /- 8.8 % ; p = 0.0096 ) . Baseline ejection fraction also independently predicted improvement in left ventricular ejection fraction ( p = 0.0001 ) . ( ABSTRACT TRUNCATED AT 250 WORDS OBJECTIVES This study was design ed to compare the in-hospital outcome of patients presenting with > 12 h from onset of chest pain and acute ST elevation myocardial infa rct ion ( AMI ) who received either immediate invasive or conservative therapy 
    Output:
    
However , subgroup analysis according to time to PCI showed that the clinical benefit was only from PCI after 12 h but not from 2 to 60 days of the onset of symptoms .
The present meta- analysis suggested that PCI performed > 12 h but not 2 - 60 days after AMI is associated with significant improvement in clinical outcomes .