***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 
    ***DOCUMENTATION*** 
    ***EXAMPLES*** 
    Input: Reproducibility and validity are prerequisites for a useful clinical scale . We therefore prospect ively tested the reproducibility and validity of the New York Heart Association criteria and the Canadian Cardiovascular Society criteria for the assessment of cardiac functional class  and compared these criteria with a new Specific Activity Scale based on the metabolic costs of specific activities . The New York Heart Association estimates made by two physicians had a reproducibility of only 56 % , and only 51 % of the estimates agreed with treadmill exercise performance . Functional estimates based on the Canadian Cardiovascular Society criteria were significantly more reproducible ( 73 % ) , but not significantly more valid . The Specific Activity Scale was as reproducible as the Canadian Cardiovascular Society criteria , and its 68 % validity was significantly higher than the validities of the other systems . The easily administered Specific Activity Scale was equally reproducible and valid when used by a nonphysician . It was especially better than the other systems for the evaluation of true class II patients and was significantly less likely to underestimate treadmill performance . Although no set of questions can perfectly predict exercise tolerance , the Specific Activity Scale deserves wider prospect i ve testing Background — In animal models , brief periods of ischemia performed just at the time of reperfusion can reduce infa rct size , a phenomenon called postconditioning . In this prospect i ve , r and omized , controlled , multicenter study , we investigated whether postconditioning may protect the human heart during coronary angioplasty for acute myocardial infa rct ion . Methods and Results — Thirty patients , su bmi tted to coronary angioplasty for ongoing acute myocardial infa rct ion , contributed to the study . Patients were r and omly assigned to either a control or a postconditioning group . After reperfusion by direct stenting , control subjects underwent no further intervention , whereas postconditioning was performed within 1 minute of reflow by 4 episodes of 1-minute inflation and 1-minute deflation of the angioplasty balloon . Infa rct size was assessed by measuring total creatine kinase release over 72 hours . Area at risk and collateral blood flow were estimated on left ventricular and coronary angiograms . No adverse events occurred in the postconditioning group . Determinants of infa rct size , including ischemia time , size of the area at risk , and collateral flow , were comparable between the 2 groups . Area under the curve of creatine kinase release was significantly reduced in the postconditioning compared with the control group , averaging 208 984±26 576 compared with 326 095±48 779 ( arbitrary units ) in control subjects , ie , a 36 % reduction in infa rct size . Blush grade , a marker of myocardial reperfusion , was significantly increased in postconditioned compared with control subjects : 2.44±0.17 versus 1.95±0.27 , respectively ( P<0.05 ) . Conclusions — This study suggests that postconditioning by coronary angioplasty protects the human heart during acute myocardial infa rct ion Background Reduction of infa rct size by ischemic postconditioning ( IPost ) has been reported in smaller proof‐of‐concept clinical studies , but has not been confirmed in other smaller studies . The principle needs to be evaluated in larger groups of ST‐elevation myocardial infa rct ion ( STEMI ) patients before being implemented in clinical practice . This study assessed the effect of ischemic postcoditioning ( IPost ) on infa rct size in patients with STEMI treated by primary percutaneous coronary intervention ( PCI ) . Methods and Results Patients with first‐time STEMI , < 6 hours from symptom onset , referred to primary PCI were r and omized to IPost or control groups . IPost was administered by 4 cycles of 1‐minute reocclusion and 1‐minute reperfusion , starting 1 minute after opening , followed by stenting . In the control group , stenting was performed immediately after reperfusion . The primary endpoint was infa rct size measured by cardiac magnetic resonance after 4 months . A total of 272 patients were r and omized . Infa rct size ( percent of left ventricular mass ) after 4 months ( median values and interquartile range ) was 14.4 % ( 7.7 , 24.6 ) and 13.5 % ( 8.1 , 19.3 ) in the control group and IPost group , respectively ( P=0.18 ) . No significant impact of IPost was found when controlling for baseline risk factors of infa rct size in a multivariate linear regression model ( P=0.16 ) . The effects of IPost on secondary endpoints , including markers of necrosis , myocardial salvage , and ejection fraction , as well as adverse cardiac events during follow‐up , were consistently neutral . Conclusions In contrast to several smaller trials reported previously , we found no significant effects of IPost on infa rct size or secondary study outcomes . Clinical Trial Registration URL : http://www . clinical trials.gov Unique identifier : NCT.No . PO1506 Background —Postconditioning has been suggested to reduce myocardial damage during primary percutaneous coronary intervention ( PPCI ) in patients with ST-segment – elevation myocardial infa rct ion . However , because clinical experience is limited , we examined the cardioprotective effects of postconditioning , using cardiac MRI in patients treated with PPCI . Methods and Results —One hundred eighteen patients with ST-segment – elevation myocardial infa rct ion referred for PPCI were r and omly assigned to have either conventional PPCI or PPCI with postconditioning .  Postconditioning was performed immediately after obtained reperfusion with 4 balloon occlusions , each lasting 30 seconds , followed by 30 seconds of reperfusion . The primary end point was myocardial salvage after 3 months as judged by delayed enhancement cardiac MRI . We found a 19 % relative reduction of infa rct size in the postconditioning group ( 51±16 % of total area at risk versus 63±17 % , P<0.01 ) , corresponding to a 31 % increase in salvage ratio . The number of patients developing heart failure was significantly fewer in the postconditioning group ( 27 % versus 46 % , P=0.048 ) . No significant evidence of interaction between the impact of postconditioning and the location of the culprit lesion or size of the myocardium at risk was detected ( P=0.21 and P=0.71 ) . Conclusions —Mechanical postconditioning reduces infa rct size in patients with ST-segment – elevation myocardial infa rct ion treated with PPCI . The impact of mechanical postconditioning seems to be independent of the size of myocardium at risk . Clinical Trial Registration —URL : http://www . clinical trials.gov . Unique Identifier : NCT00507156 AIMS To assess the short- and long-term effects of postconditioning ( p-cond ) on infa rct size , extent of myocardial salvage , and left ventricular ejection fraction ( LVEF ) in a series of patients presenting with evolving ST-elevation myocardial infa rct ion ( STEMI ) . Previous studies have shown that p-cond during primary percutaneous coronary intervention ( PCI ) confers protection against ischaemia-reperfusion injury and thus might reduce myocardial infa rct size . METHODS AND RESULTS Seventy-nine patients undergoing PCI for a first STEMI with TIMI grade flow 0 - 1 and no collaterals were r and omized to p-cond ( n= 39 ) or controls ( n= 40 ) . Postconditioning was performed by applying four consecutive cycles of 1 min balloon inflation , each followed by 1 min deflation . Infa rct size , myocardial salvage , and LVEF were assessed by cardiac-MRI 1 week and 6 months after MI . Postconditioning was associated with lower myocardial salvage ( 4.1 ± 7.2 vs. 9.1 ± 5.8 % in controls ; P= 0.004 ) and lower myocardial salvage index ( 18.9 ± 27.4 vs. 30.9 ± 20.5 % in controls ; P= 0.038 ) . No significant differences in infa rct size and LVEF were found between the groups at 1 week and 6 months after MI . CONCLUSION This r and omized study suggests that p-cond during primary PCI does not reduce infa rct size or improve myocardial function recovery at both short- and long-term follow-up and might have a potential harmful effect Background — We previously demonstrated that ischemic postconditioning decreases creatine kinase release , a surrogate marker for infa rct size , in patients with acute myocardial infa rct ion . Our objective was to determine whether ischemic postconditioning could afford ( 1 ) a persistent infa rct size limitation and ( 2 ) an improved recovery of myocardial contractile function several months after infa rct ion . Methods and Results — Patients presenting within 6 hours of the onset of chest pain , with suspicion for a first ST-segment – elevation myocardial infa rct ion , and for whom the clinical decision was made to treat with percutaneous coronary intervention , were eligible for enrollment . After reperfusion by direct stenting , 38 patients were r and omly assigned to a control ( no intervention ; n=21 ) or postconditioned group ( repeated inflation and deflation of the angioplasty balloon ; n=17 ) . Infa rct size was assessed both by cardiac enzyme release during early reperfusion and by 201thallium single photon emission computed tomography at 6 months after acute myocardial infa rct ion . At 1 year , global and regional contractile function was evaluated by echocardiography . At 6 months after acute myocardial infa rct ion , single photon emission computed tomography rest-redistribution index ( a surrogate for infa rct size ) averaged 11.8±10.3 % versus 19.5±13.3 % in the postconditioned versus control group ( P=0.04 ) , in agreement with the significant reduction in creatine kinase and troponin I release observed in the postconditioned versus control group ( −40 % and −47 % , respectively ) . At 1 year , the postconditioned group exhibited a 7 % increase in left ventricular ejection fraction compared with control ( P=0.04 ) . Conclusions — Postconditioning affords persistent infa rct size reduction and improves long-term functional recovery in patients with acute myocardial infa rct ion Flaws in the design , conduct , analysis , and reporting of r and omised trials can cause the effect of an intervention to be underestimated or overestimated . The Cochrane Collaboration ’s tool for assessing risk of bias aims to make the process clearer and more No-reflow phenomenon is a serious complication of percutaneous coronary intervention ( PCI ) which is closely related to the incidence of major adverse cardiovascular events . It has been demonstrated that Postconditioning ( PostC ) during primary PCI confers protection against ischemia – reperfusion injury and thus might reduce infa rct size . However , whether PostC may exert its beneficial effects on acute myocardial infa rct ion ( AMI ) patients by reducing no-reflow phenomenon is still unknown . Sixty two patients diagnosed with ST-elevation AMI were r and omly assigned to study group ( n = 32 ) or control group ( n = 30 ) . Blood sample s were obtained and assayed for creatine kinase MB ( CK-MB ) and high-sensitive C-reactive protein ( hs-CRP ) . Determinants of reflow , including final thrombolysis in myocardial infa rct ion ( TIMI ) grade -3 flow , ST-segment resolution ( STR ) , myocardial blush grade s-3 ( MBG-3 ) and corrected thrombolysis in myocardial infa rct ion frame count ( cTFC ) , were comparative between the two groups . Compared with control group , more patients in study group were identified as the final TIMI grade -3 flow ( 81.3 vs. 56.7 % , P = 0.036 ) , MBG-3 ( 23 vs. 14 % , P = 0.043 ) and STR ≥50 % ( 93.8 vs. 73.3 % , P = 0.029 ) , while patients in study group had less cTFC ( 28.5 ± 9.1 vs. 37.4 ± 12.4 , P = 0.002 ) After PCI , study group was associated with lower levels of CK-MB ( 2,397.6 ± 470.2 vs. 2,159.9 ± 485.5 , P = 0.028 ) , Troponin-I ( 197.5 ± 32.5 vs. 154 ± 43.1 , P = 0.041 ) and hs-CRP ( 5.5 ± 4.5 vs. 9.5 ± 5.2 mg/L , P = 0.019 ) in comparison with control group . Left ventricle ejection fraction was better in the study group than in the control group ( 55.1 ± 9.8 vs. 42.9 ± 10.7 , P = 0.042 ) . PostC could improve myocardial reperfusion in patients with ST-elevation AMI undergoing PCI by reducing no-reflow . However , due to the limited sample size , the results of our study should not be considered conclusive BACKGROUND Postconditioning has been shown to reduce infa rct size during reperfusion ( < 72 hours ) . However , it is unknown whether the infa rct size reduction with postconditioning is a long-term effect after 
    Output:
    
No effects by IPost on ST-segment resolution or on the majority of adverse clinical events were observed during follow up , except the incidence of congestive heart failure was found .
Evidence from this study suggests no cardioprotection from IPost , on surrogate and the majority of clinical end points .