human
***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: Objective To examine the reproducibility and responsiveness to change of a six minute walk test and a quality of life measure in elderly patients with heart failure . Design Longitudinal within patient study . Subjects 60 patients with heart failure ( mean age 82 years ) attending a geriatric outpatient clinic , 45 of whom underwent a repeat assessment three to eight weeks later . Main outcome measures Subjects underwent a st and ardised six minute walk test and completed the chronic heart failure question naire ( CHQ ) , a heart failure specific quality of life question naire .  Intraclass correlation coefficients ( ICC ) were calculated using a r and om effects one way analysis of variance as a measure of reproducibility . Guyatt ’s responsiveness coefficient and effect sizes were calculated as measures of responsiveness to change . Results 24 patients reported no major change in cardiac status , while seven had deteriorated and 14 had improved between the two clinic visits . Reproducibility was satisfactory ( ICC > 0.75 ) for the six minute walk test , for the total CHQ score , and for the dyspnoea , fatigue , and emotion domains of the CHQ . Effect sizes for all measures were large ( > 0.8 ) , and responsiveness coefficients were very satisfactory ( > 0.7 ) . Effect sizes for detecting deterioration were greater than those for detecting improvement . Conclusions Quality of life assessment and a six minute walk test are reproducible and responsive measures of cardiac status in frail , very elderly patients with heart failure The assessment of functional capacity reflects the ability to perform activities of daily living that require sustained aerobic metabolism . The integrated efforts and health of the pulmonary , cardiovascular , and skeletal muscle systems dictate an individual ’s functional capacity . Numerous investigations have demonstrated that the assessment of functional capacity provides important diagnostic and prognostic information in a wide variety of clinical and research setting s. This scientific statement , an up date of the previously published American Heart Association ( AHA ) document,1 highlights the major clinical and research applications of functional capacity assessment . For a comprehensive review of exercise testing , the reader is referred to the American College of Cardiology (ACC)/AHA Guidelines for Exercise Testing.2,3 Functional capacity is the ability of an individual to perform aerobic work as defined by the maximal oxygen uptake ( Vo2max ) , that is , the product of cardiac output and arteriovenous oxygen ( a−Vo2 ) difference at physical exhaustion , as shown in the following equation : ! [Formula][1 ] Where HR indicates heart rate and SV indicates stroke volume . Because Vo2max typically is achieved by exercise that involves only about half of the total body musculature , it is generally believed that Vo2max is limited by maximal cardiac output rather than peripheral factors.4 Although Vo2max is measured in liters of oxygen per minute , it usually is expressed in milliliters of oxygen per kilogram of body weight per minute to facilitate intersubject comparisons . In addition , functional capacity , particularly when estimated from the work rate achieved rather than directly measured Vo , is frequently expressed in metabolic equivalents ( METs ) , with 1 MET representing the resting energy expenditure ( ≈3.5 mL O2 · kg−1 · min−1 ) . In this instance , functional capacity is commonly expressed clinical ly as a multiple of the resting metabolic rate . Vo2max … [ 1 ] : CONTEXT Heart failure is often preceded by isolated systolic hypertension , but the effectiveness of antihypertensive treatment in preventing heart failure is not known . OBJECTIVE To assess the effect of diuretic-based antihypertensive stepped-care treatment on the occurrence of heart failure in older persons with isolated systolic hypertension . DESIGN Analysis of data from a multicenter , r and omized , double-blind , placebo-controlled clinical trial . PARTICIPANTS A total of 4736 persons aged 60 years and older with systolic blood pressure between 160 and 219 mm Hg and diastolic blood pressure below 90 mm Hg who participated in the Systolic Hypertension in the Elderly Program ( SHEP ) . INTERVENTION Stepped-care antihypertensive drug therapy , in which the step 1 drug is chlorthalidone ( 12.5 - 25 mg ) or matching placebo , and the step 2 drug is atenolol ( 25 - 50 mg ) or matching placebo . MAIN OUTCOME MEASURES Fatal and nonfatal heart failure . RESULTS During an average of 4.5 years of follow-up , fatal or nonfatal heart failure occurred in 55 of 2365 patients r and omized to active therapy and 105 of the 2371 patients r and omized to placebo ( relative risk [ RR ] , 0.51 ; 95 % confidence interval [ CI ] , 0.37 - 0.71 ; P<.001 ; number needed to treat to prevent 1 event [ NNT ] , 48 ) . Among patients with a history of or electrocardiographic evidence of prior myocardial infa rct ion ( MI ) , the RR was 0.19 ( 95 % CI , 0.06 - 0.53 ; P=.002 ; NNT , 15 ) . Older patients , men , and those with higher systolic blood pressure or a history of or electrocardiographic evidence of MI at baseline had higher risk of developing heart failure . CONCLUSION In older persons with isolated systolic hypertension , stepped-care treatment based on low-dose chlorthalidone exerted a strong protective effect in preventing heart failure . Among patients with prior MI , an 80 % risk reduction was observed BACKGROUND We prospect ively evaluated the potential of the 6-minute walk test compared with peak VO2 in predicting outcome of patients with New York Heart Association ( NYHA ) class II or III heart failure . METHODS AND RESULTS Patients with a history of heart failure caused by systolic dysfunction were included . The combined final outcome ( death or hospitalization for heart failure ) was used as the judgment criterion . One hundred twenty-one patients ( age 59+/-11 years ; left ventricular ejection fraction 29.6%+/-13 % ) were included and followed for 1.53+/-0.98 years . Patients were separated into two groups according to outcome : group 1 ( G1 , 74 patients ) , without events , and group 2 ( G2 , 47 patients ) , who reached the combined end point . Peak VO2 was clearly different between G1 and G2 ( 18.5+/-4 vs. 13.9+/-4 ml/kg/min , p=0.0001 ) but not the distance walked ( 448+/-92 vs 410+/-126 m ; p=0.084 , not significant ) . Survival analysis showed that unlike peak VO2 , the distance covered was barely distinguishable between the groups ( p < 0.08 ) . However , receiver operating characteristic curves revealed that the best performances for the  6-minute walk test were obtained for subjects walking < or = 300 m. These patients had a worse prognosis than those walking farther ( p=0.013 ) . In this subset of patients , there was a significant correlation between distance covered and peak VO2 ( r=0.65 , p=0.011 ) . Thus it appears that the more severely affected patients have a daily activity level relatively close to their maximal exercise capacity . Nevertheless , the 300 m threshold suggested by this study needs to be vali date d in an independent population . CONCLUSIONS A distance walked in 6 minutes < or = 300 m can predict outcome . Moreover , in these cases there is a significant correlation between the 6-minute walk test and peak VO2 demonstrating the potential of this simple procedure as a first-line screening test for this subset of patients AIMS The 6-min walk test may serve as a more simple clinical tool to assess functional capacity in congestive heart failure than determination of peak oxygen uptake by cardiopulmonary exercise testing . The purpose of the study was to prospect ively examine whether the distance ambulated during a 6-min walk test ( i ) correlates with peak oxygen uptake , ( ii ) allows peak oxygen uptake to be predicted , and ( iii ) provides prognostic information similar to peak oxygen uptake in patients with dilated cardiomyopathy and left ventricular ejection fraction < or = 35 % . METHODS AND RESULTS In 113 patients ( age : 54+/-12 years , NYHA : 2.2+/-0.8 ) with dilated cardiomyopathy ( left ventricular ejection fraction 19+/-7 % ) a 6-min walk test and cardiopulmonary exercise testing were performed . The 6-min walk test and peak oxygen uptake were closely correlated at the initial visit ( r=0.68 , n=113 ) , as well as after 263+/-114 ( r=0.71 , n=28 ) and 381+/-170 days ( r=0.74 , n=14 ) . During serial exercise testing the 6-min walk test allowed peak oxygen uptake to be reliably predicted ( r=0.76 between calculated and real peak oxygen uptake ) . After 528+/-234 days , 42 patients were hospitalized due to worsening heart failure and /or died from cardiovascular causes . Compared to clinical ly stable patients , these 42 patients walked a shorter distance ( 423+/-104 vs 501+/-95 m , P<0.001 ) and had a lower peak oxygen uptake ( 12.7+/-4.0 vs 17.4 + 5.6 ml x min(-1 ) x kg(-1 ) , P<0.001 ) . By univariate analysis the 6-min walk test outperformed other prognostic parameters such as left ventricular ejection fraction , cardiac index and plasma norepinephrine concentration and conferred a prognostic power similar to peak oxygen uptake . This predictive value could be further improved in a multivariate model , by combining the 6-min walk test with independent variables , such as left ventricular ejection fraction or cardiac index . CONCLUSION The 6-min walk test correlated with peak oxygen uptake when tested serially over the course of the disease . Although both tests define two distinct domains of functional capacity , the 6-min walk test provides prognostic information very similar to peak oxygen uptake in congestive heart failure patients with dilated cardiomyopathy BACKGROUND Peak oxygen uptake ( peak VO(2 ) ) is a reference parameter in the assessment of functional capacity of patients with chronic heart failure , but the procedure for cardiopulmonary exercise testing with expired gas analysis is complex and expensive , so more simple and available methods are desirable . METHODS We compared the usefulness of a time-limited walk test , the 6-minute walk test ( 6-MT ) , with that of a symptom-limited walk test , the shuttle walk test ( SWT ) , in the evaluation of patients with moderate to severe chronic heart failure . We prospect ively studied 46 clinical ly stable patients in New York Heart Association class II to IV heart failure with left ventricular ejection fraction < 40 % ( aged 53 + /- 10 years , ejection fraction 23 % + /- 8 % , New York Heart Association functional class 2.8 + /- 0.7 ) . Each patient performed two 6-MT , two SWT and a cardiopulmonary exercise testing within 2 weeks . RESULTS We found a close correlation between distance walked in SWT and peak VO(2 ) ( r = 0.83 , P < .001 ) and a moderate correlation between distance in 6-MT and peak VO(2 ) ( r = 0.69 , P < .001 ) . Both walk tests showed to be reproducible after just one practice walk . All patients who walked > 450 m in SWT had a peak VO(2 ) > 14 mL/kg/min . The overall discriminatory accuracy for SWT distance was greater than that for 6-MT distance for predicting a peak VO(2 ) < 14 mL/kg/min ( area under receiver operator characteristic curves 0.97 and 0.83 respectively , P = .02 ) . Stepwise multivariate regression analysis , including clinical , exercise testing , echocardiographic , radionuclide-angiographic , and rest hemodynamic data , showed that distance walked in SWT was the only independent predictor of peak VO(2 ) ( P < .001 ) and the strongest predictor of percent achieved of age- and sex-predicted peak VO(2 ) ( % PVO(2 ) ) ( P < .001 ) , with only age offering additional information ( P = .02 ) . CONCLUSIONS The SWT shows to be a feasible and safe method to evaluate patients with chronic heart failure that strongly and independently predicts peak VO(2 ) and % PVO(2 . ) This symptom-limited walk test seems to be more useful than 6-MT in the assessment of functional capacity in these patients This study investigated the use of an incremental , externally-paced 10 m shuttle walk test ( SWT ) as an objective , reliable and predictive test of functional capacity in patients with heart failure ( CHF ) . The SWT was compared to a 6 minute walk test ( 6WT ) and a maximal symptom-limited treadmill peak oxygen consumption ( VO2peak ) test . Experiment 1 examined the reproducibility of the SWT . Two SWF trials were performed and distance ambulated ( DA ) , heart rate ( HR ) and  rate of perceived exertion ( RPE ) results compared . In experiment 2 , SWT , 6WT , and VO2 peak tests were performed and HR . RPE and ambulatory VO2 compared . The SWT demonstrated strong test/retest reliability for DA ( r = 0.98 ) . HR ( r = 0.96 ) and RPE ( r = 0.89 ) . Treadmill VO2 peak was significantly correlated with DA during the SWT ( r = 0.83 , P < 0.05 ) , but not the 6WT . SWT peak VO2 ( 18.5 + 
    Output:
    
agent
Comparison of the studies investigating reliability shows that the 6MWT has good reproducibility .
The 6MWT demonstrates moderate correlation with peak VO(2 ) levels , and ability to predict VO(2 ) ( functional capacity ) dependent on distance walked .
Cut-off distances vary from 300 to 490 meters depending on the study ; if total distance walked remains equal or less than these values , the 6MWT retains its strong predictive value .
The 6MWT has good reliability , moderate validity , and a significant ability to predict functional capacity in patients with CHF who do not walk greater than 490 meters
***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: Objective To examine the reproducibility and responsiveness to change of a six minute walk test and a quality of life measure in elderly patients with heart failure . Design Longitudinal within patient study . Subjects 60 patients with heart failure ( mean age 82 years ) attending a geriatric outpatient clinic , 45 of whom underwent a repeat assessment three to eight weeks later . Main outcome measures Subjects underwent a st and ardised six minute walk test and completed the chronic heart failure question naire ( CHQ ) , a heart failure specific quality of life question naire .  Intraclass correlation coefficients ( ICC ) were calculated using a r and om effects one way analysis of variance as a measure of reproducibility . Guyatt ’s responsiveness coefficient and effect sizes were calculated as measures of responsiveness to change . Results 24 patients reported no major change in cardiac status , while seven had deteriorated and 14 had improved between the two clinic visits . Reproducibility was satisfactory ( ICC > 0.75 ) for the six minute walk test , for the total CHQ score , and for the dyspnoea , fatigue , and emotion domains of the CHQ . Effect sizes for all measures were large ( > 0.8 ) , and responsiveness coefficients were very satisfactory ( > 0.7 ) . Effect sizes for detecting deterioration were greater than those for detecting improvement . Conclusions Quality of life assessment and a six minute walk test are reproducible and responsive measures of cardiac status in frail , very elderly patients with heart failure The assessment of functional capacity reflects the ability to perform activities of daily living that require sustained aerobic metabolism . The integrated efforts and health of the pulmonary , cardiovascular , and skeletal muscle systems dictate an individual ’s functional capacity . Numerous investigations have demonstrated that the assessment of functional capacity provides important diagnostic and prognostic information in a wide variety of clinical and research setting s. This scientific statement , an up date of the previously published American Heart Association ( AHA ) document,1 highlights the major clinical and research applications of functional capacity assessment . For a comprehensive review of exercise testing , the reader is referred to the American College of Cardiology (ACC)/AHA Guidelines for Exercise Testing.2,3 Functional capacity is the ability of an individual to perform aerobic work as defined by the maximal oxygen uptake ( Vo2max ) , that is , the product of cardiac output and arteriovenous oxygen ( a−Vo2 ) difference at physical exhaustion , as shown in the following equation : ! [Formula][1 ] Where HR indicates heart rate and SV indicates stroke volume . Because Vo2max typically is achieved by exercise that involves only about half of the total body musculature , it is generally believed that Vo2max is limited by maximal cardiac output rather than peripheral factors.4 Although Vo2max is measured in liters of oxygen per minute , it usually is expressed in milliliters of oxygen per kilogram of body weight per minute to facilitate intersubject comparisons . In addition , functional capacity , particularly when estimated from the work rate achieved rather than directly measured Vo , is frequently expressed in metabolic equivalents ( METs ) , with 1 MET representing the resting energy expenditure ( ≈3.5 mL O2 · kg−1 · min−1 ) . In this instance , functional capacity is commonly expressed clinical ly as a multiple of the resting metabolic rate . Vo2max … [ 1 ] : CONTEXT Heart failure is often preceded by isolated systolic hypertension , but the effectiveness of antihypertensive treatment in preventing heart failure is not known . OBJECTIVE To assess the effect of diuretic-based antihypertensive stepped-care treatment on the occurrence of heart failure in older persons with isolated systolic hypertension . DESIGN Analysis of data from a multicenter , r and omized , double-blind , placebo-controlled clinical trial . PARTICIPANTS A total of 4736 persons aged 60 years and older with systolic blood pressure between 160 and 219 mm Hg and diastolic blood pressure below 90 mm Hg who participated in the Systolic Hypertension in the Elderly Program ( SHEP ) . INTERVENTION Stepped-care antihypertensive drug therapy , in which the step 1 drug is chlorthalidone ( 12.5 - 25 mg ) or matching placebo , and the step 2 drug is atenolol ( 25 - 50 mg ) or matching placebo . MAIN OUTCOME MEASURES Fatal and nonfatal heart failure . RESULTS During an average of 4.5 years of follow-up , fatal or nonfatal heart failure occurred in 55 of 2365 patients r and omized to active therapy and 105 of the 2371 patients r and omized to placebo ( relative risk [ RR ] , 0.51 ; 95 % confidence interval [ CI ] , 0.37 - 0.71 ; P<.001 ; number needed to treat to prevent 1 event [ NNT ] , 48 ) . Among patients with a history of or electrocardiographic evidence of prior myocardial infa rct ion ( MI ) , the RR was 0.19 ( 95 % CI , 0.06 - 0.53 ; P=.002 ; NNT , 15 ) . Older patients , men , and those with higher systolic blood pressure or a history of or electrocardiographic evidence of MI at baseline had higher risk of developing heart failure . CONCLUSION In older persons with isolated systolic hypertension , stepped-care treatment based on low-dose chlorthalidone exerted a strong protective effect in preventing heart failure . Among patients with prior MI , an 80 % risk reduction was observed BACKGROUND We prospect ively evaluated the potential of the 6-minute walk test compared with peak VO2 in predicting outcome of patients with New York Heart Association ( NYHA ) class II or III heart failure . METHODS AND RESULTS Patients with a history of heart failure caused by systolic dysfunction were included . The combined final outcome ( death or hospitalization for heart failure ) was used as the judgment criterion . One hundred twenty-one patients ( age 59+/-11 years ; left ventricular ejection fraction 29.6%+/-13 % ) were included and followed for 1.53+/-0.98 years . Patients were separated into two groups according to outcome : group 1 ( G1 , 74 patients ) , without events , and group 2 ( G2 , 47 patients ) , who reached the combined end point . Peak VO2 was clearly different between G1 and G2 ( 18.5+/-4 vs. 13.9+/-4 ml/kg/min , p=0.0001 ) but not the distance walked ( 448+/-92 vs 410+/-126 m ; p=0.084 , not significant ) . Survival analysis showed that unlike peak VO2 , the distance covered was barely distinguishable between the groups ( p < 0.08 ) . However , receiver operating characteristic curves revealed that the best performances for the  6-minute walk test were obtained for subjects walking < or = 300 m. These patients had a worse prognosis than those walking farther ( p=0.013 ) . In this subset of patients , there was a significant correlation between distance covered and peak VO2 ( r=0.65 , p=0.011 ) . Thus it appears that the more severely affected patients have a daily activity level relatively close to their maximal exercise capacity . Nevertheless , the 300 m threshold suggested by this study needs to be vali date d in an independent population . CONCLUSIONS A distance walked in 6 minutes < or = 300 m can predict outcome . Moreover , in these cases there is a significant correlation between the 6-minute walk test and peak VO2 demonstrating the potential of this simple procedure as a first-line screening test for this subset of patients AIMS The 6-min walk test may serve as a more simple clinical tool to assess functional capacity in congestive heart failure than determination of peak oxygen uptake by cardiopulmonary exercise testing . The purpose of the study was to prospect ively examine whether the distance ambulated during a 6-min walk test ( i ) correlates with peak oxygen uptake , ( ii ) allows peak oxygen uptake to be predicted , and ( iii ) provides prognostic information similar to peak oxygen uptake in patients with dilated cardiomyopathy and left ventricular ejection fraction < or = 35 % . METHODS AND RESULTS In 113 patients ( age : 54+/-12 years , NYHA : 2.2+/-0.8 ) with dilated cardiomyopathy ( left ventricular ejection fraction 19+/-7 % ) a 6-min walk test and cardiopulmonary exercise testing were performed . The 6-min walk test and peak oxygen uptake were closely correlated at the initial visit ( r=0.68 , n=113 ) , as well as after 263+/-114 ( r=0.71 , n=28 ) and 381+/-170 days ( r=0.74 , n=14 ) . During serial exercise testing the 6-min walk test allowed peak oxygen uptake to be reliably predicted ( r=0.76 between calculated and real peak oxygen uptake ) . After 528+/-234 days , 42 patients were hospitalized due to worsening heart failure and /or died from cardiovascular causes . Compared to clinical ly stable patients , these 42 patients walked a shorter distance ( 423+/-104 vs 501+/-95 m , P<0.001 ) and had a lower peak oxygen uptake ( 12.7+/-4.0 vs 17.4 + 5.6 ml x min(-1 ) x kg(-1 ) , P<0.001 ) . By univariate analysis the 6-min walk test outperformed other prognostic parameters such as left ventricular ejection fraction , cardiac index and plasma norepinephrine concentration and conferred a prognostic power similar to peak oxygen uptake . This predictive value could be further improved in a multivariate model , by combining the 6-min walk test with independent variables , such as left ventricular ejection fraction or cardiac index . CONCLUSION The 6-min walk test correlated with peak oxygen uptake when tested serially over the course of the disease . Although both tests define two distinct domains of functional capacity , the 6-min walk test provides prognostic information very similar to peak oxygen uptake in congestive heart failure patients with dilated cardiomyopathy BACKGROUND Peak oxygen uptake ( peak VO(2 ) ) is a reference parameter in the assessment of functional capacity of patients with chronic heart failure , but the procedure for cardiopulmonary exercise testing with expired gas analysis is complex and expensive , so more simple and available methods are desirable . METHODS We compared the usefulness of a time-limited walk test , the 6-minute walk test ( 6-MT ) , with that of a symptom-limited walk test , the shuttle walk test ( SWT ) , in the evaluation of patients with moderate to severe chronic heart failure . We prospect ively studied 46 clinical ly stable patients in New York Heart Association class II to IV heart failure with left ventricular ejection fraction < 40 % ( aged 53 + /- 10 years , ejection fraction 23 % + /- 8 % , New York Heart Association functional class 2.8 + /- 0.7 ) . Each patient performed two 6-MT , two SWT and a cardiopulmonary exercise testing within 2 weeks . RESULTS We found a close correlation between distance walked in SWT and peak VO(2 ) ( r = 0.83 , P < .001 ) and a moderate correlation between distance in 6-MT and peak VO(2 ) ( r = 0.69 , P < .001 ) . Both walk tests showed to be reproducible after just one practice walk . All patients who walked > 450 m in SWT had a peak VO(2 ) > 14 mL/kg/min . The overall discriminatory accuracy for SWT distance was greater than that for 6-MT distance for predicting a peak VO(2 ) < 14 mL/kg/min ( area under receiver operator characteristic curves 0.97 and 0.83 respectively , P = .02 ) . Stepwise multivariate regression analysis , including clinical , exercise testing , echocardiographic , radionuclide-angiographic , and rest hemodynamic data , showed that distance walked in SWT was the only independent predictor of peak VO(2 ) ( P < .001 ) and the strongest predictor of percent achieved of age- and sex-predicted peak VO(2 ) ( % PVO(2 ) ) ( P < .001 ) , with only age offering additional information ( P = .02 ) . CONCLUSIONS The SWT shows to be a feasible and safe method to evaluate patients with chronic heart failure that strongly and independently predicts peak VO(2 ) and % PVO(2 . ) This symptom-limited walk test seems to be more useful than 6-MT in the assessment of functional capacity in these patients This study investigated the use of an incremental , externally-paced 10 m shuttle walk test ( SWT ) as an objective , reliable and predictive test of functional capacity in patients with heart failure ( CHF ) . The SWT was compared to a 6 minute walk test ( 6WT ) and a maximal symptom-limited treadmill peak oxygen consumption ( VO2peak ) test . Experiment 1 examined the reproducibility of the SWT . Two SWF trials were performed and distance ambulated ( DA ) , heart rate ( HR ) and  rate of perceived exertion ( RPE ) results compared . In experiment 2 , SWT , 6WT , and VO2 peak tests were performed and HR . RPE and ambulatory VO2 compared . The SWT demonstrated strong test/retest reliability for DA ( r = 0.98 ) . HR ( r = 0.96 ) and RPE ( r = 0.89 ) . Treadmill VO2 peak was significantly correlated with DA during the SWT ( r = 0.83 , P < 0.05 ) , but not the 6WT . SWT peak VO2 ( 18.5 + 
    Output:
    