***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: BACKGROUND Recently concluded multicenter studies have shown that none of an array of echocardiographic indicators of ventricular dyssynchrony have enough sensitivity and specificity for predicting response to cardiac resynchronization therapy ( CRT ) . Inotropic contractile reserve ( ICR ) on dobutamine stress echocardiography can differentiate viable myocardium from scar and is a predictor of improvement in regional and global left ventricular function in patients with cardiomyopathy . Its role in patients undergoing CRT is unknown . The aim of this study was to evaluate the role of ICR in predicting response to CRT in patients with markedly remodeled left ventricles . METHODS Fifty-four patients ( mean age , 69±11 years ; 63 % men ) referred for clinical ly indicated CRT were evaluated . All patients underwent low-dose dobutamine stress echocardiography to assess for ICR , defined as an improvement in contractility in more than five of 16 left ventricular segments . RESULTS During a mean follow-up period of 206±167 days , 31 patients ( 57 % ) were responders , as defined by a 5-point increase in ejection fraction after CRT . The presence of ICR was a stronger predictor of response to CRT ( area under the curve , 0.94 ; χ2=39.0 ; P<.0001 ) compared with dyssynchrony ( area under the curve , 0.74 ; χ2=10.07 ; P=.002 ) . It was a significant predictor of response ( odds ratio , 2.84 ; 95 % confidence interval , 1.59 to 5.09 ; P<.0001 ) , even after controlling for the other predictors , and provided incremental prognostic value beyond that provided by QRS duration and dyssynchrony ( increase in area under the curve from 0.47 to 0.75 to 0.93 ; P=.030 and P=.008 ) . CONCLUSIONS In patients referred for CRT , ICR was a stronger predictor of response and provided incremental value beyond that of current known predictors of response to CRT ( dyssynchrony and QRS duration ) . Dobutamine stress echocardiography may have an important role in identifying CRT responders , and further multicenter studies are needed to confirm this AIMS Contradicting reports have been published regarding the relation between a dobutamine-induced increase in either cardiac dyssynchrony or left-ventricular ejection fraction ( LVEF ) and the response to cardiac resynchronization therapy ( CRT ) . Using  apical rocking ( ApRock ) as surrogate dyssynchrony parameter , we investigated the dobutamine stress echocardiography (DSE)-induced changes in left-ventricular ( LV ) dyssynchrony and LVEF and their potential pathophysiological interdependence . METHODS AND RESULTS Fifty-eight guideline -selected CRT c and i date s were prospect ively enrolled for low-dose DSE . Dyssynchrony was quantified by the amplitude of ApRock . An LVEF increase during stress of > 5 % was regarded significant . Scar burden was assessed by magnetic resonance imaging . Mean follow-up after CRT implantation was 41 ± 13 months for the occurrence of cardiac death . ApRock during DSE predicted CRT response ( AUC 0.88 , 95 % CI 0.77 - 0.99 , P < 0.001 ) and correlated inversely with changes in EF ( r = -0.6 , P < 0.001 ) . Left-ventricular ejection fraction changes during DSE were not associated with CRT response ( P = 0.082 ) . Linear regression analysis revealed an inverse association of LVEF changes during DSE with both , total scar burden ( B = -2.67 , 95CI -3.77 to -1.56 , P < 0.001 ) and the DSE-induced change in ApRock amplitude ( B = -1.23 , 95 % CI -1.53 to -0.94 , P < 0.001 ) . Kaplan-Meier analysis revealed that DSE-induced increase in ApRock , but not LVEF , was associated with improved long-term survival . CONCLUSION During low-dose DSE in CRT c and i date s with baseline dyssynchrony , myocardial contractile reserve predominantly results in more dyssynchrony , but less in an increase in LVEF . Dyssynchrony at baseline and its dobutamine-induced changes are predictive of both response and long-term survival following CRT Background — Data from single-center studies suggest that echocardiographic parameters of mechanical dyssynchrony may improve patient selection for cardiac resynchronization therapy ( CRT ) . In a prospect i ve , multicenter setting , the Predictors of Response to CRT ( PROSPECT ) study tested the performance of these parameters to predict CRT response . Methods and Results — Fifty-three centers in Europe , Hong Kong , and the United States enrolled 498 patients with st and ard CRT indications ( New York Heart Association class III or IV heart failure , left ventricular ejection fraction ≤35 % , QRS ≥130 ms , stable medical regimen ) . Twelve echocardiographic parameters of dyssynchrony , based on both conventional and tissue Doppler – based methods , were evaluated after site training in acquisition methods and blinded core laboratory analysis . Indicators of positive CRT response were improved clinical composite score and ≥15 % reduction in left ventricular end-systolic volume at 6 months . Clinical composite score was improved in 69 % of 426 patients , whereas left ventricular end-systolic volume decreased ≥15 % in 56 % of 286 patients with paired data . The ability of the 12 echocardiographic parameters to predict clinical composite score response varied widely , with sensitivity ranging from 6 % to 74 % and specificity ranging from 35 % to 91 % ; for predicting left ventricular end-systolic volume response , sensitivity ranged from 9 % to 77 % and specificity from 31 % to 93 % . For all the parameters , the area under the receiver-operating characteristics curve for positive clinical or volume response to CRT was ≤0.62 . There was large variability in the analysis of the dyssynchrony parameters . Conclusion — Given the modest sensitivity and specificity in this multicenter setting despite training and central analysis , no single echocardiographic measure of dyssynchrony may be recommended to improve patient selection for CRT beyond current guidelines . Efforts aim ed at reducing variability arising from technical and interpretative factors may improve the predictive power of these echocardiographic parameters in a broad clinical setting OBJECTIVE To underst and whether patients with post-ischemic dilated cardiomyopathy and myocardial viability ( MV ) could benefit from cardiac resynchronization therapy ( CRT ) in terms of clinical , echocardiographic and neuro- hormonal parameters compared to patients without MV . METHODS One hundred and four consecutive patients were enrolled in a prospect i ve observational cohort study . Using dobutamine stress echocardiography , 2 groups were identified : group A of 51 patients with MV  and group B of 53 patients without MV .  All patients were implanted with biventricular pacing devices combined with an internal cardioverter-defibrillator . Clinical , echocardiographic and neuro-hormonal parameters were evaluated at baseline and at six month follow-up . Analysis of variance for repeated measures on each variable suggestive of remodeling was performed . We considered responder every patient with : decrease of > 15 % in left ventricular volumes and /or improvement in left ventricular ejection fraction of > 5 % in addition to NYHA class improvement . RESULTS All the variables improved in both groups ( time effect ) . Comparing the two groups ( group effect ) , the following variables were significantly better in group A : N-terminal pro-B-type natriuretic peptide ( p=0.02 ) , NYHA class ( p=0.003 ) , reverse remodeling ( RR ) ( p=0.007 ) , dP/dt ( p=0.005 ) , left ventricular ejection fraction ( p=0.009 ) , 3rd sound ( p=0.01 ) , and left ventricular end-systolic volume after the first week ( p=0.035 ) . RR occurred at the first week after CRT only in Group A and was maintained for all the time of this study . The maximum difference of the decrease of left ventricular volumes between the two groups occurred after the first week ( p<0.001 ) . CONCLUSION Patients with MV responded better than patients without MV with a significant improvement after the first week from CRT BACKGROUND The clinical response to biventricular pacing is unpredictable , especially in patients with ischemic cardiomyopathy . OBJECTIVES The purpose of this study was to prospect ively examine the relationship between the extent of myocardial viability and the response to cardiac resynchronization therapy . METHODS Twenty-one patients with ischemic left ventricular ( LV ) dysfunction ( left ventricular ejection fraction [ LVEF ] 21 + /- 5 % ) , New York Heart Association ( NYHA ) functional class III-IV , and QRS > 120 ms received biventricular devices .  Myocardial viability was assessed by myocardial contrast echocardiography , and a perfusion score index ( PSI ) was calculated from summed segmental perfusion scores . LV performance was assessed by echocardiography on the day after implantation and at 6 months . RESULTS PSI was closely correlated with acute improvement in LVEF ( P = .003 , r = 0.65 ) , stroke volume ( P = .02 , r = 0.54 ) , and end-systolic volume ( P = .05 , r = -0.49 ) . PSI also correlated with early diastolic LV relaxation ( E ' , P < .05 , r = 0.50 ) and global myocardial performance or Tei index ( P = .003 , r = 0.63 ) . By multiple linear regression analysis , PSI provided incremental predictive value to the degree of dyssynchrony , measured by tissue Doppler imaging , for predicting improvement in LVEF . At 6 months , PSI remained positively correlated with improvement in ventricular performance and with reduction in LV end-diastolic dimension ( P = .003 , r = -0.68 ) . PSI also influenced the clinical variables of NYHA class , 6-minute walk distance , quality -of-life score , and number of hospitalizations for heart failure . CONCLUSION In patients with ischemic cardiomyopathy , the extent of myocardial viability predicts acute and long-term improvement in LV performance , exercise tolerance , and reduction in LV end-diastolic dimension with biventricular pacing A substantial proportion of patients who meet the current guidelines for cardiac resynchronization therapy ( CRT ) fail to respond to this pacing modality . Although appropriate patient selection and left ventricular ( LV ) lead location have been ascribed as determinants of CRT response , the interaction among contractile reserve , dynamics of dyssynchrony , and lead location is not well understood . The present study prospect ively evaluated the effect of contractile reserve and dobutamine-induced changes in LV synchrony , in relation to the LV lead location , as predictors of the response to CRT . In the present study , 31 patients were prospect ively evaluated and underwent low-dose dobutamine echocardiography .  The dobutamine-induced increase in ejection fraction ( contractile reserve [ CR ] ) was measured , and the most mechanically delayed segment was identified to classify patients into 2 groups . Group 1 had a CR of > 20 % and a LV lead position concordant with the mechanically delayed segment . Group 2 included the remaining patients ( i.e. , low CR , discordant LV lead position , or both ) . Patients in group 1 were significantly more likely to have an echocardiographic response at 6 months ( 80 % of group 1 vs 29 % of group 2 , p = 0.018 ) and had an improved 2-year heart failure hospitalization-free survival rate ( 90 % in group 1 vs 33 % in group 2 , p = 0.006 ) . In conclusion , low-dose dobutamine echocardiography provides information that can help to predict responders to CRT . The response rates and heart failure hospitalization-free survival were improved in those patients with a CR > 20 % and an LV lead tip concordant with the most delayed mechanical segment BACKGROUND Cardiac resynchronization therapy ( CRT ) is effective in selected patients with heart failure ( HF ) . Nevertheless , the nonresponder rate remains high . The low-dose dobutamine stress-echo ( DSE ) test detects the presence of left ventricular ( LV ) contractile reserve ( LVCR ) in HF patients of any etiology and may be useful in predicting response to resynchronization . OBJECTIVE The purpose of this study was to present the results of the LODO-CRT trial , which evaluated whether LVCR presence at baseline increases the chances of response to CRT . METHODS LODO-CRT is a multicenter prospect i ve study that enrolled CRT c and i date s according to guidelines . LVCR presence was defined as an LV ejection fraction increase > 5 units during DSE test . CRT response is assessed at 6-month follow-up as an LV end-systolic volume reduction ≥10 % . RESULTS Two hundred seventy-one patients were enrolled . The DSE test was feasible without complications in 99 % of patients . Nine patients died from noncardiac disease , and 31 presented inadequate data . Two hundred thirty-one patients were included in the analysis . Mean patient age was 67 ± 10 years ; 95 % were in New York Heart Association class III , and 42 % had HF of 
    Output:
    
The presence of global contractile reserve at baseline , as assessed by dobutamine stress echocardiography , is associated with a higher chance of CRT response in patients with heart failure