***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 Left ventricular ( LV ) volumes have important prognostic implication s , but are commonly underestimated . We sought accuracy and reproducibility of LV volume measurement by live 3-dimensional ( 3D ) echocardiography ( 3DE ) and TI-201 single photon emission computed tomography ( SPECT ) , compared with cardiac magnetic resonance imaging ( MRI ) . METHODS In all , 30 patients ( age 62 + /- 9 years , 23 men ) underwent LV volume assessment with 3DE , SPECT , and cardiac MRI after myocardial infa rct ion .  LV volumes were measured using a semiautomated border detection algorithm for 3DE , gated SPECT software for SPECT , and a 3D display for MRI . Results of 3DE and SPECT volumes were compared with MRI as the st and ard of reference . RESULTS The 3DE volumes showed excellent correlation with cardiac MRI ( end-diastolic volume [ EDV ] , r = 0.90 , P = .001 ; end-systolic volume [ ESV ] , r = 0.94 , P = .001 ) , as did SPECT ( EDV , r = 0.89 , P = .001 ; ESV , r = 0.95 , P = .001 ) . However , both 3DE and SPECT underestimated LV volumes . The mean MRI EDV was 179 + /- 56 mL compared with 3DE ( mean difference , -10 + /- 26 mL , P = .04 ) and SPECT ( mean difference , -58 + /- 28 mL , P < .001 ) . There was a significant difference between SPECT EDV and 3DE ( mean difference , -48 + /- 31 mL , P < .001 ) . The mean MRI ESV was 96 + /- 54 mL and this was underestimated by SPECT ( mean difference , -22 + /- 19 mL , P < .001 ) , but not by 3DE ( mean difference , -0.9 + /- 19 mL , P = not significant ) . ESV was also underestimated when SPECT was compared with 3DE ( mean difference , -22 + /- 27 mL , P < .001 ) . The results of 3DE were reproducible with excellent intraobserver ( ESV , r = 0.98 , -2 + /- 6 mL ; EDV , r = 0.98 , -1 + /- 6 mL , P = .001 ) and interobserver ( ESV , r = 0.97 , -2 + /- 6 mL ; EDV , r = 0.95 , -3 + /- 10 mL , P = .001 ) correlation . CONCLUSION We have shown that 3DE is accurate and reproducible for the measurement of LV volumes for risk assessment in chronic ischemic heart disease and dilated cardiomyopathy . Furthermore , 3DE is more accurate than TI-201 SPECT with less underestimation of LV volumes BACKGROUND Surgical ventricular reconstruction has been proposed as a treatment option in heart failure patients with left ventricular ( LV ) aneurysm . The feasibility of this procedure has some limitations , and extensive preoperative evaluation is necessary to give the correct indication . For this purpose , magnetic resonance imaging ( MRI ) is currently considered the gold st and ard , providing accurate quantification of LV shape , size , and global and regional function together with the assessment of myocardial scar and mitral regurgitation severity . The aim of this study was to evaluate the accuracy of real-time three-dimensional echocardiography ( RT3DE ) as a potential alternative to MRI for this evaluation . METHODS A total of 52 patients with ischemic cardiomyopathy and LV aneurysm underwent a comprehensive analysis with two-dimensional echocardiography , RT3DE , and MRI . RESULTS Excellent correlation ( r=0.97 , p<0.001 ) and agreement were found between RT3DE and MRI for quantification of LV volumes , ejection fraction , and sphericity index ; in a segment-to-segment comparison , RT3DE was shown to be accurate also for the analysis of wall motion abnormalities ( k=0.62 ) and LV regional thickness ( k=0.56 ) as a marker of myocardial scar . In contrast , two-dimensional echocardiography significantly underestimated these variables . Furthermore , mitral regurgitant volume assessed by RT3DE showed excellent correlation ( r=0.93 ) with regurgitant volume measured by MRI , without significant bias ( = -0.7 mL/beat ) . CONCLUSIONS In the management of heart failure patients with LV aneurysm , RT3DE provides an accurate and comprehensive assessment , including quantification of LV size , shape , global systolic function , regional wall motion , and myocardial scar together with precise evaluation of the severity of mitral regurgitation Background — Cardiac CT ( CCT ) and real-time 3D echocardiography ( RT3DE ) are being used increasingly in clinical cardiology . CCT offers superb spatial and contrast resolution , result ing in excellent endocardial definition . RT3DE has the advantages of low cost , portability , and live 3D imaging without offline reconstruction . We sought to compare both CCT and RT3DE measurements of left ventricular size and function with the st and ard reference technique , cardiac MR ( CMR ) . Methods and Results — In 31 patients ,  RT3DE data sets ( Philips 7500 ) and long-axis CMR ( Siemens , 1.5 T ) and CCT ( Toshiba , 16-slice MDCT ) images were obtained on the same day without β-blockers . All images were analyzed to obtain end-systolic and end-diastolic volumes and ejection fractions using the same rotational analysis to eliminate possible analysis -related differences . Intertechnique agreement was tested through linear regression and Bl and -Altman analyses . Repeated measurements were performed to determine intraobserver and interobserver variability . Both CCT and RT3DE measurements result ed in high correlation ( r2>0.85 ) compared with CMR . However , CCT significantly overestimated end-diastolic and end-systolic volumes ( 26 and 19 mL ; P<0.05 ) , result ing in a small but significant bias in ejection fraction ( −2.8 % ) . RT3DE underestimated end-diastolic and end-systolic volumes only slightly ( 5 and 6 mL ) , with no significant bias in EF ( 0.3 % ; P=0.68 ) . The limits of agreement with CMR were comparable for the 2 techniques . The variability in the CCT measurements was roughly half of that in either RT3DE or CMR values . Conclusions — CCT provides highly reproducible measurements of left ventricular volumes , which are significantly larger than CMR values . RT3DE measurements compared more favorably with the CMR reference , albeit with higher variability Background —&bgr;-Blocking agents improve functional status and reduce morbidity in mild-to-moderate heart failure , but it is not known whether they produce such benefits in severe heart failure . Methods and Results —We r and omly assigned 2289 patients with symptoms of heart failure at rest or on minimal exertion and with an ejection fraction < 25 % ( but not volume-overloaded ) to double-blind treatment with either placebo ( n=1133 ) or carvedilol ( n=1156 ) for an average of 10.4 months . Carvedilol reduced the combined risk of death or hospitalization for a cardiovascular reason by 27 % ( P = 0.00002 ) and the combined risk of death or hospitalization for heart failure by 31 % ( P = 0.000004 ) . Patients in the carvedilol group also spent 27 % fewer days in the hospital for any reason ( P = 0.0005 ) and 40 % fewer days in the hospital for heart failure ( P < 0.0001 ) . These differences were as a result of both a decrease in the number of hospitalizations and a shorter duration of each admission . More patients felt improved and fewer patients felt worse in the carvedilol group than in the placebo group after 6 months of maintenance therapy ( P = 0.0009 ) . Carvedilol-treated patients were also less likely than placebo-treated patients to experience a serious adverse event ( P = 0.002 ) , especially worsening heart failure , sudden death , cardiogenic shock , or ventricular tachycardia . Conclusion —In euvolemic patients with symptoms at rest or on minimal exertion , the addition of carvedilol to conventional therapy ameliorates the severity of heart failure and reduces the risk of clinical deterioration , hospitalization , and other serious adverse clinical events Real-time 3-dimensional echocardiographic continuous imaging ( CIM ) with contrast underestimates left ventricular ( LV ) volumes . We studied the effects of dual-triggered ( DT ) acquisition on the accuracy of LV volume measurements for patients with poor acoustic windows .  Real-time 3-dimensional echocardiographic imaging was performed in 20 patients during LV opacification ( Definity ) on the same day as cardiac magnetic resonance imaging . Both CIM and DT data were analyzed using custom software to calculate end-systolic volume ( ESV ) and end-diastolic volume ( EDV ) , which were compared with the cardiac magnetic resonance reference . CIM correlated well with the cardiac magnetic resonance reference ( EDV : r = 0.89 ; ESV : r = 0.93 ) , but underestimated EDV and ESV by 17 % and 19 % , respectively . In contrast , DT result ed in higher correlation ( EDV : r = 0.95 ; ESV : r = 0.96 ) and smaller biases ( 9 % and 6 % , respectively ) . In conclusion , because the accuracy of LV volume measurements depends on the acquisition strategy of contrast-enhanced real-time 3-dimensional echocardiographic images , the use of DT instead of the conventional CIM acquisition is recommended BACKGROUND Patients with reduced left ventricular function after myocardial infa rct ion are at risk for life-threatening ventricular arrhythmias . This r and omized trial was design ed to evaluate the effect of an implantable defibrillator on survival in such patients . METHODS Over the course of four years , we enrolled 1232 patients with a prior myocardial infa rct ion and a left ventricular ejection fraction of 0.30 or less . Patients were r and omly assigned in a 3:2 ratio to receive an implantable defibrillator ( 742 patients ) or conventional medical therapy ( 490 patients ) . Invasive electrophysiological testing for risk stratification was not required . Death from any cause was the end point . RESULTS The clinical characteristics at base line and the prevalence of medication use at the time of the last follow-up visit were similar in the two treatment groups . During an average follow-up of 20 months , the mortality rates were 19.8 percent in the conventional-therapy group and 14.2 percent in the defibrillator group . The hazard ratio for the risk of death from any cause in the defibrillator group as compared with the conventional-therapy group was 0.69 ( 95 percent confidence interval , 0.51 to 0.93 ; P=0.016 ) . The effect of defibrillator therapy on survival was similar in subgroup analyses stratified according to age , sex , ejection fraction , New York Heart Association class , and the QRS interval . CONCLUSIONS In patients with a prior myocardial infa rct ion and advanced left ventricular dysfunction , prophylactic implantation of a defibrillator improves survival and should be considered as a recommended therapy BACKGROUND It is not known whether the treatment of patients with asymptomatic left ventricular dysfunction reduces mortality and morbidity . We studied the effect of an angiotensin-converting -- enzyme inhibitor , enalapril , on total mortality and mortality from cardiovascular causes , the development of heart failure , and hospitalization for heart failure among patients with ejection fractions of 0.35 or less who were not receiving drug treatment for heart failure . METHODS Patients were r and omly assigned to receive either placebo ( n = 2117 ) or enalapril ( n = 2111 ) at doses of 2.5 to 20 mg per day in a double-blind trial . Follow-up averaged 37.4 months . RESULTS There were 334 deaths in the placebo group , as compared with 313 in the enalapril group ( reduction in risk , 8 percent by the log-rank test ; 95 percent confidence interval , -8 percent [ an increase of 8 percent ] to 21 percent ; P = 0.30 ) . The reduction in mortality from cardiovascular causes was larger but was not statistically significant ( 298 deaths in the placebo group vs. 265 in the enalapril group ; risk reduction , 12 percent ; 95 percent confidence interval , -3 to 26 percent ; P = 0.12 ) . When we combined patients in whom heart failure developed and those who died , the total number of deaths and cases of heart failure was lower in the enalapril group than in the placebo group ( 630 vs. 818 ; risk reduction , 29 percent ; 95 percent confidence interval , 21 to 36 percent ; P less than 0.001 ) . In addition , fewer patients given enalapril  died or were hospitalized for heart failure ( 434 in the enalapril group ; vs. 518 in the placebo group ; risk reduction , 20 percent ; 95 percent confidence interval , 9 to 30 percent ; P less than 
    Output:
    
Three-dimensional echocardiography underestimates volumes and has wide limits of agreement , but compared with traditional 2D methods in these carefully performed studies , 3DE is more accurate for volumes and more precise in all 3 measurements