***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 — We aim ed to investigate the cardiac effects of left bundle-branch block ( LBBB ) using myocardial contrast echocardiography ( MCE ) to ascertain the value of MCE for detecting coronary artery disease ( CAD ) and to uncover the mechanism that affects the accuracy of single-photon emission computed tomography ( SPECT ) in these patients . Methods and Results — Sixty-three symptomatic LBBB patients ( group A ) , 10 left ventricular ejection fraction – matched control subjects without LBBB and no CAD ( group B ) , and 10 normal control subjects ( group C ) underwent resting echocardiography . Rest and vasodilator MCE and SPECT were undertaken in LBBB patients . Septal ( SW ) and posterior wall ( PW ) thickness , thickening , quantitative myocardial blood flow ( MBF ) , and MBF reserve were measured . SW/PW thickness and percentage thickening ratios were lower ( P<0.01 and P<0.05 , respectively ) in group A compared with both groups B and C , but resting SW/PW MBF and MBF reserve ratios were similar in all 3 groups . MBF reserve but not MBF was reduced in groups A and B ( 2.2±0.7 versus 2.2±0.2 ; P=0.98 ) compared with group C ( 3.1±0.5 ; P<0.01 ) . SW thickness was an independent predictor ( P=0.006 ) of SPECT perfusion defects in LBBB patients without CAD . MCE ( 92 % ) had a sensitivity similar to SPECT ( 92 % ) ; however , the specificity of MCE ( 95 % ) was superior ( P<0.0001 ) to SPECT ( 47 % ) for the detection of CAD . Conclusions — Despite asymmetrical reduction in SW thickness and function , MBF is preserved and MBF reserve is homogeneously reduced in LBBB patients with left ventricular systolic dysfunction . Because of partial volume effects , the accuracy of SPECT for detecting CAD was significantly compromised compared with MCE in this patient cohort BACKGROUND Qualitative interpretation of myocardial contrast echocardiography ( MCE ) improves the accuracy of wall-motion analysis for assessment of coronary artery disease ( CAD ) . We examined the feasibility and accuracy of quantitative MCE for diagnosis of CAD . METHODS Dipyridamole/exercise stress MCE ( destruction-replenishment protocol with real-time imaging ) was performed in 90 patients undergoing quantitative coronary angiography , 48 of whom had significant ( > 50 % ) stenoses .  MCE was repeated with exercise alone in 18 patients .  Myocardial blood flow ( A*beta ) was obtained from blood volume ( A ) and time to refill ( beta ) . RESULTS Quantification of flow reserve was feasible in 88 % . The mean A*beta reserve in the anterior wall was significantly impaired for patients with left anterior descending coronary artery disease ( n = 28 ) compared with those with no disease ( 1.6 + /- 1.2 vs 4.0 + /- 2.5 , P < or = .001 ) . This reflected impaired beta reserve , with no difference in the A reserve . Applying a receiver operating characteristic curve derived cutoff of 2.0 for A*beta reserve , quantitative MCE was 76 % sensitive and 71 % specific for the diagnosis of significant left anterior descending coronary artery stenosis . Posterior circulation results were similar , with 78 % sensitivity and 59 % specificity for detection of posterior CAD . Overall , quantitative MCE was similarly sensitive to qualitative approach for diagnosis of CAD ( 88 % vs 93 % ) , but with lower specificity ( 52 % vs 65 % , P = .07 ) . In 18 patients restudied with pure exercise stress , the mean myocardial blood flow reserve was less than after combined stress ( 2.1 + /- 1.6 vs 3.7 + /- 1.9 , P = .01 ) . CONCLUSION Quantitative MCE is feasible for the diagnosis of CAD with dipyridamole/exercise stress . Dipyridamole prolongs postexercise hyperemia , augmenting the degree of hyperemia at the time of imaging OBJECTIVES To assess the acceptability and feasibility of functional tests as a gateway to angiography for management of coronary artery disease ( CAD ) , the ability of diagnostic strategies to identify patients who should undergo revascularisation , patient outcomes in each diagnostic strategy , and the most cost-effective diagnostic strategy for patients with suspected or known CAD . DESIGN A rapid systematic review of economic evaluations of alternative diagnostic strategies for CAD was carried out . A pragmatic and generalisable r and omised controlled trial was undertaken to assess the use of the functional cardiac tests : angiography ( controls ) ; single photon emission computed tomography ( SPECT ) ; magnetic resonance imaging ( MRI ) ; stress echocardiography . SETTING The setting was Papworth Hospital NHS Foundation Trust , a tertiary cardiothoracic referral centre . PARTICIPANTS Patients with suspected or known CAD and an exercise test result that required non-urgent angiography . INTERVENTIONS Patients were r and omised to one of the four initial diagnostic tests . MAIN OUTCOME MEASURES Eighteen months post-r and omisation : exercise time ( modified Bruce protocol ) ; cost-effectiveness compared with angiography ( diagnosis , treatment and follow-up costs ) . The aim was to demonstrate equivalence in exercise time between those r and omised to functional tests and those r and omised to angiography [ defined as the confidence interval ( CI ) for mean difference from angiography within 1 minute ] . RESULTS The 898 patients were r and omised to  angiography  ( n = 222 ) , SPECT ( n = 224 ) , MRI ( n = 226 ) or stress echo ( n = 226 ) . Initial diagnostic tests were completed successfully with unequivocal results for 98 % of angiography , 94 % of SPECT ( p = 0.05 ) , 78 % of MRI ( p < 0.001 ) and 90 % of stress echocardiography patients ( p < 0.001 ) . Some 22 % of SPECT patients , 20 % of MRI patients and 25 % of stress echo patients were not subsequently referred for an angiogram . Positive functional tests were confirmed by positive angiography in 83 % of SPECT patients , 89 % of MRI patients and 84 % of stress echo patients . Negative functional tests were followed by positive angiograms in 31 % of SPECT patients , 52 % of MRI patients and 48 % of stress echo patients tested . The proportions that had coronary artery bypass graft surgery were 10 % ( angiography ) , 11 % ( MRI ) and 13 % ( SPECT and stress echo ) and percutaneous coronary intervention 25 % ( angiography ) , 18 % ( SPECT ) and 23 % ( MRI and stress echo ) . At 18 months , comparing SPECT and stress echo with angiography , a clinical ly significant difference in total exercise time can be ruled out . The MRI group had significantly shorter mean total exercise time of 35 seconds and the upper limit of the CI was 1.14 minutes less than in the angiography group , so a difference of at least 1 minute can not be ruled out . At 6 months post-treatment , SPECT and angiography had equivalent mean exercise time . Compared with angiography , the MRI and stress echo groups had significantly shorter mean total exercise time of 37 and 38 seconds , respectively , and the upper limit of both CIs was 1.16 minutes , so a difference of at least 1 minute can not be ruled out . The differences were mainly attributable to revascularised patients . There were significantly more non-fatal adverse events in the stress echo group , mostly admissions for chest pain , but no significant difference in the number of patients reporting events . Mean ( 95 % CI ) total additional costs over 18 months , compared with angiography , were 415 pounds ( -310 pounds to 1084 pounds ) for SPECT , 426 pounds ( -247 pounds to 1088 pounds ) for MRI and 821 pounds ( 10 pounds to 1715 pounds ) for stress echocardiography , with very little difference in quality -adjusted life-years ( QALYs ) amongst the groups ( less than 0.04 QALYs over 18 months ) . Cost-effectiveness was mainly influenced by test costs , clinicians ' willingness to trust negative functional tests and by a small number of patients who had a particularly difficult clinical course . CONCLUSIONS Between 20 and 25 % of patients can avoid invasive testing using functional testing as a gateway to angiography , without substantial effects on outcomes . The SPECT strategy was as useful as angiography in identifying patients who should undergo revascularisation and the additional cost was not significant , in fact it would be reduced further by restricting the rest test to patients who have a positive stress test . MRI had the largest number of test failures and , in this study , had the least practical use in screening patients with suspected CAD , although it had similar outcomes to stress echo and is still an evolving technology . Stress echo patients had a 10 % test failure rate , significantly shorter total exercise time and time to angina at 6 months post-treatment , and a greater number of adverse events , leading to significantly higher costs . Given the level of skill required for stress echo , it may be best to reserve this test for those who have a contraindication to SPECT and are unable or unwilling to have MRI . Further research , using blinded re assessment of functional test results and angiograms , is required to formally assess diagnostic accuracy . Longer-term cost-effectiveness analysis , and further studies of MRI and new generation computed tomography are also required OBJECTIVE To assess the cost-effectiveness of spiral CT for the diagnosis of acute pulmonary embolism . DESIGN Computer-based cost-effectiveness analysis . PATIENTS Simulated cohort of 1,000 patients with suspected acute pulmonary embolism ( PE ) , with a prevalence of 28.4 % , as in the Prospect i ve Investigation of Pulmonary Embolism Diagnosis study . INTERVENTIONS Using a decision- analysis model , seven diagnostic strategies were compared , which incorporated combinations of ventilation-perfusion ( V/Q ) scans , duplex ultrasound of the legs , spiral CT , and conventional pulmonary angiography . MEASUREMENTS AND RESULTS Expected survival and cost ( in Canadian dollars ) at 3 months were estimated . Four of the strategies yielded poorer survival at higher cost . The three remaining strategies were as follows : ( 1 ) V/Q + /- leg ultrasound + /- spiral CT , with an expected survival of 953.4 per 1,000 patients and a cost of $ 1,391 per patient ; ( 2 ) V/Q + /- leg ultrasound + /- pulmonary angiography ( the " traditional " algorithm ) , with an expected survival of 953.7 per 1,000 patients and a cost of $ 1,416 per patient ; and ( 3 ) spiral CT + /- leg ultrasound , with an expected survival of 958.2 per 1,000 patients and a cost of $ 1,751 per patient . The traditional algorithm was then excluded by extended dominance . The cost per additional life saved was $ 70,833 for spiral CT + /- leg ultrasound relative to V/Q + /- leg ultrasound + /- spiral CT . CONCLUSIONS Spiral CT can replace pulmonary angiography in patients with nondiagnostic V/Q scan and negative leg ultrasound findings . This approach is likely as effective as- and possibly less expensive than-the current algorithm for diagnosis of acute PE . When spiral CT is the initial diagnostic test , followed by leg ultrasound , expected survival improves but costs are also considerably higher . These findings were robust to variations in the assumed sensitivity and specificity of spiral CT INTRODUCTION Myocardial contrast echocardiography ( MCE ) is a new imaging modality for diagnosing ischaemic heart disease ( IHD ) . AIM The aim of this study was to assess 1 ) the feasibility of MCE during supine bicycle stress and 2 ) the value of this method in the diagnosis of IHD . METHODS Supine bicycle stress was performed in 44 consecutive patients ( pts ) referred for coronary angiography with an intermediate pre-test probability of IHD .  MCE was carried out at peak stress and during recovery ( once the heart rate returned to the pre-exercise value ) . During MCE an ultrasound contrast agent ( Sonovue ) was administered intravenously in a continuous mode using an infusion pump ( BR-INF 100 , Bracco Research ) . The acquired images were qualitatively assessed for perfusion and wall motion abnormalities . The 18-segment division of the left ventricle was used in the analysis . Coronary angiography was performed in all pts within 15 days of the exercise test . A quantitative analysis of coronary artery stenoses was carried out using the CAAS system . RESULTS MCE could not be performed in 2 pts due to technical difficulties . Coronary angiography revealed significant coronary artery stenosis in 25 pts . The sensitivity and specificity of MCE  in the diagnosis of IHD were 92.0 % and 82.4 % , respectively . The positive and negative predictive values were found to be 88.5 % and 87.5 % , respectively , while the agreement between coronary angiography and MCE was 88.1 % ( kappa=0.75 ) . CONCLUSIONS MCE during supine bicycle stress and continuous intravenous administration of an ultrasound contrast agent is a feasible technique and allows accurate diagnosis of IHD in pts in whom the pre-test probability of the disease is intermediate OBJECTIVE To estimate the impact of contrast stress echocardiography on re source 
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It worked well in the right chambers of the heart , but dissolved when passing through the pulmonary capillaries and so was unable to provide contrast in the left side .
Notably , critically ill patients on ventilators and those with lung problems are more likely to generate poor or ' suboptimal ' echocardiograms than other patients , as are obese patients and those who 've undergone recent chest operations .
Based on the results of these studies the following conclusions were made : Stress ECHO with contrast has a higher diagnostic accuracy in the diagnosis of CAD than stress ECHO ( without contrast).Stress ECHO with contrast seems to have a similar diagnostic accuracy to 99 technetium SPECT.The addition of contrast to ECHO in patients with suboptimal ECHO results significantly improves interpretability of the results .There is not a statistically significantly higher mortality rate in patients who receive contrast compared to those who do not