Impact of contrast echocardiography on diagnostic algorithms: pharmacoeconomic implications

Multimodal Cardiac Imaging in the Assessment of Patients Who Have Suffered a Cardioembolic Stroke: A Review

Cardioembolic strokes account for 20-25% of all ischaemic strokes, with their incidence increasing with age. Cardiac imaging plays a crucial role in identifying cardioembolic causes of stroke, with early and accurate identification affecting treatment, preventing recurrence, and reducing stroke incidence. Echocardiography serves as the mainstay of cardiac evaluation. Transthoracic echocardiography (TTE) is the first line in the basic evaluation of structural heart disorders, valvular disease, vegetations, and intraventricular thrombus. It can be used to measure chamber size and systolic/diastolic function. Trans-oesophageal echocardiography (TOE) yields better results in identifying potential cardioembolic sources of stroke and should be strongly considered, especially if TTE does not yield adequate results. Cardiac computed tomography and cardiac magnetic resonance imaging provide better soft tissue characterisation, high-grade anatomical information, spatial and temporal visualisation, and image reconstruction in multiple planes, especially with contrast. These techniques are useful in cases of inconclusive echocardiograms and can be used to detect and characterise valvular lesions, thrombi, fibrosis, cardiomyopathies, and aortic plaques. Nuclear imaging is not routinely used, but it can be used to assess left-ventricular perfusion, function, and dimensions and may be useful in cases of infective endocarditis. Its use should be considered on a case-by-case basis. The accuracy of each imaging modality depends on the likely source of cardioembolism, and the choice of imaging approach should be tailored to individual patients.

Management of left ventricular thrombus: a narrative review

Left ventricular thrombus (LVT) is a serious complication of acute myocardial infarction (MI) and also non-ischemic cardiomyopathies. We performed a narrative literature review, manual-search of reference lists of included articles and relevant reviews. Our literature review indicates that the incidence of LVT following acute MI has decreased, probably due to improvement in patient care as a result of better and earlier reperfusion techniques. Predictors of LVT include anterior MI, involvement of left ventricular (LV) apex (regardless of the coronary territory affected), LV akinesis or dyskinesis, reduced LV ejection fraction (LVEF), severe diastolic dysfunction and large infarct size. LVT is associated with increased risk of systemic embolism, stroke, cardiovascular events and death, and there is evidence that anticoagulant therapy for at least 3 months can reduce the risk of these events. Cardiac magnetic resonance (CMR) has the highest diagnostic accuracy for LVT, followed by echocardiography with the use of echocardiographic contrast agents (ECAs). Although current guidelines suggest use of vitamin K antagonist (VKA) for a minimum of 3 to 6 months, there is growing evidence of the benefits of direct acting oral anticoagulants in treatment of LVT. Embolic events appear to occur even after resolution of LVT suggesting that anticoagulant therapy needs to be considered for a longer period in some cases. Recommendations for the use of triple therapy in the presence of the LVT are mostly based on extrapolation from outcome data in patients with atrial fibrillation (AF) and MI. We conclude that the presence of LVT is more likely in patients with anterior ST-segment elevation MI (STEMI) (involving the apex) and reduced ejection fraction (EF). LVT should be considered a marker of increased long-term thrombotic risk that may persist even after thrombus resolution. Ongoing clinical trials are expected to elucidate the best management strategies for patients with LVT.

Ultrasound imaging artifacts: How to recognize them and how to avoid them

Echocardiography has become a critical tool in clinical cardiology in evaluating cardiac physiology and diagnosing cardiac disease states. However, imaging artifacts are commonly encountered and often lead to misdiagnoses of life-threatening diseases, such as aortic dissection and ventricular thrombus. It is, thus, critical for clinicians to understand these artifacts to avoid these misdiagnoses and protect patients from undue intervention. Artifacts can be broken down into two categories: those from violation of ultrasound system assumptions and those from interference by external equipment and devices. This review article discusses the most commonly encountered artifacts by category, explains their physical mechanisms, elaborates on their most common presentations, and instructs clinicians on how to avoid their misinterpretation.

Impact of Contrast Echocardiography on Assessment of Ventricular Function and Clinical Diagnosis in Routine Clinical Echocardiography: Korean Multicenter Study

Background

Fundamental echocardiography has some drawbacks in patients with difficult-to-image echocardiograms. The aim of this study is to evaluate impact of contrast echocardiography (CE) on ventricular function assessment and clinical diagnosis in routine clinical echocardiography.

Methods

Two hundred sixty patients were prospectively enrolled over 3 years in 12 medical centers in Korea. General image quality, the number of distinguishable segments, ability to assess regional wall motion, left ventricular (LV) apex and right ventricle (RV) visualization, LV ejection fraction, changes in diagnostic or treatment plan were documented after echocardiography with and without ultrasound contrast agent.

Results

Poor or uninterpretable general image was 31% before contrast use, and decreased to 2% (p<0.05) after contrast use. The average number of visualized LV segments was 9.53 before contrast use, and increased to 14.46 (p<0.001) after contrast use. The percentage of poor or not seen LV regional wall motion was decreased from 28.4% to 3.5% (p<0.001). The percentage of poor or not seen LV apex and RV was decreased from 49.4% to 2.4% (p<0.001), from 30.5% to 10.5% (p<0.001), respectively. Changes in diagnostic procedure and treatment plan after CE were 30% and 29.6%, respectively.

Conclusion

Compared to fundamental echocardiography, CE impacted LV function assessment and clinical decision making in Korean patients who undergo routine echocardiography.

Quality Assessment in Dobutamine Stress Echocardiography: What are the Clinical Predictors Associated With a Non-Diagnostic Test?

Background

Non-diagnostic dobutamine stress echocardiography (ndDSE, failure to achieve 85% of maximal predicted heart rate (HR) without evidence of inducible ischemia) is an important limitation affecting quality of DSE testing. The objectives of this study were to identify the clinical variables associated with a non-diagnostic Dobutamine Stress Echocardiogram (ndDSE) and further evaluate the patterns of subsequent testing for myocardial ischemia.

Methods

Consecutive DSE’s over a 17 month period (January 2008 to June 2009) were studied. Baseline demographics, medical history, and vital signs were collected. Subsequent testing was determined for up to 6 months after the initial DSE. Univariate and multivariate logistic regression analysis was performed to identify clinical factors associated with ndDSE.

Results

Of 467 total DSE, 314 (67%) were negative for ischemia, 69 (15%) were positive, and 84 (18%) were ndDSE. Of those recommended for further nuclear MPI testing 12 (14%) had an ndDSE compared to 16 (4%) patients with a diagnostic DSE (P = 0.001). Fifty percent of the ndDSE nuclear MPI tests were positive for ischemia. In the univariate analysis, Diabetes Mellitus (DM; P = 0.003), calcium channel antagonist (CCA) use (P = 0.047), Hypertension (HTN; P = 0.06), low baseline HR (P < 0.001), and younger age group (P = 0.02) were predictive of ndDSE. Of these, all except CCA use remained independent predictors of ndDSE in multivariate analysis. A 4 variable model for predicting ndDSE was developed from the multivariate logistic regression displayed in Table 1 (age and baseline HR were categorized and scored 0-2; DM and HTN were scored as 0 (absent) or 1 (present)). Figure 2 demonstrates how risk of ndDSE correlated with a higher score, with each increment having an odds ratio of 2.1 (P < 0.001).

Conclusions

DM, HTN, younger age, and lower baseline HR affect the quality of DSE testing, resulting in non-diagnostic tests. A model combining these factors can identify patients most likely to have this outcome. Identification of this cohort may improve referral patterns and improve the quality of stress testing.

Improved detection of left ventricular thrombi and spontaneous echocontrast by tissue harmonic imaging in patients with myocardial infarction

BACKGROUND

Tissue harmonic imaging (THI) reduces near-field and side-lobe artifacts. This could improve recognition of cardiac masses, including thrombi and spontaneous echocontrast (SEC), a known thromboembolic risk factor.

OBJECTIVES

We tested the hypothesis that THI improves detection of left ventricular (LV) thrombi and SEC compared with transthoracic fundamental imaging in patients with recent myocardial infarction.

METHODS

In all, 118 consecutive patients with recent myocardial infarction were studied at predischarge. The echocardiographic examination was performed in both fundamental imaging and THI modality and evaluated by 3 skilled and 3 nonexperienced observers for recognition of LV thrombosis and SEC.

RESULTS

THI increased LV thrombi diagnosis by 25% by skilled observers and by 50% by nonexperienced readers, reducing the number of false-positive diagnoses by 67%. Also, compared with fundamental imaging, THI improved recognition of LV SEC by both experienced and nonexperienced observers by 56% and 62%, respectively.

CONCLUSIONS

The improved recognition of LV thrombosis and SEC by THI in patients with myocardial infarction is clinically relevant allowing appropriate treatment and prognostic stratification. Therefore, routine use of THI should be recommended when studying such patients in clinical practice.

Peak C-reactive protein concentration correlates with left ventricular thrombus formation diagnosed by contrast echocardiographic left ventricular opacification in patients with a first anterior acute myocardial infarction

BACKGROUND

Wall motion abnormality in the apical legion of the left ventricle (LV) with stagnant flow alone is not sufficient to identify patients at high risk for LV thrombus formation among those with first anterior acute myocardial infarction (AMI). The aim of this study was to identify the determinants of LV thrombus formation using contrast echocardiography.

METHODS AND RESULTS

In 75 patients with first anterior AMI, standard and contrast echocardiography was performed to detect LV thrombus. Although LV thrombus was found in 10 patients (13%) using standard echocardiography, it was found in 15 patients (20%) using contrast echocardiography. Apical stagnant flow was observed in 14 patients (93%) with LV thrombus. In addition, patients with LV thrombus had a higher peak C-reactive protein (CRP) concentration (18.2+/-4.3 vs 7.9+/-5.5 mg/dl, p<0.0001). In multivariate analysis, only peak CRP concentration was identified as an independent predictor of LV thrombus (p=0.02, odds ratio: 1.400, confidence interval: 1.040-1.884). The receiver-operating characteristics (ROC) analysis revealed the best cutoff value of a peak CRP concentration >10.7 mg/dl to identify patients with LV thrombus (sensivity 0.93, specificity 0.75, area under ROC curve 0.91).

CONCLUSIONS

The peak CRP concentration is a useful marker of patients with first anterior AMI who are at high risk for LV thrombus.

Clinical, imaging, and pathological characteristics of left ventricular thrombus: a comparison of contrast-enhanced magnetic resonance imaging, transthoracic echocardiography, and transesophageal echocardiography with surgical or pathological validation

BACKGROUND

Left ventricular (LV) thrombus is a frequent and potentially dangerous complication of ischemic heart disease (IHD). We evaluated the clinical, imaging, and pathology characteristics of confirmed LV thrombus and compared the diagnostic value of contrast-enhanced magnetic resonance imaging (MRI) with transthoracic (TTE) and transesophageal echocardiography (TEE) for the diagnosis of LV thrombi.

METHODS

Between November 1997 and December 2003, 361 patients with IHD had surgical and/or pathological confirmation of presence or absence of LV thrombus. Clinical information and preoperative imaging study reports were retrospectively reviewed regarding detection of thrombus. Comparisons were made between clinical and imaging characteristics of patients with and without confirmed thrombus.

RESULTS

Left ventricular thrombus was present in 106 (29%) of 361 patients in this study. Patients with thrombus had a higher incidence of recent embolic events (6.1% vs 0.8%, P < .005). In 160 patients with all 3 imaging modalities performed within 30 days of surgical or pathological confirmation, contrast-enhanced MRI showed the highest sensitivity and specificity (88% +/- 9% and 99% +/- 2%, respectively) compared with TTE (23% +/- 12% and 96% +/- 3.6%, respectively) and TEE (40% +/- 14% and 96% +/- 3.6%, respectively) for thrombus detection.

CONCLUSIONS

Left ventricular thrombus occurs frequently in patients with IHD and is associated with risk of systemic embolization. Contrast-enhanced MRI provided the highest sensitivity and specificity for LV thrombus when compared to TTE and TEE, and should be considered in the care of patients at high risk of LV thrombus formation.

New technologies applied to stress echocardiography: myocardial contrast echocardiography

The development of new echocardiographic contrast agents that can be injected intravenously and can opacify left-sided cardiac chambers has offered a contribution in the field of stress-echocardiography for two main reasons: (1) the improvement of visualization of the endocardial border and thus facilitating recognition of wall motion abnormalities during pharmacological stress or physical exercise; and (2) the obtaining of information on myocardial perfusion during stress examinations. This review will consider: (1) the improvement of diagnostic accuracy during pharmacological stress or physical exercise obtained with the administration of echo-contrast agents; (2) the results of major studies for comparison of the myocardial contrast echocardiography technique versus single-photon emission computed tomography (SPECT) and coronary angiography; (3) the added value for studying perfusion other than wall motion analysis during stress echo; and (4) the advantages and limitations of different stress modalities. New multicenter studies should now definitively clarify the choice of the best contrast agents and create protocols for myocardial contrast echocardiography using different methods of image acquisition in order to unify the diagnostic process before a 'label approved' for perfusion of contrast echocardiographic agents. Finally, caution should be considered when contrast agents are used in the acute phase of myocardial infarction or ischemia.

Improved assessment of left ventricular volumes and ejection fraction by contrast enhanced harmonic color Doppler echocardiography

AIMS

Test the accuracy of contrast enhanced harmonic color Doppler technique (CHCD) to determine left ventricular volumes and ejection fraction (LVEF) compared to equilibrium radionuclide ventriculography (MUGA).

METHODS AND RESULTS

A total of 35 patients were enrolled (male 74.3%) with the mean age of 64.5 +/- 10 years and 6.8 +/- 4.9 days between echo and MUGA scans. The correlation of LVEF by CHCD with MUGA was better (R2 = 0.89) than that of harmonic 2D (H2D) and of contrast enhanced harmonic 2D (CH2D) (R2 = 0.74, R2 = 0.82, respectively). The RMS residual of CHCD (0.056) was smaller than that of H2D and CH2D (0.079, 0.067, respectively). The LVED and LVES volumes by H2D, CH2D and CHCD correlate well with MUGA but there was a significant over estimation of LVED and LVES volumes by H2D and CH2D as compared to MUGA. Also, the RMS residuals were the lowest for the CHCD method. The CHCD had the highest mean inter-observer agreement (90.9%) for LVEF compared with H2D and CH2D (78.9% and 88.1%, respectively).

CONCLUSIONS

CHCD has been feasible in all patients in the present study and it has shown a good concordance with ejection fraction and volumes provided by MUGA.

Prognostic value of contrast stress echocardiography in patients with image quality too limited for traditional noncontrast harmonic echocardiography

Clinical data and contrast stress echocardiography (CSE) results were analyzed in 283 patients to establish the prognostic value of CSE for patients with limited echocardiogram image quality at baseline. The mean follow-up period was 736 +/- 337 days. Only 7 patients (2.5%) had nondiagnostic image quality with contrast enhancement. During follow-up, 24 cardiac events (8.5%) occurred (5 cardiac-related deaths, 2 nonfatal myocardial infarction, 17 coronary revascularizations). Overall sensitivity, specificity, and positive and negative predictive values were 60.9%, 76.8%, 19.7%, and 95.5%, respectively. Kaplan-Meier event-free survival was higher for patients with a negative CSE result as compared with those with a positive CSE finding (P <.0001). In a multivariate Cox proportional hazards model, positive CSE was the strongest predictor of cardiac events (risk ratio 3.7; 95% confidence interval 1.6-8.7). CSE can successfully predict cardiac events for patients with limited noncontrast echocardiographic image quality. A negative CSE result conferred a good prognosis.

Left ventricular opacification at rest and during stress

Although echocardiography is the most widely used cardiac imaging modality in the world, it is often limited by poor endocardial border definition. The development of contrast agents that opacify the cardiac chambers after intravenous injection now makes it possible to acquire high-quality images, even in technically difficult cases. Several studies have now shown that contrast echocardiography improves assessment of global and regional wall motion, enhances observer agreement, and salvages technically difficult studies. In addition, contrast echocardiography is valuable in specific settings, such as the intensive care unit or emergency department, where high-quality images are often most difficult to acquire. Finally, obstacles to the penetration of contrast echocardiography into routine clinical practice (such as cost/reimbursement, logistics, and education) are discussed.

Economic impact of contrast stress echocardiography on the diagnosis and initial treatment of patients with suspected coronary artery disease

OBJECTIVE

To estimate the impact of contrast stress echocardiography on resource use in the treatment of patients with suspected coronary artery disease (CAD).

METHODS

Fifty-nine patients with suspected CAD underwent nuclear perfusion imaging and contrast echocardiography examination. Further treatment was planned after each test and a final treatment was recommended after reviewing the results of both examinations. Medical resources and productivity losses were then collected for a 3-month follow-up period.

RESULTS

Diagnosis was possible in 96.6% of patients with nuclear perfusion imaging and 93.2% with contrast echocardiography, resulting in a cost per successful diagnosis of $637 (Can) and $476 (Can), respectively. For the majority of patients (74%), both tests provided the same result, but for 12 patients nuclear imaging suggested abnormal perfusion, whereas contrast echocardiography indicated normal function and for 2 patients it was the opposite situation. Per-patient costs for the total patient population decreased from $316 (Can) after nuclear perfusion imaging to $250 (Can) when results from both tests were known. Three-month follow-up societal costs were $441 (Can) per patient, with hospitalization contributing 58% of this total cost.

CONCLUSION

Contrast echocardiography has a similar success rate to nuclear perfusion imaging in diagnosing CAD, but has a 28% lower cost and has the potential of additional cost savings through the elimination of further diagnostic tests.

Contrast microbubbles improve diagnostic yield in ICU patients with poor echocardiographic windows

OBJECTIVE

To determine the value of contrast echocardiographic studies in patients admitted to ICUs who have poor echocardiographic windows secondary to COPD, ventilator use, or inability to obtain optimal positioning for the echocardiogram.

DESIGN

A prospective comparison study of technically difficult patients in the ICU.

OUTCOME MEASURE

The total scores for the left ventricle (LV) in the two-chamber and four-chamber views were calculated at baseline and following injection of 1 to 2 mL of a contrast agent. The mean numbers of segments visualized in all patients at baseline and after injection of contrast agent were compared to assess the effect on improved visualization.

RESULTS

Forty consecutive patients underwent echocardiography in the ICU for evaluation of LV function. Of these, 25 patients (63%) had poor visualization of the endocardium and required IV contrast agent. In these 25 patients, the average baseline segmental score was 4.5, compared to 11.6 in patients who received an IV contrast agent. Nineteen patients had an average baseline segmental score of 3.9 and were deemed to have a nondiagnostic study. After administration of IV contrast, all patients converted to a diagnostic study, with an average score of 11.6 segments visualized.

CONCLUSIONS

Use of echocardiographic contrast agents in selected patients with poor baseline echocardiographic windows in the ICU setting significantly enhances segmental LV visualization and yielded 100% conversion from nondiagnostic to diagnostic studies.

Contrast dobutamine stress echocardiography: clinical practice assessment in 300 consecutive patients

In this study we compared non-contrast imaging with contrast imaging of the left ventricle during dobutamine stress echocardiography (DSE). Wall segment visualization, image quality, and confidence of interpretation were determined with and without the use of intravenous Optison, a second-generation echocardiographic contrast agent, in 300 consecutive patients undergoing rest and peak DSE. At rest and at peak stress, the percentage of wall segments visualized, image quality, and confidence of interpretation were better with contrast compared with non-contrast imaging. No significant decrease was seen in wall segment visualization, image quality, or confidence of interpretation from rest to peak stress in images obtained with contrast, unlike the images obtained without contrast from rest to peak stress. The use of the intravenous echocardiographic contrast agent Optison during DSE significantly improved wall segment visualization and image quality at rest and at peak stress, resulting in improved confidence of interpretation.

Use of a decision-analytic model to support the use of a new oral US contrast agent in patients with abdominal pain

RATIONALE AND OBJECTIVES

The authors performed this study to compare the cost and diagnostic abilities of ultrasound (US) performed with and without the use of an oral contrast material recently approved by the U.S. Food and Drug Administration.

MATERIALS AND METHODS

An interactive decision-analytic model was constructed to compare US performed with and without contrast material (SonoRx; Bracco Diagnostics) for the evaluation of patients with abdominal pain who were suspected of having pancreatic disease. The model considered all resources that might be used to evaluate a patient suspected of having pancreatic disease (eg, US, computed tomography [CT], endoscopic retrograde cholangiopancreatography, fine-needle aspiration biopsy, and open biopsy). The literature and an expert panel were the clinical data sources. Cost estimates were based on Medicare and non-Medicare reimbursements. The primary cost-effectiveness measure was the cost to achieve a diagnosis.

RESULTS

SonoRx-enhanced US was less expensive than unenhanced US ($714 vs $808, respectively, with Medicare costs; $1,612 vs $1,878, respectively, with non-Medicare costs) and as effective (0.785 vs 0.782, respectively). SonoRx-enhanced US was more cost-effective than unenhanced US ($909 vs $1,034, respectively, with Medicare costs; $2,052 vs $2,401, respectively, with non-Medicare costs). This relationship was maintained throughout extensive sensitivity analyses.

CONCLUSION

SonoRx-enhanced US is more cost-effective than unenhanced US, primarily because it avoids the need for CT. CT may be avoided owing to the higher probability of obtaining optimal US scans with oral contrast material.

Myocardial contrast echocardiography: clinical benefit and practical issues

Real-time bedside evaluation of myocardial perfusion after intravenous application of microbubbles is the ultimate goal for contrast echocardiography. Over the past decade rapid evolution has occurred in the development of contrast agents, ultrasound equipment tailored to their detection, and image interpretation. This article offers a review of the basic concepts of the technique's background, contrast agent design, and imaging technology. The major clinical indications of myocardial contrast echocardiography are evaluation of acute ischemic syndromes, diagnosis of viable myocardium following AMI, and the detection of CAD using stress contrast perfusion imaging. Furthermore, the article addresses the most significant practical problems and suggested solutions to master those problems. As major new achievements are realistic expectations for the first decade of the twenty-first century, we conclude that the coupling of a new generation of contrast agents with innovative echocardiographic instrumentation will ultimately enable the full potential of myocardial contrast echocardiography to be realized which may revolutionize modern echocardiography.

Myocardial perfusion by contrast echocardiography: diagnosis of coronary artery disease using contrast-enhanced stress echocardiography and assessment of coronary anatomy and flow reserve

The advent of intravenous contrast agents, and newer ultrasound technology to enhance their detection, promises to improve and augment our conventional stress echocardiographic practice by improving diagnostic accuracy and providing novel information regarding myocardial perfusion and functional assessment of the coronary vasculature. The combination of intravenous contrast and harmonic stress echocardiography is a powerful tool for improved wall motion analysis through enhanced image quality, routinely permitting the evaluation of patients with suboptimal images. In this era of cost containment, we await studies in large populations addressing resource utilization and cost-effectiveness to determine if, indeed, all patients presenting with stress echocardiography should receive contrast. Myocardial perfusion can be observed using the technique, but the complex interactions of microbubbles and ultrasound in patients must be understood more fully before its implementation becomes routine practice. Non-invasive imaging of coronary arteries using contrast-enhanced transthoracic harmonic echo/Doppler promises to expand the field of diagnostic and experimental echocardiography, bringing new insight into the pathophysiology of ischemic and non-ischemic heart disease. The continued development of newer contrast agents and refinement of ultrasound imaging equipment ensures that the applications of contrast echocardiography in the assessment of CAD will continue to increase.

Contrast echocardiography: current and future applications

Recent updates in the field of echocardiography have resulted in improvements in image quality, especially in those patients whose ultrasonographic (ultrasound) evaluation was previously suboptimal. Intravenous contrast agents are now available in the United States and Europe for the indication of left ventricular opacification and enhanced endocardial border delineation. The use of contrast enables acquisition of ultrasound images of improved quality. The technique is especially useful in obese patients and those with lung disease. Patients in these categories comprise approximately 10% to 20% of routine echocardiographic examinations. Stress echocardiography examinations can be even more challenging, as the image acquisition time factor is critically important for accurate detection of coronary disease. Improvements in image quality with intravenous contrast agents can facilitate image acquisition and enhance delineation of regional wall motion abnormalities at the peak level of exercise. Recent phase III clinical trial data on the use of Optison and several other agents (currently under evaluation) have revealed that for approximately half of patients, image quality substantively improves, which enables the examination to be salvaged and/or increases diagnostic accuracy. For the "difficult-to-image" patient, this added information results in (1) enhanced laboratory efficiency, (2) a reduction in downstream testing, and (3) possible improvements in patient outcome. In addition, substantial research efforts are underway to use ultrasound contrast agents for assessment of myocardial perfusion. The detection of myocardial perfusion during echocardiographic examinations will permit the simultaneous assessment of global and regional myocardial structure, function, and perfusion-all of the indicators necessary to enable the optimal noninvasive assessment of coronary artery disease. Despite the added benefit in improved efficacy of testing, few data exist regarding the long-term effectiveness of these agents. Currently under evaluation are the clinical and economic outcome implications of intravenous contrast agent use for daily clinical decision making in a variety of patient subsets. Until these data are known, this document offers a preliminary synthesis of available evidence on the value of intravenous contrast agents for use in rest and stress echocardiography. At present, it is the position of this guideline committee that intravenous contrast agents demonstrate substantial value in the difficult-to-image patient with comorbid conditions limiting an ultrasound evaluation of the heart. For such patients, the use of intravenous contrast agents should be encouraged as a means to provide added diagnostic information and to streamline early detection and treatment of underlying cardiac pathophysiology. As with all new technology, this document will require updates and revisions as additional data become available.

Feasibility and accuracy of left ventricular volumes and ejection fraction determination by fundamental, tissue harmonic, and intravenous contrast imaging in difficult-to-image patients

The need to enhance the echocardiographic determination of left ventricular ejection fraction is greatest in patients with suboptimal images. Intravenous contrast (CON) and tissue harmonic imaging (THI) are 2 important methods for enhancing endocardial border definition. However, the comparative feasibility and accuracy of THI and contrast-enhanced power harmonic imaging in difficult-to-image patients have not been examined. We assessed the comparative accuracy of THI and CON in determining EF and ventricular volumes in patients with suboptimal fundamental images. We demonstrated that CON is feasible and exhibits a greater correlation with ejection fraction and ventricular volumes determined by radionuclide angiography (standard of comparison) than THI in this difficult-to-image population, with no reported side effects. For both ejection fraction and ventricular volumes, the observer variability was least for CON, intermediate with THI, and greatest for fundamental imaging.

Improved echocardiographic delineation of left ventricular thrombus with the use of intravenous second-generation contrast image enhancement

Transthoracic echocardiography is the most widely used diagnostic test for left ventricular (LV) thrombus, which must be distinguished from other intraventricular structures and image artifacts. To determine whether second-generation intravenous echocardiographic contrast agents provide better delineation of LV thrombus, we reviewed the results of 2-dimensional echocardiographic studies that were performed in 409 patients over a 1-year period to detect LV thrombus. Studies of 190 (46%) patients were interpreted as nondiagnostic for this purpose, of which 48 patients underwent an additional study after intravenous injection of 0.5 to 2 mL of human albumin microspheres within 1 to 4 days. In 43 (90%) of these 48 patients the contrast-enhanced study was definitive and diagnostic for either the presence or absence of an LV thrombus (P <.0001). Of the initial total of 409 patients, 81 had been studied at the bedside in intensive care units. The bedside studies were nondiagnostic for LV thrombus in 51 (63%) of these 81 patients. Of these 51 patients, 14 underwent additional imaging with contrast enhancement, and the contrast-enhanced images became diagnostic (P =. 004) in 11 (79%) of them. Thus intravenous contrast image enhancement improves the diagnostic yield of echocardiography in patients in whom initial images are nondiagnostic for LV thrombus.