Incremental Benefit of Myocardial Contrast to Combined Dipyridamole-Exercise Stress Echocardiography for the Assessment of Coronary Artery Disease

Low-dose dobutamine stress myocardial contrast echocardiography for the evaluation of myocardial microcirculation and prediction of overall cardiac function recovery

The study aimed to investigate the role of low-dose dobutamine stress myocardial contrast echocardiography (MCE) in evaluating myocardial local microcirculation and predicting cardiac function recovery in patients with myocardial infarction. A total of 50 patients with acute myocardial infarction (AMI) were enrolled in the present study. Positron emission tomography was used as a gold standard to determine viable/non-viable myocardial segments in infarcted myocardial region. MCE and dobutamine stress MCE were carried out 72 h after PCI. MCE was carried out again to evaluate myocardial condition at 6 months after PCI. As compared with normal myocardial segments, resting MCE revealed a significant decrease of the values of A (the peak intensity of the time-perfusion intensity curve, reflecting the myocardial blood volume), β (the slope of the curve, reflecting the myocardial blood flow (MBF) velocity) and A x β (reflecting MBF) of viable and non-viable myocardial segments. After being challenged by dobutamine, the values of A, β and A x β of normal coronary blood supply areas were significantly increased; while the segments A and A x β of viable myocardium were markedly decreased. Patients were further divided into two groups based on the changes in the contrast-enhanced index (CSI) following dobutamine loading. In the dobutamine stress echocardiography-positive group (the CSI increased or decreased by >0.2), the left ventricular ejection fraction was significantly increased and pro-B-type natriuretic peptide significantly decreased at 6 months following intervention. Low-dose dobutamine stress MCE was indicated to be an effective method to evaluate myocardial microcirculation perfusion in patients with AMI following PCI. In addition, CSI, as a simple semi-quantitative index, may predict left ventricular function in patients with AMI.

Three Decades of Ultrasound Contrast Agents: A Review of the Past, Present and Future Improvements

Initial reports from the 1960s describing the observations of ultrasound contrast enhancement by tiny gaseous bubbles during echocardiographic examinations prompted the development of the first ultrasound contrast agent in the 1980s. Current commercial contrast agents for echography, such as Definity, Optison, Sonazoid and SonoVue, have proven to be successful in a variety of on- and off-label clinical indications. Whereas contrast-specific technology has seen dramatic progress after the introduction of the first approved agents in the 1990s, successful clinical translation of new developments has been limited during the same period, while understanding of microbubble physical, chemical and biologic behavior has improved substantially. It is expected that for a successful development of future opportunities, such as ultrasound molecular imaging and therapeutic applications using microbubbles, new creative developments in microbubble engineering and production dedicated to further optimizing microbubble performance are required, and that they cannot rely on bubble technology developed more than 3 decades ago.

Clinical practice of contrast echocardiography: recommendation by the European Association of Cardiovascular Imaging (EACVI) 2017

Contrast echocardiography is widely used in cardiology. It is applied to improve image quality, reader confidence and reproducibility both for assessing left ventricular (LV) structure and function at rest and for assessing global and regional function in stress echocardiography. The use of contrast in echocardiography has now extended beyond cardiac structure and function assessment to evaluation of perfusion both of the myocardium and of the intracardiac structures. Safety of contrast agents have now been addressed in large patient population and these studies clearly established its excellent safety profile. This document, based on clinical trials, randomized and multicentre studies and published clinical experience, has established clear recommendations for the use of contrast in various clinical conditions with evidence-based protocols.

Contrast-Enhanced Stress Echocardiography and Myocardial Perfusion Imaging in Patients Hospitalized With Chest Pain: A Randomized Study

Ultrasound contrast-enhanced stress echocardiography improves endocardial visualization, but diagnostic test rates versus stress myocardial perfusion imaging (MPI) have not been studied. A prospective randomized trial was performed between April 2012 and October 2014 at a single-center, safety net hospital. Hospitalized patients referred for noninvasive stress imaging were randomized 1:1 to stress echocardiography or stress MPI. The primary outcome was diagnostic test rate defined as interpretable images and achievement of >85% of age-predicted maximal heart rate (for dobutamine and exercise). Rates were assessed among those completing testing and then based solely on image interpretability. Charges and length of stay were secondary outcomes. A total of 240 patients were randomized, and 229 completed testing. Diagnostic test rates were similar for stress echocardiography versus MPI {89.4% [95% confidence interval (CI), 82.2-94.4] vs. 94.8% [95% CI, 89.1-98.1], P = 0.13} and did not differ with multivariable adjustment. Modalities requiring a diagnostic heart rate criteria were more frequently ordered with stress echocardiography (100% vs. 26%; P < 0.001). Therefore, an imaging-based analysis without the 12 individuals who failed to achieve target heart rate (n = 217) was evaluated with diagnostic test rates of 100% versus 94.8% (95% CI, 89.1%-98.1%; P = 0.03) for stress echocardiography and MPI, respectively. Median length of stay did not differ. Median (interquartile range) test-related charges were lower with stress echocardiography: $2,424 ($2400-$2508) versus $3619 ($3584-$3728), P < 0.0001. Overall, tests were positive for ischemia in 8% of patients. In conclusion, contrast-enhanced stress echocardiography provides comparable diagnostic test rates to MPI with lower associated charges.

A novel method for quantitative myocardial contrast echocardiography in mice

The small size of the mouse heart frequently imparts technical challenges when applying conventional in vivo imaging methods for assessing heart function. Here, we describe the use of high-frequency ultrasound imaging in conjunction with a size-tuned blood pool contrast agent for quantitatively assessing myocardial perfusion in living mice. A perflurocarbon microbubble formulation exhibiting a narrow size distribution was developed, and echogenicity was assessed at 18 MHz in vitro. Adult mice were subjected to permanent ligation of the left anterior descending artery. Ultrasound imaging was performed on day 7, and a cohort of intact mice was used as a control. Parasternal long-axis cine clips were acquired at 18 MHz before and after contrast administration. Reduced ejection fraction and increased end-systolic volume were observed in infarcted compared with control mice. In control animals, washin of the contrast agent was visible in all myocardial segments. Reduced contrast enhancement was observed in apical-posterolateral regions of all infarcted mice. A novel method for reslicing of the imaging data through the time domain provided a two-dimensional presentation of regional contrast agent washin, enabling convenient identification of locations exhibiting altered perfusion. Myocardial segments exhibiting diminished contractility were observed to have correspondingly low relative myocardial perfusion. The contrast agent formulation and methods demonstrated here provide the basis for simplifying routine in vivo estimation of infarct size in mice and may be particularly useful in longitudinal evaluation of revascularization interventions and assessment of peri-infarct ischemia. NEW & NOTEWORTHY Murine myocardial contrast echocardiography frequently suffers from poor sensitivity to contrast. Here, we formulated a novel size-tuned microbubble contrast agent and validated it for use with ultra-high-frequency ultrasound. A novel data method for evaluating myocardial perfusion based on reslicing the imaging data through the time domain is presented.

Principles of transthoracic echocardiographic evaluation

Transthoracic echocardiography is the most widely used imaging test in cardiology. Although completely noninvasive, transthoracic echocardiography has a well-established role in the diagnosis of numerous cardiovascular diseases, and also provides critical qualitative and quantitative information on their prognosis and pathophysiological processes. The aim of this Review is to outline the broad principles of transthoracic echocardiography, including the traditional techniques of two-dimensional, colour, and spectral Doppler echocardiography, and newly developed advances including tissue Doppler, myocardial deformation imaging, torsion, stress echocardiography, contrast and three-dimensional echocardiography. The advantages and disadvantages, clinical application, prognostic value, and salient research findings of each modality are described. Advances in complex imaging techniques are expected to continue unabated, and this Review highlights technical improvements that will influence the diagnosis and improve our understanding of cardiovascular function and disease.

Imagify™ (perflubutane polymer microspheres) injectable suspension for the assessment of coronary artery disease

Myocardial contrast echocardiography is a rapidly evolving technique for the assessment of myocardial perfusion. Many studies have indicated their ability to detect flow-limiting coronary artery disease. Imagify (perflubutane polymer microspheres) injectable suspension, also known as AI-700, is a new ultrasound contrast agent that satisfies all the characteristics of an ideal agent for the assessment of myocardial perfusion. Preliminary studies with Imagify indicate that it is comparable with radionuclide perfusion techniques (presently the most widely used imaging technique to assess coronary artery disease) without the disadvantages of radiation and lack of availability at the bedside. This article provides an overview of Imagify, a new ultrasound contrast agent.

Use of contrast echocardiography in intensive care and at the emergency room

Bedside echocardiography in emergency room (ER) or in intensive care unit (ICU) is an important tool for managing critically ill patients, to obtain a timely accurate diagnosis and to immediately stratify the risk to the patient’s life. It may also render invasive monitoring unnecessary. In these patients, contrast echocardiography may improve quality of imaging and also may provide additional information, especially regarding myocardial perfusion in those with suspected coronary artery disease. This article focuses on the principle of contrast echocardiography and the clinical information that can be obtained according to the most frequent presentations in ER and ICU.

Echocardiography: frontier imaging in cardiology

This article reviews the recent developments in echocardiography that have maintained this technology at the forefront of day-to-day imaging in clinical cardiology. The primary reason for most requests for imaging in cardiovascular medicine is to assess left ventricular structure and function. As our understanding of left ventricular mechanics has become more intricate, tissue Doppler and speckle tracking modalities have been developed that deliver greater insights into diagnosis of cardiomyopathy and earlier warning of ventricular dysfunction. Increased accuracy has been achieved with the dissemination of real-time three-dimensional echocardiography, which has also acquired a central role in the pre-operative assessment of patients prior to reparative valvular surgery. The use of contrast has broadened the indications for transthoracic echocardiography and has increased the accuracy of stress echocardiography, while reducing the number of patients who cannot be scanned because of a limited acoustic window. Finally, echocardiography will be seen in the future not only as a diagnostic tool in those affected by cardiovascular disease but also as a method for prediction of risk and perhaps activation of targeted treatment.

Prognostic value of real time dobutamine stress myocardial contrast echocardiography in patients with chest pain syndrome

The aims of this study were (1) to evaluate the prognostic value of negative wall motion (WM) and myocardial perfusion during contrast-dobutamine stress echocardiography (DSE), (2) to determine whether WM-myocardial contrast echocardiography (MCE) had incremental prognostic value over just WM during DSE in patients with chest pain in the emergency room (ER), and (3) to compare the prognostic value of negative DSE-WM, and DSE-WM-MCE to nuclear-myocardial perfusion imaging (N-MPI) in a similar patient population over the same time period. We retrospectively studied 569 patients with real time contrast DSE, and 147 patients underwent N-MPI for evaluation of chest pain. Follow-up for cardiac events was obtained between 12 and 25 months. The cumulative cardiac event-free survival was 94.5% in negative DSE-WM, 97.1% in negative DSE-WM-MCE and 96.7% in negative N-MPI group. Cardiac event-free survival of the negative DSE-WM-MCE group was significantly higher than the DSE-WM group (log rank P < 0.01), and similar in the DSE-WM-MCE group compared to the N-MPI group. Combined WM and perfusion during DSE was the strongest independent predictor for cardiac events. The negative predictive power of DSE-WM-MCE is superior to that of just negative DSE-WM and is comparable to that of N-MPI. Myocardial perfusion and WM analysis during DSE provide independent information for predicting cardiac events in patients with chest pain syndrome in the ER.

Imaging techniques in coronary atherosclerotic disease: dobutamine stress echocardiography--evidence and perspectives

Dobutamine stress echocardiography is the most widely disseminated noninvasive technique for the assessment of coronary artery disease. Its results are important for clinical decisions. It is a versatile technique with high sensitivity and specificity for detecting viable myocardium at jeopardy. More recently, strain rate imaging has been applied to stress echocardiography. This approach relies on tissue Doppler or two-dimensional strain imaging to quantify myocardial deformation. The application of contrast echocardiographic techniques to stress echocardiography enables left ventricular opacification for border enhancement and myocardial perfusion imaging. Thus, this application is not limited to stress echocardiography, but has utility whenever image quality adversely affects wall motion assessment. Recently, three-dimensional stress echocardiography imaging has been proposed as an alternative approach to assess myocardial ischemia.

Contrast stress-echocardiography predicts cardiac events in patients with suspected acute coronary syndrome but nondiagnostic electrocardiogram and normal 12-hour troponin

BACKGROUND

No large study has demonstrated that any stress test can risk-stratify future hard cardiac events (cardiac death or myocardial infarction) in patients with suspected acute coronary syndromes (ACS), nondiagnostic electrocardiographic (ECG) findings, and normal troponin levels. The aim of this study was to test the hypothesis that combined contrast wall motion and myocardial perfusion echocardiographic assessment (cMCE) during stress echocardiography can predict long-term hard cardiac events in patients with suspected ACS, nondiagnostic ECG findings, and normal troponin.

METHODS

A total of 545 patients referred for contrast stress echocardiography from the emergency department for suspected ACS but nondiagnostic ECG findings and normal troponin levels at 12 hours were followed up for cardiac events. Patients underwent dipyridamole-atropine echocardiography with adjunctive myocardial perfusion imaging using a commercially available ultrasound contrast medium (SonoVue).

RESULTS

During a median follow-up period of 12 months, 25 cardiac events (4.6%) occurred (no deaths, 12 nonfatal myocardial infarctions, 13 episodes of unstable angina). Abnormal findings on cMCE were the most significant predictor of both hard cardiac events (hazard ratio, 22.8; 95% confidence interval, 2.9-176.7) and the combined (cardiac death, myocardial infarction, or unstable angina requiring revascularization) end point (hazard ratio, 10.7; 95% confidence interval, 3.7-31.3). The inclusion of the cMCE variable significantly improved multivariate models, determining lower Akaike information criterion values and higher discrimination ability.

CONCLUSIONS

cMCE during contrast stress echocardiography provided independent information for predicting hard and combined cardiac events beyond that predicted by stress wall motion abnormalities in patients with suspected ACS, nondiagnostic ECG findings, and normal troponin levels.

Influence of left ventricular hypertrophy and geometry on diagnostic accuracy of wall motion and perfusion magnetic resonance during dobutamine stress

BACKGROUND

The purpose of this study was to determine the influence of left ventricular (LV) hypertrophy and geometry on the diagnostic accuracy of wall motion and additional perfusion imaging during high-dose dobutamine/atropine stress magnetic resonance for the detection of coronary artery disease.

METHODS AND RESULTS

Combined dobutamine stress magnetic resonance (DSMR)-wall motion and DSMR-perfusion imaging was performed in a single session in 187 patients scheduled for invasive coronary angiography. Patients were classified into 4 categories on the basis of LV mass (normal, ≤ 81 g/m(2) in men and ≤ 62 g/m(2) in women) and relative wall thickness (RWT) (normal, <0.45) as follows: normal geometry (normal mass, normal RWT), concentric remodeling (normal mass, increased RWT), concentric hypertrophy (increased mass, increased RWT), and eccentric hypertrophy (increased mass, normal RWT). Wall motion and perfusion images were interpreted sequentially, with observers blinded to other data. Significant coronary artery disease was defined as ≥ 70% stenosis. In patients with increased LV concentricity (defined by an RWT ≥ 0.45), sensitivity and accuracy of DSMR-wall motion were significantly reduced (63% and 73%, respectively; P<0.05) compared with patients without increased LV concentricity (90% and 88%, respectively; P<0.05). Although accuracy of DSMR-perfusion was higher than that of DSMR-wall motion in patients with concentric hypertrophy (82% versus 71%; P < 0.05), accuracy of DSMR-wall motion was superior to DSMR-perfusion (90% versus 85%; P < 0.05) in patients with eccentric hypertrophy.

CONCLUSIONS

The accuracy of DSMR-wall motion is influenced by LV geometry. In patients with concentric remodeling and concentric hypertrophy, additional first-pass perfusion imaging during high-dose dobutamine stress improves the diagnostic accuracy for the detection of coronary artery disease.

Incremental value of contrast myocardial perfusion to detect intermediate versus severe coronary artery stenosis during stress-echocardiography

Background

We aimed to compare the incremental value of contrast myocardial perfusion imaging (MPI) for the detection of intermediate versus severe coronary artery stenosis during dipyridamole-atropine echocardiography (DASE).

Wall motion (WM) assessment during stress-echocardiography demonstrates suboptimal sensitivity to detect coronary artery disease (CAD), particularly in patients with isolated intermediate (50%-70%) coronary stenosis.

Methods

We performed DASE with MPI in 150 patients with a suspected chest pain syndrome who were given clinical indication to coronary angiography.

Results and discussion

When CAD was defined as the presence of a ≥50% stenosis, the addition of MPI increased sensitivity (+30%) and decreased specificity (-14%), with a final increase in total diagnostic accuracy (+16%, p < 0.001). The addition of MPI data substantially increased the sensitivity to detect patients with isolated intermediate stenosis from 37% to 98% (p < 0.001); the incremental sensitivity was much lower in patients with severe stenosis, from 85% to 96% (p < 0.05), at the expense of a higher decrease in specificity and a final decrease in total diagnostic accuracy (-18%, p < 0.001).

Conclusions

The addition of MPI on top of WM analysis during DASE increases the diagnostic sensitivity to detect obstructive CAD, whatever its definition (≥50% or > 70% stenosis), but it is mainly driven by the sensitivity increase in the intermediate group (50%-70% stenosis).

The total diagnostic accuracy increased only when defining CAD as ≥50% stenosis, since in patients with severe stenosis (> 70%) the decrease in specificity is not counterbalanced by the minor sensitivity increase.

Myocardial perfusion imaging with contrast ultrasound

This report reviews the development and clinical application of myocardial perfusion imaging with myocardial contrast echocardiography (MCE). This includes the development of microbubble formulations that permit the detection of left ventricular contrast from venous injection and the imaging techniques that have been invented to detect the transit of these microbubbles through the microcirculation. The methods used to quantify myocardial perfusion during a continuous infusion of microbubbles are described. A review of the clinical studies that have examined the clinical utility of myocardial perfusion imaging with MCE during rest and stress echocardiography is then presented. The limitations of MCE are also discussed.

Impact of previous myocardial infarction on the incremental value of myocardial contrast to two-dimensional supine bicycle stress echocardiography in evaluation of coronary artery disease

BACKGROUND

If compared to two-dimensional echocardiography (2DE), myocardial contrast echocardiography (MCE) improves detection of coronary artery disease (CAD) during pharmacological stress, but data on MCE vs. 2DE during supine bicycle stress is limited. Although previous myocardial infarction (MI) influences sensitivity of 2DE, its effect on MCE has not been evaluated.

OBJECTIVES

The study sought to determine the incremental benefit of MCE over 2DE for evaluation of CAD during supine bicycle stress and to assess the impact of previous MI on diagnostic values of both methods.

METHODS

We studied 103 consecutive patients scheduled for coronary angiography. Prior to coronary angiography, all patients underwent supine bicycle stress. 2DE and MCE were performed during this stress test. The diagnosis of obstructive CAD (> or =50% stenosis) was based on the presence of inducible wall motion and perfusion abnormalities.

RESULTS

Quantitative coronary angiography revealed > or =50% stenosis in 53 of 77 patients without previous MI and in 21 of 26 patients with previous MI. If compared to 2DE, MCE was more sensitive (68% vs. 86%; p<0.001) and more accurate (73% vs. 86%; p < 0.001) to detect > or =50% stenosis. In patients without previous MI, 2DE and MCE yielded sensitivity of 65% and 85% (p < 0.01) and accuracy of 71% and 85% (p < 0.01), whereas in patients with previous MI sensitivity was 79% and 90% (p=NS) and accuracy 79% and 88% (p = NS), respectively.

CONCLUSIONS

MCE enhances sensitivity and accuracy of 2DE in detection of obstructive CAD during supine bicycle stress. The incremental benefit of MCE is especially present in patients without previous MI.

Limitations and potential clinical application on contrast echocardiography

Myocardial contrast echocardiography (MCE) is a relatively simple myocardial perfusion imaging technique which should be used in different clinical settings. The ability of MCE to provide a comprehensive assessment of cardiac structure, function, and perfusion is likely to make it the technique of choice for non-invasive cardiac imaging.Contrast agents are encapsulated microbubbles (MB) filled with either air or high-molecular-weight gas. They are innocuous, biologically inert and when administered intravasculary, the sound backscatter from the blood poll is enhanced because MB have the enormous reflective ability due to a large acoustic impedance mismatch between the bubble gas and surrounding blood.MCE is an ideal imaging tool for the assessment of left heart contrast and the myocardial microcirculation. MCE detects contrast MB at the capillary level within the myocardium and, thus, has the potential to assess tissue viability and the duration of the contrast effect. MCE was equivalent to SPECT for the detection of CAD with a tendency toward higher sensitivity of MCE compared with SPECT in microvascular disease and CAD. MCE is also a bedside technique that can be used early in patients presenting with acute heart failure to rapidly assess LV function (regional and global) and perfusion (rest and stress).

Validation of magnetic resonance myocardial perfusion imaging with fractional flow reserve for the detection of significant coronary heart disease

BACKGROUND

Magnetic resonance myocardial perfusion imaging (MRMPI) has a number of advantages over the other noninvasive tests used to detect reversible myocardial ischemia. The majority of previous studies have generally used quantitative coronary angiography as the gold standard to assess the accuracy of MRMPI; however, only an approximate relationship exists between stenosis severity and functional significance. Pressure wire-derived fractional flow reserve (FFR) values <0.75 correlate closely with objective evidence of reversible ischemia. Accordingly, we have compared MRMPI with FFR.

METHODS AND RESULTS

One hundred three patients referred for investigation of suspected angina underwent MRMPI with a 1.5-T scanner. The stress agent was intravenous adenosine (140 microg . kg(-1) . min(-1)), and the first-pass bolus contained 0.1 mmol/kg gadolinium. In the following week, coronary angiography with pressure wire studies was performed. FFR was recorded in all patent major epicardial coronary arteries, with a value <0.75 denoting significant stenosis. MRMPI scans, analyzed by 2 blinded observers, identified perfusion defects in 121 of 300 coronary artery segments (40%), of which 110 had an FFR <0.75. We also found that 168 of 179 normally perfused segments had an FFR > or = 0.75. The sensitivity and specificity of MRMPI for the detection of functionally significant coronary heart disease were 91% and 94%, respectively, with positive and negative predictive values of 91% and 94%.

CONCLUSIONS

MRMPI can detect functionally significant coronary heart disease with excellent sensitivity, specificity, and positive and negative predictive values compared with FFR.

Prognostic value of dipyridamole stress myocardial contrast echocardiography: comparison with single photon emission computed tomography

BACKGROUND

Dipyridamole stress myocardial contrast echocardiography (MCE) can be used to detect coronary artery disease (CAD). Because it measures myocardial blood flow velocity in addition to measuring myocardial blood volume, it was hypothesized that it should have greater prognostic utility than single photon-emission computed tomography (SPECT), which measures only myocardial blood volume. Because blood flow mismatch precedes wall thickening (WT) abnormalities during demand ischemia, it was also postulated that perfusion on MCE would be superior to WT abnormalities on echocardiography for this purpose.

METHODS

The incidence of nonfatal myocardial infarction and cardiac death was determined in 261 patients with known or suspected CAD over a mean follow-up period of 14 months who underwent simultaneous dipyridamole stress MCE and 99mTc-sestamibi SPECT. Comparisons of survival curves were conducted with stratified (and unstratified) log-rank tests.

RESULTS

Abnormal results on MCE were found to be the best predictor of an adverse outcome (odds ratio, 23; 95% confidence interval, 6-201; P<.0001) and provided incremental prognostic value over clinical variables (age>60 years, the presence of >or=3 cardiac risk factors, known peripheral vascular disease, prior myocardial infarction, and left ventricular systolic function), inducible WT abnormalities, and SPECT. Prognoses were worst in patients who had both abnormal results on MCE and inducible WT abnormalities and best in those who had neither. Patients with abnormal results on MCE but no inducible WT abnormalities had intermediate outcomes.

CONCLUSION

In patients with known or suspected CAD undergoing dipyridamole stress, MCE provides powerful prognostic information that is superior to clinical variables, electrocardiography, left ventricular systolic function, WT analysis, and SPECT. MCE may therefore serve as a method of choice for myocardial perfusion assessment in patients with known or suspected CAD. Larger studies are needed to confirm these findings.

Contrast echocardiography: an update

Despite the advent of tissue harmonic imaging, echocardiography fails to produce diagnostically useful images in a significant proportion of patients. This often leads to inaccurate assessment of left ventricular function, necessitating the use of other, more expensive and laborious imaging techniques, purely for diagnostic purposes. This has facilitated the development of microbubbles, which together with ultrasound, produce opacification of the left ventricular cavity, thus enabling clear visualization and accurate quantification of left ventricular function. Contrast agents have also facilitated the development of myocardial contrast echocardiography. This allows assessment of cardiac anatomy, function, and perfusion, all in one sitting, by the bedside. Contrast ultrasound imaging also has now been applied to newer techniques (eg, real-time three-dimensional echocardiography) and is also showing promise in other cardiovascular scans (eg, carotid ultrasound for intima-media thickness). Thus, contrast agents play a pivotal role in noninvasive cardiovascular imaging and its use worldwide is likely to increase.

Detection of single-vessel coronary artery disease by dipyridamole stress echocardiography: no longer a problem?

We aimed to evaluate whether addition of myocardial contrast echocardiography (MCE) perfusion data improves the sensitivity of stress echocardiography for detection of single-vessel coronary artery disease (svCAD) and to compare the diagnostic value of MCE and single-photon emission computed tomography (SPECT) for detection of svCAD.

METHODS

One hundred and three patients with suspected or known stable CAD underwent dipyridamole (0.84 mg kg(-1) intravenously over 4 min)-atropine (up to 1 mg intravenously) stress echocardiography combined with MCE. Wall motion abnormalities (WMA) and perfusion defects were assessed visually. Presence of CAD was detected by coronary angiography.

RESULTS

Single-vessel coronary artery disease defined as >or=70% stenosis was detected in 30% of patients, whereas 26% of patients had svCAD defined as >or=50% stenosis. Presence of inducible WMA had 35% and 26% sensitivity for detection of svCAD defined as >or=70% and >or=50% stenosis, respectively. Concomitant evaluation of MCE increased the sensitivity to 74% (P = 0.005) and 56% (P = 0.053), respectively, using any inducible abnormality (WMA or perfusion defects) as a criterion. Presence of any (inducible or fixed) WMA had 77% and 59% sensitivity for detection of svCAD defined as >or=70% and >or=50% stenosis, respectively. In case of such criterion for stress test positivity, the improvement in sensitivity provided by addition of MCE (to 94% and 78%, respectively) did not reach statistical significance.

CONCLUSIONS

Addition of MCE perfusion analysis during stress echocardiographical examination based on evaluation of inducible abnormalities improves the test sensitivity for detection of svCAD. This benefit is less apparent when fixed WMA and perfusion defects are incorporated into the stress test positivity criterion.

American Society of Echocardiography Consensus Statement on the Clinical Applications of Ultrasonic Contrast Agents in Echocardiography

ACCREDITATION STATEMENT: The American Society of Echocardiography (ASE) is accredited by the Accreditation Council for Continuing Medical Education to provide continuing medical education for physicians. The ASE designates this educational activity for a maximum of 1 AMA PRA Category 1 Credit.trade mark Physicians should only claim credit commensurate with the extent of their participation in the activity. The American Registry of Diagnostic Medical Sonographers and Cardiovascular Credentialing International recognize the ASE's certificates and have agreed to honor the credit hours toward their registry requirements for sonographers. The ASE is committed to resolving all conflict-of-interest issues, and its mandate is to retain only those speakers with financial interests that can be reconciled with the goals and educational integrity of the educational program. Disclosure of faculty and commercial support sponsor relationships, if any, have been indicated.

TARGET AUDIENCE

This activity is designed for all cardiovascular physicians, cardiac sonographers, and nurses with a primary interest and knowledge base in the field of echocardiography; in addition, residents, researchers, clinicians, sonographers, and other medical professionals having a specific interest in contrast echocardiography may be included.

OBJECTIVES

Upon completing this activity, participants will be able to: 1. Demonstrate an increased knowledge of the applications for contrast echocardiography and their impact on cardiac diagnosis. 2. Differentiate the available ultrasound contrast agents and ultrasound equipment imaging features to optimize their use. 3. Recognize the indications, benefits, and safety of ultrasound contrast agents, acknowledging the recent labeling changes by the US Food and Drug Administration (FDA) regarding contrast agent use and safety information. 4. Identify specific patient populations that represent potential candidates for the use of contrast agents, to enable cost-effective clinical diagnosis. 5. Incorporate effective teamwork strategies for the implementation of contrast agents in the echocardiography laboratory and establish guidelines for contrast use. 6. Use contrast enhancement for endocardial border delineation and left ventricular opacification in rest and stress echocardiography and unique patient care environments in which echocardiographic image acquisition is frequently challenging, including intensive care units (ICUs) and emergency departments. 7. Effectively use contrast echocardiography for the diagnosis of intracardiac and extracardiac abnormalities, including the identification of complications of acute myocardial infarction. 8. Assess the common pitfalls in contrast imaging and use stepwise, guideline-based contrast equipment setup and contrast agent administration techniques to optimize image acquisition.

Evaluation and Optimization of Real-Time Perfusion Imaging Using Multiple Ultrasound Systems With Imagify Microspheres

Current commercially available ultrasound systems have proprietary contrast-specific imaging modes to evaluate myocardial contrast enhancement (MCE). Each of these modes uses a different pulsing scheme and has unique system terminology and a proprietary name. The aim of this study was to determine optimal system settings and MCE duration using Imagify (perflubutane polymer microspheres), a new ultrasound imaging agent undergoing development for perfusion stress echocardiography to detect coronary artery disease. Thirty-nine patients were enrolled. Four ultrasound systems with real-time, low mechanical index (nonlinear, multi-pulse) modes were evaluated. Optimal MCE settings were determined qualitatively in the apical views through systematic adjustment of multiple settings while maintaining a frame rate consistent with stress echocardiography to produce high-intensity (bright-hyperechoic), transmural myocardial enhancement. When using the clinical dose of Imagify during real-time imaging, the optimized settings for three ultrasound systems allowed prolonged, clinically useful MCE with a mean duration of 9.5 minutes.

Accelerated stress real-time myocardial contrast echocardiography for the detection of coronary artery disease: comparison with 99mTc single photon emission computed tomography

OBJECTIVE

The aims of this prospective study were to compare the diagnostic value of accelerated vasodilator stress real-time myocardial contrast echocardiography (MCE) and single photon emission computed tomography (SPECT) against coronary angiography and to evaluate whether the addition of MCE perfusion data improves the diagnostic accuracy of stress echocardiography.

METHODS

A total of 103 patients with suspected or known stable coronary artery disease (CAD) underwent SPECT and accelerated high-dose dipyridamole (0.84 mg/kg intravenously for 4 minutes) atropine (up to 1 mg intravenously) stress real-time qualitative MCE. The presence of CAD was detected by coronary angiography.

RESULTS

CAD defined as >or= 70% stenosis was detected in 77% of patients, whereas 86% of patients had CAD defined as >or= 50% stenosis. In a territory-by-territory analysis, the concordance between MCE and SPECT in detecting perfusion defects varied from 72.8% (kappa = 0.386) to 89.3% (kappa = 0.642). There were no significant differences between MCE and SPECT in sensitivity, specificity, and diagnostic accuracy for identifying patients with CAD. Combining MCE and wall motion abnormality analysis significantly improved the sensitivity of the test compared with wall motion abnormality analysis alone.

CONCLUSIONS

Accelerated vasodilator stress real-time MCE yields a good concordance with SPECT in detection of perfusion defects and a similar diagnostic value for the detection of CAD. The addition of MCE perfusion data improves the diagnostic value of stress echocardiography.

Left ventricular opacification for the diagnosis of coronary artery disease with stress echocardiography: an angiographic study of incremental benefit and cost-effectiveness

BACKGROUND

Left ventricular opacification (LVO) improves image quality at stress echocardiography (SE). We examined whether routine use of LVO adds incremental benefit and is cost-effective for diagnosis of coronary artery disease (CAD).

METHODS

Contrast pharmacologic and/or exercise SE was performed in 135 patients (81 men; 56 +/- 10 years) undergoing coronary angiography. Observers sequentially interpreted first standard, then LVO images; a positive SE was defined by resting or inducible wall motion abnormality in > or = 2 segments. Coronary artery disease (75 patients, 119 territories) was defined as > 50% stenosis. Three cost-effectiveness models were studied, and a sensitivity analysis was performed.

RESULTS

Left ventricular opacification increased the sensitivity of SE (80%-91%; P = .03), including single-vessel CAD (65%-87%; P = .04), with no significant change in specificity (72%-77%; P = NS). Left ventricular opacification was of benefit to 14% of patients, unrelated to resting image quality. Use of LVO in all patients added 59% to the cost of the procedure (P < .001), at a cost of $1069 per additional correct diagnosis. In a cost-effectiveness model based on cardiac outcomes after SE, LVO resulted in an increase in total cost of $1069. A 3.7% improvement in sensitivity resulted in a negative cost to identify CAD, but even 15% to 20% improvements in specificity failed to balance the cost of contrast for exclusion of CAD.

CONCLUSIONS

Left ventricular opacification adds significant incremental diagnostic benefit to standard SE, especially single-vessel CAD. Despite improved sensitivity, the use of contrast in all patients was not cost-effective when analyzed with a model based on previously published patient outcomes.

Real Time Myocardial Contrast Echocardiography During Supine Bicycle Stress and Continuous Infusion of Contrast Agent. Cutoff Values for Myocardial Contrast Replenishment Discriminating Abnormal Myocardial Perfusion

BACKGROUND

Myocardial contrast echocardiography (MCE) is a new imaging modality for diagnosing coronary artery disease (CAD).

OBJECTIVE

The aim of our study was to evaluate feasibility of qualitative myocardial contrast replenishment (RP) assessment during supine bicycle stress MCE and find out cutoff values for such analysis, which could allow accurate detection of CAD.

METHODS

Forty-four consecutive patients, scheduled for coronary angiography (CA) underwent supine bicycle stress two-dimensional echocardiography (2DE). During the same session, MCE was performed at peak stress and post stress. Ultrasound contrast agent (SonoVue) was administered in continuous mode using an infusion pump (BR-INF 100, Bracco Research). Seventeen-segment model of left ventricle was used in analysis. MCE was assessed off-line in terms of myocardial contrast opacification and RP. RP was evaluated on the basis of the number of cardiac cycles required to refill the segment with contrast after its prior destruction with high-power frames. Determination of cutoff values for RP assessment was performed by means of reference intervals and receiver operating characteristic analysis. Quantitative CA was carried out using CAAS system.

RESULTS

MCE could be assessed in 42 patients. CA revealed CAD in 25 patients. Calculated cutoff values for RP-analysis (peak-stress RP >3 cardiac cycles and difference between peak stress and post stress RP >0 cardiac cycles) provided sensitive (88%) and accurate (88%) detection of CAD. Sensitivity and accuracy of 2DE were 76% and 79%, respectively.

CONCLUSIONS

Qualitative RP-analysis based on the number of cardiac cycles required to refill myocardium with contrast is feasible during supine bicycle stress MCE and enables accurate detection of CAD.

Automated Analysis of Myocardial Deformation at Dobutamine Stress Echocardiography

OBJECTIVES

We investigated the accuracy of automated analysis of myocardial deformation during dobutamine stress echocardiography (DSE).

BACKGROUND

The time required for segmental measurement of strain rate imaging (SRI) limits its feasibility for quantification of DSE.

METHODS

Myocardial deformation was assessed at DSE in 197 patients, 76 with and 61 without coronary artery disease (CAD) at angiography, and 60 at low risk of CAD. Automated deformation analysis was based on velocity gradient and segment length methods of measuring longitudinal motion within a region of interest tracked through the cardiac cycle. Results were compared with independent wall motion scoring (WMS). Patients were randomly divided; group A (n = 69) established optimal cutoffs for the parameters and group B (n = 68) tested their accuracy.

RESULTS

The feasibility of WMS exceeded that of both SRI methods at rest and at peak stress. In group A, the area under the receiver-operating characteristics curve of the peak systolic strain rate was 0.90 by both methods, and the optimal cutoffs for detection of CAD were -1.3 (velocity gradient) and -1.2 s(-1) (segment length). The areas under the receiver-operating characteristics curves for end-systolic strain were less (0.87) by both methods, with respective cutoffs of 9% and 8%. In group B, the velocity and segment length methods had respective sensitivities of 87% and 84% for SR, and 87% and 88% for end-systolic strain. Both significantly exceeded that of WMS in the same group (75%).

CONCLUSIONS

Automated analysis of myocardial deformation at DSE is feasible and accurate, and may increase the sensitivity of expert conventional reading.

Myocardial Contrast Echocardiography Evolving as a Clinically Feasible Technique for Accurate, Rapid, and Safe Assessment of Myocardial Perfusion

Intravenous myocardial contrast echocardiography (MCE) is a recently developed technique for assessment of myocardial perfusion. Up to now, many studies have demonstrated that the sensitivity and specificity of qualitative assessment of myocardial perfusion by MCE in patients with acute and chronic ischemic heart disease are comparable with other techniques such as cardiac scintigraphy and dobutamine stress echocardiography. Furthermore, quantitative parameters of myocardial perfusion derived from MCE correlate well with the current clinical standard for this purpose, positron emission tomography. Myocardial contrast echocardiography provides a promising and valuable tool for assessment of myocardial perfusion. Although MCE has been primarily performed for medical research, its implementation in routine clinical care is evolving. This article is intended to give an overview of the current status of MCE.

Coronary Artery Disease

Early and accurate diagnostic testing is a critical factor in the detection and optimal management of coronary artery disease (CAD); thus, noninvasive cardiac imaging has become a central tool for CAD evaluation. Currently, tests used for evaluating CAD include conventional resting and stress electrocardiogram, echocardiography, and myocardial perfusion imaging--the most widely used imaging test for evaluation of suspected myocardial ischemia. Emerging techniques for noninvasive assessment of myocardial perfusion and coronary angiography include cardiac computed tomography, cardiac magnetic resonance imaging, and positron emission tomography. The distinctive pathophysiology of atherosclerosis can be used together with imaging techniques to diagnose and assess risk for CAD. Imaging modalities for cardiac risk stratification include a diverse array of tools, such as noninvasive tests that visualize presymptomatic atherosclerosis to sophisticated radionuclide protocols that identify myocardial viability. Of the noninvasive imaging tests, gated SPECT is the most accurate method for risk stratification of CAD. Myocardial perfusion imaging with SPECT has improved accuracy and image quality such that a shift from diagnostic to prognostic use has occurred. Radionuclide myocardial perfusion imaging has played an important role in CAD evaluation since the introduction of thallium-201 (Tl-201) in the 1970s. Although Tl-201 has high sensitivity, specificity, and reproducibility, it also has physical properties that limit its use and affect image quality. Currently, Tc-99m tetrofosmin and sestamibi are the most commonly used agents for a variety of resting and stress protocols, both have similar diagnostic accuracy profiles. The field of nuclear cardiology has grown steadily over the past few decades, as more practitioners recognize its clinical applications and value in managing cardiovascular disease. There is abroad spectrum of noninvasive and invasive testing available for the diagnosis and management of patients with cardiovascular disease. Advances in computer technology have made sophisticated devices, such as the gated SPECT, a routine part of cardiology.

Magnetic resonance myocardial perfusion imaging: a new era in the detection of reversible myocardial ischaemia

In due course, magnetic resonance myocardial perfusion imaging will probably replace SPECT as the most widely used non-invasive method for detecting reversible myocardial ischaemia.

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.

Diagnostic and prognostic value of non-invasive imaging in known or suspected coronary artery disease

The role of non-invasive imaging techniques in the evaluation of patients with suspected or known coronary artery disease (CAD) has increased exponentially over the past decade. The traditionally available imaging modalities, including nuclear imaging, stress echocardiography and magnetic resonance imaging (MRI), have relied on detection of CAD by visualisation of its functional consequences (i.e. ischaemia). However, extensive research is being invested in the development of non-invasive anatomical imaging using computed tomography or MRI to allow detection of (significant) atherosclerosis, eventually at a preclinical stage. In addition to establishing the presence of or excluding CAD, identification of patients at high risk for cardiac events is of paramount importance to determine post-test management, and the majority of non-invasive imaging tests can also be used for this purpose. The aim of this review is to provide an overview of the available non-invasive imaging modalities and their merits for the diagnostic and prognostic work-up in patients with suspected or known CAD.

Relationship between myocardial perfusion and dysfunction in diabetic cardiomyopathy: a study of quantitative contrast echocardiography and strain rate imaging

OBJECTIVE

To use quantitative myocardial contrast echocardiography (MCE) and strain rate imaging (SRI) to assess the role of microvascular disease in subclinical diabetic cardiomyopathy.

METHODS

Stress MCE and SRI were performed in 48 patients (22 with type II diabetes mellitus (DM) and 26 controls), all with normal left ventricular systolic function and no obstructive coronary disease by quantitative coronary angiography. Real-time MCE was acquired in three apical views at rest and after combined dipyridamole-exercise stress. Myocardial blood flow (MBF) was quantified in the 10 mid- and apical cardiac segments at rest and after stress. Resting peak systolic strain rate (SR) and peak systolic strain (epsilon) were calculated in the same 10 myocardial segments.

RESULTS

The DM and control groups were matched for age, sex and other risk factors, including hypertension. The DM group had higher body mass index and left ventricular mass index. Quantitative SRI analysis was possible in all patients and quantitative MCE in 46 (96%). The mean epsilon, SR and MBF reserve were all significantly lower in the DM group than in controls, with diabetes the only independent predictor of each parameter. No correlation was seen between MBF and SR (r = -0.01, p = 0.54) or between MBF and epsilon (r = -0.20, p = 0.20).

CONCLUSIONS

Quantitative MCE shows that patients with diabetes but no evidence of obstructive coronary artery disease have impaired MBF reserve, but abnormal transmural flow and subclinical longitudinal myocardial dysfunction are not related.