Detection Of Myocardial Perfusion Research Articles

The clinical applications of myocardial contrast echocardiography

Recent updates in the field of echocardiography have resulted in improvements in both image quality and techniques allowing echocardiography to maintain it's position as the primary non-invasive imaging modality. In particular, the development of new ultrasound contrast agents and imaging techniques have now made possible the assessment of myocardial perfusion. Myocardial contrast echocardiography utilises acoustically active gas filled microspheres (microbubbles), which have rheology similar to that of red blood cells. The detection of myocardial perfusion during echocardiographic examinations permits simultaneous assessment of global and regional myocardial structure, function, and perfusion, enabling the optimal non-invasive assessment of coronary artery disease. Myocardial contrast echocardiography is equally adept in assessing chronic coronary artery disease, acute coronary syndromes and hibernating myocardium.

Myocardial Contrast Echocardiography: Role in Clinical Cardiology

Recent updates in the field of echocardiography have resulted in improvements in both image quality and techniques allowing echocardiography to maintain its position as the primary non-invasive imaging modality. In particular, the development of new ultrasound contrast agents and imaging techniques have now made possible the assessment of myocardial perfusion. Myocardial contrast echocardiography utilises acoustically active gas filled microspheres (microbubbles), which have rheology similar to that of red blood cells. The detection of myocardial perfusion during echocardiographic examinations permits simultaneous assessment of global and regional myocardial structure, function, and perfusion, enabling the optimal non-invasive assessment of coronary artery disease. Myocardial contrast echocardiography is equally adept in assessing chronic coronary artery disease as well as acute coronary syndromes. Furthermore, its use is not limited solely to diagnostic assessment. Preliminary evidence suggests that targeted microbubbles may be useful in enhancing delivery of genes / drugs and in clot lysis.

178 Quantitative evaluation of regional myocardial perfusion during dipyridamole stress by real-time myocardial contrast echocardiography in patients with and without coronary artery disease

178 Quantitative evaluation of regional myocardial perfusion during dipyridamole stress by real-time myocardial contrast echocardiography in patients with and without coronary artery disease

Usefulness of concomitant myoglobin and troponin elevation as a biochemical marker of mortality in non–ST-segment elevation acute coronary syndromes

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Effect of destructive pulse duration on the detection of myocardial perfusion in myocardial contrast echocardiography: In vitro and in vivo observations

Myocardial perfusion is detected with contrast echocardiography by comparing a contrast-enhanced image with a baseline obtained before contrast injection (true baseline) or after myocardial bubble destruction after a high-power destructive pulse (postdestructive pulse baseline). Although it is assumed that all bubbles are destroyed by a destructive pulse insuring optimal contrast detection, this assumption has not been tested. In 18 participants we compared the videointensity (VI) differences among the contrast-enhanced image, the postdestructive pulse baseline, and the true baseline using both triggered high-mechanical index imaging and real-time imaging. VI difference was significantly greater for the true baseline with both techniques at all ventricular levels. The benefit of using a true baseline was less when the duration of the destructive pulse was increased. Similarly, we quantified VI in a flow phantom using continuous Optison (commercially available perfluoropropane-filled albumin microbubbles) (Amersham, Princeton, NJ) infusion and variable durations of destructive pulses. VI decreased with the duration of the destructive pulse and reached a plateau after a duration of 8 to 15 frames. The plateau reached after a long destructive pulse was dependent on flow rate and concentration and never reached a true baseline, unless concentration (<100 μL/L) and flow rate (<0.5 cm/s) were very low. In conclusion: (1) in clinical studies, the difference in VI between contrast-enhanced and baseline images is greater when true baseline is used; (2) the longer the destructive pulse, the closer the postdestructive pulse baseline to true baseline; and (3) this effect exists in all regions of the left ventricle. (J Am Soc Echocardiogr 2002;15:1440-7.)

Recent advances in myocardial contrast echocardiography.

Myocardial contrast echocardiography (MCE) has undergone many advances in the past several years through remarkable developments in contrast agent and ultrasound equipment technology. Microbubble ultrasound contrast agents can now safely transit the pulmonary circulation to provide opacification of the left ventricular cavity, improved endocardial border definition, and detection of myocardial perfusion. The role of contrast echocardiography in enhancing technically difficult images is now well established in clinical practice, and has proven especially useful in the stress and intensive care unit settings. Major progress has been made in the application of MCE for myocardial perfusion assessment in acute and chronic ischemic heart disease syndromes, and comprises the focus of this review. Advances in novel applications of contrast echocardiography, including targeted delivery of genetic and pharmaceutical materials, have also occurred, but remain in a preclinical phase. In summary, the combination of recent innovations in ultrasound equipment, and microbubble acoustics, allows for exciting exploration of the expanding role of contrast echocardiography in clinical practice.

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. (J Am Soc Echocardiogr 2000;13: 331-42.)

Detection of Myocardial Perfusion in Multiple Echocardiographic Windows With One Intravenous Injection of Microbubbles Using Transient Response Second Harmonic Imaging

Objectives. The purpose of this study was to prove that transient response harmonic imaging could detect normal and abnormal myocardial perfusion in multiple echocardiographic windows with one intravenous injection of microbubbles in humans.Background. Myocardial ultrasound contrast can be produced from intravenous perfluorocarbon-exposed sonicated dextrose albumin, and ultrasound can be significantly improved by briefly suspending the interval between frame rates. Whether this contrast can noninvasively quantify myocardial perfusion in humans is unknown.Methods. In 28 patients, harmonic transient response imaging was used to image the heart in multiple different imaging planes after one intravenous injection of ultrasound contrast agent. Twenty-five of these 28 patients had a repeat injection during dipyridamole stress. In the primary view, the ultrasound transmission rate was one frame per cardiac cycle; in secondary and tertiary views, the transmission rate was once every multiple cardiac cycles. Regional myocardial contrast was visually assessed and quantified off-line. Quantitative rest thallium and dipyridamole stress sestamibi imaging was also performed.Results. Perfusion abnormalities were evident in the secondary and tertiary views only with one frame every multiple cardiac cycles. Regional peak myocardial videointensity (PMVI) correlated closely with regional tracer uptake in individual patients both at rest (r = 0.84) and during stress (r = 0.88). A PMVI ratio (abnormal region divided by the region with highest nuclear uptake) <0.6 in any view had a 92% sensitivity and a 84% specificity in identifying a regional nuclear perfusion abnormality.Conclusions. Transient response imaging produces myocardial contrast in multiple views with one intravenous injection of contrast agent and can accurately identify regional myocardial perfusion abnormalities.(J Am Coll Cardiol 1997;29:791–9)

Myocardial contrast echocardiography: enhancement of perfusion images by color coding.

To determine whether real-time color coding enhances the detection of myocardial perfusion through the use of echocardiographic contrast agents, we used a recently developed real-time color system during contrast injection in six open-chest dogs. Small amounts of echocardiographic contrast were injected into the left atrium. Short-axis epicardial images were obtained with a 5-MHz transducer before and after left anterior descending artery ligation. Gray-scale and rainbow-color map images were obtained for each contrast agent. The color map allowed detection of small increments in echo intensity that were not evident with routine gray-scale imaging. Thus, real-time color coding may improve the detection of myocardial perfusion with echocardiographic contrast agents.

Digital radiofrequency echocardiography in the detection of myocardial contrast following intravenous administration of Albunex(R)

Conventional contrast echo techniques have proved inadequate for the detection of myocardial perfusion using intravenously injected echo contrast agents because of the limitations and relative insensitivity of standard echocardiographic equipment. In order to avoid these problems, we have obtained pure digital radiofrequency ultrasound data from the left ventricle and myocardium during i.v. contrast myocardial perfusion echo studies. In 30 patients, following coronary arteriography, i.v. injections of the echo contrast agent Albunex (sonicated human serum albumin) in two doses of 0.08 and 0.22 ml.kg-1 were administered during digital radiofrequency echocardiography sampling of data from the myocardium and left ventricular cavity. Analysis of mean integrated backscatter (MIB, a measure of the total ultrasound energy) was performed before, during and after Albunex injection. The data were also analysed for a shift in frequency spectrum which could be caused by resonance of the Albunex contrast microspheres in the heart, a phenomenon which has been previously demonstrated in vitro. Digital radiofrequency ultrasound data were successfully obtained and analysed in 23 patients. In 31 segments where reasonable resting perfusion was expected, there was a significant increase in MIB from 0.644 to 1.245, P < 0.001 and time intensity curves could be constructed showing wash-in and wash-out of contrast from the myocardium. In 10 segments supplied by significantly diseased vessels, MIB intensity increased from 1.044 to 1.874, P = 0.054. In myocardial segments supplied by non-diseased vessels, microsphere resonance also caused a drop in mean frequency of 140 KHz, P < 0.001, and permitted similar temporal analysis of myocardial perfusion.(ABSTRACT TRUNCATED AT 250 WORDS)