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Biomedical subjects

Mani A Vannan

Publications and source records attributed to Mani A Vannan.

14 recordsLinked to original sources
PubMed2004

Catheter-based intracardiac echocardiography in the interventional cardiac laboratory.

Recent advances in technology have engendered a renewed enthusiasm in the use of intracardiac echocardiography (ICE) to guide and assess cardiac interventions. AcuNav is a phased-array sector imaging probe equipped with color and spectral Doppler capabilities. Previous-generation imaging catheters yielded unfamiliar limited-depth radial images with no flow information. Current imaging technology such as the AcuNav has not only consolidated the role of ICE but opened newer applications in the interventional laboratory. ICE has clear advantages over transesophageal echocardiography as the imaging modality of choice in the cardiac catheterization and electrophysiological laboratories. We review the technical evolution of ICE and describe the expanded utility of the AcuNav imaging catheter during cardiac interventions.

Cardiac Catheterization↗
PubMed2004

Microbubble contrast agents for echocardiography: rationale, composition, ultrasound interactions, and safety.

Imaging the small blood vessels within the myocardium, which contains only a small fraction of the total coronary blood volume, is a significant challenge for ultrasound imaging. Recent advances in microbubble design and ultrasound technology have improved our ability to image the microcirculation. It is essential to understand the fundamentals of microbubble behavior in an ultrasound field and how it impacts technology and safety.

Coronary Vessels↗
PubMed2004

Imaging technologies and techniques.

Equipment manufacturers provide contrast-specific detection techniques that have excellent sensitivity and excellent agent-to-tissue specificity along with helpful tools that improve workflow efficiency dramatically. Excellent contrast agents have been approved for LV opacification and are available worldwide. Techniques designed for low-MI imaging offer real-time acquisition capabilities and lead to faster examinations. Techniques designed for medium-MI imaging offer better sensitivity than low-MI techniques while maintaining the benefit of rapid image acquisition. Techniques designed for high-MI imaging offer the best sensitivity with longer acquisition times. These techniques are viable means for imaging contrast agents tailored to clinical needs. Progress by contrast agent manufacturers, equipment manufacturers, and physicians will continue to drive improvements in the areas of detection and clinical workflow for improved patient care.

Coronary Circulation↗
PubMed2004

Myocardial contrast echocardiography in acute coronary syndromes.

MCE is a reliable, bedside technique for assessment of a patient with acute coronary syndrome. It can be used to estimate the myocardial risk-area and infarct size and to establish peri-infarct viability. This information is critical in both management decision-making and in assigning prognosis in the setting of acute coronary syndromes.

Echocardiography↗
PubMed2004

Targeted ultrasound imaging using microbubbles.

Targeted ultrasound imaging uses acoustically active contrast agents bearing a ligand on the surface that binds to a function-specific molecule. These ultrasound contrast agents are typically gas-filled microbubbles, nongaseous liposomes, or lipid-encapsulated perfluorocarbon emulsions. Binding of the contrast agent to the target results in persistent contrast enhancement during ultrasound imaging. This approach has been applied to the ultrasound imaging of pathophysiologic processes such as inflammation associated with ischemia reperfusion, heart transplant rejection, atherosclerotic plaque, thrombus, and apoptosis.

Animals↗
PubMed2004

Myocardial contrast echocardiography in chronic ischemic and nonischemic cardiomyopathies.

The coronary microcirculation is integral in the pathophysiology of both ischemic and non-ischemic cardiomyopathies. MCE is a unique tool for studying microcirculatory integrity, not only to aid diagnosis and determination of prognosis but also to guide interventions and management. The expanding paradigm of microcirculatory disturbances may in the future also include hypertensive and diabetic heart disease.

Cardiomyopathies↗
PubMed2003

Targeting of apoptotic macrophages and experimental atheroma with radiolabeled annexin V: a technique with potential for noninvasive imaging of vulnerable plaque.

BACKGROUND: Apoptosis is common in advanced human atheroma and contributes to plaque instability. Because annexin V has a high affinity for exposed phosphatidylserine on apoptotic cells, radiolabeled annexin V may be used for noninvasive detection of apoptosis in atherosclerotic lesions. METHODS AND RESULTS: Atherosclerotic plaques were produced in 5 rabbits by deendothelialization of the infradiaphragmatic aorta followed by 12 weeks of cholesterol diet; 5 controls were studied without manipulation. Animals were injected with human recombinant annexin V labeled with technetium-99m before imaging. Aortas were explanted for ex vivo imaging, macroautoradiography, and histological characterization of plaque. Radiolabeled annexin V cleared rapidly from the circulation (T1/2, alpha 9 and beta 46 minutes). There was intense uptake of radiolabel within lesions by 2 hours; no uptake was seen in controls. The results were confirmed in the ex vivo imaging of the explanted aorta. Quantitative annexin uptake was 9.3-fold higher in lesion versus nonlesion areas; the lesion-to-blood ratio was 3.0+/-0.37. Annexin uptake paralleled lesion severity and macrophage burden; no correlation was observed with smooth muscle cells. DNA fragmentation staining of apoptotic nuclei was increased in advanced lesions with evolving necrotic cores, predominantly in macrophages; the uptake of radiolabel correlated with the apoptotic index. CONCLUSIONS: Because annexin V clears rapidly from blood and targets apoptotic macrophage population, it should constitute an attractive imaging agent for the noninvasive detection of unstable atherosclerotic plaques.

Animals↗
PubMed2003

Delineation of intracardiac shunts using contrast echocardiography.

Contrast echocardiography is useful to visualize the endocardial borders of the left ventricle and improve the signal intensity of spectral Doppler signals. It can also help to define intracardiac flow dynamics in complex situations. We report 2 cases where contrast echocardiography improved the delineation of complex shunts and also provided new information not available by conventional echocardiography.

Adult↗
PubMed2003

Detection of resting myocardial perfusion defects by SonoVue myocardial contrast echocardiography.

BACKGROUND: SonoVue is a new microbubble contrast agent containing sulfur hexafluoride. We assessed the efficacy of SonoVue myocardial contrast echocardiography (MCE) to detect resting perfusion abnormalities. METHODS: Nineteen adult patients with a wall motion abnormality in a screening echocardiogram were studied. Each patient received up to four bolus injections of 2.0 mL SonoVue (Bracco Diagnostics, Inc.) during echocardiographic examination using either B-mode(n = 12)or power Doppler(n = 7)imaging. Each patient also had SPECT nuclear perfusion imaging performed. Segmental assessment of myocardial perfusion from SonoVue MCE images were compared with corresponding SPECT nuclear images. RESULTS: Using B-mode imaging, the mean number of views obtained with a single SonoVue injection ranged from 1.4 to 1.9, with 2 or 3 injections required for a complete examination. Ninety-four percent of segments were scored as diagnostic. Agreement between B-mode and SPECT images was 72% for segments with a perfusion defect, 86% for normal perfusion, and 80% for segments with either perfusion defect or normal perfusion (all views combined). Using power Doppler imaging, the mean number of views obtained with a single SonoVue injection ranged from 1.0 to 1.3, with 2 to 4 injections required for a complete examination. Sixty-eight percent of segments were scored as diagnostic. Agreement between power Doppler and SPECT images was 67% for perfusion defects, 53% for segments with normal perfusion, and 59% for segments with either perfusion defect or normal perfusion (all views combined). CONCLUSIONS: SonoVue MCE has the potential to assess myocardial perfusion at rest. B-mode imaging was more accurate than power Doppler imaging when compared with SPECT nuclear imaging.

Aged↗
PubMed2003

Myocardial contrast echocardiography in acute myocardial infarction.

PURPOSE OF REVIEW: Myocardial contrast echocardiography (MCE) has evolved into an important clinical tool for imaging coronary microcirculation. It can be used to delineate the spectrum of perfusion derangements that characterize acute myocardial infarction. RECENT FINDINGS: Presently, MCE uses microcirculatory perfusion as the basis to distinguish myocardial necrosis and viability in the post-infarct stage. Its future role may expand to image cellular integrity, inflammation, and angiogenesis, all of which contribute to the pathophysiology of the myocardial infarction. SUMMARY: This review provides an update of the current role and future clinical applications of MCE in acute myocardial infarction.

Acute Disease↗
PubMed2002

Methods of contrast administration for myocardial perfusion imaging: continuous infusion versus bolus injection.

The debate over the optimal contrast administration method involves many issues. This article discusses bolus versus infusion administration pertaining to myocardial perfusion imaging. Continuous infusion ensures efficient and optimal data capture during contrast studies and is preferred over bolus injection for both theoretical and practical reasons. Although bolus administration is easier, its relative disadvantages outweigh its usefulness in myocardial perfusion imaging.

Contrast Media↗
PubMed2002

Catheter-based interventions guided solely by a new phased-array intracardiac imaging catheter: in vivo experimental studies.

BACKGROUND: Intracardiac echocardiography (ICE) has had useful but limited use during interventional procedures because of technologic limitations. We used a novel phased-array ICE device (AcuNav) with 2-dimensional sector imaging and full Doppler capability to see whether it could guide cardiac interventions without fluoroscopy. METHODS: Twelve dogs were studied, and we performed atrial septostomy, tricuspid, and pulmonary valve disruption using only ICE. Preinterventional and postinterventional anatomic and hemodynamic data were noted. RESULTS: All attempts were successful in the placement of the ICE catheter (100%). We attempted septostomy on 11 dogs and were successful 8 times (73%). Tricuspid valve disruption and balloon dilatation were performed successfully on 5 dogs (100%). We attempted pulmonary valve disruption on 4 dogs and could always correctly place the guidewire (100%). We performed pulmonary valve balloon dilatation on one dog (25%). A comprehensive echocardiographic examination was always possible. CONCLUSION: This new ICE device can guide interventions without fluoroscopy. However, further studies are needed to evaluate whether it can replace fluoroscopy.

Animals↗
PubMed2002

Anatomic and hemodynamic imaging using a new vector phased-array intracardiac catheter.

BACKGROUND: We used a new vector, phased-array intracardiac catheter (AcuNav) with complete 2-dimensional imaging and Doppler capabilities to describe a systematic approach for a detailed anatomic and hemodynamic cardiac assessment. METHODS: In 14 dogs, the intracardiac echocardiographic catheter was inserted through an 11F venous access and placed in the right side of the heart to perform a comprehensive ultrasound examination of the heart. RESULTS: Imaging was successful in all dogs. All 4 cardiac chambers and valves were imaged clearly in multiple orientations. Additional structures seen included the vena cavae, coronary sinus, right and left appendages, interarterial septum, coronary arteries, and all 4 pulmonary veins. Intra-abdominal structures, such as the aorta, liver, and hepatic veins were also visualized. A complete Doppler examination of intracardiac and paracardiac flows was also possible. CONCLUSION: AcuNav is a unique intracardiac imaging device, which allows comprehensive structural and functional cardiac assessment.

Algorithms↗