Biomedical subjects
Publications and source records attributed to Navin C. Nanda.
Three-dimensional echocardiographic findings in cor triatriatum sinister (sinistrum), cor triatriatum dexter, mitral supravalvular membrane, and atrial baffle are presented.
Stress echocardiography, both pharmacologic and physiological, is an established noninvasive diagnostic method of detecting coronary artery disease. It also has a role in the assessment of patients with chest pain, the assessment of cardiovascular risk before noncardiac surgery, the assessment of patients after a myocardial infarction, the detection of viability in dysfunctional myocardium, and the prediction of functional recovery. The prognostic value of stress echocardiography is emerging. In this article, we discuss the methodology, diagnostic accuracy, and various clinical applications of stress echocardiography. We also review its limitations and compared it with other noninvasive methods of assessing patients with coronary artery disease.
Traumatic rupture of aortic isthmus atherosclerotic plaque resulting in dissection has not been documented through the use of either invasive or noninvasive diagnostic modalities. We describe an elderly patient in whom transesophageal echocardiography and three-dimensional reconstruction of multiplane transesophageal two-dimensional images clearly demonstrated the traumatic dissection to be due to rupture of a large atherosclerotic plaque located in the aortic isthmus. The patient had experienced blunt trauma to the chest from the impact of the steering wheel during an automobile accident.
In this case report, we present the utility of transesophageal echocardiography in the detection of two uncommon complications of left ventricular assist devices: regurgitation of the bioprosthetic valve in the inflow conduit and a tear of a Dacron conduit with hematoma formation and compression of the right ventricular free wall.
In the present study, we report our experience of using three-dimensional reconstruction of transesophageal two-dimensional echocardiographic images in the assessment of aortic dissection (22 patients), aortic rupture (1 patient), aortic aneurysm without dissection (2 patients), and aortic tumor (1 patient).
The present study demonstrates the feasibility of delineating the carotid bulb and the proximal portions of the left external and left internal carotid arteries during transesophageal examination. This was accomplished by slowly and carefully withdrawing the probe from the esophagus into the pharynx.
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Transient imaging has been introduced to enhance the signal intensities when using echo contrast agents. However, this phenomenon is not clearly understood. To evaluate the mechanisms of this phenomenon, isolated pig hearts were investigated with different echo imaging techniques in the beating, working heart as well as in an asystolic state without any motion of the heart. The hearts of five German farm pigs (21 +/- 2.5 kg) were surgically explanted and inserted in an artificial circulation providing physiological flow and pressures. Levovist in the dosage of 0.05-0.3 g was injected into the left atrium and contrast effects evaluated in the left ventricular (LV) cavity and in the myocardium with an ultrasound imager (ATL, HDI 3000) equipped with a prototype software for harmonic imaging. Harmonic B-scans and power Doppler registrations were performed with continuous and intermittent recordings (ECG triggered at end-systole) in the beating heart and using an external trigger in the asystolic heart in which perfusion was interrupted for 20 seconds. In the beating pig heart, transient harmonic power Doppler imaging provided intensive opacification of the LV cavity and visible myocardial uptake when ECG triggering was performed. In the asystolic pig heart, with uninterrupted perfusion, both triggered and nontriggered registrations showed contrast signals in the LV cavity and in the myocardium. These findings cannot be explained with the known physics of ultrasound contrast media. Stimulated acoustic emission occurring during disintegration of the microbubbles in the acoustic field would explain this phenomenon, which has not yet been described for Levovist.
We describe a case report where a left atrial catheter inserted intraoperatively produced an artifact, which mimicked a catheter in the left ventricle during transesophageal echocardiographic examination.
Six months following Carbomedics mitral and aortic valve replacement, multiplane transesophageal echocardiography performed (TEE) in a 49-year-old black gentleman showed a prominent 1.0-cm linear echo protruding into the left atrium at the mid-interatrial septal level distal to the sewing ring. Plane angulations at 105 and 111 degrees demonstrated the linear echo to be related to left atrial wall dehiscence indicated by the presence of a cavitary defect at the same level. At the time of surgery, a 1.0 cm-paravalvular defect and dehiscence of the left atrial wall distal to the sewing ring 2.0 centimeters anterior to the posteromedial commisure were found.
Dynamic three-dimensional (3-D) echocardiography has so far focused on reconstruction of cardiac structures. In this preliminary study, abnormal intracardiac blood flow has been reconstructed in 3-D from multiplane transesophageal and transthoracic two-dimensional (2-D) echocardiograms using modified omniplane probes with 3.7- or 5.0-MHz transducers. The study group included patients with native (40) and prosthetic (11) mitral regurgitant jets, aortic regurgitant jets (8), and shunt flow in atrial septal defect (20), ventricular septal defect (19), tetralogy of Fallot (14), and ruptured sinus of Valsalva aneurysm (6). For dynamic 3-D intracardiac flow imaging the gain of 2-D images of cardiac structures was lowered slightly and color Doppler flow signals were transformed into gray scale flow signals, which were then collected in the TomTec 3-D Echo Scan System. Dynamic 3-D cardiac flow images were displayed with volume rendering. The results indicated that dynamic 3-D cardiac flow imaging facilitates display of the stereo shape, spatial orientation, profiles and volume of regurgitant jets, and the intracardiac shunting blood flow. It allows differentiation of prosthetic transvalvular from paravalvular regurgitant jets. Limitations include nonvelocity and nonECG synchronized display.
We describe the presence of a localized echo-free space behind the ascending aorta, which could mimic an aortic dissection. This space was confirmed to be the left atrium by intraoperative contrast echocardiography.
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In this report we describe the technique used for identification of the individual aortic arch vessels using transesophageal echocardiography.
This preliminary experimental study demonstrates the potential usefulness of harmonic power Doppler imaging in producing left ventricular myocardial opacification and demonstrating intramyocardial coronary vessels during contrast echocardiography using Levovist, a saccharide-based contrast agent. The contrast effect was most dramatic when a vasodilator such as dipyridamole or nitroglycerin was used in conjunction with contrast injections of Levovist. No significant myocardial opacification was noted with B-mode harmonic imaging alone.
BACKGROUND: In fundamental and second harmonic echocardiography new contrast media opacify the cavities and reduce the difference in the gray level between the cavity and the myocardium thus obscuring the borders of the myocardium. OBJECTIVES: The aim of the study was to examine the potential usefulness of second harmonic power Doppler imaging (HPD) in providing adequate delineation of the myocardium from the left ventricular (LV) and right ventricular (RV) cavities during intravenous contrast echocardiography. Using HPD, microbubbles in a cavity or a tissue are imaged as colored pixels superimposed on a conventional B-scan image. METHODS: In a pilot study, three healthy volunteers and two patients with ischemic heart disease were investigated using an ATL-HDI 3000 echo system. Four chamber views were obtained using fundamental B-scan, harmonic B-scan two-dimensional echocardiography (H2D) and HPD following intravenous injections of 3 g Levovist(R). RESULTS: Using intermittent scanning/recording, H2D and HPD provided intensive and homogenous contrast effects in the RV and LV cavities. Good delineation of the myocardium was found in all subjects using HPD, whereas in two of three volunteers and in one of two patients ventricular septal and apical endocardial borders were obscured during H2D. No obvious change in myocardial backscatter was visually found with H2D. However, in all three healthy volunteers and in one of two patients, HPD recordings demonstrated patchy and reticular patterns in the myocardium, which were different from the homogenous signals in the LV cavity. These are consistent with imaging of intramyocardial coronary vessels. CONCLUSIONS: HPD with intravenous Levovist is feasible. This technique demonstrated good delineation of ventricular cavities from the myocardium as well as presence of visible contrast in the myocardium. This pilot study justifies further clinical trials to evaluate the clinical benefit of this approach.
We report the usefulness of transesophageal echocardiography in evaluating a patient with sclerosing mediastinitis. The technique enabled us to identify a mass obstructing the superior vena cava and right upper and lower pulmonary veins, and infiltrating and invaginating into the left atrial cavity. Transesophageal echocardiography was superior to computed tomography and transthoracic echocardiography in delineating these findings. (ECHOCARDIOGRAPHY, Volume 13, January 1996)
In this report, we describe how transesophageal echocardiography was used not only to diagnose incorrect cannula position of a right ventricular assist device in the left atrium through a patent foramen ovale, but also to guide and to confirm correct cannula placement. (ECHOCARDIOGRAPHY, Volume 13, March 1996)