Biomedical subjects
Publications and source records attributed to N C Nanda.
In this report, we present the first case of the transesophageal echocardiographic identification of left subclavian artery stenosis and steal phenomenon.
This case report describes a patient in whom a descending aortic aneurysm ruptured into the left lung, producing hemoptysis. With transesophageal echocardiography, we were able to define the site and extent of the aneurysm, as well as the two sites of rupture into lung tissue.
We present the case of a patient with a single papillary muscle that is supporting both orifices of a stenotic double orifice mitral valve. With the use of both transthoracic and transesophageal echocardiography, we were able to prospectively define this entity, which was confirmed at surgery.
In a patient with previously documented myocardial infarction, we assessed myocardial perfusion by using power contrast imaging and a newer intravenous echo contrast agent. The images were captured and stored digitally, and various image processing algorithms were used to assess myocardial perfusion. An apical perfusion defect was clearly visualized, and it correlated with radionuclide findings.
This case report describes a patient in whom a left internal carotid (LIC) artery stent was detected using a transpharyngeal approach during a transesophageal echocardiographic (TEE) study. Using pulsed-Doppler interrogation, flow through and beyond the stent was characterized and restenosis was ruled out.
A man presented with acute chest and back pain with loss of consciousness. CT scan showed a mass in the arch that extended into the descending aorta. A diagnosis of type I aortic dissection was ultimately made by echocardiography. At surgery there was a circumferential intimal tear in the aortic root, and an intussuscepted dissection flap was retrieved from the arch and descending aorta.
The clinical evaluation of blood flow regurgitation through a heart valve or stenotic lesion is an unresolved problem. The proximal flowfield region has been the study focus in the last few years; however, investigators have failed to identify an accurate and reliable calculation scheme due to lack of geometric information about the shape and size of the regurgitating or stenotic orifice. Presented here is a superior method of calculation, by using three-dimensional (3-D) echocardiography combined with Doppler velocimetry. The geometric structure of the orifice in a regurgitating porcine prosthetic valve in vitro was formulated by 3-D image construction of sequentially obtained 2-D images. The velocity flowfield was accessed by color Doppler flow mapping (CD) and continuous-wave Doppler (CW). Two accurate methods of calculation of regurgitant variables were developed. The first method calculated peak regurgitant flow rate from CD and the second method calculated regurgitant flow volume from CW. Both methods showed excellent correlation with the corresponding true values from an electromagnetic flowmeter. The promising preliminary results in such a realistic porcine model indicate the possibility of establishing a routine procedure to be tested in the clinical setting.
Many noninvasive methodologies used for the accurate evaluation of valvular regurgitation require precise velocity measurements from ultrasound instruments. Previous studies have indicated that velocity measurements from color Doppler (CD) instruments are susceptible to errors due to the interaction of the ultrasound beam and the proximal orifice flow field. This study examined the influence of high aspect ratio (AR) orifices on the CD velocity error. Center line velocity error distributions for orifices ranging from 7.07 to 78.5 mm2, varying in shape from circular to an AR = 8 ellipse, were evaluated using a numerical model of the ultrasound beam and the simulated regurgitant flow field. An in vitro study was also performed and confirmed the findings of the numerical model. The study showed that increasing AR does not significantly change the error characteristics. The study confirmed that orifice size is the dominant factor in the error distribution, and that corrections speculated for circular orifices can be extended to elliptical orifices without significant errors.
There is increasing evidence to believe that Asian Indians are at an increased risk of coronary heart disease (CHD), which cannot be attributed to the common risk factors. Individuals with small, dense LDL phenotype are also known to be at increased risk of CHD. Our objective was to examine whether the prevalence of smaller and denser LDL particles is increased in Asian Indians. Thirty-nine Asian Indians (22 men and 17 women), aged 25 to 45 years, were matched with 39 whites for age and gender. Cholesterol profiles of lipoprotein classes and LDL subclasses were measured using the Vertical Auto Profile-II (VAP-II) and LDL-VAP-II methods, respectively. Six LDL subclasses (LDL1 to LDL6) have been identified using the LDL-VAP-II, with LDL1 and LDL6, respectively, being the most and least buoyant subclasses. The prevalence of small, dense LDL type (subjects with major LDL subclass 5 or 6) was significantly higher in Asian Indians compared with white subjects (44% versus 21%; P<0.05). The relative position of the major LDL density peak (LDL-Rf) on 0 to 1 scale in LDL-VAP-II density gradient was also significantly decreased in Asian Indians (0.462+/-0.076 versus 0. 505+/-0.086; P<0.02), suggesting an increased LDL density. Furthermore, this increased prevalence of small, dense LDL type appears to be due to the increased triglycerides (TG) (r for LDL-Rf versus TG=0.681, P<0.001), with fasting insulin being one of the important determinants of TG (r for TG versus fasting insulin=0.572, P<0.001). In addition, fasting insulin was significantly increased in Asian Indians with small, dense LDL type compared with other Asian Indians, suggesting a significant role of insulin resistance in increasing the prevalence of small, dense LDL type. We conclude that the increased prevalence of small, dense LDL observed in Asian Indians might contribute to their increased CHD risk.
BACKGROUND & AIMS: We have reported that contrast echocardiography is a sensitive screening test for the hepatopulmonary syndrome (HPS). However, contrast echocardiography lacks specificity because many cirrhotic patients have positive study results with normal arterial blood gases and therefore do not fulfill criteria for HPS. The aim of this study was to assess the role of macroaggregated albumin lung perfusion scans (MAA scans) in the diagnosis of HPS. METHODS: MAA scans were performed in 25 patients with HPS, 25 cirrhotic patients without HPS, and 15 hypoxemic subjects with intrinsic lung disease alone. An MAA shunt fraction was calculated from brain and lung counts. RESULTS: MAA scan results were positive in 21 of 25 patients with HPS and negative in all controls. All 21 patients with positive MAA scans had PO2 values of <60 mm Hg. There was a strong inverse correlation between the degree of the MAA shunt fraction and arterial hypoxemia (r = -0.726). CONCLUSIONS: A positive MAA scan result in cirrhosis is specific for the presence of moderate to severe HPS. We speculate that MAA scans may be particularly useful in evaluating the contribution of HPS to the hypoxemia in cirrhotic patients with intrinsic lung disease.
Doppler myocardial imaging (DMI) is a new technique with potential clinical and research applications. It applies traditional pulsed and color Doppler techniques to the analysis of myocardial contractile velocity. A major area of focus is in the quantitation of regional and global myocardial function and evaluation of myocardial perfusion in conjunction with myocardial contrast studies. DMI may also provide a direct, relatively load-independent assessment of diastolic function. Further work is required to identify its role in clinical and research studies.
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The diagnosis and site of graft dehiscence determined by transesophageal echocardiography (TEE), transthoracic echocardiography (TTE), and aortography in 6 patients, and by computed tomography (CT) scan in 3 patients were compared with surgery. Sensitivity of TEE was 100%, aortography 83%, CT scan 67%, and TTE 33%; TEE accurately identified severe aortic regurgitation (3), graft narrowing (2), distal aortic dissection (1), and a fistulous communication between the aortic root and the right ventricle (1) when compared with surgery or aortography.
Contrast-enhanced 2-dimensional echocardiography without color Doppler did not result in complete filling of the left ventricular cavity in 21 patients studied. However, contrast-enhanced color Doppler was very effective and provided complete opacification of the left ventricular cavity in 20 of these 21 patients.
The aim of the study was to compare the accuracy of multiplane transesophageal echocardiography (TEE) with the more conventional biplane technique in the direct assessment of aortic valve area in patients with aortic stenosis. Short-axis images of the aortic valve adequate for measuring aortic valve area were obtained in all 81 patients studied by multiplane TEE but in only 56 of 64 patients (88%) using the biplane approach. The correlation coefficient for aortic valve area determined by multiplane TEE (r = 0.89; SEE = 0.04 cm2) was higher (p < 0.01) than biplane TEE (r = 0.74; SEE = 0.06 cm2). Correlations were higher for bicuspid valves (multiplane, r = 0.93; biplane, r = 0.75) than tricuspid valves (multiplane, r = 0.87; biplane, r = 0.75). Our study has demonstrated the superiority of multiplane TEE to both biplane TEE and transthoracic echocardiography (TTE) in the direct evaluation of aortic valve area in patients with aortic stenosis.
Echo enhancing agents have been used in echocardiography since 1968 for a variety of applications. Until recently, the agents were unable to survive transit through the pulmonary circulation following intravenous injection, and the technique was therefore restricted to investigations of the right side of the heart. Levovist is an echo enhancing agent capable of left heart--and even systemic--enhancement to improve the images obtained with B-mode and Doppler echocardiography. This agent offers important practical advantages in "routine" echocardiography, particularly in patients in whom image quality is suboptimal or baseline examination fails due to physical limitations. Potential future uses of contrast-enhanced echocardiography include quantitative analysis of coronary artery flow.
Since its experimental introduction over 30 years ago, the use of cardiac ultrasound has expanded expeditiously, particularly in the last decade. The inception of managed care has fueled this expansion because ultrasound technology has the potential to enhance cost-effective diagnosis and medical care. Another important factor driving the growth of cardiac ultrasound has been the recent and rapid development of contrast echocardiography (CE). This diagnostic technique, involving the injection of a contrast agent to enhance ultrasound imaging, provides a safe, noninvasive means of directly assessing myocardial perfusion and a host of other aspects of cardiovascular health and integrity.