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Biomedical subjects

N C Nanda

Publications and source records attributed to N C Nanda.

At least 91 records · Page 5Linked to original sources
PubMed1992

Transesophageal echocardiographic diagnosis of multicentric left ventricular myxomas mimicking a left atrial tumor.

We report a case of multicentric left ventricular myxomas with prolapse of one myxoma into the left atrium during ventricular systole that mimicked a left atrial tumor. The transthoracic echocardiogram showed large masses in the region of the mitral valve leaflets consistent with vegetations or tumors. A computed tomographic scan of the chest demonstrated two distinct left atrial masses, one of which appeared to prolapse from the left atrium into the left ventricle. Intraoperative transesophageal echocardiography showed a large pedunculated mass moving between the two left-sided cardiac chambers with intermittent trapping of the mass in the left atrium. The mass was attached to the left ventricular posteromedial papillary muscle by a long stalk. Another adjacent large ventricular mass was also noted in the left ventricle. These findings were confirmed at operation, which also demonstrated a third small tumor arising from the atrial aspect of the posterior mitral leaflet.

Adult↗
PubMed1991

Value and limitations of color Doppler echocardiography in the evaluation of percutaneous balloon mitral valvuloplasty for isolated mitral stenosis.

The limitations of 2-dimensional and pulsed Doppler echocardiography in patients undergoing mitral valvuloplasty are well known. This study was undertaken to assess the value of color Doppler flow imaging in 36 symptomatic mitral stenosis patients who subsequently underwent successful balloon mitral valvuloplasty by comparing the results to those obtained at cardiac catheterization. Color Doppler-guided conventional Doppler assessment agreed well with cardiac catheterization results in classifying mitral stenosis as mild, moderately severe and severe, both before and after valvuloplasty. Color Doppler was also useful in identifying patients who had moderate to severe mitral regurgitation before and after valvuloplasty. Color Doppler flow mapping was more sensitive than oximetry in the detection of iatrogenic atrial septal defects, which were noted in 25 patients. The defects of those patients with smaller defects by color Doppler (diameter less than 0.7 cm) or echocardiographic shunt volume less than 0.7 liters/min tended to close, usually within 6 months, as opposed to those with larger defects or higher shunt volumes, which tended to persist. Echocardiographic shunt volumes revealed a fair correlation with oximetric results.

Cardiac Catheterization↗
PubMed1991

Uses and limitations of transthoracic echocardiography in the assessment of atrial septal defect in the adult.

Two-dimensional and color Doppler echocardiography accurately detected the presence of an atrial septal defect (ASD) in 47 of 50 adults (mean age 40 years) confirmed by surgery or cardiac catheterization, or both. It correctly categorized all patients with ostium secundum and ostium primum ASD but misdiagnosed 3 of 5 patients with surgically proven sinus venosus ASD. The shunt flow volume across the ASD was calculated with the standard Doppler equation, and assuming the ASD to be circular correlated with shunt flow volume obtained by cardiac catheterization (r = 0.74). The maximum width of the color flow signals moving across the ASD was taken as its diameter. Mean flow velocity was determined either by placing a pulsed Doppler sample volume parallel to the flow across the ASD as visualized by color Doppler or by color M-mode examination, which allowed determination of flow velocities using a previously validated method that incorporates a computer analysis of pixel color intensity. The pulmonary to systemic blood flow ratio obtained by color-guided conventional Doppler interrogation of the left and right ventricular outflow tracts correlated poorly with cardiac catheterization results (r = 0.38). In patients with associated tricuspid regurgitation, the peak systolic pulmonary artery pressure obtained by color Doppler-guided continuous-wave Doppler correlated well with that obtained at cardiac catheterization (r = 0.89). The maximum color Doppler jet width of the flow across the ASD poorly correlated with ASD size estimated at surgery (r = 0.50).

Adolescent↗
PubMed1991

Removal of massive right atrial thrombus guided by transesophageal echocardiography.

Formation of massive right atrial thrombi around a peritoneovenous shunt is a known complication of these devices. Removal of an obstructive right atrial thrombus requires cardiopulmonary bypass and has been associated with a high morbidity and mortality. Transesophageal echocardiography was used in this case to diagnose and guide the surgical removal of a massive right atrial thrombus.

Adult↗
PubMed1991

Influence of various instrument settings on the flow information derived from the power mode.

To evaluate the factors influencing flow information displayed by the power operating mode, color Doppler flow mapping was used to image the flow in an in vitro left heart pulse duplicator system. The effect of changing one instrument setting, such as pulse repetition frequency, color filter and frame rate while keeping all other instrumental settings constant, was noted on the displayed flow areas. The flow areas derived using power and velocity modes were also compared. An increase in pulse repetition frequency and color filter decreased the flow areas significantly, and a flow area increase occurred with a decrease in frame rate. No significant difference was observed between the flow areas derived using the two operating modes. Like the velocity mode, the power mode display is also influenced by instrument settings. Although low velocity flows are better delineated using this mode, however, no significant difference occurred in the flow areas measured by this mode and velocity mode. Further studies need to be conducted to address its potential applications in the clinical setting and in quantitation.

Blood Flow Velocity↗
PubMed1991

Amplitude information from Doppler color flow mapping systems: a preliminary study of the power mode.

The flow of a saline-glycerin solution with sand particles through a continuous in vitro flow system was imaged by using two commercially available Doppler color flow mapping systems in a power mode (Toshiba SSH-160A and Advanced Technology Laboratories [ATL] Ultramark 9). The images generated from seven solutions with particle concentrations ranging from 0.0001 x 10(12) to 6 x 10(12) particles/liter and a mean velocity of 30 cm/s measured with use of pulsed Doppler ultrasound were used to examine the dependence of the power mode on particle concentration. To examine the velocity dependence, 20 mean velocities ranging from 0.1 to 0.53 m/s (3 to 30 liters/min) and three particle concentrations (1, 3 and 6 x 10(12) particles/liter) in the solution were used. The recorded images were digitized and analyzed off-line. The SUM values, or the adjusted color intensity levels in delineated areas of interest in the displayed flow, were compared. In general, the power mode was sensitive in displaying slower velocity flows; in the selected particle concentration and velocity ranges, it was both velocity and concentration dependent. The specific dependence differed for the two color flow mapping systems.

Blood Flow Velocity↗
PubMed1991

Transesophageal echocardiographic imaging of the pulmonary veins.

This report focuses on the technical aspects of the assessment of pulmonary veins using biplane transesophageal echocardiography, taking into account their spatial anatomical orientation and relationship to neighboring structures. This is aimed at increasing the echocardiographer's ability to visualize the proximal segments of all four pulmonary veins.

Echocardiography, Doppler↗
PubMed1991

Transesophageal echocardiography in aortopulmonary communications.

The assessment of congenital aortopulmonary communications by transthoracic echocardiography may be suboptimal, particularly postoperatively, due to limited acoustic windows. We performed intraoperative transesophageal echocardiograms in six patients with eight proven systemic-pulmonary communications. Diagnosis included truncus arteriosus (1), aortopulmonary window (1), Waterston anastomosis (3), central Gore-Tex shunt (1), and modified left Blalock-Taussig shunt (2). All communications were accurately demonstrated by transesophageal echocardiography (TEE). The transesophageal technique also provided an assessment of the size of the aortopulmonary communications and the proximal pulmonary arteries. In addition, the gradient across some of the communications could be accurately estimated utilizing the high pulse repetition frequency Doppler. On the other hand, only two of the seven aortopulmonary communications were detected by transthoracic echocardiography. Postoperatively, transesophageal imaging demonstrated unobstructed conduit in five of five patients who underwent conduit repair, as well as intact closure of aortopulmonary communications and concomitant closure of ventricular septal defects.

Aortopulmonary Septal Defect↗