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Biomedical subjects

N C Nanda

Publications and source records attributed to N C Nanda.

At least 109 records · Page 6Linked to original sources
PubMed1991

Usefulness of transesophageal echocardiography in assessment of aortic dissection.

BACKGROUND: The value of transesophageal echocardiography in the assessment of patients with aortic dissection was studied. METHODS AND RESULTS: Group 1 (34 patients) represented all patients studied at our institution with this technique in whom aortic dissection was proven by aortography, surgery, or autopsy. Group 2 (27 patients) represented all patients studied with this technique at our institution in whom aortic dissection was excluded by aortography. Transesophageal echocardiography made a correct diagnosis of aortic dissection in 33 of 34 patients (sensitivity, 97%; specificity, 100%). It also correctly demonstrated the type of dissection in all 29 patients with aortographic or surgical proof. On the other hand, computed tomography scanning, performed in 24 of 34 patients in group 1, made a correct diagnosis in only 67% of patients and misclassified the type of dissection in 33%. Transesophageal echocardiography correctly identified involvement of the coronary arteries by aortic dissection in six of seven patients as well as absence of both left and right coronary artery involvement in 10 patients with aortic dissection. This technique was also useful in detecting communications between the true and false lumens, presence of thrombi in the false lumen, and, in two patients, localized dissection rupture with formation of a false aneurysm. In both groups 1 and 2, transesophageal echocardiography correctly identified patients with moderate to severe aortic regurgitation. CONCLUSIONS: Transesophageal echocardiography is very useful in the assessment of aortic dissection.

Aortic Dissection↗
PubMed1990

Axial flow velocity patterns in a pulmonary artery model with varying degrees of valvular pulmonic stenosis: pulsatile in vitro studies.

With the advent of noninvasive clinical techniques which can measure blood flow velocities (Doppler ultrasound), it is suggested that a fundamental knowledge of the axial flow velocity patterns in the pulmonary artery, and the changes caused by stenosis, may be used to support accurate diagnosis of valvular pulmonic stenosis. The present study was designed to characterize the axial flow velocity patterns in an in vitro model of a human adult pulmonary artery with varying degrees of valvular pulmonic stenosis. A two-dimensional laser Doppler anemometer (LDA) system was used to map the flow fields in the main (MPA), left (LPA), and right (RPA) branches of the pulmonary artery model. The study was conducted in the Georgia Tech. right heart pulse duplicator system. It was observed that the axial flow velocity patterns in the MPA and the LPA change dramatically with increasing degree of valvular stenosis. This indicates that the axial flow velocity patterns in these two branches are strongly influenced by the degree of valvular stenosis. The axial flow velocity patterns in the RPA, however, do not change much with varying degrees of valvular stenosis, indicating that the axial flow fields in the RPA are mainly influenced by the geometry of the bifurcation. It may be concluded therefore, that the changes in the axial flow velocity patterns in the MPA and LPA (rather than in the RPA) could be sensitive and reliable indicators of the severity of the defect.

Adult↗
PubMed1990

Assessment of aortic regurgitation by noninvasive techniques.

Detection and assessment of severity of aortic regurgitation by pulsed and continuous-wave Doppler techniques requires a lengthy period of examination and a high degree of expertise to approximate the sensitivity and specificity of angiography. This is a major limitation of this modality. Color Doppler, on the other hand, is less time consuming and more reproducible. However, when color Doppler is not available, conventional Doppler in the hands of an expert operator is useful for accurate detection and semiquantitation of aortic regurgitation. Also, it should be noted that color Doppler is not precise in estimation of the severity of aortic regurgitation. Color flow mapping of aortic regurgitation still remains a semiquantitative method. Thus conventional Doppler may need to be used to supplement the color Doppler examination, especially in the assessment of severity of aortic regurgitation, even when access to color flow mapping is readily available.

Aortic Valve↗
PubMed1990

Transesophageal Doppler color flow mapping assessment of atrial septal defect.

Transesophageal Doppler color flow imaging was performed in 19 adult patients (mean age 35 years) with an atrial septal defect demonstrated by cardiac catheterization or at surgery, or both. The transesophageal study correctly identified and classified 19 of 19 shunts in contrast to 16 of 18 shunts identified by the transthoracic approach. The area of the atrial septal defect was calculated by assuming it to be circular and taking the maximal Doppler color flow jet width at the defect site as its diameter. The pulsed Doppler sample volume was placed parallel to the shunt flow direction at the defect site to obtain the mean velocity and flow duration. From these values, the shunt volume was calculated as a product of the defect area, mean velocity, flow duration and heart rate. The calculated shunt flow volume obtained by transesophageal study showed a good correlation with shunt flow volume (r = 0.91, p less than 0.001) and pulmonary to systemic blood flow ratio (r = 0.84, p less than 0.001) obtained at cardiac catheterization. The size of the defect by transesophageal Doppler color flow mapping correlated fairly well with the size estimated at surgery (r = 0.73, p = 0.004). It is concluded that transesophageal Doppler color flow imaging is useful in the detection and classification of atrial septal defects and in the assessment of shunt volumes.

Adult↗
PubMed1990

Use of the smaller pediatric transesophageal echocardiographic probe in adults.

Transesophageal echocardiography in the adult uses a relatively large diameter probe, which may be poorly tolerated by certain patients. The use of a smaller probe designed for pediatric patients was studied in 50 adults (21 males and 29 females), and concomitant transesophageal echocardiography studies were performed using the regular adult-sized probe in 28 of these patients. The smaller pediatric transesophageal echocardiography probe was easier to pass, better tolerated, caused a smaller heart rate increase (13 +/- 3 vs 20 +/- 4 beats/min, P = 0.0029), and required no sedation in more patients than the adult transducer. The resolution of the two-dimensional and color Doppler images in the mid and near fields of the smaller probe were comparable to the larger probe, as were the maximal area of mitral regurgitation and the ratio of the maximal proximal width of the aortic insufficiency jet to the left ventricular outflow tract diameter in patients with these lesions. However, the image resolution was noticeably inferior to the adult probe in the far field, such as when imaging the distal left ventricle or imaging structures transgastrically. Therefore, the smaller probe designed for pediatric use allows satisfactory near- and mid-field two-dimensional and color Doppler flow imaging in comparison to the adult probe and would be expected to be beneficial in adult patients in whom superior quality imaging of the far-field is not required clinically, those who tolerate poorly the adult probe, relatively high-risk patients in whom no sedation is desirable, and in those patients in whom passage of the larger probe is unsuccessful.

Adolescent↗
PubMed1990

Two-dimensional echocardiography and Doppler color flow mapping in the diagnosis and prognosis of ventricular septal rupture.

Doppler color flow mapping in conjunction with two-dimensional echocardiography was used to evaluate ventricular septal rupture after myocardial infarction (seven anterior and eight inferior) in 15 patients and to correlate these findings with cardiac catheterization and surgical or autopsy data. Ventricular septal rupture was diagnosed by turbulent flow traversing the ventricular septum. The direction and velocity of shunt flow was determined by color M-mode and conventional Doppler methods. In all patients, Doppler color flow mapping correctly defined the site of septal rupture, which occurred at areas of discordant septal wall motion or "hinge points" (six posterior inlet, three anterior inlet, and six apical trabecular septum). Each of three patients with moderate tricuspid regurgitation and three of four patients with right-to-left shunting during diastole died, and all had an elevated right ventricular end-diastolic pressure. Right ventricular wall motion index was significantly higher in the patients who died compared with those who survived (mean +/- SEM; 2.8 +/- 0.2 vs. 2.0 +/- 0.2, p = 0.012), but there was no difference in left ventricular wall motion index. The rupture size measured by Doppler color flow imaging (1.7 +/- 0.1 cm) correlated with the size determined during surgery or autopsy (1.8 +/- 0.2 cm, r = 0.68, p = 0.022) and the pulmonic-to-systemic shunt flow ratio by cardiac catheterization (2.4:1 +/- 0.3, r = 0.74, p = 0.004). Color-guided continuous-wave Doppler estimates of right ventricular systolic pressure (47 +/- 2 mm Hg) correlated with cardiac catheterization measurements (48 +/- 3 mm Hg, r = 0.90, p = 0.0002).(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1990

Echocardiographic evaluation of prosthetic cardiac valves.

Comprehensive echocardiographic examination of patients with prosthetic cardiac valves using M-mode, two-dimensional, conventional, and color Doppler echocardiography represents an invaluable clinical tool in the serial follow-up of these patients. A thorough knowledge of these techniques and their limitations allows accurate assessment and prevention of misdiagnoses.

Echocardiography↗
PubMed1989

Can two-dimensional echocardiography and Doppler color flow mapping identify the need for tricuspid valve repair?

Tricuspid regurgitation severity was assessed preoperatively with Doppler color flow mapping and these assessments were compared with surgical findings in 90 patients undergoing mitral or aortic valve replacement, or both. Group I (n = 52) required tricuspid valve annuloplasty because tricuspid regurgitation was judged intraoperatively to be severe; in Group II (n = 38), tricuspid valve annuloplasty was not performed because tricuspid regurgitation was judged intraoperatively not to be severe. With use of the apical four chamber and parasternal short-axis imaging planes, the severity of tricuspid regurgitation by Doppler color flow mapping was assessed by comparing the maximal area of tricuspid regurgitant signals with the right atrial area taken in the same frame in which the maximal tricuspid regurgitant signals were noted. This ratio was found to be greater than or equal to 34% (mean 50.2 +/- 11.8%) in 50 (96%) of 52 patients in Group I and less than 34% (mean 27.5 +/- 6.9%) in 36 (95%) of 38 patients in Group II (p less than 0.001). The maximal diastolic tricuspid anulus diameter measured with the same two-dimensional imaging planes was greater than or equal to mm/m2 body surface area (mean 26.7 +/- 5.2 mm/m2) in 46 patients (88%) in Group I and less than 21 mm/m2 (mean 17.8 +/- 2.5 mm/m2) in 36 patients (95%) in Group II (p less than 0.001).(ABSTRACT TRUNCATED AT 250 WORDS)

Blood Pressure↗
PubMed1989

Two-dimensional and color Doppler assessment of ventricular septal defect of congenital origin.

Two-dimensional echocardiography and color Doppler examinations were performed in 53 patients with 58 ventricular septal defects (VSD) proven surgically or anatomically. All patients also had angiocardiograms. Two-dimensional echocardiography/color Doppler examination detected all VSDs and correctly categorized the site and extension of VSDs in 50 of 58 (86%). All 40 perimembranous VSDs were diagnosed in the left ventricular outflow tract short-axis plane as an area of discontinuity adjacent to septal tricuspid valve leaflet attachment. Fourteen of 16 VSDs with inlet extension showed initial color flow signals along the septal tricuspid leaflet and along the ventricular septum. Of 23 perimembranous VSDs with outlet extension, 19 had flow signals moving directly toward the right ventricular outflow tract. One perimembranous VSD with trabecular extension showed flow signals directed anterolaterally toward the right ventricular free wall. Eleven of 13 muscular VSDs were similarly categorized correctly by color Doppler as inlet, outlet and trabecular. All 5 doubly committed VSDs were correctly diagnosed as an area of discontinuity adjacent to the pulmonary valve in the short-axis view with flow signals directly moving through VSD into right ventricular outflow and pulmonary artery. Angiography correctly detected all VSDs and correctly classified their site and extension in 45 of 58 (77.5%). It misclassified 8 of 40 perimembranous, 3 of 13 muscular and 2 of 5 doubly committed VSDs. Color Doppler compares favorably with angiocardiography in the detection and localization of VSDs.

Adult↗