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Biomedical subjects

N G Pandian

Publications and source records attributed to N G Pandian.

At least 55 records · Page 3Linked to original sources
PubMed1997

Direct measurement of three-dimensionally reconstructed flow convergence surface area and regurgitant flow in aortic regurgitation: in vitro and chronic animal model studies.

BACKGROUND: Evaluation of flow convergence (FC) with two-dimensional (2D) imaging systems may not be sufficiently accurate to characterize these often asymmetric, complex phenomena. The aim of this study was to validate a three-dimensional (3D) method for determining the severity of aortic regurgitation (AR) in an experimental animal model. METHODS AND RESULTS: In six sheep with surgically induced chronic AR, 20 hemodynamically different states were studied. Instantaneous regurgitant flow rates were obtained by aortic and pulmonary electromagnetic flow meters. Video composite data of color Doppler flow mapping images were transferred into a TomTec computer after computer-controlled 180 degrees rotational acquisition. Direct measurement of the 3D reconstructed FC surface areas as well as measurements of FC areas estimated with 2D methods with hemispherical and hemielliptical assumptions were performed, and values were multiplied by the aliasing velocity to obtain peak regurgitant flow rates. There was better agreement between 3D and electromagnetically derived flow rates than there was between the 2D and the reference values (r=.94, y=1.0x-0.16, difference=0.02 L/min for the 3D method; r=.80, y=1.6x-0.3, difference=1.2 L/min for the 2D hemispherical method; r=.75, y=0.90x+0.2, difference=-0.20 L/min for the 2D hemielliptical method). CONCLUSIONS: Without any geometrical assumption, the 3D method provided better delineation of the FC zones and direct measurements of FC surface areas, permitting more accurate quantification of the severity of AR than the 2D methods.

Animals↗
PubMed1997

Role of transthoracic and transesophageal echocardiography in predicting embolic events in patients with active infective endocarditis involving native cardiac valves.

Some studies describe an increased risk for emboli in infective endocarditis patients with large (>10 mm) and mobile vegetations. Other studies fail to demonstrate the above relation. Most studies have been performed using transthoracic echocardiography or with a monoplane transesophageal approach. The present study examines whether distinctive characteristics of vegetative lesions detected by transthoracic and multiplane transesophageal echocardiography are predictive of embolic risk. We reviewed both transthoracic and transesophageal echocardiograms of 57 patients with diagnosis of acute infective endocarditis and no documented or suspected previous embolic events. We evaluated site, length, width, mobility, and echodensity of vegetations. Twenty-five patients (44%) had embolic events. No statistical differences in age, sex distribution, location of endocarditis, or offending pathogens between embolic (n = 25) and nonembolic (n = 32) patients were found. There were no differences in any of the echo characteristics of vegetations detected by transthoracic and transesophageal approach in embolic and nonembolic groups. Thus, transthoracic and transesophageal characteristics of vegetations are not helpful in defining embolic risk in patients with infective endocarditis.

Adult↗
PubMed1997

Two- and three-dimensional transesophageal echocardiography in patient selection and assessment of atrial septal defect closure by the new DAS-Angel Wings device: initial clinical experience.

BACKGROUND: Transcatheter closure of atrial septal defects (ASDs) has been feasible and successful. Two-dimensional echocardiography (2DE) was applied to patients before selection and during device deployment. Three-dimensional echocardiography (3DE) can provide unique anatomic perspectives that might aid in improving device closure of ASDs. METHODS AND RESULTS: Twenty-two consecutive patients were enrolled in an initial protocol for ASD device closure by the new DAS-Angel Wings occluder device. On the basis of transesophageal (TEE) 2DE and 3DE, 13 patients were considered eligible for device closure (9 secundum ASDs and 4 with patent foramen ovale associated with a cerebral vascular accident). Maximal ASD diameter and surrounding rim tissues were compared by TEE 2DE and 3DE and with balloon sizing measurements at catheterization. ASD size measured by TEE 2DE and 3DE correlated well (y = 1.0x + 0.049, r = .95), with good limits of agreement. However, balloon-stretched diameter measurements were systematically larger than echocardiographic measurements. Rim tissue measurements correlated well; however, TEE 3DE could demonstrate the entire shape and perimeter of the defect. Two-dimensional imaging provided reliable information during device deployment and for closure of small ASDs. However, 3DE was superior for imaging the device, especially when abnormally placed. CONCLUSIONS: Three-dimensional imaging provides unique images and projections that were essential for understanding the spatial relationship of the device to the atrial septum. Three-dimensional echocardiography significantly enhanced our understanding of two-dimensional images and provided an imaging conceptualization that should aid in future development of device closures.

Echocardiography↗
PubMed1997

Three-dimensional echocardiographic estimation of infarct mass based on quantification of dysfunctional left ventricular mass.

BACKGROUND: Two-dimensional echocardiography is useful for estimating the extent of infarct-related wall motion abnormalities. Such estimation, however, is based on a few selected views and extrapolated for the whole left ventricle (LV). This approach does not provide us with the actual amount of dysfunctional myocardium. Volume-rendered three-dimensional echocardiography (3DE) might overcome these limitations. In this study we explored (1) how well volume-rendered 3DE delineates regional dysfunction of the infarcted LV and (2) how well dysfunctional myocardial mass quantified by 3DE reflects the actual anatomic infarct mass. METHODS AND RESULTS: 3DE was performed before and 3 hours after coronary occlusion in 16 dogs. With the LV viewed in equidistant short-axis slices, the region of dysfunction was demarcated, and the dysfunctional myocardial mass was derived from this. With triphenyltetrazolium chloride staining, anatomic infarct regions were delineated, dissected, and weighed. The anatomic infarct mass was 16.3+/-7.7 g (mean+/-SD) (range, 6.4 to 31.4 g); the dysfunctional mass estimated by 3DE was 17.4+/-9.1 g (range, 5.2 to 39.0 g). The mean difference was 1.0 g. The correlation between dysfunctional mass (y) and infarct mass (x) was y=l.lx-0.6, r=.93 (P<.0001). The percentage of LV involved in infarction was 18.2+/-5.8% (range, 9.1% to 26.1%); the percentage of LV involved in regional dysfunction was 18.3+/-6.9% (range, 7.9% to 31.2%). The mean difference was 0.1%. The correlation between percentage of LV involved in infarction (x) and percentage of LV involved in dysfunction (y) was y=1.0x-1.1, r=.92 (P<.0001). CONCLUSIONS: Volume-rendered 3DE crisply displays regional dysfunction of infarcted LV. 3DE-measured dysfunctional mass accurately reflects the anatomic infarct mass.

Animals↗
PubMed1997

Valvular perforation in left-sided infective endocarditis: a prospective echocardiographic evaluation and clinical outcome.

We undertook this study to determine the use of transthoracic and transesophageal echocardiography in detecting valvular perforation and the clinical impact of the latter on the outcome of left-sided infective endocarditis. Transthoracic echocardiography was performed in 58 consecutive patients with infective endocarditis. According to the study protocol, a subgroup of 42 patients also underwent transesophageal echocardiogrophy. At referral, 20 (34%) of 58 patients had echocardiographic evidence of valvular perforation (group A). No valvular perforations were found in the remaining 38 patients (group B). During a follow-up period of 27 +/- 16 months, a major complication occurred in 18 of 20 patients in group A and in 11 of 38 patients in group B (p < 0.0001). Univariate analysis indicated previous infective endocarditis, aortic involvement, and New York Heart Association functional class had a predictive value for valvular perforation (p < 0.001). Stepwise regression analysis confirmed aortic valve perforation as the only independent predictive variable for surgery and death. Valvular perforation is a common complication of infective endocarditis and is associated with an adverse outcome. Transthoracic echocardiography can detect or suggest valvular perforation in infective endocarditis, but transesophageal echocardiography better defines this complication and predicts severe heart failure or the need for early surgical management.

Adult↗
PubMed1997

Calculation of aortic regurgitant volume by a new digital Doppler color flow mapping method: an animal study with quantified chronic aortic regurgitation.

OBJECTIVES: The aim of the present study was to quantitate aortic regurgitant volume and regurgitant fraction in a chronic animal model with surgically created aortic regurgitation using a new semiautomated color Doppler flow calculation method. BACKGROUND: The conventional noninvasive methods for evaluating the severity of aortic regurgitation have not been accepted widely nor compared with truly quantitative reference standards. METHODS: Eight to 20 weeks after aortic regurgitation was surgically induced in six sheep, a total of 22 hemodynamic states were studied. Electromagnetic flow probes and meters provided reference flow data. Epicardial color Doppler echocardiographic studies were performed to image left ventricular outflow tract forward and aortic regurgitant blood flows. The new method digitally integrated spatial and temporal color flow velocity data for left ventricular outflow tract forward flow and ascending aortic regurgitant flow. The pulsed Doppler method using the velocity-time integral was also used to obtain regurgitant volumes and regurgitant fractions. RESULTS: Regurgitant volumes and regurgitant fractions by the new method agreed well with those obtained electromagnetically, whereas the pulsed Doppler method overestimated these reference data (mean [+/-SD] difference 0.23 +/- 2.9 ml vs. 11 +/- 5.8 ml, p < 0.0001 for regurgitant volume; mean difference 1.2 +/- 7.6% vs. 19 +/- 13%, p < 0.0001 for regurgitant fraction). CONCLUSIONS: This animal study, using strictly quantified aortic regurgitant volumes, demonstrated that the digital color Doppler method provides accurate aortic regurgitant volumes and regurgitant fractions without cumbersome measurements.

Animals↗
PubMed1997

Three-dimensional echocardiographic evaluation of aortic disorders with rotational multiplanar imaging: experimental and clinical studies.

Transesophageal echocardiography has become a highly valuable method to assess aortic disorders. With this method, however, aortic disease has been visualized only in two-dimensional views. Advances in computer technology have introduced three-dimensional (3D) echocardiography as a developing modality in cardiac imaging. Previous efforts to obtain 3D reconstructions of the aorta, by various techniques, had limited clinical applicability. In this study we attempted to explore the feasibility and potential of 3D reconstructions of the aorta employing a widely used multiplane transesophageal imaging technique in an experimental setting and in patients. In the in vitro study, we created 35 lesions in 28 pig aortic trees (15 aortic dissections, five saccular aneurysms, five coarctations, five atheromas, and five clots within dissections). Suspending these specimens in a water bath, sequential two-dimensional images were acquired over a 180-degree rotation with a commercially available multiplane transesophageal probe and ultrasound system with a 3D software package. Data processing (digital reformation, interpolation, and segmentation) and 3D display were accomplished on an off-line computer system. 3D reconstructions were achieved and displayed in wire-frame, surface-rendered, and volume-rendered images. These 3D reconstructions corresponded well with the actual anatomic specimens in delineating the various pathologic findings. In patient studies, we collected a total of 36 studies in both adults and children with a mean age of 44.5 years (range 1 month to 82 years). In addition to normal aortas (n = 13), the spectrum of abnormalities studied included six atheromatous lesions, four aortic dissections, 10 coarctations, one aneurysm with a thrombus, and one dilated aortic root. We were able to accomplish volume-rendered 3D images depicting the aortic lesions in their true form that could be viewed in many different perspectives in all patients. We conclude that 3D echocardiography is able to display the aorta and aortic disease in a realistic manner. Although this modality still has limitations, further improvements in computer and ultrasound technology would strengthen 3D echocardiography as a clinically viable diagnostic tool, in the evaluation of aortic disorders.

Adolescent↗
PubMed1997

Ruptured sinus of Valsalva aneurysm simulating endocarditis.

A previously healthy, 31-year-old man was evaluated in the emergency department after being violently assaulted. A harsh, continuous murmur was noted on physical examination. Transthoracic and transesophageal echocardiograms were interpreted as showing a ruptured sinus of Valsalva aneurysm with a shunt into the right atrium and a tricuspid valve vegetation. The patient was treated with antibiotics for presumed endocarditis. Subsequent echocardiographic and surgical evaluation showed no evidence of past or present endocarditis. Rather, the sinus of Valsalva aneurysm and rupture gave the appearance of a valvular mass. This report shows some of the potential pitfalls in the delineation of abnormalities related to sinus of Valsalva aneurysms and rupture.

Adult↗
PubMed1996

Automatic backscatter analysis of regional left ventricular systolic function using color kinesis.

Assessment of regional wall motion by 2-dimensional echocardiography can be performed by either semiquantitative wall motion scoring or by quantitative analysis. The former is subjective and requires expertise. Quantitative methods are too time-consuming for routine use in a busy clinical laboratory. Color kinesis is a new algorithm utilizing acoustic backscatter analysis. It provides a color encoded map of endocardial motion in real time. In each frame a new color layer is added; the thickness of the color beam represents endocardial motion during that frame. The end-systolic image has multiple color layers, representing regional and temporal heterogeneity of segmental motion. The purpose of this study was to validate the use of color kinesis for semiquantitative analysis of regional left ventricular systolic function and quantitatively in measurement of endocardial excursion. Semiquantitative wall motion scoring was performed in 18 patients using both 2-dimensional echo and color kinesis. Scoring was identical in 74% of segments; there was 84% agreement in definition of normal vs. abnormal. There was less interobserver variability in wall motion scoring using color kinesis. Endocardial excursion was quantified in 21 patients. 70% of the imaged segments were suitable for analysis. Correlation between 2-dimensional echocardiographic measurements and color kinesis was excellent, r = 0.87. The mean difference in excursion as measured by the 2 methods was -0.05 +/- 2.0 mm. In conclusion, color kinesis is a useful method for assessing regional contraction by displaying a color map of systolic endocardial excursion. This algorithm may improve the confidence and accuracy of assessment of segmental ventricular function by echocardiographic methods.

Adult↗
PubMed1996

Volume-rendered, three-dimensional echocardiographic determination of the size, shape, and position of atrial septal defects: validation in an in vitro model.

Accurate evaluation of atrial septal defect (ASD) size and shape is very important for the selection of patients for transcatheter occlusion. The ability of volume-rendered, three-dimensional echocardiography (3DE) in displaying ASDs in a dynamic mode has been demonstrated; however, its accuracy in sizing ASDs is unknown. To assess this, we performed 3DE of 10 explanted pig hearts in which ASDs of various locations, sizes, and shapes had been experimentally created. From en face 3DE views of the atrial septum containing the defects, major and minor diameters of the defect were measured by a blinded observer, and these data were compared to direct anatomic measurements. The correlations between 3DE and anatomy for the major and minor ASD diameters were y = 0.83x + 3.4 (r = 0.97, p < 0.0001) and y = 0.92x + 1.3 (r = 0.92, p < 0.0001) respectively. The correlation between the measures for major and minor axis ratio was y = 1.06 x - 0.052, r = 0.91, p < 0.0002. Good agreement between both methods of measurements was demonstrated for all measurements. In addition, 3DE portrayed the location and shape of the defects accurately. Thus 3DE provides excellent visualization of ASD and is able to accurately define the size of the defects. These qualitative and quantitative capabilities enhance the clinical potential of this technique in the appraisal of ASDs for decisions regarding application of closure devices.

Animals↗
PubMed1995

Dynamic three-dimensional echocardiographic assessment of intracardiac blood flow jets.

Transthoracic dynamic 3-dimensional reconstruction of the heart with tissue depiction has been proved to be feasible when using various methods of data acquisition. The same method can theoretically be applied to color Doppler flows to generate dynamic 3-dimensional images of intracardiac blood flow jets. To explore the feasibility of this approach, we studied 41 patients with various valvular disorders or intracardiac shunts. We acquired sequential 2-dimensional images along with color Doppler information using rotational scanning from a transthoracic or a subcostal window. Images were digitized and processed for 3-dimensional reconstruction using dedicated software. After adequate segmentation, the flow jets were displayed in 3 dimensions in a gray scale format. With use of this approach, 3-dimensional reconstruction of color Doppler flows was possible in all but 1 patient. Still frames allowed immediate appreciation of the shape of the jets, their location in the cardiac chambers, and their size related to that cavity. Dynamic display was even more striking by showing the flow in real time. Dynamic 3-dimensional images enabled visualization of flow jets in projections not available in conventional color flow Doppler, looking directly at the views of shunt and regurgitant flows, and also permitted 3-dimensional delineation of flow convergence zones. We conclude that dynamic visualization of various intracardiac flows in 3 dimensions using transthoracic echocardiography is possible. It provides a better understanding of the shape and size of the jets, and can potentially aid in flow quantification by displaying the actual shape of flow convergence regions.

Adolescent↗
PubMed1995

Effects of variations in flow on aortic valve area in aortic stenosis based on in vivo planimetry of aortic valve area by multiplane transesophageal echocardiography.

This study provides evidence that acute changes in stroke volume and cardiac output do not result in significant alterations in the anatomic AVA measured with multiplane TEE in patients with AS of moderate or severe degree. Thus, TEE could be useful in the assessment of severity of AS in both low- and high-output states.

Adult↗
PubMed1995

Intracardiac echocardiography without fluoroscopy: potential of a balloon-tipped, flow-directed ultrasound catheter.

Intracardiac echocardiography is a technique that uses catheter-based ultrasound transducers placed within the heart to image cardiac structures. One disadvantage to this technique is that it requires fluoroscopy for catheter placement. This study was performed to evaluate a prototype balloon-tipped, flow-directed catheter for use during intracardiac echocardiography in seven dogs. With the balloon deflated, the catheter could not be successfully advanced without fluoroscopy. Even with fluoroscopic imaging, catheter advancement was often difficult. With the balloon inflated, it could easily be passed into the pulmonary artery without fluoroscopy in 12 of 14 attempts. Images of the cardiac chambers, valves, and pulmonary artery could be obtained. In conclusion, use of a balloon-tipped, flow-directed catheter for intracardiac echocardiography and pulmonary artery imaging can be performed without the use of fluoroscopy. With continued refinements, such as enhancement of the visual field, intracardiac echocardiography could possibly be performed at the bedside to assess cardiac function or assist with interventional procedures.

Animal Population Groups↗
PubMed1995

Delineation of site, relative size and dynamic geometry of atrial septal defects by real-time three-dimensional echocardiography.

OBJECTIVES: This study attempted to determine the site, relative size and dynamic geometry of atrial septal defects using dynamic three-dimensional echocardiography. BACKGROUND: Recent studies have demonstrated the feasibility of dynamic three-dimensional echocardiography. Images are acquired from computerized reconstruction of sequential, tomographic ultrasound "slices" of the heart. Ultrasound images can be obtained by linear progression of a transducer within a transesophageal imaging probe. In small infants and children the large transducer size has not allowed transesophageal placement, and the probe has been placed on the thorax or in the subcostal position. Other scanning devices, housed in plastic containers, acquire images in a rotational format and can also be placed in a transthoracic or subcostal position. METHODS: Specially designed transesophageal probes and a dedicated computer unit were used for two-dimensional image retrieval and reconstruction of three-dimensional images. Sixteen patients with atrial septal defects were studied (median age 18 months, range 1 day to 18 years). In one patient, images were obtained by transesophageal probe placement; in the other 15 patients, the probe was placed in the transthoracic or subcostal position. RESULTS: A dynamic three-dimensional echocardiogram of the atrial septal defect could be obtained in 13 of the 16 patients. The distinguishing features of the atrial septal defects and their spatial orientation could be visualized in unique three-dimensional views. CONCLUSIONS: Dynamic three-dimensional imaging could be applied to the specific evaluation of atrial septal defects. Unique views of the heart allowed for spatial comprehension of the defects, rendering potentially important clinical information.

Echocardiography, Transesophageal↗
PubMed1995

Transthoracic real-time three-dimensional echocardiography using a fan-like scanning approach for data acquisition: methods, strengths, problems, and initial clinical experience.

Three-dimensional echocardiography is an emerging clinical method to assess cardiovascular disorders. The feasibility of using a linear mode scanning (parallel slicing) for transthoracic data acquisition has been demonstrated. In this study, we evaluated the feasibility of real-time transthoracic three-dimensional imaging of the heart using a fan-like scanning mode of echocardiographic data acquisition. We used a computer-driven motor to sequentially angulate transthoracic transducers over a fan-like arc up to 90 degrees. With careful ECG and respiratory gating, we acquired basic two-dimensional data set via parasternal and subcostal windows and performed dynamic three-dimensional reconstructions. The problems encountered included the need to repeat data acquisition sequences because of transducer movement or inappropriate gain and gray scale settings. From 15 scanning sequences in four patients, we were able to use ten sets of data. These yielded good quality three-dimensional studies projecting normal valves, a stenotic mitral valve, and an atrial septal defect, in a number of novel views. The valves could be visualized from above and from below as well as in other orientations, and the detailed anatomy appraised. Spatial relationships of the atrial septal defect with inferior and superior vena cava, coronary sinus, or tricuspid annulus could be uniquely displayed through views from the right side of the heart. This technique provided adequate new imaging planes not available from two-dimensional echocardiography. This experience demonstrates for the first time that transthoracic three-dimensional echocardiography using a fan-like scanning mode of data acquisition is feasible, and that it provides adequate visualization of intracardiac structures in unique projections.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗