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N G Pandian

Publications and source records attributed to N G Pandian.

At least 73 records · Page 4Linked to original sources
PubMed1995

Clinical, echocardiographic, and hemodynamic evidence of cardiac tamponade caused by large pleural effusions.

Large pleural effusions are typically associated with dyspnea and potential respiratory compromise. Experimental evidence suggests that with large effusions, increased intrapleural pressure may be transmitted to the pericardial space, resulting in impaired cardiac filling and reduced stroke volume. We report two cases in which large pleural collections were complicated by hypotension. The effusions were due to an infected right hepatic hydrothorax (Case 1) and a left malignant effusion (Case 2). Echocardiography demonstrated right and left ventricular diastolic collapse, respectively, confirming a diagnosis of cardiac tamponade. Large volume thoracentesis resulted in immediate hemodynamic improvement as demonstrated by a reduction in right ventricular and atrial pressures (Case 1) and echocardiographic resolution of left ventricular diastolic collapse (Case 2). These cases establish that large pleural effusions can cause hemodynamically significant cardiac tamponade. In addition, they illustrate how the demonstration of cardiac compressive physiology can significantly alter the therapeutic approach to large pleural effusions.

Adult↗
PubMed1995

Biplane and multiplane transesophageal echocardiography: methodology and echo-anatomic correlations.

Transesophageal echocardiography (TEE) is one of the most significant developments in cardiology and cardiac imaging in the last decade. While monoplane TEE clearly showed the advantages of imaging from the esophagus, biplane TEE was the next important step forward. The combination of transverse and longitudinal axis images served to provide incremental information about various cardiac pathologies. Multiplane TEE is a further advancement that allows continuous visualization of cardiac anatomy by electronic or manual steering of the ultrasound beam through 180 degrees. The intermediate views obtained by beam steering provides an unlimited perspective of normal and abnormal cardiac anatomy. This ability to view cardiac structures in multiple planes aids the understanding of the spatial arrangement of normal cardiac structures and complex disorders of cardiac anatomy. Multiplane TEE technology also eases the examination by reducing the need for probe manipulation. The ability to obtain multiplane images in a sequential manner lays the foundation for three-dimensional imaging of the heart. Ongoing developments in transducer technology should further strengthen the clinical role of TEE.

Echocardiography, Transesophageal↗
PubMed1995

Volume-rendered three-dimensional dynamic anatomy of the mitral annulus using a transesophageal echocardiographic technique.

Mitral annulus anatomy and dynamics were evaluated in 12 subjects using a three-dimensional transesophageal echocardiographic technique. The mitral annular area, diameters and distance from the left ventricular apex were measured in end-diastole, mid-systole, end-systole and mid-diastole. The mitral annulus had its largest area in end-systole and the smallest area in end-diastole. The shape of the annulus changed during the cardiac cycle with the maximal change occurring in the diameters passing close to the middle of the mitral leaflets. In the vertical plane, the annulus had a shallow ski-slope shape, with the attachment of the anterior leaflet being farthest from the apex. In other words, the highest point of the annulus was situated anteromedially and was visualized in the long axis imaging plane.

Echocardiography, Transesophageal↗
PubMed1994

Determination of cardiac output using acoustic quantification in critically ill patients.

The reliability of automated acoustic quantification (AQ) in yielding real-time left ventricular (LV) area, volume, and ejection fraction has been validated. The purpose of this study was to explore the potential of AQ in providing accurate immediate determination of cardiac output in critically ill patients. A total of 48 patients were studied. One group consisted of 37 critically ill patients with indwelling Swan-Ganz catheters. In these patients, cardiac output by AQ, manual tracing of end-diastolic and end-systolic frames of 2-dimensional images, and thermodilution were measured. AQ was also compared with Doppler calculation of flow through the left and right ventricles in 11 additional patients. Adequate data for calculation of cardiac output with AQ were obtained in 78% of critically ill patients. There was an excellent correlation between AQ and off-line manual analysis for LV volumes (r = 0.94 and 0.91 for end-diastole and end-systole), ejection fraction (r = 0.85), and cardiac output (r = 0.93). AQ also correlated well with Doppler analysis (r = 0.97) and thermodilution technique (r = 0.95) in the determination of cardiac output. However, AQ slightly underestimated thermodilution measurements, with rather wide limits of agreement (-0.3 +/- 1.1 liter/min). There was a similar underestimation of cardiac output with manual analysis when compared with thermodilution. Given the absence of significant differences between AQ and manual analysis, this observation suggests that the bias is related to the echocardiographic determination of stroke volume, and not to errors from the automated border detection. It is concluded that AQ, besides providing information on LV volumes and ejection fraction, also can yield rapid measurements of cardiac output in most patients who are acutely ill.

Acoustics↗
PubMed1994

Simulation of intraoperative visualization of cardiac structures and study of dynamic surgical anatomy with real-time three-dimensional echocardiography.

Most prior efforts of 3-dimensional (3-D) reconstruction of echocardiographic images have focused on quantitation of ventricular size and function. The resulting images have been displayed in the wire mesh format. Recently, a method for 3-D transesophageal echocardiography using a computer-controlled probe that acquires parallel tomographic slices has been described. This technique provides dynamic 3-D volume-rendered images of the heart. This study was designed to determine if surgical visualization of intracardiac anatomy could be simulated using this imaging system. Data acquired from 8 patients with congenital and acquired heart disease were analyzed. Real-time 3-D images of the cardiac chambers and valves were obtained. Images of the cardiac pathology including fibrocalcific nodules on the aortic valve, mitral valve endocarditis, rheumatic mitral stenosis, and an ostium secundum atrial septal defect were displayed in 3 dimensions that simulated surgical exposure of these structures. These 3-D representations of cardiac anatomy were in some ways superior to standard intraoperative visualization in that they demonstrated the heart as a dynamic structure, as opposed to the empty, nonbeating heart observed while on cardiopulmonary bypass. In conclusion, 3-D images of cardiac structures as seen by the surgeon intraoperatively can be provided using a computer-driven tomographic transesophageal echocardiographic probe. This imaging system can be potentially useful in the planning and evaluation of cardiac surgery. Technical improvements such as 3-D representation of flow jets, the ability to manipulate images to simulate cardiac surgery, and on-line reconstruction can make this a powerful tool in the future.

Computer Simulation↗
PubMed1994

Clinical usefulness of multiplane transesophageal echocardiography: comparison to biplanar imaging.

The increased diagnostic usefulness of multiplane over biplane transesophageal echocardiography has not yet been conclusively determined. In this study the diagnostic yield of multiplanar and biplanar imaging was compared blindly by using the information content obtained from multiplane transesophageal echocardiography to that derived from biplanar type of imaging planes available in the multiplane echocardiography recordings in 80 patients with a variety of cardiac disorders. Among these patients 9 new abnormalities were identified by multiplane transesophageal echocardiography in 8 patients. Multiplane imaging yielded better delineation of 40 various lesions in 31 patients. Thus multiplane transesophageal echocardiography has a greater diagnostic yield than biplane imaging by depicting more lesions in 10% of patients and by enhanced delineation of the extent of pathologic characteristics in 39% of patients. This versatility, coupled with the ease of obtaining a vast assembly of imaging planes without undue probe manipulations, makes multiplane transesophageal echocardiography more useful than biplanar imaging.

Echocardiography↗
PubMed1994

Potential applications of intracardiac echocardiography in interventional electrophysiology.

The growth of interventional electrophysiology in recent years has placed a greater demand on imaging guidance. Currently available imaging modalities to guide interventions, while useful, have significant limitations. Intracardiac echocardiography has the potential to improve on these limitations and evolve into a modality that could provide imaging guidance, aid in the prevention or instant identification of complications, help identify and quantify ablative lesions, and contribute toward visualization of normal and abnormal conduction pathways. Ongoing developments in catheter design in the form of lower frequency, smaller size, and preshaped catheters should enhance the role of intracardiac echocardiography in interventional electrophysiology. There is the potential to combine the imaging and ablative capabilities of intracardiac ultrasonography to make for an imaging and therapeutic tool.

Cardiac Catheterization↗
PubMed1994

Diagnosis of cardiac tamponade after cardiac surgery: relative value of clinical, echocardiographic, and hemodynamic signs.

Early detection and treatment of cardiac tamponade is crucial in management of patients after cardiac surgery. Because of the atypical features of this condition and paucity of data on relative frequency of different signs, we evaluated the sensitivity of various clinical, echocardiographic, and hemodynamic signs. We retrospectively evaluated the relative frequency of clinical, echocardiographic, and hemodynamic signs in 29 patients with cardiac tamponade after cardiac surgery. In our study 66% had a localized, posterior pericardial effusion, and the other 34% had circumferential pericardial effusion. In the whole group 24% of patients had hypotension, and pulsus paradoxus was noted in 48%, right atrial collapse in 34%, right ventricular diastolic collapse in 27%, left ventricular diastolic collapse in 65%, and left atrial collapse in 13%. Elevation with equalization of pressures was noted in 81% patients. In the patient group with circumferential pericardial effusion and cardiac tamponade 40% patients were hypotensive and 50% patients had pulsus paradoxus. RA collapse was present in 70%, RV diastolic collapse in 70%, and LV diastolic collapse in 20%. Elevated diastolic pressures with equalization of these pressures was present in 71%. In the group with regional pericardial effusion and cardiac tamponade hypotension was present in 16% and pulsus paradoxus in 47%. RA collapse was present in 16%, RV diastolic collapse in 5%, LV diastolic collapse in 89%, and LA collapse in 21% of the patients with regional tamponade. Elevated diastolic pressures with equalization of these pressures was noted in 86% of the patients. Our observations indicate that among patients who have undergone cardiac surgery the presentation of cardiac tamponade is usually atypical.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1994

Delineation of extended lengths of coronary arteries by multiplane transesophageal echocardiography.

OBJECTIVES: The purpose of this study was to evaluate the utility of multiplane transesophageal echocardiography in assessing the coronary artery tree. BACKGROUND: Evaluation of coronary disease with single-plane and biplane transesophageal echocardiography is limited to the very proximal vessels. The numerous views provided by multiplane imaging may enhance visualization of coronary arteries and detection of their abnormalities. METHODS: Intraoperative multiplane transesophageal echocardiography was performed in 45 consecutive adults who had recently undergone angiography. Recordings were reviewed in blinded manner. RESULTS: We describe the coronary segments visualized with the different imaging planes and define new views. The left main coronary artery with its bifurcation was visualized in all 45 patients. Sensitivity and specificity for detection of coronary narrowings were 100% when results were compared with angiographic data. Visualization of proximal, mid and distal segments of the left anterior descending coronary artery was possible in 69%, 31% and 16% of patients, respectively. Among patients in whom the proximal segment was visualized, sensitivity and specificity for detection of significant narrowings were 80% and 100%. Proximal, mid and distal portions of the left circumflex coronary artery were visualized in 80%, 51% and 20% of patients. Among patients in whom the proximal portion was well seen, sensitivity and specificity were 89% and 100%. The proximal, mid and distal portions of the right coronary artery were visualized in 84%, 16% and 11% of patients. Among patients in whom the proximal segment was visualized, sensitivity and specificity were 82% and 100%. Color Doppler examination was less useful because it detected only 52% of all patients with proximal stenosis. CONCLUSIONS: Multiplane transesophageal echocardiography allows enhanced visualization of extended lengths of coronary arteries and the reliable identification of coronary artery abnormalities.

Adult↗
PubMed1994

Intravascular ultrasound imaging in peripheral arterial and coronary artery disease.

Intravascular ultrasound is an emerging imaging modality that employs miniaturized transducers at the tips of catheters to provide detailed information about the morphology of small and large arteries. While there is ongoing development in technology, currently available intravascular ultrasound instrumentation already augments angiography in the assessment of structural and dynamic abnormalities of the peripheral and coronary arterial systems. Recent studies have consistently demonstrated significant underestimation of atherosclerotic disease by angiography. Demonstration by intravascular ultrasound of disease in the angiographically normal "reference" segment and of remodeling of the diseased segment may explain this angiographic underestimation. Intravascular ultrasound also has many applications during various catheter-based therapeutic procedures. In addition to contributing to our understanding of the mechanisms of interventions and restenosis, intravascular ultrasound may lead to better guidance and ultimately better outcome during various procedures such as balloon angioplasty, atherectomy, and stent placement.

Arterial Occlusive Diseases↗
PubMed1994

Utility of in vivo, intracardiac two-dimensional echocardiography in the assessment of myocardial risk area and myocardial dyssynergy during coronary occlusion and reperfusion.

We have previously reported the potential use of intracardiac echocardiography (ICE) in a variety of clinical settings, including detection of pericardial effusion, intracardiac masses, congenital cardiac defects, and during simulated balloon valvuloplasty. The utility of intracardiac ultrasound imaging of the left ventricle (LV) in patients with coronary disease needs to be further explored. We performed this study with the purpose of evaluating risk area and regional wall-motion abnormalities produced by ischemia using ICE. Ten episodes of ischemia were produced by transiently occluding the left anterior descending coronary artery in five dogs. ICE was performed with a modified 5-MHz transesophageal echocardiographic probe placed in the right atrium. Continuous short-axis images of the LV were obtained before, during, and after coronary occlusion. Risk area was defined using myocardial contrast echocardiography. In all cases, ICE provided high resolution images of the LV. Risk area and regional wall-motion abnormalities were readily detected. There was good correlation between the risk area (x) and extent of dyssynergy (y), defined by the equation y = 0.76x + 6.38 (r = 0.80, P less than 0.01). We conclude that ICE provides potentially useful information concerning regional LV dysfunction, and, when combined with myocardial contrast echocardiography, area at risk. This technique may be useful during interventional procedures once a catheter-based ultrasound transducer with adequate depth of field to provide images of the entire LV can be developed.

Animals↗
PubMed1994

Dynamic three-dimensional echocardiographic imaging of congenital heart defects in infants and children by computer-controlled tomographic parallel slicing using a single integrated ultrasound instrument.

Three-dimensional cardiac reconstruction generated from transesophageal interrogation can be performed using an integrated unit that captures, processes, and postprocesses tomographic parallel slices of the heart. This probe was used for infants and young children in the transthoracic position to evaluate the feasibility of producing three-dimensional cardiac images with capability for real-time dynamic display. Twenty-two infants and children (range 1 day-3.5 years) underwent image acquisition using a 16 mm 5 MHz 64 element probe placed over the precordium. Two infants were also imaged from the subcostal position. Data was obtained and stored over a single cardiac cycle after acceptable cardiac and respiratory gating intervals were met. The transducer was advanced in 0.5-1 mm increments over the cardiac structures using identical acquisition criteria. The images were reconstructed from the stored digital cubic format and could be oriented in any desired plane. In 9 of the 22 infants the images obtained were of optimal quality. The images obtained displayed normal cardiac structures emphasizing depth relationships as well as visualization of planes not generally demonstrated by two-dimensional imaging. Several lesions were also depicted in a unique fashion using this technique. Though the method employed was limited by movement artifact and reconstruction time, the quality of the three-dimensional display was excellent and enhanced by real-time demonstration. The transthoracic approach was successful in capturing sufficient data to create three-dimensional images, which may have further application in more accurate diagnosis of complex cardiac abnormalities and generation of planes of view which could duplicate surgical visualization of a lesion. Further assessment of the technique in infants with congenital heart disease is warranted.

Child, Preschool↗
PubMed1994

Enhanced comprehension of dynamic cardiovascular anatomy by three-dimensional echocardiography with the use of mixed shading techniques.

Advances in ultrasound instrumentation and computer technology provide us an opportunity to develop methods to perform three-dimensional echocardiography in patients. Optimal methods of displaying three-dimensional images are critical for the perception of depth and distances. We examined the utility of various shading techniques in volume-rendered three-dimensional images in 22 patients with a variety of cardiac defects. Distance coding, gray level gradient shading, texture shading, and mixtures of these shading techniques were used. Our observations suggest that the mixture of shading techniques portray the dynamic three-dimensional anatomy better than a single type of shading. Appropriate mix of shadings could provide dynamic three-dimensional echocardiograms of clinical utility.

Echocardiography↗
PubMed1994

Predicting recovery of severe regional ventricular dysfunction. Comparison of resting scintigraphy with 201Tl and 99mTc-sestamibi.

BACKGROUND: Regional 201Tl activity after resting injection, imaged early and after redistribution, reflects viable myocardium and can predict improved isotope uptake as well as regional and global ventricular function after revascularization. 99mTc-sestamibi, a perfusion tracer with favorable imaging characteristics, has distinct kinetics compared with 201Tl, demonstrating minimal redistribution; this property may give 201Tl an advantage for detecting viable myocardium, particularly in segments with resting hypoperfusion. The purpose of this study was to compare regional activities of 201Tl and 99mTc-sestamibi after resting injections in patients with coronary artery disease and regional or global left ventricular dysfunction and to assess their comparative abilities for predicting recovery of severe regional ventricular dysfunction after revascularization. METHODS AND RESULTS: Qualitative and quantitative comparisons of rest and redistribution 201Tl activity and sestamibi activity 1 hour after rest injection were performed in 31 patients with coronary artery disease and left ventricular dysfunction. Quantitative analysis of three short-axis tomograms per patient was performed by use of circumferential profiles that allowed analysis of 12 segments per patient. Two-dimensional echocardiography was used to assess wall motion and thickening in segments corresponding to the single photon emission computed tomography data. Concordance between regional 201Tl activity at redistribution imaging and regional sestamibi activity by semiquantitative visual analysis demonstrated concordant regional activity in 87% of segments; among discordant segments, no significant skew was seen, indicating enhanced uptake of one agent over the other. Quantitative analysis for all segments showed significant correlation (r = .86, P < .001) between quantitative regional 201Tl redistribution activity and 1-hour post-rest injection sestamibi activity in individual segments. Eighteen of these patients were revascularized, and echocardiography was repeated 20 +/- 16 days later; segments exhibiting significant regional ventricular dysfunction before revascularization were classified as having reversible or irreversible dysfunction on the basis of the change in wall motion and thickening. 201Tl and sestamibi regional activities were similar in those segments with reversible (72 +/- 11% [percent of peak activity] versus 75 +/- 9%, respectively, P = NS) as well as irreversible ventricular dysfunction (51 +/- 11% versus 50 +/- 8%, P = NS). Positive (75% versus 80% for 201Tl and sestamibi, respectively) and negative (92% versus 96%, respectively) predictive values for recovery of regional ventricular dysfunction after revascularization were similar for the two agents. CONCLUSIONS: In patients with coronary artery disease and left ventricular dysfunction, quantified sestamibi activity 1 hour after rest injection parallels redistribution 201Tl activity after a resting injection, suggesting that uptake and subsequent handling of sestamibi are more complex than can be explained by a pure flow tracer with no redistribution. Quantitative analysis of regional activities of both 201Tl and sestamibi after resting injections can differentiate viable from nonviable myocardium, and the two agents comparably predict reversibility of significant regional wall motion abnormalities after revascularization in such patients to a similar degree.

Adult↗
PubMed1994

Three-dimensional reconstruction of intracoronary ultrasound images. Rationale, approaches, problems, and directions.

Although intracoronary ultrasonography allows detailed tomographic imaging of the arterial wall, it fails to provide data on the structural architecture and longitudinal extent of arterial disease. This information is essential for decision making during therapeutic interventions. Three-dimensional reconstruction techniques offer visualization of the complex longitudinal architecture of atherosclerotic plaques in composite display. Progress in computer hardware and software technology have shortened the reconstruction process and reduced operator interaction considerably, generating three-dimensional images with delineation of mural anatomy and pathology. The indications for intravascular ultrasonography will grow as the technique offers the unique capability of providing ultrasonic histology of the arterial wall, and the need for a three-dimensional display format for comprehensive analysis is increasingly recognized. Consequently, three-dimensional imaging is being rapidly implemented in the catheterization laboratories for guidance of intracoronary interventions and detailed assessment of their results. However exciting the prospects may be, three-dimensional reconstructions at present remain partially artificial because the true spatial position of the imaging catheter tip is not recorded, and shifts in its location and curves of the arterial lumen result in pseudoreconstructions rather than true reconstructions. In this report, we address the principles of three-dimensional reconstruction with a critical review of its limitations. Potential solutions for refinement of this exciting imaging modality are presented.

Algorithms↗
PubMed1994

Three-dimensional volumetric ultrasound imaging of arterial pathology from two-dimensional intravascular ultrasound: an in vitro study.

The objectives of this study were to evaluate: (1) the feasibility of generating three-dimensional (3-D) ultrasound (US) volumetric images of arterial segments from intravascular (IV) US images by retaining full range of gray levels; (2) the feasibility of volumetric quantitation of various arterial wall pathology from the 3-D volume US images of arterial segments. IVUS provides morphologic details of arterial wall diseases. This is seen as variation in gray levels. However, when a 3-D US image is generated currently, the full range of gray levels is not utilized. This limits optimal assessment of arterial wall pathology. Sequential cross-sectional IVUS images from 11 arterial segments consisting of various pathology were obtained in vitro by calibrated withdrawal of an IVUS catheter. These images were digitized by an 8 bit digitizer to retain full 256 gray levels of brightness. 3-D volume generation was carried out using "ANALYZE" software. After the IVUS imaging, arterial segments were sectioned transversely in a 0.3-0.4 mm cross section and stained with hematoxylin, eosin and elastin. Geometrical measurements and gross morphological changes of the arterial segments were noted and correlated with the corresponding section of the image from the three-dimensional volume. Arterial wall pathology, its extent and its effect on lumen geometry were easily appreciated in multiple tomographic sections of a 3-D volume image. Similarly, arterial wall pathology was easily quantitated from 3-D volume. The above assessments were only feasible by retaining full range of gray levels in the 3-D volume image. This study indicates that (1) it is feasible to generate a 3-D US volume image by retaining full range of gray levels from IVUS images, (2) retaining full range of gray levels allows optimal assessment of arterial wall pathology and its extent in 3-D volume, and (3) IVUS allows quantitation of arterial wall pathology, and thereby one can assess the effect of intervention.

Arteries↗