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Biomedical subjects

N G Pandian

Publications and source records attributed to N G Pandian.

At least 19 recordsLinked to original sources
PubMed2006

Low levels of high-density lipoprotein cholesterol are associated with vascular remodeling in cardiac transplant recipients.

BACKGROUND: Early atherosclerosis may be associated with compensatory vessel enlargement, termed positive remodeling. Enlarged brachial artery diameter has been reported in patients with risk factors for atherosclerosis and in individuals with coronary atherosclerosis, indicating that brachial artery enlargement is a marker for the presence of atherosclerotic changes. Cardiac transplant recipients often have abnormal lipid levels, but the effect of specific lipid abnormalities on vascular remodeling in this population has not been evaluated. This study examined the relationship between lipid levels and brachial artery diameter in cardiac transplant recipients. METHODS: Thirty-five stable cardiac transplant recipients underwent high-resolution brachial artery ultrasound to evaluate resting brachial artery diameter. Levels of high-density lipoprotein cholesterol (HDL-C), low-density lipoprotein cholesterol (LDL-C), and triglycerides were determined and the presence of other cardiac risk factors was assessed. RESULTS: Brachial artery diameter was larger (4.3 +/- 0.1 mm) in subjects with low levels of HDL-C (< 40 mg/dL, n = 11) compared to subjects with high HDL-C (> or = 40 mg/dL, n = 24), who had a mean brachial artery diameter of 3.7 +/- 0.1 mm (P = .006). Neither high LDL-C (> or = 100 mg/dL) nor high triglycerides (> or = 200 mg/dL) were associated with differences in brachial artery diameter. Multivariate analysis demonstrated that the relationship between low HDL-C and increased brachial artery diameter was independent of body surface area or statin use. CONCLUSIONS: Low levels of HDL-C are an independent predictor of brachial artery enlargement in stable cardiac transplant recipients. These findings suggest that suboptimal HDL-C levels may be associated with the development of vascular remodeling and atherosclerosis in this population.

Adult↗
PubMed2006

Noninvasive testing for coronary artery disease in women.

Coronary artery disease is a major cause of morbidity and mortality for women in North America and Europe. Given the significance of coronary disease as a public health problem among women, accurate diagnosis of this condition is of great importance. Several noninvasive testing modalities are available for the diagnosis of coronary heart disease. An understanding of gender-based differences related to noninvasive cardiac testing is useful in order to optimally utilize these tests and improve detection and clinical outcomes in women.

Carotid Arteries↗
PubMed2002

Perforated aneurysms of left side valves during active infective endocarditis complicating hypertrophic obstructive cardiomyopathy.

The most frequent site of vegetative lesion in patients with hypertrophic cardiomyopathy is anterior mitral leaflet, due to chronic endocardial trauma arising from systolic anterior motion. We describe three cases of serious infective endocarditis complicated lesions (vegetation, aneurysm and perforation) on aortic and mitral valves, in patients with obstructive hypertrophic cardiomyopathy. In particular, we observed how severe valvular damage and dysfunction, combined with particular hemodynamic conditions, are followed by adverse clinical outcome. We performed transthoracic echocardiogram and transoesophageal echocardiography studies to define morphologic and hemodynamic features of infection, deciding the proper therapy and we planned the echocardiographic follow-up.

Adult↗
PubMed2001

Heart failure etiology affects peripheral vascular endothelial function after cardiac transplantation.

OBJECTIVES: The goal of this study was to examine the effect of heart failure etiology on peripheral vascular endothelial function in cardiac transplant recipients. BACKGROUND: Peripheral vascular endothelial dysfunction occurs in patients with heart failure of either ischemic or nonischemic etiology. The effect of heart failure etiology on peripheral endothelial function after cardiac transplantation is unknown. METHODS: Using brachial artery ultrasound, endothelium-dependent, flow-mediated dilation (FMD) was assessed in patients with heart failure with either nonischemic cardiomyopathy (n = 10) or ischemic cardiomyopathy (n = 7), cardiac transplant recipients with prior nonischemic cardiomyopathy (n = 10) or prior ischemic cardiomyopathy (n = 10) and normal controls (n = 10). RESULTS: Patients with heart failure with either ischemic cardiomyopathy or nonischemic cardiomyopathy had impaired FMD (3.6 +/- 1.0% and 5.1 +/- 1.2%, respectively, p = NS) compared with normal subjects (13.9 +/- 1.3%, p < 0.01 compared with either heart failure group). In transplant recipients with antecedent nonischemic cardiomyopathy, FMD was markedly higher than that of heart failure patients with nonischemic cardiomyopathy (13.0 +/- 2.4%, p < 0.001) and similar to that of normal subjects (p = NS). However, FMD remained impaired in transplant recipients with prior ischemic cardiomyopathy (5.5 +/- 1.5%, p = 0.001 compared with normal, p = 0.002 vs. transplant recipients with previous nonischemic cardiomyopathy). CONCLUSIONS: Peripheral vascular endothelial function is normal in cardiac transplant recipients with antecedent nonischemic cardiomyopathy, but remains impaired in those with prior ischemic cardiomyopathy. In contrast, endothelial function is uniformly abnormal for patients with heart failure, regardless of etiology. These findings indicate that cardiac transplantation corrects peripheral endothelial function for patients without ischemic heart disease, but not in those with prior atherosclerotic coronary disease.

Adult↗
PubMed2001

Impact directly over the cardiac silhouette is necessary to produce ventricular fibrillation in an experimental model of commotio cordis.

OBJECTIVES: In an experimental model of sudden death from chest wall impact (commotio cordis), we sought to define the chest wall areas important in the initiation of ventricular fibrillation (VF). BACKGROUND: Sudden death can result from an innocent chest blow by a baseball or other projectile. Observations in humans suggest that these lethal blows occur over the precordium. However, the precise location of impact relative to the risk of sudden death is unknown. METHODS: Fifteen swine received 178 chest impacts with a regulation baseball delivered at 30 mph at three sites over the cardiac silhouette (i.e., directly over the center, base or apex of the left ventricle [LV]) and four noncardiac sites on the left and right chest wall. Chest blows were gated to the vulnerable portion of the cardiac cycle for the induction of VF. RESULTS: Only chest impacts directly over the heart triggered VF (12 of 78: 15% vs. 0 of 100 for noncardiac sites: p < 0.0001). Blows over the center of the heart (7 of 23; 30%) were more likely to initiate VF than impacts at other precordial sites (5 of 55; 9%, p = 0.02). Peak LV pressures generated instantaneously by the chest impact were directly related to the risk of VF (p < 0.0006). CONCLUSIONS: For nonpenetrating, low-energy chest blows to cause sudden death, impact must occur directly over the heart. Initiation of VF may be mediated by an abrupt and substantial increase in intracardiac pressure. Prevention of sudden death from chest blows during sports requires that protective equipment be designed to cover all portions of the chest wall that overlie the heart, even during body movements and positional changes that may occur with athletic activities.

Animals↗
PubMed2001

Peripheral vascular endothelial function testing as a noninvasive indicator of coronary artery disease.

OBJECTIVES: We studied whether assessment of endothelium-dependent vasomotion (EDV) with brachial artery ultrasound (BAUS) imaging predicts the presence or absence of coronary artery disease (CAD) as defined by exercise myocardial perfusion imaging (ExMPI). BACKGROUND: Abnormalities in EDV can be detected in arteries before the development of overt atherosclerosis, and its presence may predict poor long-term prognosis. Brachial artery ultrasound during reactive hyperemia is a noninvasive method of assessing peripheral EDV. METHODS: Clinically-indicated ExMPI along with BAUS were performed in 94 subjects (43 women, 51 men). Coronary artery disease was defined by myocardial ischemia or infarction on single photon emission computed tomography images. Flow-mediated dilation (FMD) after upper arm occlusion was defined as the percent change in arterial diameter during reactive hyperemia relative to the baseline. RESULTS: Subjects with CAD by ExMPI (n = 23) had a lower FMD (6.3 +/- 0.7%) than those without CAD by ExMPI (n = 71) (10.5 +/- 0.6%; p = 0.0004). Flow-mediated dilation was highly predictive for CAD with an odds ratio of 1.32 for each percent decrease in FMD (p = 0.001). Based on a receiver-operator analysis, an FMD of 10% was used as a cut-point for further analysis. Twenty-one of 23 subjects who were positive for ExMPI had an FMD < 10% (sensitivity 91%), whereas only two of 40 subjects with an FMD > or =10% were ExMPI-positive (negative predictive value: 95%). There was a correlation between the number of cardiac risk factors and FMD. Individuals with an FMD < 10% exercised for a shorter duration than those with an FMD > or =10% (456 +/- 24 vs. 544 +/- 31 s, respectively; p = 0.02). CONCLUSIONS: Assessment of EDV with BAUS has a high sensitivity and an excellent negative predictive value for CAD and, thus, has the potential for use as a screening tool to exclude CAD in low-risk subjects. Further standardization of BAUS is required, however, before specific cut-points for excluding CAD can be established.

Brachial Artery↗
PubMed2001

Three-dimensional echocardiography: in-vitro validation of a new, voxel-based method for rapid quantification of ventricular volume in normal and aneurysmal left ventricles.

BACKGROUND: Previous approaches to ventricular volume calculations by 3-dimensional echocardiography (3-DE) required multiple transverse tomographic sectioning and summation of the volumes of parallel disks. These methods were time consuming and beared the risk of missing the apical volume. METHODS: We investigated the accuracy of a new, rapid method of 3-DE volume measurements in normal (LV) and aneurysmal (aneurLV) left ventricles in fixed pig hearts. 3-D data sets of 12 LV and 8 experimentally created aneurLV were obtained using a TomTec 3-DE system. For 3-DE volume calculations, a rotational axis in the center of the left ventricle (apical-basal orientation) was defined and 3, 6 and 12 equi-angular rotational planes were created. In each plane the endocardial border was traced and the volume of the corresponding wedge was automatically calculated. The measurements were performed by 2 independent investigators blinded to the anatomic volume and were analyzed for inter- and intraobserver variability. RESULTS: The anatomic volumes ranged from 5 to 150 ml and 9 to 40 ml in LV and aneurLV, respectively. The correlation between 3-DE and anatomic volume was excellent for LV and aneurLV traced in 3, 6 and 12 planes (r = 0.94-0.99). Ventricular volume was well predicted by 3-DE reconstruction: SEE 5.5-7.1 ml (LV), 3.0-3.2 ml (aneurLV). The correlation for interobserver measurements was good in both, LV (r = 0.99) and aneurLV (r = 0.94-0.99) even in 3 planes. The intra- and interobserver variabilities were 1.6-3.0 ml (<7%) and 7.2-7.3 ml (<15%) in LV and 1.1-1.6 (<6%) and 2.1-3.3 ml (<14%) in aneurLV respectively. CONCLUSION: This new 3-DE method of ventricular volume measurements using a rotational approach provides rapid, accurate and reproducible volume measurements in LV and aneurLV.

Animals↗
PubMed2001

Bulls-eye display and quantitation of myocardial perfusion defects using three-dimensional contrast echocardiography.

Three-dimensional (3-D) myocardial contrast echocardiography (MCE) is able to derive parallel cutting planes of the left ventricle (LV). However, assessment of the site and extent of myocardial perfusion abnormalities has to rely on the reader's 3-D mental reconstruction from the tomograms, and a manual approach has to be employed for quantitative analysis. The objective of this study was to explore the display and quantitative capability of a bulls-eye format from contrast 3-D MCE in the assessment of perfusion abnormalities derived from a canine model of acute myocardial infarction (MI). Three-dimensional MCE data were acquired sequentially in a rotational scanning format during triggered harmonic imaging with an intravenous contrast agent. Reconstructed short-axis views of the LV were aligned in a bulls-eye format with the apex as the inner most ring. The total LV was divided into 120 sectors. The number of sectors with lack of contrast enhancement was used to derive the percent of the LV (%LV) with perfusion defect and was compared with the extent of MI calculated from postmortem triphenyl tetrazolium chloride (TTC) staining. The perfusion defect regions shown on bulls-eye images corresponded correctly with the territories of the occluded coronary arteries. Three-dimensional MCE perfusion defect mass (19.2 +/- 6.0 %LV) correlated well with anatomic MI mass (19.3 +/- 5.6 %LV; r = 0.92, SEE = 2.3%, mean differential = 0.1 +/- 2.4%). We conclude that bulls-eye display of contrast 3-D MCE demonstrates the site and extent of perfusion abnormalities in an easily appreciable manner. It also allows fast and accurate assessment of endangered myocardium.

Animals↗
PubMed2001

Benign lipid envelope of the heart simulating a pericardial hematoma.

The hallmark of diagnosing a pericardial effusion by echocardiography is the presence of relatively sonolucent space outside of the cardiac structures. The location, size, mobility, and consistency of the pericardial space determined by echocardiography are considered to be reliable markers for defining pericardial processes. In certain clinical scenarios, however, it may be difficult to differentiate fluid from other pericardial processes, notably subepicardial adipose tissue. This case of a 76-year-old woman, who presented with possible cardiac tamponade after permanent pacemaker implantation, demonstrates some of the potential pitfalls in the diagnosis of pericardial space abnormalities.

Adipose Tissue↗
PubMed2001

Current status of three-dimensional echocardiography.

Volume rendered three-dimensional echocardiography (3DE), a rapidly emerging imaging method, offers clinicians and surgeons a new perspective for visualizing the heart. Using both transthoracic and transesophageal approach this new methodology enables qualitative and quantitative information of cardiac disorders to be obtained. 3DE image projections have allowed visualization of intracardiac structures and great vessels and delineation of their pathology in a comprehensive manner. Experimental and clinical studies suggest that 3DE is likely to play a valuable role in the evaluation of various cardiac and flow disorders and in planning interventions and surgery. In addition, 3DE has been applied to derive quantitative measurements of volume, mass and dimensions of the left and right ventricles and also other cardiac lesions, such as atrial and ventricular septal defects. Every aspect of 3DE is in continuous evolution. Faster and more highly automated image processing could make the technique more easily applicable in the clinical scenario.

Echocardiography, Three-Dimensional↗
PubMed2000

Does left ventricular shape influence clinical outcome in heart failure?

BACKGROUND: Left ventricular (LV) shape tends to become spherical in patients with dilated cardiomyopathy of diverse etiology. Clinical and echocardiographic factors which affect the degree of LV spherical distortion and the impact of altered LV shape on prognosis have not been studied adequately. HYPOTHESIS: This study was undertaken to investigate the prognostic implications of altered LV shape on clinical outcome in dilated cardiomyopathy. METHODS: In 112 patients with depressed LV ejection fraction (19 +/- 9%) and symptomatic heart failure, and in 10 age- and gender-matched normal controls, we performed 2-dimensional echocardiography to assess LV shape using the eccentricity index. Eccentricity index was defined as the ratio of the LV long axis to the LV transverse diameter, measured at end systole and end diastole in the apical four-chamber view. We sought univariate and multivariate clinical and echocardiographic correlates of LV shape. Further, we sought correlations between eccentricity index and clinical outcomes (death and composite outcome of death or emergent heart transplant). RESULTS: Compared with controls, patients with cardiomyopathy had significantly lower systolic (2.04 vs. 1.56; p = 0.001) and diastolic (1.75 vs. 1.53; p = 0.003) eccentricity index, implying a more spherical LV shape. Of all clinical and echocardiographic variables tested, mitral regurgitation, right ventricular dysfunction, and increased LV mass were independently associated with spherical LV shape. At a follow-up period of 17 +/- 12 months, no correlation was found between eccentricity index and the occurrence of death or the combined endpoint of death or emergent heart transplant, in univariate or multivariate analysis. CONCLUSIONS: In patients with dilated cardiomyopathy, the degree of spherical distortion of the LV does not correlate with prognosis.

Age Factors↗
PubMed2000

Three-dimensional transesophageal echocardiography (TEE) and other future directions.

As faster imaging systems enter the market, three-dimensional echocardiography is gearing up to become a useful tool in assisting the clinician to image the heart in many innovative projections. What started out as a novel idea of displaying a three-dimensional anatomic picture of the heart now provides a multitude of views of the heart and its structures. Information gained from anatomic and dynamic data has helped clinicians and surgeons in making clinical decisions. In the future, this imaging modality may become a routine imaging modality for assessing cardiac pathology and may serve to increase understanding of the dynamics of the heart.

Echocardiography, Doppler, Color↗
PubMed2000

Harmonic imaging with Levovist for transthoracic echocardiographic reconstruction of left ventricle in patients with post-ischemic left ventricular dysfunction and suboptimal acoustic windows.

BACKGROUND: Attempts to perform transthoracic 3-dimensional echocardiography (3DE) are often encumbered by poor definition of chamber borders in adult patients who have technically suboptimal acoustic windows. METHODS: To assess whether harmonic imaging (HI) and contrast agents can facilitate transthoracic 3DE assessment of the left ventricle, we used fundamental imaging (FI), HI alone, and HI coupled with the echo-enhancing contrast agent Levovist in 15 consecutive patients with post-ischemic left ventricular (LV) dysfunction and technically difficult windows. Dynamic 3DE image data sets were obtained at 5-degree angles (36 slices) from a transthoracic apical view. From these data a total of 240 myocardial segments were analyzed with the use of dynamic short-axis paraplane slices at basal, middle, and apical LV levels (standard 16 segment model). For border definition, each segment was scored in random sequence on the following scale by 2 independent investigators: 0 = not seen, 1 = suboptimal visualization, and 2 = well defined. RESULTS: Our results showed a significant increase in the number of well-visualized segments when harmonic mode combined with Levovist injection was compared with FI and HI alone. CONCLUSION: Harmonic imaging alone improves LV assessment by 3DE when compared with FI. Contrast imaging in which Levovist is added to HI further improves the capability of transthoracic tomographic 3DE in the visualization of LV myocardial segments. This could allow 3DE by transthoracic windows to be used more widely in adults for the evaluation of LV volume and function.

Adult↗
PubMed2000

Quantitative 3-dimensional contrast echocardiographic determination of myocardial mass at risk and residual infarct mass after reperfusion: experimental canine studies with intravenous contrast agent NC100100.

Two-dimensional contrast echocardiography has been shown to enable the evaluation of myocardial perfusion abnormalities. However, its ability to quantify a regional myocardial mass is limited. The goal of this study was to examine the quantitative value of 3-dimensional echocardiography (3DE) in the estimation of myocardial mass at risk, salvaged mass, and residual infarct mass after intravenous injection of contrast. We created acute coronary occlusion, followed by reperfusion in 10 dogs. Three-dimensional echocardiographic data were acquired at the end of each stage, and the perfusion defect mass and dysfunctional mass were measured. The true mass at risk and infarct mass were determined by anatomic methods. The anatomic mass at risk (x) (27.1+/-14.6 g or 23.8%+/-9.7% of the left ventricle [%LV]) correlated well with the 3DE-determined perfusion defect mass (y) during coronary occlusion (y = 0.5x+8.9; r = 0.90; P<.001; mean difference -4.8+/-8.1 g; or y = 0.7x + 6.5; r = 0.83, P<.01; mean difference -0.1+/-5.4 %LV). Good correlation was also found between the anatomic infarct mass (x) (9.3+/-8.1 g or 9.1+/-8.8 %LV) and the 3DE perfusion defect mass after reperfusion (y) (y = 1.2x+1.2; r = 0.93; P<.001; mean difference 2.3+/-4.0 g; or y = 1. 3x, r = 0.98, P <.0001; mean difference 2.7+/-3.7 %LV). The salvaged mass was 13.6 +/-11.0 %LV from anatomic methods and 14.2+/-13.0 %LV by 3DE. To conclude, with the use of intravenous contrast, 3DE could quantify the actual mass at risk during acute ischemia, and in the setting of reperfusion, the residual infarct mass and salvaged mass.

Animals↗
PubMed2000

Diagnostic accuracy of transthoracic and multiplane transesophageal echocardiography for valvular perforation in acute infective endocarditis: correlation with anatomic findings.

We evaluated the diagnostic accuracy of transthoracic and multiplane transesophageal echocardiography (TTE and TEE, respectively) for assessing valvular perforation during active infective endocarditis by correlating the results of TTE and TEE with anatomic findings of 88 valves examined at surgery or autopsy. Compared with TEE, TTE has a low diagnostic sensitivity in the detection of this complication and, in the presence of hemodynamic instability, multiplane TEE should be performed directly.

Adult↗