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Biomedical subjects

Sanjay K Prasad

Publications and source records attributed to Sanjay K Prasad.

17 recordsLinked to original sources
PubMed2006

Reference right ventricular systolic and diastolic function normalized to age, gender and body surface area from steady-state free precession cardiovascular magnetic resonance.

AIMS: Recent advances in cardiovascular magnetic resonance (CMR) include improved image quality with steady-state free precession (SSFP) sequences and advanced post-processing of high temporal resolution ventricular function. We used these techniques to establish the reference values for right ventricular (RV) volumes and function. METHODS AND RESULTS: We studied 120 healthy subjects (60 men, 60 women; from 20 to 80 years) after exclusion of cardiovascular abnormality. Data were generated from SSFP cines, with three-dimensional modelling. Gender, body surface area (BSA), and age were independent predictors of several RV parameters. Normalized RV mass (RVM) and absolute and normalized RV volumes decreased significantly with age, whereas ejection fraction increased. For diastolic variables, absolute and normalized early peak filling rate (PFR(E)) decreased and absolute and normalized active peak filling rate (PFR(A)) in males increased, with decreased PFR(E)/PFR(A). Increasing BSA was associated with increased RVM, volumes, and PFR(E). Gender significantly influenced absolute and normalized mass and volumes, and absolute and normalized PFR(A). CONCLUSION: These data using state-of-the-art CMR show that normal values of RV systolic and diastolic parameters vary significantly by gender, BSA, and age. Appropriate reference ranges normalized to all three variables should be used in the determination of normality or severity of abnormality of RV dimensions and function.

Adult↗
PubMed2006

Cardiovascular magnetic resonance in arrhythmogenic right ventricular cardiomyopathy revisited: comparison with task force criteria and genotype.

OBJECTIVES: We sought to assess the utility of cardiovascular magnetic resonance (CMR) in the evaluation of arrhythmogenic right ventricular cardiomyopathy (ARVC) in relation to diagnostic criteria and genotype. BACKGROUND: Timely diagnosis of ARVC is difficult as clinical findings may be subtle and nonspecific in early disease. The role of CMR is controversial owing to the absence of a standardized protocol, insufficient experience with the modality, and inherent difficulties in imaging the right ventricle. METHODS: Comprehensive CMR examination was performed in 232 patients undergoing evaluation for suspected ARVC. CMR outcomes were compared with: 1) prospective clinical diagnosis using Task Force guidelines, with and without the proposed modifications for familial ARVC; and 2) gene-carrier status in 35 individuals from genotyped families. RESULTS: CMR studies were positive in all 64 patients who prospectively fulfilled Task Force criteria, resulting in 100% sensitivity. Specificity in relation to Task Force criteria was low (29%). Of the 119 apparent false positives detected by CMR, however, 63 fulfilled modified diagnostic criteria for familial ARVC and 7 were obligate gene carriers, suggesting that CMR frequently identifies individuals with early disease, in whom Task Force criteria are relatively insensitive. This was borne out by evaluation of genotyped individuals (26 gene-positive and 9 gene-negative), in whom CMR had a sensitivity of 96% and a specificity of 78%. CONCLUSIONS: CMR is a valuable component of the diagnostic workup for ARVC when performed with a dedicated protocol by specialists with experience in analysis of volumes, right ventricular wall motion, and delayed-enhancement imaging.

Adolescent↗
PubMed2006

Cardiovascular magnetic resonance, fibrosis, and prognosis in dilated cardiomyopathy.

OBJECTIVES: We studied the prognostic implications of midwall fibrosis in dilated cardiomyopathy (DCM) in a prospective longitudinal study. BACKGROUND: Risk stratification of patients with nonischemic DCM in the era of device implantation is problematic. Approximately 30% of patients with DCM have midwall fibrosis as detected by late gadolinium-enhancement (LGE) cardiovascular magnetic resonance (CMR), which may increase susceptibility to arrhythmia and progression of heart failure. METHODS: Consecutive DCM patients (n = 101) with the presence or absence of midwall fibrosis were followed up prospectively for 658 +/- 355 days for events. RESULTS: Midwall fibrosis was present in 35% of patients and was associated with a higher rate of the predefined primary combined end point of all-cause death and hospitalization for a cardiovascular event (hazard ratio 3.4, p = 0.01). Multivariate analysis showed midwall fibrosis as the sole significant predictor of death or hospitalization. However, there was no significant difference in all-cause mortality between the 2 groups. Midwall fibrosis also predicted secondary outcome measures of sudden cardiac death (SCD) or ventricular tachycardia (VT) (hazard ratio 5.2, p = 0.03). Midwall fibrosis remained predictive of SCD/VT after correction for baseline differences in left ventricular ejection fraction between the 2 groups. CONCLUSIONS: In DCM, midwall fibrosis determined by CMR is a predictor of the combined end point of all-cause mortality and cardiovascular hospitalization, which is independent of ventricular remodeling. In addition, midwall fibrosis by CMR predicts SCD/VT. This suggests a potential role for CMR in the risk stratification of patients with DCM, which may have value in determining the need for device therapy.

Adult↗
PubMed2006

Improved turbo spin-echo imaging of the heart with motion-tracking.

PURPOSE: To improve dark-blood and short tau inversion recovery (STIR) prepared turbo spin-echo (TSE) imaging of the heart, particularly in the basal short-axis plane where cardiac misregistration between the preparation and imaging phases is high. MATERIALS AND METHODS: In the first approach (tracked), the basal short-axis plane was labeled and tracked over the cardiac cycle. The slice-selective 180 degrees dark-blood and STIR preparation pulses were then independently positioned on the appropriately timed labeled images. In the second approach (offset), the preparation pulses were output in the same orientation as the imaging plane, but with a user-defined slice offset that was derived from the labeled data. Both approaches were compared with the standard untracked dark-blood STIR TSE sequence (7-mm slice thickness) in 10 healthy volunteers. RESULTS: For typical preparation slice thicknesses, tracked and offset TSE images were superior to the untracked images (both P < 0.01). For the more mobile right ventricle (RV), the image quality of the tracked images was superior to that of the offset images (P < 0.05). CONCLUSION: Tracking the through-plane motion of the heart between preparation and imaging phases improves the quality of thin-slice basal short-axis TSE images, particularly for the more mobile RV.

Algorithms↗
PubMed2006

Primary myocardial dysfunction in autosomal dominant EDMD. A tissue doppler and cardiovascular magnetic resonance study.

BACKGROUND: Emery-Dreifuss muscular dystrophy is a genetically heterogeneous form of muscular dystrophy. One form is inherited in an X-linked fashion and is secondary to mutations in the gene encoding the nuclear protein emerin. A more common variant is inherited in an autosomal dominant way (EDMD2) due to mutations affecting the nuclear lamina protein lamin A/C. Typical features of both conditions are relatively mild skeletal muscle weakness, but cardiac involvement develops almost invariably by adult age, including conduction defects, arrhythmias and cardiomyopathy. Thus, early detection of cardiac abnormalities may be important for planning early therapeutic intervention. AIM: In this study, we hypothesized that early myocardial dysfunction can be detected by tissue Doppler echocardiography and CMR in unselected patients with the autosomal dominant form of Emery-Dreifuss muscular dystrophy. This would suggest that fibrosis could be implicated in the pathogenesis of cardiac dysfunction in EDMD2. METHODS: Eight consecutive patients with genetically proven EDMD2 without pacemakers were enrolled in the study and compared to eight age-matched controls. All patients and controls first underwent a comprehensive echocardiographic-Doppler examination, followed by measurement of mitral annular velocities using pulsed tissue Doppler. Color M-mode tissue images were recorded from the parasternal long axis projections to derive Myocardial Velocity Gradients (MVG). Subsequently, all subjects underwent cardiovascular magnetic resonance (CMR) imaging for function, intrinsic myocardial tissue contrast using T1 and T2 weighted spin echo (TSE) for fat deposition and extrinsic contrast (Gadolinium-DTPA late fibrosis imaging). Strain measurements, using harmonic phase imaging (HARP) tagging were also derived. RESULTS: Cavity dimensions LV mass and fractional shortening were similar between patients and controls. The overall body mass index was less in patients than in controls (14.5 +/- 1.4 vs. 18.1 +/- 2.4 g/m2, p < 0.002). While systolic MVG were similar between groups, the early diastolic MVG was lower in patients than in controls (4 +/- 1.2 s-1 vs. 7.1 +/- 2.7, p < 0.02). On CMR, LA and LV, RV volumes were similar between patients and controls. CMR strain patterns, however, showed a significant reduction in inferior wall contractility in patients compared to controls (-0.06 +/- 0.02 vs -0.09 +/- 0.03, p < 0.05). No patient showed late gadolinium enhancement. CONCLUSION: Patients with EDMD2 have abnormal left ventricular function prior to developing any cardiac symptoms. The absence of myocardial fibrosis, however, by CMR suggests that this functional abnormality may not be secondary to scarring but could precede it. Tissue Doppler echocardiography and CMR are sensitive methods of assessing the presence of myocardial dysfunction prior to the development of any cardiovascular symptoms.

Adolescent↗
PubMed2005

Optimization of the arterial input function for myocardial perfusion cardiovascular magnetic resonance.

PURPOSE: To determine how injection rate, cardiac function, and breathhold influence the arterial input function (AIF), in order to optimize the AIF in the clinical setting for quantitative myocardial perfusion cardiovascular magnetic resonance (CMR). MATERIALS AND METHODS: Gd (0.1 mmol/kg) bolus was injected at 3, 5, or 7 mL/second in 35 patients. In each cardiac cycle during the first-pass, a series of saturation recovery (SR) fast low-angle shot (FLASH) low resolution images with exponentially increasing SR delay times were acquired. Signal intensity (SI) time measurements were made from a region of interest (ROI) drawn in the ascending aorta (AA). The calculation of short T1s and thus peak Gd concentration [Gd] was performed by fitting the mean ROI SI against SR delay times. RESULTS: The mean peak [Gd] in the AA increased as injection rate increased from 3 mL/second (5.0 mM), to 5 mL/second (7.1 mM), to 7 mL/second (4 mM) (P < 0.0001). The peak [Gd] increased as the left ventricular stroke volume (LV SV) increased (P = 0.01). Breath holding was not found to influence peak [Gd]. CONCLUSION: In this study, we found that a high injection rate has advantages over lower injection speeds, although the duration of the AIF was apparently not significantly shortened by faster injection. The choice of expiration or inspiration as breathhold did not have a significant influence upon the AIF. Poor cardiac function was associated with a lower peak [Gd], indicating that first pass perfusion measurements in these patients will be suboptimal.

Aorta↗
PubMed2005

Role of CMR in assessment of myocardial perfusion.

Ischaemic heart disease is a major cause of morbidity and mortality. Assessment of myocardial perfusion is important in assessing the severity and extent of coronary artery lesions and in helping to guide revascularisation strategies where stenoses are documented. It provides information on the haemodynamic significance and a guide to prognosis. There has been much interest in the role of CMR assessment of perfusion and the opportunity for subendocardial resolution. We present an overview on its current status.

Coronary Circulation↗
PubMed2005

Cardiovascular magnetic resonance and the evaluation of heart failure.

Cardiovascular magnetic resonance (CMR) has established itself as probably the single best way of phenotyping the failing heart. It is the accepted gold standard for measuring cardiac function, volumes, and mass, but within the same scan session additional techniques are available for greater definition. Tissue characterization with the contrast agent gadolinium is well validated and allows the precise visualization and quantification of myocardial infarction. This can be used for viability assessment and to determine heart failure etiology. Dobutamine stress CMR and CMR perfusion hold advantages over conventional techniques. The new frontiers of CMR in heart failure hold the promise of unique insights quantifying myocardial iron, nonischemic fibrosis, microvascular perfusion, plaque characterization, and CMR-targeted intervention. The development and validation of these techniques represent major research challenges for the future. From a clinical perspective, an equal challenge is in increasing the availability of the modality for patients and physicians.

Cardiomyopathies↗
PubMed2005

Comparison of hybrid echo-planar imaging and FLASH myocardial perfusion cardiovascular MR imaging.

The purpose of this study was to compare fast single-shot gradient-echo (FLASH) and hybrid echo-planar imaging (EPI) magnetic resonance (MR) technologies regarding the relative contrast-to-noise ratio (CNR), spatiotemporal resolution, size of inducible perfusion defects, and presence of artifacts in patients with coronary artery disease (CAD). Fifteen patients with CAD underwent rest and adenosine stress gadolinium first-pass perfusion cardiovascular MR examinations with EPI and FLASH. The study was approved by the local ethics committee, and each subject gave written informed consent. The spatial resolution of the two sequences was made similar in nine patients, and the temporal resolution was made similar in six. The images were assessed for CNR, artifact, and size of inducible perfusion defects. The CNR was significantly higher with the EPI sequence, whether matched for spatial (32 vs 22 [46%], P < .001) or temporal (35 vs 23 [51%], P < .001) resolution. There was no significant difference in scoring for artifact or area and transmural extent of inducible perfusion defects with EPI and FLASH, whether matched for temporal or spatial resolution. Further work is warranted to determine the relative diagnostic accuracy of the two techniques.

Aged↗
PubMed2004

Role of magnetic resonance angiography in the diagnosis of major aortopulmonary collateral arteries and partial anomalous pulmonary venous drainage.

BACKGROUND: Accurate diagnosis of major aortopulmonary collaterals (MAPCAs) and partial anomalous pulmonary venous drainage (PAPVD) in adult patients with congenital heart disease is important but problematic. Three-dimensional contrast-enhanced magnetic resonance angiography (MRA) provides a minimally invasive technique to allow detailed studies in a single breath-hold. METHODS AND RESULTS: We assessed the role of contrast-enhanced 3D MRA in 29 consecutive adult patients with a diagnosis of MAPCAs (n=16) or PAPVD (n=13) made by echocardiogram, cardiac catheterization, or surgical inspection. MRA was performed with a 3D spoiled gradient-echo technique with intravenous gadolinium-DTPA (0.2 mmol/kg). In both types of pathology, there was excellent correlation between MRA and the cardiac catheterization, echocardiogram, or surgical inspection. Additional information was gained for patients with MAPCAs on confluence and size of pulmonary arteries (n=13 had central arteries), pulmonary artery stenosis (n=3), aneurysmal dilatation of pulmonary artery (n=1), and additional anomalous vascular abnormality (n=3). Shunt assessment, where present (9 of 16), showed patency in all cases (100%). For adults with PAPVD, further information was obtained on drainage origin (n=11). There were no complications. CONCLUSIONS: Contrast-enhanced 3D MRA provides a fast, noninvasive, radiation-free method of accurate and comprehensive diagnosis of MAPCAs and PAPVD in adult patients.

Adolescent↗
PubMed2004

Clinical and haemodynamic effects of sildenafil in pulmonary hypertension: acute and mid-term effects.

AIM: The treatment of patients with pulmonary arterial hypertension remains a challenge. We set out to investigate the use of sildenafil, a selective inhibitor of phosphodiesterase type 5, in patients with this disease. METHODS AND RESULTS: Ten patients (8 females, mean age 34.5+/-3.3 years) with pulmonary hypertension underwent right heart catheterisation with vasodilator testing using incremental doses of intravenous sildenafil without adverse events. All patients were subsequently commenced on oral sildenafil 50 mg t.d.s. Nine patients had repeat right heart catheterisation 3 months after the commencement of oral therapy. There was a significant reduction in mean pulmonary artery pressure (from 55.8+/-5.9 to 50.4+/-6.1 mmHg, p=0.038 ) and pulmonary vascular resistance (from 10.1+/-1.7 to 8.6+/-1.5 Wood units, p=0.009 ), and an increase in cardiac output (from 4.7+/-0.3 to 5.0+/-0.4 l/min, p=0.15 ). Furthermore, there was a significant increase in the 6-minute walk test, a mean of 112 m. In response to a quality-of-life questionnaire, patients indicated marked clinical improvement on sildenafil. Sildenafil was discontinued in 1 patient due to a transient visual disturbance. The only patient previously awaiting transplantation was removed from the active transplantation list. CONCLUSIONS: Sildenafil is well tolerated in its intravenous and oral forms and appears to improve both pulmonary haemodynamics and the clinical status of patients with pulmonary hypertension after 3 months of oral therapy.

Administration, Oral↗
PubMed2004

Combined long- and short-axis myocardial perfusion cardiovascular magnetic resonance.

PURPOSE: To date, myocardial perfusion cardiovascular magnetic resonance (CMR) has been reported in single and multiple short-axis slices. Three short-axis planes can assess 16 segments of the standard 17-segment myocardial model, but this approach fails to assess the ventricular apex that requires at least one long-axis plane. We therefore evaluated the feasibility and benefit of combined long- and short-axis perfusion CMR to enable complete 17 segments coverage for comprehensive myocardial perfusion assessment. METHODS AND MATERIALS: Using a hybrid echo planar imaging (EPI) sequence, we performed rest and adenosine stress first-pass perfusion CMR studies with 3 short-axis (basal, mid, apical) planes, and additional long-axis planes in the same cardiac cycle in a broad range of cardiology patients. RESULTS: Perfusion CMR was performed in 53 consecutive patients using the combined short-long-axis imaging protocol. Twenty-nine of those studied had known or suspected coronary artery disease (CAD), 18 hypertrophic cardiomyopathy, and 6 suspected microvascular perfusion abnormalities. In 39 patients (70%), it was possible to acquire 5 slices at rest and stress including both the horizontal and vertical long axes. In 15 patients (27%), only one long-axis could be acquired, and in 2 patients (5%) only 3 slices (short axis) could be obtained. However, in none of the patients with known or suspected CAD was apical ischemia demonstrated by the long-axis views, despite apical ischemia having been demonstrated with recent SPECT studies in 8 of these patients. CONCLUSION: Rest-stress myocardial perfusion CMR is able to achieve complete segmental coverage of the myocardium using the combined short-long axis approach using an EPI sequence in 97% of a long series of consecutive cardiology patients, while maintaining excellent spatial resolution. However, the long-axis views were not found to be able to demonstrate inducible perfusion defects in the apex.

Adult↗