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Biomedical subjects

C B Higgins

Publications and source records attributed to C B Higgins.

At least 109 records · Page 6Linked to original sources
PubMed1996

Magnetic resonance imaging of acquired cardiac disease.

Over the last 15 years, advances in magnetic resonance imaging techniques have increased the accuracy and applicability of cardiovascular magnetic resonance imaging. These advances have improved the utility of magnetic resonance imaging in evaluating cardiac morphology, blood flow, and myocardial contractility, all significant diagnostic features in the evaluation of the patient with acquired heart disease. Utilization of cardiovascular magnetic resonance imaging has been limited, primarily due to clinical reliance upon nuclear scintigraphy and echocardiography. Recent developments in fast and ultrafast imaging should continue to enhance the significance of magnetic resonance imaging in this field. Widespread use of magnetic resonance imaging in the evaluation of the cardiovascular system will ultimately depend upon its maturation into a comprehensive, noninvasive imaging technique for the varying manifestations of acquired heart disease, including cardiomyopathy, ischemic heart disease, and acquired valvular disease.

Aorta, Thoracic↗
PubMed1995

Evaluation of mitral stenosis with velocity-encoded cine-magnetic resonance imaging.

Velocity-encoded cine-magnetic resonance imaging (VEC-MRI) is a new method for quantitation of blood flow with the potential to measure high-velocity jets across stenotic valves. The objective of this study was to evaluate the ability of VEC-MRI to measure transmitral velocity in patients with mitral stenosis. Sixteen patients with known mitral stenosis were studied. A 1.5 Tesla superconducting magnet was used to obtain velocity-encoded images in the left ventricular short-axis plane. Images were obtained throughout the cardiac cycle at 3 consecutive slices beginning proximal to the mitral coaptation point. To determine the optimal slice thickness for MRI imaging, both 10 mm and 5 mm thicknesses were used. Echocardiography including continuous-wave Doppler was performed on every patient within 2 hours of MRI imaging. Peak velocity was determined for both VEC-MRI and Doppler-echo images. Two observers independently measured the VEC-MRI mitral inflow velocities. Of the 16 patients, imaged data were incomplete in only 1 study, and all images were adequate for analysis. Strong correlations were found for measurements of mitral valve gradient for both 10 mm (peak r = 0.89, mean r = 0.84) and 5 mm (peak r = 0.82, mean r = 0.95) slice thicknesses. Measurements of peak velocity with VEC-MRI (10 mm) agreed well with Doppler: mean 1.46 m/s, mean of differences (Doppler MRI) 0.38 m/s, standard deviation of differences 0.2 m/s. These findings suggest that VEC-MRI can noninvasively determine the severity of mitral stenosis.

Adult↗
PubMed1995

Assessment of valvular heart disease by magnetic resonance imaging.

MRI has developed very rapidly and now provides anatomic and functional information in cases of valvular heart disease. MRI has several important attributes that make it advantageous for the evaluation of valvular heart disease. First, the natural contrast between flowing blood and surrounding cardiovascular structures provides sharp delineation of endocardial and epicardial borders without the need for contrast media. This feature in combination with the essential three-dimensional nature of this imaging technique allows precise quantification of cardiac volumes, function, and mass without the use of any assumed formulas or geometric models. Second, blood flow-sensitive GRE techniques are able to identify areas of turbulent flow caused by stenotic or regurgitant valves. With this technique regurgitant jets can be visualized and semiquantitative grading can be performed as with color Doppler. Third, recently developed velocity-encoded techniques permit measurements of blood flow velocities across stenotic native and prosthetic heart valves and retrograde flow caused by regurgitation. Moreover, the close interstudy reproducibility of measurements of cardiac dimensions and valvular regurgitation suggests a role in assessing the effect of therapeutic interventions.

Echo-Planar Imaging↗
PubMed1995

Multislice measurement of first-pass transit of gadobenate dimeglumine in normal and ischemic myocardium in dogs.

RATIONALE AND OBJECTIVES: We monitored the differences in the first passage of gadobenate dimeglumine through normal and ischemic myocardium with left anterior descending (LAD) coronary artery occlusion in dogs. METHODS: Dynamic multislice images of the heart were taken on a 1.5-T magnetic resonance (MR) imager. In six normal dogs, inversion recovery (IR)-prepared fast gradient-recalled echo (GRE) images were acquired at five doses of gadobenate dimeglumine (0.005-0.1 mmol/kg). First passage of the contrast medium through normal and acutely ischemic myocardium were monitored in seven dogs subjected to LAD coronary artery occlusion. RESULTS: IR-prepared GRE images showed a dose-dependent increase in the signal intensity (SI) of the myocardium. In dogs with LAD coronary artery occlusion, there was a significant increase in the SI of normal myocardium (p < .01) than in ischemic myocardium after injection of 0.025 mmol/kg gadobenate dimeglumine. CONCLUSION: The first-pass dynamics of gadobenate dimeglumine through normal and ischemic myocardium can be monitored with a multislice acquisition using a clinical MR imager and differentiated between normal and ischemic myocardium in dogs.

Animals↗
PubMed1995

Coronary artery stenosis: detection with contrast-enhanced MR imaging in dogs.

PURPOSE: To monitor with fast gradient-echo magnetic resonance (MR) imaging the dynamics of gadolinium benzyloxypropionictetraacetate (gadobenate) dimeglumine on myocardial signal intensity in dogs with critical left circumflex coronary artery stenosis. MATERIALS AND METHODS: Fast gradient-echo MR images were acquired in a short axis of the left ventricle. Two bolus injections of 0.05 mmol/kg gadobenate dimeglumine were administered in the basal state after stenosis and after infusion of 0.5 mg/kg dipyridamole. RESULTS: In the basal state, there was an equivalent increase in signal intensity of normal and hypoperfused myocardium during the first pass. Dipyridamole increased left anterior descending flow (287% +/- 36; P < .05) and decreased left circumflex flow (65% +/- 14; P < .05). The magnitude of signal intensity increase during the second bolus in the hypoperfused region was less than that of normal myocardium (P < .05). Contrast-enhanced images showed the hypoperfused region as smaller than the postmortem measurement (43.8% +/- 3.3; P < .05). CONCLUSION: Contrast-enhanced fast MR imaging in the vasodilated state allows detection of hypoperfused myocardium in the presence of critical coronary stenosis.

Animals↗
PubMed1995

Primary bone tumors: value of MR angiography for preoperative planning and monitoring response to chemotherapy.

OBJECTIVE: The purposes of our study were to investigate the use of MR angiography with two- (2D) and three-dimensional (3D) displays in evaluating vascular morphology of musculoskeletal neoplasms for preoperative planning of limb-salvage surgery and to assess the use of MR angiography for monitoring changes in neovascularity and evaluating response to chemotherapy. SUBJECTS AND METHODS: We used MR angiography (2D time-of-flight) to study 13 patients with primary bone tumors (nine osteogenic sarcomas, two Ewing's sarcomas, and two primary lymphomas of bone) at the time of initial presentation. Eight patients (all of whom had osteogenic sarcoma) also underwent MR angiography following chemotherapy before limb-salvage surgery. Two-dimensional maximum intensity projections were obtained. Three-dimensional reconstructions of vascular structures were created from the angiographic source images and were displayed simultaneously with 3D reconstructions of tumor and normal bone generated from conventional MR images. RESULTS: Two-dimensional maximum intensity projections were useful for evaluating small vessel neovascularity; 3D displays demonstrated spatial relationships of tumor, feeder vessels, and normal vascular structures. Tumor encroachment onto or encasement of normal vascular structures was shown in four patients on 2D maximum intensity projections and on 3D displays. The eight patients with osteogenic sarcoma who had follow-up imaging showed marked neovascularity prior to chemotherapy. Five patients responded to chemotherapy (> or = 90% tumor necrosis at histology); MR angiography showed marked reduction in tumor neovascularity in these patients. Three patients did not respond to chemotherapy; MR angiography showed unchanged neovascularity in one and increased neovascularity in two of these patients. CONCLUSION: MR angiography provides good visualization of peripheral vascular branches and tumor neovascularity in patients with primary bone tumors. MR angiography demonstrates encroachment onto and encasement of major vessels by the tumor mass and appears to be useful for assessing response to chemotherapy in osteogenic sarcoma and possibly other primary bone tumors by detecting treatment-induced changes in tumor neovascularity.

Adolescent↗
PubMed1995

The developing role of magnetic resonance contrast media in the detection of ischemic heart disease.

Recent developments in magnetic resonance (MR) imaging have opened up new avenues in the investigation of cardiovascular physiology. Inherent signal intensity of any tissue on MR images depends largely on proton concentration as well as longitudinal (T1) and transverse (T2) relaxation times. Myocardial contrast can be manipulated by using specific MR pulse sequences which are selectively sensitive to differences in any one of these parameters. Paramagnetic metal complexes are used as contrast media in MR imaging to enhance the inherent contrast. Contrast media in MR imaging are not directly visible but change the magnetic properties of other nuclei in close proximity, such as those of the water hydrogen. The signal of water can be altered by the contrast medium in different ways, either by changing the relaxation times or through bulb susceptibility effects, or both. The role of MR contrast media for quantitative characterization of ischemic heart disease has advanced considerably in the past 10 years. Conventional MR imaging techniques following the administration of contrast media are useful for identifying and sizing myocardial infarctions and for distinguishing between occlusive and reperfused myocardial infarctions as well as reversible (stunned) and irreversible injuries. Recent results suggest that contrast-enhanced MR imaging can also be used to identify dead cells in reperfused ischemically injured myocardium. The recently developed fast MR imaging techniques, with the aid of MR contrast media as a perfusion indicator, may be useful in estimating regional myocardial perfusion and blood volume. The assessment of capillary circulation or myocardial perfusion may be used for evaluating the extent of hypoperfusion and treatment efficacy. Experimental and clinical perfusion studies indicate that perfusion-sensitive MR imaging detects compromised myocardium (area at risk). Combining myocardial perfusion imaging with the anatomic and functional information provided by other MR imaging sequences could make MR imaging a comprehensive noninvasive technique for the evaluation of ischemic heart disease.

Animals↗
PubMed1995

The use of magnetic resonance imaging in adult congenital heart disease.

Magnetic resonance (MR) imaging techniques have evolved sufficiently to produce clinically relevant studies that depict the anatomy and physiology of the heart. Applications to congenital cardiac disease in adult patients are numerous. MR imaging is particularly useful for noninvasive evaluation of the aorta in patients with aortic arch anomalies and coarctations and to study the results of palliative and corrective surgery for transposition of the great arteries and for reconstructive procedures that restore sufficient pulmonary blood flow. MR imaging is superior to transthoracic echocardiography in defining the anatomy of the central pulmonary arteries. Recent technological advances permit motion studies acquired during a single breath-hold and can be used to accurately measure stroke volume, ejection fraction, regional wall motion, and wall thickening from both ventricles. Functional parameters, such as the velocity and volume of blood flow in vessels, valve gradients, regurgitant flow, shunt flow, and pulmonary artery blood flow into each lung are readily performed. This review article documents the value of MR imaging in adult patients with congenital disorders of the heart, pulmonary arteries, and aorta, and includes illustrations of typical examples.

Adult↗
PubMed1994

Quantification of mitral regurgitation by velocity-encoded cine nuclear magnetic resonance imaging.

OBJECTIVES: The feasibility of velocity-encoded cine nuclear magnetic resonance (NMR) imaging to measure regurgitant volume and regurgitant fraction in patients with mitral regurgitation was evaluated. BACKGROUND: Velocity-encoded cine NMR imaging has been reported to provide accurate measurement of the volume of blood flow in the ascending aorta and through the mitral annulus. Therefore, we hypothesized that the difference between mitral inflow and aortic systolic flow provides the regurgitant volume in the setting of mitral regurgitation. METHODS: Using velocity-encoded cine NMR imaging at a magnet field strength of 1.5 T and color Doppler echocardiography, 19 patients with isolated mitral regurgitation and 10 normal subjects were studied. Velocity-encoded cine NMR images were acquired in the short-axis plane of the ascending aorta and from the short-axis plane of the left ventricle at the level of the mitral annulus. Two independent observers measured the ascending aortic flow volume and left ventricular inflow volume to calculate the regurgitant volume as the difference between left ventricular inflow volume and aortic flow volume, and the regurgitant fraction was calculated. Using accepted criteria of color flow Doppler imaging and spectral analysis, the severity of mitral regurgitation was qualitatively graded as mild, moderate or severe and compared with regurgitant volume and regurgitant fraction, as determined by velocity-encoded cine NMR imaging. RESULTS: In normal subjects the regurgitant volume was -6 +/- 345 ml/min (mean +/- SD). In patients with mild, moderate and severe mitral regurgitation, the regurgitant volume was 156 +/- 203, 1,384 +/- 437 and 4,763 +/- 2,449 ml/min, respectively. In normal subjects the regurgitant fraction was 0.7 +/- 6.1%. In patients with mild, moderate and severe mitral regurgitation, the regurgitant fraction was 3.1 +/- 3.4%, 24.5 +/- 8.9% and 48.6 +/- 7.6%, respectively. The regurgitant fraction correlated well with the echocardiographic severity of mitral regurgitation (r = 0.87). Interobserver reproducibilities for regurgitant volume and regurgitant fraction were excellent (r = 0.99, SEE = 238 ml; r = 0.98, SEE = 4.1%, respectively). CONCLUSIONS: These findings suggest that velocity-encoded NMR imaging can be used to estimate regurgitant volume and regurgitant fraction in patients with mitral regurgitation and can discriminate patients with moderate or severe mitral regurgitation from normal subjects and patients with mild regurgitation. It may be useful for monitoring the effect of therapy intended to reduce the severity of mitral regurgitation.

Adult↗
PubMed1994

Reperfused myocardial infarctions on T1- and susceptibility-enhanced MRI: evidence for loss of compartmentalization of contrast media.

The purpose of this study was to characterize the contrast caused by a susceptibility MRI contrast agents, on spin echo T2-weighted imaging of reperfused myocardial infarction. Our interest in this model focused on the expected requirement that such agents be compartmentalized in the tissue to cause signal loss on spin echo images, a condition which may not be present in reperfused infarcted myocardium. Accordingly, nine rats were subjected to 2 h of left coronary artery occlusion followed by 3 +/- 0.5 h of reperfusion prior to administration of contrast media. Three sets of MR images were acquired: (a) baseline axial images at the midventricle, both T1-weighted (TR/TE = 300/20) and T2-weighted (TR/TE = 1500/60); (b) T1-weighted images after administering a T1-enhancing agent, Gd-DTPA-BMA (0.2 mmol/kg), to document that contrast media is delivered to the reperfused infarction; and (c) T2-weighted images after administering the susceptibility agent, Dy-DTPA-BMA (1.0 mmol/kg). Gadolinium-enhanced T1 images depicted reperfused infarction as regions with greatly enhanced signal intensity compared with uninfarcted myocardium, indicating that contrast agent was delivered to the infarcted zone. Dysprosium-enhanced T2 images depicted the injury as a region of persistent signal intensity relative to depletion of signal in normal myocardium, consistent with failure of the contrast agent to cause signal loss. Similar infarction sizes were observed for unenhanced T2-weighted images (33 +/- 5%), gadolinium-enhanced T1-weighted images (36 +/- 5%) and postmortem staining (30 +/- 6%); strong correlations (r > 0.9) were noted in comparisons of these data.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1994

Inversion recovery EPI of bolus transit in rat myocardium using intravascular and extravascular gadolinium-based MR contrast media: dose effects on peak signal enhancement.

Inversion recovery gradient recalled echo planar imaging (TI/TR/TE = 700/2000/10 ms) was used to dynamically monitor the first pass of an intravascular (GdDOTA-polylysine) and an extravascular (GdDTPA-BMA) contrast agent through normal rat myocardium. It was found that myocardial enhancement increased with dose of the intravascular agent to a limiting value of approximately 50% of fully relaxed intensity, consistent with enhancement of 40% of myocardial water content during the first pass. Larger doses produced no further increase in peak response. On the other hand, the extravascular agent caused incrementally increased enhancement throughout the dose range examined to a final value of 68 +/- 2% of fully relaxed intensity. The profile of dose dependence for both agents was inconsistent with monoexponential T1 relaxation. It was concluded that: (a) compartmentalization of myocardial water combined with restricted myocardial water diffusion limits the peak response during bolus transit; (b) extraction of the extravascular agent during transit elevates the peak response over that obtained from agent confined to the vascular volume; and (c) models that assume simple monoexponential T1 relaxation to derive time-density curves do not adequately describe the relationship between changes in signal intensity, R1 and contrast concentration.

Albumins↗
PubMed1994

Usefulness of magnetic resonance imaging for evaluating great-vessel anatomy after arterial switch operation for D-transposition of the great arteries.

Magnetic resonance imaging (MRI) produces high-resolution images of great-vessel anatomy in pediatric patients. In this study seven patients, aged 6 to 27 months were evaluated by using gated MRI and two-dimensional echocardiography 4 to 26 months after arterial switch operation for D-transposition of the great arteries. Measurements were taken at the right and left ventricular outflow tracts, beneath the semilunar valves, at the midaortic sinuses, at the anastomotic sites of the main pulmonary artery and the aorta, at the origin of the branch pulmonary arteries, and at the distal pulmonary arteries 1 cm beyond the bifurcation. Concordant results were obtained with both imaging techniques from all sides with the exception of the left pulmonary artery and the right pulmonary artery. With MRI, four patients had significant narrowing at the right pulmonary artery origin and six patients had narrowing at the left pulmonary artery origin. With two-dimensional echocardiogram, two patients had narrowing at the right pulmonary artery origin and four patients had narrowing at the left pulmonary artery origin. The measured pulmonary artery intraluminal diameters in these patients were consistently smaller when assessed by MRI versus two-dimensional echocardiography. To verify these results, five of seven patients underwent cardiac catheterization to provide physiologic correlation before reoperation; the MRI results were found to be significantly closer to the actual catheterization measurements. We conclude that MRI is a sensitive imaging technique for evaluation of great-vessel anatomy in patients after arterial switch operation for D-transposition of the great arteries. It is particularly useful in the evaluation of the branch pulmonary artery anatomy.

Aorta↗
PubMed1994

Evaluation of left atrial contribution to left ventricular filling in aortic stenosis by velocity-encoded cine MRI.

Velocity-encoded cine MRI (VEC-MRI) can measure volume flow at specified site in the heart. This study used VEC-MRI to measure flow across the mitral valve to compare the contribution of atrial systole to left atrial filling in normal subjects and patients with left ventricular hypertrophy. The study population consisted of 12 normal subjects (mean age 34.5 years) and nine patients with various degrees of left ventricular hypertrophy resulting from aortic stenosis (mean age 70 years). VEC-MRI was performed in double-oblique planes through the heart to measure both the mitral inflow velocity pattern (E/A ratio) and the volumetric flow across the mitral valve. The left atrial contribution to left ventricular filling (AC%) was calculated. The results were compared with Doppler echocardiographic parameters. The VEC-MRI-derived mitral E/A ratios showed a significant linear correlation with E/A ratios calculated from Doppler echocardiography (r = 0.94), and the VEC-MRI-derived E/A ratios (2.1 +/- 0.5 vs 1.0 +/- 0.4) and AC% values (24.9 +/- 7.2 vs 45.7 +/- 16.4) were significantly different between normal subjects and patients with aortic stenosis (p < 0.01 in both groups). The same differences were seen in the Doppler echocardiographic parameters. The VEC-MRI-derived E/A ratio and AC% showed significant hyperbolic and linear correlations with left ventricular mass indexes (r = 0.95 and 0.86). In addition, the VEC-MRI-determined E/A ratio and the volumetric AC% displayed a highly significant hyperbolic correlation (r = 0.95). Thus VEC-MRI can be used to evaluate left ventricular diastolic filling characteristics in normal subjects and patients with abnormalities of diastolic filling.

Adult↗
PubMed1994

Postoperative evaluation of pulmonary arteries in congenital heart surgery by magnetic resonance imaging: comparison with echocardiography.

Palliative and corrective operations for the treatment of cyanotic congenital heart disease frequently involve or potentially influence the size of the pulmonary arteries. Echocardiography and magnetic resonance imaging (MRI) are two noninvasive imaging techniques currently used to assess morphologic abnormalities of the pulmonary arteries. The purpose of this study was to evaluate the role of MRI in comparison with echocardiography for defining morphologic changes of the pulmonary arteries after congenital heart surgery. The MRI scans and echocardiograms of 33 patients with surgery involving or affecting the pulmonary arteries were compared. The pulmonary outflow tract, pulmonary confluence, right and left pulmonary arteries, and surgical shunts were separately evaluated. Cineangiography and surgical reports were used to confirm findings. MRI and echocardiography were equivalent for demonstrating abnormalities of the right ventricular outflow tract, main pulmonary artery, and a variety of pulmonary shunts. MRI was superior to echocardiography in demonstrating abnormalities of the right and left pulmonary arterial branches (p < 0.001). MRI is effective for monitoring pulmonary arterial status after surgery and is superior to echocardiography for the evaluation of the right and left pulmonary arteries.

Adolescent↗
PubMed1994

AUR Memorial Award. Identification of myocardial cell death in reperfused myocardial injury using dual mechanisms of contrast-enhanced magnetic resonance imaging.

RATIONALE AND OBJECTIVES: Because the magnitude of dysprosium-induced signal loss depends on the microheterogeneity of its distribution (exclusion from intracellular space), we proposed that loss of myocardial cell integrity would be reflected by decreased potency of dysprosium in the injured compared with normal myocardium. We measured the effect of dysprosium on magnetic resonance (MR) imaging signal intensity of reperfused infarcted and nonischemic myocardium and related it to tissue concentration of the contrast media. METHODS: Rats were subjected to 1 hr coronary artery occlusion followed by 1 hr reperfusion. After 45 min of reflow, group 1 (n = 9) received 1.0 and 0.2 mmol/kg dysprosium diethylenetriamine pentaacetic acid-bismethylamide (Dy-DTPA-BMA) and gadodiamide (Gd-DTPA-BMA), respectively. Group 2 (n = 7) received no contrast agents. Excised hearts were imaged with spin-echo T1- and T2-weighted sequences. After imaging, hearts were stained (triphenyltetrazolium chloride) to define the injured zones. Concentrations of Dy-DTPA-BMA and Gd-DPTA-BMA in regional myocardial tissue were determined by induction coupled plasma-atomic emission spectrometry. Separate groups received one or the other contrast medium alone to control for potential error from the mixed effects of the two agents. RESULTS: Gd-DTPA-BMA delineated reperfused infarcted myocardium as a bright zone on T1-weighted images, thus indicating delivery of the agent and reperfusion at the tissue level. Dy-DTPA-BMA delineated the reperfused infarction as a bright region by decreasing the signal intensity of nonischemic myocardium significantly more than that of injured myocardium, despite being present in greater concentration (by 2.46-fold) in the injured myocardium. CONCLUSION: These findings are consistent with the hypothesis that the failure of myocardial cells to exclude the dysprosium compound is responsible for the diminished potency of dysprosium to cause MR imaging signal intensity loss in reperfused myocardial infarction. The combination of the two contrast media may define reperfusion of the myocardium at the tissue level (Gadolinium distribution) and the presence and extent of myocardial necrosis (diminished dysprosium effect) in reperfused myocardial infarctions.

Animals↗
PubMed1994

Octreotide therapy in advanced thyroid cancer.

Octreotide is a long-acting somatostatin analog that inhibits cell growth and hormone secretion. It has been successfully used in the management of a variety of endocrine tumors (i.e., acromegaly, carcinoid tumors, gastrinomas). In vitro, octreotide suppresses adenylate cyclase activity, DNA synthesis, and cell growth in cultured thyroid cell lines. Previous studies examining the use of octreotide in the treatment of medullary thyroid cancers, in vivo, report symptomatic improvement from tumor-related hormonal hypersecretion; however, octreotide's ability to suppress tumor growth was limited. In the present study, we examine the efficacy of long-term octreotide administration in six subjects with metastatic thyroid carcinoma, including Hurthle cell (one subject), medullary (one subject) and papillary or mixed papillary/follicular cancer (four subjects). All of the subjects had documented recurrences of their thyroid tumors despite appropriate therapy, and were considered to be untreatable by conventional therapeutic modalities (i.e., radioiodine or surgery). Subjects were monitored while receiving relatively high doses (4 mg daily) octreotide subcutaneously for up to 12 months. Octreotide therapy was very well tolerated; mild gastrointestinal symptoms persisted throughout treatment in one subject. Octreotide did not significantly decrease tumor markers (e.g., thyroglobulin, calcitonin, carcinoembryonic antigen). The carcinomas progressed during treatment, as evidenced by an increase in the size and/or number of metastatic lesions. In summary, in this small series subcutaneous octreotide administration did not appear to be efficacious in the management of advanced thyroid cancers.

Aged↗
PubMed1994

Comparison of cardiovascular response to ionic and nonionic magnetic resonance susceptibility contrast agents.

RATIONALE AND OBJECTIVES: Bolus injection of magnetic resonance (MR) contrast media has been used in recent years to exploit the diagnostic advantage of newer fast MR imaging sequences. The bolus effects of three equimolar dosages of ionic and nonionic magnetic susceptibility contrast agents on several cardiovascular functional parameters are investigated in normal rats and in rats subjected to acute myocardial infarction. These results are related to the osmolalities of the injected solutions. METHODS: Four groups of rats were examined (n = 10 rats per group). Twenty normal rats were studied. Acute myocardial infarction was produced by ligating the anterior branch of the left coronary artery for 2 hours in another 20 rats. Sequential equimolar doses of 0.1, 0.3, and 0.5 mmol/kg of ionic dysprosium diethylenetriamine pentaacetic acid dimeglumine ([NMG]2DyDTPA) or nonionic dysporosium diethylenetriamine pentaacetic acid-bis-methylamide (DyDTPA-BMA) (sprodiamide injection) were administered intravenously into the left jugular vein as a bolus. Hemodynamic parameters (heart rate, left ventricular pressures, rate of rise of left ventricular pressure [+/- dP/dt], and electrocardiogram as well as central and peripheral pressures) were continuously monitored for 15 minutes after each dose. Left ventricular developed pressure and rate pressure product, as indicators of myocardial oxygen consumption, were calculated. Osmolalities of the injected solutions were determined from freezing-point depression and correlated with the observed hemodynamic alterations. RESULTS: Bolus administration of 0.1, 0.3, and 0.5 mmol/kg DyDTPA-BMA produced no significant effect on the various hemodynamic parameters. (NMG)2DyDTPA caused dose-dependent attenuations in heart rate, left ventricular pressures, +/- dP/dt, rate pressure product and arterial blood pressures in both normal and infarcted rats. The magnitude of the response was dose dependent. Significant correlations were observed between osmolality and peak change of hemodynamic variables (r values between 0.99-1.00) after the administration of (NMG)2DyDTPA, but not after the injection of DyDTPA-BMA. CONCLUSIONS: Bolus administration of (NMG)2DyDTPA resulted in transient negative inotropic and chronotropic effects and hypotension in both healthy and infarcted animals. DyDTPA-BMA, administered as a bolus even at high doses, caused no appreciable hemodynamic alterations.

Animals↗