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Biomedical subjects

C B Higgins

Publications and source records attributed to C B Higgins.

At least 181 records · Page 10Linked to original sources
PubMed1992

Amelioration of cardiodepressive effects of gadopentetate dimeglumine with addition of ionic calcium.

Doses of gadopentetate dimeglumine of 0.1-0.5 mmol/kg cause cardiodepressive effects when injected as a rapid central bolus into the left jugular vein. This study evaluated the hemodynamic effects of this magnetic resonance imaging contrast medium with and without calcium supplementation in a rat model. Also, the potential of gadopentetate dimeglumine to bind ionized serum calcium was investigated in vitro. Addition of calcium ions resulted in dose-dependent attenuation of the hemodynamic depression induced by gadopentetate dimeglumine alone. The cardiodepressive response was negated for a 0.1-mmol/kg dose of the contrast agent by addition of 6 mumol/kg of calcium, for a 0.3-mmol/kg dose by addition of 12 mumol/kg of calcium, and for a 0.5-mmol/kg dose by addition of 18 mumol/kg of calcium. Concentrations of 2 and 4 mmol/L of gadopentetate dimeglumine were found to bind 5.1% and 10.1% of the ionized calcium in rat serum under in vitro conditions, respectively.

Animals↗
PubMed1992

Severity of aortic regurgitation: interstudy reproducibility of measurements with velocity-encoded cine MR imaging.

The interstudy reproducibility of velocity-encoded cine (VEC) magnetic resonance (MR) imaging for quantification of regurgitant volume (RV) and regurgitant fraction (RF) was studied in 10 patients with chronic aortic regurgitation. Each patient underwent two VEC MR imaging studies. RV and RF were measured on the aortic flow curve by quantifying antegrade and retrograde flow per cardiac cycle. VEC MR imaging measurements for RV and RF correlated closely with volumetric measurements for both studies (r greater than .97). Interstudy reproducibility for VEC MR imaging measurement of RV and RF was high (r greater than .97), and the interstudy variability for VEC MR imaging measurements was low. These results demonstrate a high accuracy of VEC MR imaging for measurement of RV and RF in patients with chronic aortic regurgitation. The level of interstudy reproducibility of VEC MR imaging for quantitative assessment of RV and RF indicates the potential of this technique for follow-up and monitoring of response to therapy.

Adult↗
PubMed1992

MR measurement of blood flow in the cardiovascular system.

Methods for measurement of blood flow with MR were devised many years ago but have been used for diagnosis in only the past few years. The two methods of measurement that have been used most extensively are based on the principles of time of flight and phase shift. A number of factors can influence the accuracy of MR measurements of blood flow. In vitro studies using flow phantoms have verified the accuracy of the phase-shift technique for measuring flow velocities exceeding 5 m/sec, which for practical purposes, encompasses the peak flow encountered in cardiovascular disorders. The flow measurements have been used to quantify valvular heart disease, congenital heart disease, pulmonary arterial disease, thoracic aortic disease, and peripheral vascular disease.

Blood Flow Velocity↗
PubMed1991

Noninvasive determination of left ventricular output and wall stress in volume overload and in myocardial disease by cine magnetic resonance imaging.

The current study used cine magnetic resonance imaging to determine the effect of increasing severity of valvular regurgitation on systolic wall stress and to demonstrate that wall stress was disproportionately increased in relation to the severity of regurgitation in patients with myocardial disease. A total of 39 patients with predominantly mitral (n = 22) or aortic (n = 17) regurgitation with (n = 13) and without (n = 26) myocardial disease and 10 normal volunteers were examined with cine magnetic resonance imaging (MRI) at 1.5 T. Left ventricular (LV) cardiac output (CO) and peak systolic (PS) wall stress (WS) and end-systolic (ES) WS were calculated from blood pressure recordings, carotid pulse tracings, and wall thickness (h) and diameter (D) measurements obtained from cine MRI. Patients were classified into three degrees of severity according to their LV regurgitant volume (RV). Myocardial disease was defined by an ejection fraction (EF) of less than 40%. Mean LV EF was 61 +/- 3% in normal volunteers, 64 +/- 3% in patients with regurgitation, and 25 +/- 2% in patients with myocardial disease. LV CO was directly related to RV in patients without myocardial disease, whereas it was disproportionately low in relation to RV in patients with myocardial disease. PS WS was significantly higher in severe mitral and/or aortic regurgitation compared with moderate, mild, and no mitral and/or aortic regurgitation. Compared with the degree of regurgitation, PS WS was disproportionately higher in patients with myocardial disease. Thus LV CO and WS rise progressively with increasing severity of regurgitation. Disproportionately high systolic WS relative to RV indicates the presence of myocardial disease.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1991

Left atrial volume determination by biplane two-dimensional echocardiography: validation by cine computed tomography.

Left atrial (LA) volume measurements have been made by the application of the method of discs (modified Simpson's rule) to orthogonal biplane atrial echocardiographic images. Validation of the technique has been suboptimal due to deficiencies of the reference standard, levophase angiography. To define the accuracy of echocardiography, we compared LA end-systolic volume by echocardiography in 27 patients with volumes by cine computed tomography (Cine CT), a highly accurate and validated method of measuring cardiac chambers. Echocardiographic tracings were made in the apical long-axis two- and four-chamber views. In patients with atria less than 300 ml, 14 had echoes performed prospectively, with optimization of LA size, while the remaining 10 were analyzed retrospectively. The volume of each slice was calculated and was then summated to obtain total volume. The correlation coefficient between two-dimensional echocardiography and Cine CT was r = 0.98, and it was r = 0.82 when patients with atria greater than 300 ml (n = 3) were excluded. Echocardiography underestimated Cine CT measurements by 23%. The slope of the prospective group was closer to unity than the slope of the retrospective group (p less than 0.001), and the correlation with Cine CT was slightly better for the prospective group (r = 0.88 versus r = 0.77). LA volume by two-dimensional echocardiography correlates closely with Cine CT, a more accurate method of volume determination, and gives valid measurements of LA volume. Efforts to maximize LA size during scanning limit inaccuracies of echocardiographic measurements of the left atrium.

Echocardiography↗
PubMed1991

Assessment of right ventricular diastolic and systolic function in patients with dilated cardiomyopathy using cine magnetic resonance imaging.

Cine magnetic resonance imaging (MRI) can provide clear endocardial margins of the entire right ventricle, and Simpson's algorithm can be applied to obtain the volumes at multiple phases of the cardiac cycle. Time-volume curves of the right ventricle were obtained by using cine MRI in 10 patients with dilated cardiomyopathy (DCM) and eight normal volunteers to assess right ventricular function. There were no significant differences in volumes and ejection fraction of the right ventricle between the group with DCM and the normal group. In the group with DCM the time to peak filling rate was increased (p less than 0.05) and the filling fraction was decreased (p less than 0.01). In the patients with DCM cine MRI demonstrated normal volumes and ejection fraction of the right ventricle in contradistinction to the marked increase in volumes and the decrease in ejection fraction of the left ventricle; with the use of time-volume curves of the right ventricle, impairment of diastolic function of the right ventricle was demonstrated.

Adult↗
PubMed1991

Nuclear magnetic resonance imaging of the palliative operation for hypoplastic left heart syndrome.

Electrocardiographic-gated nuclear magnetic resonance (NMR) imaging has been shown to be effective for the evaluation of congenital heart disease, particularly in supracardiac regions. This study evaluated the postoperative status after a stage I palliative operation (Norwood procedure) for hypoplastic left heart syndrome. The NMR images from three patients were compared with those of angiography and depicted all components of the reconstructed supracardiac and intracardiac anatomy after this operation. Nonobstructive anastomosis of the main pulmonary artery to the proximal aorta was clearly demonstrated in each patient. The caliber of the central or branch pulmonary artery, patency and caliber of the systemic to pulmonary artery shunt and the size of the atrial communication were also depicted in each patient and these findings corresponded with angiographic results. The results suggest that NMR imaging is effective for assessing the results of initial palliative surgery for hypoplastic left heart syndrome, which seems to be important for managing patients before subsequent definitive surgery.

Anastomosis, Surgical↗
PubMed1991

Evaluation of right ventricular early diastolic filling by cine nuclear magnetic resonance imaging in patients with hypertrophic cardiomyopathy.

Numerous studies have established abnormalities in systolic and diastolic function of the left ventricle in hypertrophic cardiomyopathy. A consistent feature of this disease is reduced diastolic function of the left ventricle, but little information is available regarding right ventricular function in this disease. Cine nuclear magnetic resonance (NMR) imaging has been found to be effective for measuring right ventricular volumes and therefore was used to assess early diastolic filling of the right ventricle in patients with hypertrophic cardiomyopathy. Right ventricular time-volume curves were obtained from cine NMR images in 10 patients with hypertrophic cardiomyopathy and 8 normal subjects. Right ventricular volume was calculated with use of Simpson's algorithm at approximately 18 phases of the cardiac cycle and, from the curve, peak filling rate and filling fraction during the first third of diastole were determined. In patients with hypertrophic cardiomyopathy, peak filling rate tended to be less (176 +/- 46 vs. 305 +/- 50 ml/s, p less than 0.01) and filling fraction decreased (39.5 +/- 13.8 vs. 74.5 +/- 13.3%, p less than 0.01) in comparison with values in normal subjects. Thus, analysis of right ventricular time-volume curves obtained by using cine NMR imaging demonstrated diastolic dysfunction of the right ventricle in hypertrophic cardiomyopathy.

Adult↗
PubMed1991

Normal and diffusely abnormal myocardium in humans: functional and metabolic characterization with P-31 MR spectroscopy and cine MR imaging.

The current study tested the concept that cine magnetic resonance (MR) imaging and phosphorus-31 MR spectroscopy might be used to provide a comprehensive evaluation of the functional and metabolic status of the myocardium in humans. Thirteen patients with congestive cardiomyopathy and eight healthy volunteers were imaged at 1.5 T with the one-dimensional chemical shift imaging technique for localization of P-31 MR spectroscopy and an electrocardiographically referenced gradient refocused sequence for imaging of the heart. Prominent peaks in the PDE and PME regions were observed in cardiomyopathic patients, but only the former peak was measured. The PCr/beta-ATP peak ratio was not significantly lower in cardiomyopathic patients compared with healthy subjects (1.51 +/- 0.08 vs 1.54 +/- 0.04). The ratios of PDE/PCr (0.80 +/- 0.07 vs 0.54 +/- 0.10) (P less than or equal to .01) and PDE/beta-ATP (1.19 +/- 0.10 vs 0.84 +/- 0.08) (P less than or equal to .05) were significantly higher in patients with dilated cardiomyopathy compared with healthy volunteers. Left ventricular systolic wall thickening was significantly lower and left ventricular peak and end-systolic wall stress and mass were significantly higher in cardiomyopathic patients compared with healthy volunteers. Thus, localized, gated P-31 MR spectroscopy combined with cine MR imaging allowed identification of both abnormal myocardial phosphate metabolism and abnormal ventricular function. While this study suggests that increased myocardial PDEs may be a marker for abnormal myocardium, the sensitivity and specificity of this marker need to be further evaluated.

Adenosine Triphosphate↗
PubMed1991

Myocardial infarction: assessment with an intravascular MR contrast medium. Work in progress.

The effect of a new intravascular magnetic resonance (MR) contrast medium (gadolinium diethylenetriaminepentaacetic acid [DTPA] polylysine) was evaluated in acute, subacute, and chronic myocardial infarctions in rats. Signal intensity (SI) was measured before and after intravenous administration of Gd-DTPA polylysine. Before administration of contrast material, chronic infarctions had lower SI than normal myocardium. With Gd-DTPA polylysine, three zones were identified in acute and subacute stages of myocardial infarction, but in the chronic stage, images demonstrated two zones. In acute and subacute infarctions, Gd-DTPA polylysine produced greater enhancement (over 60 minutes) in the peri-infarction zone than in the normal or infarcted myocardium. In chronic infarctions, Gd-DTPA polylysine had no discernible effect on the SI of the central infarction zone. Overall, it caused no significant hemodynamic effects. MR imaging with Gd-DTPA polylysine produced differential tissue enhancement in myocardial infarctions, which varied according to the age of the infarction.

Animals↗
PubMed1991

Right and left lung perfusion: in vitro and in vivo validation with oblique-angle, velocity-encoded cine MR imaging.

Quantification of pulmonary flow is clinically important in the evaluation of both congenital and acquired heart disease. Velocity-encoded cine magnetic resonance (MR) is a promising technique for measuring velocity and volume of blood flow. The authors report validation of the accuracy of velocity-encoded cine MR for measurement of oblique-angle flow in vitro, with use of a constant-flow phantom, and in vivo, with nine healthy volunteers in whom velocities were measured separately in the main, right, and left pulmonary arteries. Findings at MR were compared with findings at Doppler echocardiography. Velocity measurements in a flow phantom with cine MR correlated well with direct measurements at Doppler echocardiography. Velocity-encoded cine MR enabled accurate and reproducible measurement of absolute blood flow in healthy subjects. Oblique-gradient flow encoding (ie, flow-encoding direction coinciding with the true direction of flow) was the method of choice for velocity measurements in the right and left pulmonary arteries.

Adult↗
PubMed1991

Occlusive and reperfused myocardial infarcts: MR imaging differentiation with nonionic Gd-DTPA-BMA.

To increase the time during which effective contrast exists between normal and infarcted myocardium, a high dose (0.6 mmol/kg) of the nonionic contrast medium gadolinium diethylenetriaminepentaacetic acid bismethylamide (Gd-DTPA-BMA) was used to distinguish between occlusive and reperfused myocardial infarctions in rats. After administration of Gd-DTPA-BMA, there was clear and persistent demarcation of both occlusive and reperfused infarcts on T1-weighted MR images. In occlusive infarcts, normal, infarcted, and periinfarcted myocardium could be identified. High signal intensity was evident for 60 minutes in a band straddling the border between infarcted and normal myocardium, namely, the periinfarction zone. In the reperfused infarct, normal and infarcted myocardium could be identified. The reperfused zone was immediately enhanced after injection of Gd-DTPA-BMA. A differential pattern of enhancement between occlusive and reperfused myocardial infarcts was evident for 1 hour. Thus, Gd-DTPA-BMA has the potential to allow (a) depiction of occlusive and reperfused acute myocardial infarcts, (b) documentation of reperfusion of myocardial infarction, and (c) distinction between occlusive and reperfused infarction.

Animals↗
PubMed1991

Abnormalities of the pulmonary veins: evaluation with MR imaging and comparison with cardiac angiography and echocardiography.

Seventy-seven patients underwent T1-weighted spin-echo magnetic resonance (MR) imaging. Group 1 (n = 56) consisted of patients with various types of congenital heart disease but normal pulmonary veins. Group 2 (n = 22) consisted of patients with the following conditions: partial anomalous pulmonary venous connection (n = 11), total anomalous pulmonary venous connection (n = 5), cor triatriatum (n = 4), or pulmonary vein stenosis (n = 2). In group 1, the sites of connections of all four pulmonary veins were identified with MR imaging in 88% of cases; the connections of at least three pulmonary veins were seen in all patients. In group 2, the prospective detection rate of pulmonary venous abnormalities with MR imaging was 95%. The prospective detection rates of pulmonary venous abnormalities with cardiac angiography (n = 13) and echo-cardiography (n = 13) were 69% and 38%, respectively. This study indicates that MR imaging can accurately demonstrate the normal pulmonary veins and abnormalities of the pulmonary veins.

Adolescent↗