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Biomedical subjects

Vincent B Ho

Publications and source records attributed to Vincent B Ho.

At least 19 recordsLinked to original sources
PubMed2006

Growth hormone treatment and aortic dimensions in Turner syndrome.

BACKGROUND: In recent years many girls with Turner syndrome (TS) have been treated with supraphysiological doses of GH to increase adult height. In addition to promoting statural growth, GH may have direct effects on the cardiovascular system. OBJECTIVE: We sought to determine whether GH treatment affects aortic diameter in girls with TS because there is an increased risk for aortic dilation and dissection in this syndrome. METHODS: In a retrospective, cross-sectional study, we compared ascending and descending aortic diameters measured by magnetic resonance imaging in GH-treated (n = 53) vs. untreated (n = 48) patients with TS participating in a National Institutes of Health protocol between 2001 and 2004. RESULTS: The average duration of GH treatment was 4.7 with se 0.4 yr (range 2-11 yr). The two groups were similar in age and weight, but GH-treated subjects were on average 8 cm taller (P = 0.002). The diameter of the ascending aorta was increased by 7.3% and descending aorta by 8.9% in the GH-treated group. However, after correction for age, height, weight, and presence of bicuspid aortic valve and coarctation, using a multiple regression, neither history of GH treatment nor the length of GH treatment had an effect on the aortic diameter. Weight (P = 0.02), height (P = 0.001), and presence of bicuspid aortic valve (P = 0.0001) were associated with larger ascending aortic diameter, whereas age (P = 0.008), height (P = 0.02), and history of coarctation (P = 0.006) were associated with larger descending aortic diameter. CONCLUSIONS: GH treatment of girls with TS does not seem to affect ascending or descending aortic diameter above the increase related to the larger body size.

Adolescent↗
PubMed2006

Prolongation of the cardiac QTc interval in Turner syndrome.

Anatomic anomalies of the cardiovascular system occur in approximately 50% of individuals with Turner syndrome (TS), with the specific genetic cause(s) for the heart defects still unknown. Because congenital heart disease may be associated with conduction system abnormalities, we compared electrocardiograms (ECGs) in 100 women with TS and 100 age-matched female controls. Women with TS were significantly more likely to demonstrate left posterior fascicular block (p < 0.005), accelerated AV conduction (p < 0.006), and T wave abnormalities (p < 0.006). The PR interval was significantly shorter (137 +/- 17 vs. 158 +/- 18 ms, p < 0.0001) and the rate-corrected QT interval (QTc) significantly longer in women with TS than in controls (423 +/- 19 ms vs. 397 +/- 18 ms; p < 0.0001). Twenty-one women with TS but no controls had a QTc greater than 440 ms. We found no statistically significant relation between body habitus, cardiac dimensions, evidence of congenital heart disease, or metabolic parameters and the incidence of ECG abnormalities or QTc duration in TS. Cardiac conduction and repolarization abnormalities appear to be intrinsic features of TS, suggesting that deletion of the second sex chromosome has more profound effects on the cardiovascular system than previously recognized, and that ECG analysis should be included in evaluating and monitoring patients with Turner syndrome.

Adolescent↗
PubMed2005

Feasibility of integrating high-spatial-resolution 3D breath-hold coronary MR angiography with myocardial perfusion and viability examinations.

The study was institutional review board approved and Health Insurance Portability and Accountability Act compliant. All subjects provided informed consent. Three-dimensional breath-hold coronary magnetic resonance (MR) angiography with use of steady-state free precession was performed in 12 patients up to 20 minutes after 0.2 mmol gadolinium-based contrast material per kilogram of body weight was administered. Within 24 heartbeats, a spatial resolution of up to 1.0 x 1.2 x 2.0 mm was achieved. Sixty-five (82%) of the 79 visualized coronary artery segments had a grade of 3 or 4 on a four-point scale of depiction in which grade 4 indicated excellent depiction. Twenty-seven percent (n = 21) of the 79 segments were assigned a grade of 4; 56% (n = 44), a grade of 3; 16% (n = 13), a grade of 2; and 1% (n = 1), a grade of 1. Coronary MR angiography performed as part of a first-pass myocardial perfusion and viability assessment MR imaging examination is feasible and does not involve additional imaging time.

Adult↗
PubMed2005

Association between fetal lymphedema and congenital cardiovascular defects in Turner syndrome.

OBJECTIVES: Turner syndrome (TS) is associated with congenital cardiovascular defects (CCVDs), most commonly bicuspid aortic valve (BAV) and aortic coarctation (COARC), congenital renal anomalies, and fetal lymphedema. It has been theorized that compressive or obstructive effects of fetal lymphedema may actually cause cardiovascular and renal dysmorphogenesis in TS. The objective of this study was to determine whether there is a specific association between a history of fetal lymphedema and CCVDs in monosomy X, or TS, independent of karyotype or general severity of the phenotype. METHODS: This was a prospective study of 134 girls and women who have TS (mean age: 30 years) and were clinically evaluated for evidence of fetal lymphedema, classified as central (signified by the presence of neck webbing) or peripheral (current or perinatal, or dysplastic fingernails). The presence of BAV and/or COARC was detected by magnetic resonance imaging combined with echocardiography, and renal anomalies were determined by ultrasound. RESULTS: There is a strong association between developmental central lymphedema, signified by neck webbing, and the presence of BAV (chi2 = 10) and COARC (chi2 = 8). The association between webbed neck and CCVDs was independent of karyotype. There was, in contrast, no significant association between renal anomalies and webbed neck or CCVDs. CONCLUSIONS: The strong, statistically significant association between neck webbing and the presence of BAV and COARC in TS suggests a pathogenetic connection between fetal lymphatic obstruction and defective aortic development. The presence of neck webbing in TS should alert the clinician to the possibility of congenital cardiovascular defects.

Adult↗
PubMed2004

Major vascular anomalies in Turner syndrome: prevalence and magnetic resonance angiographic features.

BACKGROUND: Turner syndrome (TS) is associated with aortic coarctation and dissection; hence, echocardiographic evaluation of all patients is currently recommended. X-ray angiography in clinically symptomatic patients has suggested a range of other vascular anomalies, but the true prevalence of such lesions in TS is unknown. To better understand the prevalence and pathogenesis of cardiovascular defects in TS, we prospectively evaluated a group of asymptomatic adult volunteers with TS using magnetic resonance (MR) angiography. METHODS AND RESULTS: A total of 85 adults with TS and 27 normal female adult volunteers underwent gadolinium-enhanced 3D MR angiography. A high prevalence of aortic anomalies was seen in women with TS, including elongation of the transverse arch (49%), aortic coarctation (12%), and aberrant right subclavian artery (8%). Venous anomalies were also prominent, including persistent left superior vena cava (13%) and partial anomalous pulmonary venous return (13%). None of these anomalies were found in healthy female controls. The constellation of elongation of the transverse arch, aortic coarctation, and persistent left superior vena cava was significantly associated with women with TS. Neck webbing and increased thoracic anterior-to-posterior dimension diameters were strong predictors for arterial and venous anomalies. CONCLUSIONS: Thoracic vascular anomalies are common in TS, occurring in approximately 50% of a group not preselected for cardiovascular disease. The highly significant association between neck webbing, increased chest diameter, and these vascular anomalies suggests that in utero, centrally localized lymphatic obstruction may contribute to these cardiovascular deformities in TS. Improved recognition of these often-undetected vascular lesions may be important for identification of patients in need of closer cardiovascular monitoring.

Adult↗
PubMed2004

Estimation of the differential pressure at renal artery stenoses.

Atherosclerotic disease of the renal artery can lead to reduction in arterial caliber and ultimately to conditions including renovascular hypertension. Renal artery stenosis is conventionally assessed, using angiography, according to the severity of the stenosis. However, the severity of a stenosis is not a reliable indicator of functional significance, or associated differential pressure, of a stenosis. A methodology is proposed for estimation of the renal artery differential pressure (RADP) from MR imaging. Realistic computational fluid dynamics (CFD) models are constructed from MR angiography (MRA) and phase-contrast (PC) MR. The CFD model is constructed in a semiautomated manner from the MR images using the Isosurface Deformable Model (IDM) for surface reconstruction and a Marching Front algorithm for construction of the volumetric CFD mesh. Validation of RADP estimation was performed in a realistic physical flow-through model. Under steady flow, the CFD estimate of the differential pressure across a stenosis in the physical flow-through model differed by an average of 5.5 mmHg from transducer measurements of the pressure differential, for differential pressures less than 60 mmHg. These results demonstrate that accurate estimates of differential pressure at stenoses may be possible based only on structural and flow images.

Arteriosclerosis↗
PubMed2004

MR evaluation of solid renal masses.

After diagnosis of a suspicious renal mass on ultrasound or CT, renal MR imaging typically is ordered to characterize the mass further, stage the mass, or resolve discordant ultrasound and CT results. MR imaging may also be ordered in cases in which ultrasound is poor or in instances in which contrast-enhanced CT may be ill advised.

Carcinoma, Renal Cell↗
PubMed2003

Multicenter phase-II trial of safety and efficacy of NC100150 for steady-state contrast-enhanced peripheral magnetic resonance angiography.

The aim of this study was to test the safety and efficacy of NC100150 injection for steady-state contrast-enhanced peripheral MR angiography in a multicentre phase-II trial. Thirty-three patients underwent steady-state NC100150 enhanced MR angiography (5 mg Fe/kg body weight) of the aortoiliac and femoropopliteal arteries. Safety assessment consisted of pre- and post-injection (2, 24 and 72 h) monitoring of vital signs, physical examination as well as laboratory and electrocardiographic parameters. To determine sensitivity and specificity for detection of haemodynamically significant stenoses (HSS; >50% reduction of luminal diameter) MR angiograms were compared with intra-arterial digital subtraction angiography (IA DSA), which was considered the standard of reference. In 33 patients a mean of 12.8 ml NC100150 was injected. Eleven patients reported 13 mild and 2 moderate adverse events. Five mild and one moderate adverse event were considered due to NC100150 injection. There were no significant changes in vital signs, laboratory or electrocardiographic parameters. Sensitivity and specificity (in percent) for detection of HSS were 87 and 64, 56 and 76, and 75 and 84, for iliac, femoral and popliteal arteries, respectively. NC100150 high-resolution steady-state MR angiography can be performed safely and is feasible for the detection of peripheral arterial HSS, but is as yet not a clinically useful alternative to conventional gadolinium-enhanced MR angiography.

Angiography, Digital Subtraction↗
PubMed2003

MR angiography of the abdominal aorta and peripheral vessels.

Contrast-enhanced MRA can be an accurate and reliable method for the arterial evaluation of the abdominal aorta and peripheral vessels. This technique can be adapted for a variety of anatomic regions. The basic issues relate to proper synchronization of imaging with peak arterial enhancement and to optimization of voxel dimensions for adequate depiction of the arterial structures.

Aorta, Abdominal↗
PubMed2003

MRA of the thoracic vessels.

Magnetic resonance imaging (MRI) is well suited for the noninvasive evaluation of the thoracic vasculature, and with improvements in scanner technology, the ability of MR to illustrate the thoracic vessels has significantly improved. Dedicated vascular software and pulse sequences have become commercially available, and fast imaging, in particular, has facilitated the time-efficient and comprehensive MR evaluation of most thoracic vascular lesions. Over the years, a host of black and bright blood MRI methods have evolved into practical tools for illustration of the thoracic vessels. As with other MR applications, successful vascular depiction relies significantly on the proper selection and prescription of imaging pulse sequences. In this article, these methods with their specific technical and practical pitfalls for thoracic magnetic resonance angiography (MRA) will be discussed. Current clinical indications for thoracic MRA will also be illustrated.

Aortic Diseases↗
PubMed2003

Isosurfaces as deformable models for magnetic resonance angiography.

Vascular disease produces changes in lumenal shape evident in magnetic resonance angiography (MRA). However, quantification of vascular shape from MRA is problematic due to image artifacts. Prior deformable models for vascular surface reconstruction primarily resolve problems of initialization of the surface mesh. However, initialization can be obtained in a trivial manner for MRA using isosurfaces. We propose a methodology for deforming the isosurface to conform to the boundaries of objects in the image with minimal a priori assumptions of object shape. As in conventional methods, external forces attract the surface toward edges in the image. However, smoothing is produced by a moment that aligns the normals of adjacent surface triangles. Notably, the moment produces no translational motion of surface triangles. The deformable isosurface was applied to a digital phantom of a stenotic artery, to MRA of three renal arteries with atherosclerotic disease and MRA of one carotid artery with atherosclerotic disease. Results of the surface reconstruction from the deformable model were compared with conventional X-ray angiography for the renal arteries. Measurement of the degree of stenosis of the renal arteries was within 12% +/- 6%. The deformable model provided improvements over the isosurface in all cases in terms of measurement of the degree of stenosis or improving the surface smoothness.

Algorithms↗