157 research outputs found
Relationship between cardiac diffusion tensor imaging parameters and anthropometrics in healthy volunteers
Background: In vivo cardiac diffusion tensor imaging (cDTI) is uniquely capable of interrogating laminar myocardial dynamics non-invasively. A comprehensive dataset of quantative parameters and comparison with subject anthropometrics is required.
Methods: cDTI was performed at 3T with a diffusion weighted STEAM sequence. Data was acquired from the mid left ventricle in 43 subjects during the systolic and diastolic pauses. Global and regional values were determined for fractional anisotropy (FA), mean diffusivity (MD), helix angle gradient (HAg, degrees/%depth) and the secondary eigenvector angulation (E2A). Regression analysis was performed between global values and subject anthropometrics.
Results: All cDTI parameters displayed regional heterogeneity. The RR interval had a significant, but clinically small effect on systolic values for FA, HAg and E2A. Male sex and increasing left ventricular end diastolic volume were associated with increased systolic HAg. Diastolic HAg and systolic E2A were both directly related to left ventricular mass and body surface area. There was an inverse relationship between E2A mobility and both age and ejection fraction.
Conclusions: Future interpretations of quantitative cDTI data should take into account anthropometric variations observed with patient age, body surface area and left ventricular measurements. Further work determining the impact of technical factors such as strain and SNR is required
Apheresis as novel treatment for refractory angina with raised lipoprotein(a): a randomised controlled trial
Aims To determine the clinical impact of lipoprotein apheresis in patients with refractory angina and raised lipoprotein(a)ā>ā500āmg/L on the primary end point of quantitative myocardial perfusion, as well as secondary end points including atheroma burden, exercise capacity, symptoms, and quality of life. Methods We conducted a single-blinded randomized controlled trial in 20 patients with refractory angina and raised lipoprotein(a)ā>ā500āmg/L, with 3āmonths of blinded weekly lipoprotein apheresis or sham, followed by crossover. The primary endpoint was change in quantitative myocardial perfusion reserve (MPR) assessed by cardiovascular magnetic resonance. Secondary endpoints included measures of atheroma burden, exercise capacity, symptoms and quality of life. Results The primary endpoint, namely MPR, increased following apheresis (0.47; 95% CI 0.31ā0.63) compared with sham (ā0.16; 95% CIāāā0.33ā0.02) yielding a net treatment increase of 0.63 (95% CI 0.37ā0.89; Pā<ā0.001 between groups). Improvements with apheresis compared with sham also occurred in atherosclerotic burden as assessed by total carotid wall volume (Pā<ā0.001), exercise capacity by the 6āmin walk test (Pā=ā0.001), 4 of 5 domains of the Seattle angina questionnaire (all Pā<ā0.02) and quality of life physical component summary by the short form 36 survey (Pā=ā0.001). Conclusion Lipoprotein apheresis may represent an effective novel treatment for patients with refractory angina and raised lipoprotein(a) improving myocardial perfusion, atheroma burden, exercise capacity and symptoms
Myocardial Architecture, Mechanics, and Fibrosis in Congenital Heart Disease
Congenital heart disease (CHD) is the most common category of birth defect, affecting 1% of the population and requiring cardiovascular surgery in the first months of life in many patients. Due to advances in congenital cardiovascular surgery and patient management, most children with CHD now survive into adulthood. However, residual and postoperative defects are common resulting in abnormal hemodynamics, which may interact further with scar formation related to surgical procedures. Cardiovascular magnetic resonance (CMR) has become an important diagnostic imaging modality in the long-term management of CHD patients. It is the gold standard technique to assess ventricular volumes and systolic function. Besides this, advanced CMR techniques allow the acquisition of more detailed information about myocardial architecture, ventricular mechanics, and fibrosis. The left ventricle (LV) and right ventricle have unique myocardial architecture that underpins their mechanics; however, this becomes disorganized under conditions of volume and pressure overload. CMR diffusion tensor imaging is able to interrogate non-invasively the principal alignments of microstructures in the left ventricular wall. Myocardial tissue tagging (displacement encoding using stimulated echoes) and feature tracking are CMR techniques that can be used to examine the deformation and strain of the myocardium in CHD, whereas 3D feature tracking can assess the twisting motion of the LV chamber. Late gadolinium enhancement imaging and more recently T1 mapping can help in detecting fibrotic myocardial changes and evolve our understanding of the pathophysiology of CHD patients. This review not only gives an overview about available or emerging CMR techniques for assessing myocardial mechanics and fibrosis but it also describes their clinical value and how they can be used to detect abnormalities in myocardial architecture and mechanics in CHD patients
Use of the intravascular contrast agent NC100150 Injection in spin echo and gradient echo imaging of the heart
This
is
the
first
study of
the intravascular iron oxide particle contrast agent,
NC100150
Injection
(Nycomed
Imaging
AS,
Oslo,
Norway,
a
part
of
Nycomed
Amersham)
in magnetic
resonance
imaging
of
the
human
heart.
Eighteen healthy male volunteers
were studied
at both
0.5
and
1.5
T
before
and
after
the
administration
of
NC100150
Injection. Transaxial spin-echo images
were acquired at
both
field strengths, conventional gradient-echo cine images at
0.5
T,
and
breathhold Turbo-FLASH cine
images at
1.5
T.
Optimized
cine imaging sequences were
used
postcontrast, with
a
high
flip
angle
of
60-70ā.
In
the
spin-echo images there was
a
significant reduction
in
the
blood
pool
flow
artifact at
the
level
of
the right
atrium
(0.5
T,
57%,
p
<
0.01;
1.5
41%.
p
=
0.01)
and
the
left
ventricle
(LV)
(0.5
T,
45%,
p
=
0.01;
1.5
T,
45%,
p
<
0.01).
In
the
conventional gradient-echo cines
at
0.5
T,
there
was
a significant
increase
in
the
LV
blood
pool
and
myocardial
signal
difference-to-noise
ratio
(SDNR)
in
the diastolic
(56%,
p
=
0.01)
and
systolic
(141%,
p
<
0.OOl)frames. There
was
also
a
significant
increase
in
the signal
intensity
(SI)
gradient
at
the
LV
blood
pool-myocardial border in
the
diastolic
and
systolicframes (both
p
<
0.001).
At
higher doses
of
NClOO150
Injection
(3
and
4
mg/kg),
a
rim
of
signal
void
around the
LV
blood
pool
was observed, perfectly
defining
the
LV
blood
pool-
myocardial
border.
In
the
Turbo-FLASH breathhold cines
at
1.5
T,
there was
a
significant
increase
in
the
LV
blood pool-myocardial
SDNR
in the diastolic
(221%,
p
<
0.001)
and
systolic
(916%,
p
<
0.001)
frames.
Again,
there was
also
a
significant increase
in
the
SI
gradient
at
the
LV
blood
pool-
myocardial border in
the
diastolic and
systolicframes
(both
p
=
0.003).
In
conclusion,
NC100150
Injection
was given safely
to
18
healthy subjects. Image quality
and
LV
blood
pool-myocardial definition
were
improved
after
the
administration
of
NClOOI50 Injection. These improvements enable better spin-echo anatomical
defiition,
better
definition
of
myocardial
wall
motion,
and
should
improve
the
capability
of
automated edge
detection algorithms
Assessment of myocardial microstructural dynamics by in vivo diffusion tensor cardiac magnetic resonance
Background: Cardiomyocytes are organized in microstructures termed sheetlets that reorientate during left ventricular thickening. Diffusion tensor cardiac magnetic resonance (DT-CMR) may enable noninvasive interrogation of in vivo cardiac microstructural dynamics. Dilated cardiomyopathy (DCM) is a condition of abnormal myocardium with unknown sheetlet function.
Objectives: This study sought to validate in vivo DT-CMR measures of cardiac microstructure against histology, characterize microstructural dynamics during left ventricular wall thickening, and apply the technique in hypertrophic cardiomyopathy (HCM) and DCM.
Methods: In vivo DT-CMR was acquired throughout the cardiac cycle in healthy swine, followed by in situ and ex vivo DT-CMR, then validated against histology. In vivo DT-CMR was performed in 19 control subjects, 19 DCM, and 13 HCM patients.
Results: In swine, a DT-CMR index of sheetlet reorientation (E2A) changed substantially (E2A mobility ā¼46Ā°). E2A changes correlated with wall thickness changes (in vivo r2 = 0.75; in situ r2 = 0.89), were consistently observed under all experimental conditions, and accorded closely with histological analyses in both relaxed and contracted states. The potential contribution of cyclical strain effects to in vivo E2A was ā¼17%. In healthy human control subjects, E2A increased from diastole (18Ā°) to systole (65Ā°; p < 0.001; E2A mobility = 45Ā°). HCM patients showed significantly greater E2A in diastole than control subjects did (48Ā°; p < 0.001) with impaired E2A mobility (23Ā°; p < 0.001). In DCM, E2A was similar to control subjects in diastole, but systolic values were markedly lower (40Ā°; p < 0.001) with impaired E2A mobility (20Ā°; p < 0.001).
Conclusions: Myocardial microstructure dynamics can be characterized by in vivo DT-CMR. Sheetlet function was abnormal in DCM with altered systolic conformation and reduced mobility, contrasting with HCM, which showed reduced mobility with altered diastolic conformation. These novel insights significantly improve understanding of contractile dysfunction at a level of noninvasive interrogation not previously available in humans
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The influence of the atmospheric boundary layer on nocturnal layers of noctuids and other moths migrating over southern Britain
Insects migrating at high altitude over southern Britain have been continuously monitored by automatically-operating, vertical-looking radars over a period of several years. During some occasions in the summer months, the migrants were observed to form well-defined layer concentrations, typically at heights of 200-400 m, in the stable night-time atmosphere. Under these conditions, insects are likely to have control over their vertical movements and are selecting flight heights which are favourable for long-range migration. We therefore investigated the factors influencing the formation of these insect layers by comparing radar measurements of the vertical distribution of insect density with meteorological profiles generated by the UK Met. Officeās Unified Model (UM). Radar-derived measurements of mass and displacement speed, along with data from Rothamsted Insect Survey light traps provided information on the identity of the migrants. We present here three case studies where noctuid and pyralid moths contributed substantially to the observed layers. The major meteorological factors influencing the layer concentrations appeared to be: (a) the altitude of the warmest air, (b) heights corresponding to temperature preferences or thresholds for sustained migration and (c), on nights when air temperatures are relatively high, wind-speed maxima associated with the nocturnal jet. Back-trajectories indicated that layer duration may have been determined by the distance to the coast. Overall, the unique combination of meteorological data from the UM and insect data from entomological radar described here show considerable promise for systematic studies of high-altitude insect layering
Heart valve disease: investigation by cardiovascular magnetic resonance
Cardiovascular magnetic resonance (CMR) has become a valuable investigative tool in many areas of cardiac medicine. Its value in heart valve disease is less well appreciated however, particularly as echocardiography is a powerful and widely available technique in valve disease. This review highlights the added value that CMR can bring in valve disease, complementing echocardiography in many areas, but it has also become the first-line investigation in some, such as pulmonary valve disease and assessing the right ventricle. CMR has many advantages, including the ability to image in any plane, which allows full visualisation of valves and their inflow/outflow tracts, direct measurement of valve area (particularly for stenotic valves), and characterisation of the associated great vessel anatomy (e.g. the aortic root and arch in aortic valve disease). A particular strength is the ability to quantify flow, which allows accurate measurement of regurgitation, cardiac shunt volumes/ratios and differential flow volumes (e.g. left and right pulmonary arteries). Quantification of ventricular volumes and mass is vital for determining the impact of valve disease on the heart, and CMR is the 'Gold standard' for this. Limitations of the technique include partial volume effects due to image slice thickness, and a low ability to identify small, highly mobile objects (such as vegetations) due to the need to acquire images over several cardiac cycles. The review examines the advantages and disadvantages of each imaging aspect in detail, and considers how CMR can be used optimally for each valve lesion
A multi-center inter-manufacturer study of the temporal stability of phase-contrast velocity mapping background offset errors
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