137 research outputs found
Role of cardiac energetics in aortic stenosis disease progression: identifying the high-risk metabolic phenotype
Background:Â Severe aortic stenosis (AS) is associated with left ventricular (LV) hypertrophy and cardiac metabolic alterations with evidence of steatosis and impaired myocardial energetics. Despite this common phenotype, there is an unexplained and wide individual heterogeneity in the degree of hypertrophy and progression to myocardial fibrosis and heart failure. We sought to determine whether the cardiac metabolic state may underpin this variability.
Methods:Â We recruited 74 asymptomatic participants with AS and 13 healthy volunteers. Cardiac energetics were measured using phosphorus spectroscopy to define the myocardial phosphocreatine to adenosine triphosphate ratio. Myocardial lipid content was determined using proton spectroscopy. Cardiac function was assessed by cardiovascular magnetic resonance cine imaging.
Results:Â Phosphocreatine/adenosine triphosphate was reduced early and significantly across the LV wall thickness quartiles (Q2, 1.50 [1.21â1.71] versus Q1, 1.64 [1.53â1.94]) with a progressive decline with increasing disease severity (Q4, 1.48 [1.18â1.70];Â P=0.02). Myocardial triglyceride content levels were overall higher in all the quartiles with a significant increase seen across the AV pressure gradient quartiles (Q2, 1.36 [0.86â1.98] versus Q1, 1.03 [0.81â1.56];Â P=0.034). While all AS groups had evidence of subclinical LV dysfunction with impaired strain parameters, impaired systolic longitudinal strain was related to the degree of energetic impairment (r=0.219;Â P=0.03). Phosphocreatine/adenosine triphosphate was not only an independent predictor of LV wall thickness (r=â0.20;Â P=0.04) but also strongly associated with myocardial fibrosis (r=â0.24;Â P=0.03), suggesting that metabolic changes play a role in disease progression. The metabolic and functional parameters showed comparable results when graded by clinical severity of AS.
Conclusions:Â A gradient of myocardial energetic deficit and steatosis exists across the spectrum of hypertrophied AS hearts, and these metabolic changes precede irreversible LV remodeling and subclinical dysfunction. As such, cardiac metabolism may play an important and potentially causal role in disease progression
Recommended from our members
The effects of iodinated CT contrast agent on phosphorus MRS
Synopsis
Contrast-enhanced CT examination can influence H-MRI measurements performed within 24h after the CT scan, due to a reduction in water T and T caused
by the iodinated contrast agents used in CT. We have investigated whether contrast from a previous CT examination would also influence metabolic
measurements made using P-MRS, by measuring the T of H and P signals in human blood. We find that iodinated CT contrast agent has no effect on
phosphorus T s. Therefore, P-MRS examinations will not be influenced by prior CT (unlike H-MRI scans).We acknowledge financial support from the British Heart Foundation (FS/10/002/28078; FS/14/17/30634; RG/11/9/28921), a Sir Henry Dale Fellowship from the Wellcome
Trust and the Royal Society (098436/Z/12/Z), a Novo Nordisk Foundation Postdoctoral Research Fellowship and from the Slovak Grant Agencies VEGA (2/0001/17) and APVV
(15-0029)
Determinants of left ventricular mass in obesity; a cardiovascular magnetic resonance study
<p>Abstract</p> <p>Background</p> <p>Obesity is linked to increased left ventricular mass, an independent predictor of mortality. As a result of this, understanding the determinants of left ventricular mass in the setting of obesity has both therapeutic and prognostic implications. Using cardiovascular magnetic resonance our goal was to elucidate the main predictors of left ventricular mass in severely obese subjects free of additional cardiovascular risk factors.</p> <p>Methods</p> <p>38 obese (BMI 37.8 ± 6.9 kg/m<sup>2</sup>) and 16 normal weight controls subjects, (BMI 21.7 ± 1.8 kg/m<sup>2</sup>), all without cardiovascular risk factors, underwent cardiovascular magnetic resonance imaging to assess left ventricular mass, left ventricular volumes and visceral fat mass. Left ventricular mass was then compared to serum and anthropometric markers of obesity linked to left ventricular mass, i.e. height, age, blood pressure, total fat mass, visceral fat mass, lean mass, serum leptin and fasting insulin level.</p> <p>Results</p> <p>As expected, obesity was associated with significantly increased left ventricular mass (126 ± 27 vs 90 ± 20 g; p < 0.001). Stepwise multiple regression analysis showed that over 75% of the cross sectional variation in left ventricular mass can be explained by lean body mass (ÎČ = 0.51, p < 0.001), LV stroke volume (ÎČ = 0.31 p = 0.001) and abdominal visceral fat mass (ÎČ = 0.20, p = 0.02), all of which showed highly significant independent associations with left ventricular mass (overall R<sup>2 </sup>= 0.77).</p> <p>Conclusion</p> <p>The left ventricular hypertrophic response to obesity in the absence of additional cardiovascular risk factors is mainly attributable to increases in lean body mass, LV stroke volume and visceral fat mass. In view of the well documented link between obesity, left ventricular hypertrophy and mortality, these findings have potentially important prognostic and therapeutic implications for primary and secondary prevention.</p
Waterâsuppression cycling 3âT cardiac 1 HâMRS detects altered creatine and choline in patients with aortic or mitral stenosis
Funder: Gates Cambridge Trust; Id: http://dx.doi.org/10.13039/501100005370Funder: British Heart Foundation Intermediate FellowshipCardiac proton spectroscopy (1HâMRS) is widely used to quantify lipids. Other metabolites (e.g. creatine and choline) are clinically relevant but more challenging to quantify because of their low concentrations (approximately 10 mmol/L) and because of cardiac motion. To quantify cardiac creatine and choline, we added waterâsuppression cycling (WSC) to two singleâvoxel spectroscopy sequences (STEAM and PRESS). WSC introduces controlled residual water signals that alternate between positive and negative phases from transient to transient, enabling robust phase and frequency correction. Moreover, a particular weighted sum of transients eliminates residual water signals without baseline distortion. We compared WSC and the vendor's standard âWETâ water suppression in phantoms. Next, we tested repeatability in 10 volunteers (seven males, three females; age 29.3 ± 4.0 years; body mass index [BMI] 23.7 ± 4.1 kg/m2). Fat fraction, creatine concentration and choline concentration when quantified by STEAMâWET were 0.30% ± 0.11%, 29.6 ± 7.0 ÎŒmol/g and 7.9 ± 6.7 ÎŒmol/g, respectively; and when quantified by PRESSâWSC they were 0.30% ± 0.15%, 31.5 ± 3.1 ÎŒmol/g and 8.3 ± 4.4 ÎŒmol/g, respectively. Compared with STEAMâWET, PRESSâWSC gave spectra whose fitting quality expressed by CramĂ©râRao lower bounds improved by 26% for creatine and 32% for choline. Repeatability of metabolite concentration measurements improved by 72% for creatine and 40% for choline. We also compared STEAMâWET and PRESSâWSC in 13 patients with severe symptomatic aortic or mitral stenosis indicated for valve replacement surgery (10 males, three females; age 75.9 ± 6.3 years; BMI 27.4 ± 4.3 kg/m2). Spectra were of analysable quality in eight patients for STEAMâWET, and in nine for PRESSâWSC. We observed comparable lipid concentrations with those in healthy volunteers, significantly reduced creatine concentrations, and a trend towards decreased choline concentrations. We conclude that PRESSâWSC offers improved performance and reproducibility for the quantification of cardiac lipids, creatine and choline concentrations in healthy volunteers at 3 T. It also offers improved performance compared with STEAMâWET for detecting altered creatine and choline concentrations in patients with valve disease
Waterâsuppression cycling 3âT cardiac 1 HâMRS detects altered creatine and choline in patients with aortic or mitral stenosis
Funder: Gates Cambridge Trust; Id: http://dx.doi.org/10.13039/501100005370Funder: British Heart Foundation Intermediate FellowshipCardiac proton spectroscopy (1HâMRS) is widely used to quantify lipids. Other metabolites (e.g. creatine and choline) are clinically relevant but more challenging to quantify because of their low concentrations (approximately 10 mmol/L) and because of cardiac motion. To quantify cardiac creatine and choline, we added waterâsuppression cycling (WSC) to two singleâvoxel spectroscopy sequences (STEAM and PRESS). WSC introduces controlled residual water signals that alternate between positive and negative phases from transient to transient, enabling robust phase and frequency correction. Moreover, a particular weighted sum of transients eliminates residual water signals without baseline distortion. We compared WSC and the vendor's standard âWETâ water suppression in phantoms. Next, we tested repeatability in 10 volunteers (seven males, three females; age 29.3 ± 4.0 years; body mass index [BMI] 23.7 ± 4.1 kg/m2). Fat fraction, creatine concentration and choline concentration when quantified by STEAMâWET were 0.30% ± 0.11%, 29.6 ± 7.0 ÎŒmol/g and 7.9 ± 6.7 ÎŒmol/g, respectively; and when quantified by PRESSâWSC they were 0.30% ± 0.15%, 31.5 ± 3.1 ÎŒmol/g and 8.3 ± 4.4 ÎŒmol/g, respectively. Compared with STEAMâWET, PRESSâWSC gave spectra whose fitting quality expressed by CramĂ©râRao lower bounds improved by 26% for creatine and 32% for choline. Repeatability of metabolite concentration measurements improved by 72% for creatine and 40% for choline. We also compared STEAMâWET and PRESSâWSC in 13 patients with severe symptomatic aortic or mitral stenosis indicated for valve replacement surgery (10 males, three females; age 75.9 ± 6.3 years; BMI 27.4 ± 4.3 kg/m2). Spectra were of analysable quality in eight patients for STEAMâWET, and in nine for PRESSâWSC. We observed comparable lipid concentrations with those in healthy volunteers, significantly reduced creatine concentrations, and a trend towards decreased choline concentrations. We conclude that PRESSâWSC offers improved performance and reproducibility for the quantification of cardiac lipids, creatine and choline concentrations in healthy volunteers at 3 T. It also offers improved performance compared with STEAMâWET for detecting altered creatine and choline concentrations in patients with valve disease
Observational study of regional aortic size referenced to body size: production of a cardiovascular magnetic resonance nomogram
Background: Cardiovascular magnetic resonance (CMR) is regarded as the gold standard for clinical assessment of the aorta, but normal dimensions are usually referenced to echocardiographic and computed tomography data and no large CMR normal reference range exists. As a result we aimed to 1) produce a normal CMR reference range of aortic diameters and 2) investigate the relationship between regional aortic size and body surface area (BSA) in a large group of healthy subjects with no vascular risk factors.
Methods: 447 subjects (208 male, aged 19â70 years) without identifiable cardiac risk factors (BMI range 15.7â52.6 kg/m2) underwent CMR at 1.5 T to determine aortic diameter at three levels: the ascending aorta (Ao) and proximal descending aorta (PDA) at the level of the pulmonary artery, and the abdominal aorta (DDA), at a level 12 cm distal to the PDA. In addition, 201 of these subjects had aortic root imaging, allowing for measurements at the level of the aortic valve annulus (AV), aortic sinuses and sinotubular junction (STJ).
Results: Normal diameters (mean ±2 SD) were; AV annulus male(â) 24.4â±â5.4, female (â) 21.0â±â3.6 mm, aortic sinusâ32.4â±â7.7, â27.6â±â5.8 mm, ST-junction â25.0â±â7.4, â21.8â±â5.4 mm, Ao â26.7â±â7.7, â25.5â±â7.4 mm, PDA â20.6â±â5.6, +18.9â±â4.0 mm, DDA â17.6â±â5.1, â16.4â±â4.0 mm. Aortic root and thoracic aortic diameters increased at all levels measured with BSA. No gender difference was seen in the degree of dilatation with increasing BSA (pâ>â0.5 for all analyses).
Conclusion: Across both genders, increasing body size is characterized by a modest degree of aortic dilatation, even in the absence of traditional cardiovascular risk factors
- âŠ