Cardiac exercise imaging using a 3-tesla magnetic resonance-conditional pedal ergometer: Preliminary results in healthy volunteers and patients with known or suspected coronary artery disease

Background: Cardiac magnetic resonance imaging (CMR) remains underutilized as an exercise imaging modality, mostly because of the limited availability of MR-compatible exercise equipment. This study prospectively evaluates the clinical feasibility of a newly developed MR-conditional pedal ergometer for exercise CMR Methods: Ten healthy volunteers (mean age 44 ± 16 years) and 11 patients (mean age 60 ± 9 years) with known or suspected coronary artery disease (CAD) underwent rest and post-exercise cinematic 3T CMR. Visual analysis of wall motion abnormalities (WMA) was rated by 2 experienced radiologists, and volumes and ejection fractions (EF) were determined. Image quality was assessed by a 4-point Likert scale for visibility of endocardial borders.  Results: Median subjective image quality of real-time Cine at rest was 1 (IQR 1–2) and 2 (IQR 2–2.5) for post-exercise real-time Cine (p = 0.001). Exercise induced a significant increase in heart rate (62 [62–73] to 111 [104–143] bpm, p < 0.0001). Stroke volume and cardiac index increased from resting to post-exercise conditions (85 ± 21 to 101 ± 19 mL and 2.9 ± 0.7 to 6.6 ± 1.9 L/min/m2, respectively; both p < 0.0001), driven by a reduction in end-systolic volume (55 ± 20 to 42 ± 21 mL, p < 0.0001). Patients (2/11) with inducible regional WMA at high-resolution post-exercise cine imaging revealed significant coronary artery stenosis in subsequently performed invasive coronary angiography.  Conclusion: Exercise-CMR using our newly developed 3T MR-conditional pedal ergometer is clinically feasible. Imaging of both cardiac response and myocardial ischemia, triggered by dynamic stress, is rapidly conducted while the patient is near their peak heart rate

White Matter Changes in Patients with Friedreich Ataxia after Treatment with Erythropoietin

Background and Purpose—Erythropoietin (EPO) has received growing attention because of its neuro-regenerative properties. Preclinical and clinical evidence supports its therapeutic potential in brain conditions like stroke, multiple sclerosis and schizophrenia. Also in Friedreich ataxia, clinical improvement after EPO therapy was shown. The aim of the present study was to assess possible therapy-associated brain white-matter changes in these patients.Methods—Nine patients with Friedreich ataxia underwent Diffusion Tensor Imaging (DTI) before and after EPO treatment. Tract-based spatial statistics (TBSS) was used for longitudinal comparison. Results—We detected widespread longitudinal increase in fractional anisotropy (FA) and axial diffusivity (D||) in cerebral hemispheres bilaterally (p<0.05, corrected), while no changes were observed within the cerebellum, medulla oblongata and pons. Conclusions—To the best of our knowledge, this is the first DTI study to investigate the effects of erythropoietin in a neurodegenerative disease. Anatomically, the diffusivity changes appear disease-unspecific, and their biological underpinnings deserve further study

Cardiac high-energy phosphate metabolism alters with age as studied in 196 healthy males with the help of 31-phosphorus 2-dimensional chemical shift imaging.

Recently published studies have elucidated alterations of mitochondrial oxidative metabolism during ageing. The intention of the present study was to evaluate the impact of ageing on cardiac high-energy phosphate metabolism and cardiac function in healthy humans. 31-phosphorus 2-dimensional chemical shift imaging (31P 2D CSI) and echocardiography were performed in 196 healthy male volunteers divided into groups of 20 to 40 years (I, n = 43), 40 to 60 years (II, n = 123) and >60 years (III, n = 27) of age. Left ventricular PCr/β-ATP ratio, myocardial mass (MM), ejection fraction and E/A ratio were assessed. Mean PCr/β-ATP ratios were significantly different among the three groups of volunteers (I, 2.10 ± 0.37; II, 1.77 ± 0.37; III, 1.45 ± 0.28; all p<0.001). PCr/β-ATP ratios were inversely related to age (r(2)  =  -0.25; p<0.001) with a decrease from 2.65 by 0.02 per year of ageing. PCr/β-ATP ratios further correlated with MM (r =  -0.371; p<0.001) and E/A ratios (r = 0.213; p<0.02). Moreover, E/A ratios (r =  -0.502, p<0.001), MM (r = 0.304, p<0.001), glucose-levels (r = 0.157, p<0.05) and systolic blood pressure (r = 0.224, p<0.005) showed significant correlations with age. The ejection fraction did not significantly differ between the groups. This study shows that cardiac PCr/β-ATP ratios decrease moderately with age indicating an impairment of mitochondrial oxidative metabolism due to age. Furthermore, MM increases, and E/A ratio decreases with age. Both correlate with left-ventricular PCr/β-ATP ratios. The findings of the present study confirm numerous experimental studies showing an impairment of cardiac mitochondrial function with age

Comparison of an oscillometric method with cardiac magnetic resonance for the analysis of aortic pulse wave velocity.

OBJECTIVES:Pulse wave velocity (PWV) is the proposed gold-standard for the assessment of aortic elastic properties. The aim of this study was to compare aortic PWV determined by a recently developed oscillometric device with cardiac magnetic resonance imaging (CMR). METHODS:PWV was assessed in 40 volunteers with two different methods. The oscillometric method (PWVOSC) is based on a transfer function from the brachial pressure waves determined by oscillometric blood pressure measurements with a common cuff (Mobil-O-Graph, I.E.M. Stolberg, Germany). CMR was used to determine aortic PWVCMR with the use of the transit time method based on phase-contrast imaging at the level of the ascending and abdominal aorta on a clinical 1.5 Tesla scanner (Siemens, Erlangen, Germany). RESULTS:The median age of the study population was 34 years (IQR: 24-55 years, 11 females). A very strong correlation was found between PWVOSC and PWVCMR (r = 0.859, p < 0.001). Mean PWVOSC was 6.7 ± 1.8 m/s and mean PWVCMR was 6.1 ± 1.8 m/s (p < 0.001). Analysis of agreement between the two measurements using Bland-Altman method showed a bias of 0.57 m/s (upper and lower limit of agreement: 2.49 m/s and -1.34 m/s). The corresponding coefficient of variation between both measurements was 15%. CONCLUSION:Aortic pulse wave velocity assessed by transformation of the brachial pressure waveform showed an acceptable agreement with the CMR-derived transit time method

Linear correlation between PWV, clinical characteristics, oscillometric measures and CMR-derived parameters.

<p>PWV_OSC: pulse wave velocity assessed by transformation of oscillometrically defined brachial pressure wave form, PWV_CMR: pulse wave velocity assessed by cardiac magnetic resonance, RR_sys: systolic blood pressure, RR_dia: diastolic blood pressure, DC_aA: distensibility coefficient of the ascending aorta, DC_dA: distensibility coefficient of the descending thoracic aorta, DC_abA: distensibility coefficient of the abdominal aorta, DC mean: mean DC of all three aortic levels, DC central: DC at different aortic levels calculated using central aortic pulse pressure.</p><p>Linear correlation between PWV, clinical characteristics, oscillometric measures and CMR-derived parameters.</p

Study population characteristics.

<p>RR_sys: systolic blood pressure, RR_dia: diastolic blood pressure.</p><p>Study population characteristics.</p

Assessment of aortic pulse wave velocity.

<p>Evaluation of aortic pulse wave velocity using (a1) a transfer function from (a2) brachial pressure wave analysis and (b) the cardiac magnetic resonance-derived transit time method based on phase-contrast imaging. R1 and R2 indicate the aortic region.</p

The montage of localizers and spectra are derived from a 62 year old, healthy man.

<p>The axial, coronal and sagittal images were acquired for localization purposes. The grid reflects the position of the MR spectroscopic slab, originally measured with 8×8 phase encoding steps, which were interpolated to a matrix of 16×16 in the k-space. The large, semi-transparent rectangles on the localizer images show the positions of spectra, which were averaged for the determination of left-ventricular PCr/β-ATP ratio (A–H). The small rectangle on the axial localizer image represents the position of a voxel from the thorax muscles, which is given for comparison. On each spectrum, pictograms of the localizer images are superimposed on the right margin.</p

Correlation of aortic pulse wave velocity assessed by the two methods.

<p>Linear correlation between aortic pulse wave velocities assessed by brachial oscillometry (PWV_OSC) and cardiac magnetic resonance (PWV_CMR).</p