Aortic stiffness in aortic stenosis assessed by cardiovascular MRI: a comparison between bicuspid and tricuspid valves

Objectives To compare aortic size and stiffness parameters on MRI between bicuspid aortic valve (BAV) and tricuspid aortic valve (TAV) patients with aortic stenosis (AS). Methods MRI was performed in 174 patients with asymptomatic moderate-severe AS (mean AVAI 0.57 ± 0.14 cm2/m2) and 23 controls on 3T scanners. Valve morphology was available/analysable in 169 patients: 63 BAV (41 type-I, 22 type-II) and 106 TAV. Aortic cross-sectional areas were measured at the level of the pulmonary artery bifurcation. The ascending and descending aorta (AA, DA) distensibility, and pulse wave velocity (PWV) around the aortic arch were calculated. Results The AA and DA areas were lower in the controls, with no difference in DA distensibility or PWV, but slightly lower AA distensibility than in the patient group. With increasing age, there was a decrease in distensibility and an increase in PWV. After correcting for age, the AA maximum cross-sectional area was higher in bicuspid vs. tricuspid patients (12.97 [11.10, 15.59] vs. 10.06 [8.57, 12.04] cm2, p < 0.001), but there were no significant differences in AA distensibility (p = 0.099), DA distensibility (p = 0.498) or PWV (p = 0.235). Patients with BAV type-II valves demonstrated a significantly higher AA distensibility and lower PWV compared to type-I, despite a trend towards higher AA area. Conclusions In patients with significant AS, BAV patients do not have increased aortic stiffness compared to those with TAV despite increased ascending aortic dimensions. Those with type-II BAV have less aortic stiffness despite greater dimensions. These results demonstrate a dissociation between aortic dilatation and stiffness and suggest that altered flow patterns may play a role. Key Points • Both cellular abnormalities secondary to genetic differences and abnormal flow patterns have been implicated in the pathophysiology of aortic dilatation and increased vascular complications associated with bicuspid aortic valves (BAV). • We demonstrate an increased ascending aortic size in patients with BAV and moderate to severe AS compared to TAV and controls, but no difference in aortic stiffness parameters, therefore suggesting a dissociation between dilatation and stiffness. • Sub-group analysis showed greater aortic size but lower stiffness parameters in those with BAV type-II AS compared to BAV type-I

Anomalous yield reduction in direct-drive DT implosions due to 3He addition

Glass capsules were imploded in direct drive on the OMEGA laser [T. R. Boehly et aI., Opt. Commun. 133, 495, 1997] to look for anomalous degradation in deuterium/tritium (DT) yield (i.e., beyond what is predicted) and changes in reaction history with {sup 3}He addition. Such anomalies have previously been reported for D/{sup 3}He plasmas, but had not yet been investigated for DT/{sup 3}He. Anomalies such as these provide fertile ground for furthering our physics understanding of ICF implosions and capsule performance. A relatively short laser pulse (600 ps) was used to provide some degree of temporal separation between shock and compression yield components for analysis. Anomalous degradation in the compression component of yield was observed, consistent with the 'factor of two' degradation previously reported by MIT at a 50% {sup 3}He atom fraction in D{sub 2} using plastic capsules [Rygg et aI., Phys. Plasmas 13, 052702 (2006)]. However, clean calculations (i.e., no fuel-shell mixing) predict the shock component of yield quite well, contrary to the result reported by MIT, but consistent with LANL results in D{sub 2}/{sup 3}He [Wilson, et aI., lml Phys: Conf Series 112, 022015 (2008)]. X-ray imaging suggests less-than-predicted compression ofcapsules containing {sup 3}He. Leading candidate explanations are poorly understood Equation-of-State (EOS) for gas mixtures, and unanticipated particle pressure variation with increasing {sup 3}He addition