4D Flow Versus 2D Phase Contrast MRI in Populations With Bi- and Tricuspid Aortic Valves.

AIM: To compare 4D flow magnetic resonance imaging (MRI) and 2D phase contrast (PC) MRI when evaluating bicuspid (BAV) and tricuspid (TAV) aortic valves. MATERIALS AND METHODS: A total of 83 subjects (35 BAV, 48 TAV) were explored with 4D flow and 2D PC MRI. Systolic peak velocity, peak flow and regurgitation fraction were analysed at two pre-defined aortic levels (aortic root, mid-tubular). Furthermore, the two methods of 4D flow analysis (Heart and Artery) were compared. RESULTS: Correlation between the 2D PC MRI and 4D flow MRI derived parameters ranged from moderate (R=0.58) to high (R=0.90). 4D flow MRI yielded significantly higher peak velocities in the tubular aorta in both groups. Regarding the aortic root, peak velocities were significantly higher in the TAV group with 4D flow MRI, but in the BAV group 4D flow MRI yielded non-significantly lower values. Findings on peak flow differences between the two modalities followed the same pattern as the differences in peak velocities. 4D flow MRI derived regurgitation fraction values were lower in both locations in both groups. Interobserver agreement for different 4D flow MRI acquired parameters varied from poor (ICC=0.07) to excellent (ICC=1.0) in the aortic root, and it was excellent in the tubular aorta (ICC=0.8-1.0). CONCLUSION: 4D flow MRI seems to be accurate in comparison to 2D PC MRI in normal aortic valves and in BAV with mild to moderate stenosis. However, the varying interobserver reproducibility and impaired accuracy at higher flow velocities should be taken into account in clinical practice when using the 4D flow method.

Dilatation of the ascending aorta - Growth rate, risk factors and clinical outcomes in the long-term follow-up.

OBJECTIVES: To explore the risk factors, growth rate and outcomes of ascending aortic (AA) dilatation in patients scheduled for imaging follow-up. METHODS: This retrospective study included 143 patients who were followed-up with thoracic aortic CT-angiography. AA diameters were measured from aortic root (sinus Valsalva) and mid-AA at the baseline and after long-term follow-up. Risk factors and clinical outcomes were collected from medical records. The standard error of measurement (SEM) method was used to assess the statistical significance of the growth rate of AA dilatation. RESULTS: The patients' mean age was 64.0 ± 10.0 years (males n = 115, 80.4%). The mean imaging follow-up time was 3.4 ± 1.6 years and 5.7 ± 1.7 years in the clinical follow-up. According to the SEM method, 37.8% of the patients (n = 54) experienced significant AA growth; 18.9% (n = 27) in the aortic root (0.5 ± 0.7 mm/year), and 24.5% (n = 35) in the mid-AA (0.4 ± 0.5 mm/year). None of the patients experienced aortic rupture or dissection or died due to aortic reasons during the follow-up. Eighteen patients (12.6%) underwent elective surgical AA reconstruction and 10 patients (7.0%) died due to some other reason. Male gender was the only factor to associate with significant accelerated growth (p = 0.047). However, antihypertensive medication did seem to be a protective factor (p = 0.01). CONCLUSIONS: Less than half of the patients followed due to AA dilatation displayed significant AA growth during the long-term follow-up. In addition, the growth rate per year was small. None of the patients experienced any aortic catastrophes indicating that the prognosis of patients participating in regular imaging follow-up is good.

Excess of visceral adipose tissue with or without aortic elongation leads to a steeper heart position.

BACKGROUND: The heart's position determined as the heart-aorta angle (HAA) has been demonstrated to associate with ascending aortic (AA) dilatation. Visceral adipose tissue (VAT) and aortic elongation may shift the heart to the steeper position. PURPOSE: To investigate whether VAT and aortic length influence the HAA. MATERIAL AND METHODS: We examined 346 consecutive patients (58.4% men; mean age = 67.0 ± 14.1 years) who underwent aortic computed tomography angiography (CTA). HAA was measured as the angle between the long axis of the heart and AA midline. The amount of VAT was measured at the level of middle L4 vertebra from a single axial CT slice. Aortic length was measured by combining four anatomical segments in different CTA images. The amount of VAT and aortic length were determined as mild with values in the lowest quartile and as excessive with values in the other three quartiles. RESULTS: A total of 191 patients (55.2%) had no history of aortic diseases, 134 (38.7%) displayed AA dilatation, 8 (2.3%) had abdominal aortic aneurysm (AAA), and 13 (3.8%) had both AA dilatation and AAA. There was a strong nonlinear regression between smaller HAA and VAT/height, and HAA and aortic length/height. Median HAA was 124.2° (interquartile range 119.0°-130.8°) in patients with a mild amount of VAT versus 120.5° (interquartile range 115.4°-124.7°) in patients with excessive VAT (P < 0.001). CONCLUSION: An excessive amount of VAT and aortic elongation led to a steeper heart position. These aspects may possess clinical value when evaluating aortic diseases in obese patients.

Flow displacement and decreased wall shear stress might be associated with the growth rate of an ascending aortic dilatation.

OBJECTIVES: Our goal was to evaluate whether four-dimensional (4D) flow magnetic resonance imaging (MRI) can predict the growth rate of dilatation of the ascending aorta (AA) in patients with a tricuspid, normally functioning aortic valve. METHODS: In this prospective clinical study, aortic 4D flow MRI was performed at the Kuopio University Hospital on 30 patients diagnosed with AA dilatation (maximum diameter >40 mm) between August 2017 and July 2020. The MRI was repeated after a 1-year follow-up, with AA dimensions and 4D flow parameters analysed retrospectively at both time points. The standard error of measurement was used to assess the statistical significance of the growth rate of AA dilatation. Flow displacement (FD) was transformed to a class-scaled parameter using FD ≥5% as a threshold. RESULTS: Statistically significant growth [median 2.1 mm (1.5-2.2 mm); P = 0.03] was detected in 6 male patients (20%); the AA diameter remained unchanged [0.2 mm (-0.3 to 0.9 mm)] in 24 patients (80%). An increased FD at the baseline was associated with significant growth during the 1-year follow-up in the proximal AA. An association was detected between decreased total wall shear stress and significant aortic growth in the inner curve of the sinotubular junction [529 mPa (449-664 mPa) vs 775 mPa (609-944 mPa); P = 0.03] and the anterior side of the proximal aortic arch [356 mPa (305-367 mPa) vs 493 mPa (390-586 mPa); P < 0.001]. CONCLUSIONS: FD and decreased wall shear stress seem to be associated with significant growth of AA dilatation at the 1-year follow-up. Thus, 4D flow MRI might be useful in assessing risk for AA diameter growth in patients with a tricuspid aortic valve.

Mechanically robust superhydrophobic polymer surfaces based on protective micropillars.

Considerable attention is currently being devoted less to the question of whether it is possible to produce superhydrophobic polymer surfaces than to just how robust they can be made. The present study demonstrates a new route for improving the mechanical durability of water-repellent structured surfaces. The key idea is the protection of fragile fine-scale surface topographies against wear by larger scale sacrificial micropillars. A variety of surface patterns was manufactured on polypropylene using a microstructuring technique and injection molding. The surfaces subjected to mechanical pressure and abrasive wear were characterized by water contact and sliding angle measurements as well as by scanning electron microscopy and roughness analysis based on optical profilometry. The superhydrophobic polypropylene surfaces with protective structures were found to maintain their wetting properties in mechanical compression up to 20 MPa and in abrasive wear tests up to 120 kPa. For durable properties, the optimal surface density of the protective pillars was found to be about 15%. The present approach to the production of water-repellent polymer surfaces provides the advantages of mass production and mechanical robustness with practical applications of structurally functionalized surfaces.