Abstract
Introduction
In patients with severe aortic stenosis (AS), the presence of left ventricular systolic dysfunction is one of the main predictors of adverse events after valve replacement ...surgery (SAVR). However, more and more patients are being referred for surgery early on and have preserved systolic function at the time of surgery. Within this category, global longitudinal strain (GLS) has been proposed as a marker of ventricular remodeling after cardiac surgery.
Objectives
Our study aims to identify the variation of GLS in patients undergoing SAVR and any differences compared to classes of diastolic dysfunction.
Materials and methods
From June 2020 to October 2022, we analyzed 100 patients with AS with an indication for cardiac surgery treatment admitted to the cardiac surgery department of our AOU. All patients underwent an echocardiogram immediately before surgery and in the early postoperative period (mean 7 days); 52 of them were enrolled for follow-up and repeated an echocardiogram at least 3 months after surgery. In all cases, the GLS of the left ventricle was calculated and patients were divided into four classes by the degree of diastolic dysfunction (0-III) according to the most recent international guidelines; moreover, patients were divided into 2 groups: group A for grades 0-1 of diastolic dysfunction and Group B for grades 2-3. The data were analyzed with SPSS 28 software. Analysis of variance was performed with a t-test and ANOVA test.
Results
In the final analysis, 100 patients with AS were included, with a mean age of 70.8±8.27, of whom 43 were women (43%) and 57 were men (57%). In 20 patients (20%) ischaemic heart disease with an indication for coronary revascularization was also present. The mean preoperative ejection fraction was 58.98±9.5%. The mean GLS values before surgery were 15.13±4.56% with a reduction immediately post-cardiac surgery of 12.26±3.67%, p<0.0001. GLS values were comparable within the various classes of diastolic dysfunction at preoperative examination (p=0.579) and immediately postoperative (p=0.286).
At follow-up, analysis was repeated for 52 patients: an improvement in mean GLS was found: 16.09±3.64%, p<0.0001. The mean GLS in the two groups at follow-up was statistically different: 17.38±3.35% in group A vs 13.44±3.63% in group B, p<0.0001.
Conclusions
In our case series, patients with severe aortic stenosis undergoing SAVR show a significant early reduction in GLS regardless of the degree of diastolic dysfunction, while after at least 3 months of follow-up, they show a great recovery, significantly better in patients with Grades 0 or 1 diastolic dysfunction.GLS at the 3 times
. Microbeam radiation therapy (MRT) is an alternative emerging radiotherapy treatment modality which has demonstrated effective radioresistant tumour control while sparing surrounding healthy tissue ...in preclinical trials. This apparent selectivity is achieved through MRT combining ultra-high dose rates with micron-scale spatial fractionation of the delivered x-ray treatment field. Quality assurance dosimetry for MRT must therefore overcome a significant challenge, as detectors require both a high dynamic range and a high spatial resolution to perform accurately.
. In this work, a series of radiation hard a-Si:H diodes, with different thicknesses and carrier selective contact configurations, have been characterised for x-ray dosimetry and real-time beam monitoring applications in extremely high flux beamlines utilised for MRT at the Australian Synchrotron.
. These devices displayed superior radiation hardness under constant high dose-rate irradiations on the order of 6000 Gy s
, with a variation in response of 10% over a delivered dose range of approximately 600 kGy. Dose linearity of each detector to x-rays with a peak energy of 117 keV is reported, with sensitivities ranging from (2.74 ± 0.02) nC/Gy to (4.96 ± 0.02) nC/Gy. For detectors with 0.8
m thick active a-Si:H layer, their operation in an edge-on orientation allows for the reconstruction of micron-size beam profiles (microbeams). The microbeams, with a nominal full-width-half-max of 50
m and a peak-to-peak separation of 400
m, were reconstructed with extreme accuracy. The full-width-half-max was observed as 55 ± 1
m. Evaluation of the peak-to-valley dose ratio and dose-rate dependence of the devices, as well as an x-ray induced charge (XBIC) map of a single pixel is also reported.
. These devices based on novel a-Si:H technology possess a unique combination of accurate dosimetric performance and radiation resistance, making them an ideal candidate for x-ray dosimetry in high dose-rate environments such as FLASH and MRT.
