Comparison of different sowtware solutions for AVC quantification using contrast enhanced MDCT

Funding Acknowledgements

Type of funding sources: None.

Aims

Estimating aortic valve calcification (AVC) derived from multi detector computed tomography (MDCT) scans in aortic stenosis (AS) patients has gained increasing interest for diagnostic and prognostic reasons. Little is known about the interchangeability of AVC obtained from different software solutions which, was systematically determined in consecutive patients undergoing contrast enhanced MDCT before TAVR.

Methods and results

50 randomly selected patients who underwent contrast enhanced MDCT for TAVR planning were included in the analysis. All MDCT data sets were analysed using three different software vendors (3 Mensio, CVI 42, Snygo.Via). AVC score was expressed as mm³. For analysing intra- and inter-observer variability a subset of 10 patients were analysed twice with at least 2 weeks in between the measurements. Intra- and inter-observer variability was quantified using the ICC reliability method, Bland-Altman analysis and coefficients of variation.

AVC scores were successfully obtained using all software solutions (3 Mensio 941 ± 623, CVI42 941 ± 637, Syngo.Via 948 mm³ ± 655) without significant differences (p = 0.455). There was excellent intra- (3 Mensio: ICC 0.999 [0.995 – 1.000], COV 3.86 %, mean difference -19.28 [± 45.07]; CVI 42: ICC 1.000 [0.999 – 1.000], COV 1.6 %, mean difference -10.28 [± 18.6]; Syngo.Via: ICC 0.998 [0.993 – 1.000], COV 4.13 %, mean difference -24.81 [± 48.52]) and inter-observer variability (3 Mensio: ICC 1.000 [0.999 – 1.000], COV 1.38 %, mean difference -7.14 [± 16.20]; CVI 42: ICC 1.000 [1.000 – 1.000], COV 1.01 %, mean difference -1.74 [± 11.83]; Syngo.Via: ICC 0.996 [0.985 – 0.999], COV 6.68 %, mean difference -0.65 [± 79.43]) for all software types. Best inter-vendor agreement was found between CVI 42 and Syngo.Via (ICC 0.997 [CI 0.995-0.998], COV 7.26 %, mean difference -7 [± 68.60]) followed by 3 Mensio / CVI 42 (ICC 0,996 [CI 0,922-0,998], COV 8.95 %, mean difference -0.06 [± 84.16]) and 3 Mensio / Syngo.Via (ICC 0,992 [CI 0,986-0,995], COV 12.19%, mean difference -7.06 [± 115.07]).

Conclusion

Contrast enhanced MDCT derived AVC scores are interchangeable between and reproducible within different commercially available software solutions. This is important since sufficient reproducibility, inter-changeability and valid results represent prerequisites for accurate TAVR planning and wide spread clinical use.

Aortic valve calcification and endomyocardial fibrosis determine adverse outcomes following transcatheter aortic valve replacement

Funding Acknowledgements

Type of funding sources: None.

Aims

There is evidence to suggest that subtype of aortic stenosis (AS), degree of myocardial fibrosis (MF) and level of aortic valve calcification (AVC) are associated with adverse cardiac outcome in AS. Since little is known about their respective contribution, we sought to investigate their relative importance and interplay as well as association with adverse cardiac events.

Methods

100 consecutive patients with severe AS and indication for transfemoral transcatheter aortic valve replacement (TAVR) were prospectively enrolled between January 2017 and October 2018. Patients underwent transthoracic echocardiography, multi detector computed tomography (MDCT) and left ventricular endomyocardial biopsy at the time of TAVR.

Results

The final study cohort consisted of 92 patients with completed study protocol comprising of 39 (42.4 %) normal ejection fraction high gradient (NEFHG), 13 (14.1 %) low EF high gradient (LEFHG), 25 (27.2 %) low EF (flow) low gradient (LEFLG) and 15 (16.3 %) paradoxical low flow low gradient (PLFLG) AS. The high gradient phenotypes (NEFHG and LEFHG) showed the largest amount of AVC (807 ± 421; 813 ± 281 mm³ respectively) as compared to the low gradient phenotypes (LEFLG and PLFLG; 503 ± 326; 555 ± 594 mm³ respectively, p < 0.05). Conversely, MF was most prevalent in low output phenotypes (LEFLG > LEFHG > PLFLG > HEFHG, p < 0.05). This was paralleled by larger cardiovascular mortality within 600 days post TAVR (LEFLG n = 7 > PLFLG n = 4 > LEFHG n = 2 > NEFHG n = 1). In Patients with high MF burden a higher AVC was associated with a lower mortality (p = 0.045, HR = 0.261, 95%CI 0.07-0.97). Within LEFLG AS, patients with larger AVC (>476.8 mm³) had larger MF (40.2%) and higher cardiovascular mortality (n = 5) as compared to patients with lower AVC (£476.8 mm³, 17.1% MF, p = 0.027, cardiovascular mortality n = 2).

Conclusion

MF is associated with adverse cardiovascular outcome following TAVR which is most prevalent in low ejection fraction situations. In the presence of large MF burden patients with large AVC have better outcome following TAVR. Conversely worse outcome in large MF and relatively little AVC may be explained by a relative prominence of an underlying cardiomyopathy while better survival rates in large AVC patients may indicate severe AS associated pressure overload relief and subsequently improved survival following TAVR.

Real-time cardiac magnetic resonance tissue characterisation for fibrosis assessment in aortic stenosis

Background

Myocardial fibrosis is a major determinant of outcome in aortic stenosis (AS). Novel fast real-time (RT) cardiac magnetic resonance (CMR) mapping techniques allow comprehensive quantification of fibrosis but have not yet been adequately validated against standard techniques and histology.

Methods

Patients with severe AS underwent CMR before (n=110) and left ventricular (LV) endomyocardial biopsy (n=46) at transcatheter aortic valve replacement (TAVR). Midventricular short axis native, post-contrast T1 and extracellular volume fraction (ECV) maps were generated using commercially available 5(3)3 MOLLI and RT single-shot inversion recovery fast low-angle shot (FLASH) with radial undersampling. ECV and LV mass were used to calculate LV matrix volumes. Variability and agreements were assessed between RT, MOLLI and histology using intraclass correlation coefficients, coefficients of variation and Bland Altman analyses.

Results

RT and MOLLI derived ECV were similar for myocardium (26.2 vs. 26.5, p=0.073) and inter-ventricular septum (26.2 vs. 26.5, p=0.216). MOLLI native T1 time was in median 20 ms longer compared to RT (p<0.001). Agreement between RT and MOLLI was best for ECV (ICC >0.91), excellent for post-contrast T1 times (ICC >0.81) and good for native T1 times (ICC >0.62). Diffuse collagen volume fraction by biopsies was in median 7.8%. ECV (RT r=0.345, p=0.039; MOLLI r=0.40, p=0.010) and LV matrix volumes (RT r=0.45, p=0.005; MOLLI r=0.43, p=0.007) were the only parameters associated with histology.

Conclusions

RT mapping offers precise T1 and ECV assessments with similar agreement with histology as compared to conventional MOLLI techniques. Single-shot real time techniques may be advantageous in sicker patients prone to dyspnoea or arrhythmia.

Funding Acknowledgement

Type of funding source: Foundation. Main funding source(s): German Research Foundation

Structural and functional reverse myocardial remodeling following transcatheter aortic valve replacement

Background

Myocardial reverse remodeling determines outcome in patients with severe aortic stenosis (AS) following transcatheter aortic valve replacement (TAVR). However, little is known about the interplay of myocardial function and structure after TAVR. Since cardiac magnetic resonance (CMR) imaging allows comprehensive quantification of both structure and function we aimed to assess changes in myocardial tissue composition and deformation before and following TAVR.

Methods

CMR imaging was performed in 40 prospectively enrolled patients with severe AS before and one year after TAVR. Myocardial function was characterized using volumetry and CMR-feature-tracking (FT) deformation imaging of left ventricular (LV) global longitudinal strain (GLS) and atrial function (atrial reservoir ES, conduit Ee and booster pump strain EA). Myocardial structure was assessed using T1 mapping and late gadolinium enhancement (LGE) analysis. LV cellular and matrix volumes were calculated based on extra cellular volume fraction (ECV) and LV mass. CMR-FT results were compared to a control group of twenty patients with normal biventricular function. Moreover, biomarkers (NT-proBNP), functional (six-minute-walking-test) and clinical status (NYHA, Minnesota LIVING WITH HEART FAILURE score) were determined at baseline and one-year follow-up.

Results

Regression of both cellular (−20.6%, p<0.001) and matrix volumes (−12.3%, p=0.003) and subsequently increased ECV (+9.0%, p=0.001) were documented one year after TAVR. Ventricular and atrial strains were impaired at baseline (GLS p=0.004, Es p<0.001, Ee p<0.001) and recovered during follow-up (GLS p<0.001, Es p=0.005, Ee p=0.001). These changes were paralleled by improvements in NYHA (p<0.001) and Minnesota (p<0.001) scores as well as decline in NT-proBNP levels (p=0.001). There was a significant association of LV fibrosis as defined by matrix volume and extent of LGE and ventricular and atrial functional impairment (correlation of matrix volume and: GLS r=0.57, p<0.001, Es r=−0.44, p=0.009; correlation of LGE%LV and: GLS r=0.41, p=0.015, Es: r=−0.4, p=0.02, and Ea: r=−0.41, p=0.02).

Conclusion

Regression of fibrosis and cellular hypertrophy determine improved myocardial function and recovery from heart failure following TAVR. Prognostic implications of the observed changes will need to be explored next to identify makers and therapeutic targets for optimized management of these patients.

Funding Acknowledgement

Type of funding source: Foundation. Main funding source(s): German Research Foundation (DFG, CRC 1002, D1)

Performance of different myocardial tissue tracking algorithms and acquisition-based strain imaging to characterise myocardial pathology

Background

Myocardial deformation imaging is superior in risk-stratification compared to volumetric approaches. Myocardial Feature-Tracking (FT) allows easy post-processing of routinely acquired cine images. Since there is no clear recommendation regarding FT post-processing we sought to compare different FT-strains with reference standard techniques including tagging and strain encoded (SENC) magnetic resonance imaging.

Methods

CMR-FT software from 4 different vendors (TomTec, Medis, Circle, Neosoft), CMR tagging (Segment) and fastSENC (MyoStrain) were used to determine left ventricular (LV) global longitudinal and circumferential strains (GLS and GCS) in 12 healthy volunteers and 12 heart failure patients. Variability and agreements were assessed using intraclass correlation coefficients, coefficients of variation and Bland Altman plots.

Results

Compared to tagging, FT-based strain was software independently significantly higher except for GCS using Medis (p=0.178). Compared to fSENC, mean-differences of GLS were smaller within a range of ±1.5%. For GCS this only applied to CVI and Medis (<1.5%) but not TomTec (>7%) or Neosoft (>4%). Absolute agreements comparing FT to tagging were best for CVI (GLS ICC0.70) and Medis (GCS ICC0.85). Compared to fSENC agreement of GLS was generally excellent (ICC>0.77), but only CVI and Medis revealed excellent agreement for GCS (ICC0.88 and 0.85). Consistency and correlation of GLS were software independently high compared with tagging and fSENC (ICC>0.86, r>0.76) while being lower for GCS (ICC>0.68, r>0.72).

Conclusion

Although agreement differs between deformation assessment approaches, consistency and correlation are high irrespective of the method chosen, thus indicating reliable strain assessment. Further standardisation and introduction of uniform references is warranted for clinical routine implementation.

Funding Acknowledgement

Type of funding source: Public grant(s) – National budget only. Main funding source(s): DZHK - German Centre for Cardiovascular Research

Frequency and prognostic impact of right ventricular involvement in acute myocardial infarction

Background

Right ventricular (RV) involvement complicating myocardial infarction (MI) is thought to impact prognosis, but potent RV markers for risk stratification are lacking.

Purpose

To assess the frequency and prognostic implications of concomitant structural and functional RV injury in MI.

Methods

Cardiac magnetic resonance (CMR) was performed in 1235 patients with MI (STEMI: n=795; NSTEMI: n=440) 3 days after reperfusion by primary percutaneous coronary intervention. Central core laboratory-masked analyses included structural (edema representing reversible ischemia, irreversible infarction, microvascular obstruction [MVO]) and functional (ejection fraction, global longitudinal strain [GLS]) RV alterations. The clinical endpoint was the 12-month rate of major adverse cardiac events (MACE).

Results

RV ischemia and infarction were observed in 19.6% and 12.1% of patients, respectively, suggesting complete myocardial salvage in one-third of patients. RV ischemia was associated with a significantly increased risk of MACE (10.1% versus 6.2%; p=0.035), while patients with RV infarction showed only numerically increased event rates (p=0.075). RV MVO was observed in 2.4% and not linked to outcome (p=0.894). Stratification according to median RV GLS (10.2% versus 3.8%; p<0.001) but not RV ejection fraction (p=0.175) resulted in elevated MACE rates. Multivariable analysis including clinical and left ventricular MI characteristics identified RV GLS as an independent predictor of outcome (hazard ratio 1.05, 95% confidence interval 1.00–1.09; p=0.034) in addition to age (p=0.001), Killip class (p=0.020), and left ventricular GLS (p=0.001), while RV ischemia was not independently associated with outcome.

Conclusions

RV GLS is a predictor of post-infarction adverse events over and above established risk factors, while structural RV involvement was not independently associated with outcome.

Funding Acknowledgement

Type of funding source: None

Continuous delivery of rhBMP2 and rhVEGF165 at a certain ratio enhances bone formation in mandibular defects over the delivery of rhBMP2 alone--An experimental study in rats

The aim of the present study was to test the hypothesis that different amounts of vascular endothelial growth factor and bone morphogenic protein differentially affect bone formation when applied for repair of non-healing defects in the rat mandible. Porous composite PDLLA/CaCO3 carriers were fabricated as slow release carriers and loaded with rhBMP2 and rhVEGF165 in 10 different dosage combinations using gas foaming with supercritical carbon dioxide. They were implanted in non-healing defects of the mandibles of 132 adult Wistar rats with additional lateral augmentation. Bone formation was assessed both radiographically (bone volume) and by histomorphometry (bone density). The use of carriers with a ratio of delivery of VEGF/BMP between 0.7 and 1.2 was significantly related to the occurrence of significant increases in radiographic bone volume and/or histologic bone density compared to the use of carriers with a ratio of delivery of ≤ 0.5 when all intervals and all outcome parameters were considered. Moreover, simultaneous delivery at this ratio helped to "save" rhBMP2 as both bone volume and bone density after 13 weeks were reached/surpassed using half the dosage required for rhBMP2 alone. It is concluded, that the combined delivery of rhVEGF165 and rhBMP2 for repair of critical size mandibular defects can significantly enhance volume and density of bone formation over delivery of rhBMP2 alone. It appears from the present results that continuous simultaneous delivery of rhVEGF165 and rhBMP2 at a ratio of approximately 1 is favourable for the enhancement of bone formation.

Solvent free production of porous PDLLA/calcium carbonate composite scaffolds improves the release of bone growth factors

PURPOSE

Incorporation of alkaline nano-/microparticles for neutralization of acidic degradation products into degradable polymer foams requires the use of organic solvents, which may compromise biocompatibility and may be associated with biological hazards. The aim of the present study was to develop and validate a solvent-free method to produce porous poly (DL-lactic acid)/calcium carbonate composite scaffolds (PDLLA/CaCO3) for controlled release of incorporated osteogenic growth factors.

METHODS

Composite PDLLA/CaCO3 granules were produced using a milling process and compared to composite material fabricated through a solution precipitation process using organic solvents. Particle size and mineral content were comparable in both groups. Supercritical carbon dioxide pressure was used to incorporate rhBMP2 into both composites.

RESULTS

Gas foaming resulted in comparable pore structures in both groups exhibiting a homogenous distribution of CaCO3 microparticles in the polymer scaffolds. The elasticity modulus of both types of scaffolds was not significantly different whereas the bending strength of the solvent-free produced scaffolds was significantly lower. The pH values remained constant between 6.90 and 7.25 during degradation of both composites. Release of BMP2 was significantly higher and the induction of alkaline phosphatase was more reliable in the group of scaffolds produced without organic solvents.

CONCLUSION

Solvent-free fabrication of composite PDLLA/CaCO3 scaffolds for controlled release of bone growth factors through gas foaming significantly enhances the release of growth factors and improves the biological efficacy of the incorporated growth factors.

The pulse tube and the pendulum

An inverted pulse tube in which gravity-driven convection is suppressed by acoustic oscillations is analogous to an inverted pendulum that is stabilized by high-frequency vibration of its pivot point. Gravity acts on the gas density gradient arising from the end-to-end temperature gradient in the pulse tube, exerting a force proportional to that density gradient, tending to cause convection when the pulse tube is inverted. Meanwhile, a nonlinear effect exerts an opposing force proportional to the square of any part of the density gradient that is not parallel to the oscillation direction. Experiments show that convection is suppressed when the pulse-tube convection number N(ptc)=omega(2)a(2)DeltaT/T(avg)/[g(alphaD sin theta-L cos theta)] is greater than 1 in slender tubes, where omega is the radian frequency of the oscillations, a is their amplitude, DeltaT is the end-to-end temperature difference, T(avg) is the average absolute temperature, g is the acceleration of gravity, L is the length of the pulse tube and D is its diameter, alpha is about 1.5, and the tip angle theta ranges from 90 degrees for a horizontal tube to 180 degrees for an inverted tube. Theory suggests that the temperature dependence should be DeltaT/T(avg) instead of DeltaT/T(avg).

An acoustic streaming instability in thermoacoustic devices utilizing jet pumps

Thermoacoustic-Stirling hybrid engines and feedback pulse tube refrigerators can utilize jet pumps to suppress streaming that would otherwise cause large heat leaks and reduced efficiency. It is desirable to use jet pumps to suppress streaming because they do not introduce moving parts such as bellows or membranes. In most cases, this form of streaming suppression works reliably. However, in some cases, the streaming suppression has been found to be unstable. Using a simple model of the acoustics in the regenerators and jet pumps of these devices, a stability criterion is derived that predicts when jet pumps can reliably suppress streaming.

A thermoacoustic-Stirling heat engine: detailed study

A new type of thermoacoustic engine based on traveling waves and ideally reversible heat transfer is described. Measurements and analysis of its performance are presented. This new engine outperforms previous thermoacoustic engines, which are based on standing waves and intrinsically irreversible heat transfer, by more than 50%. At its most efficient operating point, it delivers 710 W of acoustic power to its resonator with a thermal efficiency of 0.30, corresponding to 41% of the Carnot efficiency. At its most powerful operating point, it delivers 890 W to its resonator with a thermal efficiency of 0.22. The efficiency of this engine can be degraded by two types of acoustic streaming. These are suppressed by appropriate tapering of crucial surfaces in the engine and by using additional nonlinearity to induce an opposing time-averaged pressure difference. Data are presented which show the nearly complete elimination of the streaming convective heat loads. Analysis of these and other irreversibilities show which components of the engine require further research to achieve higher efficiency. Additionally, these data show that the dynamics and acoustic power flows are well understood, but the details of the streaming suppression and associated heat convection are only qualitatively understood.

Occurrence and expression of glutathione-S-transferase-encoding bphK genes in Burkholderia sp. strain LB400 and other biphenyl-utilizing bacteria

The gene bphK of Burkholderia sp. strain LB400 has previously been shown to be located within the bph locus, which specifies the degradation of biphenyl (BP) and chlorobiphenyls, and to encode a glutathione S-transferase (GST) which accepts 1-chloro-2,4-dinitrobenzene (CDNB) as substrate. The specific physiological role of this gene is not known. It is now shown that the gene is expressed in the parental organism and that GST activity is induced more than 20-fold by growth of the strain on BP relative to succinate when these compounds serve as sole carbon source. Approximately the same induction factor was observed for 2,3-dihydroxybiphenyl 1,2-dioxygenase activity, which is encoded by the 5'-adjacent bphC gene. This suggests that the expression of bphK is coregulated with the expression of genes responsible for the catabolism of BP. A bphK probe detected only a single copy of the gene in strain LB400. A spontaneous BP- mutant of the organism neither gave a signal with the bphK probe nor showed CDNB-accepting GST activity, suggesting that this activity is solely encoded by bphK. Complementation of the mutant with a bph gene cluster devoid of bphK restored the ability to grow on BP, indicating that bphK is not essential for utilization of this carbon source. BphK activity proved to be almost unaffected by up to 100-fold differences in proton concentration or ionic strength. The enzyme showed a narrow range with respect to a variety of widely used electrophilic GST substrates, accepting only CDNB. A number of established laboratory strains as well as novel isolates able to grow on BP as sole carbon and energy source were examined for BphK activity and the presence of a bphK analogue. CDNB assays, probe hybridizations and PCR showed that several, but not all, BP degraders possess this type of GST activity and/or a closely related gene. In all bacteria showing BphK activity, this was induced by growth on BP as sole carbon source, although activity levels differed by up to 10-fold after growth on BP and by up to 60-fold after growth on succinate. This resulted in a variation of induction factors between 2 and 30. In the majority of bphK+ bacteria examined, the gene appeared to be part of LB400-like bph gene clusters. DNA sequencing revealed almost complete identity of bphK genes from five different bph gene clusters. These results suggest that bphK genes, although not essential, fulfill a strain-specific function related to the utilization of BPs by their host organisms. The usefulness of BphK as a reporter enzyme for monitoring the expression of catabolic pathways is discussed.

Direct measurement of the current-phase relation of a superfluid 3He-B weak link

Direct measurements of the current-phase relation, I versus Deltaphi, for a weak link coupling two reservoirs of B-phase superfluid helium-3 (3He-B) were made over a wide range of temperatures. The weak link consists of a square array of 100-nanometer-diameter apertures. For temperatures T such that T/Tc >/= 0.6 (where Tc is the superfluid transition temperature), I approximately sin(Deltaphi). At lower temperatures, I(Deltaphi) approaches a straight line. Several remarkable phenomena heretofore inaccessible to superconducting Josephson junctions, including direct observation of quantum oscillations and continuous knowledge of Deltaphi, were also observed.

The biphenyl/polychlorinated biphenyl-degradation locus (bph) of Pseudomonas sp. LB400 encodes four additional metabolic enzymes

The bph locus of Pseudomonas sp. LB400, encoding biphenyl/polychlorinated biphenyl (PCB) degradation, contains a region of about 3.5 kb of hitherto unknown function, between bphC and bphD. This DNA segment has now been characterized. Four structural genes have been located and identified by a combination of expression cloning, enzyme activity tests and DNA sequencing. The region contains four closely spaced cistrons (bphKHJI) encoding a glutathione S-transferase (GST), a 2-hydroxypenta-2,4-dienoate hydratase, an acetaldehyde dehydrogenase (acylating) and a 4-hydroxy-2-oxovalerate aldolase, respectively. The latter three are enzymes required for conversion of the aliphatic end product of bphABCD-encoded catabolism of biphenyls to Krebs cycle intermediates. The discovery of these genes provides a rationale for growth of the strain on chlorinated biphenyls which yield chlorinated benzoates as dead-end metabolites. The sequences of the enzymes involved are 54-71% identical to those of homologous enzymes encoded by the dmp and xyl operons. The role of the GST in the degradation of biphenyls is less clear, but since it was found to contain, in the putative xenobiotic substrate-binding domain, a region which shares about 29% of identical amino acids with a bacterial tetrachlorohydroquinone dehalogenase, it may be involved in dehalogenation of PCB-degradative intermediates.