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With growing adoption of coronary computed tomographic angiography (CTA), there is increasing evidence for and interest in the prognostic importance of atherosclerotic plaque volume. Manual tools for plaque segmentation are cumbersome, and their routine implementation in clinical practice is limited. The aim of this study was to develop nomographic quantitative plaque values from a large consecutive multicenter cohort using coronary CTA. Quantitative assessment of total atherosclerotic plaque and plaque subtype volumes was performed in patients undergoing clinically indicated coronary CTA, using an Artificial Intelligence–Enabled Quantitative Coronary Plaque Analysis tool. A total of 11,808 patients were included in the analysis; their mean age was 62.7 ± 12.2 years, and 5,423 (45.9%) were women. The median total plaque volume was 223 mm3 (IQR: 29-614 mm3) and was significantly higher in male participants (360 mm3; IQR: 78-805 mm3) compared with female participants (108 mm3; IQR: 10-388 mm3) (P < 0.0001). Total plaque increased with age in both male and female patients. Younger patients exhibited a higher prevalence of noncalcified plaque. The distribution of total plaque volume and its components was reported in every decile by age group and sex. The authors developed pragmatic age- and sex-stratified percentile nomograms for atherosclerotic plaque measures using findings from coronary CTA. The impact of age and sex on total plaque and its components should be considered in the risk-benefit analysis when treating patients. Artificial Intelligence–Enabled Quantitative Coronary Plaque Analysis work flows could provide context to better interpret coronary computed tomographic angiographic measures and could be integrated into clinical decision making. [Display omitted] [ABSTRACT FROM AUTHOR]

Preprocedural computed tomography (CT) workup with assessment of virtual transcatheter heart valve-to-coronary ostia (VTC) distance and transcatheter heart valve-to-sinus (VTS) distances is recommended to assess the risk of coronary obstruction following valve-in-valve (ViV) transcatheter aortic valve replacement (TAVR). The authors sought to investigate the agreement of predicted VTC and VTS distances and observed post-TAVR anatomy on CT and their relationship with transcatheter heart valve (THV) expansion and deployment conditions. Fifty-one patients who underwent a balloon-expandable ViV procedure were included in this study. The expansion of the THV stent frame was evaluated at 4 levels: THV inflow, surgical heart valve (SHV) sewing ring, SHV outflow, and THV outflow. Assessment of the VTC/VTS distances was performed on the pre-TAVR CT, and THV-to-coronary ostia and THV-to-sinus distances were assessed on the post-TAVR CT. Following the ViV procedure, the THV stent frame flared toward the outflow but was generally underexpanded at all levels, particularly at the SHV sewing ring level. Postdilatation impacted the extent of THV expansion, resulting in greater expansion than nominal balloon filling at all 4 THV levels (P < 0.001). Observed THV-to-coronary ostia distances were systematically larger than predicted by the VTC distance (mean difference 1.25 ±1.28 mm) in patients with nominal balloon filling but systematically smaller in case of postdilatation (mean difference −0.45 ± 0.52 mm). A similar relationship was observed between VTS and THV-to-sinus distance measurements. With nominal balloon filling, VTC and VTS distances underestimate postprocedural distances due to THV frame underexpansion. However, postdilatation may lead to distances smaller than predicted due to THV overexpansion at the outflow level. [Display omitted] [ABSTRACT FROM AUTHOR]

There are limited data on the effect of bioprosthetic valve remodeling (BVR) on transcatheter heart valve (THV) expansion and function following valve-in-valve (VIV) transcatheter aortic valve replacement (TAVR) in a nonfracturable surgical heart valve (SHV). This study sought to assess the impact of BVR of nonfracturable SHVs on THVs after VIV implantation. VIV TAVR was performed using 23-mm SAPIEN3 (S3, Edwards Lifesciences) or 23/26-mm Evolut Pro (Medtronic) THVs implanted in 21/23-mm Trifecta (Abbott Structural Heart) and 21/23-mm Hancock (Medtronic) SHVs with BVR performed with a noncompliant TRUE balloon (Bard Peripheral Vascular Inc). Hydrodynamic assessment was performed, and multimodality imaging including micro–computed tomography was performed before and after BVR to assess THV and SHV expansion. BVR resulted in limited improvement of THV expansion. The largest gain in expansion was observed for the S3 in the 21-mm Trifecta with up to a 12.7% increase in expansion at the outflow of the valve. Minimal change was observed at the level of the sewing ring. The Hancock was less amenable to BVR with lower final expansion dimensions than the Trifecta. BVR also resulted in notable surgical post flaring of up to 17.6°, which was generally more marked with the S3 than with the Evolut Pro. Finally, BVR resulted in very limited improvement in hydrodynamic function. Severe pinwheeling was observed with the S3, which improved slightly but persisted despite BVR. When performing VIV TAVR inside a Trifecta and Hancock SHV, BVR had a limited impact on THV expansion and resulted in SHV post flaring with unknown consequences on coronary obstruction risk and long-term THV function. [Display omitted] [ABSTRACT FROM AUTHOR]

With growing adoption of coronary computed tomographic angiography (CTA), there is increasing evidence for and interest in the prognostic importance of atherosclerotic plaque volume. Manual tools for plaque segmentation are cumbersome, and their routine implementation in clinical practice is limited. The aim of this study was to develop nomographic quantitative plaque values from a large consecutive multicenter cohort using coronary CTA. Quantitative assessment of total atherosclerotic plaque and plaque subtype volumes was performed in patients undergoing clinically indicated coronary CTA, using an Artificial Intelligence-Enabled Quantitative Coronary Plaque Analysis tool. A total of 11,808 patients were included in the analysis; their mean age was 62.7±12.2 years, and 5,423 (45.9%) were women. The median total plaque volume was 223 mm3 (IQR: 29-614 mm3) and was significantly higher in male participants (360 mm3; IQR: 78-805 mm3) compared with female participants (108 mm3; IQR: 10-388 mm3)(P < 0.0001). Total plaque increased with age in both male and female patients. Younger patients exhibited a higher prevalence of noncalcified plaque. The distribution of total plaque volume and its components was reported in every decile by age group and sex. The authors developed pragmatic age- and sex-stratified percentile nomograms for atherosclerotic plaque measures using findings from coronary CTA. The impact of age and sex on total plaque and its components should be considered in the risk-benefit analysis when treating patients. Artificial Intelligence-Enabled Quantitative Coronary Plaque Analysis work flows could provide context to better interpret coronary computed tomographic angiographic measures and could be integrated into clinical decision making. [ABSTRACT FROM AUTHOR]

Limited evidence is available regarding valve-in-valve (VIV) intervention with the ACURATE neo transcatheter heart valve (THV). Low implantation has demonstrated leaflet interaction between the surgical bioprosthesis and the THV, leading to impaired hydrodynamic performance. It is unknown if commissural alignment (CA) can affect this phenomenon. Novel techniques have now been developed to achieve CA with the ACURATE neo THV. The aim of this study was to assess the impact of commissural misalignment (CMA) on hydrodynamic function following VIV intervention with the ACURATE neo THV using a bench model. VIV intervention was performed with the ACURATE neo (a self-expanding THV with supra-annular leaflet position) implanted deep in the surgical bioprosthetic aortic valve (Mitroflow). Hydrodynamic function at CA (0°) and 3 different degrees of CMA (30°, 60°, and 90°) was tested. As per the International Organization for Standardization, a regurgitant fraction <20% is considered optimal. Following VIV, the central THV regurgitant fraction at 0°, 30°, 60°, and 90° of CMA was 8.6% ± 2.0%, 30.3% ± 12.0%, 42.6% ± 11.9%, and 66.7% ± 25.4% (P < 0.0001), respectively. On high-speed video there was no evidence of leaflet interaction at CA, whereas at 30°, 60°, and 90° of CMA there was clear evidence of THV leaflet interaction with those of the surgical valve, leading to impaired leaflet closure and to severe central THV regurgitation. In VIV using the ACURATE neo THV at deep implantation, increasing degree of CMA was associated with THV leaflet interaction with those of the surgical valve and worsening regurgitant fraction. THV leaflet interaction was prevented when there was CA. [Display omitted] [ABSTRACT FROM AUTHOR]

The implications and potential challenges of coronary access after redo transcatheter aortic valve replacement (TAVR) are unknown. The authors sought to evaluate the impact of different transcatheter heart valve (THV) designs, neoskirt height, implant technique, and cell misalignment on coronary access after redo TAVR. Different THV designs (Sapien 3 [Edwards Lifesciences LLC], Evolut Pro [Medtronic], ACURATE neo [Boston Scientific Corporation], and Portico [Abbott Structural Heart]) and sizes were implanted inside Sapien XT (Edwards Lifesciences LLC) and Evolut R (Medtronic) THVs, which were modeled as the "failed" THVs, at different implant depths. Valve combinations underwent micro–computed tomography to determine the neoskirt height and dimensions of the lowest accessible cell for potential coronary access. This was compared with dimensions of 6-F/7-F/8-F coronary guiding catheters. Redo TAVR combinations resulted in a wide range of neoskirt heights (15.4-31.6 mm) and a variable diameter of the lowest accessible cell (1.9-21.8 mm). An ACURATE neo implanted in a Sapien XT resulted in the largest accessible cells, whereas a Portico implanted in a Sapien XT resulted in the lowest neoskirt heights. The smallest accessible cell was observed in the Evolut Pro–in–Evolut R configuration with higher neoskirt heights. Redo TAVR in a tall frame valve with supra-annular leaflets caused a taller neoskirt height. In Evolut-in-Evolut combinations, misalignment of the cells of the 2 THVs reduced the cell area by 30% to 50% compared with an aligned configuration. This study demonstrates that different redo TAVR combinations are not equivalent in terms of future coronary access. Redo TAVR using a tall frame valve in a failed tall frame valve and misaligned cells may lead to potentially challenging coronary access. [Display omitted] [ABSTRACT FROM AUTHOR]

Bioprosthetic valve thrombosis may have implications for valve function and durability. Using a novel glycoprotein IIb/IIIa receptor radiotracer 18F-GP1, we investigated whether positron emission tomography (PET)-computed tomography (CT) could detect thrombus formation on bioprosthetic aortic valves. Ex vivo experiments were performed on human platelets and explanted bioprosthetic aortic valves. In a prospective cross-sectional study, patients with either bioprosthetic or normal native aortic valves underwent echocardiography, CT angiography, and 18F-GP1 PET-CT. Flow cytometric analysis, histology, immunohistochemistry, and autoradiography demonstrated selective binding of 18F-GP1 to activated platelet glycoprotein IIb/IIIa receptors and thrombus adherent to prosthetic valves. In total, 75 participants were recruited: 53 with bioprosthetic valves (median time from implantation 37 months [IQR: 12-80 months]) and 22 with normal native aortic valves. Three participants had obstructive valve thrombosis, and a further 3 participants had asymptomatic hypoattenuated leaflet thickening on CT angiography. All bioprosthetic valves, but none of the native aortic valves, demonstrated focal 18F-GP1 uptake on the valve leaflets: median maximum target-to-background ratio 2.81 (IQR: 2.29-3.48) vs 1.43 (IQR: 1.28-1.53) (P < 0.001). Higher 18F-GP1 uptake was independently associated with duration of valve implantation and hypoattenuated leaflet thickening. All 3 participants with obstructive valve thrombosis were anticoagulated for 3 months, leading to resolution of their symptoms, improvement in mean valve gradients, and a reduction in 18F-GP1 uptake. Adherence of activated platelets is a common and sustained finding on bioprosthetic aortic valves. 18F-GP1 uptake is higher in the presence of thrombus, regresses with anticoagulation, and has potential use as an adjunctive clinical tool. (18F-GP1 PET-CT to Detect Bioprosthetic Aortic Valve Thrombosis; NCT04073875) [Display omitted] [ABSTRACT FROM AUTHOR]

The aim of this study was to describe the potential of 18F-sodium fluoride (18F-NaF) positron emission tomography (PET) to identify graft vasculopathy and to investigate the influence of coronary artery bypass graft (CABG) surgery on native coronary artery disease activity and progression. As well as developing graft vasculopathy, CABGs have been proposed to accelerate native coronary atherosclerosis. Patients with established coronary artery disease underwent baseline 18F-NaF PET, coronary artery calcium scoring, coronary computed tomographic angiography, and 1-year repeat coronary artery calcium scoring. Whole-vessel coronary microcalcification activity (CMA) on 18F-NaF PET and change in calcium scores were quantified in patients with and without CABG surgery. Among 293 participants (mean age 65 ± 9 years, 84% men), 48 (16%) underwent CABG surgery 2.7 years [IQR: 1.4-10.4 years] previously. Although all arterial and the majority (120 of 128 [94%]) of vein grafts showed no 18F-NaF uptake, 8 saphenous vein grafts in 7 subjects had detectable CMA. Bypassed native coronary arteries had 3 times higher CMA values (2.1 [IQR: 0.4-7.5] vs 0.6 [IQR: 0-2.7]; P < 0.001) and greater progression of 1-year calcium scores (118 Agatston unit [IQR: 48-194 Agatston unit] vs 69 [IQR: 21-142 Agatston unit]; P = 0.01) compared with patients who had not undergone CABG, an effect confined largely to native coronary plaques proximal to the graft anastomosis. In sensitivity analysis, bypassed native coronary arteries had higher CMA (2.0 [IQR: 0.4-7.5] vs 0.8 [IQR: 0.3-3.2]; P < 0.001) and faster disease progression (24% [IQR: 16%-43%] vs 8% [IQR: 0%-24%]; P = 0.002) than matched patients (n = 48) with comparable burdens of coronary artery disease and cardiovascular comorbidities in the absence of bypass grafting. Native coronary arteries that have been bypassed demonstrate increased disease activity and more rapid disease progression than nonbypassed arteries, an observation that appears independent of baseline atherosclerotic plaque burden. Microcalcification activity is not a dominant feature of graft vasculopathy. [Display omitted] [ABSTRACT FROM AUTHOR]

In the absence of disease impacting the coronary arteries or myocardium, there exists a linear relationship between vessel volume and myocardial mass to ensure balanced distribution of blood supply. This balance may be disturbed in diseases of either the coronary artery tree, the myocardium, or both. However, in contemporary evaluation the coronary artery anatomy and myocardium are assessed separately. Recently the coronary lumen volume to myocardial mass ratio (V/M), measured noninvasively using coronary computed tomography angiography (CTCA), has emerged as an integrated measure of myocardial blood supply and demand in vivo. This has the potential to yield new insights into diseases where this balance is altered, thus impacting clinical diagnoses and management. In this review, we outline the scientific methodology underpinning CTCA-derived measurement of V/M. We describe recent studies describing alterations in V/M across a range of cardiovascular conditions, including coronary artery disease, cardiomyopathies and coronary microvascular dysfunction. Lastly, we highlight areas of unmet research need and future directions, where V/M may further enhance our understanding of the pathophysiology of cardiovascular disease. [Display omitted] • Coronary luminal volume demonstrates a strong linear relationship to myocardial mass which can be affected by diseases of the coronaries and myocardium. • CTCA offers the ability to extract accurate 3D model of the coronary geometry and volumetric assessment of left ventricular mass, enabling calculation of the V/M ratio. • CCTA-derived V/M can provide insight into vascular health such as in microvascular angina and hypertrophic cardiomyopathy. • Future studies will need to explore whether V/M is modifiable and whether improvements in V/M are associated with improved clinical outcomes. The coronary lumen volume to myocardial mass ratio (V/M), measured noninvasively using coronary computed tomography angiography (CTCA), has emerged as an integrated measure of myocardial blood supply and demand. This has the potential to yield new insights into diseases where this balance is altered, thus impacting clinical diagnoses and management.In this review, we outline the scientific methodology underpinning CTCA-derived measurement of V/M. We describe recent studies describing alterations in V/M across a range of cardiovascular conditions and highlight areas of unmet research need and future directions, where V/M may further enhance our understanding of the pathophysiology of cardiovascular disease. [ABSTRACT FROM AUTHOR]

To investigate potential differences in plaque progression (PP) between in East Asians and Caucasians as well as to determine clinical predictors of PP in East Asians. Studies have demonstrated differences in cardiovascular risk factors as well as plaque burden and progression across different ethnic groups. The study comprised 955 East Asians (age 60.4 ​± ​9.3 years, 50.9% males) and 279 Caucasians (age 60.4 ​± ​8.6 years, 74.5% males) who underwent two serial coronary computed tomography angiography (CCTA) studies over a period of at least 24 months. Patients were enrolled and analyzed from the PARADIGM (P rogression of A the R osclerotic Pl A que D eterm I ned by Computed Tomo G raphic Angiography I M aging) registry. After propensity-score matching, plaque composition and progression were compared between East Asian and Caucasian patients. Within East Asians, the plaque progression group (defined as plaque volume at follow-up CCTA minus plaque volume at baseline CCTA> 0) was compared to the no PP group to determine clinical predictors for PP in East Asians. In the matched cohort, baseline volumes of total plaque as well as all plaque subtypes were comparable. There was a trend towards increased annualized plaque progression among East Asians compared to Caucasians (18.3 ​± ​24.7 ​mm3/year vs 16.6 ​mm3/year, p ​= ​0.054). Among East Asians, 736 (77%) had PP. East Asians with PP had more clinical risk factors and higher plaque burden at baseline (normalized total plaque volume of144.9 ​± ​233.3 ​mm3 vs 36.6 ​± ​84.2 ​mm3 for PP and no PP, respectively, p ​< ​0.001). Multivariate logistic regression analysis showed that baseline normalized plaque volume (OR: 1.10, CI: 1.10–1.30, p ​< ​0.001), age (OR: 1.02, CI: 1.00–1.04, p ​= ​0.023) and body mass index (OR: 2.24, CI: 1.01–1.13, p ​= ​0.024) were all predictors of PP in East Asians. Clinical events, driven mainly by percutaneous coronary intervention, were higher among the PP group with a total of 124 (16.8%) events compared to 22 (10.0%) in the no PP group (p ​= ​0.014). East Asians and Caucasians had comparable plaque composition and progression. Among East Asians, the PP group had a higher baseline plaque burden which was associated with greater PP and increased clinical events. [ABSTRACT FROM AUTHOR]

This study sought to determine the degree of Evolut (Medtronic) leaflet pinning, diameter expansion, leaflet overhang, and performance at different implant depths of the balloon-expandable Sapien 3 (S3, Edwards Lifesciences LLC) transcatheter heart valve (THV) within the Evolut THV. Preservation of coronary access and flow is a major factor when considering the treatment of failed Evolut THVs. An in vitro study was performed with 20-, 23-, 26-, and 29-mm S3 THVs deployed within 23-, 26-, 29-, and 34-mm Evolut R THVs, respectively. The S3 outflow was positioned at various depths at node 4, 5, and 6 of the Evolut R. Neoskirt height, leaflet overhang, performance, and Evolut R valve housing diameter expansion were assessed under physiological conditions as per ISO 5840-3 standard. The neoskirt height for the Evolut R was shorter when the S3 outflow was positioned at node 4 compared with node 6 (node 4 height for 23 mm = 16.3 mm, 26 mm = 17.1 mm, 29 mm = 18.3 mm, and 34 mm = 19.9 mm vs node 6 height for 23 mm = 23.9 mm, 26 mm = 23.4 mm, 29 mm = 24.7 mm, and 34 mm = 27 mm Evolut R). All configurations exhibited acceptable hydrodynamic performance irrespective of the degree of leaflet overhang, except the 29-mm S3 implanted in 34-mm Evolut R at node 4 (regurgitant fraction >20%). The valve housing radius of the index Evolut R increased when the S3 was implanted, with the increase ranging from 0 to 2.5 mm. Placement of the S3 at a lower implant position within an index Evolut R reduces the neoskirt height with no significant compromise to S3 valve function despite a higher degree of leaflet overhang. Low S3 implantation may facilitate future coronary access after redo transcatheter aortic valve replacement. [Display omitted] [ABSTRACT FROM AUTHOR]

The aim of this study was to evaluate flow dynamics in the aortic sinus and the neosinus (NS) after transcatheter heart valve (THV) implantation in valve-in-valve (ViV). Leaflet thrombosis may occur on THVs and affect performance and durability. Differences in flow dynamics may affect the risk for leaflet thrombosis. Hemodynamic assessment following THV implantation in a surgical aortic valve was performed in a left heart simulator under pulsatile physiological conditions. Assessment was performed using a 23-mm polymeric surgical aortic valve (not diseased) and multiple THV platforms, including self-expanding devices (26-mm Evolut, 23-mm Allegra, small ACURATE neo) and a balloon-expandable device (23-mm SAPIEN 3). Particle image velocimetry was performed to assess flow in the sinus and NS. Sinus and NS washout, shear stress, and velocity were calculated. Sinus and NS washout was fastest and approximately 1 cardiac cycle for each with the Evolut, ACURATE neo, and Allegra compared with the SAPIEN 3, with washout in 2 and 3 cardiac cycles, respectively. The Allegra showed the largest shear stress distribution in the sinus, followed by the SAPIEN 3. In the NS, all 4 valves showed equal likelihoods of occurrence of shear stress <1 Pa, but the Allegra showed the highest likelihoods of occurrence for shear stress >1 Pa. The velocities in the sinus and NS were 0.05, 0.078, 0.080, and 0.075 m/s for Evolut, SAPIEN 3, ACURATE neo, and Allegra ViV, respectively. Sinus and NS flow dynamics differ substantially among THVs after ViV. Self-expanding supra-annular valves seem to have faster washouts compared with an equivalent-size balloon-expandable THV. [Display omitted] [ABSTRACT FROM AUTHOR]

The aim of the current study was to explore the impact of plaque calcification in terms of absolute calcified plaque volume (CPV) and in the context of its percentage of the total plaque volume at a lesion and patient level on the progression of coronary artery disease. Coronary artery calcification is an established marker of risk of future cardiovascular events. Despite this, plaque calcification is also considered a marker of plaque stability, and it increases in response to medical therapy. This analysis included 925 patients with 2,568 lesions from the PARADIGM (Progression of Atherosclerotic Plaque Determined by Computed Tomographic Angiography Imaging) registry, in which patients underwent clinically indicated serial coronary computed tomography angiography. Plaque calcification was examined by using CPV and percent CPV (PCPV), calculated as (CPV/plaque volume) × 100 at a per-plaque and per-patient level (summation of all individual plaques). CPV was strongly correlated with plaque volume (r = 0.780; p < 0.001) at baseline and with plaque progression (r = 0.297; p < 0.001); however, this association was reversed after accounting for plaque volume at baseline (r = –0.146; p < 0.001). In contrast, PCPV was an independent predictor of a reduction in plaque volume (r = –0.11; p < 0.001) in univariable and multivariable linear regression analyses. Patient-level analysis showed that high CPV was associated with incident major adverse cardiac events (hazard ratio: 3.01: 95% confidence interval: 1.58 to 5.72), whereas high PCPV was inversely associated with major adverse cardiac events (hazard ratio: 0.529; 95% confidence interval: 0.229 to 0.968) in multivariable analysis. Calcified plaque is a marker for risk of adverse events and disease progression due to its strong association with the total plaque burden. When considered as a percentage of the total plaque volume, increasing PCPV is a marker of plaque stability and reduced risk at both a lesion and patient level. (Progression of Atherosclerotic Plaque Determined by Computed Tomographic Angiography Imaging [PARADIGM]; NCT02803411) [ABSTRACT FROM AUTHOR]

CT measurement of supra-annular area (SA) has been proposed as an alternative to annular area (AA) for sizing of trancatheter valves in biscuspid aortic valves (BAV). This study examines the reproducibility of SA and AA measurements and their potential impact on downstream transcatheter heart valve sizing and clinical outcomes. 44 consecutive patients (mean age: 73 ± 15 years, 57% male) undergoing CTA with subsequent SAPIEN 3 valve insertion for severe bicuspid aortic stenosis (AS) were included. AA was measured at the basal ring. SA was measured by generating a circle defined by the intercommisural distance. AA and SA were measured by 2 independent observers. Baseline characteristics, TAVR procedural data, and discharge echocardiography data were collected. The SA was significantly larger than the AA (562 ± 146mm2 vs. 518 ± 112mm2,p = 0.013). Interobserver agreement was high using both techniques (ICC AA = 0.98,p < 0.001; SA = 0.80,p < 0.001), but with narrower limits of agreement with AA measurements (mean difference (limits of agreement): AA = −3mm2 (22; 19), SA = −16mm2 (−92; 76)). AA-based device sizing demonstrated substantial agreement with final valve inserted (κ = 0.72,p < 0.001), while SA demonstrated fair agreement (κ = 0.40,p < 0.001). There was no difference in post TAVR gradients, paravalvular leakage or valve success between patients with concordant sizing between AA and SA, and those in whom SA would have suggested an alternate valve size. Supra-annular sizing is less reproducible than annular sizing, with no difference in procedural complication rates in patients in whom supra-annular sizing would have altered the device size used. These results suggest no role for supra-annular sizing in current clinical practice. [ABSTRACT FROM AUTHOR]

The aim of this study was to examine the effect of different transcatheter heart valves (THVs) on valve leaflet displacement when deployed within bioprosthetic surgical valves and, thereby, risk for coronary obstruction. Coronary obstruction is a potentially devastating complication during valve-in-valve (ViV) transcatheter aortic valve replacement. Strategies such as provisional stenting and intentional bioprosthetic valve leaflet laceration have been developed to mitigate this risk. Alternatively, the use of a THV that retracts the bioprosthetic leaflet away from the coronary ostium may prevent coronary obstruction. A 25-mm J-Valve, a 26-mm Evolut Pro, and a 23-mm JenaValve were implanted into both a 25-mm Trifecta surgical valve and a 25-mm Mitroflow surgical valve. A 23-mm and a 26-mm SAPIEN 3 were deployed into the Trifecta and Mitroflow, respectively. Displacement of the surgical valve leaflets (retraction vs. expansion) was measured with implantation of each THV by measuring displacement angle and maximal displacement distance. Within both the Trifecta and Mitroflow valves, implantation of the J-Valve and JenaValve resulted in retraction of the surgical valve leaflets, and placement of the Evolut Pro and SAPIEN 3 resulted in tubular expansion of the surgical valve leaflets. There were significant differences in displacement angles and distances between both the J-Valve and JenaValve and the SAPIEN 3 and Evolut Pro (p < 0.0001). ViV implantation with new-generation THVs that directly interact with bioprosthetic valve leaflets results in surgical valve leaflet retraction. This might mitigate the risk for coronary obstruction in selected cases of ViV transcatheter aortic valve replacement and also facilitate coronary reaccess after ViV TAVR. [ABSTRACT FROM AUTHOR]

Coronary artery calcification is a significant contributor to reduced accuracy of coronary computed tomographic angiography (CTA) in the assessment of coronary artery disease severity. The aim of the current study is to assess the impact of a prototype calcium deblooming algorithm on the diagnostic accuracy of CTA. 40 patients referred for invasive catheter angiography underwent CTA and invasive catheter angiography. The CTA were reconstructed using a standard soft tissue kernel (CTA STAND) and a deblooming algorithm (CTA DEBLOOM). CTA studies were read with and without the deblooming algorithm blinded to the invasive coronary angiogram findings. Sensitivity, specificity, accuracy, positive predictive value and negative predictive value for the detection of stenosis ≥50% or ≥70% were evaluated using quantitative coronary angiography as the reference standard. Image quality was assessed using a 5-point scale, and the presence of image artifact recorded. All studies were diagnostic with 548 segments available for evaluation. Image score was 3.64 ± 0.72 with CTA DEBLOOM , versus 3.56 ± 0.72 with CTA STAND (p = 0.38). CTA DEBLOOM had significantly less calcium blooming artifact than CTA STAND (12.5% vs. 47.5%, p = 0.001). Based on a 50% stenosis threshold for defining significant disease, the Sensitivity/Specificity/PPV/NPV/Accuracy were 65.9/84.9/27.6/96.6/83.4 for CTA DEBLOOM and 75.0/81.9/26.6/97.4/81.4 for CTA STAND using a ≥50% threshold. CTA DEBLOOM specificity was significantly higher than CTA STAND (84.9% vs. 81.5%, p = 0.03), with no difference between the algorithms in sensitivity (p = 0.22), or accuracy (p = 0.15). These results remained unchanged when a stenosis threshold of ≥70% was used. Interobserver agreement was fair with both techniques (CTA DEBLOOM k = 0.38, CTA STAND k = 0.37). In this proof of concept study, coronary calcification deblooming using a prototype post-processing algorithm is feasible and reduces calcium blooming with an improvement of the specificity of the CTA exam. Coronary calcification deblooming using a prototype post-processing algorithm is feasible and significantly reduces calcium blooming with an improvement of the specificity of the CTA exam. [ABSTRACT FROM AUTHOR]

This study assessed the long-term durability of nominally deployed transcatheter heart valves (THV) to 1 billion cycles (equivalent to 25 years) and non-nominal (overexpansion, underexpansion, and elliptical) THV deployments to 200 million cycles (equivalent to 5 years) with accelerated wear testing. The long-term durability of THVs is currently unknown. As transcatheter aortic valve replacement expands to lower-risk patients, durability will be of increasing importance. SAPIEN 3 THVs, sized 20, 23, 26, and 29 mm were assessed. Nominally deployed THVs underwent hydrodynamic performance and mechanical durability as assessed with accelerated wear testing to 1 billion cycles. Magna Ease surgical valves were used as comparators. Durability of non-nominal THV deployments was tested to 200 million cycles. Valves were tested to International Standards Organization 5840:2013 standard. THV durability was excellent for both the nominal and non-nominal THV deployments to 1 billion and 200 million cycles, respectively. At 1 billion cycles the regurgitant fraction for the 20-, 23-, 26-, and 29-mm SAPIEN 3 was 0.92 ± 0.47%, 1.29 ± 0.04%, 1.73 ± 0.46%, and 2.47 ± 0.15%, respectively. There was also excellent durability in the comparator Magna Ease valves. The regurgitant fraction of non-nominal overexpanded (20 mm, 4.36 ± 0.53; 23 mm, 7.68 ± 1.39; 26 mm, 6.80 ± 1.17; 29 mm, 9.00 ± 0.37), underexpanded (20 mm, 3.06 ± 0.28; 23 mm, 4.46 ± 0.45; 26 mm, 7.72 ± 0.48; 29 mm, 8.65 ± 2.01), and elliptical (20 mm, 3.30 ± 0.38; 23 mm, 6.13 ± 0.94; 26 mm, 6.77 ± 1.22; 29 mm, 8.72 ± 0.24) THVs were excellent at 200 million cycles. Nominal SAPIEN 3 THVs demonstrated excellent durability, to an equivalent of 25-years wear. THV durability was similar to the comparator surgical valves tested. Non-nominal (overexpansion, underexpansion, and elliptical) THV deployments also had excellent durability to an equivalent of 5 years wear. [ABSTRACT FROM AUTHOR]

Abstract Objectives This study investigated processes causing leaflet thickening and structural valve degeneration (SVD). Background Although transcatheter aortic valve replacement (TAVR) has changed the treatment of aortic stenosis, concerns remain regarding SVD, potentially related to valve thrombosis and thickening, based on studies using computed tomography (CT). Detailed histological analyses are provided to help attain insights into these processes. Methods Explanted transcatheter heart valves (THVs) were evaluated for thrombosis, fibrosis, and calcification for quantification of leaflet thickness. Immunohistochemical and microscopy approaches were used to investigate SVD-associated mechanisms. Results THVs (n = 23) were obtained from 22 patients (median 81 years of age; 50% male) from 0 to 2,583 days post TAVR. Maximal leaflet thickness increased relative to implant duration (ρ = 0.427; p = 0.027). THVs explanted after >2 years were thicker than those explanted after <2 years (p = 0.007). All THVs had adherent thrombus on both aortic and ventricular sides, which beyond 60 days was seen in combination with fibrosis and beyond 4 years had calcification. Early thrombus formation (<60 days) occurred despite rapid endothelialization with an abnormal hyperplastic phenotype. Fibrosis was observed in 6 patients on both the aortic and the ventricular THV surfaces, remodeled over time, and was associated with matrix metalloproteinase-1 expression. Five THVs showed overt calcification associated with adherent thrombus and fibrosis. Conclusions There is a time-dependent degeneration of THVs consisting of thrombus formation, endothelial hyperplasia, fibrosis, tissue remodeling, proteinase expression, and calcification. Future investigation is needed to further understand these mechanisms contributing to leaflet thickening and SVD. Graphical abstract [ABSTRACT FROM AUTHOR]

Abstract Introduction Angina, myocardial ischemia, and coronary artery physiology in hypertrophic cardiomyopathy (HCM) are poorly understood. However, coronary computed tomography angiography (CCTA) with fractional flow reserve from CT (FFR CT) analysis offers a non-invasive method for evaluation of coronary artery volume to myocardial mass ratio (V/M) that may provide insight into such mechanisms. Thus, we sought to investigate changes in V/M in HCM. Methods A retrospective analysis was performed on 37 HCM patients and 37 controls matched for age, sex, and cardiovascular risk factors; CCTA-derived coronary artery lumen volume (V) and myocardial mass (M) were used to determine V/M. FFR CT values were calculated for the left anterior descending (LAD), left circumflex (LCx) and right coronary (RCA) arteries as well as the 3-vessel cumulative FFR CT values. Results HCM patients had significantly increased myocardial mass (176 ± 84 vs. 119 ± 27 g, p < 0.0001) and total coronary artery luminal volume (4112 ± 1139 vs. 3290 ± 924 mm3, p < 0.0001) that resulted from increases in segmented luminal volumes of both the left and right coronary artery systems. However, HCM patients had significantly decreased V/M (23.8 ± 5.9 vs. 26.5 ± 5.3 mm3/g; p = 0.026) which was further decreased when restricting V/M analysis to those HCM patients with septal hypertrophy (22.4 mm3/g, p = 0.01) that was mild-moderately predictive of HCM (AUC = 0.68). HCM patients also showed significantly lower nadir FFR CT values in the LCx (0.87 ± 0.06 vs. 0.91 ± 0.06, p = 0.02), and cumulative 3-vessel FFR CT values (2.58 ± 0.18 vs. 2.63 ± 0.14, p = 0.006). Conclusions HCM patients demonstrate significantly greater coronary volume. Despite this, HCM patients suffer from decreased V/M. Further prospective studies evaluating the relationship between V/M, angina, and heart failure in HCM are needed. [ABSTRACT FROM AUTHOR]

Abstract Objectives This study aimed to determine the rate and extent of plaque progression (PP), changes in plaque features, and clinical predictors of PP in patients with diabetes mellitus (DM). Background The natural history of coronary PP in patients with DM is not well established. Methods A total of 1,602 patients (age 61.3 ± 9.0 years; 60.3% men; median scan interval 3.8 years) who underwent serial coronary computed tomography angiography over a period of at least 24 months were enrolled and analyzed from the PARADIGM (Progression of Atherosclerotic Plaque Determined by Computed Tomographic Angiography Imaging) trial. Study endpoints were changes in plaque features in diabetics with PP and risk factors for PP by serial coronary computed tomography angiography between patients with and without DM. PP was defined if plaque volume at follow-up minus plaque volume at baseline was >0. Results DM was an independent risk factor for PP (84.6%; 276 of 326 patients with PP) in multivariate analysis (odds ratio [OR]: 1.526; 95% confidence interval [CI]: 1.100 to 2.118; p = 0.011). Independent risk factors for PP in patients with DM were male sex (OR: 1.485; 95% CI: 1.003 to 2.199; p = 0.048) and mean plaque burden at baseline ≥75% (OR: 3.121; 95% CI: 1.701 to 5.725; p ≤0.001). After propensity matching, percent changes in overall plaque volume (30.3 ± 36.9% in patients without DM and 36.0 ± 29.7% in those with DM; p = 0.032) and necrotic core volume (−7.0 ± 35.8% in patients without DM and 21.5 ± 90.5% in those with DM; p = 0.007) were significantly greater in those with DM. The frequency of spotty calcification, positive remodeling, and burden of low-attenuation plaque were significantly greater in patients with DM. Conclusions People with DM experience greater PP, particularly significantly greater progression in adverse plaque, than those without DM. Male sex and mean plaque burden >75% at baseline were identified as independent risk factors for PP. Graphical abstract [ABSTRACT FROM AUTHOR]

Abstract Background Scanxiety, the anxiety/stress associated with an imaging test, has never been evaluated in relation to coronary CT angiography (Coronary CTA). As it could impact heart rate and thereby affect image quality of Coronary CTA, we aimed to evaluate the prevalence, severity, and impact of scanxiety on quality and interpretability of Coronary CTA. Methods 366 consecutive patients were prospectively presented with a clinical questionnaire comprising two tests to evaluate their scan-related anxiety: the Impact of Event IES-6 (6 questions, final score 0–24) and a visual stress-scale (1 question, score 1–10). Patient demographics, heart rate and final image quality scored by two readers were recorded. Potential independent correlations were sought between IES-6 scanxiety level and image quality, heart rate variability and demographics, using an ordinal logistic regression model. Results 344 patients (59.9% men, 57.6 ± 10.7yo) completed the questionnaire. 74.1% (255 patients) reported some scan-related distress, with a mean IES-6 score of 4.1 ± 4.3 (range 0–18). There was no significant difference in terms of age, sex or indications for Coronary CTA between the non-anxious (IES-6 = 0) and the anxious (IES-6>0) patients. There was no significant independent correlation between image quality and IES-6 score (OR = 0.98, p = 0.62), nor between IES-6 score and heart rate variability (effect = −0.005, p = 0.97). Conclusion The prevalence of scan-related anxiety – aka scanxiety – in Coronary CTA patients is high (74.1%) but does not appear to impact image quality and interpretability. [ABSTRACT FROM AUTHOR]

Background The aim of the study is examine the impact of non-obstructive (<50%stenosis) left main (LM) disease on the natural history of coronary artery disease using serial coronary computed tomography angiography (CTA). Methods CTAs from the PARADIGM (Progression of atherosclerotic plaque determined by computed tomographic angiography imaging) study, a prospective multinational registry of patients who underwent serial CTA at a ≥2 year interval were analyzed. Those without evidence of CAD on their baseline scan were excluded, as were those with obstructive left main disease. Coronary artery vessels and their branches underwent quantification of: plaque volume and composition; diameter stenosis; presence of high-risk plaque. Results Of 944 (62 ± 9 years, 60% male) who had evidence of CAD at baseline, 444 (47%) had LM disease. Those with LM disease had a higher baseline plaque volume (194.8 ± 221mm3 versus 72.9 ± 84.3mm3, p < 0.001) and a higher prevalence of high-risk plaque (17.5% versus 13%, p < 0.001) than those without LM disease. On multivariable general linear model, patients with LM disease had greater annual rates of progression of total (26.5 ± 31.4mm3/yr versus 14.9 ± 20.1mm3/yr, p < 0.001) and calcified plaque volume (17 ± 24mm3/yr versus 7 ± 11mm3/yr, p < 0.001), with no difference in fibrous, fibrofatty or necrotic core plaque components. Conclusion The presence of non-obstructive LM disease is associated with greater rates of plaque progression and a higher prevalence of high-risk plaque throughout the entire coronary artery tree compared to CAD without LM involvement. Our data suggests that non-obstructive LM disease may be a marker for an aggressive phenotype of CAD that may benefit from more intensive treatment strategies. [ABSTRACT FROM AUTHOR]

Introduction A standardised approach to the interpretation of FFRCT data is currently lacking. We evaluated the rate of reclassification of FFRCT positivity using the FFRCT value distal to an anatomical stenoses compared to the lowest FFRCT value. Method Patients who underwent coronary CTA and FFRCT analysis were eligible. FFRCT value of ≤ 0.80 was considered positive. Positive FFRCT distal to stenosis was defined as those with a stenoses of ≥ 25% with an associated FFRCT value of ≤ 0.80 within 2cm distal to the lesion. Outcome data on subsequent invasive coronary angiography (ICA) and coronary revascularisation were collected with a minimum follow-up of 60 days to account for delay between referral for invasive testing and/or revascularisation and receiving the procedure. Result 192 patients (mean age 60.7 ± 10.6 years, 67.5% men) were included. FFRCT was positive for lowest FFRCT value in 55.7% of patients. Positive FFRCT value distal to stenosis was found in 31.3%. The overall reclassification rate of those positive for lowest FFRCT value to negative for FFRCT value distal to stenosis was 43.9% (p < 0.01). The reclassification rates were most pronounced for those with intermediate stenoses - 67% for those with < 50% stenoses, p < 0.01; 49% for 50–69% stenoses, p < 0.01. Amongst those who underwent ICA, the rate of revascularization was significant higher for those with positive FFRCT distal to stenosis compared to those positive for lowest FFRCT value (revascularization/ICA = 0.53 vs 0.44, p < 0.01). Conclusion Using FFRCT values distal to a anatomical stenoses, 44% of patients positive for lowest FFRCT value were reclassified as negative for FFRCT value distal to stenosis. Those who underwent ICA, the rate of revascularisation was higher amongst those with positive FFRCT distal to stenosis compared to those positive for lowest FFRCT value. [ABSTRACT FROM AUTHOR]

Background Microvascular angina (MVA) is an incompletely understood clinical entity. Computational analysis of coronary Computed Tomography Angiography (CTA) has shown an association between low coronary lumen volume to myocardial mass (V/M) ratio and lower Fractional Flow Reserve values, independent of plaque measures. We hypothesized that low V/M ratio may be present in patients with MVA. Methods A retrospective case-control analysis was performed using patients fulfilling guideline criteria for MVA with controls matched for age, gender, coronary risk factors and atherosclerotic plaque burden. V/M was extracted off site (Heartflow Inc; Redwood City, CA) employing allometric scaling laws that allow the definition of the coronary circulation beyond the epicardium. FFR CT values were calculated in the major epicardial coronary arteries for each group. Results A total of 30 patients with MVA and 32 matched controls were included in the study. Mean total coronary lumen volume (2302 mm 3 ± 109 vs 2978 mm 3 ± 134, p < 0.001) and mean myocardial mass (90.4 g ± 13.7 vs 100.4 g ± 20.1, p = 0.029) were lower in MVA patients compared to controls. Mean V/M ratio was significantly lower in MVA compared to controls (25.6 mm 3 /g ± 5.9 vs 30.0 mm 3 /g ± 6.5, p = 0.007; c-statistic 0.69). V/M ratio did not differ significantly between subclasses of angina severity (p = 0.747). No difference in mean nadir FFR CT values was found between MVA and control groups in the LAD (0.86 ± 0.07 vs 0.83 ± 0.07, p = 0.154), LCX (0.90 ± 0.05 vs 0.90 ± 0.06, p = 0.240) and RCA (0.90 ± 0.04 vs 0.90 ± 0.03, p = 0.773) vessels. Conclusion Patients with microvascular angina demonstrate a significantly lower coronary CTA-derived coronary volume/myocardial mass ratio than asymptomatic controls. [ABSTRACT FROM AUTHOR]

Objectives This study sought to determine if indexed effective orifice area (EOAi), using left ventricular outflow tract measured from computed tomography (EOAi CT ), reclassified prosthesis–patient mismatch (PPM) compared with conventional echocardiogram-defined measurements (EOAi TTE ). Background PPM does not predict mortality following transcatheter aortic valve replacement (TAVR). However, it is unknown if the EOAi CT of the left ventricular outflow tract improves risk stratification. Methods A total of 765 TAVR patients from the PARTNER II (Placement of Aortic Transcatheter Valves II) trial S3i cohort were evaluated. EOAi was calculated using the continuity equation, and the left ventricular outflow tract area was derived from baseline computed tomography. Traditional echocardiographic categories defined PPM: absent (>0.85 cm 2 /m 2 ), moderate (≥0.65 and ≤0.85 cm 2 /m 2 ), or severe (≤0.65 cm 2 /m 2 ). Correlation of EOAi CT and EOAi TTE to 1-year outcomes was performed. Results The incidence of PPM was 24% with EOA CT compared with 45% with EOAi TTE . Only 6% of PPM was graded severe by EOAi CT compared with 9% by EOAi TTE . EOAi TTE , but not EOAi CT , defined PPM showed association with reduced left ventricular mass regression (p = 0.03 vs. p = 0.52). There was no association between PPM and death or rehospitalization at 1 year with either modality. EOA CT was associated with minor stroke at 1 year (log-rank p = 0.04), and EOAi TTE with stroke/transient ischemic attack (log-rank p = 0.030). Furthermore, when subjects with mild or greater paravalvular regurgitation were excluded, the presence of PPM did not show association with any outcome. Conclusions EOAi CT downgrades frequency and severity of PPM in patients after TAVR, and was not associated with mortality 1 year after TAVR. EOAi TTE , but not EOAi CT , was associated with less left ventricular mass regression. [ABSTRACT FROM AUTHOR]

The occurrence of clonal perturbations and leukemia in patients transplanted with gamma-retroviral (RV) vector-transduced autologous hematopoietic stem and progenitor cells (HSPCs) has stimulated extensive investigation, demonstrating that proviral insertions may perturb adjacent proto-oncogene expression. Although enhancer-deleted lentiviruses are less likely to result in insertional oncogenesis, there is evidence that they may perturb transcript splicing, and one patient with a benign clonal expansion of lentivirally transduced HPSC has been reported. The rhesus macaque model provides an opportunity for informative long-term analysis to ask whether transduction impacts on long-term HSPC properties. We used two techniques to examine whether lentivirally transduced HSPCs from eight rhesus macaques transplanted 1-13.5 years previously are perturbed at a population level, comparing telomere length as a measure of replicative history and gene expression profile of vector positive versus vector negative cells. There were no differences in telomere lengths between sorted GFP+ and GFP− blood cells, suggesting that lentiviral (LV) transduction did not globally disrupt replicative patterns. Bone marrow GFP+ and GFP− CD34+ cells showed no differences in gene expression using unsupervised and principal component analysis. These studies did not uncover any global long-term perturbation of proliferation, differentiation, or other important functional parameters of transduced HSPCs in the rhesus macaque model. [ABSTRACT FROM AUTHOR]

Activation of proto-oncogenes by retroviral insertion is an important issue delaying clinical development of gene therapy. We have reported the nonrandom persistence of hematopoietic clones with vector insertions within the MDS1/EVI1 locus following transplantation of rhesus macaques. We now ask whether prolonged culture of transduced CD34+ cells before transplantation selects for clones with insertions in the MDS1/EVI11 or other proto-oncogene loci. CD34+ cells were transduced with standard retroviral vectors for 4 days and then continued in culture for an additional 6 days before transplantation. A 15% of insertions identified in granulocytes 6 months post-transplant were in MDS1/EVI11, significantly increased compared to the frequency in animals transplanted with cells immediately following transduction. MDS1/EVI1 clones became more dominant over time post-transplantation in one animal that was followed long term, accompanied by an increased overall copy number of vector-containing granulocytes, with one MDS1/EVI1 clone eventually accounting for 100% of transduced granulocytes and marrow colony-forming unit (CFU). This vector insertion increased the expression of Evi1 mRNA. There was no overrepresentation of MDS1/EVI1 insertions contributing to lymphoid lineages. Strategies involving prolonged ex vivo expansion of transduced cells may increase the risk of genotoxicity. [ABSTRACT FROM AUTHOR]

There has been significant progress toward clinically relevant levels of retroviral gene transfer into hematopoietic stem cells (HSC), and the therapeutic potential of HSC-based gene transfer has been convincingly demonstrated in children with severe combined immunodeficiency syndrome (SCID). However, the subsequent development of leukemia in two children with X-linked SCID who were apparently cured after transplantation of retrovirally corrected CD34+ cells has raised concerns regarding the safety of gene therapy approaches utilizing integrating vectors. Nonhuman primates and dogs represent the best available models for gene transfer safety and efficacy and are particularly valuable for evaluation of long-term effects. We have followed 42 rhesus macaques, 23 baboons, and 17 dogs with significant levels of gene transfer for a median of 3.5 years (range 1–7) after infusion of CD34+ cells transduced with retroviral vectors expressing marker or drug-resistance genes. None developed abnormal hematopoiesis or leukemia. Integration site analysis confirmed stable, polyclonal retrovirally marked hematopoiesis, without progression toward mono- or oligoclonality over time. These results suggest that retroviral integrations using replication-incompetent vectors, at copy numbers achieved using standard protocols, are unlikely to result in leukemogenesis and that patient- or transgene-specific factors most likely contributed to the occurrence of leukemia in the X-SCID gene therapy trial. [Copyright &y& Elsevier]

: ObjectiveEx vivo expansion of primitive hematopoietic cells remains of interest for gene therapy and transplantation. Previous studies reported loss of repopulating activity following culture of cells for more than 4–7 days in the presence of cytokines or stromal cells. In the current study, we investigated whether prolonged culture and transduction in the presence of the carboxy-terminal portion of fibronectin (FN) could maintain or expand retrovirally transduced repopulating hematopoietic stem cells (HSCs).: MethodsThe impact of culture and transduction on rhesus macaque CD34+ peripheral blood stem cells (PBSCs) was assessed in the presence of FN and stimulatory cytokines. A competitive repopulation design using up to three retroviral vectors allowed direct comparison of repopulating activity between cells transduced and cultured for 4 days vs 10 days.: ResultsIn the first animal, all cells were cultured and transduced for 10 days, with one vector used on days 0–4 and a second on days 4–10. There was stable long-term marking from both vectors, indicating that cells cycling both early and late could engraft. In three animals, we compared cells that were cryopreserved following a 4-day transduction to cells that were continued in culture for an additional 6 days. Total marking derived from the 10-day expanded cells was significantly higher than marking from the 4-day cultured cells.: ConclusionsThese results suggest that culture on FN support allows prolonged ex vivo maintenance and even expansion of transduced repopulating stem cells. [Copyright &y& Elsevier]