Soo Teik Lim

Simplified Models of Non-Invasive Fractional Flow Reserve Based on CT Images.

Invasive fractional flow reserve (FFR) is the gold standard to assess the functional coronary stenosis. The non-invasive assessment of diameter stenosis (DS) using coronary computed tomography angiography (CTA) has high false positive rate in contrast to FFR. Combining CTA with computational fluid dynamics (CFD), recent studies have shown promising predictions of FFRCT for superior assessment of lesion severity over CTA alone. The CFD models tend to be computationally expensive, however, and require several hours for completing analysis. Here, we introduce simplified models to predict noninvasive FFR at substantially less computational time. In this retrospective pilot study, 21 patients received coronary CTA. Subsequently a total of 32 vessels underwent invasive FFR measurement. For each vessel, FFR based on steady-state and analytical models (FFRSS and FFRAM, respectively) were calculated non-invasively based on CTA and compared with FFR. The accuracy, sensitivity, specificity, positive predictive value and negative predictive value were 90.6% (87.5%), 80.0% (80.0%), 95.5% (90.9%), 88.9% (80.0%) and 91.3% (90.9%) respectively for FFRSS (and FFRAM) on a per-vessel basis, and were 75.0%, 50.0%, 86.4%, 62.5% and 79.2% respectively for DS. The area under the receiver operating characteristic curve (AUC) was 0.963, 0.954 and 0.741 for FFRSS, FFRAM and DS respectively, on a per-patient level. The results suggest that the CTA-derived FFRSS performed well in contrast to invasive FFR and they had better diagnostic performance than DS from CTA in the identification of functionally significant lesions. In contrast to FFRCT, FFRSS requires much less computational time.

Iliofemoral anatomy among Asians: Implications for transcatheter aortic valve implantation

BACKGROUND/OBJECTIVESnThis study aims to examine iliofemoral anatomy and predictors of vessel size and tortuosity in Asian patients as transfemoral transcatheter aortic valve implantation (TAVI) may be limited by the smaller Asian physique.nnnMETHODSnCharacteristics and vessel dimensions of 549 patients undergoing ultrasonography were reviewed. The minimal luminal diameter (MLD) along the iliofemoral vasculature of each side was identified and the larger of the two sides was used to determine suitability for transfemoral TAVI.nnnRESULTSnThe mean age was 66 ± 11 years (68% males). Mean iliac MLD was 7.6 ± 1.7 mm, females smaller than males (7.2 ± 1.7 vs 7.8 ± 1.7, p<0.001). Mean iliac MLD decreased with age: 7.9 ± 1.7 mm, 7.4 ± 1.9 mm and 7.3 ± 1.6mm for ages <70 years, 70-79 years and ≥ 80 years respectively (p=0.038). Mean femoral MLD was 7.0 ± 1.7 mm, females smaller than males (6.3 ± 1.5mm vs 7.3 ± 1.8mm, p<0.001). Females were more likely than males to have iliac and femoral MLD <6mm (20% vs 12%, p=0.019 and 34% vs 21%, p=0.001). Independent predictors of smaller iliofemoral dimensions were female gender, lower body surface area, diabetes mellitus, dyslipidemia and smoking history. Significant iliac tortuosity was present in 11.8%, more frequent in males than females (15% vs 6%, p=0.005), and in those with logistic EuroSCORE ≥ 15 than <15 (27% vs 10%, p=0.001).nnnCONCLUSIONSnThis study establishes the mean iliac and femoral artery diameters in a cohort of relatively young Asian patients. Age and female gender were associated with smaller vessel dimension and several independent predictors of smaller vasculature and tortuosity were identified. These results have implications for TF TAVI in Asia.

Mechanical behavior of polymer-based vs . metallic-based bioresorbable stents

Bioresorbable scaffolds (BRS) were developed to overcome the drawbacks of current metallic drug-eluting stents (DES), such as late in-stent restenosis and caging of the vessel permanently. The concept of the BRS is to provide transient support to the vessel during healing before being degraded and resorbed by the body, freeing the vessel and restoring vasomotion. The mechanical properties of the BRS are influenced by the choice of the material and processing methods. Due to insufficient radial strength of the bioresorbable material, BRS often required large strut profile as compared to conventional metallic DES. Having thick struts will in turn affect the deliverability of the device and may cause flow disturbance, thereby increasing the incidence of acute thrombotic events. Currently, the bioresorbable poly-l-lactic acid (PLLA) polymer and magnesium (Mg) alloys are being investigated as materials in BRS technologies. The bioresorption process, mechanical properties, in vitro observations and clinical outcomes of PLLA-based and Mg-based BRS will be examined in this review.

Combined diagnostic performance of coronary computed tomography angiography and computed tomography derived fractional flow reserve for the evaluation of myocardial ischemia: A meta-analysis

BACKGROUNDnTo evaluate the combined diagnostic accuracy of coronary computed tomography angiography (CCTA) and computed tomography derived fractional flow reserve (FFRct) in patients with suspected or known coronary artery disease (CAD).nnnMETHODSnPubMed, The Cochrane library, Embase and OpenGray were searched to identify studies comparing diagnostic accuracy of CCTA and FFRct. Diagnostic test measurements of FFRct were either extracted directly from the published papers or calculated from provided information. Bivariate models were conducted to synthesize the diagnostic performance of combined CCTA and FFRct at both per-vessel and per-patient levels.nnnRESULTSn7 articles were included for analysis. The combined diagnostic outcomes from both positive strategy, i.e. a subject was considered as positive only when both CCTA and FFRct were positive, demonstrated relative high specificity (per-vessel: 0.91; per-patient: 0.81), high positive likelihood ratio (LR+, per-vessel: 7.93; per-patient: 4.26), high negative likelihood ratio (LR-, per-vessel: 0.30; per patient: 0.24) and high accuracy (per-vessel: 0.91; per-patient: 0.81) while either positive strategy, i.e. a subject was considered as positive when either CCTA or FFRct was positive, demonstrated relative high sensitivity (per-vessel: 0.97; per-patient: 0.98), low LR+ (per-vessel: 1.50; per-patient: 1.17), low LR- (per-vessel: 0.07; per-patient: 0.09) and low accuracy (per-vessel: 0.57; per-patient: 0.54).nnnCONCLUSIONnBoth positive strategy showed better diagnostic performance to rule in patients with non-significant stenosis compared to either positive strategy, as it efficiently reduces the proportion of testing false positive subjects.

Percutaneous transcatheter aortic valve implantation for degenerated surgical bioprostheses: the first case series in Asia with one-year follow-up.

INTRODUCTIONnPercutaneous transcatheter aortic valve implantation (TAVI) has become an established therapy for inoperable and high-surgical-risk patients with severe aortic stenosis. Although TAVI in patients with degenerated surgical aortic bioprostheses (i.e. valve-in-valve TAVI) is increasingly reported in Western studies, such data is lacking in Asian patients. We describe the initial experience of valve-in-valve TAVI in Asia.nnnMETHODSnEight patients who underwent valve-in-valve TAVI due to degenerated aortic bioprostheses were enrolled. The mechanism of bioprosthetic valve failure was stenotic, regurgitation or mixed. All procedures were performed via transfemoral arterial access, using the self-expanding CoreValve prosthesis or balloon-expandable SAPIEN XT prosthesis.nnnRESULTSnThe mean age of the patients was 71.6 ± 13.2 years and five were male. Mean duration to surgical bioprosthesis degeneration was 10.2 ± 4.1 years. Valve-in-valve TAVI was successfully performed in all patients. CoreValve and SAPIEN XT prostheses were used in six and two patients, respectively. There were no deaths, strokes or permanent pacemaker requirement at 30 days, with one noncardiac mortality at one year. All patients experienced New York Heart Association functional class improvement. Post-procedure mean pressure gradients were 20 ± 11 mmHg and 22 ± 8 mmHg at 30 days and one year, respectively. Residual aortic regurgitation (AR) of more than mild severity occurred in one patient at 30 days. At one year, only one patient had mild residual AR.nnnCONCLUSIONnIn our experience of valve-in-valve TAVI, procedural success was achieved in all patients without adverse events at 30 days. Good clinical and haemodynamic outcomes were sustained at one year.

Is subdural hemorrhage after pulmonary endarterectomy underrecognized

From the Departments of Cardiology and Cardiothoracic Surgery, National Heart Centre Singapore, Singapore; Departments of Anesthesiology, Diagnostic Radiology, Hematology, and Respiratory Medicine, Singapore General Hospital, Singapore; and Department of Cardiothoracic Surgery, Royal Papworth Hospital, Cambridge, United Kingdom. Drs Yap and Ruan contributed equally to this article. Disclosures: Authors have nothing to disclose with regard to commercial support. Received for publication Jan 30, 2018; revisions received May 31, 2018; accepted for publication June 5, 2018; available ahead of print July 26, 2018. Address for reprints: Jonathan Yap, MBBS, MRCP, MPH, National Heart Centre Singapore, 5 Hospital Dr, Singapore 169609 (E-mail: jonyap@yahoo.com). J Thorac Cardiovasc Surg 2018;156:2039-42 0022-5223/

Advanced analyses of computed tomography coronary angiography can help discriminate ischemic lesions

36.00 Copyright 2018 by The American Association for Thoracic Surgery https://doi.org/10.1016/j.jtcvs.2018.06.029 Computed tomography scan of the brain showing an acute hyperintense subdural hemorrhage (red arrow) after pulmonary endarterectomy. T H O R

Improving door-to-balloon times in Asia for acute ST elevation myocardial infarction via direct activation by emergency physicians of percutaneous coronary intervention

BACKGROUNDnComputed tomography coronary angiography (CTCA) image analysis enables plaque characterization and non-invasive fractional flow reserve (FFR) calculation. We analyzed various parameters derived from CTCA images and evaluated their associations with ischemia.nnnMETHODSn49 (61 lesions) patients underwent CTCA and invasive FFR. Lesions with diameter stenosis (DS)u202f≥u202f50% were considered obstructive. CTCA image processing incorporating analytical and numerical methods were used to quantify anatomical parameters of lesion length (LL) and minimum lumen area (MLA); plaque characteristic parameters of plaque volume, low attenuation plaque (LAP) volume, dense calcium volume (DCV), normalized plaque volume (NP Vol), plaque burden, eccentricity index and napkin-ring (NR) sign; and hemodynamic parameters of resistance index, stenosis flow reserve (SFR) and FFRB. Ischemia was defined as FFRu202f≤u202f0.8.nnnRESULTSnPlaque burden and plaque volume were inversely related to FFR. Multivariable logistic regression analysis identified the best anatomical, plaque and hemodynamic predictors, respectively, as DS (≥50% vs <50%; OR: 8.0; 95% CI: 1.6-39.4), normalized plaque volume (NP Vol) (≥4.3 vs <4.3; OR: 3.9; 95% CI: 1.1-14.0) and NR Sign (0 vs 1; OR: 13.6; 95% CI: 1.3-146.1), and FFRB (≤0.8 vs >0.8; OR: 44.4; 95% CI: 8.8-224.8). AUC increased from 0.70 with DS as the sole predictor to 0.81 after adding NP Vol and NR Sign; further addition of FFRB increased AUC to 0.93.nnnCONCLUSIONnNormalized plaque volume, napkin-ring derived from plaque analysis, and FFRB from numerical simulations on CTCA images substantially improved discrimination of ischemic lesions, compared to assessment by DS alone.

Bioresorbable Scaffold Stability and Mechanical Properties

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TCT-54 LEADERS FREE OAC : Biolimus A9 coated versus bare metal stents in patients requiring oral anticoagulation. A pre-specified subgroup analysis of the LEADERS FREE trial

Bioresorbable scaffolds (BRSs), lauded as the fourth revolution in interventional cardiology, were introduced to address the drawbacks of current metallic drug-eluting stents (DESs), including late in-stent restenosis and permanent caging of the vessel. The concept of the BRS is to provide temporal support to the vessel during healing before being degraded and resorbed by the body, allowing vessel vasomotion to be restored. However, although BRSs have many promising advantages over metallic stents, limitations such as insufficient radial strength of the bioresorbable material and large strut profile of the device need to be overcome to enhance their performance. Thick struts affect the deliverability of the device and may cause flow disturbance, which could increase the incidence of acute thrombotic events. This chapter compares the mechanical differences between metallic DESs and BRSs and explores how factors such as crystallinity and processing influence the mechanical properties of BRSs, giving an insight into technologies that can be used to improve BRS radial strength. The bioresorption process, mechanical properties, and clinical outcomes of poly-l-lactide (PLLA)-based and magnesium-based BRSs are examined.