Coronary artery stenosis and vulnerable plaque quantification on CCTA by deep learning methods

Introduction

Coronary computed tomography angiography (CCTA) has emerged as a reliable non-invasive modality to assess coronary artery stenosis (CAS) severity and vulnerable plaque (VP). However, comprehensive CCTA assessment, especially VP, is time-consuming and dependent on reader expertise, limiting CCTA's true potential.

Purpose

In this study, we aim to develop and validate a deep learning (DL) based system capable of evaluating CAS severity and characterising VP on CCTA.

Methods

A DL system was trained to assess CAS severity on 3909 expert annotated vessels. A subset of 824 vessels was used to train the model to assess for the presence of VP. The model was based on a 2D U-Net and 3D convolutional neural network architecture. The system automatically performed vessel tracking and segmentation to quantify stenosis severity and characterise the presence of VP. CAS severity was categorised as 0%, 1–49% and ≥50%. VP was defined as: low attenuation plaque (LAP; ≤30 Hounsfield units), positive remodelling (PR; ≥10% diameter) and spotty calcification (SC; <3mm). The model was then tested on 1435 vessels for CAS (mean calcium score 197±502) and a subset of 365 vessels for VP (mean calcium score 419±551), and its diagnostic performance compared with expert readers.

Results

The CAS testing data had a prevalence of 75% (1080/1435), 18% (257/1435) and 6.8% (98/1435) for 0%, 1–49% and ≥50% stenosis, respectively. VP was present in 20% (72/365) in the respective dataset with 44% (32/72) LAP, 19% (14/72) PR and 36% (26/72) SC. Average analysis time for CAS severity and VP was 3.7±2.0s and 3.5±1.8s, respectively. Diagnostic performance of our system is summarised in Tables 1 (CAS severity) and 2 (VP characteristics).

Conclusions

We developed an DL based system capable of rapidly evaluating CAS severity and characterising VP on CCTA. Our system demonstrated high specificity and accuracy for both CAS severity and VP quantification when compared with expert readers.

Funding Acknowledgement

Type of funding sources: None.

The role of intravascular ultrasound to guide drug-eluting stents implantation

Serial IVUS has demonstrated significant differences in intimal hyperplasia (IH) volume between drug-eluting stent (DES) and bare metal stents (BMS) in recent clinical trials. It has also been reported that IVUS is a useful tool in determining optimal DES implantation, especially for diabetes mellitus (DM) patients. Recent data have also suggested a critical role for, IVUS guidance in reduction of risk for DES thrombosis. IVUS has been invaluable in the elucidation of DES effects on the arterial wall, offering insight into the potential mechanisms of DES failure. Therefore, in this current manuscript, we review the potential benefits of intravascular ultrasound (IVUS) during drug eluting stent (DES) implantation.

Review of percutaneous therapy for bifurcation lesions in the era of drug-eluting stents

Although recent advances in percutaneous coronary interventions (PCI) have led to dramatic expansions in procedural complexity, bifurcation lesions (BL) remain a serious challenge for the interventionalist. Turbulent flow dynamics and high shear stress likely predispose coronary bifurcations to development of atherosclerotic plaques. These lesions comprise 15% to 20% of the total number of coronary interventions. When compared with non-BL interventions, BL interventions demonstrate lower procedural success rates, higher procedural costs, longer hospitalizations, and higher clinical and angiographic restenosis rates. The recent introduction of drug-eluting stents (DES) has resulted in lower incidences of target lesion/ vessel revascularization and reduction of main branch restenosis in this anatomic subset, when compared to historical bare metal stent (BMS) controls. Nonetheless, DES have not resolved the bifurcation PCI problem; and several techniques employing either 1 or 2 stents have emerged. Stenting of the main vessel with provisional side branch stenting seems to be the prevailing approach. While no definitive single BL-PCI technique has been identified, the optimal approach is likely lesion-specific. This paper reviews different treatment modalities for this complex lesion subset, with particular emphasis on the use of DES, as well as new potential therapeutic approaches.

The use of electron beam computed tomography in the primary care setting

EBT has become a clinical tool that has allows physicians to gain another piece of data to help predict which patients may be at risk for coronary artery disease. Valuable information that predicts a patient's risk at a relatively young age (fourth or fifth decade) may allow attenuation of such risk by aggressive risk factor modification over the ensuing decades. Coronary calcium can be quantified and subsequently followed to see if risk factor modification is effective. The task for the primary care physician is to properly use these new imaging tests to improve the care they provide for their patients.

Therapeutic angiogenesis with recombinant fibroblast growth factor-2 improves stress and rest myocardial perfusion abnormalities in patients with severe symptomatic chronic coronary artery disease

BACKGROUND

We report the effects of the administration of recombinant fibroblast growth factor-2 (rFGF-2) protein on myocardial perfusion using single photon emission computed tomography imaging in humans with advanced coronary disease.

METHODS AND RESULTS

A total of 59 patients with coronary disease that was not amenable to mechanical revascularization underwent intracoronary (n=45) or intravenous (n=14) administration of rFGF-2 in ascending doses. Changes in perfusion were evaluated at baseline and again at 29, 57, and 180 days after rFGF-2 administration. In this uncontrolled study, perfusion scans were analyzed by 2 observers who were blinded to patient identity and test sequence; scans were displayed in random order, with scans from nonstudy patients randomly interspersed to enhance blinding. Combining all dose groups, a reduction occurred in the per-segment reversibility score (reflecting the magnitude of inducible ischemia) from 1.7+/-0.4 at baseline to 1.1+/-0.6 at day 29 (P:<0.001), 1.2+/-0.7 at day 57 (P:<0.001), and 1.1+/-0.7 at day 180 (P:<0.001). The 37 patients with evidence of resting hypoperfusion had evidence of improved resting perfusion: their per-segment rest perfusion score of 1.5+/-0. 5 at baseline decreased to 1.0+/-0.8 at day 29 (P:<0.001), 1.0+/-0.8 at day 57 (P:=0.003), and 1.1+/-0.9 at day 180 (P:=0.11).

CONCLUSIONS

These preliminary data suggest that the administration of rFGF-2 to patients with advanced coronary disease resulted in an attenuation of stress-induced ischemia and an improvement in resting myocardial perfusion; these findings are consistent with a favorable effect of therapeutic angiogenesis.

Irradiation and postangioplasty restenosis: a recent overview

One of the most intriguing developments in recent years towards prevention of restenosis after angioplasty is the use of ionizing radiation. The background for the use of radiation treatment for this application is sound, since radiation is used not only to treat malignant cancerous growths but also is used for treatment of benign hyperplastic disorders such as post-surgical keloid formation and recurrence of pterygium after surgical removal. Restenosis can be considered a form of overexuberant wound healing triggered by angioplasty. Ionizing radiation inhibits serum-stimulated proliferation of many cell types including fibroblasts and smooth muscle cells in vitro and also suppresses the synthesis of collagen by cultured fibroblasts. Liermann who showed inhibition of post-stent restenosis first used ionizing radiation for restenosis prevention clinically in iliac and iliofemoral arteries. Subsequently, extensive animal studies in various restenosis models have shown a profound inhibitory effect of catheter-based radiation (endovascular brachytherapy) on neointima formation and overall vessel shrinkage (negative remodeling). Based on these results clinical trials have been initiated with several types of devices and isotopes. Among these are 192Ir, 32P, 90Y, 90Sr/Y and 188Re. Additionally, radioactive stents have been developed; devices for clinical use are made radioactive at the microCi level by surface implantation of 32P ions. Results from early clinical trials are encouraging and brachytherapy appears safe for clinical use and at an appropriate dose, may be highly effective for restenosis prevention.

GPIIbIIIa inhibitors as adjunctive therapy in acute myocardial infarction

Thrombolytic therapy has proved useful in the treatment of acute myocardial infarction but is frequently associated with limited vessel reperfusion and early reocclusion. Local platelet aggregation and activation play a role in these pathological processes, explaining the benefit of aspirin, a weak antiplatelet agent. Recent interest has turned to GPIIbIIIa antagonists, a class of potent inhibitors of platelet aggregation. Their concomitant use with fibrinolytics, in rescue and primary angioplasty for acute myocardial infarction treatment is explored. Efficacy and safety issues are addressed and the potential pivotal role of these agents in the treatment of acute myocardial infarction is discussed.

Increased platelet responsiveness following coronary stenting. Heparin as a possible aetiological factor in stent thrombosis

AIMS

Platelet activation may be a determinant of thrombotic and restenotic complications following intracoronary stenting. In order to measure the effect of stenting on platelet activation antigen expression we used whole blood flow cytometry in 18 patients undergoing Palmaz-Schatz stenting (treated with full anticoagulation) and compared these with a group of 18 patients undergoing elective angioplasty. The effects of low molecular weight heparin and unfractionated heparin on platelet behaviour were also studied, both in vitro and in vivo to determine the contribution of prolonged heparin therapy to platelet activation following stenting.

METHODS AND RESULTS

Fibrinogen binding to activated GPIIb-IIIa, and surface expression of P-selectin, GPIb and GPIIb-IIIa antigens were measured in unstimulated peripheral blood samples (rest) and on stimulation with adenosine diphosphate (0.1-10 micromol x 1(-1)) and thrombin (0.02-0.16 U x ml(-1)). No changes were seen in resting samples following angioplasty or stenting. Agonist responsiveness was unaltered after angioplasty, but in stented patients antigen expression in response to thrombin was significantly reduced (P< or =0.04), whilst the adenosine diphosphate response was significantly increased (P=0.01). Similar effects were observed in patients with unstable angina treated with either low molecular weight heparin or unfractionated heparin in vivo. In vitro, both unfractionated and low molecular weight heparin inhibited thrombin-induced platelet activation, but stimulation of adenosine diphosphate responses was more marked with unfractionated than low molecular weight heparin.

CONCLUSIONS

There was a significant increase in platelet responsiveness to adenosine diphosphate following intracoronary stenting in patients treated with conventional anticoagulants. This was probably a consequence of treatment with heparin. Activation of platelets by heparin may explain the increased rate of stent thrombosis in patients treated with anticoagulant therapy. Low molecular weight heparins stimulate platelets less than unfractionated heparin.

Use of abciximab in interventional cardiology

The advent of platelet membrane glycoprotein (GP) IIb/IIIa inhibitors has changed the landscape of interventional cardiology. Given the commercial availability of abciximab and expected regulatory approvals for other receptor blockers, defining appropriate use of these agents in the interventional setting is mandated. One key issue is selection of patients who may benefit from GP IIb/IIIa receptor blockade. Focusing specifically on abciximab, data from three large-scale, randomized trials demonstrate that abciximab is appropriate for all patients undergoing percutaneous transluminal coronary angioplasty, regardless of risk stratum. Other important issues to consider when prescribing this therapy include benefits in conjunction with stents and new devices, dosing and timing of administration, and the role of prophylactic versus "bailout" administration. This article reflects a distillation of the views and consensus regarding the use of GP IIb/IIIa inhibitors in patients undergoing coronary intervention expressed by a group of international experts convened in Davos, Switzerland, February 16, 1997. This report attempts to review clinical progress to date, formulate recommendations, and map out potentially fruitful lines of inquiry for future investigation.

Use of abciximab in interventional cardiology

The advent of platelet membrane glycoprotein (GP) IIb/IIIa inhibitors has changed the landscape of interventional cardiology. Given the commercial availability of abciximab and expected regulatory approvals for other receptor blockers, defining appropriate use of these agents in the interventional setting is mandated. One key issue is selection of patients who may benefit from GP IIb/IIIa receptor blockade. Focusing specifically on abciximab, data from three large-scale, randomized trials demonstrate that abciximab is appropriate for all patients undergoing percutaneous transluminal coronary angioplasty, regardless of risk stratum. Other important issues to consider when prescribing this therapy include benefits in conjunction with stents and new devices, dosing and timing of administration, and the role of prophylactic versus "bailout" administration. This article reflects a distillation of the views and consensus regarding the use of GP IIb/IIIa inhibitors in patients undergoing coronary intervention expressed by a group of international experts convened in Davos, Switzerland, February 16, 1997. This report attempts to review clinical progress to date, formulate recommendations, and map out potentially fruitful lines of inquiry for future investigation.

[Endovascular radiation and restinosis]

Restenosis following coronary angioplasty is still the most vexing problem facing percutaneous coronary interventions, despite advances in stent designs and new antiplatelet therapies. Endovascular radiation has shown to limit the formation of neointimal tissue in the vascular wall in recent studies and it appears as a promising method to control the restenotic process. This article reviews the experimental and clinical data with the use of this form of radiation and analyses its potential role in Interventional Cardiology.

In vitro comparison of the effects of contrast media on coagulation and platelet activation

The aim of this study was to compare the in vitro effects of different classes of contrast media on both the blood coagulation system and on platelet function. Global tests (APTT, TT) and FpA and F1 + 2 generation measurements showed that ioxaglate (ionic dimer) presents the highest anticoagulant potential. The anticoagulant effects of nonionic agents were less marked, iodixanol (nonionic dimer) being significantly less anticoagulant than iohexol (nonionic monomer). Major platelet activation was observed with release of PF4, serotonin and PDGF-AB when iohexol was incubated for 1 min in whole blood. Iodixanol showed no effect over the same period, while moderate platelet activation was observed after 30 min. Under the same experimental conditions, ioxaglate had no effect on platelets even after incubation for 30 min, whereas activation was observed with 9 g/l saline control at this time. Prevention of thrombin formation and platelet activation is only achieved with ioxaglate, the ionic dimer. These findings may be clinically important in the thrombotic environment of radiological procedures and may explain the increased thrombotic risks observed with nonionic agents in interventional procedures.

Electro-encapsulating drugs within blood platelets: local delivery to injured arteries during angioplasty

Prostacyclins (PGl2) inhibit platelet-platelet interactions at concentrations that do not affect platelet adhesion to collagen and other arterial subendothelial structures exposed during injury. Such compounds can be encapsulated within platelets by reversible electroporation and, using the platelet's natural haemostatic propensity, they can be targeted to injured vessels in vivo. In rat (aorta), rabbit (ileofemoral) and pig (carotid) angioplasty models, autologous platelets, electro-loaded with the stable prostacyclin iloprost and given intravenously after balloon overstretch injury, substantially reduced platelet deposition at the lesion site as compared with control platelets. In the pig model, when the drug-loaded platelets were delivered directly to the injury site during angioplasty via a double balloon delivery catheter, platelet deposition was restricted to monolayer coverage (> 80% reduction compared with controls). Candidate antiproliferative drugs (for co-encapsulating with iloprost) are being investigated in order to develop a combined antithrombotic/antirestenosis strategy for use during angioplasty and thrombolysis procedures. Autologous platelets as drug-targeting vehicles should obviate many of the immunological, toxicological and biodegradability concerns inherent in the use of other drug transport vectors such as antibodies, viruses, liposomes and synthetic polymer microcapsules.

Evaluation of whole blood flow cytometric detection of platelet bound fibrinogen on normal subjects and patients with activated platelets

Activated platelets can be detected by measuring platelet-bound fibrinogen in a whole blood, flow cytometric assay, using a fluorescently-conjugated polyclonal antibody. Fibrinogen binding to unstimulated platelets from normal subjects was low in this assay, as was expression of the CD63 antigen. Single cell counting of samples prepared for flow cytometric analysis showed platelet aggregates do not form during the assay procedure. Immune complexes were not seen, and fibrinogen binding to the platelets was unaffected by the CD32 MAb, IV.3. Artefactual activation of the unfixed samples could be minimised by control of phlebotomy, time and temperature of incubation. Variations in platelet count in the range 140-430 x 10(9) 1(-1) and in plasma fibrinogen in the range 2-6 g 1(-1) did not affect the assay results. Comparison of fibrinogen binding with expression of CD63 antigen on normal platelets, stimulated with agonists in vitro, demonstrated that fibrinogen binding detects an earlier stage of platelet activation. Platelet bound fibrinogen was shown to be sensitive in detecting small numbers of activated platelets in clinical samples in twelve patients on intensive care, four undergoing haemofiltration. The patients had a significantly higher median percentage of circulating platelets with bound fibrinogen (p < 0.005), but fibrinogen binding was significantly lower (p < 0.02) in response to 10(-5) M ADP, compared to twelve age-matched normal controls.

Implantation of half Palmaz-Schatz stents in short aorto-ostial lesions of saphenous vein grafts

Two cases are presented in which a half Palmaz-Schatz stent was implanted in a short lesion located in the ostium of a saphenous vein graft. Aorto-ostial stenoses are a technical challenge for balloon angioplasty and stenting. Short stents may offer several advantages as regards deployment, positioning, thrombogenicity, and restenosis.

Thyrotoxicosis presenting as a life threatening hypokalaemic paralysis: investigation of the Na/K pump in isolated leucocytes

A 37-year-old Chinese man presented with the rapid onset of profound muscle weakness, and a serum potassium of 1.7 mmol/l. The intravenous infusion of undiluted potassium chloride (2 mmol/ml) through a central venous catheter resulted in rapid recovery. Further investigation revealed thyrotoxicosis. He was treated with carbimazole and subsequently remained well. We assessed Na/K pump activity in isolated leucocytes taken from the patient and found an exaggerated response to adrenaline which ceased after he became euthyroid.

A case of resistant tuberculosis

We report a case of multiple drug-resistant pulmonary tuberculosis, in which treatment with two second line chemotherapy regimens was inadequate. Despite in-vitro sensitivity to ciprofloxacin the patient remained sputum positive with Mycobacterium tuberculosis after 11 months.

Pancreatic pseudocyst causing portal vein thrombosis and pancreatico-pleural fistula

Portal vein thrombosis and pancreatico-pleural fistula are unusual complications of chronic pancreatitis. We describe a patient with chronic alcoholic pancreatitis in whom erosion of the splenic vein led to portal vein thrombosis and to the development of a pancreatico-pleural fistula. We suggest that fistula formation may occur over a considerable time period as the portal vein thrombosis was diagnosed three years before the amylase-rich pleural effusions.

Effect of hyperoxia and hypoxia on exercise-induced breathlessness in normal subjects

1. The subjective changes accompanying alterations in inspired oxygen concentration during heavy exercise have been investigated single blind, in normal subjects. 2. In particular, the intensity of the sensation of breathlessness was quantified using a visual analogue scale and changes were compared with those in objective ventilatory measures. 3. Eleven subjects performed three steady-state work-load exercise tests on different days and 100% O2, 15% O2 or air were randomly administered for a fixed interval during each test. 4. Compared with air breathing, all subjects felt less breathless during 100% O2 breathing, and ten of them felt more breathless when inspiring 15% O2; these changes were reversed on return to air breathing. 5. During and after 100% O2, the time course of changes in breathlessness was similar to those for ear arterial oxygen saturation and minute ventilation such that it could be a secondary response to either. However, during and after inspiration of 15% O2, changes in breathlessness occurred relatively more quickly than those in ventilation, more closely reflecting changes in oxygen saturation; this suggests that hypoxia, per se, could contribute to the genesis of this sensation. 6. Individual variability in breathlessness responses to exercise and changes in inspired oxygen concentration did not correlate with objective ventilatory changes; neither were changes in breathlessness in the group particularly associated with changes in respiratory frequency or tidal volume.

The measurement of breathlessness induced in normal subjects: individual differences

Normal subjects show wide variability in their sensory scaling of breathlessness for equivalent degrees of ventilatory stimulation and behave "characteristically' irrespective of stimulus type. Observed differences are not explained by physical characteristics, ventilatory sensitivity or pattern of breathing although there is a weak association with the degree of physical fitness. Differences are seen when scaling is performed with reference to both rigidly defined extremes of breathlessness (visual analogue scaling) and a subject's own relative changes in the intensity of this sensation (magnitude estimation). These findings may explain the common observation, in patients with respiratory disease, of dyspnoea out of proportion to the pathophysiological state.

The measurement of breathlessness induced in normal subjects: validity of two scaling techniques

The intensity of breathlessness induced by ventilatory stimulation resulting from hypercapnia, hypoxia or exercise has been quantified in normals by using the two different sensory scaling techniques of linear visual analogue scaling and ratio magnitude estimation. In naive individuals both techniques show good face validity. When related to ventilation, quantification of breathlessness is moderately reproducible with both methods, even when subjects are kept in ignorance of the pattern of ventilatory stimulation. There is a small within- and large between-subject variability with both scaling techniques; possible factors responsible are discussed. The reproducibility of visual analogue scaling when related to ventilation is independent of the nature of the ventilatory stimulus and is maintained over intervals as long as 1 week when memory for the score given is unlikely to be an important factor. The difficulties of interpreting subjective estimates of perceived breathlessness are discussed, together with the relative merits of the two scaling techniques.