Invasive testing for coronary artery disease: FFR, IVUS, OCT, NIRS

Radiomic features of plaques derived from coronary CT angiography to identify hemodynamically significant coronary stenosis, using invasive FFR as the reference standard

OBJECTIVE

This study aimed to investigate the diagnostic performance of radiomics features derived from coronary computed tomography angiography (CCTA) in the identification of ischemic coronary stenosis plaque using invasive fractional flow reserve (FFR) as the reference standard.

MATERIALS AND METHODS

174 plaques of 149 patients (age: 62.21 ± 8.47 years, 96 males) with at least one lesion stenosis degree between 30 % and 90 % were retrospectively included. Stenosis degree and plaque characteristics were recorded, and a conventional multivariate logistic model was established. Over 1000 radiomics features of the plaque were derived from CCTA images. The plaques were randomly divided into training set (n = 139) and validation set (n = 35). A random forest model was built. The area under the curve (AUC) of the models was compared.

RESULTS

Fifty-eight radiomics features were correlated with functionally significant stenosis (p <  0.05), wherein 56 features had an AUC of >0.6. NCP volume, NRS, remodeling index, and spotty calcification were included in the conventional model. Ultimately, 14 features were integrated to build the radiomics model. The AUC showed an improvement: 0.71 vs 0.82 for the training set and 0.70 vs 0.77 for the validation set (conventional model and radiomics model, respectively); however, it was not statistically significant (p =  0.58).

CONCLUSION

The radiomics analysis of plaques showed improvement compared with conventional plaques assessment in identifying hemodynamically significant coronary stenosis. The statistical advancement of machine learning for plaques to predict hemodynamic stenosis with a noninvasive approach still needs further studies on a large-scale dataset.

The Effect of Functional and Intra-Coronary Imaging Techniques on Fluoroscopy Time, Radiation Dose and Contrast Volume during Coronary Angiography

The aim was to analyze the effect of fractional flow reserve (FFR), intravascular ultrasound (IVUS) and optical coherence tomography (OCT) on fluoroscopy time (FT), radiation dose (RD) and contrast volume (CV) in patients undergoing coronary angiography. This case-control study included consecutive patients above the age of 18, who underwent coronary angiography. FT, RD, and CV after each procedure were retrospectively recorded. Multivariate models were used to demonstrate the effect of these complementary studies and other factors, on radiation and contrast exposure. A total of 1047 patients were included, 74.5% were men and the mean (SD) age was 62.4 (12.1) years. Complementary studies performed were: IVUS (n = 237), FFR (n = 56) and OCT (n = 37). FFR and IVUS had a small effect on FT (η = 0.008 B = 2.2, p < 0.001; η = 0.009, B = 2.5, p < 0.001), while OCT had no effect (η = 0.002 B = 2.9, p < 0.183). IVUS, FFR and OCT had no effect on the RD. IVUS did not affect contrast volume (η = 0.002 B = 9.4, p < 0.163) while OCT and FFR had a small effect on CV (η = 0.006 B = 39, p < 0.01; η = 0.008 B = 37, p < 0.003). The number of placed stents had a significant effect on FT (η = 0.192, Β = 4.2, p < 0.001), RD (η = 0.129, Β = 511.8, p < 0.001) and CV (η = 0.177, Β = 40.5, p < 0.001). The use of complementary studies in hemodynamics did not modify the received RD and had a minor effect on FT and the CV used.

Cardiac Catheterization in Assessment and Treatment of Kawasaki Disease in Children and Adolescents

Cardiac catheterization has become a promising tool to assess and treat coronary artery lesions in patients with Kawasaki disease. Significant coronary artery lesions can now be treated via transcatheter route even in small children. Further development and miniaturization of this technology will help to promote widespread use to the benefit of small children suffering from coronary artery disease. The role of diagnostic and interventional coronary artery procedures in children and adolescents are discussed in this article.

Catheter-based anatomic and functional assessment of coronary arteries in anomalous aortic origin of a coronary artery, myocardial bridges and Kawasaki disease

Most diagnostic testing in patients with anomalous aortic origins of coronary arteries, myocardial bridges, and coronary artery changes after Kawasaki disease are performed with the use of noninvasive techniques. In some cases, however, further diagnostic information is needed to guide the clinician in treating these patients. In such instances, cardiac catheterization with invasive anatomic and functional testing is an invaluable tool. Moreover, interventional treatment in the cardiac catheterization laboratory may be performed in a small subset of these patients. As the diagnosis of these conditions is now becoming more common, it is important for pediatric interventional cardiologists to be familiar with these techniques. In this article, the role of angiography, intravascular ultrasound, fractional flow reserve, and optical coherence tomography in these patients is reviewed.

Anomalous Coronary Arteries and Myocardial Bridges: Risk Stratification in Children Using Novel Cardiac Catheterization Techniques

The evaluation of the vast majority of children with anomalous aortic origin of a coronary artery (AAOCA) and/or myocardial bridges is performed with non-invasive testing. However, a subset of these patients may benefit from invasive testing for risk stratification. All patients included in the Coronary Anomalies Program (CAP) at Texas Children's Hospital who underwent cardiac catheterization were included. Techniques included selective coronary angiograms (SCA), intravascular ultrasound (IVUS), and fractional flow reserve (FFR) measurements with provocative testing using adenosine and/or dobutamine infusions. Out of the 131 patients followed by the CAP between 12/12-4/16, 8 (6%) patients underwent 9 cath investigations at median age 13.1 (2.6-18.7) years and median weight 49.5 (11.4-142.7) kg. Six patients presented with cardiac signs/symptoms. Four patients had myocardial bridges of the left anterior descending (LAD) coronary artery, 2 patients had isolated AAOCA, and 2 patients had an anomalous left coronary artery (LCA) with an intramyocardial course of the LAD. SCA was performed in all patients. FFR was positive in 4/6 patients: IVUS showed >70% intraluminal narrowing in 3/5 patients. One patient had hemodynamic instability that reversed with catheter removal from the coronary ostium. Based on the catheterization data obtained, findings were reassuring in three patients, surgery was performed in three patients, and two patients are being medically managed/restricted from competitive sports. In our small cohort of patients, we demonstrated that IVUS and FFR can safely be performed in children and may help to risk stratify some patients with AAOCA and myocardial bridges.

Intracoronary Imaging in the Detection of Vulnerable Plaques

Coronary artery disease is the result of atherosclerotic changes to the coronary arterial wall, comprising endothelial dysfunction, vascular inflammation and deposition of lipid-rich macrophage foam cells. Certain high-risk atherosclerotic plaques are vulnerable to disruption, leading to rupture, thrombosis and the clinical sequelae of acute coronary syndrome. Though recognised as the gold standard for evaluating the presence, distribution and severity of atherosclerotic lesions, invasive coronary angiography is incapable of identifying non-stenotic, vulnerable plaques that are responsible for adverse cardiovascular events. The recognition of such limitations has impelled the development of intracoronary imaging technologies, including intravascular ultrasound, optical coherence tomography and near-infrared spectroscopy, which enable the detailed evaluation of the coronary wall and atherosclerotic plaques in clinical practice. This review discusses the present status of invasive imaging technologies; summarises up-to-date, evidence-based clinical guidelines; and addresses questions that remain unanswered with regard to the future of intracoronary plaque imaging.

Vascular Stenosis Asymmetry Influences Considerably Pressure Gradient and Flow Volume

Vascular stenosis is often described only by its percentage in both clinical and scientific praxis. Previous studies gave inconclusive results regarding the effect of stenosis eccentricity on its hemodynamic effect. The aim of this experimental study was to investigate and quantify the effect of stenosis severity and eccentricity on the pressure drop. A combination of pressure and flow measurements by Particle Imaging Velocimetry (PIV) method was used. Models of the same stenosis significance but with different levels of eccentricity were studied in vitro by PIV. This study has shown that stenosis asymmetry is associated with more profound pressure drop and flow volume decrease. On the contrary, pressure drop and flow volume decrease were not further significantly influenced by the level of asymmetry. Hemodynamic changes associated with stenosis eccentricity must be taken into account in both clinical and scientific studies.

Intravascular ultrasound observation of the mechanism of no-reflow phenomenon in acute myocardial infarction

Objective

To study the mechanism of the no-reflow phenomenon using coronary angiography (CAG) and intravascular ultrasound (IVUS).

Methods

A total of 120 patients with acute myocardial infarction (AMI) who successfully underwent indwelling intracoronary stent placement by percutaneous coronary intervention (PCI). All patients underwent pre- and post-PCI CAG and pre-IVUS. No-reflow was defined as post-PCI thrombolysis in myocardial infarction (TIMI) grade 0, 1, or 2 flow in the absence of mechanical obstruction. Normal reflow was defined as TIMI grade 3 flow. The pre-operation reference vascular area, minimal luminal cross-sectional area, plaque cross-sectional area, lesion length, plaque volume and plaque traits were measured by IVUS.

Results

The no-reflow group was observed in 14 cases (11.6%) and normal blood-flow group in 106 cases (89.4%) based on CAG results. There was no statistically significant difference in the patients’ medical history, reference vascular area (no-flow vs. normal-flow; 15.5 ± 3.2 vs. 16.2 ± 3.3, p> 0.05) and lesion length (21.9 ± 5.1 vs. 19.5 ± 4.8, p> 0.05) between the two groups. No-reflow patients had a longer symptom onset to reperfusion time compared to normal blood-flow group [(6.6 ± 3.1) h vs (4.3 ± 2.7) h; p< 0.05] and higher incidence of TIMI flow grade< 3 (71.4% vs 49.0%, p< 0.05). By IVUS examination, the no-reflow group had a significantly increased coronary plaque area and plaque volume compared to normal blood-flow group [(13.7 ± 3.0) mm² vs (10.2 ± 2.9) mm²; (285.4 ± 99.8) mm³ vs (189.7 ± 86.4) mm³; p< 0.01]. The presence of IVUS-detected soft plaque (57.1% vs. 24.0%, p< 0.01), eccentric plaque (64.2% vs. 33.7%, p< 0.05), plaque rupture (50.0% vs. 21.2%, p< 0.01), and thrombosis (42.8% vs. 15.3%) were significantly more common in no-reflow group.

Conclusion

There was no obvious relationship between the coronary risk factors and no-reflow phenomenon. The symptom onset to reperfusion time, TIMI flow grade before stent deployment, plaque area, soft plaques, eccentric plaques, plaque rupture and thrombosis may be risk factors for the no-reflow phenomenon after PCI.