In vivo comparison of lumen dimensions measured by time domain-, and frequency domain-optical coherence tomography, and intravascular ultrasound

Lumen dimensions measured by time-domain optical coherence tomography (TD-OCT) may be influenced by the hemodynamic effect of proximal balloon occlusion. Frequency-domain OCT (FD-OCT) does not require the interruption of blood flow. Therefore, we compared the coronary lumen dimensions measured by TD-OCT, FD-OCT, and intravascular ultrasound (IVUS) in both stented and non-stented segments. Twenty patients who underwent both IVUS and OCT imaging (10 for TD- and 10 for FD-OCT) after stent implantation were included. The maximum, minimum, and mean diameters and areas were measured at the proximal and distal stent edges, as well as 3 mm inside and 5 mm outside of both edges. The measurements inside stent showed no significant differences between IVUS and TD- or FD-OCT. The lumen mean diameters and areas measured by IVUS at 5 mm outside stent were similar to those measured by FD-OCT (Distal; 3.07 ± 0.7 vs 3.03 ± 0.7 mm, p = 0.08 and 7.80 ± 4.0 vs 7.72 ± 4.1 mm², p = 0.07, respectively. Proximal; 3.25 ± 0.7 vs 3.23 ± 0.7 mm, p = 0.09 and 8.78 ± 3.8 vs 8.65 ± 3.7 mm², p = 0.08, respectively), but were greater than those measured by TD-OCT (Distal; 2.75 ± 0.5 vs 2.29 ± 0.5 mm, p = 0.0001 and 6.15 ± 2.6 vs 4.38 ± 1.9 mm², p = 0.0002, respectively. Proximal; 3.27 ± 0.6 vs 2.69 ± 0.6 mm, p = 0.0001 and 8.64 ± 3.4 vs 6.12 ± 2.7 mm², p = 0.0001 respectively). The interaction between TD- and FD-OCT for lumen dimension measurements at 5 mm outside stent was statistically significant. Vessel dimension measurements were similar between IVUS and FD-OCT in native vessel unlike with TD-OCT. Therefore, we might adapt the IVUS criteria of lesion severity for percutaneous coronary intervention to FD-OCT.     

In vivo volumetric analysis of coronary stent using optical coherence tomography with a novel balloon occlusion-flushing catheter: a comparison with intravascular ultrasound

Optical coherence tomography (OCT) is limited as an intravascular imaging tool because of interference with blood. This study tested a new balloon occlusion-flushing catheter for OCT scanning of stented coronary arteries and compared stent measurements between OCT and intravascular ultrasound (IVUS). Motorized pullback with OCT and IVUS was examined in coronary stents deployed in swine. Quantitative measurements were obtained and compared between both groups. In addition, stent strut thickness was compared among OCT, IVUS and actual measurement. The occlusion catheter successfully provided motorized pullback OCT images in the stented coronary arteries without any complications. There were no differences in calculated lumen volume. However, stent volumes were significantly smaller with OCT than with IVUS (p < 0.05). OCT significantly underestimated the stent strut thickness compared with the actual measurement. Although OCT underestimates the stent strut thickness, motorized pullback OCT imaging with the occlusion catheter can provide appropriate in-stent images in the porcine coronary arteries.     

Serial changes of minimal stent malapposition not detected by intravascular ultrasound: follow-up optical coherence tomography study

Morphologic changes of small-sized post-stent malapposition have not been sufficiently evaluated. We investigated serial changes of minimal post-stent malapposition with a follow-up optical coherence tomography (OCT) study. Post-stent OCT and intravascular ultrasound (IVUS) and follow-up OCT were performed in 26 patients with minimal post-stent malapposition. Serial changes of number and percent of malapposition struts, and mean extra-stent malapposition area were measured in OCT analysis. Zotarolimus-eluting stent (ZES), sirolimus-eluting stent (SES), and paclitaxel-eluting stent (PES) were deployed in 17, 7 and 2 patients, respectively. Mean durations of the follow-up OCT study were 5.7 ± 3.0 months. The minimal post-stent malapposition cannot be detected by the IVUS, but be visualized with an OCT examination. According to different drug-eluting stents, malapposed stent struts were defined as the struts with detachment from the vessel wall ≥160 μm for SES, ≥130 μm for PES, and ≥110 μm for ZES. The percent of malapposition struts significantly decreased from 12.2 ± 11.0% post-stent to 1.0 ± 2.2% follow-up (P < 0.001). There was a significant decrease in the mean extra-stent malapposition area from 0.35 ± 0.16 mm² post-stent to 0.04 ± 0.11 mm² follow-up (P < 0.001). Complete disappearance of stent malapposition was also observed in 22 (85%) patients. In conclusion, minimal stent malapposition which is not detectable by IVUS may disappear or decrease in follow-up OCT evaluation.     

Accuracy of coronary computed tomography angiography for bioresorbable scaffold luminal investigation: a comparison with optical coherence tomography

To establish the accuracy of coronary computed tomography angiography (CTA) for in-scaffold quantitative evaluation with optical coherence tomography (OCT) as a reference. The translucent backbone of the bioresorbable scaffold allow us to evaluate non-invasively the coronary lumen with coronary CTA. In the ABSORB first-in-man studies, coronary CTA was shown to be feasible for quantitative luminal assessment. Nevertheless, a comparison with an intravascular modality with higher resolution has never been performed. In the ABSORB Cohort B trial, 101 patient with non-complex lesions were treated with the fully biodegradable vascular scaffold. For this analysis, all patients who underwent coronary CTA at 18 months and OCT within ±180 days were included. Coronary CTA and OCT data were analysed at an independent core laboratory for quantitative cross-sectional luminal dimensions. The primary objective was the accuracy and precision of coronary CTA for in-scaffold minimal lumen area assessment, with OCT as a reference. Among the 101 patients of the ABSORB Cohort B trial, 35 underwent both OCT and coronary CTA. The feasibility of quantitative evaluation was 74%. In the scaffolded segment, coronary CTA underestimated minimal lumen area by 9.8% (accuracy 0.39 mm², precision 1.0 mm², 95% limits of agreement ?1.71 to 2.50 mm²). A similar level of agreement was observed in the non-scaffolded segment. Compared to OCT, coronary CTA appears to be accurate for the estimation of in-scaffold luminal areas, with no difference compared to the non-scaffolded region.     

Comparison of longitudinal geometric measurement in human coronary arteries between frequency-domain optical coherence tomography and intravascular ultrasound

Previous studies have demonstrated the higher accuracy of frequency-domain optical coherence tomography (FD-OCT) for quantitative measurements in comparison with intravascular ultrasound (IVUS). However, those analyses were based on the cross-sectional images. The aim of this study was to assess the accuracy of FD-OCT for longitudinal geometric measurements of coronary arteries in comparison with IVUS. Between October 2011 and March 2012, we performed prospective FD-OCT and IVUS examinations in consecutive 77 patients who underwent percutaneous coronary intervention with single stent. Regression analysis and Bland–Altman analysis revealed an excellent correlation between the FD-OCT-measured stent lengths and IVUS-measured stent lengths (r = 0.986, p < 0.001; mean difference = ?0.51 mm). There was an excellent agreement between the actual stent lengths and the FD-OCT-measured stent lengths (r = 0.993, p < 0.001) as well as between the actual stent lengths and the IVUS-measured stent lengths (r = 0.981, p < 0.001). The difference between the actual stent lengths and the FD-OCT-measured stent lengths was significantly smaller than that between the actual stent lengths and the IVUS-measured stent lengths (0.15 ± 0.68 vs. 0.70 ± 1.15 mm, p < 0.001). Both FD-OCT (mean difference = ?0.04 and ?0.04 mm, respectively) and IVUS (mean difference = ?0.06 and ?0.06 mm, respectively) showed an excellent intra-observer and inter-observer reproducibility for the stent length measurements. In conclusion, FD-OCT provides accurate longitudinal measurement with excellent intra-observer and inter-observer reproducibility. FD-OCT might be a reliable technique for longitudinal geometric measurement in human coronary arteries.     

Optical coherence tomography criteria for defining functional severity of intermediate lesions: a comparative study with FFR

Fractional flow reserve (FFR) is the gold standard in the assessment of severity of the coronary stenosis. The aim of the study was to compare optical coherence tomography (OCT) obtained intermediate coronary lesions lumen areas measurements with FFR assessments, with the goal to develop an OCT threshold to identify significant coronary stenosis. 48 patients (mean age 65 ± 10 years) was enrolled for the study. Within this population, 71 intermediate coronary lesions were investigated using both FFR and OCT. High dose bolus of Adenosine (120 μg) was used to obtain coronary hyperemia. OCT imaging was performed using non-occlusive technique to assess minimal lumen area (MLA) and diameter. The OCT cut-off value that showed the best correlation with the FFR cut-off of 0.80 was the MLA less than 2.05 mm² (accuracy 87 %, sensitivity 75 %, specificity 90 %, p < 0.001). The study did not disclose any relationship between FFR value and the lesion length. Vessel size influenced the OCT cut-off values, with greater values being found in presence of arteries with a reference diameter greater than 3.0 mm. OCT derived minimal lumen area might be complementary to FFR measurement in identifying ischemia related lesions. Further studies are warranted to assess threshold values in relation to vessel size and location.     

The impact of Fourier-Domain optical coherence tomography catheter induced motion artefacts on quantitative measurements of a PLLA-based bioresorbable scaffold

Intracoronary Fourier-Domain optical coherence tomography (FD-OCT) enables imaging of the coronary artery within 2–4 seconds, a so far unparalleled speed. Despite such fast data acquisition, cardiac and respiratory motion can cause artefacts due to longitudinal displacement of the catheter within the artery. We studied the influence of longitudinal FD-OCT catheter displacement on serial global lumen and scaffold area measurements in coronary arteries of swine that received PLLA-based bioresorbable scaffolds. In 10 swine, 20 scaffolds (18 × 3.0 mm) were randomly implanted in two epicardial coronary arteries. Serial FD-OCT imaging was performed immediately after implantation (T1) and at 3 (T2) and 6 months (T3) follow-up. Two methods for the selection of OCT cross-sections were compared. Method A did not take into account longitudinal displacement of the FD-OCT catheter. Method B accounted for longitudinal displacement of the FD-OCT catheter. Fifty-one OCT pullbacks of 17 scaffolds were serially analyzed. The measured scaffold length differed between time points, up to one fourth of the total scaffold length, indicating the presence of longitudinal catheter displacement. Between method A and B, low error was demonstrated for mean area measurements. Correlations between measurements were high: R² ranged from 0.91 to 0.99 for all mean area measurements at all time points. Considerable longitudinal displacement of the FD-OCT catheter was observed, diminishing the number of truly anatomically matching cross-sections in serial investigations. Global OCT dimensions such as mean lumen and scaffold area were not significantly affected by this displacement. Accurate co-registration of cross-sections, however, is mandatory when specific regions, e.g. jailed side branch ostia, are analyzed.     

Quantitative multi-modality imaging analysis of a fully bioresorbable stent: a head-to-head comparison between QCA,IVUS and OCT

The bioresorbable vascular stent (BVS) is totally translucent and radiolucent, leading to challenges when using conventional invasive imaging modalities. Agreement between quantitative coronary angiography (QCA), intravascular ultrasound (IVUS) and optical coherence tomography (OCT) in the BVS is unknown. Forty five patients enrolled in the ABSORB cohort B1 study underwent coronary angiography, IVUS and OCT immediately post BVS implantation, and at 6 months. OCT estimated stent length accurately compared to nominal length (95% CI of the difference: −0.19; 0.37 and −0.15; 0.47 mm² for baseline and 6 months, respectively), whereas QCA incurred consistent underestimation of the same magnitude at both time points (Pearson correlation = 0.806). IVUS yielded low accuracy (95% CI of the difference: 0.77; 3.74 and −1.15; 3.27 mm² for baseline and 6 months, respectively), with several outliers and random variability test–retest. Minimal lumen area (MLA) decreased substantially between baseline and 6 months on QCA and OCT and only minimally on IVUS (95% CI: 0.11; 0.42). Agreement between the different imaging modalities is poor: worst agreement Videodensitometry-IVUS post-implantation (ICCa 0.289); best agreement IVUS-OCT at baseline (ICCa 0.767). All pairs deviated significantly from linearity (P < 0.01). Passing-Bablok non-parametric orthogonal regression showed constant and proportional bias between IVUS and OCT. OCT is the most accurate technique for measuring stent length, whilst QCA incurs systematic underestimation (foreshortening) and solid state IVUS incurs random error. Volumetric calculations using solid state IVUS are therefore not reliable. There is poor agreement for MLA estimation between all the imaging modalities studied, including IVUS-OCT, hence their values are not interchangeable.     

In-stent area stenosis on 64-slice multi-detector computed tomography coronary angiography: optimal cutoff value for minimum lumen cross-sectional area of coronary stents compared with intravascular ultrasound

We aimed to prospectively assess the optimal cutoff value for a minimum lumen cross-sectional area (CSA) on a 64-slice multidetector computed tomography (MDCT) compared with an intravascular ultrasound (IVUS). In 39 patients with 43 stents, the minimum lumen diameter, stent diameter, diameter stenosis, minimum lumen CSA, stent CSA, and area stenosis at the narrowest point were measured independently on 64-slice MDCT and IVUS images. For the assessment of diameter and CSA, 64-slice MDCT showed good correlations with IVUS (r = 0.82 for minimum lumen diameter, r = 0.66 for stent diameter, r = 0.79 for minimum lumen CSA, and r = 0.75 for stent CSA, respectively, P < 0.0001). For the assessment of diameter and area stenoses, a 64-slice MDCT showed good correlations with IVUS (r = 0.89 and 0.91, respectively, P < 0.0001). The overall sensitivity, specificity, positive predictive value, and negative predictive value to detect in-stent area restenosis (≥50 % area stenosis) of a 64-slice MDCT were 77, 100, 100, and 91 %, respectively. The cutoff value of a 64-slice MDCT, determined by receiver operator characteristic (ROC) analysis, was 5.0 mm² with 76.5 % sensitivity and 92.3 % specificity for significant in-stent area restenosis; the area under the ROC curve was 0.902 (P < 0.0001). A good correlation was found between a 64-slice MDCT and the IVUS, regarding the assessment of diameter and area stenoses of coronary stents in selected patients implanted with stents of more than 3 mm in diameter. Optimal cutoff value for the minimum lumen CSA of coronary stents on the 64-slice MDCT is 5 mm² to predict a CSA of 4 mm² on IVUS.     

Fusion of optical coherence tomographic and angiographic data for more accurate evaluation of the endothelial shear stress patterns and neointimal distribution after bioresorbable scaffold implantation: comparison with intravascular ultrasound-derived reconstructions

Intravascular ultrasound (IVUS)-based reconstructions have been traditionally used to examine the effect of endothelial shear stress (ESS) on neointimal formation. The aim of this analysis is to compare the association between ESS and neointimal thickness (NT) in models obtained by the fusion of optical coherence tomography (OCT) and coronary angiography and in the reconstructions derived by the integration of IVUS and coronary angiography. We analyzed data from six patients implanted with an Absorb bioresorbable vascular scaffold that had biplane angiography, IVUS and OCT investigation at baseline and 6 or 12 months follow-up. The IVUS and OCT follow-up data were fused separately with the angiographic data to reconstruct the luminal morphology at baseline and follow-up. Blood flow simulation was performed on the baseline reconstructions and the ESS was related to NT. In the OCT-based reconstructions the ESS were lower compared to the IVUS-based models (1.29 ± 0.66 vs. 1.87 ± 0.66 Pa, P = 0.030). An inverse correlation was noted between the logarithmic transformed ESS and the measured NT in all the OCT-based models which was higher than the correlation reported in five of the six IVUS-derived models (?0.52 ± 0.19 Pa vs. ?0.10 ± 0.04, P = 0.028). Fusion of OCT and coronary angiography appears superior to IVUS-based reconstructions; therefore it should be the method of choice for the study of the effect of the ESS on neointimal proliferation.     

Angiographically uncertain left main coronary artery narrowings: correlation with multidetector computed tomography and intravascular ultrasound

Background Angiographic assessment of left main coronary artery (LMCA) stenosis is often difficult and unreliable. To date, intravascular ultrasound (IVUS) is used to determine the significance of lesions in patients with LMCA stenosis of uncertain significance. We aimed to prospectively show the ability of multidetector computed tomography (MDCT) to assess LMCA luminal and plaque dimensions, and to characterize atherosclerotic plaque, as compared to IVUS and quantitative coronary angiography (QCA), in patients with angiographically uncertain LMCA stenosis. Methods Twenty patients, with angiographically uncertain LMCA stenosis, underwent coronary evaluation with IVUS, QCA and 16-slice MDCT. Minimal lumen diameter (MLD), minimal lumen area (MLA), lumen area stenosis (LAS) and plaque burden (PB) were assessed. Results The MLD (median [interquartile range]) was 3.2 mm (2.5–3.7) by IVUS, 2.8 mm (2.3–3.3) by QCA (r = 0.52, P < 0.05), and 2.8 mm (2.5–3.8) by MDCT (r = 0.77, P < 0.01). MDCT estimated MLA as 10.7 mm² (7.1–12.6) Vs. 9.9 mm² (6.5–13.5) by IVUS (r = 0.93, P < 0.01). Very high correlations were observed between MDCT and IVUS in assessing LAS (mean ± SD) (25.8 ± 19.1% and 29.0 ± 24.9% respectively, r = 0.83, P < 0.01), and PB (49.2 ± 15.8% and 49.2 ± 19.7% respectively, r = 0.94, P < 0.01). MDCT assigned plaque as being non-calcified with a sensitivity of 100%, while calcified plaques with a sensitivity of 75%. Conclusion A high degree of correlation was found between MDCT and IVUS regarding the assessment of minimal lumen diameter and area, lumen area stenosis and plaque burden as well as plaque characterization in patients with angiographically borderline LMCA stenosis. Therefore, in patients selected for non-invasive coronary tree evaluation, MDCT may provide a valuable tool for the assessment, decision-making and follow-up of patients with uncertain LMCA disease.     

Comparative assessment of three drug eluting stents with different platforms but with the same biodegradable polymer and the drug based on quantitative coronary angiography and optical coherence tomography at 12-month follow-up

The aim of this study was to compare neointima proliferation in three drug-eluting stents (DES) produced by the same company (Balton, Poland) which are covered with a biodegradable polymer and elute sirolimus (concentration: 1.0 and 1.2 µg/mm²), but have different stent platforms and strut thickness: stainless steel Prolim^® (115 µm) and BiOSS LIM^® (120 µm) and cobalt-chromium Alex^® (70 µm). We analyzed data of patients with quantitative coronary angiography (QCA) and optical coherence tomography (OCT) at 12 months from BiOSS LIM Registry, Prolim Registry and Alex OCT clinical trial. There were 56 patients enrolled, in whom 29 Prolim^® stents were deployed, in 11—BiOSS LIM^® and in 16—Alex stents. The late lumen loss was the smallest in Prolim^® subgroup (0.26?±?0.17 mm) and did not differ from Alex^® subgroup (0.28?±?0.47 mm). This parameter was significantly bigger in BiOSS^® subgroup (0.38?±?0.19 mm; p?<?0.05). In OCT analysis there was no statistically significant difference between Prolim^® and Alex^® subgroups in terms of mean neointima burden (24.6?±?8.6 vs. 19.27?±?8.11%) and neointima volume (28.16?±?15.10 vs. 24.51?±?17.64 mm³). In BiOSS^® group mean neointima burden (30.9?±?6.2%) and mean neointima volume (44.9?±?4.9 mm³) were significantly larger. The morphological analysis revealed that in most cases in all groups the neointima was homogenous with plaque presence only around stent struts. In the QCA and OCT analysis regular DES (Prolim^® and Alex^®) obtained similar results, whereas more pronounced response from the vessel wall was found in the BiOSS^® subgroup.     

Stent implant follow-up in intravascular optical coherence tomography images

The objectives of this article are (i) to utilize computer methods in detection of stent struts imaged in vivo by optical coherence tomography (OCT) during percutaneous coronary interventions (PCI); (ii) to provide measurements for the assessment and monitoring of in-stent restenosis by OCT post PCI. Thirty-nine OCT cross-sections from seven pullbacks from seven patients presenting varying degrees of neointimal hyperplasia (NIH) are selected, and stent struts are detected. Stent and lumen boundaries are reconstructed and one experienced observer analyzed the strut detection, the lumen and stent area measurements, as well as the NIH thickness in comparison to manual tracing using the reviewing software provided by the OCT manufacturer (LightLab Imaging, MA, USA). Very good agreements were found between the computer methods and the expert evaluations for lumen cross-section area (mean difference = 0.11 ± 0.70 mm²; r ² = 0.98, P < 0.0001) and the stent cross-section area (mean difference = 0.10 ± 1.28 mm²; r ² = 0.85, P value <  0.0001). The average number of detected struts was 10.4 ± 2.9 per cross-section when the expert identified 10.5 ± 2.8 (r ² = 0.78, P value < 0.0001). For the given patient dataset: lumen cross-sectional area was on the average (6.05 ± 1.87 mm²), stent cross-sectional area was (6.26 ± 1.63 mm²), maximum angle between struts was on the average (85.96 ± 54.23°), maximum, average, and minimum distance between the stent and the lumen were (0.18 ± 0.13 mm), (0.08 ± 0.06 mm), and (0.01 ± 0.02 mm), respectively, and stent eccentricity was (0.80 ± 0.08). Low variability between the expert and automatic method was observed in the computations of the most important parameters assessing the degree of neointimal tissue growth in stents imaged by OCT pullbacks. After further extensive validation, the presented methods might offer a robust automated tool that will improve the evaluation and follow-up monitoring of in-stent restenosis in patients.     

Long-term follow-up of renal arteries after radio-frequency catheter-based denervation using optical coherence tomography and angiography

Optical coherence tomography (OCT) imaging at the time of renal denervation (RDN) showed that procedure might cause spasm, intimal injury or thrombus formation. In the present study, we assessed the healing of renal arteries after RDN using OCT and renal angiography in long-term follow-up. OCT and renal angiography were performed in 12 patients (22 arteries) 18.41 ± 5.83 months after RNS. There were no adverse events or complications during the long-term follow-up. In ten patients (83 %), significant reductions of blood pressure was achieved without a change of the antihypertensive medications. We demonstrated the presence of 26 areas of focal intimal thickening identified by OCT in 10 (83 %) patients and in 14 (63 %) arteries. The mean area of focal intimal thickening was 0.054 ± 0.033 mm². No vessel dissection, thrombus, intimal tear or acute vasospasm were observed during the OCT analysis. Also, the quantitative angiography analysis revealed a significant reduction of the minimal and proximal lumen diameters at follow-up as compared to measurements obtained before RDN. Renal arteries have a favorable “long-term” vessel healing response after RDN. Focal intimal thickening and a modest reduction of the minimal lumen diameter may be observed after RF denervation. Further studies are needed to determine whether intravascular imaging may be helpful in evaluating the vessel healing of RF RDN.     

Optical coherence tomography guided in-stent thrombus removal in patients with acute coronary syndromes

The persistence of thrombus inside stent struts is a frequent event in patients with acute coronary syndromes (ACS) undergoing percutaneous coronary intervention (PCI), and this phenomenon might be associated with an increased risk of stent thrombosis. We sought to quantify by means of optical coherence tomography (OCT) the presence of in-stent thrombus after achievement of an optimal angiographic result in patients with ACS undergoing PCI. In addition, we evaluated the feasibility and safety of an OCT-guided strategy of in-stent thrombus removal. Eighty consecutive patients with ACS undergoing PCI were treated with two different strategies equally divided into two groups: angio-guided PCI, and OCT-guided PCI, in which additional OCT-driven in-stent balloon dilatation was adopted to reduce thrombus encroachment of the lumen. Overall in-stent thrombus area was 4.3 % with a maximal thrombus encroachment of 16.7 %. In the OCT-guided group, use of high pressure intra-stent dilatation led to a significant increase in stented area (9.6 ± 2.4 vs. 9.1 ± 2.49 mm², p = 0.002) and lumen area (9.2 ± 2.4 vs. 8.7 ± 2.3 mm², p < 0.001) and also significantly decreased in-stent thrombus area in absolute (0.35 ± 0.29 vs. 0.42 ± 0.30 mm², p = 0.001) and relative terms (3.58 ± 3.25 vs. 4.53 ± 3.01 %, p = 0.001). Values of TIMI flow, frame count and blush grade, as well as clinical outcomes were not detrimentally affected by such additional dilatations. The use of additional OCT-driven in-stent balloon dilatations is feasible, safe and might be effective in the treatment of in-stent thrombus for patients with ACS.     

In-stent fractional flow reserve variations and related optical coherence tomography findings: the FFR–OCT co-registration study

We sought to assess in-stent variations in fractional flow reserve (FFR) in patients with previous percutaneous coronary intervention (PCI) and to associate any drop in FFR with findings by optical coherence tomography (OCT) imaging. Suboptimal post-PCI FFR values were previously associated with poor outcomes. It is not known to which extent in-stent pressure loss contributes to reduced FFR. In this single-arm observational study, 26 patients who previously underwent PCI with drug-eluting stent or scaffold implantation were enrolled. Motorized FFR pullback during continuous intravenous adenosine infusion and OCT assessments was performed. Post-PCI FFR?<?0.94 was defined as suboptimal. At a median of 63 days after PCI (interquartile range: 59–64 days), 18 out of 26 patients (72%) had suboptimal FFR. The in-stent drop in FFR was significantly higher in patients with suboptimal FFR vs. patients with optimal FFR (0.08?±?0.07 vs. 0.01?±?0.02, p?<?0.001). Receiver operating characteristic curve analysis showed that an in-stent FFR variation of >?0.03 was associated with suboptimal FFR. In patients with suboptimal FFR, the OCT analyses revealed higher mean neointimal area (respectively: 1.06?±?0.80 vs. 0.51?±?0.23 mm²; p?=?0.018) and higher neointimal thickness of covered struts (respectively 0.11?±?0.07 vs. 0.06?±?0.01 mm; p?=?0.021). Suboptimal FFR values following stent-implantation are mainly caused by significant in-stent pressure loss during hyperemia. This finding is associated to a larger neointimal proliferation.     

Automatic quantification and characterization of coronary atherosclerosis with computed tomography coronary angiography: cross-correlation with intravascular ultrasound virtual histology

Plaque constitution on computed tomography coronary angiography (CTA) is associated with prognosis. At present only visual assessment of plaque constitution is possible. An accurate automatic, quantitative approach for CTA plaque constitution assessment would improve reproducibility and allows higher accuracy. The present study assessed the feasibility of a fully automatic and quantitative analysis of atherosclerosis on CTA. Clinically derived CTA and intravascular ultrasound virtual histology (IVUS VH) datasets were used to investigate the correlation between quantitatively automatically derived CTA parameters and IVUS VH. A total of 57 patients underwent CTA prior to IVUS VH. First, quantitative CTA quantitative computed tomography (QCT) was performed. Per lesion stenosis parameters and plaque volumes were assessed. Using predefined HU thresholds, CTA plaque volume was differentiated in 4 different plaque types necrotic core (NC), dense calcium (DC), fibrotic (FI) and fibro-fatty tissue (FF). At the identical level of the coronary, the same parameters were derived from IVUS VH. Bland–Altman analyses were performed to assess the agreement between QCT and IVUS VH. Assessment of plaque volume using QCT in 108 lesions showed excellent correlation with IVUS VH (r = 0.928, p < 0.001) (Fig. 1). The correlation of both FF and FI volume on IVUS VH and QCT was good (r = 0.714, p < 0.001 and r = 0.695, p < 0.001 respectively) with corresponding bias and 95 % limits of agreement of 24 mm³ (?42; 90) and 7.7 mm³ (?54; 70). Furthermore, NC and DC were well-correlated in both modalities (r = 0.523, p < 0.001) and (r = 0.736, p < 0.001). Automatic, quantitative CTA tissue characterization is feasible using a dedicated software tool.

Improvement of coronary morphology and blood flow after stenting

Intravascular ultrasound (IVUS) and intracoronary Doppler (ICD) were performed in eight patients (54.3±6.5 years, 6 male) immediately after PTCA and after stenting. ICD was also performed before PTCA. After PTCA, IVUS has demonstrated intimal rupture in all patients. After stenting, IVUS revealed wall wrapping of the intimal flap with a free lumen in all patients. The lumen diameter was 2.42±0.55 mm after PTCA and was 2.74±0.49 mm after stenting (p<0.001). The cross-sectional area increased from 4.70±1.99 mm² post-PTCA to 6.40±2.15 mm² post-stent (p<0.005). Coronary flow velocity reserve, calculated by the ratio of mean flow velocity at rest and after intracoronary papaverine administration, increased from 2.05±1.01 to 2.99±1.14 after PTCA (p = 0.015); and increased to 4.51±1.33 after stenting (p<0.001). The morphological data derived from IVUS correlated with the functional information obtained with ICD. In addition to its established role in bail out situations, stent implantation may be considered when a suboptimal morphological and functional result has been demonstrated.     

Treatment of small coronary arteries with a paclitaxel-coated balloon catheter

Background

Treatment of lesions in small coronary arteries by percutaneous transluminal coronary intervention is limited by a high recurrence rate. We assessed the use of a paclitaxel-coated balloon in this indication.

Methods

One-hundred eighteen patients with stenoses in small coronary vessels were treated by a paclitaxel-coated balloon (3 μg/mm²). The main inclusion criteria encompassed diameter stenosis of ≥70% and ≤22 mm in length with a vessel diameter of 2.25–2.8 mm. Follow-up angiography was performed at scheduled 6-month post-intervention or whenever driven by clinical or electrocardiographic signs of ischemia. The primary endpoint was angiographic in-segment late lumen loss.

Results

Eighty-two of 118 patients (70%) with a vessel diameter of 2.35 ± 0.19 mm were treated with the drug-coated balloon only, while 32 patients required additional stent deployment. The mean in-segment late lumen loss was 0.28 ± 0.53 mm. In patients treated with the drug-coated balloon only, the in-segment late lumen loss was 0.16 ± 0.38 mm. At 12 months, the rate of major adverse cardiac events was 15% which was primarily due to the need for target lesion revascularization in 14 patients (12%). In those with additional bare metal stent implantation geographical mismatch between coated-balloon dilatation and stent implantation was significantly associated with the occurrence of restenosis.

Conclusion

Treatment of coronary stenosis in small coronary vessels with the paclitaxel-coated balloon was well tolerated. It may offer an alternative to the implantation of a drug-eluting stent (ClinicalTrials.gov Identifier: NCT00404144).