Optical Coherence Tomography Pullbacks Research Articles

Vascular lesions induced by renal nerve ablation as assessed by optical coherence tomography: pre- and post-procedural comparison with the Simplicity® catheter system and the EnligHTN™ multi-electrode renal denervation catheter

AimsCatheter-based renal nerve ablation (RNA) using radiofrequency energy is a novel treatment for drug-resistant essential hypertension. However, the local endothelial and vascular injury induced by RNA has not been characterized, although this importantly determines the long-term safety of the procedure. Optical coherence tomography (OCT) enables in vivo visualization of morphologic features with a high resolution of 10–15 µm. The objective of this study was to assess the morphological features of the endothelial and vascular injury induced by RNA using OCT.Methods and resultsIn a prospective observational study, 32 renal arteries of patients with treatment-resistant hypertension underwent OCT before and after RNA. All pre- and post-procedural OCT pullbacks were evaluated regarding vascular changes such as vasospasm, oedema (notches), dissection, and thrombus formation. Thirty-two renal arteries were evaluated, in which automatic pullbacks were obtained before and after RNA. Vasospasm was observed more often after RNA then before the procedure (0 vs. 42%, P < 0.001). A significant decrease in mean renal artery diameter after RNA was documented both with the EnligHTN™ (4.69 ± 0.73 vs. 4.21 ± 0.87 mm; P < 0.001) and with the Simplicity® catheter (5.04 ± 0.66 vs. 4.57 ± 0.88 mm; P < 0.001). Endothelial-intimal oedema was noted in 96% of cases after RNA. The presence of thrombus formations was significantly higher after the RNA then before ablation (67 vs. 18%, P < 0.001). There was one evidence of arterial dissection after RNA with the Simplicity® catheter, while endothelial and intimal disruptions were noted in two patients with the EnligHTN™ catheter.ConclusionHere we show that diffuse renal artery constriction and local tissue damage at the ablation site with oedema and thrombus formation occur after RNA and that OCT visualizes vascular lesions not apparent on angiography. This suggests that dual antiplatelet therapy may be required during RNA.

Early vessel healing of the Avantgarde cobalt-chromium coronary stent

Uncoverage and malapposition of stent struts at optical coherence tomography (OCT) have been associated with stent thrombosis. Stent uncoverage by OCT is being used as a surrogate to address the propensity of a stent to develop thrombosis. We aimed to appraise early vessel healing in patients with ST-elevation myocardial infarction (STEMI) treated with the novel Avantgarde stent. Patients with STEMI and multivessel disease were enrolled. The stent deployed on the infarct-related artery was imaged by frequency domain-OCT during deferred intervention (4-7 days apart). The primary end-point was the percentage of uncovered struts. Secondary end-points were the percentage of malapposed struts and struts covered with thrombus. Twenty patients (20 lesions) were enrolled, with 18 (18 stents) achieving a complete OCT pull-back and thus entering the final analysis (1497 cross-sections, 11 446 struts). Uncovered struts were 3.9%, whilst 8.0% of struts were malapposed and 2.6% were covered by thrombus. At per-stent analysis, all stents but two had a homogeneous distribution of strut coverage (i.e. % of uncovered struts ≥10). This study, originally exploiting OCT data early after stenting in STEMI patients, shows that the Avantgarde stent is associated with favourable vessel healing features.

Immediate results of bifurcational stenting assessed with optical coherence tomography

A tubular stent may adapt with difficulty to coronary bifurcation lesions (CBLs). Time domain or frequency domain (FD) optical coherence tomography (OCT) was performed to assess strut apposition immediately after stent implantation across four segments inside the bifurcation, in a consecutive series of patients. OCT pullbacks were performed in the main vessel (MV). A total of 13,142 struts in 45 CBL in 41 patients were assessed. Strut malapposition was significantly more frequent in the half bifurcation facing the side-branch (SB) ostium (42.9%) than in the proximal segment of the bifurcation 11.8%, half bifurcation opposite the SB 6.7%, or the distal segment 5.7% (all P < 0.0001). Lesions (n = 15) treated with stenting of both MV and SB had a total higher rate of malapposition than those (n = 30) treated with stenting of the MV only (17.6% vs. 9.5%; P = 0.0014). In latter group, lesions treated with FD-OCT-guided stent implantation (n = 13) presented a lower rate of malapposition than those treated with conventional angiographic-guided stent implantation (n = 17) (7.1% vs. 17.5%; P = 0.005). In CBL, strut malapposition is particularly high at the SB ostium. However, a strategy of stenting MV only with adjunctive FD-OCT guidance is associated with lower rates of malapposition.

Safety and Feasibility of Intravascular Optical Coherence Tomography Using a Nonocclusive Technique to Evaluate Carotid Plaques Before and After Stent Deployment

To evaluate the safety and feasibility of optical coherence tomography (OCT) in patients with carotid stenosis undergoing carotid artery stenting (CAS). In a prospective study, 25 consecutive patients (15 men; mean age 74±4 years) undergoing protected CAS were enrolled and underwent high-definition (homoaxial resolution 10 µm) OCT image acquisition before stent deployment, immediately after stent placement, and following postdilation of the stent (3 scans/patient). Pullbacks were started during a nonocclusive flush, mechanically injecting 24 mL of 50% diluted contrast at 6 mL/s to displace blood from the artery. Two independent physicians judged the quality of images on a predefined 1-10 scale. The proportions of specific agreement and kappa values (κ) were calculated. No procedural or in-hospital neurological complications occurred (any stroke/death 0%). The technical success of OCT pullbacks was 97.3% (73/75). The total amount of contrast was 86±18 mL/patient. No significant alteration in glomerular filtration rate or any other significant adverse event occurred. The images obtained were of high quality (mean value 8.1 out of 10), with good inter- and intraobserver agreement (κ = 0.81-0.87 and κ = 0.95, respectively). OCT images revealed innovative features such as rupture of the fibrous cap, plaque prolapse, and stent malapposition in a high percentage of the patients (range 24%-100%). Intravascular OCT during a nonocclusive flush appears to be feasible and safe in carotid arteries. Since some original and unexpected information after CAS has been made available for the first time at such a high definition, future studies with OCT should focus on the interaction between carotid plaque and stent design, which might revolutionize our understanding of the mechanisms of carotid stenting, as well as influence our clinical policies.

When the doctor needs an engineer to be the matchmaker

When the doctor needs an engineer to be the matchmaker

Dynamic Nature of Coronary Plaques and Clinical Outcomes in Diabetic Patients: Is Change in Itself Bad?

We evaluated the geographic distribution of thin-cap fibroatheromas (TCFAs) in the coronary arteries using optical coherence tomography (OCT), a high-resolution imaging modality.Plaque rupture is the most frequent cause of acute myocardial infarction (AMI). It has been recognized that TCFA is the primary plaque type at the site of plaque rupture.We performed 3-vessel OCT examinations in 55 patients: 35 AMI and 20 stable angina pectoris patients. The criteria for TCFA in an OCT image was a lipid-rich plaque with fibrotic cap thickness <65 μm. The distance between each TCFA location and the respective coronary artery ostium was measured with motorized OCT imaging pullback. The total length of all 3 coronary arteries imaged by OCT pullbacks was 82 ± 21 mm in the left anterior descending coronary artery (LAD), 67 ± 26 mm in the left circumflex coronary artery (LCx), and 104 ± 32 mm in the right coronary artery (RCA).OCT detected 94 TCFAs in 165 coronary arteries. The minimum fibrous-cap thickness of TCFAs was 57.4 ± 5.4 μm in AMI patients, and 55.9 ± 7.3 μm in stable angina pectoris patients (p = 0.4). Of the total of 94 TCFAs, 28 were detected in the LAD, 18 in the LCx, and 48 in the RCA. Most LAD TCFAs were located between 0 and 30 mm from the LAD ostium (76%). Conversely, LCx and RCA TCFAs were evenly distributed throughout the entire coronary length. The clustering of the TCFAs was similar in culprit segments as compared with nonculprit segments. In AMI patients, most LAD TCFAs were distributed near side branches, mainly positioned opposite the side branch bifurcation.Three-vessel OCT imaging showed that TCFAs tend to cluster in predictable spots within the proximal segment of the LAD, but develop relatively evenly in the LCx and RCA arteries.

Automatic segmentation of in-vivo intra-coronary optical coherence tomography images to assess stent strut apposition and coverage

The implantation of intracoronary stents is currently the standard approach for the treatment of coronary atherosclerotic disease. The widespread adoption of this technology has boosted an intensive research activity in this domain, with continuous improvements in the design of these devices, aiming at reducing problems of restenosis (re-narrowing of the stented segment) and thrombosis (sudden occlusion due to thrombus formation). Recently, a new, light-based intracoronary imaging modality, optical coherence tomography (OCT), was developed and introduced into clinical practice. Due to its very high axial resolution (10-15μm), it allows for in vivo evaluation of both stent strut apposition and neointima coverage (a marker of healing of the treated segment). As such, it provides valuable information on proper stent deployment, on the behaviour of different stent types in-vivo and on the effect of new types of stents (e.g. drug-eluting stents) on vessel wall healing. However, the major drawback of the current OCT methodology is that analysis of these images requires a tremendous amount of-currently manual-post-processing. In this manuscript, an algorithm is presented that allows for fully automated analysis of stent strut apposition and coverage in coronary arteries. The vessel lumen and stent struts are automatically detected and segmented through analysis of the intensity profiles of the A-lines. From these data, apposition and coverage can then be measured automatically. The algorithm was validated using manual assessments by two experienced operators as a reference. High Pearson's correlation coefficients were found (R=0.96-0.97) between the automated and manual measurements while Bland-Altman analysis showed no significant bias with good limits of agreement. As such, it was shown that the presented algorithm provides a robust and fast tool to automatically estimate apposition and coverage of stent struts in in-vivo OCT pullbacks. This will be important for the integration of this technology in clinical routine and for the analysis of datasets of larger clinical trials.

Fusion of 3D QCA and IVUS/OCT

The combination/fusion of quantitative coronary angiography (QCA) and intravascular ultrasound (IVUS)/optical coherence tomography (OCT) depends to a great extend on the co-registration of X-ray angiography (XA) and IVUS/OCT. In this work a new and robust three-dimensional (3D) segmentation and registration approach is presented and validated. The approach starts with standard QCA of the vessel of interest in the two angiographic views (either biplane or two monoplane views). Next, the vessel of interest is reconstructed in 3D and registered with the corresponding IVUS/OCT pullback series by a distance mapping algorithm. The accuracy of the registration was retrospectively evaluated on 12 silicone phantoms with coronary stents implanted, and on 24 patients who underwent both coronary angiography and IVUS examinations of the left anterior descending artery. Stent borders or sidebranches were used as markers for the validation. While the most proximal marker was set as the baseline position for the distance mapping algorithm, the subsequent markers were used to evaluate the registration error. The correlation between the registration error and the distance from the evaluated marker to the baseline position was analyzed. The XA-IVUS registration error for the 12 phantoms was 0.03 ± 0.32 mm (P = 0.75). One OCT pullback series was excluded from the phantom study, since it did not cover the distal stent border. The XA-OCT registration error for the remaining 11 phantoms was 0.05 ± 0.25 mm (P = 0.49). For the in vivo validation, two patients were excluded due to insufficient image quality for the analysis. In total 78 sidebranches were identified from the remaining 22 patients and the registration error was evaluated on 56 markers. The registration error was 0.03 ± 0.45 mm (P = 0.67). The error was not correlated to the distance between the evaluated marker and the baseline position (P = 0.73). In conclusion, the new XA-IVUS/OCT co-registration approach is a straightforward and reliable solution to combine X-ray angiography and IVUS/OCT imaging for the assessment of the extent of coronary artery disease. It provides the interventional cardiologist with detailed information about vessel size and plaque size at every position along the vessel of interest, making this a suitable tool during the actual intervention.

3-Dimensional Optical Coherence Tomography Assessment of Jailed Side Branches by Bioresorbable Vascular Scaffolds: A Proposal for Classification

The purpose of this study is to assess jailing of side branches (SB) by the everolimus-eluting, bioresorbable vascular scaffold (BVS) with 3-dimensional (3D) optical coherence tomography (OCT) reconstruction. Because BVS struts at the SB orifice are suspected of being bioresorbed and/or forming a neointimal bridge, OCT has been used to evaluate the struts in detail at that particular site. Our understanding of the 3D relationship of the strut and the SB orifice is limited by the use of 2-dimensional OCT images. Fourier-domain OCT enables reliable 3D reconstruction of coronary vessels. The ABSORB Cohort B (A Clinical Evaluation of the Bioabsorbable Everolimus Eluting Coronary Stent System in the Treatment of Patients With de Novo Native Coronary Artery Lesions) trial is a multicenter single-arm trial to assess the safety and performance of the BVS. Fourier-domain OCT pullbacks (C7-XR system, LightLab Imaging Inc., Westford, Massachusetts) are obtained at pullback speed of 20 mm/s and 3D renderings are performed. The orifices of the SB are assessed visually. The area of SB orifice and the number of strut-free compartments delineated by the BVS struts are evaluated. Fifty-one OCT pullbacks were acquired: 33 pullbacks were imaged with Fourier-domain OCT and 27 treated segments had 46 side branches. Three-dimensional assessment was feasible in 87% (40 of 46) of pullbacks. The mean area of the SB orifice was 1.16 +/- 1.02 mm(2). The mean number of strut-free compartments was 2.0 +/- 1.1. The classification of the overhanging struts is proposed. This study demonstrates that 3D OCT reconstruction is feasible to evaluate the orifices of SB jailed with BVS. (ABSORB Clinical Investigation, Cohort B; NCT00856856).

Treatment of a large thrombus containing lesion with the MGuard™ protective net coronary stent system: optical coherence tomographic evidence of complete plaque sealing

Avoidance of distal embolization is the key of success in the percutaneous treatment of patients with ST elevation myocardial infarction. Embolization may lead to microvascular obstruction, and consequently impairment of myocardial perfusion with increased infarct size and mortality [1, 2]. Different types of devices have been proposed to avoid this issue. Prospective randomized clinical trials have shown the beneficial effect of thrombus aspiration devices in the setting of primary percutaneous coronary intervention (PCI) [3, 4]. Recently, the use of MGuard net coronary stent system (MGS, Inspire-MD, Tel Aviv, Israel) in the setting of primary PCI has shown high rate of myocardial reperfusion and angiographic procedural success [5]. MGS is a new stainless-steel closed-cell design stent concept. Other than conventional available bare-metal stents (BMS), it has an ultrathin flexible polyethylene terephthalate mesh sleeve that is anchored to the external surface of the struts. This biocompatible microfiber net (string diameter 10–22 lm) has minimal effects on stent crossing profile and deliverability (Fig. 1). During stent deployment, the net stretches and slides over the expanding stent struts, creating custom designed pores of &200 lm in diameter. The idea of this design is to entrap the thrombus burden between stent mesh and the wall of the artery, isolating the high-thrombogenic intima components and preventing the ‘‘snow plug effect’’. This is the first time, at our knowledge, that the optical coherence tomography (OCT) assessment of MGS implantation for the treatment of a large thrombus burden right coronary artery (RCA) lesion is being reported. A 78-year-old female with mild hypertension and dislipidemia, previously treated with dual chamber pacemaker implant, was admitted at our hospital for coronary angiography following an inferior ST elevation myocardial infarction treated with a partial effective systemic thrombolytic therapy with reteplase. At the time of coronary angiography, the patient was already on double antiplatelet therapy (600 mg loading dose of clopidogrel and 300 mg loading dose of acetylsalicylic acid). The angiography showed a significant mid-RCA lesion with large thrombus burden (Fig. 2a), while there were no lesions on the left coronary system. PCI was then performed using the standard approach. A bolus of 80 UI/kg of unfractioned heparin was given at the start of procedure. No glycoprotein IIb/IIIa inhibitors were given during the procedure to avoid bleeding complications related to the already administered anti-platelet therapy and patient’s age. After cannulation of the RCA with a 7 French side holes Judking right 4 guiding catheter, a BMW guide wire (Abbott Vascular, Redwood City, CA, USA) was advanced until the distal postero-lateral branch and an OCT scan using the C7XR OCT image system (LightLab Imaging Inc., Westford, MA, USA) was then performed using the nonocclusive flushing technique [6]. The OCT pullback showed a tight stenosis of RCA with a very large intraluminal stratified red thrombus (Fig. 2b). Subsequently, it was decided to perform a direct stenting with 4.0/24 mm MGS implantation, which was deployed at 16 atm. The OCT was repeated thereafter showing a malapposition at the mid part of the stent. Therefore, post-dilatation was A. La Manna S. D. Tomasello C. Tamburino Clinical Division of Cardiology, Department of Internal Medicine and Systemic Disease, Ferrarotto Hospital, University of Catania, Catania, Italy

OCT Assessment of Thin-Cap Fibroatheroma Distribution in Native Coronary Arteries

We evaluated the geographic distribution of thin-cap fibroatheromas (TCFAs) in the coronary arteries using optical coherence tomography (OCT), a high-resolution imaging modality. Plaque rupture is the most frequent cause of acute myocardial infarction (AMI). It has been recognized that TCFA is the primary plaque type at the site of plaque rupture. We performed 3-vessel OCT examinations in 55 patients: 35 AMI and 20 stable angina pectoris patients. The criteria for TCFA in an OCT image was a lipid-rich plaque with fibrotic cap thickness <65 microm. The distance between each TCFA location and the respective coronary artery ostium was measured with motorized OCT imaging pullback. The total length of all 3 coronary arteries imaged by OCT pullbacks was 82 +/- 21 mm in the left anterior descending coronary artery (LAD), 67 +/- 26 mm in the left circumflex coronary artery (LCx), and 104 +/- 32 mm in the right coronary artery (RCA). OCT detected 94 TCFAs in 165 coronary arteries. The minimum fibrous-cap thickness of TCFAs was 57.4 +/- 5.4 microm in AMI patients, and 55.9 +/- 7.3 microm in stable angina pectoris patients (p = 0.4). Of the total of 94 TCFAs, 28 were detected in the LAD, 18 in the LCx, and 48 in the RCA. Most LAD TCFAs were located between 0 and 30 mm from the LAD ostium (76%). Conversely, LCx and RCA TCFAs were evenly distributed throughout the entire coronary length. The clustering of the TCFAs was similar in culprit segments as compared with nonculprit segments. In AMI patients, most LAD TCFAs were distributed near side branches, mainly positioned opposite the side branch bifurcation. Three-vessel OCT imaging showed that TCFAs tend to cluster in predictable spots within the proximal segment of the LAD, but develop relatively evenly in the LCx and RCA arteries.

Use of optical coherence tomography in interventional cardiology

Optical coherence tomography (OCT) has offered a greater understanding of coronary atherosclerosis with the ability to visualize plaque and quantify the thin, fibrous cap. Furthermore, OCT is able to traverse many of the limitations of angiography and intravascular ultrasound when imaging coronary stents in vivo. These applications are as a result of the use of near-infrared light, permitting an almost ‘histological’ resolution of the coronary artery. Novel developments with faster OCT pullback speeds (up to 20 mm/s with the next generation Fourier-domain systems) will further simplify the procedural requirements, meaning that the use of a proximal occlusion balloon is eliminated. Hence, OCT is, and will continue to be a unique imaging modality that is able to help improve our understanding of the atherosclerotic process and shed light on the all important interaction between coronary stents and the vessel wall.

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 mm(2); r (2) = 0.98, P < 0.0001) and the stent cross-section area (mean difference = 0.10 ± 1.28 mm(2); 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 mm(2)), stent cross-sectional area was (6.26 ± 1.63 mm(2)), 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.

Current and future developments in intracoronary optical coherence tomography imaging

Optical coherence tomography (OCT) has become a key intracoronary imaging modality able to traverse some of the limitations of angiography and intravascular ultrasound. In vivo imaging with high resolution (around 15 micrometres) has given unique insights into not only atherosclerotic plaque, but also to the understanding of tissue responses underlying stent implantation. Novel developments with faster OCT pullback speeds will further simplify the procedural requirements and eventually eliminate the need for proximal vessel balloon occlusion during image acquisition. This report explores the current and future developments in OCT technology that will see this unique imaging modality become a key player in both the clinical and research arena for the interventional cardiologist.

A novel approach for quantitative analysis of intracoronary optical coherence tomography: High inter‐observer agreement with computer‐assisted contour detection

This study aims to examine observer-related variability of quantitative optical coherence tomography (OCT) derived measurements from both in vitro and in vivo pullback data. Intravascular OCT is a new imaging modality using infrared light and offering 10 times higher image resolution (15 microm) compared to intravascular ultrasound. The quantitative analysis of in vivo intracoronary OCT imaging is complicated by the presence of blood, motion artifacts and the large quantity of information that has to be processed. We developed a standardized, automated quantification process for intracoronary OCT pullback data with inter-observer variability assessed both in vitro by using postmortem human coronary arteries and in vivo by studying simple and complex coronary pathology and outcomes following stent implantation. The consensus between measurements by two observers was analyzed using the intraclass and interclass correlation coefficient and the reliability coefficients. Bland-Altman plots were generated to assess the relationship between variability and absolute measurements. In vitro OCT assessment was performed in nine postmortem coronary arteries. The time needed for semiautomated contour detection of a 15-mm long coronary segment was approximately 40 min. The absolute and relative difference between lumen area measurements derived from two observers was low [0.02 +/- 0.10 mm(2); (0.3 +/- 0.5)% respectively] with excellent correlation confirmed by linear regression analysis (R(2) = 0.99; P < 0.001). Similarly, in vivo measurements demonstrated a high correlation with the main source of inter-observer variation occurring as a result of coronary dissection and motion artifact. The absolute and relative difference between measurements were 0.11 +/- 0.33 mm(2) (1.57 +/- 0.05)% for lumen area (R(2) = 0.98; P < 0.001), 0.17 +/- 0.68 mm(2) (1.44 +/- 0.08)% for stent area (R(2) = 0.94; P < 0.001), and 0.26 +/- 0.72 mm(2) (14.08 +/- 0.37)% for neointimal area (R(2) = 0.78; P < 0.001). Highly accurate computer-assisted quantitative analysis ofintracoronary OCT pullbacks is feasible with low inter-observer variability. The presented approach allows for observer independent analysis of detailed vessel structures, and may be a valuable tool for future longitudinal studies incorporating OCT.

From Bench to Bedside A Novel Technique of Acquiring OCT Images

Optical coherence tomography (OCT), a high resolution intravascular imaging technique, requires blood displacement for reliable image acquisition and the current technique uses a soft occlusion balloon plus saline injection in the coronary artery. A non-occlusive technique based on manual infusion of a viscous iso-osmolar solution has been developed and tested and validated through a 2-phase study. OCT assessment was performed with the M2 LightLab OCT (LightLab Imaging, Westford, MA, USA) image-wire in 3 swine by infusing 30 ml of each of 3 solutions differing in viscosity, osmolarity and electrolytic composition (A: iodixanol 320 and Lactated Ringer's; B: iodixanol 320 and 50% albumin; C: iodixanol 320). Image quality and adverse effects were evaluated. The solution with the best image quality/side-effect ratio was tested in 44 patients. The best image quality/side-effect ratio was obtained in the swine model with solution C, which enabled the study of arterial segments of 29.8+/-2.1 mm in length. The results were confirmed in the human study (average length of 28.3+/-2.5 mm and absence of major complications and/or major arrhythmias). Repeated OCT pull-back in the first 10 patients enabled comparison of 1,572 matched cross-sections with an excellent correlation for reproducibility (R=0.96; p<0.001). The non-occlusive technique using iodixanol 320 has an excellent ratio of safety, feasibility and efficacy.