Mechanism of high-speed rotational atherectomy and adjunctive balloon angioplasty revisited by quantitative coronary angiography: edge detection versus videodensitometry

Comparison of acute gain and late lumen loss after PCI with bioresorbable vascular scaffolds versus everolimus-eluting stents: an exploratory observational study prior to a randomised trial

AIMS

The study sought to compare the acute gain and two-year follow-up late lumen loss (LLL) between the Absorb bioresorbable vascular scaffold (BVS) and the analogous everolimus-eluting metallic stent (EES). The current analysis included all the patients recruited in the ABSORB Cohort B and SPIRIT II trials implanted with a single 3.0×18 mm device (Absorb BVS or EES) who underwent serial angiographic examinations at baseline and at two-year follow-up. The acute gain was defined as the difference between post- and preprocedural minimal lumen diameter (MLD). The in-stent/scaffold LLL was calculated as the difference in stent/scaffold segment between the post-procedural MLD and follow-up MLD. Thirty-three patients (33 lesions) implanted with the Absorb BVS, and 26 patients (28 lesions) implanted with the EES were studied. The acute gain was similar in the Absorb BVS group (1.23±0.38 mm) compared to the EES group (1.32±0.26 mm, p=0.29). The in-stent/scaffold LLL at two-year follow-up in the Absorb BVS group (0.26±0.19 mm) was also similar compared to the EES group (0.22±0.22 mm, p=0.29). Although the two groups had similar two-year clinical outcomes (major adverse cardiac events: Absorb BVS: 6.1% vs. EES: 0.0%), patients treated with the Absorb BVS exhibited a significantly lower two-year in-stent/scaffold MLD compared to the EES (2.02±0.26 mm vs. 2.22±0.34 mm, p=0.01). Although BVS and EES demonstrated similar two-year clinical outcomes, patients treated with the Absorb BVS exhibited a significantly lower two-year in-stent/scaffold MLD compared to patients treated with the EES. Appropriately powered randomised trials are necessary to confirm these exploratory results and evaluate their prognostic and clinical significance.

Quantitative videodensitometric technique for verification of optimal coronary stent implantation

Coronary angiography is not sensitive enough to define the results of stent implantation. Intravascular ultrasound defines accurately the anatomy of the vessel and the stent within the vessel and is thus considered the gold standard for defining the results of stent implantation. However intravascular ultrasound is an additional invasive procedure that is time consuming and expensive. This study describes a new simple quantitative videodensitometric technique, developed specifically to assess the results of stent implantation and compares the findings to intravascular ultrasound. In the proposed algorithm for the videodensitometric analysis, density profiles were constructed perpendicular to the long axis of the stented segment and each one was compared (after background subtraction) with a theoretic profile of a normal artery at that location. Density deficit index was determined at each point from the actual and theoretic profiles and a global volumetric density deficit index was calculated for each stent by integrating the deficit indices at all points along the stent. Similarly an area stenosis was determined at each point along the stent (using the stent and normal vessel cross sectional areas as defined by intravascular ultrasound) and the global volumetric stent stenosis was calculated by integrating the values of area stenosis along the stent. Twenty-five patients were evaluated immediately before and after coronary stent implantation. Global density deficit index improved from 66.1+/-16.4% before (after last balloon inflation) to 44.4+/-11.1% after stenting (P < 0.001). The shape of the curves of densitometric deficit indices along each stent were similar to the equivalent area stenosis curves as determined by intravascular ultrasound. The correlation (R = 0.74) between the global volumetric density deficit index and the global volumetric stent stenosis is statistically significant (P < 0.001). In conclusion, in this preliminary report we describe a new algorithm for videodensitometric analysis of the results of coronary stent implantation. As compared with intravascular ultrasound this method does not require an additional invasive procedure and it is quick cheap and easy to carry out.

ECG-gated three-dimensional intravascular ultrasound: feasibility and reproducibility of the automated analysis of coronary lumen and atherosclerotic plaque dimensions in humans

BACKGROUND

Automated systems for the quantitative analysis of three-dimensional (3D) sets of intravascular ultrasound (IVUS) images have been developed to reduce the time required to perform volumetric analyses; however, 3D image reconstruction by these nongated systems is frequently hampered by cyclic artifacts.

METHODS AND RESULTS

We used an ECG-gated 3D IVUS image acquisition workstation and a dedicated pullback device in atherosclerotic coronary segments of 30 patients to evaluate (1) the feasibility of this approach of image acquisition, (2) the reproducibility of an automated contour detection algorithm in measuring lumen, external elastic membrane, and plaque+media cross-sectional areas (CSAs) and volumes and the cross-sectional and volumetric plaque+media burden, and (3) the agreement between the automated area measurements and the results of manual tracing. The gated image acquisition took 3.9+/-1.5 minutes. The length of the segments analyzed was 9.6 to 40.0 mm, with 2.3+/-1.5 side branches per segment. The minimum lumen CSA measured 6.4+/-1.7 mm2, and the maximum and average CSA plaque+media burden measured 60.5+/-10.2% and 46.5+/-9.9%, respectively. The automated contour-detection required 34.3+/-7.3 minutes per segment. The differences between these measurements and manual tracing did not exceed 1.6% (SD<6.8%). Intraobserver and interobserver differences in area measurements (n=3421; r=.97 to.99) were <1.6% (SD<7.2%); intraobserver and interobserver differences in volumetric measurements (n=30; r=.99) were <0.4% (SD<3.2%).

CONCLUSIONS

ECG-gated acquisition of 3D IVUS image sets is feasible and permits the application of automated contour detection to provide reproducible measurements of the lumen and atherosclerotic plaque CSA and volume in a relatively short analysis time.

Computerized assessment of coronary lumen and atherosclerotic plaque dimensions in three-dimensional intravascular ultrasound correlated with histomorphometry

Intravascular ultrasound (IVUS), which depicts both lumen and plaque, offers the potential to improve on the limitations of angiography for the assessment of the natural history of atherosclerosis and progression or regression of the disease. To facilitate measurements and increase the reproducibility of quantitative IVUS analyses, a computerized contour detection system was developed that detects both the luminal and external vessel boundaries in 3-dimensional sets of IVUS images. To validate this system, atherosclerotic human coronary segments (n = 13) with an area obstruction > or = 40% (40% to 61%) were studied in vitro by IVUS. The computerized IVUS measurements (areas and volumes) of the lumen, total vessel, plaque-media complex, and percent obstruction were compared with findings by manual tracing of the IVUS images and of the corresponding histologic cross sections obtained at 2-mm increments (n = 100). Both area and volume measurements by the contour detection system agreed well with the results obtained by manual tracing, showing low mean between-method differences (-3.7% to 0.3%) with SDs not exceeding 6% and high correlation coefficients (r = 0.97 to 0.99). Measurements of the lumen, total vessel, plaque-media complex, and percent obstruction by the contour detection system correlated well with histomorphometry of areas (r = 0.94, 0.88, 0.80, and 0.88) and volumes (r = 0.98, 0.91, 0.83, and 0.91). Systematic differences between the results by the contour detection system and histomorphometry (29%, 13%, -9%, and -22%, respectively) were found, most likely resulting from shrinkage during tissue fixation. The results of this study indicate that this computerized IVUS analysis system is reliable for the assessment of coronary atherosclerosis in vivo.

Quantification of the minimal luminal cross-sectional area after coronary stenting by two- and three-dimensional intravascular ultrasound versus edge detection and videodensitometry

The use of 2-dimensional intravascular ultrasound (2-D IVUS) to improve the outcome of coronary stenting has gained clinical acceptance, and recently 3-D IVUS has been introduced to clinical practice. However, there have been no comprehensive studies comparing the measurements of the coronary dimensions after stenting obtained by the different approaches of IVUS and quantitative coronary angiography. We examined the minimal luminal cross-sectional area of 38 stents using 2-D IVUS, 3-D IVUS, and 2 standard methods of quantitative coronary angiography, edge detection (ED) and videodensitometry (VD). Correlations between 2-D IVUS and ED (r = 0.72; p < 0.0001), VD (r = 0.87; p < 0.0001), and 3-D IVUS (r = 0.81; p < 0.0001) were higher than the correlations seen between 3-D IVUS and ED (r = 0.58; p < 0.0005) and VD (r = 0.70; p < 0.0001). The measurements by 2-D and 3-D IVUS (8.32 +/- 2.50 mm2 and 8.05 +/- 2.66 mm2) were larger than the values obtained by the quantitative angiographic techniques ED and VD (7.55 +/- 2.22 mm2 and 7.27 +/- 2.21 mm2). Thus, concordance was seen among all of the 4 techniques, confirming the validity of using IVUS for determination of the minimal luminal cross-sectional area after coronary stenting. A particularly good correlation was found between VD and IVUS, perhaps because measurement of the luminal area is the basic quantification approach of both techniques, whereas the lower correlations of ED with IVUS and VD may be explained by the dependence of ED on the angiographic projections used, which is especially important in eccentric stent configurations.

Morphometric analysis in three-dimensional intracoronary ultrasound: an in vitro and in vivo study performed with a novel system for the contour detection of lumen and plaque

Currently, automated systems for quantitative analysis by intracoronary ultrasound (ICUS) are restricted to the detection of the lumen. The aim of this study was to determine the accuracy and reproducibility of a new semiautomated contour detection method, providing off-line identification of the intimal leading edge and external contour of the vessel in three-dimensional ICUS. The system allows cross-sectional and volumetric quantification of lumen and of plaque. It applies a minimum-cost algorithm and the concept that edge points derived from previously detected longitudinal contours guide and facilitate the contour detection in the cross-sectional images. A tubular phantom with segments of various luminal dimensions was examined in vitro during five catheter pull-backs (1 mm/sec), and subsequently 20 diseased human coronary arteries were studied in vivo with 2.9F 30 MHz mechanical ultrasound catheters (200 images per 20 mm segment). The ICUS measurements of phantom lumen area and volume revealed a high correlation with the true phantom areas and volumes (r = 0.99); relative mean differences were -0.65% to 3.86% for the areas and 0.25% to 1.72% for the volumes of the various segments. Intraob-server and interobserver comparisons showed high correlations (r = 0.95 to 0.98 for area and r = 0.99 for volume) and small mean relative differences (-0.87% to 1.08%), with SD of lumen, plaque, and total vessel measurements not exceeding 7.28%, 10.81%, and 4.44% (area) and 2.66%, 2.81%, and 0.67% (volume), respectively. Thus the proposed analysis system provided accurate measurements of phantom dimensions and can be used to perform highly reproducible area and volume measurements in three-dimensional ICUS in vivo.