Cardiovascular Angiography Analysis System Research Articles

Impact of wall shear stress affected by anatomical difference between acute and chronic coronary syndrome in patients with LAD proximal disease

Abstract Recent hemodynamic studies have demonstrated that progression of coronary atherosclerosis occurs at low wall share-stress site, whereas plaque rupture frequently occurs at high share stress site. It is well recognized that wall shear stress is relatively low along the outer walls of the bifurcation. We investigated consecutive 140 patients (77 with acute coronary syndrome (ACS) and 63 with chronic coronary syndrome (CCS) performed PCI for LAD proximal lesions (AHA seg.6) from January 2016 to December 2019. In CCS group, entry criteria included stenosis of at least 90% in the LAD proximal lesion or at least 70% in the LAD proximal lesion and objective evidence of myocardial ischemia (inducible ischemia with either exercise or pharmacologic vasodilator stress or with pressure wire). Exclusion criteria were patients with maintenance dialysis, chronic total occlusion lesions, in-stent restenosis, and clinically diagnosed unstable angina without troponin I elevation. We measured the distance from LMT distal carina to the culprit site (Distance) and plaque location (Location) with intravascular ultrasound and angle between LMT and LAD with cardiovascular angiography analysis system (CAAS) (Angle). The two groups were generally well balanced with regard to baseline clinical characteristics. The mean (±SD) age of the patients was 69.0±11.8 years, and 75% were men. Medication at baseline was also similar between two groups except higher prevalence of statin prescription in CCS group. The Distance was shorter and Angle was steeper in CCS group than in ACS group. The number of patients with Angle less than 150 degrees and with Location in the lateral wall side was much more in CCS group. In this study, plaques in CCS were frequently observed at low shear stress site, whereas those in ACS at high shear stress site. Plaque progression in CCS may be associated with low wall shear stress, and high shear stress may play key role in plaque rupture in ACS. This anatomical difference can partly explain the different mechanisms of onset between of ACS and CCS. Funding Acknowledgement Type of funding sources: None. Anatomical differenceCharacteristics and results

Advances in two-dimensional quantitative coronary angiographic assessment of bifurcation lesions: improved small lumen diameter detection and automatic reference vessel diameter derivation

To validate a new two dimensional (2-D) bifurcation quantitative coronary angiography (QCA) software. In the latest edition of the Cardiovascular Angiography Analysis System (CAAS 5.9; Pie Medical Imaging, Maastricht, The Netherlands) video-densitometric information is dynamically integrated into the edge-detection algorithm of 11- and 6-segment models to reduce overestimation of small diameters. Furthermore, automatic reference obstruction analysis was optimised. Values of the minimal lumen diameter (MLD), reference vessel diameter (RVD), percent diameter stenosis (DS) and bifurcation angle (BA) for the different bifurcation segment models were validated against precision manufactured plexiglass phantoms. In anteroposterior views, accuracy and precision (mean difference±SD) of 11- and 6-segment models for MLD were 0.013±0.082 mm vs. 0.003±0.100 mm, for RVD -0.030±0.047 mm vs. -0.029±0.045 mm and for DS -0.48±3.66% vs. -0.11±3.97%. In smaller vessel segments (true MLD <0.7 mm), MLD overestimation was reduced. Inter-observer variability for MLD, RVD and DS for either model was ≤0.052 mm, ≤0.043 mm and ≤2.24%, respectively. Agreement between models for MLD, RVD and DS was ±0.076 mm, ±0.021 mm and ±2.53%, respectively. Accuracy and precision for BA were -2.6±3.5°, and variability was ≤1.2°. Accuracy and precision for diameter-derived parameters were slightly decreased in projections with 30° rotation; BA precision dropped to 6.2°. MLD quantification is improved for true MLD <0.7 mm, resulting in highly accurate and precise diameter measurements over the entire range of phantom diameters. Automatic reference obstruction analysis provides highly accurate, precise and reproducible RVD and DS measurements.

Two‐dimensional quantitative coronary angiographic models for bifurcation segmental analysis

Quantitative coronary angiography (QCA) analysis for bifurcation lesions needs to be standardized. In vitro validation of two models for bifurcation QCA segmental analysis. In the latest edition of the Cardiovascular angiography analysis system (CAAS 5v8, Pie Medical Imaging, Maastricht, The Netherlands) a 6-segment model for two-dimensional coronary bifurcation analysis was implemented next to the currently available 11-segment model. Both models were validated against 6 precision manufactured plexiglas phantoms, each of them mimicking a vessel with three successive bifurcation lesions with variable anatomy and Medina class. The phantoms were filled with 100% contrast agent and imaged with a biplane gantry. Images acquired in antero-posterior (AP) direction by either C-arm and at 30° right and left anterior oblique angulation were analyzed by two independent analysts, blinded to the actual dimensions. Manual correction of the contours was not allowed. Measurements for minimal lumen diameter (MLD), reference vessel diameter (RVD), percent diameter stenosis (DS) and bifurcation angle (BA) were compared with the true phantom dimensions. In AP views the accuracy and precision (mean difference ± SD) of 11- and 6-segment model for MLD, RVD, and DS were 0.065 ± 0.128 mm vs. 0.058 ± 0.142 mm, -0.021 ± 0.032 mm vs. -0.022 ± 0.030 mm, and -2.45% ± 5.07% vs. -2.28% ± 5.29%, respectively. Phantom MLD values ≤ 0.7 mm were systematically overestimated; if excluded, MLD accuracy and precision became 0.015 ± 0.106 mm and 0.004 ± 0.125 mm for the 11- and 6-segment model, respectively. Accuracy and precision for BA were -2.2° ± 3.3°. Interobserver variability for MLD, RVD, DS, and BA for either model was ≤ 0.049 mm, ≤ 0.056 mm, ≤ 2.77%, and 1.6°, respectively. Agreement between models for MLD, RVD, and DS was ± 0.079 mm, ± 0.011 mm, and ± 2.07%. Accuracy and precision for diameter-derived parameters were slightly decreased in angulated projections; precision for BA measurements dropped to 6.1°. The results of both models are highly reproducible and for phantom MLD values >0.7 mm in excellent agreement with the true dimensions.

Dual quantitative coronary angiography: a novel approach to quantify intracoronary thrombotic burden

To validate and test in vivo a new modality of quantitative coronary angiography (QCA), dual QCA (D-QCA), developed to quantify intracoronary thrombotic burden (ITB). Calculation of ITB with D-QCA is based on the discrepancy of luminal areas assessed with edge detection (ED) and video-densitometry (VD), measured with Cardiovascular Angiography Analysis System II. Experimental validation was first performed in phantoms with known obstructive volumes. In vivo assessment of thrombotic burden changes was performed in angiograms from 19 patients with large ITB, obtained before and after antithrombotic treatment, and compared with semi-quantitative assessment (TIMI thrombus grade (TTG)). A good correlation between D-QCA and true occlusive volumes was found (y = 9.21+0.99x, r = 0.996). Intra- and inter-observer variability was 2.77 +/- 10.97 mm3 (p = 0.50) and -1.28 +/- 6.99 mm3 (p = 0.62) respectively. In vivo, D-QCA demonstrated a significant reduction in ITB resulting from treatment (137.22 +/- 120.13 mm3 before and 104.72 +/- 99.19 mm3 after treatment, p = 0.001). Overall, TTG also decreased (3.63 +/- 0.68 before and 3.11 +/- 1.20 after, p = 0.008), but in those nine (47%) patients in which remained unchanged D-QCA detected a reduction in ITB (pre 148.17 +/- 154.03 mm3, post 112.86 +/- 117.82 mm3, p = 0.05). D-QCA appears as a useful approach to quantify IC thrombus volume, being more sensitive than TTG in assessing changes in ITB resulting from treatment strategies.

Quantitative coronary arteriography on digital flat-panel system.

On images acquired with a digital flat-panel (DFP) detector, known for its better image quality, the performance of a validated quantitative coronary arteriography (QCA) software, CAASII (Cardiovascular Angiography Analysis System or CAAS), and a DFP-dedicated QCA algorithm (flat-panel analysis software or FPAS) was compared in a phantom and a patient study. On phantom, FPAS performed with higher accuracy the quantification of the smallest tubes and the calibration of an empty catheter. The overall accuracy and precision for the quantification procedure was better for FPAS (0.07 +/- 0.04 mm) than for the CAAS (0.19 +/- 0.06 mm; P = 0.03 and P < 0.01, respectively). In the patient study, the main difference between the two algorithms was found in the small diameters: CAAS almost always gave higher values than FPAS for the minimal luminal diameter (P < 0.001) and could only give values up to 70% for diameter stenosis. In conclusion, the FPAS can be considered more appropriate for assessing severe stenoses on digital flat-panel images.

The HELP‐LDL‐apheresis multicentre study, an angiographically assessed trial on the role of LDL‐apheresis in the secondary prevention of coronary heart disease. II. Final evaluation of the effect of regular treatment on LDL‐cholesterol plasma concentrations and the course of coronary heart disease*

The efficacy of the heparin-induced extracorporeal LDL-precipitation (HELP)-apheresis procedure has been studied in an open prospective multicentre trial. After 2 years of regular weekly HELP-treatment the data from 39 of 51 patients could be evaluated according to the study criteria. Twelve of the initially recruited study patients were omitted from the evaluation either because of premature termination of the treatment or because they did not fulfil the exact guidelines of the study protocol. A mean of 2.831 plasma was regularly treated on average every 7.85 days. The mean pre-/post-apheresis LDL-cholesterol levels decreased from 286/121 mg dl-1 at the first HELP treatment to 203/77 mg dl-1 after 1 year and to 205/77 mg dl-1 after 2 years of regular apheresis; the corresponding values for fibrinogen were 314/144, 246/98 and 250/105 mg dl-1, respectively. In contrast, the mean pre-/post-apheresis HDL-cholesterol levels rose from 41/38 through 51/44 mg dl-1 after 1 year to 52/43 mg dl-1 after 2 years of treatment. The overall result was a normalization of the atherogenic index (LDL-/HDL-cholesterol ratio) from 6.9/3.2 to 4.0/1.9. The angiographies from 33 patients obtained before and after 2 years of regular treatment could be evaluated blindly using the cardiovascular angiography analysis system. The mean degree of stenosis of all segments decreased from 32.5% (SD = 16) to 30.6% (SD = 16.8) over the 2 years. A regression > 8% was observed in 50/187 (26.7%) segments, whereas 29/187 (15.5%) segments showed progression. In 108/187 (57.8%) segments the lesions were stable (< 8% deviation) over 2 years. We conclude that regular treatment with HELP-LDL-apheresis is able to stabilize progressive atherosclerotic disease and to induce almost twice as much regression as progression of atherosclerotic lesions.

Doppler flow velocity measurements during coronary angioplasty.

In addition to further studies using Doppler catheters to assess blood flow velocity during coronary angioplasty this study intends to evaluate the functional significance of coronary stenoses and to estimate their hemodynamic relevance prior to and after percutaneous transluminal coronary angioplasty (PTCA). Diameters of coronary artery stenoses were quantified by means of the cardiovascular angiographic analysis system (CAAS) both prior to and following successful PTCA in 37 patients. During coronary artery angioplasty a 12 M:Hz 0.018-in. Doppler-tipped guidewire was used to measure prestenotic and poststenotic parameters of coronary artery flow velocity both prior to and following PTCA. The minimal stenosis diameter was raised from 1.01 +/- 0.58 to 1.76 +/- 0.73 mm (P < 0.0001), the percent diameter stenosis decreased from 63 +/- 11 to 35 +/- 6% (P < 0.0001). Prestenotic average (APV) and maximum peak velocity (MPV), peak velocity integral (PVI), average systolic (ASPV) and diastolic (ADPV) peak velocity, systolic (SPVI) and diastolic (DPVI) peak velocity integral, and diastolic/systolic velocity ratio showed--in contrast to further studies--a considerably significant difference (P < 0.05), whereas poststenotic Doppler data (APV, MPV, PVI, ASPV, DSPV, SPVI, DPVI, DSVR) differed highly significantly (P < 0.0001) prior to and following PTCA. Prestenotic and poststenotic measurements of coronary artery flow velocity differed significantly before and after PTCA and offer the potential for estimating both the hemodynamic relevance of coronary artery stenoses and success of PTCA.

CAAS II: A second generation system for off‐line and on‐line quantitative coronary angiography

The Cardiovascular Angiography Analysis System (CAAS) has been completely redesigned and transferred to a modern platform. The user-friendly environment together with a number of image processing techniques and tools allow easy and fast analysis of cardiovascular angiographic images. These images are obtained either on-line by means of a frame grabber hooked on the video output of the X-ray equipment or off-line by digitising 35-mm cine film frames. In addition, images can be acquired more directly by means of a network link. Images stored on disk in different formats, including MS-DOS, can also be analysed. Accurate and reliable quantitative analysis of coronary stenoses and assessment of their related functional significance may offer the clinician a tool in a stratification of patients at risk. The semireal-time environment will make it possible for the cardiologist to quickly respond to the results of recanalisation procedures while the patient is still in the catheterisation laboratory. The addition of a video front end makes the system available to all clinically relevant X-ray imaging equipment. A detailed comparison with the former CAAS on the basis of analysis of 40 arterial segments in routinely acquired cineangiograms demonstrated no statistically significant differences between the two analysis systems. Repeated analysis of the same segments yielded inter- and intraobserver variabilities for the obstruction diameter of 0.096 and 0.108 mm, respectively. For the computed reference diameter the values are 0.099 and 0.096 mm, respectively, and for the percentage diameter stenosis 4.67 and 5.37%, respectively.

Radiological quality of coronary guiding catheters: a quantitative analysis.

Quantitative coronary angiography (QCA) is a validated and widely accepted method to investigate changes in arterial dimension over time. Calibration of measurements is enabled by the use of the coronary catheter as a scaling device. The dimensions and laminar composition of coronary catheters, however, have changed significantly over recent years and the suitability of the current generation of coronary catheters for calibration purposes has not been validated. We therefore recorded 57 coronary guiding catheters on cinefilm, and compared their automated quantitative measurements (Cardiovascular Angiography Analysis System, CAAS) with their true values (precision micrometer). We found an overall underestimation of quantitatively derived dimensions, ranging from -8.9 to +4% for water-filled catheters and from -15.5 to -3.9% for contrast-filled catheters. In conclusion, while the current generation of coronary guiding catheters shows a wide variety in radiological quality, it can be clearly detected by the CAAS system, and is suitable for calibration of QCA measurements (with the exception of the DVI atherectomy catheter), provided that calibration is done on contrast-empty catheters.

Quantification of intracoronary volume by videodensitometry: Validation study using fluid filling of human coronary casts

Changes in intracoronary volume reflect the hemodynamic significance of progression or regression of diffuse coronary artery disease where intracoronary catheters cannot be applied for direct measurements due to small vessel dimensions. We have validated the videodensitometric measurement of intracoronary volume with epoxy casts of postmortem human coronary arteries. The volume of 31 coronary segments (cross-sectional areas in a range of 2-13 mm2) measured by fluid-filling using a precision dispenser was compared with the respective single plane intracoronary volume assessments obtained by the videodensitometric algorithm of the new generation Cardiovascular Angiography Analysis System (CAAS II). The true and measured values of volume were compared by calculation of the mean of the signed differences +/- standard deviation and by linear regression analysis. Videodensitometric measurement of intracoronary volume correlate well with fluid-filling of human coronary artery casts (correlation coefficient: r = 0.99, y = 1.96 +/- 0.99x, standard error of estimate: SEE = 3.96) with a significant trend towards overestimation of true volume values (mean difference = 1.73 +/- 3.64 mm3, P < 0.05). Intracoronary volume estimations can be used to measure changes of luminal dimensions of coronary arteries and may offer a new approach to assessment of progression or regression of diffuse coronary artery disease.

Recoil following Wiktor stent implantation for restenotic lesions of coronary arteries.

The purpose of this study was to determine acute recoil of the vessel wall immediately after Wiktor stent implantation in native coronary arteries of 77 consecutive patients and to assess whether there was compression or "late recoil" of the stent itself at long-term follow-up. Furthermore, the relationship between recoil and a number of clinical, angiographic, and procedural variables was studied in addition to the relation between acute recoil renarrowing or restenosis was assessed. All angiograms were analyzed with the Cardiovascular Angiography Analysis System using automated edge detection. Acute recoil was defined by the difference between the mean diameter of the fully expanded balloon on which the stent was mounted and the mean diameter of the stented segment. Late recoil was calculated by comparing the mean diameter of the stent itself immediately after implantation and at follow-up without opacification of the vessel. Acute recoil amounted to 0.25 +/- 0.32 mm or 8.2%. Multivariate analysis identified sex (coefficient = -0.20, p = 0.04) and stent/artery ratio (coefficient = 0.99, p = 0.0001) as the only independent predictors of acute recoil. "Late recoil" of the stent itself was not observed. The overall difference between the mean diameter of the stent itself immediately after implantation and at follow-up was -0.15 +/- 0.33 mm, suggesting an overall increase in diameter of 5.0%. There was no relation between acute recoil and late restenosis. On the contrary, there was a trend towards a greater degree of recoil in patients without restenosis. Moreover, linear regression analysis disclosed a weak but negative correlation between acute recoil and a loss in minimal luminal diameter (coefficient: -0.55, p = 0.04). The Wiktor stent effectively scaffolds the instrumented vessel. Only a minimal amount of acute recoil was noted, which did not contribute to late luminal renarrowing or restenosis. In addition, no late compression of the stent itself was observed. These data suggest that tissue ingrowth into the lumen of the stented segment is the main cause of late luminal renarrowing after stent implantation.

Quantitative coronary angiography (QCA) in interventional cardiology: Clinical application of QCA measurements

Q UANTITATIVE coronary angiography (QCA) has had a tremendous impact in the field of interventional cardiology. Because of its superior accuracy and objectivity, QCA has supplanted visual and hand-held caliper assessments of coronary arteriograms and has improved interobserver and intraobserver variability. 1-3 QCA is now the gold standard for the assessment of the coronary tree in the context of scientific research, 4 although it has not yet gained widespread appeal for routine clinical use. 5 Until very recently, mainly because of the expense and time-consuming aspect involved in routine clinical application of sophisticated computer-based analysis, QCA has only been available for off-line use. 6-9 In addition, the extra precautions that must be taken by the angiographer in obtaining images suitable for quantitative analysis 1~ imply that many angiograms routinely performed by busy clinicians or in acute or emergency situations may not be analyzable by an automated computer-based system. 5 However, with the progressively increasing number of clinics involved in multicenter restenosis prevention trials in which QCA plays an integral role, 1H3 perhaps these extra precautions may become routine clinical practice. QCA has been particularly useful in interventional cardiology as the only objective and reliable means of assessing the immediate and long-term effects of coronary interventions. In particular, the phenomenon of restenosis has primarily been described and researched most extensively on the basis of sequential QCA studies. At the Thoraxcenter (Rotterdam, The Netherlands), we have been advocating the importance of QCA since the first report of its use by our group in 1978 TM and, subsequently, with renewed vigour after our initial experience with QCA in the assessment of coronary interventions, as reported in 1982.15 The Cardiovascular Angiographic Analysis System (CAAS) has been extensively and rigorously validated, 16-18 and technical aspects are presented in the accompanying report. The entire angiographic database now consists of collected information from more than 5,000 patients who have undergone several different forms of nonoperative coronary revascularization. The principles of QCA, which were initially designed for diagnostic studies of coronary artery disease (CAD), have necessarily been adapted to more complex situations related to either the presence of a device or the effect of an intervention on the angiographic appearance of a damaged vessel. The introduction of several newer devices in the past 7 years, has presented a number of unique and unforeseen problems in image analysis and the subsequent interpretation of important quantitative data, as described in the accompanying report. The emergence of digital subtraction angiography has allowed on-line performance of QCA measurements in the catheterization laboratory, so that a technique previously confined to research applications has been transformed into a powerful analytic tool, directly applicable to clinical decision making. 7,19 The immediate availability of QCA measurements during interventional procedures provides a unique opportunity for more accurate selection of appropriate interventional devices (eg, balloon, stent, or atherotome dimension) and for continuous monitoring and immediate evaluation of the result obtained. During the last 5 years at the Thoraxcenter, a large clinical experience has been accumulated through the application of the Philips Digital Cardiac Imaging (DCI) Automated Coronary Analysis System. 6,9 In vivo study of stenosis phantoms placed in porcine

Morphologic changes during follow-up after successful percutaneous transluminal coronary balloon angioplasty: Quantitative angiographic analysis in 778 lesions—further evidence for the restenosis paradox

The purpose of this study was to determine if there are any morphologic characteristics of lesions that renarrow (that is, restenotic lesions) following successful coronary balloon angioplasty that are different from their appearance pretreatment or from the appearance of nonrestenotic lesions that might provide some new insight into the restenosis phenomenon. The study population consisted of 653 patients (778 lesions) with 6 months of angiographic follow-up (94% angiographic follow-up rate) who were participating in the Multicenter European Research trial with Cilazapril after Angioplasty to prevent Transluminal coronary Obstruction and Restenosis (MERCATOR) study. Detailed quantitative angiographic measurements, including the mean diameter of the vessel segment (in millimeters) that was subjected to balloon dilation, were performed preangioplasty, postangioplasty, and at follow-up using the cardiovascular angiographic analysis system to provide some objective measurement of the actual extent of luminal changes in the months following coronary balloon angioplasty. Two different approaches for restenosis were used: (1) static criterion of >50% diameter stenosis at follow-up and (2) dynamic criteria of ≥0.40 or ≥0.72 mm change in minimal lumen diameter between postangioplasty and follow-up. Both approaches identified more severe stenosis to be a typical feature for restenotic lesions before angioplasty compared with nonrestenotic lesions. No differences were observed in lesion length, balloon-inflated vessel segment, or roughness index before angioplasty between the groups. Conflicting data were found for the amount of atherosclerotic plaque, symmetry index, and curvature index. The restenotic lesion at follow-up compared with its initial appearance gave conflicting results depending on which approach was used. The dynamic criteria illustrate that the reference diameter and the mean diameter of the entire segment dilated are reduced during follow-up. Two messages emerge from the study: (1) the restenosis process clearly involves the apparent normal vessel wall adjacent to the actual lesion, probably in response to the unavoidable injury caused by balloon dilatation and (2) the use of percentage diameter stenosis measurements depending on the assumptions of normality for a reference segment will therefore underestimate the true extent of the restenosis process and should be replaced in clinical angiographic studies by absolute luminal measurements.

Usefulness of repeat coronary angiography 24 hours after successful balloon angioplasty to evaluate early luminal deterioration and facilitate quantitative analysis

Because of the unavoidable occurrence of vessel disruption after successful coronary balloon angioplasty, the reliability of quantitative angiographic analysis in that setting has been questioned. For this reason and the suggested occurrence of delayed elastic recoil, repeat angiography at 24 hours has been advocated in clinical interventional trials. In this study, these issues are confronted by performing comprehensive quantitative analysis (Cardiovascular Angiographic Analysis System) of coronary angiograms, acquired in multiple identical projections immediately after and 24 hours after angioplasty, in 102 patients with 110 successfully dilated lesions. Vasomotion was controlled by intracoronary nitrate before angiography and all patients were fully anticoagulated (activated partial thromboplastin time 85 to 120 seconds) for >24 hours. Paired Student's (tests applied to angiographic measurements revealed that there was no significant deterioration in minimal luminal diameter or cross-sectional area from immediately after angioplasty to 24 hours later. It can thus be inferred that there is no phenomenon of delayed elastic recoil, at least during this time period. Measurement accuracy and precision of the Cardiovascular Angiographic Analysis System from the postangioplasty angiogram are highly acceptable, at < 0.01 and ± 0.20 mm, respectively. Therefore, it is concluded that routine repeat 24-hour angiography is not indicated after successful angioplasty. A highly significant increase (p < 0.001) in reference diameter (+0.11 ± 0.18 mm) was responsible for the apparent increase in percent diameter stenosis (2.4 ± 7%), a finding that demonstrates the potential for error by selective application of percent diameter stenosis measurements atone. Preferential use of absolute luminal measurements is thus strongly recommended for clinical trials with angiographic monitoring.

Experimental validation of geometric and densitometric coronary measurements on the new generation cardiovascular angiography analysis system (caas ii)

Computer-assisted contour detection and videodensitometric cross sectional area assessment of coronary artery obstructions on the CAAS II system were validated in vitro and in vivo by angiographic cinefilm recording and automated measurement of stenosis phantoms (luminal diameter 0.5, 0.7, 1.0, 1.4, 1.9 mm) which were first inserted in a plexiglass model and then serially implanted in swine coronary arteries. "Obstruction diameter" (OD) and "obstruction area" (OA) values obtained from 10 in vitro and 19 in vivo images at the site of the artificial stenoses were compared with the true phantom dimensions. The in vitro assessment of OD yielded an accuracy of 0.00 +/- 0.11 mm (correlation coefficient: r = 0.98, y = 0.18 + 0.82x, standard error of estimate: SEE = 0.08), whereas the in vivo measurement of OD gave an accuracy of -0.01 +/- 0.18 mm (r = 0.94, y = 0.22 + 0.82x, SEE = 0.15). The assessment of OA gave an accuracy of -0.08 +/- 0.21 mm2 in vitro (r = 0.97, y = 0.08 + 0.99x, SEE = 0.22) and -0.22 +/- 0.32 mm2 in vivo (r = 0.95, y = 0.21 + 1.01x, SEE = 0.33). The mean reproducibility was +/- 0.09 mm for geometric measurements and +/- 0.21 mm2 for videodensitometric assessments, respectively. Thus, due to inherent limitations of the imaging chain, the reliability of geometric coronary measurements is still far superior to videodensitometric assessments of vessel cross sectional areas.

Visual versus quantitative assessment of the severity of coronary artery stenoses: Can the angiographer's eye be reeducated?

The percent reduction of intraluminal diameter of 102 coronary stenoses before ( n = 26), immediately after ( n = 24), and 6 months after ( n = 52) coronary balloon angioplasty as assessed by two observers experienced in quantitative coronary angiography and by automated measurement by means of the Cardiovascular Angiographic Analysis System (CAAS) was compared. Two hundred twenty-seven still frames were selected for analysis by CAAS and displayed for assessment by each of the observers, who were unaware of CAAS results. Comparisons with CAAS measurements were made for all still frames (“per view” analyses) and for each coronary stenosis after averaging the values obtained for a given coronary segment (“per stenosis” analyses). Intraobserver variability was tested on 21 still frames from 10 stenoses, assessed 6 weeks apart by one observer. Intraobserver variability was 5% ( r = 0.98); interobserver variability was 6% ( r = 0.94). Per view analyses showed that observer measurements correlated well with CAAS measurements ( r = 0.89 and r = 0.90); the accuracy was −0.9% and −0.7% for observers 1 and 2, and the precision was 9% and 8%, respectively; for per stenosis analyses, the accuracy was −0.5% and −0.8% ( r = 0.92 and 0.94) and the precision 7% and 6%, respectively. There was no difference in the accuracy and precision of visual assessment for lesions with 〈50%- or 〉50%-diameter stenoses. The occurrence of restenosis was likewise detected visually with a high sensitivity and specificity compared with CAAS. Visual assessment of coronary obstructions by observers trained in quantitative coronary angiography techniques can yield measurement accuracy and precision of sufficient standard for clinical practice and may be applicable in some clinical angiographic studies.

Matching based on quantitative coronary angiography as a surrogate for randomized studies: Comparison between stent implantation and balloon angioplasty of native coronary artery lesions

Although intracoronary stenting has been advocated as an adjunct to balloon angioplasty to circumvent late restenosis, its effectiveness has not yet been verified. Therefore the aim of this study was to determine the differences in the immediate and long-term changes in stenosis geometry between Wallstent implantation and balloon angioplasty in native coronary artery lesions. To obtain two study populations with identical baseline stenosis characteristics, patients were matched for lesion site, vessel size, and minimal luminal diameter. Only patients undergoing elective and successful coronary intervention of a native coronary artery, in whom a control angiographic study had been performed, were included. A total of 186 patients (93 in each group) were selected. The coronary angiograms were analyzed with the computer-assisted cardiovascular angiographic analysis system. Matching was considered adequate, since there was an equal number of lesion sites in each study population and there were no differences in baseline reference diameter and minimal luminal diameter. Wallstent implantation resulted in a significantly greater increase in minimal luminal diameter (from 1.22 ± 0.34 mm to 2.49 ± 0.40 mm, p < 0.00001) compared with balloon angioplasty (from 1.21 ± 0.29 mm to 1.92 ± 0.35 mm, p < 0.00001). Despite a greater decrease in minimal luminal diameter after Wallstent implantation (0.48 ± 0.74 mm) than after balloon angioplasty (0.20 ± 0.46 mm), the minimal luminal diameter at follow-up was significantly greater after stent implantation (2.01 ± 0.75 mm vs 1.72 ± 0.54, p < 0.0001). It was concluded that Wallstent implantation results in a superior immediate and long-term increase in minimal luminal diameter compared with balloon angioplasty. The larger initial gain after stent implantation compensates for the late loss, and thus an improved initial result and not lessened neointimal hyperplasia is responsible for a reduced incidence of restenosis. Studies based on matching of angiographic variables are a surrogate for randomized studies, forecasting their results and offering insight into the effects of different interventional techniques. Moreover, these studies yield statistical information that may be helpful for the proper design of a randomized study (sample size, type II error).

In-vivo validation of on-line and off-line geometric coronary measurements using insertion of stenosis phantoms in porcine coronary arteries.

Geometric coronary artery measurements with the Phillips Digital Cardiac Imaging System (DCI) and the Cardiovascular Angiography Analysis System (CAAS) were validated using percutaneous insertion of radiolucent stenosis phantoms in swine coronary arteries. Angiographic visualization of the stenosis lumens (phi 0.5, 0.7, 1.0, 1.4, 1.9 mm) was simultaneously recorded on DCI and cinefilm. The acquisition systems were calibrated by either the diameter of the guiding catheter (catheter CAL) or the isocenter method (isocenter CAL). Minimal luminal diameters (MLD) obtained with CAAS and DCI on 20 corresponding cineframes were compared with the true phantom diameters (PD). The accuracy of MLD measurements with the CAAS using isocenter CAL was -0.07mm, the precision 0.21 mm (r = 0.91; y = 0.30 + 0.79x; SEE = 0.19), with catheter CAL the accuracy was 0.09 mm, the precision 0.23 mm (r = 0.89; y = 0.19 + 0.74x; SEE = 0.19). The accuracy of MLD measurements using the DCI with isocenter CAL was 0.08 mm, the precision 0.15 min (r = 0.96; y = 0.08 + 0.86x; SEE = 0.14), with catheter CAL the accuracy was 0.18 mm, the precision 0.21 mm (r = 0.92; y = 0.09 + 0.76x; SEE = 0.17). DCI underestimated PD with isocenter CAL (p less than 0.05) and with catheter CAL (p less than 0.001). MLD can be measured with high accuracy, both applying on-line digital as well as off-line cineangiographic analysis. The results of digital measurements demonstrate high reliability of the new digital software package.

A comparison of two methods to measure coronary flow reserve in the setting of coronary angioplasty: intracoronary blood flow velocity measurements with a Doppler catheter, and digital subtraction cineangiography

Intracoronary blood flow velocity measurements with a Doppler balloon catheter and the radiographic assessment of myocardial perfusion with contrast media, before and after the intracoronary administration of papaverine, have previously been used to investigate regional coronary flow reserve. In the present study we applied both techniques in 21 patients to measure coronary flow reserve in the setting of coronary angioplasty. Pre-angioplasty (N = 14) and post-angioplasty (N = 19) measurements of coronary flow reserve were obtained by digital subtraction cineangiography in the myocardial region supplied by the dilated coronary artery, and with the Doppler probe in the proximal part of the dilated vessel. The reactive hyperaemia following the final balloon inflation was recorded with the Doppler balloon catheter still positioned across the stenotic lesion. Coronary stenosis geometry was quantified with the Cardiovascular Angiography Analysis System. When the epicardial stenosis was the only factor causing a reduction in coronary flow reserve, flow reserve measured with both digital subtraction cineangiography and with the Doppler probe correlated well with the cross-sectional area at the site of obstruction, r = 0.88, SEE = 0.36 and r = 0.77, SEE = 0.45 respectively. In contrast, when other factors decreasing coronary flow reserve were present (intimal dissection, left ventricular hypertrophy, previous myocardial infarction, collaterals) measurements obtained with both techniques correlated poorly with cross-sectional area (r = 0.55, SEE = 0.57, and r = 0.59, SEE = 0.50). Flow reserve measurements obtained with digital subtraction cineangiography correlated well with the measurements obtained with the Doppler probe (r = 0.85, SEE = 0.38, and r = 0.87, SEE = 0.34), although the two approaches have methodologically nothing in common and their respective regions of interest (myocardium for the radiographic technique and intracoronary lumen for the Doppler technique) are basically different. Furthermore, the reactive hyperaemia following the final balloon inflation was related to the flow reserve measured with both the angiographic technique (r = 0.85, SEE = 0.34) and the Doppler technique (r = 0.83, SEE = 0.32) using pharmacologically induced coronary vasodilation with intracoronary papaverine. This suggests that the same quantity of coronary flow reserve that can be recruited pharmacologically can be recruited by ischaemia following a transluminal occlusion.

How critical is frame selection in quantitative coronary angiographic studies?

To analyse quantitatively a coronary arterial segment from a cineangiogram, an end-diastolic or neighbouring frame is usually selected. However, different cardiologists may select other (although usually neighbouring) frames, even when the same selection criteria are followed. It is also possible that the frames are selected from different cardiac cycles. In this study the effects of such phase shifts on the reproducibility of the quantitative measurements were studied. In a total of 38 consecutive patient films obtained at a filmspeed of 25 frames s-1, the frame phi demonstrating the severity of a lesion optimally as judged by a senior cardiologist, the three preceding frames, the three following frames and one frame exactly one cycle prior to or following frame phi were selected; frame phi was always chosen in the end-diastolic phase of the cardiac cycle. In each film one coronary arterial segment with a focal lesion was analysed quantitatively in these total of 8 frames with the Cardiovascular Angiography Analysis System (CAAS). No significant differences were found in the mean difference and the standard deviations of the differences (variabilities) in the obstruction diameter, interpolated reference diameter, percent diameter stenosis, extent of the obstruction and area of atherosclerotic plaque obtained in the various frames with respect to frame phi. Therefore, it may be concluded that the selection of a cineframe for quantitative analysis in the end-diastolic phase of the cardiac cycle is not very critical.(ABSTRACT TRUNCATED AT 250 WORDS)