Quantitative computer techniques for analyzing coronary arteriograms

Antihypertensive therapy and regression of coronary artery disease: insights from the Comparison of Amlodipine versus Enalapril to Limit Occurrences of Thrombosis (CAMELOT) and Norvasc for Regression of Manifest Atherosclerotic Lesions by Intravascular Sonographic Evaluation (NORMALISE) trials

BACKGROUND

In patients with coronary artery disease (CAD), therapies designed to prevent clinical events are not always associated with significant reduction in coronary obstruction, as measured by quantitative coronary angiography. We set out to explore the relationship between quantitative coronary angiography parameters, baseline characteristics, and clinical events in a large trial of CAD regression with antihypertensive agents.

METHODS AND RESULTS

Patients randomized to amlodipine, enalapril, or placebo in the CAMELOT trial were followed for 24 months for major ischemic events. Among 431 patients participating in the angiographic and intravascular ultrasound substudy NORMALISE, 298 (99 amlodipine, 96 enalapril, and 103 placebo) had complete angiographic and intravascular ultrasound data. The patients did not differ significantly with respect to baseline characteristics (except for diabetes) or extent of CAD. After 24 months, the change in minimal lumen diameter (MLD) was -0.02 +/- 0.13 for amlodipine, -0.03 +/- 0.12 for enalapril, and -0.03 +/- 0.17 mm for placebo (P = .40). Major ischemic events occurred in 20.2%, 24%, and 25.2%, respectively (P = .68). There was no significant correlation between change in MLD and age, sex, statin therapy, or systolic blood pressure at baseline. The change in MLD did not differ in patients with and without cardiovascular events, regardless of treatment assignment (P = .54). Only the extent of CAD was independently predictive of ischemic events.

CONCLUSION

As compared to placebo, amlodipine treatment resulted in fewer ischemic events after 24 months of therapy, but the clinical benefit was not associated with a commensurate improvement in arterial lumen dimensions.

Thematic review series: Patient-Oriented Research. Imaging atherosclerosis: state of the art

The ability to image obstructive arterial disease brought about a revolution in clinical cardiovascular care; the development of newer technologies that image arterial wall thicknesses, areas, volumes, and composition allows valid imaging of atherosclerosis for the first time. Development of noninvasive imaging of atherosclerosis has further led to a quantum shift in research in the field by enabling the study of asymptomatic populations and thus allowing investigators to focus on preclinical disease without the many biases associated with the study of symptomatic patients. These noninvasive investigations have broad implications for clinical care as well. Coronary angiography, computed tomographic (CT) imaging of coronary calcium, intravascular ultrasound, multidetector CT angiography, B mode ultrasound of the carotid arteries, and MRI of the carotid arteries all have unique strengths and weaknesses for imaging atherosclerosis. Certain of these techniques are extremely useful as outcome variables for clinical trials, and others are uniquely useful as predictors of the risk of cardiovascular disease. All are informative in one way or another with regard to the role of plaque remodeling and composition in disease causation. CT and MRI technology are advancing very rapidly, and research and clinical uses of these imaging modalities promise to further advance our understanding of atherosclerosis and its prevention.

"Vulnerable plaques" — ticking of the time bomb

Atherosclerosis and its sequelae are one of the leading causes of morbidity and mortality, especially in the developed nations. Over the years, treatment protocols have changed with the changing understanding of the disease process. Inflammatory mechanisms have emerged as key players in the formation of the atherosclerotic plaque. For the majority of its life span, the plaque develops silently and only some exhibit overt clinical manifestations. The purpose of this review is to examine the inherent properties of some of these "vulnerable" or symptomatic plaques. Rupture of the plaque is related to the thickness of the fibrous cap overlying the necrotic lipid core. A thin cap is more likely to lead to rupture. Multiple factors broadly grouped as the "determinants of vulnerability" are responsible for directly or indirectly influencing the plaque dynamics. Apoptosis is considered an important underlying mechanism that contributes to plaque instability. Inflammatory reactions within the plaque trigger apoptosis by cell–cell contact and intra cellular death signaling. Once started, the apoptotic process affects all of the components that make up the plaque, including vascular smooth muscle cells, endothelial cells, and macrophages. Extensive research has identified many of the key cellular and molecular regulators that play a part in apoptosis within the atherosclerotic lesion. This information will help us to gain a better understanding of the underlying mechanisms at the cellular and molecular level and enable us to formulate better therapeutic strategies to combat this disease.Key words: apoptosis, atherosclerosis, inflammation, plaque stability, vulnerable plaques.

Adaptive edge localisation approach for quantitative coronary analysis

Lack of reliability, user dissatisfaction and errors in determining coronary vessel wall characteristics are challenging issues in quantitative coronary analysis (QCA). A new approach is proposed for QCA that tackles these issues. The proposed approach extracts the coronary vessel edges by applying dynamic programming techniques that use human-based decision criteria, adaptive edge detection and feature-based cost minimisation. This approach uses image gradient, image intensity, boundary continuity and adaptive thresholding to gain maximum quality assurance. The validation of this approach was conducted through modelled phantoms and real X-ray angiograms. The results show that the accuracies obtained were 0.0116mm and 0.06mm, respectively, and the precisions were 0.0263mm, and 0.04mm, respectively. The proposed approach is reliable, reproducible and user friendly and provides high precision compared with recently published results. Furthermore, the significance of the proposed approach and its limitations are also discussed.

Estimation of the supplementary axial wall stress generated at peak flow by an arterial stenosis

Mechanical stresses in arterial walls are known to be implicated in the development of atherosclerosis. While shear stress and circumferential stress have received a lot of attention, axial stress has not. Yet, stenoses can be intuitively expected to produce a supplementary axial stress during flow systole in the region immediately proximal to the constriction cone. In this paper, a model for the estimation of this effect is presented, and ten numerical examples are computed. These examples show that the cyclic increase in axial stress can be quite considerable in severe stenoses (typically 120% or more of the normal stress value). This result is in best agreement with the known mechanical or morphological risk factors of stenosis progression and restenosis (hypertension, elevated pulse pressure, degree of stenosis, stenosis geometry, residual stenosis, etc). The supplementary axial stress generated by a stenosis might create the damages in the endothelium and in the elastic membranes which potentiate the action of the other risk factors (hyperlipidaemia, diabetes, etc). It could thus be an important cause of stenosis progression and of restenosis.

Simvastatin and niacin, antioxidant vitamins, or the combination for the prevention of coronary disease

BACKGROUND

Both lipid-modifying therapy and antioxidant vitamins are thought to have benefit in patients with coronary disease. We studied simvastatin-niacin and antioxidant-vitamin therapy, alone and together, for cardiovascular protection in patients with coronary disease and low plasma levels of HDL.

METHODS

In a three-year, double-blind trial, 160 patients with coronary disease, low HDL cholesterol levels and normal LDL cholesterol levels were randomly assigned to receive one of four regimens: simvastatin plus niacin, vitamins, simvastatin-niacin plus antioxidants; or placebos. The end points were arteriographic evidence of a change in coronary stenosis and the occurrence of a first cardiovascular event (death, myocardial infarction, stroke, or revascularization).

RESULTS

The mean levels of LDL and HDL cholesterol were unaltered in the antioxidant group and the placebo group; these levels changed substantially (by -42 percent and +26 percent, respectively) in the simvastatin-niacin group. The protective increase in HDL2 with simvastatin plus niacin was attenuated by concurrent therapy with antioxidants. The average stenosis progressed by 3.9 percent with placebos, 1.8 percent with antioxidants (P=0.16 for the comparison with the placebo group), and 0.7 percent with simvastatin-niacin plus antioxidants (P=0.004) and regressed by 0.4 percent with simvastatin-niacin alone (P<0.001). The frequency of the clinical end point was 24 percent with placebos; 3 percent with simvastatin-niacin alone; 21 percent in the antioxidant-therapy group; and 14 percent in the simvastatin-niacin-plus-antioxidants group.

CONCLUSIONS

Simvastatin plus niacin provides marked clinical and angiographically measurable benefits in patients with coronary disease and low HDL levels. The use of antioxidant vitamins in this setting must be questioned.

Intracoronary thrombus and platelet glycoprotein IIb/IIIa receptor blockade with tirofiban in unstable angina or non-Q-wave myocardial infarction. Angiographic results from the PRISM-PLUS trial (Platelet receptor inhibition for ischemic syndrome management in patients limited by unstable signs and symptoms). PRISM-PLUS Investigators

BACKGROUND

The present study describes the effects of tirofiban, a nonpeptide platelet glycoprotein (GP) IIb/IIIa receptor blocker, on the characteristics of culprit lesions in patients with unstable angina (UA) or non-Q-wave myocardial infarction (NQWMI).

METHODS AND RESULTS

Of 1915 patients enrolled in PRISM-PLUS, 1491 had a readable film obtained a median of 65 hours after randomization. A core laboratory examined the culprit lesions for intracoronary thrombus burden (primary end point) and for TIMI flow grade distribution and severity of the obstruction and of underlying coronary artery disease (secondary end points). The combination of tirofiban plus heparin compared with heparin alone significantly reduced the intracoronary thrombus burden of the culprit lesions (OR=0.77, P=0.022), improved the perfusion grade (OR=0.65, P=0.002), and decreased the severity of the obstruction (P=0.037), but it did not influence the severity of the underlying plaque. Persistence of a thrombus in 45% of patients was associated with a 2.4-fold increase in the odds of death at 30 days (P=0.005) and a 2-fold increase in the odds of myocardial infarction (P=0.002).

CONCLUSIONS

The addition of tirofiban to heparin reduced the thrombus burden of the culprit lesion and improved distal perfusion in patients with UA or NQWMI, which supports the clinical benefit observed with the combination treatment.

Intravascular imaging and physiologic lesion assessment to define critical coronary stenoses

Despite the fact that the coronary angiogram is the gold-standard in assessing a coronary artery stenosis for the purposes of clinical decision making, it has many limitations. Alternative methods are available. This article discusses three of these: intravascular ultrasound, coronary flow reserve, and fractional flow reserve.

[Reliability of digital coronary quantification in a hemodynamic laboratory. Comparison with a film-based system]

BACKGROUND AND OBJECTIVES

Quantitative coronary angiography can be performed in two ways: on-line during catheterism, and off-line once the procedure is finished. Consequently, several studies have been published comparing both systems. Nevertheless, none of them has compared the measurements made off-line with those acquired on-line by the hemodynamist in charge of procedure. The objective of this study was to compare the measurements made on-line by the hemodynamist involved in the procedure with a digital system (DCI) with those obtained off-line by an independent and alien observer to the procedure by using film-based system (CMS).

MATERIAL AND METHODS

Forty coronary lesions suitable for quantification were measured in a prospective fashion. They came from follow-up angiograms. Either balloon or stent were used in the previous angioplasty. Stenoses were assessed on-line and off-line by using the most severe view as judged by the hemodynamist.

RESULTS

No significant differences were found for obstruction diameter, reference diameter nor percent diameter stenosis. Pearson's correlation coefficient values (r), intraclass correlation coefficient (ri), regression line equation and mean of signed differences with their standard deviations are showed: a) obstruction diameter: r = 0.83, ri = 0.83, DCI = 0.42 + 0.76 x CMS, -0.01 +/- 0.42 mm; b) reference diameter: r = 0.72, ri = 0.69, DCI = 1.29 + 0.61 x CMS, 0.003 +/- 0.38 mm, y c) percent diameter stenosis: r = 0.86, ri = 0.86, DCI = 10.05 + 0.77 x CMS, 1.19 +/- 10.75%.

CONCLUSIONS

We attained good concordance between both quantification systems under clinical conditions. In our opinion these results support the use of on-line quantification as a reliable tool for clinical decision making in the catheterization laboratory.

Quantitative coronary angiography with deformable spline models

Although current edge-following schemes can be very efficient in determining coronary boundaries, they may fail when the feature to be followed is disconnected (and the scheme is unable to bridge the discontinuity) or branch points exist where the best path to follow is indeterminate. In this paper, we present new deformable spline algorithms for determining vessel boundaries, and enhancing their centerline features. A bank of even and odd S-Gabor filter pairs of different orientations are convolved with vascular images in order to create an external snake energy field. Each filter pair will give maximum response to the segment of vessel having the same orientation as the filters. The resulting responses across filters of different orientations are combined to create an external energy field for snake optimization. Vessels are represented by B-Spline snakes, and are optimized on filter outputs with dynamic programming. The points of minimal constriction and the percent-diameter stenosis are determined from a computed vessel centerline. The system has been statistically validated using fixed stenosis and flexible-tube phantoms. It has also been validated on 20 coronary lesions with two independent operators, and has been tested for interoperator and intraoperator variability and reproducibility. The system has been found to be specially robust in complex images involving vessel branchings and incomplete contrast filling.

Validation of coronary artery saphenous vein bypass graft diameter measurements using quantitative angiography

The accepted value for reproducibility (true change) is two standard deviations (SD) of the differences between repeat measurements. It has been well established for coronary artery measurements using several different quantitative coronary angiography (QCA) systems, but it has not been well documented for saphenous vein grafts (SVG). The purpose of this study was to assess, using the Cardiovascular Measurement System (CMS), the measurement reproducibility of 24 vein grafts from 24 patients who had symptom-directed control angiography. Three equal graft segments were studied separately. Focal narrowings expressed in percent stenosis varied from 5 to 80% (mean 20.8 +/- 15.9%). The average minimum lumen diameter (MLD) was 3.07 +/- 0.81 mm and the average interpolated reference diameter (Ref. D) was 3.87 +/- 0.58 mm. We assessed the reproducibility of measurements obtained from two separate imagings of the graft in the same view but at least 20 minutes apart, near the beginning and at the end of the angiographic procedure (simulating baseline and end-trial examinations). The SD for differences in measurements (variability) was 0.183 mm for the MLD, 0.193 mm for the Ref.D, 0.184 mm for the mean diameter (Mean D) and 3.72% for the percent diameter stenosis (PDS). A reasonable true change cut-off for SVG measurements in our laboratory is > or = 0.4 mm for the minimum and mean lumen diameters, and > or = 10% for the PDS, when QCA is obtained with the QCA-CMS analytical software package.

Assessment of blood flow distal to coronary artery stenoses. Correlations between myocardial positron emission tomography and poststenotic intracoronary Doppler flow reserve

BACKGROUND

Previous studies have correlated quantitative coronary angiographic stenosis severity with positron emission tomography (PET) myocardial perfusion and proximal measurements of intracoronary flow velocities in normal and diseased coronary arteries. The aim of this study was to correlate regional myocardial blood flow (RMBF) derived from [15O]H2O PET with directly measured poststenotic intracoronary Doppler flow velocity data acquired under basal conditions and dipyridamole-induced hyperemia.

METHODS AND RESULTS

Eleven consecutive patients 53 +/- 13 years old with ischemic chest pain and isolated proximal left coronary artery stenoses (left anterior descending, 9; left circumflex, 2; mean, 59 +/- 23% diameter stenosis) underwent [15O]H2O myocardial PET and intracoronary Doppler flow velocity studies within 1 week. PET RMBF (mL.g-1.min-1) and myocardial perfusion reserve (MPR) were calculated in poststenotic and normal reference vascular beds. Poststenotic Doppler average peak flow velocities (APV; cm/s) and coronary flow velocity reserve (CFR) were compared with corresponding PET data and quantitative angiographic lesional parameters. PET RMBF and Doppler APV were linearly correlated (r = .60; P < .001), as were poststenotic PET MPR and Doppler CFR (r = .76; P < .0002). Relative coronary flow velocity and MPR ratios between poststenotic and angiographically normal vascular beds were comparably reduced (0.83 +/- 0.25 versus 0.86 +/- 0.21, respectively; P = NS).

CONCLUSIONS

Intracoronary Doppler flow velocities acquired distal to isolated left coronary artery stenoses correlated with [15O]H2O PET regional myocardial perfusion and are useful for assessment of the physiological significance of coronary stenoses in humans.

Use of intravascular ultrasound for in vivo assessment of changes in intimal thickness of angiographically normal saphenous vein grafts one year after aortocoronary bypass surgery

OBJECTIVE

To use intravascular ultrasound in vivo to evaluate changes in the intimal thickness of angiographically normal saphenous vein grafts one year after implantation.

DESIGN

Fifteen saphenous vein grafts in 12 patients were examined one month and 12 months after aortocoronary bypass graft surgery with intravascular ultrasound using a 30 MHz transducer. None of the grafts examined showed any angiographic abnormalities. The intimal thickness and intimal area of the graft in the proximal portion were measured on intravascular ultrasound images obtained one month and 12 months after operation.

SETTING

General hospital.

PATIENTS

Twelve patients who underwent aortocoronary bypass graft surgery.

RESULTS

The ultrasound images showed a thin-walled graft with a thin intima one month after operation (mean (SD)) (0.31 (0.09) mm). The intimal thickness of the graft increased significantly to 0.65 (0.08) mm (P < 0.001) 12 months after operation. The intimal area of the graft was 0.90 (0.80) mm2 one month after operation. 12 months after operation the intimal area had increased significantly to 5.26 (1.38) mm2 (P < 0.001).

CONCLUSION

Intravascular ultrasound in vivo showed that one year after implantation angiographically normal saphenous vein grafts had a thicker intima than one month after implantation.

LDL-Apheresis Atherosclerosis Regression Study (LAARS). Effect of aggressive versus conventional lipid lowering treatment on coronary atherosclerosis

BACKGROUND

Intensive lipid lowering may retard the progression of coronary atherosclerosis. LDL-apheresis has the potential to decrease LDL cholesterol to very low levels. To assess the effect of more aggressive lipid lowering with LDL-apheresis, we set up a randomized study in men with hypercholesterolemia and severe coronary atherosclerosis.

METHODS AND RESULTS

For 2 years, 42 men were treated with either biweekly LDL-apheresis plus medication or medication alone. In both groups a dose of simvistatin of 40 mg per day was administered. Baseline (mean+/-SD) LDL cholesterol was 7.8+/-1.9 mmol x L(-1) and 7.9+/-2.3 mmol x L(-1) in the apheresis and medication groups, respectively. The mean reduction in LDL cholesterol was 63% (to 3.0 mmol x L(-1)) and 47% (to 4.1 mmol x L(-1)), respectively. Primary quantitative coronary angiographic end points were changes in average mean segment diameter and minimal obstruction diameter. No differences between the apheresis and medication groups were found in mean segment diameter (-0.01+/-0.16 mm versus 0.03+/-0.16 mm, respectively) or in minimal obstruction diameter (0.01+/-0.13 mm versus 0.01+/-0.11 mm, respectively), expressed as means per patient. On the basis of coronary segment, mean percent stenosis of all lesions showed a tendency to decrease; only in the apheresis group more minor lesions disappeared in comparison to the medication group. On bicycle exercise tests, the time to 0.1 mV ST-segment depression increased significantly by 39% and the maximum level of ST depression decreased significantly by 0.07 mV in the apheresis group versus no changes in the medication group.

CONCLUSIONS

Two years of lipid lowering both with medication alone or LDL-apheresis with medication showed angiographic arrest of the progression of coronary artery disease. However, more aggressive treatment induced functional improvement, which may precede anatomic changes.

Value of visual versus central quantitative measurements of angiographic success after percutaneous transluminal coronary angioplasty. NHLBI PTCA Registry Investigators

This study examined the optimal angiographic definition for long-term success after angioplasty and compared visual and quantitative angiographic measurements in assessing outcome. The National Heart, Lung, and Blood Institutes--Percutaneous Transluminal Coronary Angioplasty Registry prospectively followed 1,768 patients from 15 clinical centers. Symptom-free survival, defined as survival without angina, myocardial infarction, bypass surgery, or death, occurred in 59% of patients. In a subset of 393 patients, quantitative coronary angiography (QCA), done at a core angiographic laboratory, was compared with visual site readings. Although there was considerably more variability for visual readings, a site reading of a change in percent stenosis of >20% correlated highly with symptom-free survival (64.6% for patients who had all lesions successfully dilated, 48% for patients with partial success, and only 21% for patients without angiographic success; p < 0.001). Similar findings were seen for other angiographic definitions, but a change of > 20% was most discriminatory. In contrast, QCA readings had little or no predictive value. This study confirms that visual assessment of the immediate change in percent stenosis is predictive of a successful 1-year outcome. A change of greater than 20% is most discriminatory and should still be used to define angiographic success. QCA does not appear to be superior to visual assessment in predicting 1-year outcome.

Variability in measurement of extracranial internal carotid artery stenosis as displayed by both digital subtraction and magnetic resonance angiography: an assessment of three caliper techniques and visual impression of stenosis

BACKGROUND AND PURPOSE

The degree of stenosis in the extracranial internal carotid artery helps predict the risk of an individual suffering subsequent cerebrovascular ischemic events. Different techniques have evolved to measure stenosis from angiograms, leading to some confusion and a call for the adoption of a single technique. To help choose the most reliable technique, this study assessed observer variability in reporting carotid stenosis for four different techniques, from both digital subtraction (DSA) and MR angiograms (MRA). Three of the techniques used caliper measurements; the fourth was the visual impression of stenosis.

METHODS

From a total of 137 angiograms, caliper measurements were possible on 105 DSAs and 74 MRAs. Measurements from these angiograms were made by two independent observers on two separate occasions to assess interobserver and intraobserver variation in reporting.

RESULTS

For DSA, the variability in reporting and the number of clinically significant differences arising as a result were similar for each of the four techniques. While the typical measurement errors for each of the techniques studied were on the order of +/- 5%, each technique produced some sizable individual differences for the same angiogram, with resultant wide 95% limits of agreement. Observer variability for reporting MRA was generally a little greater than for DSA. Compared with the caliper techniques, the visual impression of stenosis technique performed well, particularly for MRA.

CONCLUSIONS

Although observer variability in reporting can be considerable, no important differences were found among the different techniques widely used for measuring carotid stenosis.

Variability in estimation of coronary dimensions from 6F and 8F catheters

To investigate the suitability of diagnostic 6F catheters for coronary angiographic measures in the clinical setting, we determined the relative accuracy and reproducibility of the measures obtained with these catheters as scaling devices in 59 stenoses. Comparison was made with duplicate injections, obtained before angioplasty, using an 8F guiding catheter as scaling device. Intra- and interobserver variability was evaluated in 15 stenoses. The coefficient of variation averaged 18.3% for the minimal lumen diameter, 10.4% for the percent stenosis, and only 7.4% for the reference diameter. Reproducibility of angiographic measures done with the 6F catheter was similar to that obtained with the 8F catheter, although accuracy was lower with the 6F for the measurement of reference diameter. Thus, quantitative coronary angiography (QCA) measures derived from routine diagnostic angiograms may be suitable for determination of reference diameter, allowing enough precision for determination of the size of a coronary device for intervention, but these measures may lack accuracy for precise determination of minimum diameter and percent stenosis, making their use questionable in studies looking at individual changes in coronary stenosis dimensions.

In-vivo validation of videodensitometric coronary cross-sectional area measurement using dual-energy digital subtraction angiography

Previous studies indicate that conventional geometric edge detection techniques, used in quantitative coronary arteriography (QCA), have significant limitations in quantitating coronary cross-sectional area of small diameter (D) vessels (D < 1.00 mm) and lesions with complex cross-section. As a solution to this problem, we have previously reported on an in-vitro validation of a videodensitometric technique that quantitates the absolute cross-sectional area including small vessel diameter (D < 1.00 mm) and any complex shape of the vessel cross-section. For in-vivo validation, plastic tubing (5-8 mm long) with different shape complex cross-section with known cross-sectional area (A = 0.8-4.5 mm2) were percutaneously wedged in the coronary arteries of anesthetized pigs (40-50 kg). Contrast material injections (6-10 ml at 2-4 ml/sec) were made into the left main coronary artery during image acquisition using a motion immune dual-energy subtraction technique, where low and high X-ray energy and filtration were switched at 30 Hz. A comparison was made between the actual and measured cross-sectional area using the videodensitometry and edge detection techniques in tissue suppressed energy subtracted images. In eighteen comparisons the videodensitometry technique produced significantly improved results (slope = 0.87, intercept = 0.24 mm2, r = 0.94) when compared to the edge detection technique (slope = 0.42, intercept = 1.99 mm2, r = 0.39). Also, a cylindrical vessel phantom (D = 1.00-4.75 mm) was used to test the ability to calculate and correct for the effect of the out of plane angle of the arterial segment on the cross-sectional area estimation of the videodensitometry technique. After corrections were made for the out of plane angle using two different projections, there was a good correlation between the actual and the measured cross-sectional area using the videodensitometry technique (slope = 0.91, intercept = 0.11 mm2, r = 0.99). These data suggest that it is possible to quantitate absolute cross-sectional area without any assumption regarding the arterial shape using videodensitometry in conjunction with the motion immune dual-energy subtraction technique.

Quantitative arteriography of apparently normal coronary segments with nearby or distant disease suggests presence of occult, nonvisualized atherosclerosis

OBJECTIVES

The aim of this study was to evaluate, using quantitative arteriography, whether the diameter of visually normal coronary segments might be influenced by the relative proximity of visually apparent disease.

BACKGROUND

Severity of coronary artery lesions is commonly referenced against a presumed normal nearby coronary segment with the presumption that visually smooth segments are relatively free of atherosclerotic disease.

METHODS

Angiograms from 136 male patients with focal coronary disease were examined, and visually normal segments in the proximal portions of the major vessels were identified for measurement of mean segment diameters. Normal segments with immediately adjacent disease were compared with normal segments with distal disease in the same vessel and compared with normal segments in vessels for which the only other visible disease was in distant vessels. Angiograms with entirely normal findings from 26 age-matched men with atypical chest pain were used as controls. Segments were measured after nitroglycerin administration by means of computer-assisted quantitation.

RESULTS

Mean diameters of visually normal segments with distant disease were smaller than those of control segments (p < 0.05). Normal left main and proximal left anterior descending coronary artery segments in patients with disease within the same vessel were significantly smaller than normal segments in patients with distant disease (p < 0.05). Normal segments with immediately adjacent disease had smaller mean diameters than normal segments with distal disease in the same vessel (p < 0.05).

CONCLUSIONS

Visually normal coronary segments have progressively smaller lumen diameters, depending on the relative proximity of visible disease. Measurement of percent stenosis on the basis of the diameter of apparently normal adjacent reference segments can result in underestimation of coronary lesion severity.

Robust simultaneous detection of coronary borders in complex images

Visual estimation of coronary obstruction severity from angiograms suffers from poor inter- and intraobserver reproducibility and is often inaccurate. In spite of the widely recognized limitations of visual analysis, automated methods have not found widespread clinical use, in part because they too frequently fail to accurately identify vessel borders. The authors have developed a robust method for simultaneous detection of left and right coronary borders that is suitable for analysis of complex images with poor contrast, nearby or overlapping structures, or branching vessels. The reliability of the simultaneous border detection method and that of the authors' previously reported conventional border detection method were tested in 130 complex images, selected because conventional automated border detection might be expected to fail. Conventional analysis failed to yield acceptable borders in 65/130 or 50% of images. Simultaneous border detection was much more robust (p<.001) and failed in only 15/130 or 12% of complex images. Simultaneous border detection identified stenosis diameters that correlated significantly better with observer-derived stenosis diameters than did diameters obtained with conventional border detection (p<0.001), Simultaneous detection of left and right coronary borders is highly robust and has substantial promise for enhancing the utility of quantitative coronary angiography in the clinical setting.

Directional low-pass filtering for improved accuracy and reproducibility of stenosis quantification in coronary arteriograms

Considers the quantification of percent diameter stenosis in digital coronary arteriograms of low spatial resolution. To improve accuracy and reproducibility an edge-preserving smoothing method, called the directional low-pass filter (DLF), was developed to suppress quantum noise by averaging image intensity in a direction parallel to the vessel border. Accuracy of stenosis quantification was assessed by using stenosis phantoms. The standard error of the estimate (SEE) was 0.76 pixel-length (p) without spatial filtering and further reduced to 0.50 p by DLF; the average deviation as a measure of the regularity of border definition was also reduced by DLF from 1.00 to 0.68 p (n=50, P<0.001). It was shown that the DLF outperformed the conventional moving average filter and median filter. Reproducibility in terms of intraframe variability was assessed by using coronary arteriograms obtained from 10 patients. Intraframe variability of the percent stenosis measurements was reduced from 3.5% to 2.9% by DLF (n=10, P<0.005). An analysis of variance showed, however, that the interframe variability cannot be reduced by any of the spatial filters under investigation. The result of this study has provided a guideline for angiographically based quantification of percent stenosis under limited imaging resolution and suggests a new method for improving accuracy and reproducibility by directional low-pass filtering.

Comparison of magnetic resonance angiography, duplex ultrasound, and digital subtraction angiography in assessment of extracranial internal carotid artery stenosis

The results of a prospective study comparing ultrasound, intra-arterial digital subtraction angiography, and magnetic resonance angiography in the assessment of the degree of extracranial internal carotid artery stenosis are reported in patients with symptoms of recent carotid territory ischaemia. A total of 70 patients and 137 vessels were examined by all three techniques. The results obtained by each technique were reported blind. The mean difference (SD) for the comparison of magnetic resonance angiography and digital subtraction angiography was -0.7 (14)%, for ultrasound and digital subtraction angiography 3.1 (15)%, and for magnetic resonance angiography and ultrasound -3.8 (15)%. The level of agreement was greater for the more tightly stenosed vessels. With the assumption that the results of the digital subtraction angiogram reflect the true situation, the sensitivity and specificity in the detection of > or = 30% stenoses were 93% and 82% with ultrasound and 89% and 82% with magnetic resonance angiography; for stenoses > or = 70% 93% and 92% with ultrasound and 90% and 95% with magnetic resonance angiography; and for stenoses of 70-99% 89% and 93% with ultrasound and 86% and 93% with magnetic resonance angiography. For occlusion the values were 93% and 99% with ultrasound and 80% and 99% with magnetic resonance angiography. Increased sensitivity and specificity were obtained when analysis was confined to those vessels in which ultrasound and magnetic resonance angiography were in agreement over classification. It is thus possible to accurately categorize the degree of stenosis of the extracranial internal carotid artery from a combination of ultrasound and magnetic resonance angiography. The adoption of this combination for the investigation of patients before carotid endarterectomy removes the risk associated with conventional angiography and represents an important advance in the management of carotid stenosis.

A randomized trial comparing coronary angioplasty with coronary bypass surgery. Emory Angioplasty versus Surgery Trial (EAST)

BACKGROUND

The clinical benefit of percutaneous transluminal coronary angioplasty (PTCA) as compared with coronary-artery bypass grafting (CABG) for patients with multivessel coronary artery disease has not been established. To determine the outcomes of these treatments in patients referred for the first time for coronary revascularization, we conducted a three-year prospective, randomized trial comparing the two procedures.

METHODS

Revascularization was performed by accepted methods. Follow-up clinical information was collected every six months, and coronary arteriography and thallium stress scanning were performed at one and three years. The primary end point was a composite of death, Q-wave myocardial infarction, and a large ischemic defect identified on thallium scanning at three years. Secondary end points included clinical and angiographic status and the need for additional revascularization procedures. Data were analyzed according to the intention-to-treat principle.

RESULTS

Of the 5118 patients screened for the trial, 842 (16.5 percent) were eligible for enrollment, and 392 (7.7 percent) agreed to participate. A total of 194 patients were randomly assigned to the CABG group, and 198 to the PTCA group. The primary end point occurred in 27.3 percent of the CABG group and 28.8 percent of the PTCA group (P = 0.81). Death occurred in 6.2 percent of the CABG group and 7.1 percent of the PTCA group (P = 0.73 by log-rank test). At three years, the proportions of patients in the CABG group who required repeated bypass surgery (1 percent) or angioplasty (13 percent) were significantly lower than the proportions in the PTCA group (22 and 41 percent, respectively; P < 0.001). Angiographic studies at three years showed a greater degree of revascularization in the CABG group. Angina was more frequent in the PTCA group (20 percent) than in the CABG group (12 percent).

CONCLUSIONS

We found that CABG and PTCA did not differ significantly with respect to the occurrence of the composite primary end point. Consequently, the selection of one procedure over the other should be guided by patients' preferences regarding the quality of life and the possible need for subsequent procedures.

Dyslipidemia and coronary artery disease

Genetically determined and metabolically induced disturbances in lipid metabolism, as manifested in several types of dyslipidemia, have been shown to be causally related to the development of coronary artery disease (CAD). A diversity of clinical and angiographic studies has been made to evaluate the linkage between plasma lipid-control therapy in the development of initial and recurrent cardiovascular events. The plan of treatment invariably begins with a low-fat, low-cholesterol diet before initiation of drug therapy. However, many patients have difficulty in adhering to the low-fat diet. Fortunately, metabolic studies show that foods which contain fats rich in stearic (saturated) and oleic (monounsaturated) fatty acids may be given in limited amounts to boost patients' compliance to a low-fat diet and to prevent their blood lipids from rising to abnormal levels. A bile acid sequestrant (cholestyramine or colestipol) is the first-line drug for control of hypercholesterolemia. Either gemfibrozil or gemfibrozil plus niacin is prescribed to raise high-density lipoprotein (HDL) levels of CAD patients. Approval of two HMG CoA reductase inhibitors, pravastatin and simvastatin, by the FDA gives physicians the additional flexibility of employing a single or a combination drug therapy for optimal control of dyslipidemia. The association of low serum cholesterol level (< 160 mg/dl) with increase in noncardiac mortality has prompted health professionals to consider modifying the universal screening and treatment of serum cholesterol in children and young women and to use hypolipidemic drugs in patients judiciously.

Correlation of pharmacological 99mTc-sestamibi myocardial perfusion imaging with poststenotic coronary flow reserve in patients with angiographically intermediate coronary artery stenoses

BACKGROUND

The physiological assessment of angiographically intermediate-severity stenoses remains problematic. Functional measurements of poststenotic intracoronary Doppler coronary flow reserve can be performed in humans but have not been correlated with hyperemic myocardial perfusion imaging or angiographic data in this patient population.

METHODS AND RESULTS

Thirty-three patients undergoing diagnostic quantitative coronary angiography (QCA) for assessment of intermediate-severity coronary artery disease (mean QCA percent diameter stenosis, 56 +/- 14%) were studied. Proximal and distal poststenotic Doppler coronary flow velocities were measured (left anterior descending coronary artery, 16; right coronary artery, 10; left circumflex artery, 7 patients) before and during peak maximal hyperemia with intracoronary adenosine (8 to 12 micrograms). Intravenous pharmacological stress (adenosine, 20 patients; dipyridamole, 13 patients) 99mTc-sestamibi tomographic perfusion imaging was performed within 1 week of coronary flow-velocity studies. kappa statistics were calculated to measure the strength of correlation among coronary flow velocities, perfusion imaging data, and QCA results. QCA stenosis severity (abnormal, > or = 50% diameter stenosis) and poststenotic Doppler coronary flow reserve (ratio of abnormal distal hyperemic to basal flow, < or = 2.0) were correctly correlated in 20 of 27 patients (74%; kappa = .48). QCA stenosis severity and 99mTc-sestamibi imaging (abnormal if one or more reversible myocardial segments were present in the poststenotic zone) were correlated in 28 of 33 patients (85%; kappa = .63). 99mTc-sestamibi imaging results agreed with the basal (nonhyperemic) proximal-to-distal velocity ratio (normal, < 1.7) in 15 of 31 patients (48%; kappa = .17). The strongest correlation occurred between hyperemic distal flow-velocity ratio measurements and 99mTc-sestamibi perfusion imaging results in 24 of 27 patients (89%; kappa = .78). All 14 patients with abnormal distal hyperemic flow-velocity values had corresponding reversible 99mTc-sestamibi tomographic defects. More reversibly hypoperfused segments were present in patients with abnormal poststenotic hyperemic flow-velocity ratios (abnormal, 2.4 +/- 0.7 segments; normal, 0.6 +/- 1.0 segments; P < .05). The number of poststenotic myocardial 99mTc-sestamibi perfusion defects was correlated with the QCA percent cross-sectional area reduction (P < .02) and with minimal luminal diameter (P < .05) of intermediate-severity coronary artery stenoses.

CONCLUSIONS

Two technologically diverse functional measures of stenosis severity--Doppler-derived poststenotic hyperemic intracoronary flow reserve and vasodilator stress 99mTc-sestamibi myocardial perfusion imaging--are highly (89%) correlated. The physiological assessment of coronary stenoses of angiographically intermediate severity may be improved by the use of these techniques.

Variability of human coronary artery geometry: an angiographic study of the left anterior descending arteries of 30 autopsy hearts

A computer-based system is described to measure objectively the geometric parameters of arteries from pairs of projection angiograms. This technique, which employs back-projection to define the vessel axes in 3-D space, was used to obtain selected parameters of coronary artery geometry from radiographic images of autopsy hearts. Results of the first 30 cases are presented, focussing on the distribution of the geometric parameters of the left anterior descending coronary artery (LAD) and its first two major branches. The derived parameters include the angle between the left circumflex artery and the LAD; the angles between the LAD and its early diagonal and septal perforator branches; distances between branch points; and tortuosity. The geometric parameters vary considerably, presumably contributing to a corresponding variability in local hemodynamic and mechanical stresses. Most parameters are uncorrelated. One exception is the angle at the origin of the second diagonal branch, which is positively correlated (p < 0.01) with the distance between the ostia of the first two diagonal vessels; this correlation could reflect the existence of "target" perfusion regions. No relation between geometric parameters and age or gender was seen. In this sample, blacks had a larger angle at the left main bifurcation than whites (p < 0.05).

Effects of intensive lipid-lowering therapy on the coronary arteries of asymptomatic subjects with elevated apolipoprotein B

BACKGROUND

Do the benefits of intensive lipid-lowering therapy seen in symptomatic patients extend to high-risk subjects who have never had symptoms?

METHODS AND RESULTS

Of 120 men completing the FATS trial, 91 were symptomatic and 29 asymptomatic. All had apolipoprotein B > or = 125 mg/dL, a positive family history, and coronary atherosclerosis. All were counseled in diet and randomized to intensive therapy: colestipol 10 g TID plus either niacin 1 g QID or lovastatin 20 mg BID or to conventional therapy: placebos, or colestipol if low-density lipoprotein cholesterol was elevated. End points included quantitative arteriographic disease change and clinical events over a 2.5-year interval. At baseline, symptomatic and asymptomatic patients had comparable risk profiles, but proximal stenosis severity averaged 36% for symptomatic and 23% for asymptomatic patients (P < .001). Among the 91 symptomatic patients, those in the intensive group experienced definite (> or = 10%S) proximal lesion progression less frequently than conventional (24% of intensive versus 48% of conventional) and definite regression more frequently (36% of intensive versus 15% of conventional) (P = .009). Similarly, among the 29 asymptomatic patients, 19% of intensive versus 38% of conventional had progression and 31% of intensive versus 0% of conventional, regression (P = .04). Ischemia on baseline exercise tolerance testing was associated with significantly greater proximal disease progression among the asymptomatic patients. Clinical cardiovascular events (death, infarction, or revascularization) occurred in 10 of 38 symptomatic patients originally assigned to conventional therapy, compared with 5 of 76 symptomatic patients assigned to intensive (P < .01); no asymptomatic patient had an event.

CONCLUSIONS

Asymptomatic subjects with this high-risk profile have less coronary disease at baseline than comparable symptomatic patients, and they have an excellent short-term clinical prognosis. However, asymptomatic subjects are indistinguishable from symptomatic patients in terms of their arterial disease progression with conventional therapy and their regression with intensive. These findings may justify an active treatment strategy in such subjects, particularly those with provokable ischemia.

Computer assisted quantification of vasospasm on angiograms

We describe a new computer-based, automated method for the assessment of in vivo cerebral vasospasm. Arterial diameter measurements were performed on post-processed digital substraction angiographic images, using "pixel" as the unit. Vasospasm which was difficult to detect by visual inspection could be measured by the "stenosis quantification" program. A computer-assisted method such as we describe might decrease the risk of subjective errors.

Effect of cholesterol reduction by simvastatin on progression of coronary atherosclerosis: Design, baseline characteristics, and progress of the Multicenter Anti-Atheroma Study (MAAS)

The Multicenter Anti-Atheroma Study (MAAS) is a 2 + 2-year, placebo-controlled trial to evaluate the effect of simvastatin, a 3-hydroxy-3-methylglutaryl coenzyme a (HMG-CoA) reductase inhibitor, on progression and regression of coronary atherosclerosis in patients with established coronary artery disease. This paper describes the aims, methodology, and baseline data. Patients with at least two coronary segments visibly involved with atherosclerosis, in whom an angiogram was carried out according to the standards required for quantitative analysis, were selected provided that the serum total cholesterol was between 5.5 and 8.0 mmol/L and fasting triglycerides were lower than 4 mmol/L. Between march 1988 and October 1989, 383 eligible patients of both sexes aged 30-67 years were randomized in 11 European clinics. Patients received either 20 mg oral simvastatin or placebo daily for 2 years in addition to dietary counseling. The primary outcome measures are the change in the mean absolute width and in the mean of the minimal width of segments analyzed quantitatively by coronary angiography performed before and after 2 and 4 years of trial medication. To this end, at least 5 coronary artery segments are analyzed in each angiogram using matched view. The 2-year analysis was completed on 89% of eligible patients in February 1992. The trial was initially designed with a 2-year treatment period. To allow for the possibility to extend this, the decision was taken to keep all patients on the original medication allocation until all 2-year angiograms had been analyzed. Based on a predefined decision rule, an independent committee then recommended extension of treatment with another 2 years, to be concluded by a third angiogram. Of the patients enrolled initially, 81% continued. Four-year follow-up will be completed late 1993 and final results are expected mid 1994.

Lipid lowering and plaque regression. New insights into prevention of plaque disruption and clinical events in coronary disease

The consensus of evidence from angiographic trials demonstrates both coronary artery and clinical benefits from lowering of lipids by a variety of regimens. The findings of reduced arterial disease progression and increased regression have been convincing but, at best, modest in their magnitude. For example, among those treated intensively in FATS, the mean improvement in proximal stenosis severity per patient was < 1% stenosis, and only 12% of all lesions showed convincing regression. In view of these modest arterial benefits, the associated reductions in cardiovascular events have been surprisingly great. For example, coronary events were reduced 75% in FATS; this was entirely a result of a 93% reduction in the likelihood that a mildly or moderately diseased arterial segment would experience substantial progression to a severe lesion at the time of a clinical event. We believe that the magnitude of the clinical benefit is best explained in terms of this observation, according to the following lines of reasoning. Clinical events most commonly spring from lesions that are initially of mild or moderate severity and then abruptly undergo a disruptive transformation to a severe culprit lesion. The process of plaque fissuring, leading to plaque disruption and thrombosis, triggers most clinical coronary events. Fissuring is predicted by a large accumulation of core lipid in the plaque and by a high density of lipid-laden macrophages in its thinned fibrous cap. Lesions with these characteristics constitute only 10-20% of the overall lesion population but account for 80-90% of the acute clinical events. In the experimental setting, normalization of an atherogenic lipid profile substantially decreases the number of lipid-laden intimal macrophages (foam cells) and depletes cholesterol from the core lipid pool. In the clinical setting, intensive lipid lowering virtually halts the progression of mild and moderate lesions to clinical events. Thus, the reduction in clinical events observed in these trials appears to be best explained by the relation of the lipid and foam cell content of the plaque to its likelihood of fissuring and by the effects of lipid-lowering therapy on these "high-risk" features of plaque morphology. The composite of data presented here supports the hypothesis that lipid-lowering therapy selectively depletes (regresses) that relatively small but dangerous subgroup of fatty lesions containing a large lipid core and dense clusters of intimal macrophages. By doing so, these lesions are effectively stabilized and clinical event rate is accordingly decreased.

Definition and measurement of restenosis after successful coronary angioplasty: implications for clinical trials

Angiographic restenosis represents the most established measure of long-term outcome in most prospective clinical trials of coronary angioplasty (PTCA). The accuracy of assessing this endpoint is of utmost importance. The purpose of this article is to propose guidelines for the use of coronary angiography in this setting. First, the cineangiograms must be of high technical quality and performed in a high proportion of consecutive patients in follow-up under controlled study conditions that are reproducible. Second, computer-assisted quantitative coronary angiographic analysis is essential to minimize interobserver and intraobserver variability in stenosis measurement between successive studies. The following recommendations are presented for quantitative coronary angiographic analysis. Because biplane orthogonal views cannot always be performed both at baseline and at follow-up, stenosis measurement in the single-plane, most severe view often constitutes the most consistent and practical approach. The edge-detection method is still much more reproducible and accurate than densitometry and should be the preferred method of analysis. Measurement of reference diameter by the interpolated method is more objective than measurement by the user-defined approach and should be used whenever possible. Finally, measurements of absolute minimum diameter and percent diameter stenosis are both important in the assessment of outcome in clinical trials. Absolute minimum diameters are independent of variations in reference diameter, and the extent of reduction in minimum diameter between the immediate postangioplasty and follow-up angiograms, when expressed in dichotomous or continuous fashion, accurately defines the extent of vessel wall hyperplasia as an endpoint. On the other hand, vessel size corresponds in general to the size of myocardium subserved, and absolute changes do not take into account this physiologic fact. Therefore defining restenosis in terms of significant reduction in percent diameter stenosis is also a useful approach because of its clinical relevance. Thus clinical restenosis requires that a successfully dilated segment (< 50% diameter stenosis) show a > or = 50% diameter stenosis at follow-up angiography with, in addition, a meaningful degree of change, that is, exceeding 2 SDs of observer variability in quantitative measurements which, in our experience, translates into > or = 15% difference between early postangioplasty and follow-up angiography measurements.

Natural history of coronary atherosclerosis using quantitative angiography in men, and implications for clinical trials of coronary regression. The Harvard Atherosclerosis Reversibility Project Study Group

Previous studies of the natural history of coronary disease generally relied on estimates of percent stenosis derived from visual assessment of the coronary angiogram. In a study of 26 patients, serial quantitative angiography was performed 3 years apart to determine changes in both absolute measurements of the luminal diameter and relative percent stenosis. Initially, the mean minimal diameter of 74 coronary obstructions was 1.94 +/- 0.09 mm, the mean "normal" reference diameter was 3.06 +/- 0.11 mm, and the mean percent stenosis was 37%. At follow-up, there was a mild reduction of 0.12 +/- 0.04 mm (6%) in the minimal diameter (p < 0.005), and an increase in percent stenosis to 39% (p = 0.03). The average diameter of 85 arterial segments without a focal obstruction either initially or at follow-up showed mild but significant progression (-0.11 +/- 0.04 mm; p = 0.02). Using a minimal change of 0.27 mm in arterial diameter as a categoric variable, progression occurred in 26% of 74 arterial segments, no significant change in 65%, and regression in 9%. The only significant determinant of disease progression was the initial severity of disease. Obstructed arteries with a larger initial minimal diameter and presumably milder disease progressed more rapidly than did those with a smaller diameter (r = -0.42; p = 0.0002). There was no effect of age on the rate of progression (r = 0.02; p = NS).(ABSTRACT TRUNCATED AT 250 WORDS)

Arteriographic view of treatment to achieve regression of coronary atherosclerosis and to prevent plaque disruption and clinical cardiovascular events

Lipid-lowering therapy, as assessed by angiography, clearly benefits the arterial disease process. For example, among intensively treated patients in FATS the frequency of definite progression per lesion at risk was reduced by 75% among mild and moderate lesions, which form the great preponderance of the lesion population. Regression frequency per lesion was more than doubled by intensive therapy in mild and moderate subgroups and quadrupled in the subgroup with severe lesions. Clinical events were reduced by 73%. This was clearly due to a 15-fold reduction in the likelihood that a mildly or moderately diseased arterial segment would undergo abrupt and substantial progression to a severe lesion at the time of the clinical event. It has been shown that the process of plaque fissuring, leading to plaque disruption, thrombosis, and clinical coronary events, is predicted by the size of the plaque core lipid pool and the abundance of lipid-laden macrophages in its fibrous cap. Experimentally, lipid lowering therapy decreases the number of lipid-laden intimal macrophages and more slowly depletes core cholesteryl ester deposits. Thus the composite of new and previously published data presented here supports the idea that lipid-lowering therapy selectively lipid-depletes (causes regression of) those fatty lesions containing a large lipid core and abundant intimal foam cells. By doing so, these lesions, which are most vulnerable to fissuring, are rendered much more stable and the clinical event rate is accordingly decreased.

Discordant results of visual and quantitative estimates of stenosis severity before and after coronary angioplasty

The ability to accurately estimate the severity of epicardial coronary stenoses is critical in the assessment of the immediate and long-term results of percutaneous transluminal coronary angioplasty (PTCA). We prospectively compared visual estimates, performed by experienced interventional cardiologists, with computerized quantitative angiographic measurements of stenosis severity in a group of patients (n = 305) before, immediately after and 6 months after PTCA. Before PTCA the visual estimate of the mean (+/- SD) percentage stenosis severity, 80.6 (+/- 9.7)%, was significantly (P < 0.001) higher than the equivalent value, 73.4 (+/- 11.1)%, obtained with use of quantitative angiography. Immediately after PTCA the visual estimate of the mean residual stenosis, 18.8 (+/- 12.3)%, was significantly (P < 0.0001) lower than the equivalent quantitative estimate, 37.4 (+/- 14)%. Additionally, the residual stenosis was more frequently (18% vs. 3%) classified as significant (> 50%) by quantitative angiography. At follow-up, quantitative measurements of stenosis severity showed a Gaussian distribution with a mean of 54.8 (+/- 21)%, whereas visual estimates had a bimodal distribution with populations greater than 70% and less than 50%. Visual estimates provide an inaccurate assessment of the immediate and medium term results of PTCA. Quantitative measurements suggest that the immediate results of PTCA are frequently misclassified as successful by the operator. Conversely, restenosis rates are underestimated by the operators suggesting that a more objective method must be used in trials to assess the impact of new therapies on the rate of restenosis.

Early effects of tissue-type plasminogen activator added to conventional therapy on the culprit coronary lesion in patients presenting with ischemic cardiac pain at rest. Results of the Thrombolysis in Myocardial Ischemia (TIMI IIIA) Trial

BACKGROUND

The early effects of tissue-type plasminogen activator (t-PA) on the "culprit" coronary lesion in patients presenting with unstable angina or non-Q wave myocardial infarction were determined by quantitative arteriography.

METHODS AND RESULTS

Of 391 such patients, 306 satisfied clinical and arteriographic requirements for eligibility and received a 90-minute front-loaded infusion of t-PA (0.8 mg/kg i.v.; maximum, 80 mg) or placebo plus conventional antianginal therapy. All patients received full heparinization and a follow-up arteriogram 18-48 hours after treatment. A non-Q wave myocardial infarction (MI) was diagnosed in 97 patients (32%) after entry. In the entire patient population, among t-PA- and placebo-treated patients, respectively, 25% versus 19% (p = 0.25) of all culprit lesions achieved the primary study end point, measurable improvement (by > or = 10% reduction of stenosis or two Thrombolysis in Myocardial Infarction [TIMI] flow grades) at follow-up. Substantial improvement (by > or = 20% reduction of stenosis or two TIMI grades) was seen with t-PA in 15% of all culprit lesions versus 5% with placebo (p < 0.003). Arteriographically apparent thrombus was present at baseline in the culprit lesion of 107 patients (35%). Substantial improvement was more frequent with t-PA among lesions containing apparent thrombus (in 36% with t-PA versus 15% with placebo; p < 0.01), as it was among patients evolving a non-Q wave MI (33% versus 8%; p < 0.005). By multivariate analysis, the significant, independent predictors of substantial improvement include apparent thrombus (p = 0.0001), non-Q wave MI (p = 0.003), and t-PA use (p = 0.01). Both non-Q wave MI status and thrombus had been specified a priori as important variables.

CONCLUSIONS

Arteriographically apparent intraluminal thrombus and improvement of the culprit lesion with either of these regimens were only moderately frequent in patients with unstable angina or non-Q wave MI. Substantial improvement of culprit lesions was more frequent with t-PA than with placebo overall and in two prospectively defined subgroups. The clinical relevance of these observations is being tested in the larger, ongoing clinical TIMI IIIB study.

Ischemia: reperfusion injury and restenosis after coronary angioplasty

Percutaneous transluminal coronary angioplasty (PTCA) is a very effective technology that allows, without surgery, successful mechanical revascularization of acutely or chronically obstructed coronary arteries. The success of PTCA in patients with acute myocardial infarction or unstable angina is questioned by early coronary reocclusion and by so-called reperfusion injury. In a biochemical context, reperfusion injury occurs as a very complex interaction between the different tissues that build heart muscle. Free radicals play a pivotal role and initiate a deleterious cascade of events after reperfusion. Protective mechanisms such as superoxide dismutase, glutathione peroxidase, and catalase are normally present in the cell to prevent damage by free radicals. Endothelial cells have a greater number of specific physiologic and metabolic functions and influence the microcirculatory flow. In the presence of exogenous glucose, coronary endothelial cells show a pronounced lactate production under well-oxygenated conditions. Low energy demand and high glycolytic activity may be the cause of why the coronary endothelium is less severely injured than the cardiomyocytes in the ischemic and anoxic heart. The success of PTCA in patients with chronically obstructed coronary arteries (stable angina) is questioned by vessel occlusion and restenosis. Restenosis is a very complex process involving clinical, morphological, procedural, regional flow-dependent, and biological determinants. Early platelet deposition, formation of mural thrombus, coronary vasospasm, and elastic recoil forces of stretched vessel wall may contribute to early restenosis in the first days after PTCA, but the peak incidence of restenosis occurs between two and three months after PTCA. Intimal hyperplasia or proliferation of smooth muscle cells is believed to be the fundamental process of restenosis. To solve the problem of restenosis, much effort has been expended, which includes several technical and pharmacological approaches. Pharmacological strategies, systemically or locally administered, aim at increased vasomotor tone, platelet function, smooth muscle cell proliferation/migration, and fibrocollagenous healing. Up to now none of the proposed drugs has been able to reduce the restenosis rate. There is experimental evidence for a claim that the antioxidant functions of vitamins (E, C, and beta-carotene) may prevent restenosis post-PTCA. Until recently, in most post-PTCA restenosis trials the angiographic analyses were not performed using computerized measurement methods. In order to assess the efficacy of acute or long-term interventions on the natural course or acute complications of coronary artery disease, quantitative measures have been introduced and validated that make use of digital coronary angiography and computerized image processing techniques.(ABSTRACT TRUNCATED AT 400 WORDS)