Quantitative analysis of coronary arteriograms by microprocessor cinevideodensitometry

Serial quantitative coronary analyses for the evaluation of one-year change in saphenous vein grafts

BACKGROUND

A paucity of data exists with respect to changes in whole saphenous vein grafts (SVGs) despite accelerated atherosclerosis within grafted saphenous vein conduits. In the present study, we evaluated the one-year change in SVGs by means of quantitative coronary analysis.

METHODS

This study enrolled consecutive 52 patients with 109 SVGs, who underwent coronary artery bypass graft surgery successfully. A follow-up study was performed in 33 patients with 65 SVGs after one year because 16 SVGs were obstructed (baseline, 8; follow-up period, 8), and 15 patients with 28 SVGs dropped out within one year.

RESULTS

Both minimal and mean lumen diameters decreased significantly (3.17 +/- 0.64 mm vs 2.41 +/- 0.57 mm, p < 0.001; 3.70 +/- 0.69 mm vs 2.92 +/- 0.70 mm, p < 0.001; respectively). Graft length also decreased significantly (107.1 +/- 25.8 vs 100.6 +/- 25.2 mm, p < 0.001). The graft shortening rate (graft shortening length/baseline graft length x 100) was greater than 5% in 33 vessels (51%) and greater than 10% in 23 vessels (35%). Coronary risk factors (smoking, diabetes mellitus, hypertension, dyslipidemia) did not reveal significant relationship with late loss of minimal and mean lumen diameters.

CONCLUSIONS

The present study showed a considerable and uniform lumen loss of SVGs after one year, irrespective of coronary risk factors. Graft length shortening was seen more than elongation.

Effects of a single oral dose of cilostazol on epicardial coronary arteries and hemodynamics in humans

Cilostazol, a novel cyclic adenosine monophosphate phosphodiesterase type III inhibitor, has been developed as an antiplatelet drug with a vasodilating action on peripheral arteries. The present study was designed to test, in humans, whether cilostazol can dilate the epicardial coronary arteries and what are its hemodynamic effects. Eight patients with chest pain syndrome were subjected to serial quantitative coronary arteriography immediately before and at 30, 60 and 150min after a single oral dose of cilostazol (200mg). Luminal cross-sectional areas (mm2) at the proximal and distal sites of major coronary arteries (6 segments at each sampling time) were significantly increased at 150 min after taking the drug. The percent increases relative to the baseline values were 25+/-7 (6.8+/-0.8-->8.3+/-1.0*) and 42+/-7% (2.1+/-0.3-->3.0+/-0.4*) in the right coronary artery, 24+/-5 (5.1+/-0.7-->6.1+/-0.8*) and 28+/-10% (1.6+/-0.31-->9+/-0.3*) in the left anterior descending artery, and 14+/-6 (5.9+/-0.9-->6.6+/-0.9*) and 24+/-10% (1.3+/-0.2-->1.5+/-0.2*) in the left circumflex artery, respectively (*p<0.05 vs baseline). This action, relative to that of nitroglycerine, was between 27% and 54%. Moreover, small but sustained decreases in systolic pulmonary pressure and stroke work index were observed. Thus, cilostazol has a mild coronary vasodilating action with minimal hemodynamic effects, thereby giving it a possible role in the treatment of coronary artery disease.

Heterogeneous vasomotor responses of coronary conduit and resistance vessels in hypertension

OBJECTIVES

The purpose of our study was to investigate the relation between conductance and resistance coronary vasomotor responsiveness in hypertensive patients without atherosclerosis.

BACKGROUND

Although similar in morphology, conduit and resistance coronary vessels differ importantly in size, function and local environment and appear to be differentially affected in certain disease processes, such as atherosclerosis and hypertension. However, little is known about the effect of hypertension on contiguous coronary conduit and resistance vessels in humans.

METHODS

Changes in coronary blood flow (a measure of resistance vessel reactivity) and coronary artery diameter (a measure of conduit vessel reactivity) were investigated in response to graded infusion of the endothelium-dependent agonist acetylcholine (ACh) in 98 patients with normal coronary arteries.

RESULTS

In 31 normotensive, euglycemic patients, conduit and resistance coronary artery responses to intracoronary infusion of ACh were significantly correlated (r = 0.73, p = 1 x 10[-6]), although eight patients (26%) had constriction of conduit but dilation of resistance arteries at peak effect. In 28 hypertensive patients without left ventricular hypertrophy (LVH), conduit and resistance artery responses to ACh remained significantly correlated (r = 0.5, p = 0.006), although 12 patients (43%) had discordant findings. Finally, in 39 hypertensive patients with LVH, conduit and resistance artery responses to ACh displayed the lowest correlation (r = 0.38, p = 0.02), with 22 patients (56%) demonstrating conduit artery constriction and resistance artery dilation.

CONCLUSIONS

Despite angiographically normal coronary arteries, heterogeneous vasomotor responses (dilation and constriction) were demonstrated in contiguous conduit and resistance arteries in normotensive and hypertensive patients referred for cardiac catheterization because of chest pain. In addition to more severe endothelial dysfunction among conduit and resistance arteries, a greater frequency of discordant conduit and resistance artery responses and resistance vessel constriction was found with increasing severity of hypertension. Our study suggests differing mechanisms of endothelium responsiveness to ACh among conduit and resistance coronary arteries.

A new technique for improved densitometric quantification of coronary artery stenoses in angiographic images

In vitro studies have demonstrated that densitometric quantification of coronary artery stenoses is superior to geometric methods to assess non-circular lumens. However, in patients, several authors have reported significant discrepancies between area reduction percentages obtained densitometrically from two different imaging projections. Some of the factors causing the discrepancies can be reduced by simple precautions taken during image acquisition. Some others may be compensated for during analysis. Nevertheless, two factors remain problematic. The first is the inadequate spatial orientation of the vessel axes at the stenotic and reference cross sections with respect to the x-rays. The second is the difficulty in identifying the same vessel cross section in both planes at the time of analysis. We have designed a new densitometric technique that eliminates the error contributions of these two factors. The technique requires simultaneously acquired biplane coronary angiograms and biplane images of a translucent cube bearing steel markers acquired in exactly the same biplane geometry. Using the two projection matrices calculated from the images of the cube, the centerlines and the edges of the coronary arteries can be reconstructed in space from the biplane angiograms. The angles between the vessel axes and the x-ray beams can be determined and the densitometric cross sections can be corrected accordingly. Moreover, the 3D reconstruction allows the identification of the same cross section in the two planes for the determination of the area reduction percentages. Validation measurements were performed on a Perspex phantom and in patients, before and after angioplasty. In both types of measurement, the interplane discrepancies could be roughly halved. The densitometric technique presented can be incorporated into routine angiography and could become a strong alternative to the geometric approach that is presently dominating this field.

The impact of vessel orientation in space on densitometric measurements of cross sectional areas of coronary arteries

Under ideal conditions, densitometric measurement of a coronary arterial cross section in biplane angiographic images should result in nearly equal cross sectional areas for both planes. However, quite appreciable discrepancies have been found by some authors in patients. In this study, the role of inadequate spatial orientation of the vessel axes relatively to the x-rays was assessed by use of a 3D technique applied to 60 stenoses (45 pre PTCA and 15 post PTCA) in simultaneously acquired digital biplane coronary angiograms of 27 CAD patients. The 3D technique yields two radius values per projection directly in mm at any arterial cross section of interest. This was used to determine the areas Ar(in mm2) of the reference cross sections. As with catheter calibration, these cross sections were thus assumed to be more or less circular, but out-of-plane effects and errors due to a catheter diameter determination in pixels were avoided. The areas of the stenotic sections were then determined densitometrically (in mm2) from the two projections (1 and 2) according to As1 = ArDs1/Dr1, resp. As2 = ArDs2/Dr2, where Dr1, Dr2, Ds1 and Ds2 are the conventional densitometric areas of the reference and stenotic cross sections measured in planes 1 and 2. As expected, the areas As1 and As2 correlated only moderately: As2 = 0.92 As1 + 0.7 mm2, r = 0.82, n = 60, SEE = 1.4 mm2. The 3D method also yielded the two spatial angles between the local vessel axis and the X-rays of both planes. These two angles were then used to correct each densitometric area for inadequate orientation. With the corrected densitometric areas As1c and As2c, the correlation improved to: As2c = 1.05 As1c + 0.03 mm2, r = 0.93, n = 60, SEE = 0.8 mm2. Inadequate orientation of the cross sections in space thus appears to be an important factor of inaccuracy in densitometric measurements of stenotic cross sections in patients.

1996 AUR Memorial Award. Densitometric analysis of eccentric vascular stenoses: comparison of CO2 and iodinated contrast media

RATIONALE AND OBJECTIVES

The authors compared the accuracies of CO2 and iodinated contrast material in the densitometric quantification of eccentric vascular stenoses.

METHODS

Five precision-machined eccentric phantom stenoses of 50%, 60%, 70%, 80%, and 90% cross-sectional area narrowing were integrated into a pulsatile ex vivo flow model, imaged with digital subtraction angiography (DSA), and analyzed with densitometry. Relationships between the actual and measured (densitometric) degree of cross-sectional area narrowing were evaluated by using linear regression analysis and paired Student t tests. Comparison measurements were obtained in en face and profile projections. In addition, the effect of iodinated contrast material concentration was evaluated over a range of dilutions (47-282 mg iodine per milliliter).

RESULTS

CO2 yielded significantly more accurate results than did iodinated contrast material (282 mg iodine per milliliter) in the 50%, 60%, and 70% stenosis models when imaging was performed en face (P < .005). The best overall correlation was observed with CO2 DSA when imaging in profile (slope = 0.91, intercept = 2.42% actual stenosis, r = .99). The accuracy of densitometric stenosis estimation was inversely related to the concentration of iodinated contrast material.

CONCLUSION

CO2 DSA densitometry, under the conditions of these experiments, yields quantitative measures of relative cross-sectional area narrowing that are comparable with, and under some circumstances surpass, those obtained with iodinated contrast material-based DSA. In this model, CO2 was more useful than iodinated contrast material in 50%-70% stenosis when imaging in the least-optimal plane of stenosis quantification, the en face projection.

Pravastatin reduces restenosis after coronary angioplasty of high grade stenotic lesions: results of SHIPS (SHIga Pravastatin Study)

We conducted a multicenter prospective, randomized, double-blind, placebo-controlled trial to test whether pravastatin, a hydroxymethyl glutaryl coenzyme A reductase inhibitor, can decrease restenosis after percutaneous transluminal coronary angioplasty (PTCA). Pravastatin 10 mg twice daily was begun at least 10 days prior to elective PTCA in patients with total cholesterol less than 280 mg/dl. The end-point was a between-group comparison of the frequency of restenosis defined as a more than 50% loss of the initial gain in diameter stenosis at the PTCA site at 3 months during follow-up by automated quantitative coronary arteriography. Of 207 patients randomly assigned to study groups, 139 patients underwent PTCA; 133 procedures were successful, and 124 patients underwent follow-up angiography at 3 months, and 179 lesions (85 pravastatin, 94 placebo) in 124 patients (62 pravastatin, 62 placebo) were analyzed. The two groups were comparable for baseline characteristics. Total cholesterol decreased by 19.6% in the pravastatin group (p < 0.001) but not in the placebo group. Although the restenosis rate was not different in the two groups (29.4% in pravastatin vs. 39.4% in placebo, p = 0.215) as a whole, it was reduced to about one fifth (8.8%) in the pravastatin group compared with 44.8% in the placebo group (p = 0.0011) when the comparison was restricted to high grade lesions (> or = 75% diameter stenosis, 34 lesions in pravastatin, 29 lesions in placebo). Pravastatin thus reduces restenosis after PTCA of high grade lesions.

Directional coronary atherectomy and progressive coronary dilatation: a comparative analysis of acute outcome

To evaluate the acute results and in-hospital complications of directional atherectomy (DCA) as compared to progressive coronary dilatation (PCD), we retrospectively analyzed the acute outcome of DCA with PCD in age-, sex-, vessel-, and lesion morphology-matched groups of patients during the same time span. There was a total of 73 matched patients (77 lesions) in each group. Angiographic success on the basis of intent to treat was 85% in the DCA cohort versus 97%. The preprocedural mean diameter stenosis was similar between the two groups (87% vs 84%; p = n.s.). The mean postprocedural stenosis was significantly lower with DCA than with PCD (11.2% vs 19.7%; p < or = 0.05). Complications including death, myocardial infarction, and need for emergency bypass surgery were not statistically different in either group. In conclusion, PCD offers an alternative method of coronary intervention in patients with "atherectomy anatomy" with a significantly higher success rate. It can also be used successfully when DCA fails or cannot be performed because of technical factors.

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

High-speed rotational coronary atherectomy (RA) is primarily used to treat complex lesions. Quantitative angiographic analysis of such complex lesions by edge detection is often unsuitable, whereas videodensitometry, measuring vessel dimensions independently of the target stenosis contours, may offer potential advantages. To gain insight into the operative mechanism of RA and to study the agreement between the two quantitative angiographic methods in measuring the minimal luminal cross-sectional area, the edge detection and videodensitometry techniques were applied to coronary angiograms of 21 lesions in 19 patients with symptoms who underwent successful RA and balloon angioplasty (BA). Obstruction diameter as determined by edge detection increased from 1.00 +/- 0.31 mm before intervention to 1.35 +/- 0.29 mm after RA (p < 0.001) and further increased to 1.74 +/- 0.33 mm after adjunctive BA (p > 0.001). The mean between-method difference (edge detection minus videodensitometry) was 0.34 mm2 before intervention, 0.13 mm2 after RA, and 0.09 mm2 after adjunctive BA (not significant). The standard deviation of the differences decreased from +/- 0.87 mm2 before intervention to +/- 0.80 mm2 after RA (not significant) and increased after BA significantly to +/- 1.21 mm2 (p < 0.05). Thus edge detection and videodensitometry provided equivalent immediate angiographic results after RA and adjunctive BA. The good agreement after RA may reflect the operative mechanism of RA, which by ablation of noncompliant plaque material yields a circular symmetric lumen with smooth surface. The increased dispersion of the between-method differences observed after adjunctive BA presumably results from dissections, plaque ruptures, and loss of luminal smoothness after balloon dilatation.

Adjunctive thrombolytic therapy during angioplasty for ischemic rest angina. Results of the TAUSA Trial. TAUSA Investigators. Thrombolysis and Angioplasty in Unstable Angina trial

BACKGROUND

Acute closure is increased after angioplasty in unstable angina, and adjunctive intracoronary thrombolytic therapy has been used successfully to increase angiographic success. The role of prophylactic thrombolytic therapy during angioplasty in unstable angina is unknown.

METHODS AND RESULTS

Four hundred sixty-nine patients with ischemic rest pain with or without a recent (< 1 month) infarction were randomized in double-blind fashion to intracoronary urokinase or placebo. Randomization was carried out in two sequential phases. In phase I, 257 patients were randomized to 250,000 U of urokinase or placebo given in divided doses at the time of angioplasty. In phase II, 212 patients were randomized to 500,000 U of urokinase or placebo in divided doses. All patients were pretreated with aspirin, and activated clotting times were followed to maintain them at > 300 seconds during angioplasty. Angiographic end points of thrombus after angioplasty were insignificantly decreased by urokinase (30 [13.8%] versus 41 [18.0%] with placebo; P = NS). Acute closure, on the other hand, was increased with urokinase (23 [10.2%] versus 10 [4.3%] with placebo; P < .02). The difference in acute closure between urokinase and placebo was more striking at the higher dose of urokinase (P < .04) than in phase I at the lower urokinase dose (P = NS). Adverse in-hospital clinical end points (ischemia, infarction, or emergency coronary artery bypass surgery) were also increased with urokinase versus placebo (30 [12.9%] versus 15 [6.3%], respectively; P < .02). Angiographic and clinical end points were worse with urokinase in unstable angina without recent infarction than with angioplasty after a recent infarction.

CONCLUSIONS

Adjunctive urokinase given prophylactically during angioplasty for ischemic rest angina as administered in this trial is associated with adverse angiographic and clinical events. These detrimental effects may be related to hemorrhagic dissection, lack of intimal sealing, or procoagulant or platelet-activating effects of urokinase.

Limitation of detection and evaluation of coronary arterial stenosis by densitometry

In coronary cineangiography, both X-ray absorption and light scatter in the image intensifier tend to degrade image quality, and so affect the accuracy of densitometric measurement of vessel diameter. To investigate this problem, we compared the accuracy and precision of the densitometric method and the edge detection method in the automated detection of stenosis in both vessel phantom and clinical studies. In the phantom study, the X-ray penetration was varied by altering the thickness of the model, and the change in the measured diameter obtained by each of the two methods was evaluated simultaneously. A difference of 5 mm in the thickness of the model was found to alter significantly (P < 0.01) measurement of the diameter obtained using the densitometric method, but not that obtained by the edge detection method. In the clinical part of the study, the accuracy of each method in the automated detection of coronary stenosis was evaluated. With respect to the detection of stenosis, the level of disagreement between the assessment of the 3 observers and what was detected by densitometry (22.8%) was 2.9 times higher than the disagreement between the observers' assessment and what was detected using the edge detection method (7.9%). When the background density of the coronary cineangiogram along the axis of the vessel was uneven, many vessel segments which had been evaluated as normal when edge-detection was used were evaluated as stenosed when densitometry was used. This study, then, demonstrates that the Lambert-Beer law does not apply in cases where the thickness of the subject varies in different locations along the axis of the same vessel. We therefore conclude that densitometry is not a reliable means of assessing coronary stenosis in such cases, due to veiling-glare and scatter, and recommend that it not be routinely used in the automated detection of coronary arterial stenosis.

Failure of epoprostenol (prostacyclin, PGI2) to inhibit platelet aggregation and to prevent restenosis after coronary angioplasty: results of a randomised placebo controlled trial

OBJECTIVE

To study the effect of epoprostenol (prostacyclin, PGI2) given before, during, and for 36 h after coronary angioplasty on restenosis at six months and to evaluate the transcardiac gradient of platelet aggregation before and after percutaneous transluminal coronary angioplasty (PTCA) in treated and placebo groups.

DESIGN

Double blind placebo controlled randomised study.

PATIENTS

135 patients with successful coronary angioplasty.

METHODS

Intravenous infusion of PGI2 (4 ng/kg/ml) or buffer was started before balloon angioplasty and continued for 36 hours. Platelet aggregation was measured in blood from the aorta and coronary sinus before and after PTCA in each group. Routine follow up was at six months with repeat angiography and there was quantitative assessment of all angiograms (those undertaken within the follow up period and at routine follow up). PRESENTATION OF RESULTS: Restenosis rates in treated and placebo groups determined according to the National Heart, Lung and Blood Institute definition IV. Comparison at follow up between the effect of treatment on mean absolute luminal diameter and mean absolute follow up diameter in the placebo group. Comparison of acute gain and late loss between groups.

RESULTS

Of 125 patients available for assessment 23 were re-admitted because of angina within the follow up period. Quantitative angiography showed restenosis in 15 (10 in the PGI2 group and five in the placebo group). Of 105 patients evaluated at six month angiography there was restenosis in nine more in the PGI2 group and 18 more in the placebo group. Total restenosis rates (for patients) were 29.2% for PGI2 and 38.3% for placebo (NS). The mean absolute gain in luminal diameter was 1.84 (0.76) mm in the PGI2 group and 1.58 (0.56) mm in the placebo group (p = 0.04); the late loss in the PGI2 group was also greater (0.65 (0.94) mm vs 0.62 (0.89) mm (NS) and there was no significant difference in final luminal diameter at follow up between the two groups (1.83 (0.88) mm v 1.59 (0.60) mm). The transcardiac gradient of quantitative platelet aggregation increased after PTCA in both groups, indicating that PGI2 in this dose did not affect angioplasty-induced platelet activation. Mean (SD) platelet activation indices in the PGI2 group were pre PTCA aorta 8.4 (4.1) v coronary sinus 8.8 (4.0) (p = 0.001) and post PTCA aorta 8.9(3.0) v coronary sinus 12.9 (5.7) (p = 0.001). In the placebo group the values were pre PTCA aorta 7.6 (3.3) v coronary sinus 7.4 (3.6) (p = 0.001) and post PTCA aorta 7.6(2.8) v coronary sinus 11.2(4.3) (p = 0.001).

CONCLUSION

The dose of PGI2 given was designed to limit side effects and as a short-term infusion did not significantly decrease the six month restenosis rate after PTCA. The sample size, which was determined by the original protocol and chosen because of the potency of the agent being tested, would have detected only a 50% reduction in restenosis rate. There was, however, no effect in the treated patients on the increased platelet aggregation seen in placebo group as a result of angioplasty. Angioplasty is a powerful stimulus to blood factor activation. Powerful agents that prevent local platelet adhesion and aggregation are likely to be required to reduce restenosis.

Quantitative angiography during coronary angioplasty with a single angiographic view: a comparison of automated edge detection and videodensitometric techniques

Little information is available on the reliability of coronary luminal measurements obtained from quantitative analysis of a single angiographic view, an approach that is central to the practical use of on-line quantitative angiography. In the present study we investigated the contribution of two different techniques of quantitative angiography, edge detection (ED) and videodensitometry (VD), to the application of this concept during coronary angioplasty. Forty-six balloon angioplasty procedures were included in this study, all of them performed in a stenosis located in the mid right coronary segment. This coronary location was chosen to optimize data collection on luminal morphology and to minimize the number of factors that may adversely affect quantitative analysis with both techniques. In all cases two orthogonal angiographic projections were obtained before, after balloon dilatation, and at follow-up. Correlation coefficients and differences between orthogonal measurements obtained with each technique were used to evaluate the agreement between orthogonal readings at every stage of the procedure. The obtained correlation coefficients and mean differences (MD) between orthogonal measurements were as follows: before percutaneous transluminal coronary angiography (PTCA), 0.67 (MD 0.01 +/- 0.47 mm2) and 0.57 (MD 0.05 +/- 0.64 mm2) for ED and VD, respectively (Pitman's test for SD, p < 0.05); after balloon dilatation, 0.32 (MD -0.56 +/- 1.53 mm2) and 0.53 (MD -0.15 +/- 1.43 mm2) for ED and VD, respectively (paired t test for MD, p < 0.05); and at follow-up 0.79 (MD -0.15 +/- 0.97 mm2) and 0.73 (MD 0.17 +/- 1.16 mm2) for ED and VD, respectively (p = NS).(ABSTRACT TRUNCATED AT 250 WORDS)

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.

Early decrease in minimal luminal diameter after successful percutaneous transluminal coronary angioplasty predicts late restenosis

Eighty-eight patients underwent serial coronary arteriography before, immediately after, 24 hours after and 7 +/- 2 months after successful percutaneous transluminal coronary angioplasty (PTCA) of 102 lesions. Severity of coronary obstruction was measured using quantitative digital angiography. Three groups of lesions were defined when comparing angiograms recorded immediately after and 24 hours after PTCA: group I--lesions with either no change or < or = 10% increase in arterial diameter stenosis after PTCA (n = 71); group II--lesions with > 10% increase in diameter stenosis after PTCA (n = 19); and group III--patients with total occlusion (n = 12). There were no significant differences in the severity of stenosis before or immediately after PTCA among the 3 groups of lesions. Twenty-four hours after PTCA the diameter stenosis was 14.2 +/- 6.3% in group I, 34.7 +/- 8.1% in group II and 100 in group III (p < 0.0001). At 7.1 +/- 2 months after PTCA the diameter stenosis was 21.2 +/- 16.8% in group I, 61.3 +/- 1.1% in group II, and 98.5 +/- 1.3% in group III (p < 0.0001). Restenosis (> or = 50% stenosis diameter) at follow-up per lesion was significantly greater in group II than in group I (73.6 vs 9.8%) (p < 0.0001). Thus, early angiographic study after successful PTCA stratifies lesions into angiographic subsets with low (group I) and high (group II) risk of coronary restenosis.

Lesion-to-lesion independence of restenosis after treatment by conventional angioplasty, stenting, or directional atherectomy. Validation of lesion-based restenosis analysis

BACKGROUND

Since many restenosis trials include patients in whom more than one lesion is treated, analysis of the angiographic data on a "per lesion" basis might be confounded by potential correlations of restenosis among multiple treated lesions within each patient. The goals of this study were: 1) to determine whether there was any correlation in the rate of restenosis among multiple lesions that underwent conventional angioplasty, stenting, or directional atherectomy within the same patient and 2) to determine whether lesions treated in a multilesion intervention experience a different magnitude of restenosis than lesions undergoing single-lesion procedures.

METHODS AND RESULTS

Of 441 patients treated by Palmaz-Schatz stenting (n = 114), directional atherectomy (n = 100), or conventional balloon angioplasty (n = 227), 67 underwent multilesion procedures involving treatment of 146 lesions. A general linear model with intraclass correlation (GLIMIC) was used to calculate the coefficient of correlation (rho) of the change in the measured minimum luminal diameter (late loss) from the time of the initial procedure to 6-month angiogram among the multiple lesions within the same patient for all 441 patients. This showed no correlation among multiple lesions within the same patient for the late loss in minimum luminal diameter (rho = -0.12 [95% CI: -0.40, 0.12]), among lesions in the same vessel (rho = 0.14 [95% CI: -0.34, 0.62]), or among different vessels (rho = -0.18 [95% CI: -0.52, 0.16]), suggesting that the magnitude of late loss is independent among multiple lesions within the same patient. There was no difference (p = 0.96) between the observed incidence of zero-, one-, and two-vessel restenosis (> or = 50% diameter stenosis at follow-up) for patients with multiple-lesion treatment and that predicted assuming lesion-to-lesion independence. Similarly, there was no difference in late loss or in the overall binary restenosis rate when single-lesion procedures were compared with multilesion procedures. Multivariable analysis of the late loss in lumen diameter (which adjusted for the effects of the acute result and the device used) demonstrated no independent effect (p = 0.20) of single-lesion versus multilesion status.

CONCLUSIONS

Luminal encroachment appears to occur at independent rates among multiple lesions treated in a single patient. The observed incidence of restenosis for patients with multiple treated lesions is accurately predicted assuming independent probabilities of restenosis. Lesion-based analysis, even when including multiple treated lesions within the same patient, is thus valid for evaluating conventional angioplasty, stenting, or directional atherectomy.

Generalized model of restenosis after conventional balloon angioplasty, stenting and directional atherectomy

OBJECTIVES

This study was designed to extend the results of a quantitative model originally developed for restenosis after stenting or atherectomy to include restenosis after conventional balloon angioplasty.

BACKGROUND

We have previously described a continuous regression model that explains late (6-month) lumen narrowing as the difference between the immediate gain and the subsequent normally distributed late loss in lumen diameter after Palmaz-Schatz stenting or directional atherectomy.

METHODS

Lumen diameter was measured immediately before and after coronary intervention on 524 consecutive lesions including those treated by Palmaz-Schatz stenting (102), directional atherectomy (134) and conventional balloon angioplasty (288). Of these lesions, 475 (91%) underwent follow-up angiography 3 to 6 months after treatment. The immediate increase in lumen diameter produced by the intervention (immediate gain) and the subsequent reduction in lumen diameter between the time of intervention to follow-up angiography (late loss) were examined. Association between demographic or angiographic variables and continuous measures of restenosis (late lumen diameter or late percent stenosis) was tested with linear regression techniques; a traditional binary measure of restenosis (late diameter stenosis > or = 50%) was evaluated with logistic regression analysis.

RESULTS

Regression models relating late lumen diameter to the immediate lumen result were successfully fitted to all segments studied. According to these models, three indexes of restenosis (late lumen diameter, late percent stenosis and binary restenosis) were found to depend solely on the immediate lumen diameter after the procedure and the immediate residual percent stenosis, but not on the specific intervention used. Moreover, the late loss in lumen diameter was found to vary directly with the immediate gain provided by an intervention, and the "loss index" (a measure that corrects for differences in immediate gain) was uniform among all three interventions.

CONCLUSIONS

The quantitative model originally developed for restenosis after stenting or atherectomy may thus be generalized to include conventional balloon angioplasty. It shows that the apparent differences in restenosis among the three interventions studied are due solely to differences in the immediate result provided and not to differences in the behavior of subsequent late loss. Moreover, although the late loss in lumen diameter was found to correlate with differences in the immediate gain provided by an intervention, the "loss index" (a measure that corrects for differences in acute gain) was uniform across all three interventions. It is thus the immediate result (and not the procedure used to obtain that result) that determines late outcome after coronary intervention.

Edge detection versus densitometry in the quantitative assessment of stenosis phantoms: an in vivo comparison in porcine coronary arteries

The aim of this study was the in vivo validation and comparison of the geometric and densitometric technique of a computer-assisted automatic quantitative angiographic system (CAAS system). In six Landrace Yorkshire pigs (45 to 55 kg), precision-drilled phantoms with a circular lumen of 0.5, 0.7, 1.0, 1.4, and 1.9 mm were percutaneously introduced into the left anterior descending or left circumflex coronary artery. Twenty-eight coronary angiograms obtained with the phantom in a wedged intracoronary position could be quantitatively analyzed. Minimal lumen diameter, minimal cross-sectional area, percent diameter stenosis, and cross-sectional area stenosis were automatically measured with both the geometric and densitometric technique and were compared with the known phantom dimensions. When minimal lumen diameter was measured using the geometric approach, a nonsignificant underestimation of the phantom size was observed, with a mean difference of -0.06 +/- 0.14 mm. The larger mean difference observed with videodensitometry (-0.11 +/- 0.20 mm) was the result of the failure of the technique to differentiate the low lumen videodensities of two phantoms of smaller size (0.5 and 0.7 mm) from a dense background. Percent cross-sectional area stenosis measured with the two techniques showed a good correlation with the corresponding phantom measurements (mean difference between percent cross-sectional area stenosis calculated from the quantitative angiographic measurements and the corresponding phantom dimensions was equal to 2 +/- 6% for both techniques, correlation coefficient = 0.93 with both techniques, SEE = 5% with the geometric technique and 6% with the densitometric approach).(ABSTRACT TRUNCATED AT 250 WORDS)

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)

Prevention of restenosis by lovastatin after successful coronary angioplasty

Prevention of restenosis after successful percutaneous transluminal coronary angioplasty (PTCA) remains a major challenge. To determine whether lovastatin could prevent restenosis, between December 1987 and July 1988, a total of 157 patients undergoing successful PTCA were randomly and prospectively assigned to the lovastatin group or a control group. Seventy-nine patients received lovastatin (20 mg daily if the serum cholesterol level was less than 300 mg/dl and 40 mg daily if the serum cholesterol level was greater than or equal to 300 mg/dl) in addition to conventional therapy (lovastatin group). Seventy-eight patients received conventional therapy alone (control group). Fifty patients in the lovastatin group and 29 in the control group were evaluated with coronary angiography at an interval of 2 to 10 months (mean 4 months). The restenosis rate was evaluated according to the number of patients showing restenosis, the number of vessels restenosed, and the number of PTCA sites restenosed. Restenosis was defined as the presence of greater than 50% stenosis of the PTCA site. In the lovastatin group 6 of 50 patients (12%) had restenosis compared with 13 of 29 patients (44.4%) in the control group (p less than 0.001). When the number of vessels restenosed was considered, only 9 of 72 vessels (12.5%) restenosed in the lovastatin group compared with 13 of 34 vessels (38.2%) in the control group (p less than 0.002). Similarly, 10 of 80 (12.5%) PTCA sites restenosed in the lovastatin group compared with 15 of 36 (41.7%) in the control group (p less than 0.001).(ABSTRACT TRUNCATED AT 250 WORDS)

Effect of H1 receptor stimulation on coronary artery diameter in patients with variant angina: comparison with effect of acetylcholine

It has been suggested that histamine is involved in the pathogenesis of coronary spasm but its exact role remains unclear. H1 receptor stimulation of the coronary artery was performed with a selective intracoronary infusion of histamine (2 micrograms/min) in 21 patients with variant angina after blockade of the H2 receptor with cimetidine (25 mg/kg) and its effect on the coronary artery diameter was examined. Intracoronary injection of acetylcholine was also performed in 19 of the 21 patients. Ergonovine (0.2 mg) was intravenously administered in one patient. The coronary artery diameter was measured with cinevideodensitometric analysis. A mean plasma histamine concentration in the coronary sinus increased from 4 x 10(-9) to 7 x 10(-8) M 5 min after histamine infusion into the left coronary artery (n = 18). Coronary spasm was induced in 6 patients (29%) with histamine, in 18 (95%) with acetylcholine and in 1 with ergonovine. The effect of histamine on the luminal diameter was analyzed at the site of spasm in the 26 coronary arteries in which spasm was induced by acetylcholine or ergonovine. Of the 20 coronary arteries with a normal arteriogram or a fixed stenosis less than or equal to 50% of luminal diameter, histamine decreased the diameter in 4, increased it in 14 (70%) and caused no change in 2; of the 6 coronary arteries with a fixed stenosis greater than or equal to 75%, histamine decreased the diameter in 5 and increased it in 1. In the coronary arteries in which spasm was not induced by either acetylcholine or ergonovine, histamine increased the diameter, especially in those without advanced atherosclerosis.(ABSTRACT TRUNCATED AT 250 WORDS)

Videodensitometry versus digital calipers for quantitative coronary angiography

Single-plane left coronary angiograms in 18 patients were prospectively analyzed using videodensitometry (XR-70 system) and handheld digital calipers to compare arterial dimensions, stenosis dimensions, intraobserver variability and interobserver variability for the methods. A total of 648 arterial segments were measured, yielding a highly significant correlation between videodensitometry and caliper-determined cross-sectional area (r = 0.96, p = 0.0001). Similarly, a highly significant linear relation was observed between videodensitometry and caliper-determined diameter (r = 0.95, p = 0.0001). When data subsets for small, medium and large arterial segments were examined, higher variability in the correlation between videodensitometry and caliper-determined area was observed in the large segments (greater than 10 mm2). In addition, caliper-estimated areas tended to be slightly smaller than videodensitometry-estimated areas in these segments. For diameter estimations, correlations between caliper and videodensitometry data were similar for the entire range of arterial segment sizes. Intra- and interobserver variability was low for both caliper and videodensitometry determination of diameter or area. Thus, over a wide range of arterial dimensions, results obtained with caliper estimates of luminal area and diameter are comparable to those obtained with videodensitometry using the XR-70 system.

Reproducibility of measurements of coronary narrowings by videodensitometry: unreliability of single view measurements

Computer-assisted videodensitometry has been shown to be a reliable and reproducible method of measuring absolute and relative coronary narrowings. Using a commercially available analyzer (Vanguard XR70) we confirmed the intra- and interobserver reproducibilities in 34 narrowings in 9 patients. Analyses were performed on normal area and diameter, stenotic area and diameter, percent area stenosis and percent diameter stenosis. For all 6 analyses, excellent intra- and interobserver correlations were found (r = 0.93-0.98), with slopes close to 1 and intercepts close to zero. In a separate study of 16 lesions in 11 patients, each lesion was analyzed in both the RAO and LAO planes. Correlation between the measurements was reasonable with r = 0.76 for the stenotic area and r = 0.75 for the absolute diameter stenosis. However, with suboptimal slopes (0.54 and 0.63 respectively), actual differences between measurements in the two planes were often unacceptably large. These data suggest that videodensitometry is a highly reproducible quantitative angiographic method; however, single view analyses are inadequate for comparative studies.

An objective computer system for the quantification of artery stenoses

We have developed a low cost, clinically usable system for the objective assessment of the severity of coronary artery stenoses from single view angiograms. The system is based on a desktop computer with incorporated frame grabber. Images are captured by means of a video camera. The user selects a region of interest which encompasses the stenosis. Facilities are provided for automatic or manual definition of the artery centre line and edges. The computer then calculates the artery diameter and cross-sectional area by videodensitometry along profile lines which are orthogonal to the long axis of the artery. These results can be expressed numerically as a percentage stenosis when compared to a normal region of the artery. The image is corrected for geometric distortion using a grid test object. The image grey scale is corrected by means of a ramp test object such that a pixel value is proportional to the attenuator thickness. The ramp is placed on the patient during the X-ray examination and an iterative technique has been developed for subtracting the underlying structures from the superimposed ramp image. The system has been assessed using test objects constructed in Perspex which simulate arteries of known cross-sectional area and stenoses of known severity.

Responses of angiographically normal human coronary arteries to intracoronary injection of acetylcholine by age and segment. Possible role of early coronary atherosclerosis

We examined the response of left coronary arteries to intracoronary injection of acetylcholine (ACh) 50 micrograms in 74 patients by measuring the diameter changes with a videodensitometric analysis system. Patients with angiographically normal coronary arteries were subdivided into a younger group of 26 patients (age, 9-29 years) and an older group of 23 patients (age, 31-68 years). In the younger group, the diameter at the distal segment of the left anterior descending artery (LAD) and at the proximal, middle, and distal segments of the left circumflex artery (LCx) increased significantly (16.7 +/- 19.3%, p less than 0.01, for LAD and 8.0 +/- 18.8%, p less than 0.05; 11.0 +/- 16.1%, p less than 0.01; and 19.8 +/- 17.5%, p less than 0.01, for LCx segments, respectively) in response to ACh. In the older group, on the other hand, the diameter at the proximal and middle segments of LAD and LCx decreased significantly (-20.8 +/- 16.9%, p less than 0.01; and -17.9 +/- 28.4%, p less than 0.01, for LAD segments and -14.6 +/- 17.4%, p less than 0.01; and -11.3 +/- 21.4%, p less than 0.05, for LCx segments, respectively). The dilator response to ACh in the younger group was significantly greater in the distal segment than in the proximal segment in both LAD and LCx (p less than 0.01 for LAD and p less than 0.05 for LCx). The constrictor response to ACh in the older group was significantly greater in the proximal than the distal segment in both LAD and LCx (p less than 0.05 for LAD and LCx, respectively).(ABSTRACT TRUNCATED AT 250 WORDS)

Effects of H1-receptor stimulation on coronary arterial diameter and coronary hemodynamics in humans

Effects of H1-receptor stimulation on coronary arterial diameter and coronary hemodynamics were examined in 11 patients with angiographically normal coronary arteries and without variant angina or resting angina. Selective H1-receptor stimulation was achieved by infusing histamine into the left coronary artery at a rate of 2.0 micrograms/min for 5 minutes after pretreatment with cimetidine (25 mg/kg). Plasma histamine concentration in the coronary sinus, coronary sinus blood flow, heart rate, and aortic pressure were measured before, during, and after the histamine infusion. Coronary arterial diameter was measured by cinevideodensitometric analysis of coronary arteriograms performed before and immediately after the histamine infusion. During the histamine infusion, plasma histamine concentration in the coronary sinus increased from 0.33 +/- 0.06 to 5.86 +/- 0.71 ng/ml (p less than 0.01); coronary sinus blood flow increased from 98 +/- 12 to 124 +/- 13 ml/min (p less than 0.01), and coronary vascular resistance decreased from 1,113 +/- 117 to 851 +/- 91 mm Hg.min/l (p less than 0.01). Heart rate and aortic pressure remained unchanged. The mean luminal diameters of the proximal, middle, and distal left anterior descending artery increased by 9.4 +/- 3.6% (p less than 0.05), 19.2 +/- 3.8% (p less than 0.001), and 31.5 +/- 5.6% (p less than 0.001), respectively, after the histamine infusion. The mean luminal diameters of the proximal, middle, and distal left circumflex artery increased by 15.2 +/- 3.6% (p less than 0.01), 17.5 +/- 5.2% (p less than 0.01), and 20.6 +/- 4.3% (p less than 0.001), respectively, after the histamine infusion.(ABSTRACT TRUNCATED AT 250 WORDS)

Importance of balloon size in coronary angioplasty

The effect of balloon size on the success of coronary angioplasty was studied to develop quantitative criteria for optimal selection of balloon size. Coronary dimensions of 165 stenotic lesions were measured by computer-assisted cinevideodensitometry in 120 patients who had undergone angioplasty with a balloon selected by visual estimates. Cross-sectional areas and diameters of normal and stenotic arterial segments were measured before and after angioplasty by a previously validated cinevideodensitometric technique. The diameter of the inflated balloon compared with that of the normal arterial segment was expressed as a ratio for sizing balloons. Oversized balloons with a ratio greater than 1.3 (n = 35) caused a high (37%) incidence of dissection, with three severely compromised arterial lumens. Undersized balloons with a ratio less than 0.9 (n = 29) often resulted in significant (greater than 50% diameter stenosis) residual stenotic lesions (21%) and a significantly (p less than 0.05) higher rate of repeat angioplasty for restenosis. Selection of balloon sizes with ratios in the 0.9 to 1.3 range (n = 101) resulted in a low (4%) incidence of dissection with few patients (3%) having significant residual stenosis. Mean residual stenosis (percent diameter reduction) was most severe for undersized (35.0 +/- 18%) or oversized (23.1 +/- 19%) balloons and least severe for balloons with a ratio of 0.9 to 1.3 (18.7 +/- 14%) (p less than 0.001). Repeat angioplasty for restenosis was more frequently required (p less than 0.05) for lesions dilated with undersized balloons. Thus, selection of angioplasty balloons that approximate or slightly exceed the diameter of the normal arterial diameter yields optimal angiographic results with minimal dissections and minimal residual stenotic lesions.

Restenosis after successful percutaneous transluminal coronary angioplasty: serial angiographic follow-up of 229 patients

To further understand the temporal mode and mechanisms of coronary restenosis, 229 patients were studied by prospective angiographic follow-up on day 1 and at 1, 3 and 6 months and 1 year after successful percutaneous transluminal coronary angioplasty. Quantitative measurement of coronary stenosis was achieved by cinevideodensitometric analysis. Actuarial restenosis rate was 12.7% at 1 month, 43.0% at 3 months, 49.4% at 6 months and 52.5% at 1 year. In 219 patients followed up for greater than or equal to 3 months, mean stenosis diameter was 1.91 +/- 0.53 mm immediately after coronary angioplasty, 1.72 +/- 0.52 mm on day 1, 1.86 +/- 0.58 mm at 1 month and 1.43 +/- 0.67 mm at 3 months. In 149 patients followed up for greater than or equal to 6 months, mean stenosis diameter was 1.66 +/- 0.58 mm at 3 months and 1.66 +/- 0.62 mm at 6 months. In 73 patients followed up for 1 year, mean stenosis diameter was 1.65 +/- 0.56 mm at 6 months and 1.66 +/- 0.57 mm at 1 year. Thus, stenosis diameter decreased markedly between 1 month and 3 months after coronary angioplasty and reached a plateau thereafter. In conclusion, restenosis is most prevalent between 1 and 3 months and rarely occurs beyond 3 months after coronary angioplasty.

Effect of isolated proximal coronary stenotic lesions on distal myocardial perfusion during exercise

This study tested the hypothesis that the absolute dimension of a coronary stenotic lesion is a more important determinant of its hemodynamic effect on regional myocardial perfusion during exercise than is relative percent stenosis. In 31 patients with an isolated lesion of the left anterior descending coronary artery, regional myocardial perfusion was determined from thallium-201 scans recorded in the left anterior oblique projection after symptom-limited treadmill exercise. Thallium-201 uptake in the distribution of the left anterior descending coronary artery was expressed as a ratio of thallium-201 uptake in the left circumflex artery distribution. Percent area stenosis, minimal cross-sectional area and mean diameter of each stenotic lesion were measured by computer-assisted cinevideodensitometric analysis of projected coronary arteriograms digitized in a 512 X 512 pixel matrix with 256 gray levels. Thallium-201 uptake in the left anterior descending coronary artery distribution, expressed as a ratio, correlated poorly (r = 0.65) with relative percent stenosis, but correlated significantly (r = 0.83; p less than 0.05) with absolute lesion area. For all 16 patients with reduced regional perfusion in the left anterior descending coronary artery distribution during exercise, lesion cross-sectional area was less than 1.8 mm2 (mean 0.9 +/- 0.6); for 13 of the 15 patients with normal distal perfusion, the area of the stenotic lesion was greater than 1.8 mm2 (mean 2.7 +/- 0.7; p less than 0.001). Percent coronary stenosis failed to predict flow-limiting lesions.(ABSTRACT TRUNCATED AT 250 WORDS)

Cinevideodensitometric analysis of the effect of coronary angioplasty on coronary stenotic dimensions

The accuracy and reproducibility of caliper and cinevideodensitometric measurements of coronary stenotic dimensions were compared in radiographic phantom models and in coronary arteriograms of 28 patients undergoing coronary angioplasty. Projected, single-plane coronary cine frames were analyzed by a computer-assisted videodensitometric method, which measures stenotic cross-sectional area without assumptions about lesion geometry. The accuracy (2.4%) and precision (+/- 1.9%) of cinevideodensitometry for measuring percent area stenosis in Plexiglas models of eccentric stenotic lesions was superior to the accuracy (24.7%) and precision (+/- 5.4%) of caliper measurements. Interobserver variability was significantly (p less than 0.05) better for cinevideodensitometric (r = 0.98; SEE = 6.4%) than for caliper measurements (r = 0.87; SEE = 13.1%). After angioplasty, percent diameter stenosis measured by calipers fell from 70 +/- 12% to 30 +/- 15%. Mean percent area reduction measured by cinevideodensitometry fell from 89.1 +/- 8% to 40.1 +/- 22% and stenotic area increased five-fold, from 0.59 +/- 0.5 to 3.47 +/- 1.6 mm2. Pre and post PTCA gradients did not correlate with lesion dimensions. Cinevideodensitometric measurements of absolute stenotic dimensions were more reproducible than relative measurements expressed as a percentage, due to the tapered caliber of normal arterial segments. Thus, cinevideodensitometric measurements were more accurate and reproducible than caliper measurements. The angiographic effects of coronary angioplasty are best measured by cinevideodensitometry, because residual lesions post PTCA are often eccentric, have indistinct margins, and are better characterized by changes in area than by changes in diameter.