Clinical application of quantitative coronary angiography using the CAAS system: preliminary results of the INTACT study (International Nifedipine Trial on Antiatherosclerotic Therapy)

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.

Association between coronary occlusions and myocardial infarcts. The INTACT investigators. International Nifedipine Trial on Antiatherosclerotic Therapy

The number of angiographically documented coronary occlusions and the incidence of Q-wave myocardial infarcts were retrospectively compared in 348 patients with moderate coronary artery disease from the INTACT study (International Nifedipine Trial on Antiatherosclerotic Therapy). In only 68 out of 118 infarcts (58%) an occlusion of the respective coronary artery was found, suggesting a spontaneous recanalization rate of 42%. On the other hand, only 68 out of 150 coronary occlusions (45%) had resulted in a Q-wave infarct. Considering the high spontaneous recanalization rate of the occlusions, it seemed possible that roughly only every fourth coronary occlusion might result in a myocardial infarct. This hypothesis was confirmed in the prospective 3 years follow-up of the identical patients during which 41 new occlusions developed causing only 10 myocardial infarcts (24%). These findings might contribute to explain the relatively low incidence of clinically apparent coronary heart disease in the general population despite a high prevalence of coronary artery disease.

Influence of the selection of angiographic projections on the results of coronary angiographic follow-up trials. International Nifedipine Trial on Antiatherosclerotic Therapy Investigators

In recent years follow-up trials on coronary artery disease with angiographic end points analyzed quantitatively have gained increasing relevance and popularity. There is no consensus, however, on the method of calculation of progression or regression from multiple angiographic projections. Therefore the influence of the selection of angiographic projections on the outcomes of such trials was investigated with the data of the International Nifedipine Trial on Antiatherosclerotic Therapy. In 348 patients with coronary artery disease, repeated coronary angiograms were compared in multiple identical angiographic projections. Changes in angiographic parameters were averaged over the 1063 stenoses analyzed. Five methods of evaluation of multiple projections in the individual stenoses were applied, resulting in different extents of overall progression, or even regression of coronary artery disease (p < 0.01). It is concluded that in quantitative coronary angiographic follow-up trials changes should be averaged over all angiographic projections available for a stenosis to avoid overestimation of progression or regression.

Fate of side branches after intracoronary implantation of the Gianturco-Roubin flex-stent for acute or threatened closure after percutaneous transluminal coronary angioplasty

Side branch occlusion may occur in the course of percutaneous transluminal coronary angioplasty (PTCA), particularly if complicated by site dissection. Concern that the additional placement of a stent may further jeopardize side branches is logical. Consequently, this study analyzed pre-PTCA, post-PTCA, poststent, and 6-month follow-up angiograms of 100 consecutive patients in whom 103 Gianturco-Roubin stents were implanted for acute or threatened closure after PTCA. Side branches were defined as major (> 50% of the stented vessel diameter) and minor (< 50%). Minor branches, often < 1 mm in diameter, were assessed only for patency. One hundred eight major branches, of which 33 were diseased (> 50% stenosis), and 129 minor branches were analyzed. Seven major branches (6%), all of which were diseased before PTCA, and 23 minor branches (18%) were lost after PTCA. Immediately after stent insertion, only 1 additional major and 1 minor branch were lost, whereas 2 of 7 major (29%) and 9 of 23 minor (39%) branches reappeared. At follow-up angiography, 7 major branches (6%) were more stenosed and 6 (6%) were improved compared with the angiogram before PTCA. Only 2 major (2%) and 5 minor (4%) branches remained occluded. Additionally, 2 major and 1 minor branch, which were patent after PTCA and stenting, were occluded at follow-up as a result of total occlusion of the stented segment.(ABSTRACT TRUNCATED AT 250 WORDS)

Clinical and angiographic variables affecting the progression of coronary artery disease as determined by quantitative angiography

To assess by serial quantitative angiography, the significance of clinical and angiographic variables that affect the progression of coronary artery disease (CAD). Progression of disease by sequential angiography is unpredictable and the role of clinical risk factors controversial. Various intervention trials have demonstrated less progression and even regression in hyperlipidemic patients. Correlates of progression have included a younger age, unstable angina, and greater involvement of the coronary arteries, with few studies looking at angiographic features of individual lesions. Serial angiograms on 74 patients were analyzed by computer assisted quantitative angiography using absolute measurements. A total of 99 diseased segments were analyzed for progression defined as an absolute reduction of 20% in luminal cross-sectional area. A preliminary correlation coefficient was calculated for each of the clinical and angiographic variables to detect any association with progression, and the odds ratio determined. The presence of any of the clinical risk factors-diabetes, hypertension, serum cholesterol, smoking, and a family history of coronary disease could not predict progression. The use of beta blockers was three times less likely to be associated with progression (odds ratio 0.33). While the presence of distal disease was associated with progression of a more proximal lesion (odds ratio 2.4), eccentricity, branch point location, lesion length, calcification, thrombus, or the presence of collaterals did not influence progression of disease in an individual segment. In conclusion, the presence of any of the clinical risk factors could not predict progression of disease in an individual coronary segment as determined by serial quantitative angiography, and the use of beta blockers and the absence of coexistent distal disease was associated with less progression of disease in an individual coronary segment. This may be related to changes in wall stress, reduced platelet interactions, and the integrity and permeability of the vascular endothelium to lipids.

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.

Progression of coronary artery disease is dependent on anatomic location and diameter. The INTACT investigators

OBJECTIVES

This study represents the first prospective, quantitative analysis of the association of progression of coronary atherosclerosis with anatomic site and diameter.

BACKGROUND

The progressive course of coronary artery disease has been documented in many angiographic follow-up trials.

METHODS

The data of 348 patients with coronary artery disease from the International Nifedipine Trial on Antiatherosclerotic Therapy (INTACT) were reviewed. Standardized coronary angiograms were taken 3 years apart and were analyzed quantitatively. The coronary tree was subdivided into 25 segments. The progression of 1,063 preexisting coronary stenoses and the appearance of 247 newly formed stenoses was assessed in relation to the mean diameter of segments (< 2 mm, 2 to 3 mm, > 3 mm) and to their position in the coronary tree (proximal, mid, distal) and in the three major coronary arteries.

RESULTS

Decreases in the minimal diameter of preexisting stenoses were largest in segments that were > 3 mm in diameter (mean +/- SD 0.23 +/- 0.5 mm vs. 0.10 +/- 0.4 mm and 0.02 +/- 0.3 mm, p < 0.001), in a proximal position (0.14 +/- 0.5 mm vs. 0.09 +/- 0.4 mm and 0.06 +/- 0.3 mm, p = 0.081) and in the right coronary artery (0.14 +/- 0.4 mm vs. 0.07 +/- 0.4 mm and 0.07 +/- 0.3 mm, p < 0.01). Changes in percent diameter stenosis of preexisting stenoses were lowest in segments that were < 2 mm in diameter and in a distal position (p = NS). The number of new stenoses/segment was lowest in segments that were < 2 mm in diameter (44 of 1,756 vs. 139 of 1,967 and 64 of 1,125, p < 0.001) and in a distal position (77 of 2,370 vs. 84 of 1,193 and 86 of 1,285, p < 0.001) and was highest in segments of the right coronary artery (100 of 1,546 vs. 66 of 1,496 and 72 of 1,492, p = 0.044).

CONCLUSIONS

Progression of coronary artery disease occurs most frequently in coronary segments that are > 2 mm in diameter, in a proximal or midartery position and in the right coronary artery.

Quantitative angiographic follow-up studies on the development of coronary artery disease: which coronary segments should be analyzed? Experience from INTACT

Angiographic follow-up studies on the evolution of coronary artery disease are of increasing relevance. It has still to be evaluated which coronary segments are predominantly involved in the process of atherosclerosis and, thus, should be preferably included in the analysis. Therefore, the correlation of progression and regression of coronary disease with the diameter and location (proximal, mid or distal) of coronary segments was investigated from the data of the INTACT-study, in which 25 different coronary segments were defined including anatomic variants of rather distal segments. In 348 patients with coronary artery disease, standardized coronary angiograms were repeated within 3 years and were quantitatively analyzed (CAAS). In 1063 coronary stenoses (% diameter stenosis > 20%) compared from both angiograms, progression and regression were not influenced by diameter nor location of arterial segments. In the follow-up angiograms, the number of new lesions (stenoses and occlusions) per coronary segment differed with regard to segment diameter (> 3 mm: 64/1125 (6%); 2-3 mm: 139/1967 (7%); < 2 mm: 44/1756 (2%); p < 0.001) and location of segments (proximal: 86/1285 (7%); mid: 84/1193 (7%); distal: 77/2370 (3%); p < 0.001). Out of 77 distal new lesions, only 25 (32%) were found in segments < 2 mm in diameter. Since the absolute number of new lesions was high in distal coronary segments, but low in segments with diameters < 2 mm, angiographic follow-up studies should analyze coronary segments at any location, but may neglect segments with diameters smaller than 2 mm.

Anatomical progression of coronary artery disease in humans as seen by prospective, repeated, quantitated coronary angiography. Relation to clinical events and risk factors. The INTACT Study Group

BACKGROUND

At present, there is extensive knowledge on the clinical course of coronary artery disease (CAD), whereas data on the underlying anatomical changes and their relation to clinical events are still limited.

METHODS AND RESULTS

We investigated progression and regression of CAD prospectively over 3 years in 230 patients (average age, 53.2 years) with mild to moderate disease by applying quantitated, repeated coronary angiography. Minimal stenotic diameters, segment diameters, and percent stenosis were analyzed by the computer-assisted Coronary Angiography Analysis System (CAAS). Progression was defined either as an increase in percent stenosis of preexisting stenoses by greater than or equal to 20% including occlusions or as formation of new stenoses greater than or equal to 20% and new occlusions in previously angiographically "normal" segments. At first angiography, we found 838 stenoses greater than or equal to 20% (average degree, 39.3%) and 135 occlusions in the four major coronary branches (4.23 lesions per patient). At second angiography, 82 (9.8%) of the preexisting stenoses had progressed, 15 of them up to occlusion (1.8%; preocclusion degree averaging 46.6%; 29.7-65.6%). In addition, there were 144 newly formed stenoses (average degree, 39.2%) and 10 new occlusions. Hence, 25 (2.6%) of all stenoses had become occluded. Altogether, 129 patients (56.1%) showed progression: 68 (29.6%) with new lesions only, 27 (11.7%) with preexisting lesions, and 34 (14.8%) with both types. Regression (decrease in degree of stenoses greater than or equal to 20%) was present in 29 stenoses (3.6%) and 28 patients (12%). The incidence of new myocardial infarctions was low, with three originating from occluding preexisting stenoses and one from new stenoses; hence, only four (16%) of the 25 new occlusions led to myocardial infarctions. Risk factor analysis showed that cigarette smoking correlated significantly with the formation of new lesions (p = 0.001), whereas total cholesterol correlated with the further progression of preexisting stenoses (p = 0.017) but not with the incidence of new lesions.

CONCLUSIONS

In patients with mild to moderate CAD, the angiographic progression is slow (in this study 18.7% of patients and 7% of stenoses per year) but exceeds regression (4.1% of patients and 1.2% of stenoses per year). Progression is predominantly seen in the formation of new coronary stenoses and less in growth of preexisting ones. Most of the stenoses were of a low degree (less than 50%), clinically not manifest including those going into occlusion and leading to myocardial infarction. Progression was influenced by risk factors, especially cigarette smoking (formation of new lesions) and high cholesterol levels (progression of preexisting stenoses).

Concept of an antiatherosclerotic efficacy of calcium entry blockers. INTACT Investigators

Animal experiments suggest an inhibitory effect of calcium entry blockers on arterial calcinosis and the formation of atherosclerotic plaques. Experiments with isolated tissues suggest various mechanisms for an antiatherosclerotic effect of calcium entry blockers. INTACT, the International Nifedipine Trial on Antiatherosclerotic Therapy, is the first study investigating, with a prospective, placebo-controlled, randomized, double-blind design, the influence of a calcium entry blocker (nifedipine 80 mg/day) on the progression of coronary atherosclerosis in patients with proven coronary artery disease. Study endpoints were changes of established coronary stenoses (diameter reduction greater than or equal to 20%), as well as the formation of new stenoses as documented by coronary angiography. Standardized coronary angiograms were taken before and after a treatment period of 3 years. The angiograms were quantitatively analyzed with the computer-assisted edge detection system CAAS. Of the 425 patients included in the study, 282 patients (134 on nifedipine and 148 on placebo) revealed no protocol violations. In the inclusion angiograms of these patients, 893 coronary stenoses were detected which were not significantly influenced in their development by nifedipine. However, 196 entirely new coronary lesions, 185 stenoses and 11 occlusions, were found in the follow-up angiograms. There were 78 lesions in 54 patients (40%) on nifedipine (0.58 new lesions/patient) and 118 lesions in 73 patients (49%; n.s.) on placebo (0.8 new lesions/patient; p = 0.031). In two other studies on the inhibiting effect of dihydropyridine calcium entry blockers on the progression of coronary artery disease in man defining angiographic endpoints, the drugs were also shown to reduce the number of newly formed significant coronary lesions. If further trials in man confirm a protective role of calcium entry blockers against the formation of atherosclerotic coronary lesions, a new strategy in the prevention of coronary artery disease has to be considered.

Pitfalls in the determination of absolute dimensions using angiographic catheters as calibration devices in quantitative angiography

Using catheter outer diameter as a scaling device, quantitative coronary arteriography allows the precise and objective measurement of change in absolute dimensions of coronary arteries after mechanical or pharmacologic intervention. Because of variable density in the wall of the catheter, automated systems might vary in the determination of the outer catheter diameter. To examine this premise, catheters in a variety of French sizes from 6 manufacturers were injected with radiographic contrast and used as scaling devices for arterial phantoms of known geometric dimension. Radiographic diameters of the catheters were determined by applying the quantitative coronary arteriographic algorithm to the catheters using a calibration grid in the same field of view. The varying composition of the catheters resulted in differing x-ray attenuation and, subsequently, automated edge-detection algorithms varied widely in determining the actual catheter diameter to be used as a scaling factor. For instance, a Lucite "artery" with a minimal luminal diameter of 1.50 mm (image calibrated using the micrometer-determined outside diameter of a Baxter 8Fr guiding catheter) resulted in a quantitative angiographic diameter of 2.03 mm (overestimation by 35%). If the diameter of a similar size Shiley catheter was used to calibrate the image, a luminal diameter of 1.60 mm was determined: a difference of 0.43 mm based solely on differences in scaling catheter attenuation. These data suggest that a specific "fingerprint" for each catheter material and catheter French size exists, rendering generalizations about catheter size questionable. These observations are important for quantitative angiography where many brands and sizes of angiographic catheters are being used clinically.(ABSTRACT TRUNCATED AT 250 WORDS)

Dual purpose computer aided program for cardiac catheterization laboratory data management

This communication describes the design criteria used in the early systems analysis activity of the cardiac laboratory. This analysis activity required an understanding of the cardiology laboratory environment, the establishment of needs to be answered by the program, and the goals of the entire system. The rationale for inclusion of various cardiologic, demographic, quality assurance, and personnel safety parameters is discussed. The input forms used, the database structure created, and the information provided by an applications system are described. Since the system is built around a general-purpose computer (the IBM PC or compatible) and widely available powerful general purpose software, the entire system may be used for many other cardiology laboratory data management tasks.

Retardation of coronary artery disease in humans by the calcium-channel blocker nifedipine: results of the INTACT study (International Nifedipine Trial on Antiatherosclerotic Therapy)

Experimental studies have demonstrated a 30-50% reduction in the development of atheromatous lesions of the aorta in rabbits fed a diet rich in cholesterol when they were treated with nifedipine. Based on these favorable results, we designed a multicenter, placebo (PL)-controlled, randomized, double-blind study, to test the effect of 80 mg nifedipine (NIF) per day versus placebo on the progression of mild coronary artery disease (CAD) (further development of existing stenoses, especially formation of new stenoses and occlusions) over a duration of 3 years. Progression of CAD was assessed by coronary angiograms performed at entrance and at completion of the study, using a computer-assisted analysis system (CAAS) to quantitate various stenosis parameters (percent degree of stenosis and minimal stenosis diameter). Of the 425 patients enrolled, 348 (82%) underwent a second angiogram; 66 of them, however, terminated treatment prematurely after an average of 359 (placebo) and 467 days (nifedipine). A total of 282 patients (148 on placebo, 134 on nifedipine) completed the trial with full-length treatment. There were no differences between the two groups in the progression of the existing stenoses. Patients on nifedipine, however, demonstrated significantly fewer new lesions (stenoses greater than 20% or occlusions) than those on placebo: In the 282 patients undergoing the full-length treatment, there were 73 patients on placebo (49%) with 118 new lesions (0.8/patient) and 54 patients on nifedipine (40%) with 78 new lesions (0.58/patient), a difference of -27% (p = 0.031 by Cochran's linear trend test). The difference was greatest in the left anterior descending branch, with 28 patients on placebo developing 33 new lesions (0.22/patient), versus 16 patients on nifedipine with 18 new lesions (0.13/patient) (-40%; p = 0.045); and in the left circumflex branch, where 34 patients on placebo exhibited 39 new lesions (0.26/patient) versus 23 patients on nifedipine with 22 new lesions (0.16/patient) (-38%, p = 0.033). No differences were observed in the right coronary artery, the vessel with the highest number of existing and new lesions [PL] versus 0.27 [NIF] new lesions/patient) (-7.6%, p = 0.381). Hence, INTACT confirmed the previous experimental studies and demonstrates a significant reduction in newly formed coronary lesions in patients on nifedipine when compared with those on placebo, especially in the presence of early coronary artery disease.

Features of the angiographic evaluation of the INTACT study. International Nifedipine Trial on Antiatherosclerotic Therapy

INTACT (International Nifedipine Trial on Antiatherosclerotic Therapy) is a prospective, placebo-controlled, randomized, double-blind, multicenter trial analyzing the influence of 80 mg nifedipine/day on the angiographic progression of early stage coronary atherosclerosis. Coronary angiograms were taken in identical projections before and after a treatment period of 3 years. Quantitative analysis of the angiograms was performed with the computer-assisted contour detection system CAAS. For definition purposes, the coronary artery system was subdivided into 25 different segments, including all anatomic variants. Measurement parameters of segments were mean and minimal diameter, and of stenoses minimal diameter, percentage diameter reduction (at least 20%), length, and plaque area. The variable extent of the changes of these parameters in the different projections analyzed per patient in the two study angiograms was considered by separate computation of the maximal, mean, and minimal changes over these projections; the comparison of the parameter changes between the two treatment groups was performed separately according to these three modes. For all parameters, this comparison was performed on the basis of the individual 25 segments, as well as after aggregation of individual segments to arteries (RCA, LAD, and LCX), to groups of large and small segments, and to the entire coronary artery system. Assessment of changes of the coronary (patho)morphology by quantitative analysis of coronary angiograms is associated with a number of methodical limitations, which may lead to a certain variability of the results. However, due to the double-blind feature of INTACT, this variability should be comparable in the two groups of this study, allowing for a conclusive comparison.

Reproducible uniform coronary vasomotor tone with nitrocompounds: prerequisite of quantitative coronary angiographic trials

In quantitative analysis of repeated coronary angiograms, a variable vasomotor tone of the epicardial coronary arteries may influence the accuracy of the results. Therefore, we evaluated the extent and reproducibility of coronary artery dilation with nitrocompounds. In 32 patients with coronary artery disease, the vasodilatory response of angiographically normal coronary segments to different nitrocompounds was analyzed with the computer-assisted contour detection system CAAS. Twenty patients received 5 mg or 10 mg of isosorbide dinitrate sublingually. After 10 to 15 min, a maximal diameter increase was measured with an average of 16 +/- 11% (5 mg: P less than 0.01) and 28 +/- 13% (10 mg: P less than 0.001) from control. Another 12 patients received 0.025 mg per kg body weight of SIN-1, the active metabolite of molsidomine, as an intravenous infusion over 5 min. A comparable maximal dilation (29 +/- 5%; P less than 0.001) occurred after 10 to 15 min and could not be enhanced further with 0.8 mg nitroglycerin administered sublingually (28 +/- 7%; n.s.). One hour after square root of Sin-1, coronary dilation was still 24 +/- 8% (P less than 0.001 compared with control), and 0.8 mg of nitroglycerin sublingually reestablished the previous maximal dilation of 28 +/- 8%. We conclude that high doses of nitrocompounds induce a reproducible maximal coronary dilation that eliminates a substantial source of error in quantitative analysis of repeated coronary angiograms. At present, sublingual administrations of either 10 mg isosorbide dinitrate once or 0.8 mg nitroglycerin repeatedly seem to represent the easiest practicable modes to achieve maximal coronary vasodilation for an adequate period.

International nifedipine trial on anti-atherosclerotic therapy (INTACT)--methodologic implications and results of a coronary angiographic follow-up study using computer-assisted film analysis

Animal experiments demonstrated a significant suppressive effect of various calcium channel blockers on the formation of atherosclerotic lesions. Therefore, a prospective, placebo-controlled, randomized, double blind multicenter study was performed to investigate the inhibitory influence of the calcium channel blocker nifedipine (80 mg/day) on the progression of coronary artery disease in man. Study endpoints were changes of coronary morphology documented by coronary angiography with particular respect to the formation of new coronary stenoses. In 348 out of 425 patients included in the study, coronary angiograms were repeated after three years. The angiograms were standardized by induction of a maximal coronary vasodilation with high doses of nitrates and by using absolutely identical angiographic projections. Quantitative analysis of coronary cineangiograms was performed with the computer-assisted contour detection system CAAS. Parameters were mean and minimal diameter of all segments and minimal stenosis diameter, percent diameter stenosis, length and plaque area of all stenoses. Continuous intake of study medication was registered in 282 patients, 134 on nifedipine and 148 patients on placebo. In these patients, a total of 3808 coronary segments with 893 stenoses (greater than or equal to 20% diameter reduction in at least one angiographic projection) were compared on the baseline and follow-up cineangiograms. The changes in all angiographic parameters analyzed averaged over all patients by considering all angiographic projections analyzed, indicated significant progression of the disease (p less than 0.006). The average changes in all parameters were even about three times more profound, when in the individual patients only the respective projections indicating the maximal changes were considered for the calculation (p less than 0.001). However, with neither of these two analysis modes, the differences in progression between the treatment groups were statistically significant. In the follow-up angiograms, a total of 196 new coronary lesions (185 stenoses, 11 occlusions) were found at previously normal arterial sites. In patients on nifedipine, an average of only 0.58 new lesions per patient were detected versus 0.80 lesions per patient on placebo (-27%; p = 0.031). INTACT is the first prospective angiographic trial on the progression of coronary artery disease using computer-assisted quantitative coronary angiography in such a high number of patients. All parameters analyzed indicated significant progression of coronary artery sclerosis. Nifedipine had no influence on the progression of preexisting coronary stenoses, but inhibited significantly the formation of new angiographically recognizable lesions. Further prospective coronary angiographic trials with calcium channel blockers using a comparably exact method are needed to confirm the results of this study.

Elimination of variable vasomotor tone in studies with repeated quantitative coronary angiography

In quantitative coronary angiographic studies, unintentional changes of coronary vasomotor tone may have a significant influence on the coronary artery diameters, thereby increasing the variability in the measurements. To obtain objective data on these measurement variabilities, two protocols were designed to assess the influences of ionic and nonionic radiographic contrast media on the mean diameters of angiographically normal coronary arteries. The vessel sizes were determined with the CAAS using automated edge detection techniques. In 21 patients (study no. I), coronary angiograms were taken in identical angiographic projections before (control), and immediately following several (at average 7) subsequent diagnostic dye injections administered over a period of about 7 min. The ionic contrast agent diatrizoate 76% induced a coronary dilation of 19 +/- 7% (mean +/- s.d., p less than 0.001; n = 10); the nonionic agent iopromide 370 increased the coronary artery diameters by only 6 +/- 4% (p less than 0.01; n = 11). In another 11 patients (study no. II) coronary angiograms were obtained using the nonionic contrast medium iopamidol 300 at 5, 8, 10 and 11 min after the control acquisition; this protocol was repeated in the same patients with diatrizoate 76%. With iopamidol, coronary diameter changes were not significant at any time; with diatrizoate, however, coronary dilation was measured at 10 min (2 +/- 2%; p less than 0.01) and at 11 min (10 +/- 3%; p less than 0.001). In a third study it was tested, whether standardization of coronary vasomotor tone (e.g. in coronary angiographic follow-up studies) is possible by the induction of a reproducible maximum coronary dilation with nitrocompounds. In 12 patients, the mean diameters of angiographically normal coronary segments were analyzed before and at various times after i.v. administration (over 4 min) of 0.025 mg SIN-1/kg bodyweight. Coronary dilation was maximal at 10 or 15 min after the onset of the SIN-1-infusion (29 +/- 5%; p less than 0.001). 0.8 mg nitroglycerin given s.l. at 15 min did not further dilate the coronary arteries (28 +/- 7%). One hour after SIN-1, coronary dilation still amounted to an average of 24 +/- 8% (p less than 0.001) and became 'maximal' again, when 0.8 mg nitroglycerin was again administered sublingually (28 +/- 8%; p less than 0.001). In conclusion, short-term variability of coronary vasomotor tone induced by ionic radiographic contrast media can be eliminated by the use of nonionic contrast agents and observation of injection intervals of at least 2 min. In quantitative coronary angiographic follow-up studies, as well as during acute interventions (e.g., PTCA), identical baseline vasomotor tone can be achieved by induction of the maximal coronary dilation using nitrocompounds.