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

Restenosis after coronary angioplasty

Coronary angioplasty is used to treat coronary disease in many patients. Indications for angioplasty have expanded since it was first performed, mainly as a result of improvement in equipment and techniques. One problem with coronary angioplasty is the phenomenon of renarrowing of the treated coronary lesion, a process called restenosis. The events that constitute restenosis appear to be a universal response to the arterial wall injury of angioplasty. They are currently characterized as follows: platelet adhesion and aggregation on the damaged endothelium and within deep splits into the tunica media; release of platelet-derived growth factors; inflammation of the mechanically injured medial zone; transformation of smooth muscle cells of the tunica media after their activation by several of the growth-promoting substances; migration and proliferation of transformed smooth muscle cells, with secretion of copious amounts of extracellular matrix material; and, finally, termination of the growth process with regrowth of endothelium over the injured area. A decade of research work has helped identify clinical correlates of restenosis after coronary angioplasty procedures. This work is hindered by lack of a uniform angiographic definition of restenosis. In addition, much of the information has come from small studies, with incomplete follow-up and retrospective orientation. Nevertheless, some data are available. Patient-related correlates include male gender, unstable angina, diabetes, and continued smoking after angioplasty. Lesion-related correlates include multilesional and multivessel procedures, higher postangioplasty residual stenosis, proximal vessel location, location in the left anterior descending artery, location in a vein graft, long lesions, and total occlusions. The only consistent procedure-related correlate has been incorrect sizing of the angioplasty balloon to the treated artery. For the purposes of individual patient care, clinical correlates are not helpful. No group of variables has been found to be associated with complete freedom from restenosis, and no group is completely predictive of restenosis. All patients undergoing angioplasty procedures require some follow-up through subsequent months and years. Symptom status and the results of noninvasive studies have been investigated for purposes of follow-up. Symptoms are virtually useless by themselves for predicting restenosis or its absence. When symptom status is combined with exercise thallium 201 scintigraphy performed 4 to 6 months after an angioplasty procedure, the two factors are less than ideal but have a negative predictive value of more than 90%. This means that more than 90% of patients who have neither symptoms nor evidence of ischemia by thallium 201 scintigraphy will not have angiographic restenosis.(ABSTRACT TRUNCATED AT 400 WORDS)

Restenosis after coronary angioplasty

Coronary angioplasty is used to treat coronary atherosclerotic disease in many patients. One problem with coronary angioplasty is the phenomenon of restenosis. Restenosis appears to be a universal response to arterial wall injury. The biological events that underlie restenosis are characterized by: platelet adhesion and aggregation at sites of damaged endothelium, and within dissections into the medial layers, release of platelet derived growth-promoting substances, inflammation of the injured medial zone, transformation, migration, and proliferation of smooth muscle cells of the media following their activation by growth-promoting substances, secretion of copious amounts of extracellular matrix material, and finally, termination of the growth process following regrowth of endothelium over the damaged area. More than a decade of research work has helped identify clinical correlates of restenosis after coronary angioplasty. Patient-related correlates include male gender, unstable angina, diabetes, and continued smoking after angioplasty. Lesion-related correlates include multilesion and multivessel procedures, higher post-angioplasty residual stenosis, proximal vessel location, location in the left anterior descending coronary artery, location in a vein graft, long lesions, and total occlusions. However, for the purposes of individual patient care, clinical correlates are not particularly helpful. No group of variables has predicted complete freedom from restenosis, and conversely no group of variables has reliably indicated its presence. All patients undergoing angioplasty will require some form of follow-up evaluation. Symptom status by itself has not been found to be useful for predicting restenosis. However, when symptom status is combined with exercise thallium-201 scintigraphy, performed 4-6 months after angioplasty, it is less than ideal, but has a negative predictive value of over 90%. This means that over 90% of patients who are asymptomatic and have no evidence of ischemia by thallium-201 scintigraphy, will not have angiographic restenosis. Numerous clinical trials have been performed in order to reduce or prevent restenosis. Almost all have been disappointing, while a few have been encouraging. Studies of antiplatelet agents such as aspirin, dipyridamole (Boehringer Ingelheim Pharmaceuticals Inc., Ridgefield, CT, USA), and Ticlopidine (Syntex, Humgcao, Puerto Rico) have not shown efficacy, yet studies of an inhibitor of platelet-derived growth factor have been provocatively encouraging. No reduction in restenosis rates was found with the anticoagulants Coumadin (Du Pont Pharmaceuticals, Wilmington, DE, USA) and Heparin (Wyeth-Ayerst, Philadelphia, PA, USA). Fish oils (omega fatty acids) have been found in several clinical trials to provide modest, but encouraging, reductions in restenosis, but await further confirmation.(ABSTRACT TRUNCATED AT 400 WORDS)

The effect of porous infusion balloon-delivered angiopeptin on myointimal hyperplasia after balloon injury in the rabbit

BACKGROUND

Angiopeptin, a synthetic somatostatin analogue, reduces myointimal hyperplasia after experimental balloon angioplasty when given subcutaneously. The feasibility and efficacy of a single dose of angiopeptin delivered locally via the Wolinsky porous balloon on myointimal hyperplasia were studied.

METHODS AND RESULTS

Three rabbits received 125I-angiopeptin in the mid abdominal aorta via the Wolinsky balloon at 5 atm for 1 minute after balloon injury. Thirty minutes later, autoradiography demonstrated radioactivity in the media and the adventitia. Forty rabbits were divided equally into one control group receiving saline and three angiopeptin groups receiving 1, 10, or 100 micrograms/mL of angiopeptin delivered locally at 5 atm for 1 minute via the Wolinsky balloon into the mid abdominal aorta after balloon injury of the entire abdominal aorta. On day 21, the abdominal aortas were fixed in situ and harvested. There was no statistical difference in the amount of myointimal hyperplasia in the locally treated aorta in the angiopeptin groups compared with the control group. However, in the lower abdominal aorta, where balloon injury without local delivery was performed, there was a significant reduction of myointimal hyperplasia in the highest-concentration angiopeptin group (P < .001 versus the control group). Electron microscopy showed that the control animals had a pseudointima of smooth muscle cells throughout the aorta, whereas in all the angiopeptin-treated animals, endothelial cells were present at both locations.

CONCLUSIONS

Angiopeptin can be delivered intramurally via the Wolinsky porous balloon and reduces myointimal hyperplasia only in the area distal to the local drug delivery site (downstream effect), possibly by healing the injured endothelium, by transport via the vasa vasora, and/or by systemic effect.

A comparison of directional atherectomy with coronary angioplasty in patients with coronary artery disease. The CAVEAT Study Group

BACKGROUND

Directional coronary atherectomy is a new technique of coronary revascularization by which atherosclerotic plaque is excised and retrieved from target lesions. With respect to the rate of restenosis and clinical outcomes, it is not known how this procedure compares with balloon angioplasty, which relies on dilation of the plaque and vessel wall. We compared the rate of restenosis after angioplasty with that after atherectomy.

METHODS

At 35 sites in the United States and Europe, 1012 patients were randomly assigned to either atherectomy (512 patients) or angioplasty (500 patients). The patients underwent coronary angiography at base line and again after six months; the paired angiograms were quantitatively assessed at one laboratory by investigators unaware of the treatment assignments.

RESULTS

Stenosis was reduced to 50 percent or less more often with atherectomy than with angioplasty (89 percent vs. 80 percent; P < 0.001), and there was a greater immediate increase in vessel caliber (1.05 vs. 0.86 mm, P < 0.001). This was accompanied by a higher rate of early complications (11 percent vs. 5 percent, P < 0.001) and higher in-hospital costs ($11,904 vs $10,637; P = 0.006). At six months, the rate of restenosis was 50 percent for atherectomy and 57 percent for angioplasty (P = 0.06). However, the probability of death or myocardial infarction within six months was higher in the atherectomy group (8.6 percent vs. 4.6 percent, P = 0.007).

CONCLUSIONS

Removing coronary artery plaque with atherectomy led to a larger luminal diameter and a small reduction in angiographic restenosis, the latter being confined largely to the proximal left anterior descending coronary artery. However, atherectomy led to a higher rate of early complications, increased cost, and no apparent clinical benefit after six months of follow-up.

A comparison of directional atherectomy with balloon angioplasty for lesions of the left anterior descending coronary artery

BACKGROUND

Restenosis is a major limitation of coronary angioplasty. Directional coronary atherectomy was developed with the expectation that it would provide better results than angioplasty, including a lower rate of restenosis. We undertook a randomized, multicenter trial to compare the rates of restenosis for atherectomy and angioplasty when used to treat lesions of the proximal left anterior descending coronary artery.

METHODS

Of 274 patients referred for first-time, non-surgical revascularization of lesions of the proximal left anterior descending coronary artery, 138 were randomly assigned to undergo atherectomy and 136 to undergo angioplasty; 257 of 265 eligible patients (97 percent) underwent follow-up angiography at a median of 5.9 months. Computer-assisted quantitative measurements of luminal dimensions were determined from the angiograms obtained before and immediately after the procedure and at follow-up. The primary end point of restenosis was defined as stenosis of more than 50 percent of the vessel's diameter at follow-up.

RESULTS

Quantitative analysis showed that the procedural success rate was higher in patients who underwent atherectomy than in those who had angioplasty (94 percent vs. 88 percent, P = 0.061); there was no significant difference in the frequency of major in-hospital complications (5 percent vs. 6 percent). At follow-up, the rate of restenosis was 46 percent after atherectomy and 43 percent after angioplasty (P = 0.71). Despite a larger initial gain in the minimal luminal diameter with atherectomy (mean [+/- SD], 1.45 +/- 0.47 vs. 1.16 +/- 0.44 mm; P < 0.001), there was a larger late loss (0.79 +/- 0.61 vs. 0.47 +/- 0.64 mm; P < 0.001), resulting in a similar minimal luminal diameter in the two groups at follow-up (1.55 +/- 0.60 vs. 1.61 +/- 0.68, P = 0.44). The clinical outcomes at six months were not significantly different between the two groups.

CONCLUSIONS

The role of atherectomy in percutaneous coronary revascularization remains to be fully defined. However, as compared with angioplasty, atherectomy did not result in better late angiographic or clinical outcomes in patients with lesions of the proximal left anterior descending coronary artery.

Coronary atherectomy versus angioplasty: the CAVA Study

Directional coronary atherectomy was developed with the hope that it would lower the risk of acute closure and restenosis by leaving a larger smoother lumen and fewer dissections than angioplasty. To evaluate this hypothesis, we compared the clinical and angiographic results of directional coronary atherectomy with those of percutaneous transluminal coronary angioplasty in well-matched groups. We studied 126 consecutive atherectomies and 127 angioplasties performed on similar lesions. Procedural results were evaluated with regard to dissections, complications, acute closure, and residual stenosis. Each patient's clinical course was followed, and each patient was contacted at 6 months for evaluation of recurrent angina, need for repeat catheterization, and angiographic rate of restenosis. Baseline clinical and angiographic characteristics of the two groups were well matched and met the criteria established as being appropriate for atherectomy. The angiographic success rate was 98% after angioplasty and 99% after atherectomy. There were fewer dissections after atherectomy (13%) compared with the number after angioplasty (22%; p = 0.03). Residual stenosis was 8.3 +/- 9% after atherectomy compared with 15 +/- 12% after angioplasty (p = 0.0001). However, there were more complications after atherectomy (p = 0.03). There was no significant difference between the two groups in the recurrence rate of angina or in the angiographic restenosis rate at 6 months. It was concluded that when lesion characteristics and vessel size are appropriate for atherectomy, the procedural success rate of either atherectomy or angioplasty is extremely high. Although atherectomy leads to a larger residual lumen and fewer dissections, the complication rate after atherectomy is higher than that after angioplasty. There is a trend toward more occlusions after atherectomy.(ABSTRACT TRUNCATED AT 250 WORDS)

Local infusion balloon angioplasty to obviate restenosis compared with conventional balloon angioplasty in an experimental model of atherosclerosis

Balloon angioplasty is an accepted treatment for arterial obstruction; however, a substantial percentage of initially successfully treated lesions recur in the first 4 to 6 months. There is increasing interest in local treatment of lesions undergoing angioplasty to prevent restenosis, and an infusion catheter has been developed for this purpose. This study compared infusion balloon angioplasty by means of saline solution with conventional balloon angioplasty in atherosclerotic iliac arteries of 18 cholesterol-fed New Zealand white rabbits. Values for minimum stenosis diameter assessed angiographically immediately after maximum infusion balloon angioplasty (2.1 +/- 0.6 mm) and after conventional balloon angioplasty (2.3 +/- 0.3 mm, p = NS) were similar. In follow-up studies up to 5 weeks after angioplasty, the angiographic minimum stenosis diameter remained similar in the two treatment groups, but the histologically assessed intimal area was greater after infusion angioplasty (1.54 +/- 0.92 mm vs 1.02 +/- 0.75 mm in conventionally treated arteries, p = 0.0001). Infusion balloon angioplasty merits further evaluation as a treatment strategy for the simultaneous dilatation of atherosclerotic lesions with delivery of therapeutic agents to minimize restenosis.

Percutaneous transluminal coronary angioplasty or coronary by-pass surgery in the management of chronic angina pectoris

The treatment modalities for patients with chronic stable angina have expanded since the introduction of percutaneous revascularization procedures such as percutaneous transluminal coronary angioplasty. In selected patients, these percutaneous procedures provide an excellent alternative to surgical revascularization; in other patients, percutaneous transluminal coronary angioplasty is an excellent alternative to medical therapy. Selection of the optimal therapy depends on the specific coronary anatomy, left ventricular function, clinical setting, and the need for complete revascularization. Also, the availability of bailout devices, such as stents for the dilatation procedure, needs to be considered in higher risk patients or higher risk lesions. Currently, randomized trials that are being completed will allow comparison of surgical versus angioplasty approaches and will improve our ability to tailor therapy for specific subsets of patients.

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.

Influence of platelet size before coronary angioplasty on subsequent restenosis

Platelet size has been shown to reflect platelet activity. We prospectively measured the mean platelet volume (MPV) in 47 patients undergoing single vessel angioplasty for symptomatic angina. The patients underwent repeat angiography 4-8 months later irrespective of symptomatic status. Restenosis was assessed quantitatively by hand held calliper measurements of the lesion and qualitatively by a return of angina, ST segment changes on an exercise test and visual analysis of the lesion severity by two experienced angiographers. Twenty-four patients developed recurrent angina during the follow-up period, the MPV in the group with chest pain was 8.54 +/- 0.60 fl compared to 8.1 +/- 0.69 fl in the asymptomatic group (P = 0.04). Twenty two patients had significant ST segment changes at exercise. In this group the MPV was 8.6 +/- 0.56 fl compared to 8.0 +/- 0.70 fl for the group with a negative test (P = 0.002). Similarly visually assessed angiographic stenosis showed a significant increase in the restenotic group (8.6 +/- 0.56 vs. 8.0 +/- 0.61 fl, P = 0.001). The relative odds for developing clinically defined restenosis were 10.2 times greater if the pre-procedural MPV lay in the upper compared to the lowest quartile. There was a positive correlation between MPV and change in minimal luminal diameter between post angioplasty and follow-up angiography, assessed quantitatively, r = +0.56, P = 0.016. There was no association between clinical or angiographic definitions of restenosis and haemoglobin, red cell count, mean corpuscular volume, white cell count or platelet count. Platelet size may influence the development of restenosis after successful coronary angioplasty.

Potentiation of the vasospastic response to angioplasty by pretreatment with fluoxetine. A study in the atherosclerotic rabbit

There is evidence that angioplasty-induced vasospasm is mediated by serotonin (5-hydroxytryptamine [5-HT]) release from platelets. We tested the hypothesis that pretreatment of the atherosclerotic rabbit with fluoxetine, a platelet-uptake inhibitor of 5-HT, would reduce vasospasm after balloon angioplasty. Short-term administration of fluoxetine reduced platelet 5-HT uptake to 4% of baseline. Daily administration of fluoxetine for 7 days reduced whole-blood 5-HT levels to 28% of baseline. Thus, fluoxetine inhibited platelet 5-HT uptake in this model as predicted. Contrary to our expectations and despite the substantial reduction in whole-blood 5-HT levels, pretreatment with fluoxetine for 1 week resulted in augmentation of angioplasty-induced vasospasm in atherosclerotic rabbits. Intraperitoneal administration of fluoxetine produced vasoconstriction in normal rabbits that was augmented by 5-HT and not reversed with LY53857, a specific serotonin receptor antagonist. We postulate that this new observation is probably a result of the inhibition of the clearance mechanism for serotonin, with resultant enhancement of the effect of serotonin released by the activated platelets that are deposited on the vessel wall surface at the time of angioplasty. A direct effect of fluoxetine on serotonergic receptors is a second possible mechanism for the observed effect.

Treatment of long coronary artery narrowings with long angioplasty balloon catheters

Balloon angioplasty of long coronary artery narrowings has been associated with a lower rate of acute success, and a higher rate of acute complications and restenosis than that observed for short narrowings. Angioplasty catheters with longer length balloons (30 and 40 mm) are now available, and the objective of this study was to determine the acute and long-term success for patients with long coronary artery narrowings treated with these longer balloons. All patients with long narrowings (> or = 10 mm) treated with long balloons at 1 institution over a 1-year period were identified (93 narrowings in 89 patients), and acute and long-term outcomes were carefully documented. Procedural success (residual stenosis < or = 50%) was 97%. Abrupt closure occurred in 6% and major dissection in 11% of narrowings. Clinical success (procedural success without in-hospital death, bypass surgery or myocardial infarction) was achieved in 90% of patients. Repeat catheterization was performed in 61 patients (76% of those eligible), and restenosis was found in 50 to 55%, depending on the definition used. The treatment of long coronary artery narrowings using angioplasty catheters with longer balloons leads to high rates of acute success. However, there is a high rate of restenosis. New interventional devices for long lesions should be compared with long balloons in a randomized controlled trial.

Excimer laser-assisted coronary angioplasty for lesions containing thrombus

OBJECTIVES

The purpose of this study was to analyze the success rates for excimer laser-assisted coronary angioplasty performed in patients undergoing angioplasty for lesions containing thrombus.

BACKGROUND

The presence of intracoronary thrombus increases the risk of a poor clinical outcome after balloon angioplasty. The effect of intracoronary thrombus on the safety and efficacy of excimer laser-assisted coronary angioplasty is unknown.

METHODS

Percutaneous excimer laser-assisted coronary angioplasty was attempted in 142 patients, of whom 12 had angiographic evidence of intracoronary thrombus in 14 lesions, defined as a filling defect surrounded by contrast medium or an area of contrast staining.

RESULTS

Clinical success (< 50% residual stenosis without myocardial infarction, death or bypass surgery at any time during hospitalization) was achieved in 7 (58%) of the 12 patients with intracoronary thrombus, compared with 123 (95%) of the 130 patients without thrombus (p = 0.00001). Angiographic and clinical complications were more common in patients with thrombus: embolization (25% vs. 1%, p < 0.001), myocardial infarction (33% vs. 2%, p < 0.001), abrupt closure (17% vs. 4%, p = 0.049). Angiographic restenosis at 6 months was seen at 7 (70%) of 10 treated sites with intracoronary thrombus and at 59 (51%) of 116 sites without thrombus (p = 0.245). Presence of intracoronary thrombus was identified as the most important predictor of clinical success (p = 0.013) by multivariable logistic regression analysis, which controlled for other co-variables, such as lesion complexity or lesion location in a saphenous vein graft.

CONCLUSIONS

This analysis shows that the success of excimer laser-assisted coronary angioplasty is compromised when thrombus is detected angiographically. Further investigation of other strategies is needed to improve the outcome of angioplasty for this challenging problem.

Serial angiographic follow-up after Palmaz-Schatz stent implantation: comparison with conventional balloon angioplasty

OBJECTIVES

Serial angiographic follow-up study was designed to evaluate the temporal mode of lumen diameter changes after Palmaz-Schatz stent implantation, and the results were compared with those from a cohort of patients undergoing balloon angioplasty.

BACKGROUND

Restenosis remains a major limitation of balloon angioplasty. The Palmaz-Schatz balloon expandable coronary stent is now under clinical investigation to evaluate its efficacy in preventing restenosis.

METHODS

Serial angiographic follow-up study was performed the day after stent implantation and at 1, 3 and 6 months after the procedure. The stent group consisted of 96 patients who had 97 lesions with a single stent. A cohort of 179 patients with 192 lesions were selected as the balloon group by the criteria of final balloon size > or = 3 mm and lesion length < 20 mm.

RESULTS

A significantly larger lumen diameter was obtained immediately after stent implantation (2.9 +/- 0.4 mm [mean +/- SD] in the stent group vs. 2.1 +/- 0.5 mm in the balloon group, p < 0.001). At 3 to 6 months of follow-up, a significantly larger lumen diameter was maintained in the stent group (2.2 +/- 0.6 vs. 1.5 +/- 0.7 mm, p < 0.001). The late restenosis rate according to a binary definition was significantly lower in the stent group (13% vs. 39%, p < 0.001). Stenosis exacerbation, frequently observed within 24 h after balloon angioplasty, was not found after stenting. Between the next day and 1 month, regression was dominant in the balloon group, whereas progression of stenosis was observed in the stent group. The greatest tendency to restenosis was observed in both groups between 1 and 3 months after the procedure. Between 3 and 6 months, significantly greater diameter loss was found in the stent group.

CONCLUSIONS

The Palmaz-Schatz stent was effective in reducing the restenosis rate in this highly selected cohort of patients. Reduction in restenosis rate was dependent on a larger lumen obtained immediately. Late loss of diameter was significantly greater after stenting. The restenosis rate after stenting should be evaluated by follow-up angiography at 6 months rather than at 3 months, which is adequate after conventional balloon angioplasty.

Serial angiographic observations after successful directional coronary atherectomy

This study focuses on the early and late angiographic evolution observed in 82 patients with coronary artery disease who were successfully treated by directional coronary atherectomy (DCA) without adjunctive balloon angioplasty. Qualitative inspections and quantitative measurements were obtained from a selected angled-view projection in the following conditions: (1) before treatment; (2) immediately after treatment; (3) the day after atherectomy; (4) 1 month after; and (5) 6 months after. The appearance of the treated segment 24 hours after the procedure did not differ in 79 patients from that observed immediately after DCA; silent total occlusion occurred in two patients, and one had an aneurysm at the site of resection (all three patients were excluded from the analysis). At the 1-month study restenosis developed in 3 (3.6%) patients; the remaining 76 had identical appearances, with no evidence of renarrowing of the lumen. However, from 1 to 6 months after the procedure restenosis developed in 35 of the remaining 76 (46%) patients, and 41 patients were free of restenosis and symptoms. These findings, which show that early elastic recoil does not occur after successful DCA, are different from the changes observed after balloon angioplasty. At the 1-month observation restenosis is an infrequent but possible phenomenon (3.8%). From this point the healing of the arterial wall leads to no or mild renarrowing (late success); an exaggerated proliferative response produces restenosis.

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

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

Time course of restenosis during the first year after emergency coronary stenting

BACKGROUND

Prevention of abrupt vessel closure after percutaneous transluminal coronary angioplasty (PTCA) represents one of the current indications for intracoronary stent implantation. After the procedure, the stented segment undergoes luminal changes that may lead to late restenosis. This study was undertaken to assess the time course of luminal changes during the first year after emergency placement of coronary stents.

METHODS AND RESULTS

Coronary stenting was indicated in patients with present or threatened vessel closure secondary to large dissections after PTCA. From June 1989 to May 1991, 82 patients who received Palmaz-Schatz stents and did not have early vessel occlusion after stenting were enrolled into a serial angiographic follow-up study. Coronary normal reference diameter and minimal luminal diameter were measured with an automated edge detection technique. Patients who underwent repeat PTCA for restenosis were excluded from further serial angiography. The restudy rate at 3, 6, and 12 months was 96%, 81%, and 90% of the eligible patients, respectively. The incidence of restenosis (defined as a diameter stenosis > or = 50%) was 22.0% at 3 months, 31.9% at 6 months, and 33.2% at 12 months. Minimal luminal diameter was increased from 0.66 +/- 0.32 mm before to 2.85 +/- 0.43 mm immediately after stenting. It was 0.46 +/- 0.31 mm smaller than the diameter of the maximally inflated balloon during the procedure. The reduction in minimal luminal diameter was 0.80 +/- 0.69 mm (p = 0.0001) for the first 3 months, 0.29 +/- 0.52 mm (p = 0.0001) between 3 and 6 months, and 0.13 +/- 0.32 mm (p = 0.01) for the last 6 months. The percentage of patients who presented a significant change in minimal luminal diameter (defined as > 0.60 mm) declined from 50.6% during the first 3 months and 18.9% between 3 and 6 months to 6.5% for the period between 6 and 12 months.

CONCLUSIONS

The incidence and the time course of restenosis after emergency coronary stenting are similar to that reported for conventional PTCA. Coronary lumen dimensions demonstrated a peak change at 3 months and remained mostly stable after the first 6 months.

Mechanisms of restenosis and redilation within coronary stents--quantitative angiographic assessment

OBJECTIVES

This study was designed to assess the relative contributions of intimal hyperplasia and stent compression to the lumen narrowing seen after intracoronary stenting and to determine whether the lumen enlargement produced by angioplasty of in-stent restenosis results primarily from compression or extrusion of intimal hyperplasia through the stent or from additional stent expansion.

BACKGROUND

Palmaz-Schatz stent placement outwardly displaces plaque and eliminates elastic vessel recoil to provide a large and smooth lumen. Some degree of late lumen narrowing occurs within each stent and causes significant restenosis (> or = 50% stenosis) in 25% to 30% of treated lesions. It has not been clear, however, whether this narrowing results from stent compression (crush) or from in-stent intimal hyperplasia. Because the Palmaz-Schatz stent has a distinct radiographic shadow, it is possible to determine the late diameter of both the stent and the enclosed vessel lumen to assess the relative contributions of these two processes.

METHODS

From cineangiograms, initial (after stenting) and late (follow-up) lumen and stent diameters were examined in 55 patients (59 stents, group I) who had both immediate and 6-month (192 +/- 117 days) angiography. Lumen and stent diameter were also examined before and after dilation in 30 patients (30 stents, group II) who underwent angioplasty of severe in-stent restenosis.

RESULTS

Late loss in minimal lumen diameter was 0.99 +/- 0.87 mm for group I despite only a slight (0.03 +/- 0.23-mm) reduction in the corresponding stent diameter. After redilation for in-stent restenosis, the acute gain in minimal lumen diameter was 1.51 +/- 0.82 mm for group II, again without appreciable increase (0.06 +/- 0.20 mm) in stent diameter.

CONCLUSIONS

Restenosis after intracoronary Palmaz-Schatz stenting appears to be due predominantly to lumen encroachment by intimal hyperplasia within the stent, with minimal contribution of stent compression. Lumen enlargement after coronary angioplasty of in-stent restenosis appears to be due primarily to compression or extrusion of intimal hyperplasia through the stent, or both, rather than to further stent expansion.

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.

Reliability of quantitative coronary angiography of the target lesion immediately and 1 day after coronary balloon and excimer laser angioplasty

OBJECTIVES

This prospective trial was performed to evaluate the impact of the morphologic complications of angioplasty on the reliability and results of quantitative angiographic assessment of the residual stenosis.

BACKGROUND

Postintervention quantitative coronary analysis is limited by a variety of such complications.

METHODS

In 199 patients undergoing an early control angiographic study within 24 h after coronary balloon or excimer laser angioplasty (24-h study), detailed quantitative angiographic measurements were performed on the target lesion immediately after intervention and at the 24-h study. Reproducibility of quantitative arteriography was determined by repeat measurements on the same angiogram.

RESULTS

Intraobserver/interobserver variability was significantly higher (p < 0.0001/p < 0.03) for the postintervention angiogram than for the 24-h angiogram. Patients were classified into three subgroups with respect to the occurrence of angiographic complications or chest pain after intervention. In patients with angiographic complications after balloon angioplasty alone/stand-alone laser angioplasty/laser angioplasty with adjunctive balloon dilation, a significant difference in mean minimal lumen diameter (p = 0.0001/p = 0.03/p = 0.035) was observed between the immediate postintervention and 24-h angiogram. In patients without angiographic complications or patients with recurrent chest pain undergoing balloon angioplasty, stand-alone or adjunctive laser angioplasty, mean minimal lumen diameter remained nearly unchanged (p = NS).

CONCLUSIONS

Angiographic measurements of the target lesion immediately after angioplasty were significantly less reliable than measurements obtained at 24 h after angioplasty in patients with angiographic complications. The occurrence of postintervention vascular complications was associated with significant early lesion changes between the immediate postangioplasty and the 24-h angiogram.

Influence of elastic recoil on restenosis after successful coronary angioplasty in unstable angina pectoris

The elastic behavior of the dilated coronary vessel has been reported to affect the immediate results of coronary angioplasty. To determine whether elastic recoil may also influence the long-term restenosis process, 98 consecutive patients with unstable angina and 1-vessel disease were studied. An automated coronary quantitative program was used for the assessment of balloon and coronary luminal diameters. Elastic recoil was defined as the percent reduction between minimal balloon diameter at the highest inflation pressure and minimal lesion diameter immediately after coronary angioplasty. Follow-up coronary arteriography was performed 8 to 12 months after the procedure in all patients. The mean elastic recoil averaged 17.7 +/- 16% and was correlated to the degree of residual stenosis immediately after coronary angioplasty (r = 0.64; p < 0.001). Restenosis, defined as > 50% diameter stenosis at follow-up, developed in 53 patients (54%). There was no correlation between the degree of elastic recoil and the changes in minimal lesion diameter observed during follow-up, whereas a positive correlation between the amount of elastic recoil and the incidence of restenosis was documented (r = 0.84; p < 0.05). Thus, the elastic properties of the dilated vessel do not influence the active process of restenosis. However, because elastic recoil negatively influences the initial results of angioplasty, it is more likely that further reductions in lumen diameter during follow-up can reach a threshold of obstruction considered critical for a binary definition of restenosis.

A predictive method for estimating the late angiographic results of coronary intervention despite incomplete ascertainment

BACKGROUND

Investigations of coronary restenosis typically use late (4-6-month) angiographic end points. Since only 50-80% of patients generally undergo repeat angiography, however, restenosis for the population as a whole is usually estimated by assuming that nonrestudied and restudied patients are similar. If restudied and nonrestudied patients differ, incomplete angiographic follow-up can yield an erroneous estimate of restenosis. No suitable method has yet been devised to detect and correct these errors.

METHODS AND RESULTS

We studied the clinical indications for angiographic restudy in an actual series of 301 treated lesions in 267 consecutive patients who underwent either Palmaz-Schatz stenting (126 patients) or directional coronary atherectomy (141 patients) at our institution. While only 249 (83%) treated segments underwent 4-6-month angiographic follow-up, all had clinical follow-up that described whether specific indications for restudy were present. Patients who had no clinical indications for such restudy were designated as having elective follow-up. In contrast, patients who had recurrent symptoms or positive exercise studies and were scheduled for repeat angiography at the independent recommendation of their referring cardiologist were designated as having nonelective follow-up. Mean late percent stenosis or binary restenosis rate (> 50% diameter stenosis) was determined for elective versus nonelective lesions that underwent follow-up angiography. These values were then used to input the behavior of the nonrestudied lesions according to their clinical status. From these imputations, a "predictive" model was developed to estimate the mean restenosis values that would have been found had the entire population actually undergone angiographic follow-up. Comparisons between the estimates of this predictive method and the traditional method that uses only the actual angiographic data demonstrate how alterations in various parameters influence the selection bias caused by incomplete angiographic follow-up. Of the 301 lesions available for follow-up, 100 of the 103 (97%) nonelective versus 149 of the 198 (75%, p < 0.001) elective lesions actually underwent angiographic follow-up. Mean follow-up percent stenosis (50% versus 27%) and the binary restenosis rate (53% versus 13%) differed significantly for the nonelective versus the elective lesions, respectively (both p < 0.001). Even at the fairly high (83%) angiographic follow-up rate, elective versus nonelective status was thus a confounder that caused differences between the restenosis rate estimated by the traditional (29.1%; 95% CI: 23.4, 34.7) and the predictive methods (26.3%; 95% CI: 21.4, 31.1). Larger (and even statistically significant) differences may be present under the conditions that exist in many current studies.

CONCLUSIONS

Restenosis trials with < 90% angiographic follow-up suffer from selection bias. Traditional methods that analyze only the restudied patients fail to correct for the important confounding influence of the clinical status of the nonrestudied patients. By using this readily available clinical information about the nonrestudied patients, a predictive method may be developed that provides a closer estimate of the true restenosis behavior for the population as a whole.

Quantitative analysis of factors influencing late lumen loss and restenosis after directional coronary atherectomy

Although encouraging initial results have been demonstrated after directional atherectomy, the mechanisms and predictors of late lumen loss and restenosis after this procedure have not been evaluated. To examine these issues, clinical and angiographic follow-up were obtained in 262 (96%) and 212 (77%) of 274 patients undergoing successful directional coronary atherectomy. Symptom recurrence developed in 87 (33%) patients and angiographic restenosis was found in 93 (44%). Restenosis was highest in re-stenotic lesions in saphenous vein grafts (78% [95% confidence interval (CI): 56 to 100%]) and lowest in new-onset lesions in the left anterior descending (27% [95% CI: 15 to 39%]) and circumflex (14% [95% CI: 0 to 43%]) coronary arteries. Residual lumen diameter immediately after atherectomy was smaller in re-stenotic lesions (p = 0.002) and in lesions > or = 10 mm in length (p = 0.02). Late lumen loss was associated with the minimal lumen diameter immediately after atherectomy (p < 0.001), saphenous vein graft lesion location (p = 0.008), and male gender (p = 0.02). Re-stenotic lesions (p < 0.001), lesions > or = 10 mm in length (p = 0.018), saphenous vein graft lesion location (p = 0.025) and male gender (p = 0.045) were independent predictors for restenosis. It is concluded that restenosis after directional atherectomy is related both to factors resulting in a suboptimal initial result and to factors contributing to excessive late lumen loss. These results may have implications for lesion selection in patients undergoing directional coronary atherectomy.

Clinical assessment following coronary revascularization

There remains a need to establish adequate protocols for investigating the short- and long-term follow-up of revascularization procedures. For coronary angioplasty the most reliable basis for decision-making in managing patients is the symptomatology of the patient. For bypass surgery a protocol should be established to evaluate patients late, at 5 to 10 years following bypass surgery, in particular those with saphenous vein grafting, as graft and patient survival begins to fall after this period. Investigation after this may be too late for many patients who may already have several occluded grafts and poor left ventricular function, two of the most important prognostic factors post bypass surgery. The improvement and refinement of non-invasive investigations has led to a better understanding of the value and limitations of many of these tests, but it is particularly important that the limitations of many investigation are fully appreciated when they are used to influence clinical decisions. In this regard, a study comparing and integrating the predictive value of the persistence or return to symptoms, a positive non-invasive test, and a positive invasive test would surely prove invaluable.

Coronary rotational ablation: initial experience in 302 procedures

OBJECTIVES

The aim of this study was to assess the utility of percutaneous transluminal coronary rotational ablation in the treatment of coronary artery disease.

BACKGROUND

Although numerous advances have been made in the treatment of coronary artery disease, there are lesions with complex morphology that are not amenable to current intravascular therapy.

METHODS

A consecutive series of 242 patients having 302 coronary rotational ablation procedures was analyzed. One hundred nineteen (49%) of the patients had previously undergone attempted coronary angioplasty, which was unsuccessful in 31 patients (13%). The left ventricular ejection fraction was normal in 196 patients (81%). The ablation procedure was attempted in 308 vessels and 346 lesions. Of the 346 lesions treated, 26 (7.5%) were classified as American College of Cardiology/American Heart Association type A, and 320 (92.5%) as either type B or type C.

RESULTS

Procedural success was achieved in 284 (94%) of the 302 procedures and 330 (95.4%) of the 346 lesions in which ablation was attempted. Five procedures (1.7%) were unsuccessful, but no cardiac event occurred during the hospital stay. A major cardiac event occurred in 13 cases (4.3%); 9 (3%) of these complications were due to the ablation procedure. Six patients sustained a Q wave myocardial infarction alone, two had a Q wave infarction and required emergency surgery and one needed emergency surgery but did not have a Q wave infarction. No procedural deaths were attributed to the ablation procedure. Follow-up has been obtained in 182 of the 242 patients at a mean interval of 9 +/- 5 months. Of the 182 patients, 174 (95.6%) were alive and free of myocardial infarction. Angiographic follow-up is available thus far in 87 patients. By combining angiographic and clinical outcome, an overall estimated restenosis rate of 37.4% (68 of 182) was calculated.

CONCLUSIONS

These data suggest that coronary rotational ablation can be performed on lesions with a variety of morphologic features with high initial success rates. The overall rate of restenosis is similar to that of balloon angioplasty.

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

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

Inhibitory effects of antisense oligodeoxynucleotides targeting c-myc mRNA on smooth muscle cell proliferation and migration

Smooth muscle cell (SMC) proliferation and migration play pivotal roles in restenosis following angioplasty. c-myc is an immediate early response gene induced by various mitogens, and several lines of evidence derived from experiments using transformed or hematopoietic cell lines, or transgenic mice, suggest its protein product plays a role in numerous signaling transduction pathways, including those modulating cell division. We therefore reasoned that a strategy employing oligodeoxynucleotides (ODNs) complementary to c-myc mRNA (antisense ODNs) might be potent inhibitors of SMC proliferation and, perhaps, of SMC migration. To evaluate this concept, we tested several antisense ODNs targeted to c-myc mRNA (15- or 18-mer ODNs complementary to different c-myc mRNA sequences) by introducing them individually into the medium of cultured rat aortic SMCs. Phosphoroamidate-modified ODNs were employed to retard degradation. Antisense ODNs inhibited, in a concentration-dependent manner, SMC proliferation and SMC migration. Maximal inhibitory effect was 50% for proliferation and > 90% for migration. These effects were associated with decreased SMC expression of c-myc-encoded protein by Western immunoblotting and immunocytochemical staining. ODNs with the same nucleotides but a scrambled sequence caused no effect. These results indicate that the c-myc gene product is involved in the signal transduction pathways mediating SMC proliferation and migration in the in vitro model we employed. The results also suggest a potential role of antisense strategies designed to inhibit c-myc expression for the prevention of coronary restenosis.

Chronic total obstruction and short-term outcome: the Excimer Laser Coronary Angioplasty Registry experience

Percutaneous transluminal coronary angioplasty for chronic total obstructions is associated with significantly decreased success rates in comparison with those for dilation of subtotal stenoses. Failure usually results from inability to cross the occlusive lesion with a guidewire, although it may result from inability to pass the balloon catheter after the guidewire has been passed. In the Excimer Laser Coronary Angioplasty Registry, 172 chronic total obstructions were treated in 162 patients (10.3% of the 1,569 patients entered). For chronic total obstructions, passage of a guidewire is a prerequisite for laser angioplasty. Once a guidewire crossed an occlusion, the overall laser success rate for treatment of chronic total obstructions was 83%; the extent of stenosis decreased from 100% to 55 +/- 26%. Success was independent of length of the occlusive lesion. In 74% of patients, adjunctive percutaneous transluminal coronary angioplasty was used after laser angioplasty. A final procedural success, defined as residual stenosis of less than 50% and no major complication (coronary artery bypass grafting, myocardial infarction, or death), was achieved in 90%. Major complications were infrequent; 1.2% of patients required coronary artery bypass grafting, and 1.9% had a Q-wave myocardial infarction. Only one death occurred. The use of laser angioplasty may be of particular value when chronic total obstructions can be crossed with a guidewire but not with a conventional balloon catheter or when the occlusion is confirmed to be extremely long.

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.

Biological risk factors for restenosis after percutaneous transluminal coronary angioplasty

In an attempt to discern biological (such as thrombotic or fibrinolytic) risk factors in patients developing restenosis after percutaneous transluminal coronary angioplasty, the following factors were measured prior to angiography in a population of 23 patients (20 men, 3 women, mean age 57 +/- 5 yr) treated by a successful angioplasty (gain > 20% and residual stenosis < 50%) for stable angina pectoris and who had a routine angiographic restudy. The following factors were thus assessed: lipid factors: cholesterol, triglycerides, high density lipoprotein cholesterol, low density lipoprotein cholesterol, apolipoprotein AI, apolipoprotein B; coagulation factors: fibrinogen, antithrombin III, fibrinopeptide A, factor VIII coagulant, factor VIII antigen, protein C; factors of physiological fibrinolysis: plasminogen, alpha 2-antiplasmin, tissue plasminogen activator and euglobulin clot lysis time before and after venous occlusion, plasminogen activator inhibitor before venous occlusion; and factors of platelet release: beta-thromboglobulin, platelet factor 4. Also studied were clinical characteristics: age, gender, diabetes, hypertension, smoking habits, previous myocardial infarction; angiographic data: global extent of coronary artery disease, location of the stenosis in a bend or branch point, complexity of the lesion, initial and residual stenosis and treatment during follow-up. The coronary angiograms were analyzed by a computer-assisted method with automatic edge detection. On angiographic criteria, 6 patients (restenosis group) were judged to have developed a restenosis (30% decrease in diameter and/or return to a 50% stenosis). The other 17 patients (those without restenosis) were considered to have a persistent success. Apart from age (group without restenosis: 55 +/- 6; restenosis group 61 +/- 5, p < 0.04), there were no differences in clinical, angiographic or treatment variables. There were no differences in lipid factors, but significant differences were observed in hemostatic variables: fibrinogen (without restenosis: 3.18 +/- 0.83; restenosis: 3.83 +/- 0.51 milligrams, p = 0.05), tissue plasminogen activator before venous occlusion (without restenosis: 10.9 +/- 26.8; restenosis: 232.5 +/- 371.2 IU, p < 0.04), euglobulin clot lysis time after venous occlusion (without restenosis: 176.5 +/- 100.5; restenosis: 78.6 +/- 40.2 min, p < 0.05) and for marker of the platelet release: platelet factor 4 (without restenosis: 10.8 +/- 7.9; restenosis: 20.5 +/- 7.5 ng/l, p < 0.04). These findings indicate that patients developing restenosis after coronary angioplasty tend to have an imbalance in the prothrombotic-antithrombotic equilibrium prior to the procedure.

8-Methoxypsoralen and longwave ultraviolet irradiation are a novel antiproliferative combination for vascular smooth muscle

BACKGROUND

Smooth muscle cell proliferation plays a major role in the genesis of restenosis after angioplasty or vascular injury. Although the effects of arterial exposure to high-energy radiation sources such as laser have been investigated in detail, the effects on vascular cells of low-intensity radiant energy in combination with photoactive agents have not been extensively characterized. Psoralens are photoactive agents that are known to be well tolerated when used in conjunction with local exposure to ultraviolet light in the A band (UVA) for the treatment of various dermatologic proliferative disorders.

METHODS AND RESULTS

We have investigated the effects of psoralen/UVA (PUVA) exposure on the proliferation of bovine aortic smooth muscle cells. Proliferation and viability were assessed over a 14-day period by trypan blue exclusion counts. Cell cycle effects were evaluated by thymidine incorporation and flow cytometry with DNA quantitation after addition of serum or platelet-derived growth factor B-chain (PDGF-BB) to subconfluent cells synchronized by serum withdrawal. No effect was observed after exposure to 8-methoxypsoralen (8-MOP) at concentrations up to 10 microM or UVA irradiation at energies up to 2.5 J/cm2. Longwave ultraviolet light and 8-MOP were found to behave synergistically as potent inhibitors of DNA synthesis in bovine aortic smooth muscle cells with the EC50 in combination ranging from 7 microM at 0.35 J/cm2 to 0.2 microM at 2.1 J/cm2. Similar antiproliferative effects were obtained by an inverse variation of dose and energy delivered. After serum stimulation, inhibition of DNA synthesis was found with either an immediate or delayed (16-hour) application of PUVA. This effect was independent of subsequent 8-MOP washout. Flow cytometry of cells treated with PUVA at several times after serum stimulation demonstrated for each time point a block in further cell cycle progression for cells in all phases of the cell cycle. Evaluation of [125I]-labeled PDGF and epidermal growth factor (EGF) binding revealed no effect of PUVA on the apparent number or affinity of PDGF binding sites present but did reveal a dose-dependent inhibition by PUVA of EGF binding. This inhibition of EGF binding occurred increasingly at higher PUVA doses than the cell cycle inhibition and accordingly did not appear to represent a critical mechanism for the antiproliferative effect. Cell counting after a single exposure to PUVA (1 microM, 1.5 J/cm2) revealed complete stasis of cell proliferation over a 28-day period without recurrent exposure. No increase in trypan-positive cells was noted over this period.

CONCLUSIONS

PUVA treatment represents a novel method for locally inhibiting proliferation of vascular smooth muscle cells without producing cytolysis.

Coronary restenosis: prospects for solution and new perspectives from a porcine model

Coronary restenosis, a major unresolved problem for percutaneous coronary revascularization procedures, has thus far been resistant to all therapeutic strategies. In part, ineffective treatment or prevention of coronary restenosis may be due to reliance on a conceptualization of the restenosis process that incompletely reflects the pathophysiologic factors associated with neointimal formation after arterial injury. In a porcine coronary restenosis model, three stages of neointimal growth after arterial injury have been identified: an early thrombotic stage, with platelets, fibrin, and erythrocytes; a cellular recruitment stage, with endothelialization and an infiltration by lymphocytes and monocytes; and a proliferative stage, in which smooth muscle cells migrate into and proliferate within the fibrin-rich degenerating thrombus. Evaluation of basic mechanisms responsible for neointimal formation has been possible with this model. In particular, a direct relationship exists between the depth of arterial injury and subsequent neointimal thickness. This relationship can be used for investigating the efficacy of new therapies. Treatment strategies for restenosis should be directed toward interference with the cellular or humoral events that lead to neointimal formation, with the specific goal of decreasing the neointimal volume. These strategies may include delivery of drugs to the site of arterial injury to limit the amount of early mural thrombus or decreasing subsequent cellular recruitment and proliferation as well as synthesis of extracellular matrix.

Occurrence, extent, and implications of pressure waves during excimer laser ablation of normal arterial wall and atherosclerotic plaque

Ablation of atherosclerotic plaque and normal arterial wall was performed using a Xenon-Chloride Excimer laser with a wave-length of 308 nm and a pulse duration of 115 ns. The light was transmitted via a 600 microns bare fibre and adjusted to an energy density of 3.5J/cm2. The acoustic signals generated by the laser pulse were measured with two types of hydrophones consisting of polyvinylidenefluoride with active diameters of 0.3 mm and 0.5 mm and recorded on a dual channel digital storage oscilloscope using either a 0.5 m coaxial cable or a broadband fibre-optic transmission system. Tissue was retrieved from nine cadaver human aortas and macroscopically classified as either normal or calcified atherosclerotic plaque. Histological analysis (Haematoxylin eosin, elastica van Gieson, and immunohistochemical staining) was carried out after the experiments to verify the macroscopic diagnosis and to correlate the acoustic responses with the tissue characteristics. For normal arterial wall, maximum peak pressure was 1.28 MPa +/- 0.85 MPa, rise time 163 ns +/- 43 ns, and pressure increase 8.2k Pa +/- 5.4k Pa/ns. For calcified, atheromatous segments, a maximum peak pressure of 2.02 MPa +/- 1.16 MPa, a rise time of 69.9 ns +/- 25.8 ns, and a pressure increase of 32.3 kPa +/- 21.3 kPa/ns was found. Statistical analysis showed a significant shorter rise time (P < 0.0001) and a higher pressure increase (P < 0.0001) for calcified tissue in comparison to normal arterial wall, whereas maximum pressures alone did not allow a differentiation of tissue characteristics. Several hundred kPa are generated during Excimer laser ablation.(ABSTRACT TRUNCATED AT 250 WORDS)

The importance of acute luminal diameter in determining restenosis after coronary atherectomy or stenting

BACKGROUND

We evaluated native coronary arteries treated by directional coronary atherectomy or balloon-expandable stent placement in an effort to derive a quantitative geometric model relating the luminal diameter immediately after intervention to that present 6 months later. The minimal luminal diameter of each lesion was measured before and immediately after intervention in 102 single Palmaz-Schatz stents and 134 directional atherectomies, 192 (81%) of which had repeat angiographic measurement of minimal luminal diameter 6 months after the intervention. The immediate enlargement in luminal diameter produced by the intervention (acute gain) and the subsequent reduction in luminal diameter from the time of intervention to 6 months of follow-up (late loss) were calculated.

METHODS AND RESULTS

Luminal diameter increased from 0.69 +/- 0.40 mm to 3.11 +/- 0.64 mm (acute gain, 2.41 +/- 0.64 mm) after intervention, providing an immediate postprocedure residual stenosis of 1 +/- 14% relative to a reference diameter of 3.13 +/- 0.65 mm. At 6-month follow-up, the late luminal diameter was 1.97 +/- 0.92 mm (late loss, 1.13 +/- 0.89 mm), yielding a late diameter stenosis of 36 +/- 26%. The restenosis rate (according to the traditional definition of diameter stenosis > or = 50%) was 30%. Multivariable analysis demonstrated that late luminal diameter (p = 0.02), late percent stenosis (p = 0.04), and restenosis (according to a > 50% definition, p = 0.04) were each strongly associated with the luminal diameter present immediately after the procedure. Whereas late luminal diameter was also influenced by reference artery size and the vessel treated (left anterior descending versus right coronary artery), reference vessel size was rejected by the multivariable models of late percent stenosis and binary restenosis after they were adjusted for the effect of postprocedure luminal diameter. Once adjusted for postprocedure luminal diameter, neither late luminal diameter nor late loss was found to be independently determined by which device was used (atherectomy versus stents). Rather, late loss was determined independently by the immediate postprocedure luminal diameter (p = 0.005) and the postprocedure percent stenosis (p = 0.02). Although late loss thus increased with acute gain, the net beneficial effect of increased acute gain was maintained: Late loss was only a fraction (0.47) of acute gain, so the ability of a larger postprocedure luminal diameter to reduce the probability of subsequent restenosis was preserved.

CONCLUSIONS

This quantitative model demonstrates that the late coronary lumen diameter and the probability of restenosis after Palmaz-Schatz stenting or directional atherectomy are influenced strongly by the lumen diameter present immediately after the procedure rather than by the specific device used. Although the influence of a larger acute result on reduced restenosis appears to be well established in this treatment population, the interplay among the multiple other biological influences on restenosis limits the ability to predict the probability of restenosis for the individual patient based on a large acute result alone. Future studies of restenosis, however, can further refine this multivariable quantitative model by adjusting for the effects of other clinical variables, mechanical interventions, or drug therapies in addition to the clear effect of postprocedure luminal diameter.

Angiographic restenosis after successful Wallstent stent implantation: an analysis of risk predictors

Follow-up angiographic study was performed in 86 patients after initially successful Wallstent stent (Medinvent, Lausanne, Switzerland) implantation between April 1986 and October 1990. The stent angiographic restenosis rate was 16% at a mean of 8 months after stenting despite the inclusion of a substantial number of patients at high risk of restenosis after percutaneous transluminal coronary angioplasty (PTCA). Of a total 15 variables analyzed, only suboptimal stent placement was found to be a significant predictor of stent restenosis. Age; gender; baseline New York Heart Association functional class; previous PTCA; indication for stenting; left ventricular ejection fraction; preangioplasty and immediate postangioplasty diameter stenosis severity; stented vessel site, lesional morphology; number, diameter, and length of stents implanted; and the interval between stenting and follow-up angiographic restudy were not significant risk factors of stent restenosis. Our study suggests that intracoronary stent implantation with the Wallstent may be a useful and promising adjunctive option after PTCA, particularly in patients at high risk of restenosis after PTCA. However, because of the significantly enhanced risk of restenosis after suboptimal stent implantation, we strongly recommend the selection and placement of Wallstent stents that adequately cover the entire length of the dilated coronary segment.

Acute outcome of directional coronary atherectomy vs standard balloon angioplasty in de novo left anterior descending stenoses

To assess the immediate outcome of directional coronary atherectomy (DCA) versus standard balloon angioplasty (PTCA) in de novo left anterior descending coronary stenoses, 25 consecutive atherectomies (22 men, 3 women) performed at The Toronto Hospital, between July 1990 and March 1991 were compared with 25 (14 men, 11 women) temporally matched successful angioplasties. Coronary stenoses were analyzed by quantitative arteriography, using the Coronary Measurement System (Leiden, The Netherlands), with estimation of transstenotic hemodynamics by fluid dynamic equations. Before and after procedure qualitative blood flow (TIMI criteria) was also evaluated, as was intimal haziness and coronary dissection. In comparison to PTCA, coronary atherectomy produced less residual minimum stenotic diameter (DCA, 2.75 +/- 0.55 vs PTCA, 1.70 +/- 0.44 mm, p < 0.001), and relative percent diameter stenosis (DCA, 17.9 +/- 10.7 vs PTCA, 34.4 +/- 10.7 percent, p < 0.001), with less transstenotic obstructive gradient (DCA, 0.2 +/- 0.2 vs PTCA, 1.0 +/- 1.5 mm Hg, p < 0.05), and greater estimated stenotic flow reserve (DCA, 4.86 +/- 0.15 vs PTCA, 4.50 +/- 0.48 x baseline, p < 0.05). Coronary atherectomy "normalized" TIMI flow patterns in virtually all patients (DCA, 2.96 +/- 0.20 vs PTCA, 2.72 +/- 0.45, p < 0.05), while creating less intimal haziness (DCA, 10/25 [40 percent] vs PTCA, 23/25 [92 percent], p < 0.01), and coronary dissection (DCA, 6/25 [24 percent] vs PTCA, 16/25 [64 percent], p < 0.05). Therefore, when compared with standard balloon angioplasty, DCA produces less residual stenosis, better transstenotic hemodynamics, while decreasing the frequency of coronary artery damage, in de novo left anterior descending stenoses.

Restenosis after directional coronary atherectomy. Effects of luminal diameter and deep wall excision

BACKGROUND

Deep wall excision during directional atherectomy has been reported in one study to increase the risk of subsequent restenosis. On the other hand, we have observed that the probability of late (6-month) restenosis is reduced by maximizing postprocedure luminal diameter. Although such maximal luminal enlargement by directional atherectomy has not increased procedural complications in our experience, it might well increase the incidence of subintimal (deep wall component) recovery. We performed this study to evaluate the relative influences of luminal enlargement and deep wall component excision on postatherectomy restenosis.

METHODS AND RESULTS

Atherectomy resulted in a 7 +/- 15% residual stenosis with < 0.5% incidence of angiographic vessel perforation. The minimal luminal diameter of each lesion was measured before and after intervention in 413 lesions, 389 (94%) of which had histological analysis of the excised specimens. Specimens were categorized by the deepest layer retrieved: type I (recovery of intima alone, n = 141), type II (recovery of media, n = 79), and type III (recovery of adventitia, n = 65). Repeat angiographic measurement of minimal luminal diameter was available for 329 (80%) segments 6 months after atherectomy. Compared with the 32% restenosis rate for type I excision, there was no increase in restenosis (stenosis > 50%) for type II, type III, or types II+III (p = 0.86). Stratification by vessel characteristics also failed to show any association between restenosis and deep wall component recovery in any subgroup, including native coronary (p = 0.85), left anterior descending coronary artery (p = 0.70), right coronary artery (p = 0.51), saphenous graft (p = 0.78), or prior restenosis lesions (p = 0.98). Paradoxically, the recovery of adventitia (type III excision) was associated with a lower late percent stenosis (p = 0.03) and a trend toward less restenosis (p = 0.11) compared with type I excisions. A multiple logistic regression model was constructed that demonstrated immediate postprocedure luminal diameter (p = 0.02) to be an independent determinant of restenosis. In this model, the presence of deep wall components (type II+III) did not adversely affect (p = 0.86) restenosis, but the recovery of adventitia was associated with an independent trend toward reduced restenosis (p = 0.06).

CONCLUSIONS

The immediate goal of directional atherectomy should be to safely provide the largest lumen possible in order to reduce restenosis. The recovery of deep wall components does not appear to jeopardize the beneficial effect that obtaining a large immediate postprocedure lumen diameter has on reducing the incidence of late restenosis.

Time course and cellular characteristics of the iliac artery response to acute balloon injury. An angiographic, morphometric, and immunocytochemical analysis in the cholesterol-fed New Zealand white rabbit

Evaluation of the response of the arterial vessel wall to acute arterial injury in experimental models has taken on substantial importance because of an increasing interest in angioplasty treatment of human atherosclerotic lesions. In this study, the response of normal arterial vessels to acute balloon injury was studied in 45 iliac artery segments from 24 New Zealand White rabbits fed a 2% cholesterol diet. At specified time points between 1 and 41 days after the initial balloon pullback injury, the iliac arteries were analyzed by angiographic, morphometric, and immunocytochemical techniques. Angiographic measurements indicated progressive compromise of the iliac artery lumen with increasing duration of time from injury. Morphometric measurements showed that intimal area increased from 0.004 +/- 0.01 mm2 3 days after injury to 1.15 +/- 0.30 mm2 34-41 days after injury. Cell line-specific immunocytochemical analysis identified the macrophage as a prominent component of the earliest intimal cellular infiltrate. Smooth muscle cells appeared within the intima 7-9 days after injury. As the intima increased in area, macrophages predominated along the internal elastic lamina aspect of the intimal lesion while smooth muscle cells occupied the portion of the intima adjacent to the lumen. In summary, retrograde balloon pullback injury followed by cholesterol feeding results in progressive arterial luminal narrowing due to a progressively enlarging intimal cellular infiltrate. The temporal and spatial contributions of smooth muscle cell and macrophage components of the developing intimal cellular infiltrate have been characterized.

Clinical characteristics and angiographic follow-up of patients undergoing early or late repeat dilation for a first restenosis

OBJECTIVE

The aim of this study was to analyze the angiographic rate of recurrent restenosis in patients who underwent repeat coronary angioplasty for a first restenosis within 3 months or greater than 3 months after the first procedure.

BACKGROUND

Several studies that have examined risk factors for restenosis after coronary angioplasty have suggested that a short interval between a first angioplasty and a repeat procedure is associated with an increased risk for a second restenosis.

METHODS

Between January 1981 and December 1990, 423 patients underwent a repeat coronary angioplasty procedure because restenosis had occurred at the site of a successful first angioplasty procedure. The clinical characteristics, immediate outcome and angiographic rate of recurrent restenosis were compared in patients who underwent repeat dilation within 3 months (early redilation group, n = 77) or greater than 3 months (late redilation group, n = 346) after the first procedure.

RESULTS

The incidence of unstable angina at the time of the repeat procedure was significantly higher in the patients who underwent early redilation (42% vs. 8%, p = 0.0001). The procedural success rate (95%) and complication rate were similar in both groups. Follow-up angiography was performed in 86% of patients with an initially successful procedure. The incidence of restenosis was significantly higher in the group that underwent early redilation (56% vs. 37%, p = 0.007) and was similar in patients in this group who presented with stable (55%) or unstable (57%) angina.

CONCLUSIONS

Rapidly recurring coronary stenoses have an extremely high rate of restenosis when again treated by coronary angioplasty, irrespective of the clinical presentation at the time of repeat dilation. The outcome in patients with early restenosis who have stable angina might be improved by delaying the repeat procedure.

In vitro validation of three-dimensional intravascular ultrasound for the evaluation of arterial injury after balloon angioplasty

OBJECTIVES

The hypothesis of this study was that three-dimensional ultrasound imaging would facilitate the evaluation of arterial dissection after balloon angioplasty.

BACKGROUND

The presence and extent of arterial dissection occurring at the time of balloon angioplasty may be important predictors of abrupt vessel closure or late restenosis.

METHODS

Forty-one human arterial segments obtained after death were imaged in an in vitro system at physiologic pressure (80 to 100 mm Hg) before and after balloon angioplasty. Images were acquired with a 20- to 30-MHz mechanical intravascular ultrasound imaging system (Cardiovascular Imaging Systems) with a constant pullback technique (1 mm/s). Standard 0.5-in. (1.27-cm) video tapes were used for data storage and later playback for analog to digital conversion. Digitized data were reconstructed to three-dimensional images with use of voxel space modeling. The vessels were opened longitudinally and subjected to pathologic examination, photographed and classified histologically as normal, fibrous or calcified. Dissection was defined as a disruption and separation of components of the arterial wall. The length and depth of arterial dissection were evaluated grossly and microscopically.

RESULTS

Of the 41 arteries studied, 36 (88%) exhibited dissection on pathologic examination after balloon angioplasty. Three-dimensional reconstruction of intravascular ultrasound images identified dissection in 11 (92%) of 12 normal, 8 (100%) of 8 fibrous and 11 (69%) of 16 calcified arteries. Excellent agreement between ultrasound and pathologic findings was achieved in the evaluation of length and depth of dissection for histologically normal and fibrous arteries (kappa = 0.72 to 1.0). When the vessels were severely calcified, the agreement was not as good (kappa = 0.27 to 0.56), particularly in detection of small, non-raised intimal flaps.

CONCLUSIONS

This histopathologic validation study suggests that three-dimensional intravascular ultrasound imaging facilitates the evaluation of both quantitative and morphologic features of arterial dissection induced by balloon angioplasty. The advantage of three-dimensional intravascular ultrasound is its ability to assess the length and morphology of arterial injury over an entire vessel segment.