Mechanisms of acute gain and late lumen loss after atherectomy in different preintervention arterial remodeling patterns

The main mechanism of restenosis after directional coronary atherectomy (DCA) remains obscure. We investigated mechanisms of restenosis after DCA in different coronary artery remodeling patterns. DCA was performed in 51 de novo lesions. The lesions were evaluated by intravascular ultrasound (IVUS) before, immediately after, and 6 months after the procedure. According to the IVUS findings before DCA, we classified the lesions into the following 3 groups: (1) positive (n = 10), (2) intermediate (n = 25), and (3) negative (n = 16) remodeling. We measured lumen area, vessel area, and plaque area using IVUS before DCA, immediately after DCA, and at follow-up. Lumen area increase after DCA was mainly due to plaque area reduction in the positive and intermediate remodeling groups (90 plus minus 15% and 80 plus minus 25% increase in lumen area, respectively), whereas that in the negative remodeling group was due to both plaque area reduction (57 plus minus 22% increase in lumen area) and vessel area enlargement (43 plus minus 33% increase in lumen area). The plaque area increase correlated strongly with late lumen area loss in the positive and intermediate remodeling groups (r = 0.884, p <0.001; r = 0.626, p <0.001, respectively), but the decrease in vessel area was not correlated with lumen area loss. In contrast, both an increase in plaque area and a decrease in vessel area were correlated with late lumen area loss (r = 0.632, p = 0.009; r = 0.515, p = 0.041) in the negative remodeling group. Coronary artery restenosis after atherectomy was primarily due to an increase in plaque in the positive and/or intermediate remodeling groups. However, in the negative remodeling group, late lumen loss might have been caused by both an increase in plaque and vessel shrinkage.     

Morphological effects on in-stent restenosis assessed by intravascular ultrasound imaging.

The purpose of this study was to evaluate the rupture and dissection of the vessel wall immediately after balloon dilatation by intravascular ultrasound (IVUS) imaging and to predict restenosis in patients who underwent subsequent coronary stent implantation. Stent implantation improves the long-term results of coronary angioplasty by reducing lesion elastic recoil and arterial remodeling. However, several studies have suggested that neointimal hyperplasia is the cause of instant restenosis. We recruited 60 patients in whom IVUS studies were performed immediately after successful balloon dilatation and just before stent implantation. We compared IVUS parameters with 6-month follow-up quantitative coronary angiography. This was performed in 51 lesions of 51 patients (85%). Qualitative analysis included assessment of plaque composition, plaque eccentricity, plaque fracture and the presence of dissection. In addition, minimal luminal diameter, percent diameter stenosis, percent area stenosis and plaque burden were quantitatively analyzed. Two morphological patterns after balloon dilatation were classified by IVUS. Type I was defined as absence or partial tear of the plaque without disclosure of the media to lumen (22 lesions). Type II was defined as a split in the plaque or dissection of the vessel wall with disclosure of the media to the lumen (29 lesions). At 6 months follow-up, angiographic restenosis occurred in 17 of the 51 lesions (33%). Restenosis was significantly (p < 0.05) more likely to occur in type II (13/29: 45% incidence) than in type I (4/22: 18% incidence). The assessment of plaque morphology immediately after balloon dilatation and before stent implantation provides important therapeutic and prognostic implications.     

Predictors of vessel remodeling following directional coronary atherectomy.

The purpose of this study was to clarify predictors of vessel remodeling following directional coronary atherectomy (DCA). Negative remodeling after DCA leads to restenosis. However, little is known about the predictors of the vessel remodeling. Serial IVUS was performed in 43 lesions. The vessel remodeling was defined as adaptive if vessel area at follow-up minus postprocedure vessel area was > 0 mm2, or as constrictive if < 0 mm2. Adaptive remodeling occurred in 21 (49%) lesions. Postprocedure percent plaque area was smaller in the adaptive group (32.9% +/- 5.7% vs. 45.5% +/- 8.8%; P < 0.005). At follow-up, vessel area was larger in the adaptive group. However, plaque area was similar between the two groups. As a result, lumen area was larger in the adaptive group. Multivariate analyses showed that postprocedure percent plaque area < 40% was the only predictor of adaptive remodeling (odds ratio, 6.68; P < 0.05).     

Preintervention arterial remodeling affects vessel stretch and plaque extrusion during coronary stent deployment as demonstrated by three-dimensional intravascular ultrasound

The mechanisms of lumen enlargement during stent implantation may be significantly affected by arterial remodeling. To assess effects of lesion remodeling, we performed 3-dimensional intravascular ultrasound (IVUS) analyses in 55 coronary lesions before and after deployment of balloon-expandable stents. Standard quantitative analysis was performed, and arterial remodeling was assessed by the remodeling index (target site divided by mean of proximal and distal reference segment vessel areas), which classified lesions into group A (remodeling index < or =1, negative or intermediate remodeling, n = 40) or group B (remodeling index >1, positive remodeling, n = 15) lesions. Characteristics of the 55 patients and the interventional procedures were similar in the 2 groups. IVUS demonstrated that stenting resulted in increased lumen and vessel dimensions and in a reduced plaque size (p < or =0.001 each) in both group A and group B lesions. The extent of lumen increase inside the stents was almost identical, but resulted from different mechanisms: (1) vessel stretch was greater in group A (p <0.002 at minimum lumen site); (2) plaque compression (or embolization) tended to be greater in group B (p = 0.05, along entire stented segment); (3) plaque redistribution within the stent was observed in both groups (p <0.005 both); and (4) significant (p <0.01) plaque extrusion into the distal reference segment was found in group B only. Thus, the remodeling pattern of coronary lesions has a significant impact on the mechanisms of lumen enlargement during stent deployment. Lesions with positive remodeling show more plaque extrusion into the distal reference and less stent-induced vessel stretch than those with negative remodeling.     

Coronary artery restenosis after atherectomy is primarily due to negative remodeling.

The primary cause of restenosis following directional coronary atherectomy (DCA) remains obscure. "Negative remodeling," a decrease in vessel area, is believed to be more causative than is increase in plaque area. The DCA technique used in these patients, designed to facilitate the removal of plaque, should allow a more precise evaluation of the relative roles of these two mechanisms. Twenty-five patients underwent DCA. In 17, complete angiographic and intravascular ultrasound (IVUS) images were obtained before and after DCA and at follow-up (6 to 9 months). Internal elastic lamina (IEL), lumen, and plaque areas were calculated at preatherectomy, postatherectomy, and follow-up. Postatherectomy, the mean IEL area increased by 32% and the mean plaque area decreased by 51%, resulting in a significant mean increase in lumen area, 500%. At follow-up when compared to postatherectomy, the change in IEL area was variable; however, the mean did not change significantly (p = 0.58). Plaque area change, when standardized for initial vessel size, was small (mean increase 2.8 +/- 3.5%). The mean lumen area did not decrease significantly at follow-up (p = 0.43). A highly significant correlation (r = 0.96) was noted between IEL area change and lumen area at follow-up. In contrast, the correlation between plaque area change and lumen area change over the same period was much less significant (r = 0.64). These data indicate that decrease in IEL area primarily is responsible for restenosis.     

Effect of preintervention remodeling type on subsequent coronary artery behavior after directional atherectomy

To evaluate the influence of preintervention remodeling on subsequent vessel behavior after directional coronary atherectomy (DCA) under intravascular ultrasound (IVUS) guidance, serial (before and after DCA and at 6-month follow-up) IVUS data were analyzed for 246 lesions that were classified into 2 categories: positive remodeling (PR) in 77 lesions versus intermediate or negative remodeling in 169 lesions. Although the 2 groups had similar baseline characteristics, IVUS data showed that the PR group had a greater acute lumen area (LA) gain without an increased late LA loss, resulting in a greater net (acute plus late) LA gain and follow-up LA. This suggests that IVUS-guided DCA may neutralize the negative impact of preintervention PR on late vessel patency.     

Quantitative angiographic and intravascular ultrasound study >5 years after directional coronary atherectomy

Aggressive and optimal directional coronary atherectomy (DCA) using intravascular ultrasound (IVUS) guidance provides favorable outcomes within 1 year. However, no previous data are available on the changes that occur in target lesions for the long term after stand-alone DCA. This study's aim evaluates, using quantitative angiography and intravascular ultrasonography, the natural history of changes that occur in target lesions between short- (about 6 months) and long-term (>5 years) follow-up angiography after stand-alone DCA. Of 186 patients (221 lesions) with successful stand-alone DCA, 48 patients (53 lesions) underwent revascularization within 6 months, and 14 patients subsequently died, leaving a study population of 124 patients (154 lesions). Complete quantitative coronary angiography (QCA) was obtained in 91 patients (101 lesions) and complete serial IVUS assessment was obtained for 38 lesions before and after intervention and during follow-up. From short- to long-term follow-up angiography, the minimal luminal diameter significantly increased (from 2.12 to 2.56 mm; p <0.0001); lesion subgroups with >30% diameter stenosis at short-term follow-up angiography showed significant late regression as assessed by QCA. Serial IVUS assessment revealed that the vessel cross-sectional area did not change (from 17.3 to 17.4 mm(2); p = NS); however the lumen cross-sectional area significantly increased (from 7.3 to 9.5 mm(2); p <0.0001) due to the reduction of plaque plus media cross-sectional area (from 10.0 to 7.9 mm(2); p <0.0001). The change in lumen cross-sectional area correlated with the change in plaque plus media cross-sectional area (r = -0.686, p <0.0001). Target lesions show late regression due to plaque reduction at >5 years after stand-alone DCA.     

Randomized comparison of debulking followed by stenting versus stenting alone for ostial left anterior descending artery stenosis: intravascular ultrasound guidance

Background

Although directional coronary atherectomy (DCA) before stenting has the advantage of combining substantial removal of atheromatous plaque and prevention of elastic recoil, there has been no randomized study to investigate its efficacy in ostial left anterior descending artery (LAD) lesions. This study was aimed to evaluate the effect of DCA followed by stenting on ostial LAD stenosis under the guidance of intravascular ultrasound (IVUS).

Methods

Eighty-six patients with ostial LAD stenoses were randomly assigned to DCA followed by stenting (group I) or stenting alone (group II). Aggressive DCA or optimal stenting was performed in both groups under the guidance of IVUS. The primary end point was angiographic restenosis at 6 months.

Results

Baseline clinical and angiographic characteristics were similar between the 2 groups. The postprocedural minimal lumen diameter was larger in group I than group II (4.0 ± 0.4 mm vs. 3.5 ± 0.5 mm, P < .001). However, the angiographic restenosis rates were not significantly different between the 2 groups (9/32 [28.1%] in group I vs. 11/30 [36.7%] in group II, P = .472). The postprocedural IVUS stent area was the only independent determinant of restenosis by multivariate analysis (odds ratio .61, 95% CI 0.41-0.92, P = .018).

Conclusions

DCA followed by stenting achieved greater lumen gain than stenting alone for ostial LAD stenosis. However, DCA did not improve angiographic restenosis.     

Neointima in coronary stent does not increase during over 1-year in non-restenosed lesion at 6 months follow-up: serial volumetric intravascular ultrasound study

The long-term outcomes of coronary artery stenting have been determined by coronary angiography only with has the limitation of determining stent expansion and neointimal proliferation at long-term follow-up. Volumetric intravascular analysis has the potential to evaluate the morphology and distribution of neointima longitudinally after coronary artery stenting. We used three-dimensional intravascular ultrasound (3-D IVUS) to evaluate serial changes in stent and neointimal volumes for over 1-year in 9 patients who did not exhibit angiographic restenosis at 6-month follow-up. Volumetric analysis by a validated Netra 3-D IVUS system was performed pre- and post-intervention, at 6-month follow-up (FU1), and at over one-year follow-up (FU2). Lumen volume in the stented lesions increased significantly after intervention, and the increase persisted until FU2. There were no significant changes in stent volume between just after stent implantation and at FU2. Neointimal volume within the stents did not change from FUI to FU2 (FU1; 38.4 +/- 9.0 mm3 vs FU2; 33.8 +/- 10.3 mm3). In 33% (3/9) of all lesions, neointimal volume increased between from 6-months to over 1-year after stent implantation. Neointimal distribution after stenting seemed to be almost equal and unrelated to the plaque burden at pre-intervention. Neointimal volume within the stents did not increase and stent volume did not change over the 1st-year in patients who did not exhibit angiographic restenosis at 6-months.     

Effects of lipid-lowering therapy on coronary artery remodeling

BACKGROUND: Although lipid-lowering therapy affects the luminal size of atherosclerotic coronary arteries the role of vascular remodeling has not been systematically studied. DESIGN/METHODS: Serial three-dimensional volumetric intravascular ultrasound (IVUS) was used to study remodeling, which was defined as changes in arterial size independent of or dependent on changes in plaque size. Using an automated contour detection algorithm, a 1 mm segment of a moderate atherosclerotic lesion at the site of the maximal plaque volume at baseline was analysed. After 12 months the relationship between the absolute change in vessel volume and plaque volume was calculated in 99 patients. There was a significant relationship between changes in plaque and vessel volume, independent of plaque progression or plaque regression (decrease in plaque size, r = 0.60, P < 0.0001 and increase in plaque size, r = 0.49, P < 0.0008, respectively; the slopes of the regression equation were 1.03 and 0.80). By means of an analysis of covariance we tested whether the regression slopes were equal between groups of patients as defined by the low-density lipoprotein-cholesterol (LDL-c) level achieved with lipid-lowering therapy. RESULTS: Only patients with plaque progression and a LDL-c level < 100 mg/dl had a significantly smaller slope than patients with a LDL-c level > 100 mg/dl (-0.14 compared with 1.14, P = 0.003 ), indicating diminished coronary remodeling. CONCLUSIONS: Serial volumetric IVUS confirms the existence of both positive and negative remodeling in relation to an increase and decrease in plaque volume. It has been shown that the outward remodeling process is diminished in patients with plaque progression and intensive lipid-lowering therapy.     

Preventive mechanisms and effects of pemirolast potassium on restenosis after percutaneous transluminal coronary angioplasty: serial coronary angiography and intravascular ultrasound studies

Pemirolast potassium, an antiallergic agent, has preventive effects against restenosis after percutaneous transluminal coronary angioplasty (PTCA). This study investigated the mechanism of the preventive effects of pemirolast on restenosis using serial intravascular ultrasound (IVUS). Initial elective PTCA was performed in consecutive 106 patients from March 1996 through August 1997. Patients with type C lesions or graft stenosis were excluded from the study. A total of 97 patients with 110 lesions, 48 patients (56 lesions) in the pemirolast treated group and 49 patients (54 lesions) in the control group were analyzed. Restenosis was defined as a diameter stenosis of > or = 50% at follow-up study. Patients in the pemirolast group received 20 mg/day from the morning after angioplasty until the time of follow-up (mean 6 months). The lumen cross-sectional area, vessel area, plaque area, and % plaque area were measured by quantitative coronary ultrasound and compared after PTCA and at follow-up between the patients without restenosis in the pemirolast (28 lesions) and control (27 lesions) groups. There was no significant change in baseline characteristics between the 2 groups. Restenosis rate per lesion was significantly lower in the pemirolast group than in the control group (23.2% vs 44.4%, p < 0.05, respectively). After angioplasty and at follow-up study, there was no difference in lumen and vessel cross-sectional areas between the 2 groups. However, plaque and % plaque area in the pemirolast group were smaller than in the control group at follow-up study (8.9 +/- 2.3 vs 11.8 +/- 3.5 mm2, p < 0.005, 56.0 +/- 9.0% vs 64.0 +/- 10.4%, p < 0.005, respectively). These results suggest that suppression of neointimal hyperplasia is the preventive mechanism of pemirolast against restenosis after angioplasty. Pemirolast may be more effective against restenosis after coronary stenting.     

New developments in intravascular ultrasound

Intravascular ultrasound (IVUS) is a dynamic imaging modality that provides real-time in vivo visualization of atherosclerosis and other vascular pathology. The tomographic image presentation of IVUS permits detailed assessment of plaque morphology and its corresponding responses to interventional therapy. IVUS studies have confirmed vascular remodeling in vivo, have proposed a high-pressure stent implantation strategy and have shown two key mechanisms of restenosis after angioplasty: plaque proliferation and vessel shrinkage (negative remodeling). IVUS also provides accurate quantitative information regarding lumen size, vessel size and plaque burden. These observations, essential to achieving improved outcomes, have drastically changed the understanding of atherosclerotic artery disease and interventional procedures. IVUS has matured into an essential complement to daily peripheral and coronary interventional practice and is routinely incorporated as part of the interventional arsenal in the catheterization laboratory. A variety of new imaging techniques are currently being designed and tested. These include combined therapeutic devices, further miniaturization, 3-D applications and tissue characterization. These techniques may evolve to provide increased favorable clinical outcomes and more accurate information of vessel geometry and plaque composition.     

Comparison of Restenosis Rate in Various Devices for Coronary Intervention: Analysis Using Vessel Diameter and Lesion Length

The purpose of this study was to retrospectively compare the restenosis rates related to vessel diameter and lesion length among plain old balloon angioplasty (POBA), cutting balloon (CB) angioplasty, Palmaz-Schatz (PS) stems, Gianturco-Roubin (GR) stents, and directional coronary atherectomy (DCA). In 909 consecutive successfully treated cases, target lesion dimensions were divided into diameters of ± 2.5 mm and lengths of ± 20 mm to compare the restenosis rates obtained by the individual devices. Quantitative angiographic analysis was performed before the procedure, after the procedure, and at FU angiography at a mean FU time of 6 ± 3 months. Restenosis was defined as %DS > 50 at FU angiography. Patients with acute myocardial infarction, chronic total occlusions, left main lesions, ostial as well as venous graft lesions, severe calcifications, severe coronary thrombosis, and bleeding complications were excluded. The overall restenosis rate was 32%, with the CB it was 29%, with the PS stent it was 27%, and with DCA it was 39%. Each of these restenosis rates was significantly lower than that with POBA. The overall restenosis rate with short lesions at small vessels was 35%, while CB angioplasty yielded 29%, being significantly lower compared to that obtained by POBA. The overall restenosis rate with long lesions at small vessels was 53%. With those lesions there was no significant difference among the devices. The overall restenosis rate with short lesions at large vessels was 27%, with CB angioplasty it was 24%, with the PS stent it was 22%, and with DCA it was 25%. These restenosis rates were significantly lower compared to POBA. With long lesions at large vessels, the overall restenosis rate was 44%. In this subgroup, there was again no significant difference among the devices. Our study suggests that restenosis rates with short lesions are lower after CB angioplasty, stenting, and DCA, when compared to POBA. However, in the presence of long lesions, no difference was found among the devices.     

Intravascular ultrasound for evaluation of initial vessel patency and early outcome following directional coronary atherectomy

Elastic recoil and thrombus formation may potentially occur following directional coronary atherectomy (DCA) confounding the assessment of late vascular remodeling. Since intravascular ultrasound (IVUS) data on early outcome of DCA is not available, we used IVUS to investigate whether elastic recoil or thrombus formation can affect early (4 hr) outcome. Quantitative coronary angiography (QCA) and IVUS were performed in high-grade coronary lesions in 32 consecutive patients before, immediately after, and 4 hr after DCA. Late clinical follow-up was obtained after a maximum interval of 2 years. Significant acute elastic recoil was observed by both IVUS (19% ± 14%) and QCA (19% ± 12%), but there was no further recoil after 4 hr. DCA reduced plaque area by 51% ± 13%, an effect that was stable after 4 hr, indicating the absence of relevant thrombus formation. Residual area stenosis by IVUS was not related to the occurrence of late clinical events (n = 8). Mechanical recoil or thrombus formation do not hamper initial lumen gain achieved by DCA. Although QCA significantly underestimated residual plaque burden after DCA when compared to IVUS, the degree of residual area stenosis did not identify patients suffering from cardiac events on follow-up.Cathet. Cardiovasc. Intervent. 47:14–22, 1999. © 1999 Wiley-Liss, Inc.     

Extent and distribution of in-stent intimal hyperplasia and edge effect in a non-radiation stent population

Intimal hyperplasia within the body of the stent is the primary mechanism for in-stent restenosis; however, stent edge restenosis has been described after brachytherapy. Our current understanding about the magnitude of in vivo intimal hyperplasia and edge restenosis is limited to data obtained primarily from select, symptomatic patients requiring repeat angiography. The purpose of this study was to determine the extent and distribution of intimal hyperplasia both within the stent and along the stent edge in relatively nonselect, asymptomatic patients scheduled for 6-month intravascular ultrasound (IVUS) as part of a multicenter trial: Heparin Infusion Prior to Stenting. Planar IVUS measurements 1 mm apart were obtained throughout the stent and over a length of 10 mm proximal and distal to the stent at index and follow-up. Of the 179 patients enrolled, 140 returned for repeat angiography and IVUS at 6.4 +/- 1.9 months and had IVUS images adequate for analysis. Patients had 1.2 +/- 0.6 Palmaz-Schatz stents per vessel. There was a wide individual variation of intimal hyperplasia distribution within the stent and no mean predilection for any location. At 6 months, intimal hyperplasia occupied 29.3 +/- 16.2% of the stent volume on average. Lumen loss within 2 mm of the stent edge was due primarily to intimal proliferation. Beyond 2 mm, negative remodeling contributed more to lumen loss. Gender, age, vessel location, index plaque burden, hypercholesterolemia, diabetes, and tobacco did not predict luminal narrowing at the stent edges, but diabetes, unstable angina at presentation, and lesion length were predictive of in-stent intimal hyperplasia. In a non-radiation stent population, 29% of the stent volume is filled with intimal hyperplasia at 6 months. Lumen loss at the stent edge is due primarily to intimal proliferation.     

Impact of moderate lesion calcium on mechanisms of coronary stenting as assessed with three-dimensional intravascular ultrasound in vivo

Axial plaque redistribution is an important mechanism of lumen enlargement after stenting of noncalcified lesions. To assess effects of lesion calcification on mechanisms of coronary stenting, we analyzed 55 lesions with noncircumferential calcification with 3-dimensional intravascular ultrasound (IVUS) (standard qualitative and quantitative analyses) before and after implantation of balloon-expandable stents. Thirty-two plaques (58%) showed arcs of calcium <120 degrees of vessel circumference (group A), whereas 23 lesions (42%) contained arcs of calcium > or =120 degrees of vessel circumference (group B). In the entire cohort of 55 lesions, as well as groups A and B, which were studied separately, both single-slice IVUS analysis (performed at minimum lumen site before intervention) and mean stented segment IVUS analysis showed an increase in lumen and vessel area and a decrease in plaque area (p <0.001). The magnitude of lumen and vessel increase and of plaque decrease was similar in both groups. Group A lesions showed significant plaque extrusion into the distal reference segment that was not observed in group B (increase in plaque area of 1.3 +/- 1.9 vs 0.1 +/- 2.0 mm(2), p <0.04). Stenting did not alter plaque area of the proximal reference segment in either group. In addition, there was an increase in vessel area of the distal reference of both groups, indicating that stent-induced vessel expansion observed within the lesion also affected the distal reference. Thus, longitudinal plaque redistribution and vessel expansion contribute to increased lumen dimensions during stenting of lesions with varying amounts of calcium; however, marked plaque extrusion was found only in lesions with a calcium arc of <120 degrees.     

Serial intravascular ultrasonic study of outcomes of coronary culprit lesions with plaque rupture following bare metal stent implantation in patients with angina pectoris

Coronary culprit lesions with plaque rupture (PR) have been treated with different coronary interventions. However, it is unknown whether the presence of PR affects the restenotic process after coronary intervention. One hundred forty-two patients undergoing coronary bare metal stent implantation were enrolled in the present retrospective analysis. Case selection was based on availability of intravascular ultrasound (IVUS) and quantitative coronary angiographic examinations at baseline (before and after intervention) and at follow-up. Serial comparative analyses included qualitative and quantitative features of the culprit lesion and reference segments. PR was defined as an intraplaque cavity in communication with the lumen in the presence of a residual, disrupted cap. Patients were categorized according to the presence/absence of PR. Pre-interventional IVUS detected PR in 54 patients (38%). Baseline patient demographics were similar between the +PR and -PR groups. Quantitative IVUS analysis showed higher rates of positive remodeling and larger vessel and plaque areas in the +PR compared with -PR lesions (p <0.001 for all). At follow-up (7.2 +/- 2.6 months), no statistically significant difference was observed between the 2 groups in quantitative coronary angiographic or IVUS measurements. In conclusion, culprit lesions with PR exhibited larger plaque mass and higher rates of positive remodeling at preintervention IVUS examination. However, when treated with bare metal stents, the absence/presence of preintervention PR was not found to affect the rate or severity of in-stent restenosis in these culprit lesions.     

Intravascular ultrasonography in the evaluation of results of coronary angioplasty and stenting

The main advantage of intravascular ultrasonography (IVUS) over angiography in assessing the effect of coronary interventions is the ability of IVUS to directly visualize the vessel wall. IVUS often reveals a high residual plaque burden after angiographically successful angioplasty, and this can motivate the operator to use additional, more aggressive measures in an attempt to increase lumen dimensions. Studies using IVUS imaging before and after balloon angioplasty have shown that luminal gain after percutaneous transluminal coronary angioplasty (PTCA) results from a combination of plaque reduction and vessel wall stretch. Minimal luminal area and residual area stenosis after PTCA and stent deployment, as measured by IVUS, have been shown to be predictors of restenosis. IVUS studies have pointed to vessel shrinkage, not intimal hyperplasia, as the main mechanism of restenosis after PTCA. IVUS guidance of stent deployment has often revealed inadequate stent expansion despite optimal results on angiography, leading to high-pressure stent deployment with significant additional luminal gain. Restenosis rates may be lower with IVUS-guided stent deployment.     

Impact of deep vessel wall injury and vessel stretching on subsequent arterial remodeling after balloon angioplasty: a serial intravascular ultrasound study

Background Arterial remodeling has been shown to be responsible for lumen narrowing after nonstent interventions. Methods To examine the impact of deep vessel wall injury (DI) after balloon angioplasty on the subsequent vessel remodeling process, we performed serial intravascular ultrasound (IVUS) analysis in 47 native coronary artery lesions that underwent balloon angioplasty. An IVUS study was performed before and after balloon angioplasty and repeated at follow-up. Vessel and lumen area were measured at the narrowest site before intervention. Plaque area was calculated as vessel area minus lumen area. DI was defined as the presence of plaque/vessel wall fracture deep in the medial layer (sonolucent zone by IVUS) after angioplasty. Results After angioplasty, DI was present in 18 (38%, DI group) and absent in 29 (62%, non-DI group) of lesions. During follow-up, changes in vessel area in the DI group were significantly larger than in the non-DI group (P = .007). There were no significant differences in changes in plaque area. A trend toward greater late lumen loss was observed in the non-DI group (P = .05). In the DI group, changes in lumen area correlated better with changes in vessel area (r = 0.81, P < .0001) than with changes in plaque area (r = 0.32, P = .20). However, in the non-DI group, changes in lumen area correlated with changes in plaque area (r = −0.55, P = .002), but not with changes in vessel area (r = 0.30, P = .11). Conclusions Deep vessel wall injury after balloon angioplasty is associated with the magnitude of the subsequent vessel remodeling process. The differences in the remodeling process may have implications regarding adjunctive therapies to prevent restenosis after balloon angioplasty. (Am Heart J 2002;144:323-8.)     

Mechanism of luminal gain with plaque excision in atherosclerotic coronary and peripheral arteries: assessment by histology and intravascular ultrasound

OBJECTIVES: Using intravascular ultrasound (IVUS) and histology, the purpose of this study was to evaluate the occurrence of arterial wall overstretch and Dotter effect following revascularization with a plaque excision (PE) catheter compared with balloon angioplasty. BACKGROUND: Previous studies have demonstrated the safety and feasibility of plaque excision for the treatment of de novo coronary and peripheral atherosclerotic disease. However, whether mechanical vessel dilatation related to catheter insertion contributes to gains in the final luminal diameter is uncertain. METHODS: Treatment with PE was assessed in both a porcine model (6 lesions treated with balloon angioplasty or PE) using histology and in humans with IVUS. In the latter part of the study, IVUS study was performed before and immediately following PE in 21 patients with either coronary artery disease (N = 13) or femoral artery disease (N = 8). Ultrasound measures in the femoral artery group were then compared with a control group of atherosclerotic lesions treated with conventional angioplasty that was matched according to lesion location and vessel diameter. RESULTS: Among individuals with coronary and peripheral arterial lesions treated with PE, the relative increases in luminal area secondary to reductions in plaque volume were 89% and 83%, respectively, with minimal increase in vessel diameter. In contrast, balloon angioplasty was associated with significantly greater vessel expansion and less plaque volume reduction. Vessel dissection also tended to occur less frequently and to a lesser extent with PE. CONCLUSIONS: Improvement in luminal dimensions using PE is principally due to a reduction in plaque volume rather than mechanical vessel expansion. The potential to increase luminal area while minimizing arterial dissection and barotrauma merits further clinical study with this method of revascularization.