Histologic findings in specimens obtained by percutaneous directional coronary atherectomy

Intravascular Ultrasound Guidance for Peripheral Vascular Interventions

Intravascular ultrasound (IVUS) imaging during peripheral endovascular interventions adds important information regarding the distribution of disease by providing controlled measurements of the cross-sectional area of the vessel lumen and wall prior to and following procedures. IVUS is useful in determining the mechanism and efficacy of balloon angioplasty, in guiding atherectomy devices, and in assuring appropriate placement of intravascular stents. The incorporation of an IVUS element into catheter-based interventional devices may improve the immediate and long-term results of endovascular interventions by decreasing complications from dissection and perforation of the arterial wall. Combined IVUS-stent prototype catheters are being developed to enable imaging and deployment simultaneously. Similar devices are being explored to enhance expedient, precise delivery of endoluminal grafts. Future studies of endovascular techniques should include IVUS, when possible, to accurately quantitate the initial efficacy of devices and to determine the nature and distribution of recurrent lesions.

Animal models of restenosis

Percutaneous transluminal coronary angioplasty is a widely used technique for recanalizing arteries that are occluded by atherosclerotic plaque, but its usefulness is limited by the occurrence ofrestenosis in a high proportion of patients. The development of new therapies for this currently intractable problem will be facilitated by the use of animal models of restenosis that are predictive of drug efficacy in humans. Two approaches for improving predictivity can be identified. In the first of these, the goal is to maximize the anatomical and procedural resemblance of the model to humans. The second approach seeks to maximize the pathophysiological and molecular biological resemblance of the model to humans. Tangible progress is being made toward the first goal, but lack of understanding of the basic biology of human restenosis is hampering progress toward the second.

Increased intimal apoptosis in coronary atherosclerotic vessel segments lacking compensatory enlargement

OBJECTIVES

In a histopathologic study, we assessed the balance of cell proliferation and apoptosis by counting the number of apoptotic and proliferating cell nuclear antigen-positive cells in freshly harvested atherectomy specimens from 34 patients.

BACKGROUND

Remodeling of human coronary arteries is an adaptive process that alters vascular lumen size.

METHODS

Intravascular ultrasound was performed prior to atherectomy. Total vessel area (area within the external elastic lamina [EEL]), lumen area and plaque area were measured at the region of interest (ROI), and at a proximal and distal reference segment, utilizing the formula Delta(%)=100x(ROI-reference segment)/reference segment. Positive arterial remodeling (R+) resulting in luminal expansion was defined as DeltaEEL >10%. Absence of remodeling (0 < DeltaEEL <10%) and constrictive arterial remodeling (DeltaEEL <0) were considered as neutral remodeling (R0) and negative remodeling (R-), respectively.

RESULTS

In R- lesions, apoptotic indices (APO) were significantly elevated (17.17 +/- 2.19%) compared with R+ lesions (4.89 +/- 1.7%; p = 0.0007). In a rabbit iliac percutaneous transluminal coronary angioplasty model intimal apoptosis was increased four weeks after balloon angioplasty injury (APO 8.8 +/- 0.03%) compared with contralateral untreated segments (APO 3.0 +/- 0.04%, n = 6). Lesions with an EEL/intimal area <3.0 showed significantly more intimal apoptosis than untreated lesions (p = 0.02).

CONCLUSIONS

The data indicate that constrictive remodeling of atherosclerotic coronary lesions is associated with increased apoptosis of intimal cells. We speculate that increased apoptosis is due to extensive plaque healing after episodes of symptomatic or asymptomatic plaque rupture.

Regulated expression of the BTEB2 transcription factor in vascular smooth muscle cells: analysis of developmental and pathological expression profiles shows implications as a predictive factor for restenosis

BACKGROUND

We have previously shown BTEB2, a Krüppel-like zinc finger transcription factor, to regulate expression of the SMemb/NMHC-B gene, which has been implicated in phenotypic modulation of smooth muscle cells (SMCs). The present study was done to assess the developmental and pathological expression profiles of BTEB2 and to further evaluate the clinical relevance of BTEB2 expression in human coronary artery disease.

METHODS AND RESULTS

Immunohistochemistry showed developmentally regulated expression of BTEB2 with abundant expression in fetal but not in adult aortic SMCs of humans and rabbits. In balloon-injured aortas, predominant expression of BTEB2 was seen in neointimal SMCs. Atherectomy specimens obtained from primary and restenotic lesions showed predominant expression of BTEB2 to stellate SMCs. The incidence of restenosis in primary lesions was significantly higher in lesions containing BTEB2-positive cells than in lesions without (55.6% versus 25.0%, P:=0.01).

CONCLUSIONS

The present study shows that BTEB2 expression is developmentally and pathologically regulated. BTEB2 is preferentially expressed in dedifferentiated or activated SMCs. Examination of human coronary artery specimens suggests that primary lesions containing BTEB2-positive cells are associated with higher risk of restenosis than BTEB2-negative lesions. These results suggest that BTEB2 can serve as a molecular marker for phenotypic modulation of vascular SMCs.

Replication in restenotic atherectomy tissue

Previously, we demonstrated that replication in restenotic coronary atherectomy specimens was an infrequent and modest event. In general, this data was interpreted with caution, as immunocytochemistry for the proliferating cell nuclear antigen (PCNA) was used to subjectively assess proliferation and most of the tissue specimens were resected more than 3 months after the initial interventional procedure. The purpose of the present study was to use a more sensitive method of detecting replication, in situ hybridization for histone 3 (H3) mRNA, to determine the replication profile of human directional atherectomy specimens. Restenotic directional coronary atherectomy specimens from lesions that had undergone an interventional procedure within the preceding 3 months were studied. In addition, larger atherectomy specimens from peripheral arterial lesions were assessed to ensure that pockets of replication were not being overlooked in the smaller coronary specimens. We found evidence for replication in tissue resected from 2/17 coronary and 9/12 peripheral artery restenotic lesions. In contrast, 3/11 specimens resected from primary lesions of peripheral arteries also expressed H3 mRNA. We estimated that the maximum percentage of cells that were replicating in restenotic coronary, restenotic peripheral and primary peripheral artery tissue slides to be <0.5, < or =1.2 and <0.01%, respectively. Replication was found in tissue specimens resected both early and late after a previous interventional procedure. For specimens with >15 replicating cells per slide we found high levels of focal replication. Therefore, cell replication, as assessed by the expression of H3 mRNA, was infrequent in restenotic coronary artery specimens, whereas peripheral restenotic lesions had more frequent and higher levels of replication regardless of the interval from the previous interventional procedure. For all specimens the percentage of cells that were replicating was low, however focal areas with relatively high replication indices were presented. Although replication was more abundant in restenotic lesions it does not appear to be a dominant event in the pathophysiology of restenosis.

Restenosis following angioplasty in the swine coronary artery is inhibited by an orally active PDGF-receptor tyrosine kinase inhibitor, RPR101511A

BACKGROUND

Platelet-derived growth factor (PDGF), a purported mediator of arterial response to injury, stimulates proliferation, chemotaxis, and matrix production by activation of its membrane receptor tyrosine kinase. Because these activities underlie restenosis, inhibition of the PDGF-receptor tyrosine kinase (PDGFr-TK) is postulated to decrease restenosis.

METHODS AND RESULTS

RPR101511A is a novel compound which selectively and potently inhibits the cell-free and in situ PDGFr-TK and PDGFr-dependent proliferation and chemotaxis in vascular smooth muscle cells (VSMC). To evaluate the effect of RPR101511A (30 mg. kg-1. d-1 BID for 28 days following PTCA) on coronary restenosis, PTCA was performed in hypercholesterolemic minipigs whose left anterior descending (LAD) coronary artery had been injured by overdilation and denudation, yielding a previously existing lesion. Angiographically determined prePTCA minimal lumen diameters (MLD) were similar in vehicle and RPR101511A-treated pigs (1.98+/-0.09 versus 2.01+/-0.08 mm) and increased to the same extent in the 2 groups following successful PTCA (2.30+/-0.06 versus 2.52+/-0.13). At termination, there was an average 50% loss of gain in the vehicle-treated group but no loss of gain with RPR101511A (2.16+/-0. 05 versus 2.59+/-0.11, P<0.001). Morphometric analysis of the LAD showed that RPR101511A caused a significant decrease in total intimal/medial ratio (0.96+/-0.58 versus 0.67+/-0.09, P<0.05).

CONCLUSIONS

RPR101511A, which acts by inhibition of the PDGFr-TK, completely prevented angiographic loss of gain following PTCA and significantly reduced histological intimal hyperplasia.

Studies on the histogenesis of myxomatous tissue of human coronary lesions

Myxomatous tissue is a characteristic component of human coronary artery lesions, found more often in restenotic lesions. It represents a bulky accumulation of stellate-shaped cells of unknown histogenesis that are embedded in a loose stroma. We analyzed 64 atherectomy specimens containing substantial amounts of myxomatous tissue by using immunohistochemistry, in situ hybridization, and electron microscopy techniques. Stellate cells represented a heterogeneous population, sharing features of smooth muscle cells (SMCs), macrophages, as well as antigen-presenting dendritic cells. Like quiescent medial SMCs, the stellate cells in all specimens expressed high levels of SM alpha-actin message and protein and showed heterogeneity with respect to heavy-chain myosin, SM22, desmin, and vimentin. Ultrastructurally, stellate cells resembled SMCs, with some peculiarities that distinguish them from both differentiated and dedifferentiated SMCs. In contrast to quiescent SMCs, the stellate cells expressed high levels of acidic fibroblast growth factor mRNA and protein similar to cells of monocyte/macrophage lineage. However, stellate cells did not express the marker of mature macrophages, HAM56, and were heterogeneous with respect to CD68. Moreover, unlike SMCs, the stellate cells bore some of the major phenotypic markers of dendritic cells: they were S100-positive and showed various reactivity with respect to CD1a and human leukocyte antigen (HLA)-DR. Invasion of myxomatous tissue with CD45RO-positive T lymphocytes was correlated with strong expression of CD1a in these specimens. Stellate cells also expressed a pericyte marker, high-molecular-weight melanoma-associated antigen. We conclude that stellate cells of myxomatous tissue represent a specific phenotype of mesenchymal cells (possibly pericytes), which is activated to express some markers of antigen-presenting cells. These findings suggest involvement of the stellate cells in a local immune response.

Photochemically induced endothelial injury in the mouse as a screening model for inhibitors of vascular intimal thickening

We have established a mouse model of intimal thickening and assessed its suitability for experimental studies of intimal thickening. Neointimal formation was observed after endothelial injury by photochemical reaction between transluminal green light and systemically administered rose Bengal, which represents a nonmechanical approach to vessel wall denudation. Intimal thickening began 7 days after endothelial injury, reached a maximum after 21 days, and then remained unchanged for as long as 42 days. Furthermore, as a consequence of neointimal proliferation, the luminal area gradually decreased. The cells in the neointimal layer were identified as smooth muscle cells by immunohistochemical staining with an alpha-actin-specific antibody. Extracellular matrix deposition in the neointima was markedly increased beyond 14 days after injury. Smooth muscle cell proliferation, as measured by pulse labeling of 5-bromo-2'-deoxyuridine, was identified initially in the media 2 days after vessel wall denudation, with the proliferative activity's shifting almost exclusively to the neointima within 7 days. Endothelial regeneration, as indicated by Evans blue staining, was complete within 21 days after injury. To assess the suitability of this model for experimental studies on intimal thickening, the effect of tranilast, an antiallergy drug with a broad spectrum of pharmacological actions on intimal thickening, was investigated. Tranilast (100 mg x kg(-1) x d(-1) p.o.) significantly (P<0.05) reduced smooth muscle cell proliferation in the neointima and media 7 days after injury and neointimal formation 21 days after injury in treated mice compared with vehicle-treated mice. This simple experimental mouse model is suitable for studying factors promoting or inhibiting intimal thickening after endothelial injury and for developing therapeutic strategies against intimal thickening.

Electron microscopic studies of phenotypic modulation of smooth muscle cells in coronary arteries of patients with unstable angina pectoris and postangioplasty restenosis

BACKGROUND

Proliferation and matrix protein secretion of coronary smooth muscle cells (SMCs) have been suggested as one of the mechanisms responsible for the development of postangioplasty restenosis and an alternative cause of unstable angina. Phenotypic modulation of SMCs may produce a pool of cells potentially responsive to growth stimulation that can synthesize abundant extracellular matrix. This study tested the hypothesis that phenotypic modulation of SMCs occurred during the evolution of postangioplasty restenosis and unstable angina.

METHODS AND RESULTS

The SMCs of coronary atherectomy specimens from 24 patients were identified under electron microscope. Volume fractions of synthetic organelles (VFSOs) and other features related to phenotypic modulation of SMCs were measured. The results showed that the VFSO in SMCs from 5 patients with unstable angina (group 2) resembled those from 9 patients with postangioplasty restenosis (group 3; 0.42 +/- 0.13 versus 0.36 +/- 0.10; P = NS), and both were significantly higher than those from 6 patients with stable angina (group 1; 0.21 +/- 0.11). Four patients with restenosis lesions who underwent angioplasty > 6 months ago (group 4) also had a low VFSO in SMCs (0.19 +/- 0.05). This value was significantly less than those in groups 2 and 3 (P < .05) but similar to that in group 1.

CONCLUSIONS

The coronary lesions from patients with unstable angina resembled those from patients with postangioplasty restenosis in terms of the phenotypic modulation and VFSO in SMCs. Our findings therefore suggest that after phenotypic modulation, the SMCs may become responsive to growth stimulation, with an ability to massively proliferate and synthesize abundant extracellular matrix. These processes may lead to plaque expansion and eventually to the development of unstable angina and restenosis.

Coronary artery and saphenous vein graft remodeling: a review of histologic findings after various interventional procedures--Part VI

Catheter balloon angioplasty is a well accepted form of nonsurgical treatment of acutely and chronically obstructed coronary artery vessels. It is also the centerpiece for various new intervention techniques. Their morphologic effects on the site of obstruction has been termed "remodeling." Part VI of this six-part series focuses on atherectomy and restenosis tissue obtained by atherectomy procedures.

Effect of coronary artery size on the prevalence of atherosclerosis

To investigate the effect of coronary artery size on the prevalence of atherosclerosis, we measured the diameters of the major coronary arteries prospectively in 884 consecutive patients referred for coronary arteriography. For each artery, we assigned patients to 3 groups: group S (small) and group L (large) with diameters >1SD smaller and larger, respectively, than the mean; and group A (average), with diameters within 1SD of the mean. As specified during study design, we compared the frequency of lesions > or = 50% diameter stenosis in groups S and L for each artery. We adjusted for relevant covariates by performing logistic regression on data from all 884 patients with coronary diameter entered as a continuous variable. In group S versus L, respectively, the frequency of > or = 50% lesion was 6.5% versus 2.4% (p = 0.13) in the left main artery; 61.3% versus 35.8% (p = 0.0001) in the right coronary artery; 58.1% versus 40.7% (p = 0.008) in the left anterior descending artery, and 47.4% versus 22.2% (p = 0.0001) in the circumflex artery. Multivariate analysis showed that coronary diameter was a significant independent predictor of lesions in the right coronary artery (p = 0.000001), left anterior descending artery (p = 0.001), and circumflex artery (p = 0.0002) and nearly significant in the left main artery (p = 0.077). Thus, small coronary artery size may be a risk factor for atherosclerosis.

Analysis of atherosclerotic plaques obtained by coronary atherectomy: Foam cells correlated positively with subsequent restenosis

Restenosis following coronary intervention is a complex process the mechanisms of which remains mostly unknown. Tissue obtained by atherectomy is an important means to study restenosis. Previous studies on atherectomy-retrieved tissue have not identified histologic features that correlate with restenosis. We performed an histopathologic evaluation on atherosclerotic plaque tissue obtained by atherectomy from 58 patients, all of whom had a 6-month angiographic follow-up. We identified macrophages and lymphocytes and localized tumor necrosis factor-α expression in the tissue by immunohistochemistry. Histopathology was correlated with late angiographic outcomes. Of 10 histologic features evaluated in the plaque tissue, only the presence of foam cells, identified in paraffin sections, correlated positively with restenosis (p = 0.04). Immunohistochemistry showed that macrophages (p = .07), tumor necrosis factor-α (p = .07), and lymphocytes (p = .14) were more prominent, but not significantly so, in lesions from patients with foam cells and restenosis than in lesions from patients without foam cells or restenosis. Thus the presence of foam cells in primary lesions obtained by atherectomy as identified in paraffin-embedded tissue appears to be a marker for restenosis.

Restenosis following coronary angioplasty: clinical presentations and therapeutic options

Restenosis following angioplasty is an iatrogenic disease of increasing frequency. Restenosis may be defined in terms of either angiographic or clinical criteria. Definitions of angiographic restenosis have varied in different studies, accounting in part for the differences in reported restenosis rates. Most studies now define angiographic restenosis as either a > 50% loss of initial gain or an absolute lesion stenosis of > or = 50% at follow-up angiogram. Common clinical end points used in defining restenosis include recurrent angina, need for repeat revascularization, or myocardial infarction. Despite technical advances and multiple pharmacologic interventions, most studies have found that the incidence of angiographic restenosis remains in the range of 40%; in none of these studies, however, was complete angiographic follow-up obtained, and thus actual restenosis rates may be somewhat higher. In several studies, clinical restenosis has been found to occur in approximately 36-40% of patients. Thus, a minority of patients with angiographic restenosis have no clinical manifestations. Most patients who develop symptoms of restenosis develop these symptoms within the first 3 months after angioplasty. The presenting symptom in the majority of these patients is progressive exertional angina. Patients occasionally will present with unstable angina and only rarely with acute myocardial infarction. In patients who present with recurrent chest pain, several features have been found to be helpful in predicting whether they will have angiographic restenosis at follow-up angiography. Patients who present 1-6 months after angioplasty with typical anginal symptoms have a high likelihood of having angiographic restenosis. By contrast, patients who present more than 6 months after percutaneous transluminal coronary angioplasty with recurrent chest pain are more likely to have new, significant coronary lesions to account for their symptoms. Noninvasive testing in patients with clinical presentations suggestive of restenosis can, in general, add only modest information in predicting whether restenosis is indeed present. A negative exercise thallium test appears to have a high specificity in ruling out restenosis and may be helpful in patients who present with more atypical symptoms. Repeat angioplasty is the therapy most frequently utilized to treat restenosis, although coronary artery bypass surgery or medical therapy may be reasonable alternative therapies. Clinical success rates with repeat angioplasty are > 90%, and major complications are rare; however, restenosis will recur in a significant percentage of these patients. Some patients who develop such recurrent restenoses will ultimately benefit from a strategy of repeat angioplasties, although many will require surgical revascularization.

Comparison of coronary lesions obtained by directional coronary atherectomy in unstable angina, stable angina, and restenosis after either atherectomy or angioplasty

The present study investigated the incidence of the histopathologic lesions and of growth factor expression in a consecutive series of directional coronary atherectomy (DCA) samples from 40 unstable angina pectoris patients without prior acute myocardial infarction and compared the findings with those obtained in DCA samples from 18 patients with stable angina without previous infarction and 18 patients with restenosis. We investigated coronary thrombosis, neointimal hyperplasia, and inflammation. For unstable angina, we correlated the angiographic Ambrose plaque subtypes with the histopathologic findings. The immunophenotype of plaque cells and the growth factor expression were assessed with specific antibodies for cell characterization and for the expression of basic fibroblast and platelet-derived AA and AB growth factors and receptors. The incidence of coronary thrombosis was 35% in patients with unstable angina, 17% in those with stable angina, and 11% in patients with restenosis. Neointimal hyperplasia was found in 38% of unstable angina cases, in 17% of stable angina cases, and in 83% of restenosis cases. Inflammation without thrombus or accelerated progression occurred in 20% of unstable angina and 6% of stable angina samples. In 52% of unstable angina cases, inflammation coexisted with thrombosis and/or neointimal hyperplasia. In the unstable angina group, 71% of the plaques with thrombus had a corresponding angiographic pattern of complicated lesions. The growth factor expression, reported as percentage of cells immunostaining with different growth factor antibodies, was highest in restenosis, followed by unstable angina and stable angina lesions.(ABSTRACT TRUNCATED AT 250 WORDS)

Intravascular ultrasound guidance for peripheral vascular interventions

Intravascular ultrasound (IVUS) imaging during peripheral endovascular interventions adds important information regarding the distribution of disease by providing controlled measurements of the cross-sectional area of the vessel lumen and wall prior to and following procedures. IVUS is useful in determining the mechanism and efficacy of balloon angioplasty, in guiding atherectomy devices, and in assuring appropriate placement of intravascular stents. The incorporation of an IVUS element into catheter-based interventional devices may improve the immediate and long-term results of endovascular interventions by decreasing complications from dissection and perforation of the arterial wall. Combined IVUS-stent prototype catheters are being developed to enable imaging and deployment simultaneously. Similar devices are being explored to enhance expedient, precise delivery of endoluminal grafts. Future studies of endovascular techniques should include IVUS, when possible, to accurately quantitative the initial efficacy of devices and to determine the nature and distribution of recurrent lesions.

Early experience of directional coronary atherectomy: clinical results, complications and histopathological findings

OBJECTIVE

To report the early experience, clinical results and histopathologic findings of Directional Coronary Atherectomy from a UK centre experienced in coronary angioplasty.

DESIGN

Prospective study of the first 45 Directional Coronary Atherectomy (DCA) procedures using the Simpson coronary atherectomy device.

RESULTS

Forty-five procedures were performed in 33 male and 5 female patients (mean age, 55.1 years). Directional Coronary Atherectomy was performed to 50 lesions (39 de novo, 11 restenosis; 44 left anterior descending, 3 right, 2 circumflex coronary arteries and 1 saphenous vein graft). Clinical and primary angiographic success was achieved in 43 of 45 cases (95.5%) and in 47 of 50 lesions (94%) after DCA alone. Before DCA the mean diameter stenosis was 88.7% (range, 50-100%) but following DCA (and percutaneous coronary angioplasty (PTCA) if necessary) the mean diameter stenosis was 3.5% (range, 0-15%; P < 0.001). Complications included occlusive dissection requiring coronary artery bypass surgery in two patients; abrupt closure of right coronary artery in one patient successfully reopened by PTCA and thrombolysis, complicated by excessive blood loss; reversible coronary artery spasm due to minor nose-cone trauma in four patients and temporary side branch loss in one patient. There were no coronary artery perforations, guide catheter complications, peripheral vascular trauma or deaths. On average 5.6 specimens (range, 1-18) were removed per case. Histology showed fibrous intimal plaque in 98%, media in 39% and adventitia in 7%. Neo-intimal hyperplasia was found in all restenosis lesions but also in 30% of de novo lesions.

CONCLUSIONS

This small initial series indicates that directional coronary atherectomy is an effective and safe procedure for the treatment of obstructive coronary artery disease in carefully selected patients. With care, a high success rate can be achieved even during a learning phase. The technique is particularly effective for morphologically complex lesions that are unfavourable for PTCA. The procedure is unlike PTCA and requires additional training if pitfalls are to be avoided, high success rates achieved and complication rates kept low.

Lessons from intravascular ultrasonography: observations during interventional angioplasty procedures

This article reviews many of the applications of intravascular ultrasonic imaging for coronary and peripheral arterial disease. In vitro studies demonstrate an excellent correlation between ultrasound measurements of lumen and plaque cross-sectional area compared with histologic sections. In vivo clinical studies reveal the enhanced diagnostic capabilities of this technology compared with angiography. Ultrasonic imaging also permits visualization of the atherosclerotic plaque itself for the first time in vivo. In addition to accurately describing the plaque morphology, ultrasonography can identify some of the tissue characteristics of the plaque. During interventional procedures, ultrasonic imaging has been shown to be beneficial for enhanced diagnosis as well as improvement of our understanding of the mechanism of newer interventional devices such as directed atherectomy, rotational or TEC atherectomy, or excimer laser. Initial studies suggest that ultrasound guidance of intravascular stent deployment may be critical for optimizing stent placement. Randomized studies are currently in progress to determine whether the guidance provided by intravascular ultrasonic imaging will alter the results of interventional procedures so that the restenosis rate can be improved.

Directional coronary atherectomy: how much lumen enlargement is optimal?

Until recently, it has not been clear how much of the effect of directional coronary atherectomy is due to tissue removal per se, and whether the long-term results of the procedure are helped or harmed when the operator attempts to obtain the "near zero percent" residual stenosis of which this technique is capable. This article summarizes the findings of a series of studies that have addressed these important questions and proposes a prescription for the optimal performance of directional atherectomy. Analysis of retrieved tissue weights compared with measured increases in luminal volume shows that about half of the improvement seen after directional atherectomy results from mechanical dilation. Because this "facilitated" dilation appears to take place within the bases of the trenches created by atherectomy cuts (rather than being randomly distributed in fractures throughout the plaque substance), a larger and smoother lumen is possible compared with that seen after conventional balloon dilation. Although the recovery of deep vessel wall components (media and even adventitia) is common, it generally does not cause either acute complications (i.e., perforation) or increase the probability of subsequent restenosis. Rather, reduction in the probability of late restenosis appears to be most directly related to the ability of directional atherectomy to provide the largest acute luminal diameter safely possible, thus providing better tolerance of subsequent intimal hyperplasia before hemodynamically significant renarrowing results at the treatment site.

Histologic analysis of directional coronary atherectomy samples. A review of findings and their clinical relevance

Histologic analysis of atherectomy samples from > 400 patients who received directional coronary atherectomy at 3 separate institutions disclosed 2 major categories of tissue: atherosclerotic plaque (with or without thrombus) and intimal proliferation (hyperplasia, with or without thrombus). The predominant tissue type in atherectomy samples from native, primary, or de novo coronary artery stenoses was atherosclerotic plaque. The predominant tissue type in atherectomy samples from restenosis lesions (prior balloon angioplasty, atherectomy, or both) was intimal proliferation with variable amounts of atherosclerotic plaques (with or without thrombus). Deep vessel wall components (media, adventitia) were identified at varying frequencies. The clinical relevance of atherectomy tissue is reviewed.

Molecular biology: insight into the causes and prevention of restenosis after arterial intervention

Very little is known about the development of postatherectomy or postangioplasty restenosis. Morphologically, restenosis lesions are primarily composed of smooth muscle cells with associated matrix proteins and develop within 3-6 months. Although some degree of smooth muscle cell proliferation is a necessary part of the healing process after injury, it is unclear why only some individuals develop clinically significant lesions. Platelet deposition and release of growth factors have been postulated to be important in initiating the cellular growth response after vascular injury. Current data suggest that growth factors synthesized locally in the vessel wall may be very important in controlling smooth muscle proliferation. In addition, atherosclerotic plaques contain many procoagulant proteins that are exposed by angioplasty or atherectomy. These proteins stimulate a coagulation response and the activation of thrombin, resulting in platelet aggregation and thrombus formation. Thrombin mediates several biologic responses that may facilitate vascular lesion formation and can act directly as a smooth muscle mitogen. Vascular lesion formation as a result of percutaneous transluminal coronary angioplasty or atherectomy may be stimulated by a combination of factors, including platelet deposition and thrombin action, ultimately generating an autocrine growth response in the vessel wall.

Atherectomy of the subclavian artery for patients with symptomatic coronary-subclavian steal syndrome

OBJECTIVES

This study addresses the efficacy of directional atherectomy in the subclavian artery for the relief of angina in patients with the coronary-subclavian steal syndrome. In addition, we review the histologic findings from the atherectomy specimens.

BACKGROUND

The coronary-subclavian steal syndrome may occur after internal mammary-coronary artery bypass grafting. It is due to a stenosis in the subclavian artery proximal to the origin of the internal mammary artery and causes frank ischemia to the area supplied by the graft. Currently, surgery is the corrective procedure of choice.

METHODS

In three patients with severe subclavian artery stenoses and unstable angina, directional atherectomy was performed using a peripheral atherectomy catheter through a percutaneous femoral approach. The patients ranged from 43 to 71 years of age and had undergone internal mammary-coronary artery bypass grafting 3 to 10 years previously. Each patient had severe peripheral vascular and cerebrovascular disease.

RESULTS

All three patients had immediate symptomatic relief after the atherectomy, and postprocedure exercise testing demonstrated improved cardiac function. Two patients remain asymptomatic at 7 and 8 months, respectively; the third patient developed unstable angina 9 months later because of severe restenosis that was again successfully treated with atherectomy. Histologic examination of the specimens revealed atherosclerotic plaque, occasionally with adventitia. The specimen from the repeat atherectomy showed severe intimal hyperplasia.

CONCLUSIONS

Directional atherectomy appears to be a safe and effective treatment for coronary-subclavian steal syndrome. This procedure may be the treatment of choice for patients in whom a vascular bypass operation is not feasible.

Frequency and consequences of intimal hyperplasia in specimens retrieved by directional atherectomy of native primary coronary artery stenoses and subsequent restenoses

Although intimal hyperplasia is a frequent occurrence after arterial interventional procedures, the overall frequency and significance of intimal hyperplasia in primary coronary lesions has not been previously addressed. The incidence of intimal hyperplasia was therefore examined using standard light microscopy in specimens obtained from native coronary arteries of patients undergoing directional coronary atherectomy. The associated clinical history, angiographic results and clinical outcomes were also tabulated. Intimal hyperplasia was identified in 51 of 55 patients (93%) treated with directional coronary atherectomy for restenosis after a prior intervention. These restenosis lesions had less acute gain in lumen diameter after directional coronary atherectomy, a smaller late lumen diameter, more severe late stenosis (p < 0.04), and tended to have more restenosis defined as late stenosis > or = 50% (restenosis rate 40% for prior restenosis vs 26% for primary lesions). Surprisingly, however, intimal hyperplasia was also identified in 45 of 102 (44%) primary stenoses. Primary lesions (n = 45) with intimal hyperplasia were more likely to occur in younger patients and in the left anterior descending artery than were either primary lesions without intimal hyperplasia (n = 57) or prior restenosis lesions. There were otherwise no differences in the baseline characteristics, angiographic findings or clinical outcome of primary lesions with or without intimal hyperplasia (restenosis rate 28 and 24%, respectively). The event-free survival (72% at 12 months) was similar in all 3 groups. Thus, even though intimal hyperplasia is an almost universal finding in restenosis lesions, intimal hyperplasia is not specific for restenosis since histologically identical hyperplasia may be found in nearly half of primary coronary artery stenoses.(ABSTRACT TRUNCATED AT 250 WORDS)

Histopathological examination of specimens removed during directional coronary atherectomy in patients presenting with crescendo angina show mural thrombus

Thrombus formation over a fissured coronary atheromatous plaque has been shown by post mortem histological examination to be the pathophysiological mechanism responsible for myocardial ischaemia in those patients who died following a crescendo pattern of angina. Histological examination of plaques responsible for a crescendo pattern of angina in patients who do not die has not been available until recently. We describe two patients who presented with a crescendo pattern of angina. A new technique of coronary revascularization, directional coronary atherectomy, produced symptomatic relief and resolution of myocardial ischaemia. Histological examination of material from the stenosis responsible for their myocardial ischaemia, obtained using this technique, confirmed thrombus formation overlying a fissured atheromatous plaque.

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.

Long-term results of directional coronary atherectomy: predictors of restenosis

OBJECTIVES

This study was performed to obtain better understanding of the long-term clinical efficacy of directional coronary atherectomy.

BACKGROUND

Although this procedure yields favorable acute results, its acceptance has been limited by the perception that late results (that is, freedom from restenosis) are no better than those of conventional angioplasty.

METHODS

A total of 225 atherectomies performed in 190 patients between August 1988 and July 1991 were examined. Minimal lumen diameter of the treated segments was measured on angiograms obtained before, after and 6 months after intervention.

RESULTS

Although most lesions (97%) had one or more characteristics predictive of unfavorable short- or long-term results after conventional angioplasty, atherectomy was successful in 205 lesions (91%) with a mean residual stenosis of 7 +/- 16%. After subsequent balloon angioplasty in 16 unsuccessful atherectomy attempts, procedural success was 98%. There were no deaths or Q wave myocardial infarctions, and one patient (0.5%) underwent emergency bypass surgery. Six-month angiographic follow-up was obtained in 77% of the eligible patients. The overall angiographic restenosis rate was 32%. Predictors of a lower restenosis rate included a postprocedure lumen diameter > 3 mm (24% vs. 39%, p = 0.047), serum cholesterol < or = 200 mg/dl (18% vs. 40%, p = 0.018) and recent myocardial infarction (16% vs. 37%, p = 0.034). Life-table analysis showed a 2% mortality rate and a 26% incidence of other events (myocardial infarction, repeat revascularization) within the 1st year. The annual 5% mortality rate and 7% incidence of other events during years 2 and 3 were related in large part to the existence or progression of disease at other locations.

CONCLUSIONS

Six-month angiographic follow-up of patients who underwent directional coronary atherectomy during the 1st 3 years of our experience shows an overall restenosis rate of 32%, with lower rates in patients with a postatherectomy lumen diameter > or = 3 mm, cholesterol level < or = 200 mg/dl or a recent myocardial infarction. Few if any events relating to the site of atherectomy developed after the 1st year of follow-up.