Growth factors and endothelial dysfunction

Endothelial dysfunction has been implicated in the pathogenesis of many cardiovascular diseases; experimental and clinical studies have shown that endothelial dysfunction may be a key factor in various processes, including abnormal arterial vasomotion, thrombosis or neointimal proliferation. Endothelial dysfunction has been shown to be a characteristic feature of atherosclerotic vessels, sites subject to mechanical injury or collateral vessels that develop in response to severe ischaemia. Fibroblast growth factor (FGF) and vascular endothelial growth factor (VEGF) are important growth factors for endothelial cells in vitro. While VEGF is specific for endothelial cells, FGFs are also potent growth factors for other cell types such as smooth muscle cells. Recent studies have demonstrated the feasibility of using endothelial cell growth factors in vivo. Basic FGF (bFGF) and VEGF have been shown to increase the development of collateral vessels in ischaemic models and to enhance the extent of endothelial regrowth following arterial injury. The marked anatomical improvement associated with the administration of endothelial cell growth factors has promoted questions concerning a possible role for these factors in endothelial dysfunction. In vivo administration of endothelial cell growth factors is associated with significant improvement in endothelium-dependent responses. This effect is observed with bFGF and VEGF in various animal models of endothelial dysfunction such as the collateral circulation, the regenerated endothelium following arterial injury and experimental atherosclerosis. While the precise mechanisms underlying this ubiquitous beneficial effect of endothelial cell growth factors are still to be determined, these results do support the concept of using such factors as a new therapeutic strategy in patients with vascular diseases.

[Restenosis after angioplasty]

Restenosis remains the main limitation of endocoronary methods of revascularisation. It is observed in 20 to over 50% of cases, depending on the prevailing risk factors and techniques used. The mechanism of post balloon angioplasty restenosis consists of neointimal hyperplasia, vascular remodelling and thrombosis. Intra-stent thrombosis is mainly caused by the neointimal hyperplasia. The strategies developed to prevent restenosis may be grouped in two categories: mechanical and pharmacological strategies. Stenting is the only mechanical method to have been shown to be effective. With respect to pharmacological methods, the general impression is rather negative even if some positive results have been reported recently. Of the new strategies which may provide a solution in the coming years, gene therapy and endocoronary irradiation justify a special mention.

[Coronary angioplasty in diabetic patients. Analysis of the problems to improve results]

The object of this review is to update our knowledge of the results of revascularisation by angioplasty in diabetics. The authors discuss: 1. the clinical results in diabetic patients compared with non-diabetics and the results of coronary bypass surgery; 2. the factors influencing the prognosis of these patients after balloon angioplasty, especially with respect to restenosis; 3. the possibilities of improving the results by the use of modern techniques of revascularisation and prevention and 4. the strategies of revascularisation which may be proposed, based on available data.

Growth factors and endothelial dysfunction

Endothelial dysfunction has been implicated in the pathogenesis of many cardiovascular diseases: experimental and clinical studies have shown that endothelial dysfunction may be a key factor in various processes, including abnormal arterial vasomotion, thrombosis or neointimial proliferation. Endothelial dysfunction has been shown to be a characteristic feature of atherosclerotic vessels, sites subject to mechanical injury or collateral vessels that develop in response to severe ischaemia. Fibroblast growth factor (FGF) and vascular endothelial growth factor (VEGF) are important growth factors for endothelial cells in vitro. While VEGF is specific for endothelial cells. FGFs are also potent growth factors for other cell types such as smooth muscle cells. Recent studies have demonstrated the feasibility of using endothelial cell growth factors in vivo. Basic FGF (bFGF) and VEGF have been shown to increase the development of collateral vessels in ischaemic models and to enhance the extent of endothelial regrowth following arterial injury. The marked anatomical improvement associated with the administration of endothelial cell growth factors has promoted questions concerning a possible role for these factors in endothelial dysfunction. In vivo administration of endothelial cell growth factors is associated with significant improvement in endothelium-dependent responses. This effect is observed with bFGF and VEGF in various animal models of endothelial dysfunction such as the collateral circulation, the regenerated endothelium following arterial injury and experimental atherosclerosis. While the precise mechanisms underlying this ubiquitous beneficial effect of endothelial cell growth factors are still to be determined, these results do support the concept of using such factors as a new therapeutic strategy in patients with vascular diseases.

L-arginine and L-NAME have no effects on the reendothelialization process after arterial balloon injury

OBJECTIVE

Growth regulatory properties of nitric oxide (NO) in cultured endothelial cells is controversial. The aim of our study was to investigate the effect of L-arginine, the endogenous NO precursor, and L-NAME, an inhibitor of NO synthase on the reendothelialization process after angioplasty.

METHODS

Fifty-five New Zealand White rabbits underwent denudation of the left iliac artery. After injury the rabbits were randomized in three groups: L-arginine 2.25% (L-arginine, n = 19); NG-nitro-L-arginine methyl ester 15 mg/kg/day (L-NAME, n = 19); and placebo (controls, n = 17). Treatment was solubilized in drinking water. Reendothelialization was evaluated at 4 weeks by macroscopic evaluation of Evans blue staining and endothelial-specific immunostaining (CD-31) on cross sections. Intimal hyperplasia was evaluated by morphometric analysis.

RESULTS

Despite a significant increase in plasma arginine (P = 0.001) and a reduction in intimal hyperplasia (P = 0.003) with L-arginine, neither agent had a significant effect on reendothelialization at 4 weeks (controls = 36 +/- 4%, L-arginine = 43 +/- 3%, L-NAME = 33 +/- 4%; NS).

CONCLUSION

These results suggest that, in spite of previously demonstrated effects on neointimal hyperplasia, the NO pathway does not influence the regrowth of macrovascular endothelial cells in vivo.

Restenosis, late vessel occlusion and left ventricular function six months after balloon angioplasty in diabetic patients

OBJECTIVES

We studied angiographic outcome and its predictors after traditional coronary balloon angioplasty in diabetics. We further examined whether changes in ejection fraction were influenced by the status of the dilated site(s) at follow-up.

BACKGROUND

Recent studies have suggested that diabetics have a particularly poor outcome after balloon angioplasty. The reasons for this observation are not known.

METHODS

We investigated procedural and six-month angiographic outcome, analyzed by quantitative coronary angiography, and left ventricular function in 485 consecutive diabetics (627 lesions) treated by balloon angioplasty without stent implantation.

RESULTS

The procedure was successful in 455 (94%) patients; angiographic follow-up was available in 377 patients (83%). At follow-up, the rates of restenosis and total occlusion were 62% and 13%, respectively. Five independent predictors of restenosis were identified: the presence of organ damage, a saphenous vein graft (SVG) angioplasty, a bifurcation lesion, a Thrombolysis in Myocardial Infarction (TIMI) flow <3 preprocedure and the degree of residual stenosis. Four independent predictors of vessel occlusion were identified: treatment with insulin, a SVG angioplasty, a TIMI flow <3 preprocedure and the degree of residual stenosis after angioplasty. Late vessel occlusion at angioplasty site(s) was observed in 15% of patients, ranging from 11% for a one-site procedure to 37% for a three-site procedure. This complication was associated with a decrease in ejection fraction at follow-up (-6.2 +/- 9.9%, p = 0.0001), whereas no significant change was observed in patients without occlusion.

CONCLUSIONS

This study shows that late vessel occlusion is a frequent mode of restenosis in diabetic patients and is associated with a significant decrease in ejection fraction. This could partly explain the poor long-term clinical outcome reported in such patients after traditional balloon angioplasty.

Angiographically documented late reocclusion after successful coronary angioplasty of an infarct-related lesion is a powerful predictor of long-term mortality

BACKGROUND

Late reocclusion of an infarct-related artery (IRA) that was patent in the early days after acute myocardial infarction (MI) is a frequent event; the reocclusion rate may be as high as 30%. Few studies have been designed to analyze the impact of late reocclusion of the IRA on late survival.

METHODS AND RESULTS

We studied 528 patients who all had a patent IRA after a successful PTCA procedure 10+/-6 days after MI and who underwent systematic 6-month angiographic follow-up to assess late patency of the IRA. We compared long-term survival of patients with and without late reocclusion. Based on the results of 6-month follow-up angiography, 2 groups of patients were defined: (1) 90 patients (17%) with reocclusion (Thrombolysis In Myocardial Infarction [TIMI] flow 0 or 1) and (2) 438 patients (83%) without reocclusion. Long-term clinical follow-up was obtained for all 528 patients at a median of 5.7 years after follow-up angiography (6.4 years after PTCA). The overall actuarial 8-year total mortality rate was 13%. At the end of follow-up, there were 35 deaths (8%) among the 438 patients without reocclusion and 18 deaths (20%) among the 90 patients with reocclusion (P=0.002). The actuarial 8-year total mortality rate was 10% in patients without reocclusion and 28% in patients with reocclusion (P=0.0003). The actuarial cardiovascular mortality rate was 7% in patients without reocclusion and 25% in patients with reocclusion (P<0.0001). The impact of reocclusion on long-term mortality was greater in patients with anterior MI.

CONCLUSIONS

Late IRA patency is strongly associated with long-term survival after MI. These observations should encourage prospective studies to evaluate the impact of strategies designed to prevent late reocclusion in postinfarction patients.

Role of nitric oxide in restenosis after experimental balloon angioplasty in the hypercholesterolemic rabbit: effects on neointimal hyperplasia and vascular remodeling

OBJECTIVES

The purpose of this study was to assess the effects of L-arginine and N(G)-nitro-L-arginine methyl ester (L-NAME) on neointimal hyperplasia and vascular remodeling after balloon angioplasty in the hypercholesterolemic rabbit.

BACKGROUND

Restenosis after balloon angioplasty is a consequence of both neointimal hyperplasia and vessel remodeling. Nitric oxide inhibits neointimal hyperplasia, but its effect on vessel remodeling is unknown.

METHODS

Six weeks after induction of bilateral iliac atherosclerosis, 48 rabbits underwent successful angioplasty in 75 vessels. Eight rabbits (acute group) were sacrificed immediately after angioplasty. The remaining animals received either placebo (chronic control group), or a diet supplemented with either L-arginine (1.5 g/kg/day), or L-NAME (15 mg/kg/day) for 4 weeks after angioplasty.

RESULTS

The intimal area was significantly greater in the chronic control group compared to the acute group (2.60+/-1.03 mm2 vs. 1.35+/-0.62 mm2). This increase in intimal area was lower in the L-arginine group (1.79+/-0.61 mm2), and greater in the L-NAME group (3.23+/-0.92 mm2). The area circumscribed by the internal elastic lamina (IEL) increased significantly in the control group compared to the acute group (from 2.52+/-0.66 to 3.33+/-0.85 mm2); a more marked increase occurred in the L-NAME group (3.90+/-0.85 mm2). By contrast, IEL area was unchanged in the L-arginine group (2.41+/-0.62 mm2). As a result, there was no significant difference in lumen area after 4 weeks in the chronic groups (control: 0.74+/-0.38 mm2; L-arginine: 0.50+/-0.43 mm2; L-NAME: 0.48+/-0.42 mm2).

CONCLUSIONS

Our results demonstrate that L-arginine inhibits whereas L-NAME stimulates neointimal hyperplasia after experimental balloon angioplasty in the hypercholesterolemic rabbit. However, the lack of vessel enlargement in the L-arginine group resulted in a similar final lumen size in the L-NAME and L-arginine groups.

Randomized multicenter comparison of conventional anticoagulation versus antiplatelet therapy in unplanned and elective coronary stenting. The full anticoagulation versus aspirin and ticlopidine (fantastic) study

BACKGROUND

Dual therapy with ticlopidine and aspirin has been shown to be as effective as or more effective than conventional anticoagulation in patients with an optimal result after implantation of intracoronary metallic stents. However, the safety and efficacy of antiplatelet therapy alone in an unselected population has not been evaluated.

METHODS

Patients were randomized to conventional anticoagulation or to treatment with antiplatelet therapy alone. Indications for stenting were classified as elective (decided before the procedure) or unplanned (to salvage failed angioplasty or to optimize the results of balloon angioplasty). After stenting, patients received aspirin and either ticlopidine or conventional anticoagulation (heparin or oral anticoagulant). The primary end point was the occurrence of bleeding or peripheral vascular complications; secondary end points were cardiac events (death, infarction, or stent occlusion) and duration of hospitalization.

RESULTS

In 13 centers, 236 patients were randomized to anticoagulation and 249 to antiplatelet therapy. Stenting was elective in 58% of patients and unplanned in 42%. Stent implantation was successfully achieved in 99% of patients. A primary end point occurred in 33 patients (13.5%) in the antiplatelet group and 48 patients (21%) in the anticoagulation group (odds ratio=0.6 [95% CI 0.36 to 0.98], P=0.03). Major cardiac-related events in electively stented patients were less common (odds ratio=0.23 [95% CI 0.05 to 0.91], P=0.01) in the antiplatelet group (3 of 123, 2.4%) than the anticoagulation group (11 of 111, 9.9%). Hospital stay was significantly shorter in the antiplatelet group (4.3+/-3.6 versus 6. 4+/-3.7 days, P=0.0001).

CONCLUSIONS

Antiplatelet therapy after coronary stenting significantly reduced rates of bleeding and subacute stent occlusion compared with conventional anticoagulation.

[Current data on atheromatous plaques and their evolution]

The modes of evolution of atheromatous plaques are now better understood. The process may start very early and continue for several decades. The severity of atherosclerosis lies in the results of phases of rapid progression involving a thrombotic mechanism. An initial mechanical accident (rupture or erosion of the plaque) is followed by a phenomenon of arterial thrombosis of variable severity. The vulnerability of an atheromatous plaque (defined as its potential for acute complication) is related to: 1) the risk of rupture, 2) the risk of thrombosis in case of rupture. A number of intrinsic properties influence the degree of plaque vulnerability. A thorough understanding of these mechanisms is essential for the development of new treatments to improve the prognosis of coronary patients.

[From the angiogenic response to ischemia to the validation of the concept of "therapeutic angiogenesis"]

The object of this review is to assess the importance of angiogenesis in cardiovascular physiology and to review the new therapeutic approach which have opened up in this field. The authors report: 1) general information about growth factors implicated in angiotensin (fibroblast growth factor, vascular endothelial growth factor, scatter factor). 2) data obtained from embryo studies which have confirmed the relative rôle of certain intermediary molecules, especially vascular endothelial growth factor in vascular formation. 3) results of animal model experiments of chronic ischaemia and 4) the therapeutic possibilities that these studies suggest and the preliminary results of human applications.

Predictors of restenosis after coronary stent implantation

OBJECTIVES

We sought to determine predictors of restenosis after coronary stenting (CS) in a consecutive series of patients.

BACKGROUND

Although stenting in highly selected patient groups reduces restenosis, the results of stenting in a heterogeneous patient group and the effects of clinical and procedural factors on stent restenosis are currently unclear.

METHODS

We analyzed the 6-month angiographic outcome of 500 lesions in 463 consecutive patients undergoing successful CS. Clinical, qualitative and quantitative angiographic variables were correlated with restenosis assessed as both a binary and a continuous variable.

RESULTS

Restenosis, defined as the presence of >50% diameter stenosis in the dilated segment, was present in 105 (26%) of the 405 lesions with angiographic follow-up. The mean late lumen loss during the follow-up period was 0.79+/-0.64 mm. Implantation of multiple stents (p < 0.0001) and a high acute gain (p < 0.0002) were independently associated with a higher late lumen loss. In contrast, the use of high inflation pressure (p < 0.02) and Palmaz-Schatz stents (p < 0.005) was independently associated with a lower late lumen loss. When restenosis was defined as a qualitative variable, implantation of multiple stents (p < 0.001), stenosis length (p < 0.01), small reference diameter (p < 0.02) and stent type other than Palmaz-Schatz (p < 0.01) were independent predictors of restenosis. None of the clinical variables tested was associated with restenosis.

CONCLUSIONS

Coronary stenting in an unselected patient group is associated with an acceptable restenosis rate. Although some risk factors were identified, the risk of restenosis was not related to most of the variables tested. This suggests that the superiority of CS over balloon angioplasty, in terms of restenosis, might also apply to subgroups of patients that were not included in the recent randomized studies.

Effects of poloxamer 407 on transfection time and percutaneous adenovirus-mediated gene transfer in native and stented vessels

Reduction in transfection time and the ability to perform gene transfer in conjunction with endovascular stent implantation constitute two important challenges for percutaneous adenovirus-mediated gene transfer to vessel walls. Studies have suggested that the use of biocompatible polyol poloxamer 407 could be useful. We first evaluated the use of poloxamer 407 for percutaneous gene transfer in nonstented rabbit iliac arteries. A 200-microl mixture of Ad-RSVbetagal or Ad-CMVLuc in either phosphate-buffered saline (PBS) or 20% poloxamer was delivered. After 3 days, gene transfection was evaluated by X-Gal staining or measurement of luciferase activity. Poloxamer use resulted in a 3- to 15-fold increase in the percentage of transfected cells (X-Gal, p = 0.001) and a 16-fold increase in protein product (luciferase activity, p = 0.03), and allowed a decrease in transfection time from 30 to 5 min with minimal reduction in transfection efficiency. We then evaluated the feasibility of percutaneous gene transfer, using Ad-RSVbetagal diluted in pure PBS or 20% poloxamer, in conjunction with stent implantation. Gene delivery was performed either immediately before (pre-) or after (post-) stent implantation. When adenoviruses were diluted in PBS, gene transfer had a low efficiency (prestent, 0.3%; poststent, 0.2%; NS). With poloxamer, the efficacy was much higher (p = 0.0001) and similar "pre" (2.2%) or "post" (1.7%) stent delivery (NS).

CONCLUSIONS

(1) The use of poloxamer, rather than PBS, as a vehicle increases the efficacy of percutaneous adenovirus-mediated gene transfer and reduces transfection time; (2) gene transfer performed during stent implantation with poloxamer is feasible and achieves a significant level of gene expression. Thus percutaneous gene delivery is applicable to conventional stents and could present an attractive method by which to achieve local biological effects in a stent environment.

Intramural injection of biodegradable microspheres as a local drug-delivery system to inhibit neointimal thickening in a rabbit model of balloon angioplasty

Restenosis remains the major limitation of coronary angioplasty. The objective of this study was to develop microspheres able to be delivered at the angioplasty site for long-term drug release and to test their effects in a model of balloon angioplasty. Polylactic-co-glycolide acid microspheres (5-10 microm in diameter) were prepared by using an oil-in-water emulsion-solvent evaporation method. In vitro experiments with hydrocortisone-loaded microspheres revealed a hydrocortisone release for 4 weeks. We studied the in vivo effect of injection of microspheres into the arterial wall of New Zealand White rabbits by using a perforated balloon. Deep penetration of microspheres in the arterial wall was documented immediately after angioplasty. Intimal hyperplasia was assessed in iliac arteries 4 weeks after angioplasty. The morphometric analysis was performed in four groups of animals; the first group was subjected only to conventional angioplasty (control, n = 10), whereas the other three groups after conventional angioplasty were received perforated balloon angioplasty with saline (n = 10), microspheres (n = 10), or hydrocortisone-loaded microspheres (n = 7). Intramural injection of saline did not induce greater intimal hyperplasia compared with control (0.17 +/- 0.03 vs. 0.18 +/- 0.03 mm2, respectively). Microspheres injection was associated with a trend toward a greater degree of intimal hyperplasia that did not reach statistical significance. Hydrocortisone-loaded microspheres were associated with a significant reduction in intimal hyperplasia compared with unloaded microspheres (0.16 +/- 0.02 vs. 0.26 +/- 0.03 mm2, respectively). The polylactic-co-glycolide acid microspheres are well tolerated, easily injected into the arterial wall, and the increase of intimal hyperplasia is easily inhibited by release of hydrocortisone for 4 weeks after initial injury.

Potentiated angiogenic effect of scatter factor/hepatocyte growth factor via induction of vascular endothelial growth factor: the case for paracrine amplification of angiogenesis

BACKGROUND

Scatter factor/hepatocyte growth factor (SF/HGF) is a pleiotropic growth factor that stimulates proliferation and migration of endothelial cells (ECs) via the c-Met receptor, present on ECs as well as other cell types, including smooth muscle cells (SMCs). We studied the effects of recombinant human (rh) SF/HGF in vitro and in vivo in a rabbit model of hindlimb ischemia. We further compared these effects with those of recombinant human vascular endothelial growth factor (rhVEGF165), an EC-specific mitogen.

METHODS AND RESULTS

In vitro, rhSF/HGF and rhVEGF165 exhibited similar effects on proliferation and migration of ECs. When both cytokines were administered together, the result was an additive effect on EC proliferation and a synergistic effect on EC migration. Application of rhSF/HGF to cultures of human SMCs resulted in the induction of VEGF mRNA and protein. In vivo, administration of rhSF/HGF (500 microg x 3) was associated with significant improvements in collateral formation (P<.001) and regional blood flow (P<.0005) and with a significant reduction in muscle atrophy (P<.0001). These effects were significantly more pronounced than those of rhVEGF165 administered according to the same protocol (P<.05). Neither remote angiogenesis nor other pathological sequelae were observed with either rhSF/HGF or rhVEGF165.

CONCLUSIONS

The pleiotropic effects of certain growth factors may potentiate angiogenesis via a combination of direct effects on EC proliferation and migration and indirect effects that result in the generation of other potent EC mitogens from non-EC populations. The synergistic effects demonstrated when SF/HGF and VEGF are administered together in vitro may be reproduced in vivo by SF/HGF-induced upregulation of VEGF in vascular SMCs.

Six-month angiographic outcome after successful repeat percutaneous intervention for in-stent restenosis

BACKGROUND

In-stent restenosis is an increasing clinical problem. Discordant results have been published regarding the risk of recurrent restenosis after repeat angioplasty for the treatment of in-stent restenosis.

METHODS AND RESULTS

One hundred three consecutive patients (107 vessels) underwent repeat percutaneous intervention for the treatment of in-stent restenosis and were entered in a prospective angiographic follow-up program. Repeat balloon angioplasty was performed at 93 lesions (87%) and additional stenting at 14 lesions (13%). The primary success rate was 98%. Six-month angiographic follow-up was performed in 85% of eligible patients. Restenosis was determined by quantitative angiography. Restenosis defined as a >50% diameter stenosis at follow-up was observed at 22% of lesions. The rate of target-lesion revascularization at 6 months was 17%. Repeat intervention for diffuse in-stent restenosis and severe stenosis before repeat intervention were associated with significantly higher rates of recurrent restenosis.

CONCLUSIONS

The overall restenosis rate after repeat intervention for in-stent restenosis is low. The subgroup of patients with diffuse and/or severe in-stent restenosis, however, is at higher risk of recurrent restenosis and may benefit from alternative therapeutic strategies.

Coronary angioscopic findings in the infarct-related vessel within 1 month of acute myocardial infarction: natural history and the effect of thrombolysis

BACKGROUND

Limited angioscopic information is available on the natural history of infarct-related plaque after myocardial infarction (MI), in particular the effect of thrombolysis.

METHODS AND RESULTS

We studied with angioscopy the morphological characteristics of the infarct-related lesion in 56 patients between 24 hours and 4 weeks after MI. Forty of these patients were initially treated with a thrombolytic agent. Most lesions were complex (complex + ulcerated shape = 54%). The predominant color of the plaque was yellow in 79% of cases; only 6% were uniformly white. Angioscopically visible thrombus was found in 77% of cases. Despite angioscopic evidence of instability, only 7% of the patients had post-MI angina. During the 1-month time window since the occurrence of MI, there was no significant difference in the angioscopic appearance of the plaque except for a slight increase in uniformly white plaques (P=.07). The use of a thrombolytic agent at the onset of MI was associated with a reduction in thrombus size and less protruding thrombi (P=.02) but not with a decreased frequency of plaque containing thrombi. Furthermore, a trend for more frequently ulcerated plaques (45% versus 16%, P=.06) was associated with the use of a thrombolytic agent.

CONCLUSIONS

These results suggest that healing of the infarct-related lesion requires more than 1 month and that an "unstable" yellow plaque with adherent thrombus is common during that period. This finding may partly explain the unique behavior of recent infarct-related lesions, which are more prone to occlude than other lesions.

Effects of coronary stenting on restenosis and occlusion after angioplasty of the culprit vessel in patients with recent myocardial infarction

BACKGROUND

PTCA of an infarct-related lesion is associated with a high rate of restenosis and/or vessel occlusion. Recent studies have shown that coronary stenting in patients with stable or unstable angina is associated with a significant reduction in the restenosis rate compared with conventional balloon angioplasty. However, no information is available concerning the long-term effect of coronary stenting at infarct-related lesions compared with balloon angioplasty alone.

METHODS AND RESULTS

One hundred consecutive patients undergoing stent implantation at an infarct-related lesion and systematic 6-month angiographic follow-up were matched for major pre-PTCA clinical and angiographic variables with a group of patients undergoing conventional angioplasty. Preprocedural, postprocedural, and 6-month follow-up angiograms were analyzed with quantitative angiography. Coronary stenting was performed as a bailout procedure after failed balloon angioplasty in 20%, for a suboptimal result after balloon angioplasty in 71%, and electively in 9%. Stent implantation was associated with a higher acute gain than balloon angioplasty. At follow-up, the minimal lumen diameter was significantly (P<.0001) larger in the stent group (1.72+/-0.69 versus 1.23+/-0.72 mm). Restenosis (>50% DS at follow-up) occurred in 27% of the stent group versus 52% of the balloon group (P<.005). At follow-up, total occlusion at the dilated site occurred in 1% of the stent group versus 14% of the balloon group (P<.005).

CONCLUSIONS

Coronary stenting of infarct-related lesions is associated with a highly beneficial effect on 6-month angiographic outcome compared with balloon angioplasty alone. Further studies are needed to establish whether the beneficial effect of coronary stenting on long-term vessel patency is associated with an improvement in left ventricular function or in clinical outcome.

Effects of stenting of recent or chronic coronary occlusions on late vessel patency and left ventricular function

Due to high rates of late vessel reocclusion, balloon angioplasty of recent or chronic coronary occlusions is not associated with a sustained improvement in left ventricular function. Recent studies have suggested that stent implantation at coronary occlusions significantly reduces late vessel occlusion. We thus designed a study to analyze the effect of stent implantation at coronary occlusions on late vessel potency and left ventricular function. Twenty-four consecutive patients with recent or chronic coronary occlusions had successful stent implantation and were enrolled in a 6-month angiographic follow-up program. Contrast left ventricular cineangiography, at baseline and 6-month follow-up, as well as preprocedural, postprocedural, and follow-up angiograms analyzed with quantitative angiography were available in 22 of the patients (92%). At follow-up, no vessel reocclusion was observed and 32% of the patients, as analyzed by the >50% diameter stenosis criterion, had restenosis. There was a significant improvement in global left ventricular function with a decrease in both left ventricular end-diastolic volume index (LVEDVI, p <0.01) and left ventricular end-systolic volume index (LVESVI, p <0.0001) and an increase in left ventricular ejection fraction (LVEF, p <0.0001). Similarly, regional wall motion in the territory of the recanalized artery was also significantly improved (p <0.05). These effects were associated with a reduction in left ventricular filling pressure (p <0.0001). Stent implantation following balloon angioplasty of recent or chronic coronary occlusion is associated with a low rate of late vessel reocclusion, a reduction in cardiac volume, and an increase in ejection fraction. Such effects on left ventricular volumes could have a significant impact on patient survival.

[Endothelial dysfunction in cardiovascular diseases: therapeutic implications after coronary angioplasty]

Restenosis remains the principal limitation of coronary angioplasty; its main mechanisms are neointimal hyperplasia and vascular remodeling. The endothelium destroyed at angioplasty will progressively recover the denuded zone. However, dysfunction of this neo-endothelium persists for quite a period and may participate in restenosis by influencing these two components (hyperplasia and remodeling). Several therapeutic strategies are under evaluation to try and accelerate the regeneration of the endothelium and make it functional more rapidly. Increasing available nitric oxide (NO) decreases the hyperplasia and improves endothelial function. Growth factors accelerate the endothelial regeneration and improves its function: the effect on hyperplasia depends on the growth factor used. The angiotensin converting enzyme inhibitors decrease hyperplasia by improving endothelial function. These therapeutic strategies merit evaluation in the clinical setting.

Hypercholesterolemia attenuates angiogenesis but does not preclude augmentation by angiogenic cytokines

BACKGROUND

The impact of hyperlipidemia on collateral vessel development in vivo remains enigmatic. We sought to determine the anatomic extent and functional capacity of the collateral bed that develops in response to limb ischemia in a well characterized animal model of spontaneous hypercholesterolemia, the Watanabe heritable hyperlipidemic (WHHL) rabbit. We further characterized the impact of exogenous angiogenic cytokine administration on collateral vessel development and function in the same animal model.

METHODS AND RESULTS

Weight-matched 6-month-old male homozygous WHHL (n=9) and normal New Zealand White (NZW) (n=9) rabbits underwent surgical resection of one femoral artery. Ten days later, the ischemic hindlimb was evaluated for collateral vessel formation, blood flow, and tissue damage. Collateral vasculature was less extensive among WHHL than NZW, as indicated by a significant reduction in angiographic score (0.19+/-0.02 versus 0.35+/-0.03, P<.001) and capillary density (46.4+/-4.1 versus 78.9+/-4.6/mm2, P<.0002). This was associated with a reduction in calf blood pressure index (9.5+/-3.5% versus 32.8+/-2.8%, P<.0001), arterial blood flow (7.5+/-0.6 versus 13.6+/-0.7 mL/min, P<.0001), and muscle perfusion index (40.1+/-3.2% versus 65.9+/-2.0%, P<.0001) and an increase in muscle necrosis (48.16+/-5.41% versus 25.90+/-3.83% negative 2,3,5-triphenyltetrazolium chloride staining, P<.004). Treatment of WHHL rabbits (n=9) with recombinant human vascular endothelial growth factor produced a statistically significant improvement in all functional as well as anatomic indices of collateral development.

CONCLUSIONS

Collateral vessel development associated with hindlimb ischemia in vivo is severely attenuated in an animal model of spontaneous hypercholesterolemia but nevertheless may be augmented by administration of angiogenic cytokines.

[Recanalization of complete coronary occlusions followed by STENT implantation. An angiographic study after 6 months]

The restenosis and reocclusion rate after coronary recanalization by conventional angioplasty are high. The role of stent implantation in this context is unknown. The authors assessed a group of 49 patients who underwent implantation of one or more stent after a recanalization procedure by angiography at 6 months. The restenosis rate assessed by quantitative angiography was 24%; no cases of reocclusion were observed. These angiographic results were accompanied with a significant improvement of the anginal symptoms (p < 0.01). These results suggest that stent implantation following recanalization of a coronary occlusion may be beneficial on the restenosis and reocclusion rates and anginal symptoms. However, they should be confirmed by randomised study. It would also be important to analyse the impact of this procedure on the outcome of left ventricular function.