Current understanding of coronary in-stent restenosis. Pathophysiology, clinical presentation, diagnostic work-up, and management

In-stent restenosis is the limiting entity following coronary stent implantation. It is associated with significant morbidity and cost and thus represents a major clinical and economical problem. Worldwide, approximately 250 000 in-stent restenotic lesions per year have to be dealt with. The pathophysiology of instent restenosis is multifactorial and comprises inflammation, smooth muscle cell migration and proliferation and extracellular matrix formation, all mediated by distinct molecular pathways. Instent restenosis has been recognised as very difficult to manage, with a repeat restenosis rate of 50% regardless of the mechanical angioplasty device used. Much more favourable results were reported for the adjunctive irradiation of the in-stent restenotic lesion, with a consistent reduction of the incidence of repeat in-stent restenosis by 50%. Data from the first clinical trials on drug-eluting stents for the treatment of in-stent restenosis have shown very much promise yielding this strategy likely to become the treatment of choice. This review outlines the histological and molecular findings of the pathophysiology, the epidemiology, the predictors and the diagnostic work-up of in-stent restenosis and puts emphasis on the various treatment options for its prevention and therapy.

Early time course of neointima formation and vascular remodelling following percutaneous coronary intervention and vascular brachytherapy of in-stent restenotic lesions as assessed by intravascular ultrasound analysis

In-stent restenosis (ISR) represents the major limitation of stent implantation. Treatment, although of relative technical ease, is unsatisfactory due to a high incidence of recurrent restenosis. Vascular brachytherapy (VBT) has emerged as a powerful adjunct therapeutic modality to treat ISR. Inhibition of neointima formation has been regarded as the relevant mechanism of action. Yet, positive remodelling has been suspected as another contributing factor. Since only very few precise analyses of the extent, distribution and time course of the respective mechanims exist, the goal of the present study was to describe the changes of the vessel geometry at the target lesion and at the reference site following angioplasty and VBT of ISR in 42 patients by means of quantitative coronary angiography (QCA) and intravascular ultrasound (IVUS) before and after the index procedure and at the 3 and 6 month follow-up. By QCA the acute lumen gain measured 2.2+/-0.8 mm, the late lumen loss at 3 months was 0.1+/-0.5 mm and at 6 months 0.4+/-0.7 mm. By IVUS luminal cross-sectional area increased from 1.5+/-1.2 mm(2) to 7.9+/-1.9 mm(2) (p<0.001). The intima hyperplasia cross-sectional area at 3 months was only 0.2+/-1.0 mm(2) (p=0.191), but increased to 0.7+/-0.6 mm(2) (p<0.001) at 6 months resulting in a lumen cross-sectional area of 7.1+/-1.7 mm(2). Stent dimensions did not show any significant changes over time. The external elastic membrane cross-sectional area at 3 months increased by 1.3+/-1.9 mm(2) (p<0.001), and showed a further increase by 0.7+/-2.9 mm(2) at 6 months. Positive remodelling could be demonstrated also at the reference segment. In conclusion the absolute amount of intima hyperplasia during a 6-month follow-up period after VBT of ISR is low and most pronounced between the third and sixth month. Besides this, predominantly within the first 3 months of follow-up, significant positive remodelling could be demonstrated at the target lesion and at the reference site. Both observed effects may contribute to the preservation of the vessel lumen.

Acute limb ischemia after femoral arterial closure with a vascular sealing device: Successful endovascular treatment

We report on successful catheter therapy of acute occlusions of popliteal and crural arteries due to distal embolization from a vascular sealing device. A 45 years-old male patient underwent percutaneous coronary angiography. After primary successful closure of the right femoral artery by a sealing device the patient developed acute ipsilateral lower limb ischemia, most probably due to embolization of a collagen/thrombin plug. Occlusions of the popliteal and crural vessels were successfully treated by percutaneous thrombectomy, thrombolysis and ballon angioplasty. Combined percutaneous catheter therapy is a therapeutic option for occlusions of popliteal and crural vessels due to embolization from a vascular sealing device.

A randomized comparison of 4 doses of intracoronary adenosine in the assessment of fractional flow reserve

BACKGROUND

Fractional flow reserve (FFR) is a measure of coronary stenosis severity that is based on pressure measurements obtained at maximal hyperemia. Therefore, achievement of maximal vasodilatation of the coronary microcirculation is a prerequisite for the measurement of FFR. The study was designed to address the hypothesis that intracoronary adenosine yields more complete vasodilatation of the coronary microcirculation when high doses are used, resulting in a more accurate FFR measurement.

METHODS

Thirty-six patients with 43 moderate lesions underwent determination of FFR during cardiac catheterization. FFR was calculated in all lesions as the ratio of the distal coronary pressure to the aortic pressure at hyperemia. Different incremental doses of intracoronary adenosine (16, 24, 32 and 40 microg for both coronary arteries) were administered in a randomized fashion.

RESULTS

No adverse events occurred with any intracoronary adenosine bolus. At baseline there were no significant differences for mean aortic and distal coronary pressure, heart rate as well as FFR values between the different doses. FFR was not significantly altered from the different incremental adenosine doses. However, in 27 (63%) out of 43 lesions there was a further reduction of FFR up to 0.23 when a dose >16 microg was injected.

CONCLUSIONS

This study suggests that doses of adenosine up to 40 microg are safe and can be used to achieve a more pronounced vasodilatation in individual patients compared to the standard doses. This may have therapeutic impact with FFR values near cut-off points in patients undergoing diagnostic coronary angiography as well as in patients in whom FFR is used to assess the outcome of interventions.

Clinical and angiographic acute and follow up results of intracoronary beta brachytherapy in saphenous vein bypass grafts: a subgroup analysis of the multicentre European registry of intraluminal coronary beta brachytherapy (RENO)

OBJECTIVE

To assess clinically and angiographically the feasibility, safety, and effectiveness of vascular brachytherapy (VBT) in saphenous vein bypass grafts (SVG).

PATIENTS AND METHODS

67 of 1098 (6.1%) consecutive patients of the European registry of intraluminal coronary beta brachytherapy underwent treatment for 68 SVG lesions by VBT using a Sr/Y(90) source train (BetaCath). Clinical follow up data were obtained for all of them after a mean (SD) of 6.3 (2.4) months and angiographic follow up was performed in 61 patients (91.0%) after 6.9 (2.0) months.

RESULTS

58 (86.6%) patients were men, their mean (SD) age was 66 (10) years, 28 (41.8%) had unstable angina, and 21 (31.3%) had diabetes. Fifty three (77.9%) lesions were in-stent restenosis, 13 (19.1%) de novo lesions, and 2 (3.0%) non-stented restenotic lesions. Mean (SD) reference diameter before the intervention was 4.19 (0.52) mm, mean (SD) lesion length was 23.56 (20.38) mm, and mean (SD) minimum lumen diameter measured 0.73 (0.62) mm. Mean (SD) acute gain was 3.02 (0.88) mm. The prescribed radiation dose was 20.1 (3.2) Gy. Pullback manoeuvres were performed in 17 (25.0%) of cases. Most patients received combined aspirin and thienopyridin treatment for 6 or 12 months after the procedure. Technical success was obtained in 62 (91.2%) treated lesions and in-hospital major adverse cardiac events occurred in 4.5%. At follow up, mean (SD) reference diameter was 4.20 (0.53) mm, minimum lumen diameter 2.94 (1.50) mm, and late loss 0.86 (1.25) mm. The overall major adverse cardiac events rate was 26.7%.

CONCLUSION

VBT of SVG is feasible and safe. At follow up the reintervention rate and cardiac morbidity and mortality seem to be favourable, considering that interventions in SVG usually are associated with the highest risks.

[Clinical and angiographic one-year follow-up of vascular beta-brachytherapy for coronary lesions treated by a stent with a very high risk for restenosis]

BACKGROUND

Vascular brachytherapy (VBT) has been proven to reduce restenosis rate and unwanted cardiac events in several randomized trials. Long-term data on populations at high risk for re-interventions are few. The aim of this study was to assess the acute and one-year outcome of beta-radiation in coronary in-stent restenoses with a high likelihood of recurrence.

METHODS

In 79 patients, VBT using 90Yttrium/Strontium or 32Phosphorus, was performed. Clinical and angiographic follow-up was carried out after 6 months and 1 year.

RESULTS

44.4 % of patients had three-vessel coronary artery disease and a high prevalence of cardiovascular risk factors and comorbidity. Mean lesion length was 36.8+/-18.9 mm. VBT was successful in all patients. Fractionation of VBT was necessary in 2,5 %. Acute gain of luminal diameter was 2.15+/-0.89 mm. During the hospital stay one acute myocardial infarction (AMI) not associated with VBT occurred. After 6 months loss of luminal diameter measured 0.39+/-0.47 mm, equaling a restenosis rate (RR) of 16.8 % (1 year: 0.60+/-0.56 mm, RR 33.5 %). 18.9 % of patients required revascularization of the target lesion (1 year: 29.5 %). After 6 months, all patients survived, three had an AMI after discontinuation of clopidogrel, one of them was asymptomatic (1 year: 1 cardiac death, 2 symptomatic AMI).

CONCLUSION

Beta-VBT in patients at a high risk for recurrence after angioplasty is feasible and safe. Though the clinical and angiographic results at 1 year showed some impairment as opposed to the 6-months-follow-up, they nevertheless are largely superior to those patients from historic controls not treated with VBT.

Insights into vascular pathology after intracoronary brachytherapy

Post-angioplasty restenosis is a major limitation of interventional cardiology. A large body of evidence reveals that expression of myofibroblast activity promoters moves progressively from the neoadventitia to the neointima. Brachytherapy inhibits vascular cell activity (proliferation, migration), mitigates recruitment of intimal cells, and shows a favorable prophylactic effect on late vascular remodeling by preventing adventitial constriction at the injured site. These effects of brachytherapy are dose related. Clinical and experimental data demonstrate that restenosis is determined by the balance between arterial remodeling and intimal hyperplasia. Apparently, brachytherapy-induced positive remodeling plays the principal role in increasing the luminal diameter after PTCA and, in case of a lower dose or dose fall-off, to cause detrimental edge effects. With regard to clinical course, healing defects, endothelial dysfunction and stent-vessel wall malapposition are apparently important and possibly underestimated features of vascular pathology, since they may contribute to late thrombosis and delayed intimal hyperplasia in long-term course after intracoronary brachytherapy.

[Edge effect and late thrombosis -- inevitable complications of vascular brachytherapy?]

Restenosis is the limiting entity after percutaneous coronary angioplasty. Vascular brachytherapy for the treatment of in-stent restenosis has been shown to reduce the repeat restenosis rate and the incidence of major adverse events in several randomized trials. Besides the beneficial effects, brachytherapy yielded some unwanted side effects. The development of new stenoses at the edges of the target lesion treated with radiation is termed edge effect. It occurs after afterloading brachytherapy as well as after implantation of radioactive stents. It is characterized by extensive intimal hyperplasia and negative remodeling. As contributing factors the axial dose fall-off, inherent to all radioactive sources, and the application of vessel wall trauma by angioplasty have been identified. The combination of both factors, by insufficient overlap of the radiation length over the injured vessel segment, has been referred to as geographic miss. It has been shown to be associated with a very high incidence of the edge effect. Avoidance of geographic miss is strongly recommended in vascular brachytherapy procedures. Late thrombosis after vascular brachytherapy is of multifactorial origin. It comprises platelet recruitment, fibrin deposition, disturbed vasomotion, non-healing dissection and stent malapposition predisposing to turbulent blood flow. The strongest predictors for late thrombosis are premature discontinuation of antiplatelet therapy and implantation of new stents during the brachytherapy procedure. With a consequent and prolonged antiplatelet therapy, the incidence of late thrombosis has been reduced to placebo levels. Edge effect and late thrombosis represent unwanted side effects of vascular brachytherapy. By means of a thorough treatment planning and prolonged antiplatelet therapy their incidences can be largely reduced. With regard to the very favorable net effect, they do not constitute relevant limitations of vascular brachytherapy.

[Coronary interventions in old patients presenting with cardiogenic shock]

HISTORY AND CLINICAL FINDINGS

A 80-year-old unconscious woman was admitted to our hospital. She had suffered from angina pectoris and progressive dyspnea for three days. She had been in pulmonary edema 6 months ago. Clinical examination revealed low blood pressure of 90/60 mmHg, central cyanosis and signs of pulmonary congestion.

INVESTIGATIONS

Laboratory findings comprised elevated creatinkinase, troponin and lactate dehydrogenase as well as reduced sodium.

CLINICAL COURSE

After intubation and mechanical ventilation the patient underwent cardiac catheterization because of the cardiogenic shock. Coronary angiography revealed severe coronary artery disease with high grade stenoses of the right coronary artery and of the main stem of the left coronary artery. After initiating intraaortic balloon counterpulsation, transcatheter revascularization of the right and left coronary artery was performed, leading to an improvement of the systolic left ventricular function. But the patient finally died due to cardiac pump failure.

CONCLUSION

Elderly patients presenting with cardiogenic shock and additional risk factors have the highest mortality. Thus the decision for cardiac catheterization and eventual intervention should be made on a case-by-case basis. Successful angioplasty may reduce mortality by approximately 20 %. Due to the usually severe comorbidity absolute mortality is nevertheless very high.

[Intravascular ultrasound guided directional atherectomy and stent implantation of an unprotected main stem in a heart transplant patient with comorbidity]

Following orthotopic heart transplantation (HTx), development of transplant vasculopathy (TVP) is the limiting medical entity leading to significant morbidity and mortality beyond the first year after HTx. Selection of a suitable strategy for repeat revascularisation--transcatheter angioplasty, coronary artery bypass grafting or repeat HTx--depends on various parameters including coronary morphology, left ventricular performance, comorbidity, availability of graft material and donor organs. Catheter-based interventions on the main stem of the left coronary artery are feasible, but a relatively lower primary success rate and a higher complication rate and significantly increased mortality have to be expected. We report on a patient who underwent HTx 9 years ago and developed severe transplant vasculopathy revealing significant main stem stenosis, making reintervention necessary. Due to age, coronary artery morphology and comorbidity the patient was not considered for coronary artery bypass grafting or repeat HTx. We performed successful IVUS-guided directional coronary atherectomy and stent implantation on a distal stenosis of the unprotected main stem. Our case demonstrates a predictable procedural risk and favourable primary result of left main stem angioplasty procedures, thus providing a therapeutic option for patients who are poor candidates for operative revascularisation strategies.

Vascular brachytherapy for treatment of cardiac allograft vasculopathy

A high restenosis rate often follows treatment of coronary stenoses in cardiac allograft vasculopathy. We report successful coronary brachytherapy of a second in-stent restenosis in a patient after heart transplantation.

[Carotid stenting with the new slotted tube stent--prospective multicenter study. Essen experiences]]

The indication for therapy of high degree carotid stenoses is discussed controversely in regard to new publications. Only symptomatic carotid stenoses are accepted as indication for operative therapy (arterectomy). The new method of carotid stenting was investigated in several studies and needs to be proved in controlled prospective randomized trials. The use of the self-expanding wall-stent has been established in most working groups; nevertheless some disadvantages should be considered (uncontrolled long segment stenting, covering the origin of ext. carotid artery, insufficient adaptation of struts in carotid communis). After development of a new flexible multicellular balloon-expanding stent (Jo-Carotisstent) with sufficient flexibility and compressibility and different stent lengths, the use of this stent in high degree carotid stenoses was investigated. The aim of this study was to analyze the acute and long-term quantitative stent results (angiography and duplex sonography) and clinical results periinterventionally and during follow-up (0.5-1 year).

METHODS

Selective approach from femoral, 8 Fr.-guiding catheter, canalization of stenosis with coronary guide wire (0.014 inch), primary PTA with coronary balloon.

RESULTS

In 47 of 48 patients with 49 carotid stenoses, successful stent implantation was achieved (97.9%). In 2 patients TIA of short duration (4.2%) and in 1 patient (2.1%) a minor stroke occurred. All stents could be implanted with optimal reference diameter. During follow up after 0.5 year no significant proliferative restenosis was observed. The quantitative analysis showed excellent stent-diameter after 0.5 year with only minimal recoil (< 5%) and no clinical event.

CONCLUSION

Using a new flexible and non-deforming multicellular balloon-expanded stent, selective stenting of high degree carotid artery stenoses can be realized with an excellent procedural success rate and a complication rate comparable with the results of other publicated studies. The results after 0.5 year follow-up seem to be promising.

[Interventions in carotid stenoses: carotid srugery, percutaneous transluminal balloon angioplasty and stent implantation. Indications, results of clinical studies. An overview]

Ischemic stroke is the third most reason of death and the main reason of severe disability in Western countries. The high incidence of stroke, 330 per 100,000 subjects in Germany, illustrates the importance of the disease. Generally, atherosclerotic stenosis of the proximal internal carotid artery is the responsible mechanism. The clinical efficiency of surgically performed endarterectomy has been demonstrated in several large multicenter trials. Proven indications for endarterectomy are symptomatic moderate to high-grade stenoses, rapidly progressive asymptomatic stenoses and asymptomatic patients with lesions revealing greater than sixty percent diameter stenosis under certain clinical conditions. Reduction of the incidence of cerebrovascular events, though, is only possible if a low perioperative complication rate is accomplished. Recommendations of the American Heart Association demand a total periprocedural complication rate less than six percent for symptomatic and less than three percent for asymptomatic stenoses. Implantation of stents in carotid arteries is a promising method which might expand the spectrum of indications toward stenosis morphology unfavorable for surgery and patients with significant comorbidity. Clinical results reveal primary success rates, complication rates, and restenosis rates comparable with those of surgical endarterectomy. Randomized trials, comparing both methods, are necessary and reasonable. Yet results are not available at the moment.

[IVUS-controlled aorto-ostial directional coronary atherectomy in higher grade stenosis of the central anastomosis of a sequential triple venous bypass]

Following coronary artery bypass grafting repeat ischemia mandatory for reintervention occurs in 2 to 30% of cases, depending mainly on graft age. Selection of a suitable strategy for revascularisation--transcatheter angioplasty or reoperation--depends on various parameters including coronary morphology, left ventricular performance, comorbidity and availability of graft material. Catheter-based interventions on saphenous vein bypass grafts are feasible, but lower primary success rates and a higher incidence of restenosis--compared with native coronary arteries--have to be expected. Repeat coronary artery bypass graft operations are associated with a significantly higher perioperative morbidity and mortality, patency rates are lower and late clinical outcome is worse than in primary surgery. We report on a patient who underwent coronary artery bypass grafting 4 years ago revealing a high grade ostial stenosis in a jump-graft supplying RCA, LAD and Cx sequentially, making reintervention necessary. As a prerequisite serial balloon angioplasty of two native vessels was performed prior to ostial intervention. Intravascular-ultrasound guided directional coronary atherectomy was performed with good primary and long-term result. Our case demonstrates that, if all relevant clinical parameters and different therapeutic options are taken into account, complex transcatheter angioplasty procedures are feasible and associated with a reasonable amount of risk, thus avoiding repeat coronary artery bypass graft operations.

[Indications and limits of conventional revascularization methods in coronary heart disease]

The number of cardiologic patients undergoing invasive diagnostic catheterization is rapidly increasing. Due to more liberal and extensive indications for invasive diagnosis patients in relatively unfavorable clinical condition (e.g., elderly patients with severe extracardial disease, patients status post CABG) are being catheterized and, if suitable and indicated, undergo revascularization procedures. With rapidly increasing procedural skill of cardiovascular surgeons and invasive cardiologists even high-risk patients with severe coronary artery disease or underlying illness, who were classically excluded from surgical or catheter-invasive revascularization, are now being treated more aggressively. The changing indications for diagnostic catheterization and significant changes in the different modes of revascularization--operative bypass-surgery or interventional procedures--have led to continuous changes in the differential indications for these invasive therapeutic strategies. This article reviews and discusses the currently accepted indications for surgical and interventional revascularization as well as the limitations of these procedures.