Restenosis after coronary angioplasty: an overview

A Systematic Review and Meta-Analysis of Drug Eluting Stents for Safety and Efficacy in Intracranial Atherosclerotic Disease

BACKGROUND

Advancements in arterial stenting technology have challenged prior notions favoring medical management for intracranial atherosclerotic disease (ICAD). Where previous conclusions were drawn from bare metal stent (BMS) technology, recent studies suggest drug-eluting stents (DES) are favorable due to their anti-proliferative effect, which reduces vascular remodeling.

METHODS

We conducted a systematic review and meta-analysis of the literature prior to August 2023 reviewing all reports of ICAD treated with DES. Our target outcomes were incidence of any stroke, transient ischemic attack (TIA), or death within 30 days (postprocedural complications), ischemic stroke in the territory of the qualifying artery beyond 30 days (long-term complications), radiographically detected in-stent restenosis rate (ISR), and symptomatic ISR during follow-up. A subgroup analysis further stratified preprocedural mean stenosis above and below 70% into severe and moderate cohorts, respectively.

RESULTS

PubMed, Web of Science, Cochrane and EMBASE query identified 527 candidate articles, from which 14 studies met inclusion criteria for a total of 607 patients and 640 ICAD lesions. Incidence of postprocedural complications was 7.3% (95% CI 3.9-11.7%) with subgroup analysis demonstrating significantly higher incidence in the severely stenotic group [9.0% (95% CI 4.7-14.5%)] than the moderately stenotic group [3.0% (95% CI 0.7-6.8%)]. Long-term complications were 1.2% (95% CI 0.4-2.3%). Radiographic ISR was 3.5% (95% CI 1.4-6.3%) and symptomatic ISR was 0.3% (95% CI 0.0-1.5%).

CONCLUSIONS

Our systematic review and meta-analysis suggest that DES can effectively reduce the risk of ISR and may be a viable treatment modality to reduce long-term complications in refractory ICAD patients.

Uncertainty quantification of a three-dimensional in-stent restenosis model with surrogate modelling

In-stent restenosis is a recurrence of coronary artery narrowing due to vascular injury caused by balloon dilation and stent placement. It may lead to the relapse of angina symptoms or to an acute coronary syndrome. An uncertainty quantification of a model for in-stent restenosis with four uncertain parameters (endothelium regeneration time, the threshold strain for smooth muscle cell bond breaking, blood flow velocity and the percentage of fenestration in the internal elastic lamina) is presented. Two quantities of interest were studied, namely the average cross-sectional area and the maximum relative area loss in a vessel. Owing to the high computational cost required for uncertainty quantification, a surrogate model, based on Gaussian process regression with proper orthogonal decomposition, was developed and subsequently used for model response evaluation in the uncertainty quantification. A detailed analysis of the uncertainty propagation is presented. Around 11% and 16% uncertainty is observed on the two quantities of interest, respectively, and the uncertainty estimates show that a higher fenestration mainly determines the uncertainty in the neointimal growth at the initial stage of the process. The uncertainties in blood flow velocity and endothelium regeneration time mainly determine the uncertainty in the quantities of interest at the later, clinically relevant stages of the restenosis process.

Effects of probucol on restenosis after percutaneous coronary intervention: a systematic review and meta-analysis

BACKGROUND

Restenosis after percutaneous coronary intervention (PCI) is a remained clinical problem which limits long-term success of PCI. Although there was recognition that probucol in treating restenosis after percutaneous transluminal coronary angioplasty, the efficacy of probucol on restenosis after stent-implantation is controversial. So this meta-analysis was conducted to investigate the association between probucol and late restenosis.

METHODS

Articles were assessed by four trained investigators, with divergences resolved by consensus. PubMed, EMBASE, ScienceDirect and the Cochrane Central Register of clinical trials were searched for pertinent studies. Inclusion criteria were random allocated to treatment and a comparison of probucol-treated patients and control patients (not treated with lipid-lowering drug) undergoing PCI.

RESULTS

Fifteen studies with 859 subjects were analyzed. Major outcome, binary angiographic restenosis defined as >50% stenosis upon follow-up angiography, was significantly decreased with probucol treatment (RR = 0.59 [0.43, 0.80] among vessels, P = 0.0007; and RR = 0.52 [0.40, 0.68] among patients, P<0.00001). Probucol also increased the minimal luminal diameter (SMD = 0.45 [0.30, 0.61], P<0.00001) and decreased late loss upon follow-up after 6 months (SMD = -0.41 [-0.60, -0.22], P<0.0001). Moreover, there was a significantly lower incidence of major adverse cardiac events (MACE) in the probucol group than control group (RR = 0.69 [0.51, 0.93], P = 0.01).

CONCLUSION

Probucol is more than a lipid-lowering drug. It is also effective in reducing the risk of restenosis and incidence of MACE after PCI.

Myocardial perfusion imaging after coronary revascularization: a clinical appraisal

Revascularization procedures, including percutaneous coronary intervention (PCI) and coronary artery bypass grafting (CABG), are performed in many patients with coronary artery disease. Despite the effectiveness of these procedures, different follow-up strategies need to be considered for the management of patients after revascularization. Stress myocardial perfusion single-photon emission computed tomography (MPS) is a suitable imaging method for the evaluation of patients who have undergone PCI or CABG, and it has been used in the follow-up of such patients. Radionuclide imaging is included in the follow-up strategies after PCI and CABG in patients with symptoms, but guidelines warn against routine testing of all asymptomatic patients after revascularization. After PCI, in the absence of symptoms, radionuclide imaging is recommended and indicated as appropriate after incomplete or suboptimal revascularization and in specific asymptomatic patient subsets. On the other hand, the value of MPS late after CABG in risk stratification has been demonstrated even in the absence of symptoms. Thus, given the adverse outcome associated with silent ischaemia, it can be speculated that all patients regardless of clinical status should undergo stress testing late after revascularization. Larger prospective studies are needed to assess whether stress MPS will have an impact on the outcome in asymptomatic patients after revascularization.

Inhibitory Effects of Bezoar Bovis on Intimal Formation and Vascular Smooth Muscle Cell Proliferation in Rat

Intimal formation of animal carotid arteries induced by balloon endothelial denudation has been considered to be an "accelerated atherosclerosis" model and used in primary screening methods to evaluate natural drugs and chemical candidates. The aim of the present study was to examine whether intimal formation is prevented by Bezoar Bovis (dried cattle gallbladder stones: Niuhuang in Chinese and Go-o in Japanese), which has been used to prevent heart palpitation in patients with hypertension. The intimal-to-medial area ratio in rat carotid arteries 7 days after balloon endothelial denudation was significantly reduced by oral administration of Bezoar Bovis. Bezoar Bovis also suppressed vascular smooth muscle cells (VSMCs) proliferation, which is thought to play important roles in the intimal formation after endothelial damage and also atherosclerosis resulting from long-term inappropriate lifestyle. The present findings suggest that Bezoar Bovis may be useful for preventing atherosclerosis and for protection against restenosis after percutaneous coronary intervention, for which effective reduction method is not currently available.

Myocardial Perfusion SPECT Imaging in Patients after Percutaneous Coronary Intervention

Coronary artery disease (CAD) is the most prevalent form of cardiovascular disease affecting about 13 million Americans, while more than one million percutaneous transluminal intervention (PCI) procedures are performed annually in the USA. The relative high occurrence of restenosis, despite stent implementation, seems to be the primary limitation of PCI. Over the last decades, single photon emission computed tomography (SPECT) myocardial perfusion imaging (MPI), has proven an invaluable tool for the diagnosis of CAD and patients’ risk stratification, providing useful information regarding the decision about revascularization and is well suited to assess patients after intervention. Information gained from post-intervention MPI is crucial to differentiate patients with angina from those with exo-cardiac chest pain syndromes, to assess peri-intervention myocardial damage, to predict-detect restenosis after PCI, to detect CAD progression in non-revascularized vessels, to evaluate the effects of intervention if required for occupational reasons and to evaluate patients’ long-term prognosis. On the other hand, chest pain and exercise electrocardiography are largely unhelpful in identifying patients at risk after PCI.

Although there are enough published data demonstrating the value of myocardial perfusion SPECT imaging in patients after PCI, there is still debate on whether or not these tests should be performed routinely.

Platelet-derived chemokine RANTES may be a sign of restenosis after percutaneous coronary intervention in patients with stable angina pectoris

Inflammation plays a pathogenic role in the development of restenosis after percutaneous coronary intervention (PCI). We measured and compared the ratio of elevated levels of regulated on activation normally T-cell expressed and secreted (RANTES), monocytic chemotactic peptide-1 (MCP-1), soluble (s) P-selectin and sL-selectin after PCI. Plasma levels of chemokines and soluble markers were measured before, 1, 3 and 7 days after PCI in 52 patients (43 males and nine females, aged 63 +/- 10 years) who underwent PCI and who had repeated angiograms at a 6-month follow-up. Restenosis occurred in 16 (31%) patients. A significant and time-dependent increase in sL-selectin was observed in the restenosis group. However, there were no significant differences in MCP-1 levels with or without restenosis. sP-selectin levels in the restenosis group exhibited a transient elevation at 3 days after PCI. RANTES levels were no different at baseline between patients with or without restenosis. However, a significant and time-dependent decrease in RANTES levels were observed in the non-restenosis group, and patients with restenosis compared with patients without restenosis had a statistically significant ratio of elevated levels of RANTES. These findings suggest that restenosis development after PCI in patients with effort angina pectoris may involve leukocyte activation at an early period after PCI. In addition, platelet-derived chemokine RANTES may be a sign of restenosis after PCI in patients with stable angina pectoris.

Clinical value of echocardiographic assessment of coronary flow reserve after left anterior descending coronary artery stenting in an unselected population

BACKGROUND

Transthoracic Doppler echocardiography is a valuable tool to measure coronary flow reserve (CFR) and detect in-stent restenosis (ISR) after percutaneous coronary angioplasty in selected series of patients.

OBJECTIVES

To assess the usefulness of coronary flow reserve measured by echocardiography in detecting significant (> or =70%) ISR of the left anterior descending coronary artery in a large unselected population.

METHODS

Two hundred and twenty-three patients (age 61 +/- 10 years; 168 men) treated with left anterior descending stenting underwent CFR measurement by transthoracic Doppler echocardiography and venous adenosine infusion 24-72 h before control coronary angiography. Coronary-active drugs were continued, and patients with multiple risk factors and old anterior-apical myocardial infarction were included.

RESULTS

Significant ISR occurred in 56 patients (25%). Patients with ISR had higher basal coronary flow velocity (27 +/- 10 cm/s vs. 24 +/- 7 cm/s; P < 0.002) and lower CFR (1.5 +/- 0.5 vs. 2.7 +/- 0.6; P < 0.0001) than those without ISR. A linear relation was found between ISR and CFR (r = -0.73; P < 0.0001) and remained significant after adjustment for blood pressure and heart rate (r = -0.74; P < 0.0001). A CFR less than two identified significant ISR (sensitivity 88%, specificity 88%, area under the curve = 0.943; P < 0.001). In a multivariate model of CFR prediction, myocardial infarction and heart rate were slightly contributory (ss = -0.19, P < 0.01; ss = -0.16, P < 0.03, respectively), whereas ISR had a large influence (ss = -0.66; P < 0.0001). The inverse correlation between ISR and CFR persisted in patients with myocardial infarction (r = -0.64; P < 0.0001) and in those treated with beta-blockers (r = -0. 71; P < 0.0001).

CONCLUSION

Echocardiographic measurement of CFR detects significant left anterior descending ISR in unselected patients with multiple risk factors, old anterior-apical myocardial infarction, and taking beta-blockers.

A randomized comparison of sirolimus-eluting versus bare metal stents in the treatment of diabetic patients with native coronary artery lesions: the DECODE study

OBJECTIVE

To compare the effects of sirolimus-eluting (SES) versus bare metal stents (BMS) on 6-month in-stent late luminal loss (LLL) and 1-year major adverse cardiac events (MACE) in diabetics undergoing percutaneous coronary interventions.

BACKGROUND

In studies of unselected patients, coronary restenosis rates have been lower with SES than with BMS. Comparisons of SES versus BMS in diabetics with more than one stenosis or more than one vessel disease are few.

METHODS

This open-label trial randomly assigned 200 diabetics with de novo coronary artery stenoses to receive up to three SES versus BMS in a 2:1 ratio. The patients underwent repeat coronary angiography at 6 months after the index procedure and were followed-up for 1 year. The primary study endpoint was in-stent LLL at 6 months.

RESULTS

Between August 2002 and May 2004, 83 patients (mean age = 60 years) with 128 lesions (mean = 1.5 per patient) were enrolled at four U.S. and seven Asian medical centers. Enrollment was terminated early by the Safety Monitoring Board because of a statistically significant difference in rates of clinical endpoints. The mean in-stent LLL at 6 months was 0.23 mm in SES versus 1.10 mm in BMS recipients (P < 0.001). At 12 months, 8 patients (15%) assigned to SES had experienced MACE versus 12 patients (41%) assigned to BMS (P = 0.006).

CONCLUSIONS

In diabetics, the mean 6-month in-stent LLL was significantly smaller, and 12-month MACE rate significantly lower, after myocardial revascularization with SES than with BMS.

Endothelial dysfunction and restenosis following percutaneous coronary intervention

BACKGROUND

Restenosis remains an important limitation of PCI. Although local factors such as small vessel diameter and systemic factors such as diabetes explain some of its incidence, it nevertheless also occurs in low-risk patients. We hypothesize that endothelial dysfunction may be an independent risk factor in some of these cases.

METHODS

20 patients who had previously undergone PCI were studied at cardiac catheterization (10 with restenotic lesions were matched to 10 without restenosis). Infusion of multiple concentrations of acetylcholine (ACh) and nitroglycerine (GTN) were made via a 3F infusion catheter into the target artery. Following infusion, changes in diameter of segments proximal and distal to the PCI site were measured.

RESULTS

There was a significant impairment in endothelium-dependent dilatation at the maximal dose of acetylcholine in those with restenosis compared to those without restenosis, both proximal and distal to the stented area (proximal; 11.5+/-7.0% versus -20.9+/-9.0% p<0.001, distal; 12.0+/-3.1% versus -17.8+/-8.1% p<0.001), but there was no difference in the response to GTN. There was a significant correlation between the endothelium-dependent dilatation response and the percent restenosis (r=-0.65, p=0.003).

CONCLUSIONS

Coronary endothelium-dependent dilatation is reduced in subjects with restenosis in arterial segments separate from the stented lesion. This supports a hypothesis that endothelial dysfunction contributes to the development of restenosis, following percutaneous coronary intervention.

Adiponectin incompletely prevent MCP-1-dependent restenosis after percutaneous coronary intervention [corrected] in patients with coronary artery disease

BACKGROUND

Some factors play pathogenic roles in the development of restenosis after percutaneous coronary intervention (PCI). We measured and compared the ratio of elevated levels of monocytic chemotactic peptide-1 (MCP-1), regulated on activation normally T-cell expressed and secreted (RANTES), soluble (s) P-selectin, sE-selectin and adiponectin after PCI.

METHODS

Plasma levels of chemokines and soluble markers were measured before and 30 days after PCI in 96 patients (69 males and 27 females, aged 63 +/- 9 years) who underwent PCI and who had repeated angiograms at a 6-month follow-up. In addition, we carried out the basic study of the tissue factor expression on monocytic cell line (THP-1) by MCP-1.

RESULTS

Restenosis occurred in 33 (34.4%) patients. A significant and time-dependent increase in MCP-1 was observed in the restenosis group. However, there were no significant differences in RANTES, sP-selectin, and sE-selectin levels with or without restenosis. Adiponectin levels in patients with coronary artery disease were significantly lower than levels in normal controls. However, adiponectin levels were no different at baseline between patients with or without restenosis. MCP-1 did not induce the expression of tissue factor on THP-1. However, the recombinant sCD40 ligand-induced expression of tissue factor on THP-1 was enhanced by the addition of MCP-1.

CONCLUSION

These findings suggest that restenosis development after PCI in patients with coronary artery disease may involve the participation of MCP-1 after PCI, and adiponectin incompletely prevent this MCP-1-dependent restenosis.

ENaC proteins contribute to VSMC migration

Vascular smooth muscle cell (VSMC) migration plays a key role in tissue repair after arterial wall injury. VSMC migration requires integration of chemical and mechanical signaling mechanisms. Recently, we showed that epithelial Na(+) channel (ENaC) proteins are expressed in VSMCs and that ENaC inhibition abolishes pressure-induced constriction in isolated artery segments. However, whether ENaC proteins play a role in VSMC migration is unknown. The goal of this study was to determine whether ENaC molecules are required for VSMC migration. Using RT-PCR, immunoblotting, and immunolabeling, we detected expression of alpha-, beta-, and gammaENaC transcripts and proteins in cultured VSMCs (SV40-LT and A10 cells). Of the three proteins, betaENaC was the most readily detected in both cell lines by immunolocalization and Western blotting. Inhibition of ENaC activity with 1 microM benzamil blunted VSMC migration associated with wound healing (40.3% at 8 h and 26.2% at 24 h) and in response to the chemotactic stimulant platelet-derived growth factor-BB (38.1%). Furthermore, silencing ENaC gene expression with small interfering RNA blunted VSMC migration. These data indicate that expression of ENaC proteins is required for normal VSMC migration and suggest a potential new role for ENaC proteins in vascular tissue repair.

Preparation and preliminary biological evaluation of a 166Ho labeled polyazamacrocycle for possible use as an intravascular brachytherapy (IVBT) agent

(166)Ho can be considered as a potential radionuclide for intravascular brachytherapy (IVBT) using liquid-filled balloons owing to its suitable nuclear decay characteristics. The possibility of producing (166)Ho with adequate specific activity using moderate flux reactors and natural holmium target makes it an attractive alternative of (188)Re for developing IVBT agents. Keeping in mind the high thermodynamic stability of lanthanide complexes with polyazamacrocycles, (166)Ho complex of 1,4,8,11-tetraazacyclotetradecane-1,4,8,11-tetraacetic acid (TETA) was prepared and studied for its suitability as a possible agent for IVBT. (166)Ho was produced with adequate specific activity and high radionuclidic purity by irradiating natural Ho(2)O(3) powder. TETA was synthesized by a single step procedure using cyclam as the starting material. (166)Ho-TETA complex was prepared with excellent radiochemical purity and the complex was found to retain its stability for 7 days at room temperature. Biodistribution studies carried out in Wistar rats showed major renal clearance of the injected activity with almost no retention in any of the vital organ/tissue.

Association of Leukocyte Activation, but Not the Common Cold, with Restenosis after Percutaneous Coronary Intervention in Patients with Angina Pectoris

We investigated the relationship between the common cold and restenosis after percutaneous coronary intervention (PCI) in Japanese patients with angina pectoris, because suffering from a common cold during the follow-up period after PCI may be involved in the development of restenosis. In addition, we measured the soluble (s) L-selectin level early after PCI in patients with and without restenosis. The study group included 104 effort angina pectoris patients. We examined whether or not they had had a common cold in the 6 months following angioplasty. Finally, 88 patients, whose common cold status was known, were selected as the study subjects. Twelve patients caught a common cold after PCI. All of these patients were given antibiotics and/or anti-inflammatory agents and recovered within 2 weeks. None had clinically detectable influenza infection. Thirty-three patients suffered from restenosis and 55 did not. There was no significant difference in the restenosis frequency between effort angina pectoris patients with and without a common cold. The sL-selectin level was significantly increased in patients with restenosis early after PCI, whereas in patients without restenosis, sL-selectin remained unchanged. These findings suggest that restenosis development after PCI in patients with effort angina pectoris may involve leukocyte activation early after PCI, while suffering from a common cold during the follow-up period after PCI has no effect.

Diagnostic value of stress echocardiography for the detection of restenosis after PTCA

Stress echocardiography (SE) has become a widely accepted clinical tool for the non-invasive diagnosis of coronary artery disease (CAD). Previous studies have confirmed that SE has superior diagnostic value compared to exercise ECG testing. SE has also emerged as a cost-effective alternative to nuclear imaging techniques in patients where symptoms and/or conventional ECG stress testing have provided ambiguous results. Several studies have investigated the value of SE to detect significant restenosis after PTCA. However, in these studies, different methods have been used to induce cardiovascular stress such as physical exercise by bicycle or treadmill, pharmacologic stress testing (with dipyridamole or dobutamine) or transoesphageal atrial pacing. This review evaluates the published database of SE to detect restenosis in patients after successful PTCA. It includes 13 studies with a total of 989 patients performed at 3-6 months after the primary intervention. The diagnostic value, utility and limitations of SE is presented and discussed. The data show that SE has a high diagnostic value for detecting significant restenosis after PTCA. Mean sensitivity of SE was 74% (CI 69-79%), mean specificity was 87% (CI 84-89%). The positive predictive value (PPV) of SE was 83%, the overall negative predictive value (NPV) 97%. We conclude that, in the follow-up of patients after PTCA, SE has distinct advantages over other non-invasive methods and is a recommended method for the detection of those to be considered for repeat angiography.

Inhibition of vascular smooth muscle cell migration by serum from rats treated orally with Saiko-ka-Ryukotsu-Borei-To, a traditional Chinese formulation

Oral administration of Saiko-ka-Ryukotsu-Borei-To (SRB), a traditional Chinese formulation, has been found to prevent intimal thickening of the carotid artery after balloon endothelial denudation in cholesterol-fed rats. To clarify the mechanism of this effect, the present study investigated if SRB inhibits vascular smooth muscle cell (VSMC) migration, which plays an important role in the development of intimal thickening after endothelial injury. The serum (SRB serum) sampled from cholesterol-fed rats treated orally with SRB for 3 days before and 4 days after the injury dose-dependently inhibited the migration of cultured VSMCs. When added directly to cultured VSMCs, the SRB extract did not inhibit VSMC migration. It is remarkable that SRB serum, which may contain a much lower concentration of SRB ingredients compared with the SRB extract, inhibited cultured VSMC migration. The present testing system using serum obtained from animals treated orally with traditional Chinese formulations may be useful for clarifying the pharmacological efficacy of such drugs, including many non-absorbable components. Furthermore, it may be useful in the search for new active compounds in serum after oral administration of traditional Chinese formulations, the active metabolites of which have not been identified.

Molecular and cellular basis of restenosis after percutaneous coronary intervention: the intertwining roles of platelets, leukocytes, and the coagulation-fibrinolysis system

The major limitation of percutaneous coronary intervention (PCI) is restenosis. Restenosis is considered to be an overreaction of the natural healing process after traumatic balloon dilatation. An elaborate web of cellular and molecular responses, including the interaction of platelets, leukocytes, and the coagulation-fibrinolysis system, as well as the secretion of various growth factors and pro-inflammatory cytokines, contributes to neointimal hyperplasia and the development of restenosis. Moreover, platelet and neutrophil activation after stenting appears to be different from that after balloon angioplasty alone. Pharmacotherapy targeting the cell-to-cell interaction between platelets and neutrophils may potentially offer an effective treatment strategy against restenosis after PCI.

Perivascular delivery of losartan with surgical fibrin glue prevents neointimal hyperplasia after arterial injury

OBJECTIVE

Long-term success of revascularization procedures is limited by recurrent stenosis, a reduction in vascular lumen area that results from neointimal hyperplasia. Inhibitors of the renin-angiotensin system, such as losartan, have potential to prevent recurrent stenosis; however, to date, efficacy has not been demonstrated in either animal models or human beings. While we have previously reported that treatment with a satisfactory dose may be an important element in obtaining efficacy, oral delivery cannot achieve the required concentration. We therefore tested the ability of losartan to restrict neointimal hyperplasia after local delivery of an elevated dose in a fibrin glue.

METHODS

The porcine saphenous artery was subjected to balloon angioplasty. Losartan (25 micromol/mL) was applied directly to the adventitial surface of the injured vessel after mixing with 1.0 mL of Tisseel. Neointimal formation was quantified after 14 days with morphometry, and immunologic staining was used to monitor expression of proteins associated with cell proliferation, migration, and phenotypic modulation.

RESULTS

A statistically significant decrease of 82% (n = 5) in neointimal area was obtained with losartan, and cell proliferation, as defined by proliferating cell nuclear antigen (PCNA) expression, was inhibited by 97%. Reduced cyclin A expression in losartan-treated vessels confirmed that cell cycle progression was blocked; however, the presence of cytokeratin 8 and tenascin in the media and neointima of injured vessels, regardless of treatment, suggested that losartan does not restrict phenotypic modulation. Inhibition of MT1-MMP (MMP-14) expression by losartan indicated that this inhibitor likely suppresses cell migration as well.

CONCLUSIONS

These data demonstrate that losartan can effectively prevent recurrent stenosis when delivered locally with a fibrin glue such as Tisseel. Our results also indicate that losartan may operate by interfering with the expression of proteins required for cell cycle progression and migration.

CLINICAL RELEVANCE

Release of angiotensin II in response to vascular injury may promote neointimal hyperplasia, because this hormone can stimulate smooth muscle cell proliferation and migration. This study demonstrates that local application of an angiotensin receptor antagonist, losartan, to the site of injury can effectively prevent neointimal hyperplasia after balloon angioplasty. Application of losartan to the perivascular surface of the injured vessel in a surgical fibrin glue enabled delivery of a dose that exceeds the maximum attainable, via a systemic delivery route. The glue also served as a depot from which the drug was slowly released over time. Treatment with losartan may be a viable approach for controlling neointimal hyperplasia at locations (eg, grafts) that are accessible during a surgical procedure.

Distinct yet complementary mechanisms of heparin and glycoprotein IIb/IIIa inhibitors on platelet activation and aggregation: implications for restenosis during percutaneous coronary intervention

OBJECTIVE

To study the effect of unfractionated heparin (UFH) versus low molecular weight heparin (LMWH) in combination with glycoprotein (Gp) IIb/IIIa blockers on platelet activation and aggregation.

METHODS

Washed platelets were stimulated with thrombin in the presence or absence of UFH (monoparin), LMWH (enoxaparin), and a Gp IIb/IIIa blocker (abciximab, eptifibatide, or tirofiban).

RESULTS

Although Gp IIb/IIIa antagonists blocked the final common pathway of thrombin induced platelet aggregation, UFH and LMWH were better at blocking upstream platelet activation. UFH was significantly more effective than LMWH at inhibiting P selectin expression (p = 0.001) and platelet derived growth factor release from thrombin activated platelets (p = 0.012).

CONCLUSIONS

UFH and LMWH exert complementary effects to Gp IIb/IIIa blockers by inhibiting afferent pathways of platelet activation. Coadministration of heparin with Gp IIb/IIIa blockers provides improved protection against persistent platelet activation, thereby improving outcome after percutaneous coronary intervention. Judging from these data, UFH may be more effective in this regard than LMWH, at least in vitro. The use of LMWH in preference to UFH during percutaneous coronary intervention, although initially attractive, may inadequately protect against platelet activation despite the presence of Gp IIb/IIIa blockers.

The predictive value of 201Tl rest-redistribution and 18F-fluorodeoxyglucose SPECT for wall motion recovery after recent reperfused myocardial infarction

201Tl and 18F-FDG are useful for acute myocardial infarction (MI) assessment. The goal of this study was to compare their predictive value for wall motion recovery in the culprit area after a recent reperfused MI using SPECT technique.

METHODS

Forty-one patients (mean age: 56 +/- 12 years) were included, 81% of them male; all were studied within 1-24 days post MI. They underwent angioplasty in 27 cases (12 primary); bypass grafting in 10 cases and successful thrombolysis in 4. SPECT 201Tl injected at rest and redistribution (R-R) and also 18F-FDG, were performed on different days. Processed tomograms were interpreted blinded to clinical or angiographic data. Segmental wall motion assessed with echocardiography at baseline was compared with the 3 month follow up.

RESULTS

Sensitivity [Confidence Interval] for 201Tl R-R was 74.6% [60.5-84.5], for FDG it was 82.1% [70.8-90.4]; specificities were 73% [64.3-80.5] and 54.8% [45.6-63.7], respectively. 18F-FDG tended to be more sensitive than 201Tl R-R, but the latter was more specific (p < 0.0004). Both 201Tl RR and 18F-FDG presented high negative predictive value (p: ns).

CONCLUSION

In recent MI, SPECT 201Tl R-R is a valuable and widely available technique for viability detection, with similar sensitivity and significant better specificity than SPECT 18F-FDG.

Myocardial perfusion imaging following percutaneous coronary intervention: the importance of restenosis, disease progression, and directed reintervention

Percutaneous coronary intervention (PCI) has become a mainstay in the treatment of patients with coronary artery disease. Currently, more than one million coronary angioplasty and stent implantation procedures are performed annually. Although increasingly complex lesions and higher risk patients are being successfully treated percutaneously, restenosis and disease progression continue to cause significant morbidity. Restenosis occurs in approximately one-third of patients, one-half of who remain asymptomatic, while disease progression occurs at rates approaching 7% per year. Despite technological advances, unadjusted mortality rates have actually increased since the mid-1980s, and the current annual risk of a major adverse cardiac event following PCI is 5% to 7%. Although randomized clinical trials are needed to more definitively show a benefit, when performed six or more months following PCI, myocardial perfusion imaging reliably identifies patients most at risk of a poor long-term outcome. Directed reintervention can have a salutary impact on the prognosis of these patients. In view of recent data showing a positive impact of imaging and reintervention in patients after PCI, current guidelines should be reassessed.

The BBZDR/Wor Rat Model for Investigating the Complications of Type 2 Diabetes Mellitus

Congenic and inbred strains of rats offer researchers invaluable insight into the etiopathogenesis of diabetes and associated complications. The inbred Bio-Breeding Zucker diabetic rat (BBZDR)/Wor rat strain is a relatively new and emerging model of type 2 diabetes. This strain was created by classical breeding methods used to introgress the defective leptin receptor gene (Lepr(fa)) from insulin-resistant Zucker fatty rats into the inbred BBDR/Wor strain background. The diabetic male BBZDR/Wor rat is homozygous for the fatty mutation and shares the genetic background of the original BB strain. Although lean littermates are phenotypically normal, obese juvenile BBZDR/Wor rats are hyperlipidemic and hyperleptinemic, become insulin resistant, and ultimately develop hyperglycemia. Furthermore, the BBZDR/Wor rat is immune competent and does not develop autoimmunity. Similar to patients with clinical diabetes, the BBZDR/Wor rat develops complications associated with hyperglycemia. The BBZDR/Wor rat is a model system that fully encompasses the ability to study the complications that affect human type 2 diabetic patients. In this review, recent work that has evaluated type 2 diabetic complications in BBZDR/Wor rats is discussed, including the authors' preliminary unpublished studies on cardiovascular disease.

Chimeric DNA–RNA hammerhead ribozyme targeting transforming growth factor-β1 mRNA inhibits neointima formation in rat carotid artery after balloon injury

We designed and synthesized a chimeric DNA-RNA hammerhead ribozyme targeting transforming growth factor (TGF)-beta 1 mRNA and found that this ribozyme effectively and specifically inhibited growth of vascular smooth muscle cells. We examined the effects of the chimeric DNA-RNA hammerhead ribozyme targeting TGF-beta 1 mRNA on neointima formation and investigated the underlying mechanism to develop a possible gene therapy for coronary artery restenosis after percutaneous transluminal coronary angioplasty. Expression of mRNAs encoding TGF-beta 1, p27kip1, and connective tissue growth factor (CTGF) in carotid artery increased after balloon injury. Fluorescein-isothiocyanate (FITC)-labeled ribozyme was taken up into the midlayer smooth muscle of the injured carotid artery. Both 2 and 5 mg of ribozyme reduced neointima formation by 65% compared to that of controls. Ribozyme markedly decreased expression of TGF-beta 1 mRNA and protein in injured vessel. Mismatch ribozyme had no effect on expression of TGF-beta 1 mRNA protein in injured vessel. Ribozyme markedly decreased expression of fibronectin, p27kip1, and CTGF mRNAs in injured vessel, whereas a mismatch ribozyme had no effect on these mRNAs. These findings indicate that the chimeric DNA-RNA hammerhead ribozyme targeting TGF-beta 1 mRNA inhibits neointima formation in rat carotid artery after balloon injury with suppression of TGF-beta 1 and inhibition of extracellular matrix and CTGF. In conclusion, the hammerhead ribozyme against TGF-beta 1 may have promise as a therapy for coronary artery restenosis after percutaneous transluminal coronary angioplasty.

Immunity to heat shock protein 65--an additional determinant in intimal thickening

Inflammation occurring consequent to vessel injury is thought to play an important role in atherosclerosis and restenosis. Autoimmunity to HSP65 has been shown to accelerate early atherogenesis in rabbits and mice, whereas in humans epidemiological data support this contention. In the current study, we explored the possibility of HSP65 influencing the extent of neointimal growth in the rat carotid injury model. Rats were either immunized with recombinant mycobacterial HSP65, heat killed preparation of Mycobacterium tuberculosis (MT), or with PBS, all emulsified in incomplete Freund's adjuvant. Animals were boosted with a similar protocol 3 weeks following the primary immunization and 2 weeks later carotid injury was applied in all animals by balloon inflation. Upon sacrifice 2 weeks later, sera were obtained for measurement of anti-HSP65 antibodies by ELISA, splenocytes were assessed for proliferative response to in vitro priming with HSP65, and carotid arteries were removed for evaluation of neointimal growth. Rats immunized with HSP65 exhibited a brisk and sustained humoral immune response to HSP65, and cellular immunity was also evident by thymidine uptake to splenocytes primed with the respective protein. Neointimal/medial ratio was significantly increased in HSP65 immunized rats, in comparison with MT injected and control animals. In conclusion, immunity to HSP65 can play a role in accelerating restenosis following arterial injury. These results should be further investigated in humans as they may provide a possible link between infections and restenosis/accelerated arteriosclerosis.

Endovascular brachytherapy after percutaneous transluminal angioplasty of recurrent femoropopliteal obstructions

PURPOSE

To test the preventive effect of endovascular brachytherapy (EVBT) on restenosis following secondary angioplasty in patients with presumed neointimal restenosis in the femoropopliteal segment.

METHODS

From March 1997 through May 2000, 100 patients (58 men; mean age 70 years, range 45-87) with postangioplasty femoropopliteal segment restenoses were enrolled and randomized to treatment with repeat angioplasty and EVBT (n=51) or to angioplasty alone (n=49) as control. The groups were similar with regard to demographics and lesion characteristics. High-dose-rate EVBT was performed with (192)Ir irradiation without a centering device (12 Gy for a reference vessel radius of 3 mm and a 2-mm reference depth). Primary endpoint in the 1-year follow-up was recurrent obstruction >50% documented by duplex ultrasound; the secondary endpoint was clinical improvement.

RESULTS

Only 44 (86%) of 51 patients received adequate EVBT due to technical failure, so the 7 failures were included with the controls in the per-protocol adherence analysis. At 1 year, the patients receiving EVBT had a restenosis rate of 23% (10/44), which differed significantly (p<0.028) from the 42% (23/56) rate in controls. Clinical results tended to be better with EVBT, but differences did not achieve statistical significance.

CONCLUSIONS

EVBT without a centering device reduced restenosis significantly in patients with recurrent stenosis after angioplasty, which confirms previous results in primary long-segment femoropopliteal obstructions.

The Cutting Balloon--a new technology?

The Cutting Balloon consists of a standard balloon dilatation catheter with four microtome-sharp blades that incise the plaque and minimize arterial wall trauma. It was used in 31 patients; nine had calcified arteries, ten had non-compliant lesions, three had in-stent restenosis and nine had aorto-ostial lesions. Seventeen lesions were predilated, 28 were post-dilated and 18 required stent implantation. The procedure was very effective in aorto-ostial lesions, non-compliant lesions that were not responsive to high-pressure balloon dilatation, and was partially successful in calcified arteries. It has a very specific niche in selected lesions.

Exercise stress testing, myocardial perfusion imaging and stress echocardiography for detecting restenosis after successful percutaneous transluminal coronary angioplasty: a review of performance

When chest symptoms recur in a patient who underwent percutaneous transluminal coronary angioplasty (PTCA), it is necessary to rule out restenosis (R). Three main noninvasive tests suggest the presence of R: exercise stress test (XT), myocardial perfusion imaging (MPI) and stress echocardiography (s-echo). The objectives of this review were: (1) to estimate the pretest probability of R as a function of time after PTCA in symptomatic patients and (2) to obtain an approximation of the diagnostic parameters of the XT, MPI and s-echo for detecting R. A MEDLINE search (English-language, years: 1980-2001) was conducted to identify studies examining post-PTCA functional testing for diagnosing R. Data from the studies were pooled. Comparing studies was often difficult due to varying methodology in the studies. Pretest probability of R in symptomatic patients increases in a nonlinear fashion from 20% or less at 1 month, to nearly 90% at 1-year postangioplasty. The approximated accuracy of the XT, MPI, and s-echo for detecting R was 62, 82 and 84%, respectively. During the first month after PTCA, none of the noninvasive modalities is able to accurately detect R. Late (7-9 months) after PTCA, the pretest probability of R is high and therefore the noninvasive measure may be spared. Our analysis suggests that MPI and s-echo should be preferred over the XT for diagnosing R.

Role of target vessel size and body surface area on outcomes after percutaneous coronary interventions in women

BACKGROUND

Women have higher mortality rates than men after coronary angioplasty. Differences in target vessel size may partially account for these differences. We set out to explore the effects of sex, body surface area (BSA), and target coronary vessel size on clinical outcomes after angioplasty.

METHODS

Data from 5 interventional trials and 1 registry were pooled for analysis (n = 3982).

RESULTS

Compared with men, women undergoing angioplasty were older, had lower weights and BSA, more coronary risk factors, and slightly smaller target coronary vessel size (as assessed by reference vessel diameter). The correlation between target vessel size and BSA was poor (r = 0.13). At 6 months, women had higher mortality rates (1.7% vs 0.8%, P =.03) but similar rates of myocardial infarction and repeat revascularization. On univariate analysis, advanced age, smaller BSA, and female sex were associated with increased mortality, but target vessel size was not. Advanced age was the only significant multivariate predictor of mortality. Target vessel size and diabetes were independent predictors of repeat revascularization.

CONCLUSIONS

Women have higher unadjusted 6-month mortality rates after angioplasty, owing largely to their more advanced age at the time of intervention. Smaller target vessel size is associated with increased risk of restenosis and repeat revascularization; however, it does not appear to be a predictor for downstream mortality. As such, the fact that women have smaller vessels does not account for their higher 6-month mortality after coronary angioplasty.

Macrophages, myofibroblasts and neointimal hyperplasia after coronary artery injury and repair

Macrophages participate in the restenosis process through the release of cytokines, metalloproteinases and growth factors. Studies of peritoneal granulation tissue suggest that macrophages may be precursors of myofibroblasts. This study examined the contribution of monocyte/macrophage lineage cells to neointimal cellular mass in a porcine model of thermal vascular injury. Thermal coronary artery injury caused medial smooth muscle cell necrosis and transformation of the media into an extracellular matrix barrier. The neointimal hyperplasia that developed over the injury sites was evaluated by light microscopy, electron microscopy and immunohistochemistry. At day 3, blood monocytes were adhered to the vessel wall and infiltrated the fibrotic media. At day 14, 42+/-3.9% of neointimal cells had a monocytic nuclear morphology and expressed macrophage-specific antigen SWC3 (identified by monoclonal antibody DH59B). Moreover, 9.2+/-1.8% of neointimal cells co-expressed SWC3 and alpha-smooth muscle actin and had ultrastructural characteristics intermediate between macrophages and myofibroblasts. At day 28, 10.5+/-3.5% of cells expressed SWC3 and 5.2+/-1.8% of cells co-expressed SWC3 and alpha-smooth muscle actin. This study indicates that hematopoietic cells of monocyte/macrophage lineage abundantly populate the neointima in the process of lesion formation and may be precursors of neointimal myofibroblasts after thermal vascular injury.

Fighting restenosis after coronary angioplasty: contemporary and future treatment options

Despite the widespread use of coronary stents, prevention of restenosis after percutaneous transluminal coronary angioplasty (PTCA) remains a major challenge. The restenotic process is even higher after balloon angioplasty without stenting and has been shown to be in the range of 30-50%. Experimental data suggest that 3-hydroxy-3-methylglutaryl coenzyme A (HMG CoA) reductase inhibitors ("statins") might have a beneficial effect on restenosis after coronary angioplasty. Proposed mechanisms include favorable effects on plasma lipoproteins, endothelial function, plaque architecture and stability, thrombosis and inflammation. Although statins have documented efficacy in reducing clinical events and angiographic disease progression in patients with coronary atherosclerosis, the results of subsequent large prospective clinical trials using different types of statins clearly demonstrate that statins do not have a short-to-medium term effect on prevention of restenosis after successful conventional PTCA. The underlying pathological reasons for this shortcoming as well as promising innovative approaches including gene therapy and local drug delivery of vasoactive substances will be discussed in this review.

CCAAT/enhancer-binding protein decoy oligodeoxynucleotide inhibition of macrophage-rich vascular lesion formation in hypercholesterolemic rabbits

Many cytokine genes, including those encoding acute-phase proteins and immunoglobulins, share binding sites for the CCAAT/enhancer-binding protein (C/EBP) in their 5'-flanking regions, and C/EBP-related transcription factors regulate cell proliferation during terminal differentiation. Therefore, C/EBP represents an attractive target for inhibiting restenosis after balloon angioplasty. In a rabbit model of restenosis that combines balloon injury of the carotid artery with cholesterol-mediated chronic inflammation, a decoy oligodeoxynucleotide (ODN) capable of neutralizing C/EBP was administered to the site of injury for 30 minutes. Electrophoretic mobility shift analysis confirmed that C/EBP activity in decoy ODN-treated segments was virtually absent after 2 days. Morphometric analysis after 28 days revealed significant reduction (up to 50%) of neointimal formation and intravascular inflammation in decoy ODN-treated segments compared with mutant control ODN or vehicle-treated segments. In addition, de novo synthesis of endothelin-1 and the number of proliferating cell nuclear antigen-positive smooth muscle cells in the vessel wall were markedly attenuated at day 3. These findings suggest that decoy ODN-based neutralization of C/EBP may be a feasible and effective method to limit restenosis after angioplasty brought about, at least in part, by inhibiting the de novo synthesis of endothelin-1.

Preparation and evaluation of [166Ho] holmium-dimethyl diethylenetriaminepentaaceticacid (DMDTPA) as potential radiopharmaceutical for endovascular radiation therapy (EVRT)

Holmium-166 with its favorable radiation characteristics could be used in endovascular radionuclide therapy (EVRT) technique in liquid filled low-pressure balloon angioplasty. 166Ho-dimethyl di ethylene triamine penta acetic acid (DMDTPA) was prepared and its biodistribution carried out to evaluate its suitability as an EVRT formulation. DMDTPA was synthesized, characterized and was complexed with 166Ho. The complex was stable at 37 degrees C in human serum environment and at room temperature for 48 h. Biodistribution studies in mice revealed rapid renal clearance (approximately 90% of the injected dose in 30 min p.i.) with insignificant retention in any of the major organs including bone. The studies show that 166Ho-DMDTPA is a good formulation which can be explored as an EVRT source.

Dose effect of guidewire position in intravascular brachytherapy

It has been reported that the dose effects of metallic guidewires are significant in intravascular brachytherapy (IVBT) using a beta source. The purpose of this work is to investigate the dependence of these dose effects on guidewire position. The EGS4 Monte Carlo codes were used to perform the dose calculations for the 90Sr (NOVOSTE), 32P (Guidant) and 192Ir (BEST Ind.) sources with and without a guidewire in place. Guidewires were placed at various distances from the central axes of the sources. Due to the attenuation by the guidewires, a dose reduction of up to 70% behind a guidewire was observed for the beta sources, while the dose perturbation was found to be negligible for the gamma source. The dose reduction for the beta sources was found to be dependent on the guidewire location. For example, the dose reduction was 10% higher for a stainless steel guidewire located at 0.5 mm than that for the guidewire at 2 mm from the central axis of the source, The portion of the target volume affected (shadowed) dosimetrically by the guidewire was reduced when the guidewire was positioned farther away from the source. The shadow volume (in which the dose reduction occurs) can be reduced by up to 45% as the guidewire is moved away from the source axis from 0.5 mm to 2 mm. The dosimetric perturbations due to the presence of a metallic guidewire as well as their dependence on guidewire location should be considered in designing a new IVBT delivery device, in analysing the treatment efficacy, and/or in dose prescription for a beta source.

Preventive effects of a traditional Chinese formulation, Chaihu-jia-Longgu-Muli-tang, on intimal thickening of carotid artery injured by balloon endothelial denudation in rats

We report here that the traditional Chinese formulation, Chaihu-jia-Longgu-Muli-tang (CLM), significantly inhibited the increase in intimal thickening in rat carotid artery injured by balloon endothelial denudation, which mimics many aspects of restenosis after percutaneous coronary intervention (PCI) in humans. CLM, Saiko-ka-Ryukotsu-Borei-to in Japanese, is commonly prescribed for symptoms accompanying hypertension and atherosclerosis in Japanese Kampo medical care. CLM administered orally 1 week before and 1, 4 and 8 weeks after balloon injury inhibited the increase in intimal area, intimal/medial ratio and stenosis ratio. To our knowledge, this is the first report demonstrating inhibitory effects of a traditional Chinese formulation on intimal thickening of carotid artery after balloon injury. It is worth noting that CLM maintained its inhibitory effect up to 8 weeks after balloon injury. The reduction in intimal thickening by CLM could have resulted from inhibition of intimal smooth muscle cell proliferation, which was assessed by immuno-histochemical analysis using monoclonal antibody against proliferating cell nuclear antigen. Therefore, CLM may be a favourable candidate for prevention of restenosis after PCI. Moreover CLM may have a therapeutic value in the prevention of atherosclerosis, because restenosis after PCI is considered to be an accelerated atherosclerosis.

Exposure of the operator to ionizing radiation during intracoronary radiation therapy

This study examined the radiation exposure levels and safety of medical personnel during intracoronary radiotherapy procedures. The data of 34 stenosis patients from a total of 42 irradiated patients who participated in the Seoul National University Hospital Postangioplasty Rhenium (SPARE) trial were analyzed. Intracoronary radiotherapy was delivered to the patient immediately after angioplasty ballooning. The prescribed dose was 17 Gy to the media of the diseased artery and was delivered via a Re-188 filled balloon catheter. Dosimetry was carried out with a Geiger-Müller counter at eight different points. The selected maximum and whole-body exposed doses to the operator were 10 cm and 40 cm from the patient's heart. Median delivered activity was 111.6 MCi, with an average treatment time of 576 seconds. Average exposed dose rates at 10 cm and 40 cm from the patient's heart level were 47.2 mrem/hour and 29.6 mrem/hour, respectively, and average exposed doses per treatment were 7.0 mrem and 4.9 mrem, respectively. Exposure levels measured were much lower than the recommended limit of 50 mSv for radiation workers or 1 mSv for the general population, as recommended by the International Commission on Radiological Protection. This study proves that the method of intracoronary radiotherapy currently adopted and which is the basis of this trial is safe with respect to radiation protection.

Propionyl-L-carnitine reduces intimal hyperplasia after injury in normocholesterolemic rabbit carotid artery by modulating proliferation and caspase 3-dependent apoptosis of vascular smooth muscle cells

Previously we documented that propionyl-L-carnitine (PLC) reduces the growth of atherosclerotic lesions in cholesterol-fed aged rabbits in association with a decrease of plaque smooth muscle cell (SMC) proliferation and plasma triglycerides. To clarify whether PLC might influence SMC growth through mechanisms other than triglyceride lowering, we investigated the effect of a daily treatment per os with PLC on carotid intimal hyperplasia after ballooning in normocholesterolemic rabbits. PLC did not induce variations of plasma triglyceride and cholesterol. One week later, the number of proliferating SMCs was reduced in PLC as compared with controls. After 3 weeks, morphometric analysis demonstrated a reduced neointimal relative volume and percentage of stenosis but not vessel area in PLC as compared with controls. This associated with an intimal reduced SMC number and an increased apoptotic rate as detected by nick-end labelling (TUNEL) and ligation-mediated polymerase chain reaction (PCR). Western blotting also demonstrated an increase of caspase-3 cleavage in PLC carotids. Antiproliferative and pro-apoptotic effects of PLC were confirmed in vitro on actively proliferating and serum deprived SMCs, respectively. Molecules with an additional cell-specific, pro-apoptotic action may represent a new therapeutic tool in reducing intimal SMC hyperplasia following angioplasty or stenting procedures.

Dose effects of guide wires for catheter-based intravascular brachytherapy

PURPOSE

Guide wires with high torquability and steerability are commonly used to navigate through a tortuous and/or branching arterial tree in a catheter-based intravascular brachytherapy procedure. The dosimetric effects due to the presence of metallic guide wires have not been addressed. This work investigates these dose effects for the three most commonly used beta and gamma sources (90Sr, 32P, and 192Ir).

METHODS AND MATERIALS

The EGS4 Monte Carlo codes were used to calculate the dose distributions for the 90Sr(NOVOSTE), 32P (Guidant), and 192Ir (BEST Ind.) with and without a guide wire in place. Energy spectra for particles exiting the sources were calculated from the full phase-space data obtained from the Monte Carlo simulations of the source constructions. Guide wires of various thicknesses and compositions were studied.

RESULTS

The dose perturbations due to the presence of guide wires were found to be far more significant for the 90Sr/90Y and 32P beta sources than those for the 192Ir gamma source. Because of the attenuation by the guide wires, a dose reduction of up to 60% behind a guide wire was observed for the beta sources, whereas the dose perturbation was found to be negligible for the gamma source. For a beta source, the dose perturbations depend on the thickness and the material of the guide wire. When the region behind a guide wire is part of an intravascular brachytherapy target, the presence of the guide wire results in a significant underdosing for beta sources. The underdosed region can extend a few mm behind the guide wire and up to 1 mm in other directions.

CONCLUSION

Significant dose perturbations by the presence of a metallic guide wire have been found in catheter-based intravascular brachytherapy using beta sources. The dose effects should be considered in the dose prescription and/or in analyzing the treatment outcome for beta sources. Such precautions are not necessary if using a gamma source.

Intracoronary beta-radiation exacerbates long-term neointima formation in balloon-injured pig coronary arteries

BACKGROUND

Long-term biological effects of ionizing radiation on coronary arteries remain poorly defined. We examined late arterial responses 6 months after balloon angioplasty and beta-radiation in normal pig coronary arteries.

METHODS AND RESULTS

Coronary arteries of 25 adult pigs were randomized to receive 20 Gy (n=8) or 30 Gy (n=9) of (186)Re beta-radiation or sham radiation (n=8) immediately after balloon angioplasty. Aspirin was given daily during follow-up. The study vessels were analyzed histopathologically at 6 months. beta-Radiation decreased lumen area (20 Gy, 1.55+/-0.99 mm(2); 30 Gy, 1.03+/-0.82 mm(2); and 0 Gy, 2.05+/-0.80 mm(2); P<0.05) but not overall vessel area. The neointimal area was significantly larger within the injured segment with beta-radiation (20 Gy, 1.92+/-1.23 mm(2); 30 Gy, 1.51+/-0.97 mm(2); and 0 Gy, 0.89+/-0.31 mm(2); 0 Gy versus 20 Gy, P<0.05), and a significant increase of edge stenosis was observed with beta-radiation. Irradiated vessels also had larger thrombus areas within the neointima (30 Gy, 0.24+/-0.61 mm(2); 20 Gy, 0.98+/-1.57 mm2; and 0 Gy, 0.00+/-0.01 mm(2); P<0.05) and larger adventitial areas (20 Gy, 2.25+/-0.75 mm(2); 30 Gy, 2.38+/-0.98 mm(2); and 0 Gy, 1.23+/-0.29 mm(2); 0 Gy versus 20 or 30 Gy, P<0.05) that showed substantial collagen accumulation.

CONCLUSIONS

Intracoronary beta-radiation did not inhibit neointima formation in balloon-injured normal pig coronary arteries 6 months after the interventional procedure. Unresorbed thrombus contributed to, but was not the sole component of, augmented neointima formation. Irradiated vessels demonstrated more adventitial thickening and fibrosis. These observations may have relevance for long-term clinical outcomes after intracoronary beta-radiation.

The effect of intravenous immunoglobulins on intimal thickening in a mouse model of arterial injury

Inflammatory mechanisms appear to influence the progression of intimal thickening in experimental models of arterial injury. Intravenous immunoglobulin (IVIG) is a polyspecific preparation of human immunoglobulin (Ig)G employed for treatment of autoimmune disorders. In this study, we sought to investigate whether treatment with IVIG could influence intimal thickening in a model of murine arterial injury. Intimal thickening was induced by placement of a periadventitial cuff over the right femoral artery of male C57BL/6 mice. In the first experiment, IVIG or human serum albumin (HSA) (10 mg/mouse) were administered intraperitoneally for five consecutive days starting 1 day prior to cuff placement. In the second experiment, IVIG or HSA treatment were delivered similarly, but initiated 3 days following induction of arterial injury. Neointimal area and intimal/medial ratio were significantly reduced in mice treated with IVIG prior to cuff placement as compared with HSA treatment. No differences were noted with regard to neointimal area or intimal/medial ratio, between IVIG- and HSA-treated mice when the treatment was commenced 3 days following induction of injury. IVIG treatment reduced the proliferative capacity of splenocytes to the non-specific mitogen Con-A. Treatment with IVIG was associated with a significantly enhanced secretion of interleukin (IL)-10) by the respective splenocytes in comparison with HSA-treated mice. No effect of IVIG was evident on the secretion of IL-4 or IFN-gamma. Thus, IVIG has proven beneficial in ameliorating intimal thickening in a mouse model of arterial injury. The effect could be mediated by upregulation of T-cell secretion of the anti-inflammatory cytokine IL-10.