Angiotensin-converting enzyme tissue activity in the diffuse in-stent restenotic plaque

Increase in Vascular Injury of Sodium Overloaded Mice May be Related to Vascular Angiotensin Modulation

This study aimed to analyzing the effect of chronic sodium overload upon carotid and femoral injury, and its relation to vascular angiotensin modulation. Male C57Bl6 mice were divided in: control (cont), receiving 1% NaCl solution for 2 weeks (salt-2) or 12 weeks (salt-12). Two-weeks before the end of the study, a 2mm catheter was implanted around the left femoral and carotid arteries to induce injury. Blood pressure (BP) and heart rate (HR) were measured at the end of the study by tail plethysmography. Arteries were collected and prepared for histological analysis to determine arterial thickening and perivascular collagen deposition. Angiotensin II and Ang(1-7) were quantified in fresh arteries using the HPLC method. There were no differences in body weight, BP and HR. Intima/media ratio had a similar increase in both injured arteries of cont and salt-2 mice, but a more pronounced increase was observed in salt-12 mice (31.1±6%). On the other hand, sodium overload modified perivascular collagen deposition, increasing thick fibers (cont: 0.5%; salt-2: 3.4%; salt-12: 0.6%) and decreasing thin fibers (cont: 7.4%; salt-2: 0.5%; salt-12: 6.8%) in non-injured arteries. Injured arteries presented similar collagen fiber distribution. Angiotensin quantification showed increased Ang(1-7) in salt treated mice (salt-2: +72%; salt-12: +45%) with a concomitant decrease in Ang II (salt-2: -54%; salt-12: -60%). Vascular injury increased significantly Ang(1-7) in salt-12 mice (+80%), maintaining Ang II reduction similar to that of a non-injured artery. The lack of changes in BP and HR suggests that the structural changes observed may be due to non-hemodynamic mechanisms such as local renin-angiotensin system. Collagen evaluation suggests that sodium overload induces time-related changes in vascular remodeling. The increase of artery injury with concomitant increase in Ang(1-7) in 12-week treated mice shows a direct association between the duration of salt treatment and the magnitude of vascular injury.

Long-term histological and immunohistochemical findings in human venous aorto-coronary bypass grafts

The aim of the present study was to analyse the long-term histology and immunohistochemistry of the plaque composition and cellular infiltration of SVGs (saphenous vein grafts) containing metallic stents. Percutaneous interventions in SVGs have a worse long-term clinical outcome compared with stenting of coronary arteries. Whether the pathological features of old degenerated SVGs condition the efficacy of drug-eluting stents is also unknown. Histology and immunohistochemistry of seven SVGs in the coronary circulation containing 12 metallic stents implanted 5 to 61 months before retrieval were analysed in patients undergoing a second aorto-coronary bypass surgery at a mean time of 11±6 years. The pathology of the old SVGs showed an important thrombotic and necrotic composition of the plaque, with plaque protrusion through the stent wires and a fragile media layer that could easily be damaged by stent placement with subsequent neointimal proliferation; indeed, stents with medial fracture had significantly greater mean neointimal thickness than those without (1.37±0.68 compared with 0.81±0.47 mm2; P<0.02). Neointimal inflammatory cell density correlated with increased neointimal thickness in patent vessels (r2=0.43, P<0.001). Immunostaining showed the total absence of ERs (oestrogen receptors), a poor cellular proliferative state as indicated by the presence of the Ki-67 marker, and persistent inflammation close to the stent wires as revealed by KP-1 and ACE (angiotensin-converting enzyme) immunostaining in most inflammatory cells in contact with the metal. These pathological findings may contribute to the more severe progression of disease and worse clinical outcome observed after conventional stented angioplasty of SVGs and might also interfere with the efficacy of drug-eluting stents in this specific atherosclerotic milieu.

Role of Angiotensin-Converting Enzyme Inhibitors in the Coronary Artery Bypass Patient

Angiotensin-converting enzyme inhibitors have been shown to prolong survival and decrease infarct size in patients after acute coronary syndromes. Now there is evidence to suggest that angiotensin-converting enzyme inhibition is beneficial in coronary artery bypass patients. This review will summarize the beneficial effects of angiotensin-converting enzyme inhibition in patients with ischemic heart disease and provide evidence to show that the routine use of angiotensin-converting enzyme inhibition in coronary artery bypass patients can improve clinical outcomes.

The use of angiotensin-converting enzyme inhibitors in patients undergoing coronary artery bypass graft surgery

Angiotensin-converting enzyme inhibitors have been shown to prolong survival, decrease infarct size, and improve ventricular function in patients who have congestive heart failure, and in those who have sustained a myocardial infarction. This review will summarize the evidence to show that angiotensin-converting enzyme inhibitors can also benefit patients undergoing coronary artery bypass graft surgery by minimizing perioperative ischemia, and reducing long-term cardiovascular events.

Renin-Angiotensin System Intervention to Prevent In-Stent Restenosis

The occurrence of in-stent restenosis is a major drawback of percutaneous transluminal coronary angioplasty with stent placement. Target vessel revascularization is necessary in 15% of patients who receive a stent. Recent advances in the development of drug-eluting stents have reduced these numbers tremendously. However refinement of antirestenotic therapies remains obligatory. The emerging interest in more physiological antirestenotic therapies might unchain an interest in the well-known inhibitors of the rennin-angiotensin system (RAS), the angiotensin-converting enzyme inhibitors, and the angiotensin II type I receptor blockers. Contradictory results overshadow the discussion of whether intervention in the RAS could prevent in-stent restenosis. This review discusses the pathophysiology of in-stent restenosis, the role of the RAS in in-stent restenosis, and the possible role of RAS intervention in the prevention of in-stent restenosis.

Angiotensin Antagonism in Coronary Artery Disease

The renin-angiotensin system (RAS) is an ancient and complex cascade of homeostatic reactions aimed at regulating primordial functions that ensure organ perfusion through the control of blood pressure and the regulation of renal-cardiac activity. However, the over-expression or lack of compensatory mechanisms of any of its components may initiate detrimental effects that potentially lead to disease, a balance that makes the RAS a sequence with a labile physiological equilibrium and with a strong harm potential. These characteristics of the RAS in general, and of the angiotensin converting enzyme (ACE) in particular, make it not only an important complex for the regulation of blood pressure and neuropeptide metabolism, but also a fascinating subject of study from a biochemical, evolutionary and genetic point of view. Pharmacological interventions that influence the RAS by inhibiting the ACE or the angiotensin II type 1 receptor (AT1R) have demonstrated sustained efficacy in reducing the incidence of cardiovascular events and, consequently, vascular mortality in several clinical situations. ACE inhibitors and angiotensin II receptor antagonists (ARAs) reduce blood pressure and have cardio- and vasculoprotective effects. Anti-atherosclerotic effects have also been attributed to these drugs. For these reasons, it has been hypothesised that RAS inhibitors could also reduce the recurrence of ischaemic events after myocardial revascularisation procedures, namely coronary artery by-pass graft surgery (CABG) or percutaneous coronary interventions (PCI). Information available on the effect of ACE inhibitors and ARAs in patients with coronary artery disease (CAD) previously treated with revascularisation techniques indicates a substantial reduction of mortality and infarction in these patients. However, data regarding the progression of CAD, restenosis or reocclusion of vascular conduits of the coronary circulation after myocardial revascularisation are inconsistent. In most studies, the administration of ACE inhibitors neither improved the ischaemic threshold nor reduced the need for new revascularisation procedures. On the contrary, ACE inhibitors have been associated with higher restenosis rates after PCI in some retrospective series. Conversely, a single, exploratory randomised trial demonstrated that the selective AT1R antagonist valsartan significantly reduced stent restenosis after PCI. In patients undergoing CABG, ACE inhibitors did not reduce the risk of graft degeneration or occlusion. Studies that evaluated a possible anti-atherosclerotic effect of ACE inhibitors (including some large randomised trials) have generally been negative.

Intracoronary β-irradiation prevents excessive in-stent neointimal proliferation in de novo lesions of patients with high plasma ACE levels. The BetAce randomized trial

BACKGROUND

This study evaluated vascular brachytherapy (VBT) as a potent antiproliferative treatment to prevent in-stent restenosis (ISR) after coronary angioplasty of de novo lesions in patients carrying the D allele of the I/D polymorphism of the ACE gene and high ACE plasma levels (>34 U/l).

METHODS AND MATERIALS

A prospective randomized trial was designed to detect a 30% improvement in the minimal lumen diameter (MLD) of the stenotic artery, as measured by quantitative coronary analysis (QCA), 6 months following VBT at the time of stented angioplasty. All patients were carriers of the D allele of the ACE gene, with plasma ACE levels >34 U/l.

RESULTS

Thirty-one patients (33 stenoses) were allocated to stent implantation (control group) and 30 patients (31 stenoses) to VBT and stented angioplasty. After angioplasty, in-stent MLD was similar in the two groups. At 6 months in the control group, in-stent MLD had decreased to 1.74+/-0.8 versus 2.25+/-1.05 mm in the VBT group (P=.04). The mean in-stent diameter was 2.3+/-0.8 mm in the control group versus 2.9+/-1.05 mm after VBT (P=.02), and the restenosis rate was 37.5% versus 17.9%, respectively (P=.08). At 6 months, a higher need for target vessel revascularization (TVR) was observed in the control group: 35.5% versus 13.3% (P=.04).

CONCLUSIONS

This randomized study confirms that patients with high plasma ACE concentrations are exposed to an increased risk for ISR after coronary stenting. The preventive use of VBT in these patients reduced neointimal formation by 65% such that the MLD at follow-up was increased by 29% compared with the control group.