Feasibility and accuracy of a comprehensive multidetector computed tomography acquisition for patients referred for balloon-expandable transcatheter aortic valve implantation.

BACKGROUND: The aim of this study was to assess the accuracy of a comprehensive multidetector computed tomography (MDCT) evaluation of the aortic annulus (AoA), coronary artery disease (CAD), and peripheral vessels in patients referred for transcatheter aortic valve implantation (TAVI). METHODS: In 60 patients referred for TAVI, the following parameters were assessed with 64-slices MDCT and compared with transesophageal echocardiography (TEE), invasive coronary angiography (ICA), and peripheral angiography: AoA maximum diameter (Max-AoA-D(MDCT)), minimum diameter (Min-AoA-D(MDCT)), and area; lumen morphology index ([Max-AoA-D(MDCT)/Min-AoA-D(MDCT)]); length of the left, right, and non-coronary aortic leaflets; degree (grades 1-4) of aortic leaflet calcifications; distance between AoA and left main coronary ostium and between AoA and right coronary ostium CAD and peripheral vessel disease. RESULTS: The Max-AoA-D(MDCT) and Min-AoA-D(MDCT) were 25.1 ± 2.8 and 21.2 ± 2.2 mm, respectively, with high correlation versus AoA diameter measured with TEE (r = 0.82 and 0.86, respectively). The area of AoA, systolic and diastolic lumen morphology index were 410 ± 81.5 mm(2), 1.19 ± 0.1 and 1.22 ± 0.11, respectively. Aortic leaflet calcification score was 3.3 ± 0.5. The lengths of left, right, and non-coronary aortic leaflets were 14.2 ± 2.4, 13.7.1 ± 2.1, and 14.5 ± 2.6 mm, whereas distances between AoA and the left main coronary ostium and between AoA, and the right coronary ostium were 13.7 ± 2.9 and 15.8 ± 3.5 mm, respectively. Feasibility, negative predictive value, and accuracy for CAD detection versus ICA were 87%, 100% (CI 100-100), and 96% (95% CI 94-100), respectively. All patients (N = 17) who were ineligible for TAVI were correctly detected by MDCT. CONCLUSIONS: A comprehensive MDCT evaluation of patients referred for TAVI is feasible, provides more accurate assessment than TEE of AoA morphology, and may replace peripheral angiography in all patients and ICA in patients without significant CAD.

Endovascular treatment of abdominal aortic aneurysm after previous left pneumonectomy: a sound choice.

Surgical treatment of abdominal aortic aneurysm after previous pneumonectomy is a challenge because of the impaired respiratory function and increased surgical risks. Endovascular aneurysm repair in anatomically suited high-surgical-risk patients offers excellent short-term results and provides good protection from aneurysm-related death. In this article, we report a successful endovascular aneurysm repair of an infrarenal aortic aneurysm in a patient with past left pneumonectomy.

Circulating microRNAs are new and sensitive biomarkers of myocardial infarction.

AIMS: Circulating microRNAs (miRNAs) may represent a novel class of biomarkers; therefore, we examined whether acute myocardial infarction (MI) modulates miRNAs plasma levels in humans and mice. METHODS AND RESULTS: Healthy donors (n = 17) and patients (n = 33) with acute ST-segment elevation MI (STEMI) were evaluated. In one cohort (n = 25), the first plasma sample was obtained 517 ± 309 min after the onset of MI symptoms and after coronary reperfusion with percutaneous coronary intervention (PCI); miR-1, -133a, -133b, and -499-5p were ~15- to 140-fold control, whereas miR-122 and -375 were ~87-90% lower than control; 5 days later, miR-1, -133a, -133b, -499-5p, and -375 were back to baseline, whereas miR-122 remained lower than control through Day 30. In additional patients (n = 8; four treated with thrombolysis and four with PCI), miRNAs and troponin I (TnI) were quantified simultaneously starting 156 ± 72 min after the onset of symptoms and at different times thereafter. Peak miR-1, -133a, and -133b expression and TnI level occurred at a similar time, whereas miR-499-5p exhibited a slower time course. In mice, miRNAs plasma levels and TnI were measured 15 min after coronary ligation and at different times thereafter. The behaviour of miR-1, -133a, -133b, and -499-5p was similar to STEMI patients; further, reciprocal changes in the expression levels of these miRNAs were found in cardiac tissue 3-6 h after coronary ligation. In contrast, miR-122 and -375 exhibited minor changes and no significant modulation. In mice with acute hind-limb ischaemia, there was no increase in the plasma level of the above miRNAs. CONCLUSION: Acute MI up-regulated miR-1, -133a, -133b, and -499-5p plasma levels, both in humans and mice, whereas miR-122 and -375 were lower than control only in STEMI patients. These miRNAs represent novel biomarkers of cardiac damage.

Impact of left ventricular systolic function on clinical and echocardiographic outcomes following transcatheter aortic valve implantation for severe aortic stenosis.

BACKGROUND: This study aimed to evaluate the impact of baseline left ventricular (LV) systolic function on clinical and echocardiographic outcomes following transcatheter aortic valve implantation (TAVI). Survival of patients undergoing TAVI was also compared with that of a population undergoing surgical aortic valve replacement. METHODS: One hundred forty-seven consecutive patients (mean age=80±7 years) undergoing TAVI in 2 centers were included. Mean follow-up period was 9.1±5.1 months. RESULTS: At baseline, 34% of patients had impaired LV ejection fraction (LVEF) (<50%) and 66% had normal LVEF (≥50%). Procedural success was similar in these 2 groups (94% vs 97%, P=.41). All patients achieved improvement in transvalvular hemodynamics. At follow-up, patients with a baseline LVEF<50% showed marked LV reverse remodeling, with improvement of LVEF (from 37%±8% to 51%±11%). Early and late mortality rates were not different between the 2 groups, despite a higher rate of combined major adverse cardiovascular events (MACEs) in patients with a baseline LVEF<50%. The predictors of cumulative MACEs were baseline LVEF (HR=0.97, 95% CI=0.94-0.99) and preoperative frailty (HR=4.20, 95% CI=2.00-8.84). In addition, long-term survival of patients with impaired or normal LVEF was comparable with that of a matched population who underwent surgical aortic valve replacement. CONCLUSIONS: TAVI resulted in significant improvement in LV function and survival benefit in high-risk patients with severe aortic stenosis, regardless of baseline LVEF. Patients with a baseline LVEF<50% were at higher risk of combined MACEs.

Incidental detection of a giant ductus arteriosus aneurysm by low-dose multidetector computed tomography in an asymptomatic adult.

Aneurysm of the ductus arteriosus is a very rare congenital lesion in adults that can be associated with thromboembolism, rupture, and death. Its detection in a silent clinical phase is very important for planning appropriate treatment and avoiding potentially fatal complications. We report a case of a patent ductus arteriosus aneurysm of very large size (65.5 mm) that was incidentally discovered with low-dose (3.2 mSv) multidetector computed tomography in an asymptomatic 67-year-old man. The presence of coronary disease was also ruled out with this non-invasive imaging modality. Further evaluation with echocardiography and selective angiography confirmed the diagnosis. At surgery, the aneurysm was successfully resected via a left posterolateral thoracotomy.

Transcatheter aortic valve replacement: a dog bone-shaped balloon technique.

We report a new technique of the partially and sequentially gonflage of the transcatheter balloon valve, the so called dog bone shaped technique, which allowed us to approach the aortic root by inflating the valve balloon in two different times, stabilizing the heart and deplacing the valve.

Nitric oxide modulates chromatin folding in human endothelial cells via protein phosphatase 2A activation and class II histone deacetylases nuclear shuttling.

Nitric oxide (NO) modulates important endothelial cell (EC) functions and gene expression by a molecular mechanism which is still poorly characterized. Here we show that in human umbilical vein ECs (HUVECs) NO inhibited serum-induced histone acetylation and enhanced histone deacetylase (HDAC) activity. By immunofluorescence and Western blot analyses it was found that NO induced class II HDAC4 and 5 nuclear shuttling and that class II HDACs selective inhibitor MC1568 rescued serum-dependent histone acetylation above control level in NO-treated HUVECs. In contrast, class I HDACs inhibitor MS27-275 had no effect, indicating a specific role for class II HDACs in NO-dependent histone deacetylation. In addition, it was found that NO ability to induce HDAC4 and HDAC5 nuclear shuttling involved the activation of the protein phosphatase 2A (PP2A). In fact, HDAC4 nuclear translocation was impaired in ECs expressing small-t antigen and exposed to NO. Finally, in cells engineered to express a HDAC4-Flag fusion protein, NO induced the formation of a macromolecular complex including HDAC4, HDAC3, HDAC5, and an active PP2A. The present results show that NO-dependent PP2A activation plays a key role in class II HDACs nuclear translocation.

Performance of EuroSCORE in CABG and off-pump coronary artery bypass grafting: single institution experience and meta-analysis.

AIMS: To assess EuroSCORE performance in predicting in-hospital mortality in on-pump coronary artery bypass grafting (CABG) and off-pump coronary artery bypass grafting (OPCAB). METHODS AND RESULTS: Additive and logistic EuroSCORE were computed for consecutive patients undergoing CABG (n = 3440, 75%) or OPCAB (n = 1140, 25%) at our hospital from 1999 to September 2007. The areas under the receiver operating characteristic (ROC) curves (AUCs) were used to describe performance and accuracy. No difference in performance between CABG and OPCAB and between additive and logistic EuroSCORE (additive EuroSCORE AUCs of 0.808 and 0.779 for CABG and OPCAB, respectively; logistic EuroSCORE AUCs of 0.813 and of 0.773 for CABG and OPCAB, respectively) was found, although a marked tendency to overpredict mortality by both models was evident. A meta-analysis of previously published data was done, and a total of eight studies representing 19 212 and 5461 patients undergoing CABG and OPCAB, respectively, met inclusion criteria. Meta-analysis confirmed similar performance of EuroSCORE in CABG and OPCAB: estimated AUCs were 0.767 and 0.766 for CABG and OPCAB, respectively, with an estimated difference of 0.001 (95% CI -0.061 to 0.063). CONCLUSION: Additive and logistic EuroSCORE algorithms performed similarly, and cumulative evidence suggests comparable performance in CABG and OPCAB procedures; both risk models, however, significantly overestimated mortality.

Atrial fibrillation after isolated coronary surgery affects late survival.

BACKGROUND: Atrial fibrillation (AF) after coronary artery bypass graft surgery is a difficult problem and a continuing source of morbidity and mortality. However, the prognostic implications of postoperative AF are still in dispute. Our aim was to ascertain the impact of AF after coronary artery bypass graft on postoperative survival and to assess its prognostic role in cause-specific mortality. METHODS AND RESULTS: We conducted a prospective observational study of 1832 patients undergoing isolated coronary artery bypass graft between January 2000 and December 2005 at 2 cardiac surgery centers in northern Italy. Patients affected by postoperative AF were identified and followed up until death or study end (April 30, 2007). A total of 570 patients (31%) developed AF after coronary surgery. Patients affected by postoperative AF experienced a longer hospital stay (7 days [25th to 75th percentile, 7 to 10 days] versus 7 days [25th to 75th percentile, 6 to 8 days]; P<0.001). Hospital mortality also was higher in AF patients (3.3% versus 0.5%; P<0.001). On discharge, 1806 patients were alive; 143 were lost to follow-up. The remaining 1663 were followed up for a median of 51 months (25th to 75th percentile, 41 to 63 months); 126 of them died after a median of 14 months (25th to 75th percentile, 5 to 32 months). Long-term mortality rates were significantly higher for patients with postoperative AF (2.99 per 100 person-years; 95% confidence interval, 2.33 to 3.84; 61 deaths) compared with those without the arrhythmia (1.34 per 100 person-years; 95% confidence interval, 1.05 to 1.71; 65 deaths), with an adjusted hazard ratio of 2.13 (P<0.001) and 2.56 (P=0.001) when also accounting for the prescription of warfarin at discharge. With Cox regression, patients with AF were shown to be at higher risk of dying from embolism (adjusted hazard ratio, 4.33; 95% confidence interval, 1.78 to 10.52) but not from other causes. CONCLUSIONS: Postoperative AF affects early and late mortality after isolated coronary artery bypass graft surgery. Patients affected by AF are at higher risk of fatal embolic events. Careful postoperative surveillance with a specific antiarrhythmic and antithrombotic prophylaxis, aimed at reducing AF and its complications, is recommended.

Tissue factor in patients with acute coronary syndromes: expression in platelets, leukocytes, and platelet-leukocyte aggregates.

OBJECTIVE: Activated platelets and circulating platelet-leukocyte aggregates (PLA) are significantly higher in patients with unstable angina than in those with stable angina (SA). Platelets from healthy subjects express TF on activation. The aim of this study was to investigate the expression of TF in PLA, in platelets, and in monocytes of acute coronary syndrome (ACS) patients compared to SA patients and healthy subjects (Controls). METHODS AND RESULTS: We enrolled 26 consecutive patients with ACS, 29 patients with SA, and 25 Controls. A significantly greater number of total and TF positive platelet-monocyte aggregates was found by flow cytometry in blood of ACS patients than in either SA patients (3-fold) or Controls (5-fold). ACS patients also had a significantly higher amount of TF-positive platelets than SA or Controls (>3-fold) and significantly higher thrombin generation capacity. TF mRNA expression in platelets was significantly higher in ACS patients than in SA or Controls. CONCLUSIONS: In ACS patients the greater expression of TF in platelets and PLA strengthens the link between platelet activation, blood coagulation, and thrombus formation and may further contribute to the hypercoagulability associated with the disease.

Oxidized proteins in plasma of patients with heart failure: role in endothelial damage.

BACKGROUND: Oxidative stress is increased in the failing heart, and this might contribute to the pathogenesis of myocardial remodelling and heart failure (HF). AIM: To identify the oxidized proteins in plasma of chronic HF patients and to evaluate their possible role in endothelial damage. METHODS: Plasma levels of oxidized proteins were measured by immunoassay and by analysis in albumin and immunoglobulin depleted plasma using a proteomic approach, in 40 HF patients and in 20 age-matched normal subjects. Analysis of the effects of proteins oxidized in vitro on human endothelial cell (EC) viability was also performed. RESULTS: Plasma levels of oxidized proteins were significantly higher in HF patients than in controls (p<0.01). We identified two proteins, alpha-1-antitrypsin and fibrinogen, which underwent oxidation. Oxidation of alpha-1-antitrypsin resulted in loss of its protease inhibitor activity, thus leading to EC death in the presence of elastase. Fibrinogen, when oxidized, became otherwise cytotoxic and induced apoptosis in EC. CONCLUSIONS: This study shows that plasma levels of oxidized proteins are increased in HF, and permitted the identification of two proteins, namely alpha-1-antitrypsin and fibrinogen, which underwent oxidation. In vitro results highlighted the potential role of oxidized proteins in the EC damage that occurs in HF.

On- and off-pump coronary surgery and perioperative myocardial infarction: an issue between incomplete and extensive revascularization.

OBJECTIVE: Complete myocardial revascularization is the standard for coronary artery bypass grafting. It has been shown, however, that off-pump coronary bypass surgery (OPCAB) may reduce completeness of revascularization without affecting perioperative myocardial infarction rates. We evaluated the influence of OPCAB on major postoperative events in a large consecutive cohort of patients, with special emphasis on risk factors for perioperative myocardial infarction. METHODS: From 1995 to 2004, 5935 patients underwent isolated coronary bypass surgery; of these, 4623 (77.9%) and 1312 (22.1%) underwent on-pump coronary surgery (CABG) and OPCAB, respectively. Patients undergoing OPCAB were matched to patients undergoing CABG by propensity score; logistic regression analysis models were used to study predictors of perioperative myocardial infarction. RESULTS: In matched pairs, postoperative mortality, myocardial infarction, stroke, and atrial fibrillation were similar between groups, while reoperation for bleeding, time on ventilator and red blood cell use were lower in patients undergoing OPCAB. The number of distal anastomoses was lower in patients undergoing OPCAB (2.2+/-0.80 in OPCAB vs 2.9+/-0.86 in CABG, p<0.001), as well as complete revascularization rates (61.9% in OPCAB vs 90.0% in CABG, p<0.001). Multivariate analyses, performed on preoperative and intraoperative variables, showed that both incomplete revascularization and increasing numbers of distal anastomoses (even when controlling for completeness of revascularization) were significant predictors of perioperative myocardial infarction, while CABG/OPCAB strategy did not influence it. CONCLUSIONS: The choice of surgical technique did not influence the occurrence of major perioperative complications and of myocardial infarction, which is negatively affected by incomplete or too extensive revascularization strategies.

Long-term survival after salvage surgery for invasive thymoma with intracardiac extension.

We report a case of successful salvage surgery for invasive thymoma initially judged to be unresectable that did not respond to sequential chemoradiotherapy. The patient underwent en bloc resection of the tumor, superior vena cava, upper portion of the right atrium (RA) and intracardiac neoplastic thrombus with the aid of a cardiopulmonary bypass without cardiac arrest. The patient is disease free 8.5 years after radical thymectomy and subsequent resection of 2 second primary lung adenocarcinomas.

Intraoperative antiaggregant strategy for off-pump coronary artery bypass grafting in a patient with heparin-induced thrombocytopenia.

Immune heparin-induced thrombocytopenia is a rare complication of heparin administration. We describe a patient with a previous diagnosis of heparin-induced thrombocytopenia and related contraindications to anticoagulation who underwent urgent off-pump myocardial revascularization with the administration of only antiaggregant therapy.

Cyclin D1 degradation enhances endothelial cell survival upon oxidative stress.

The understanding of endothelial cell responses to oxidative stress may provide insights into aging mechanisms and into the pathogenesis of numerous cardiovascular diseases. In this study, we examined the regulation and the functional role of cyclin D1, a crucial player in cell proliferation and survival. On H2O2 treatment, endothelial cells showed a rapid down-modulation of cyclin D1. Other D-cyclins were similarly regulated, and this decrease was also observed after exposure to other oxidative stress-inducing stimuli, namely 1,3-bis (2 chloroethyl)-1 nitrosourea treatment and ischemia. H2O2 treatment induced cyclin D1 ubiquitination followed by proteasome degradation. Phospholipase C inhibition prevented cyclin D1 degradation, and its activation triggered cyclin D1 down-modulation in the absence of oxidative stress. Activated phospholipase C generates inositol-1,4,5-trisphosphate (IP3) and Ca2+ release from internal stores. We found that both IP3-receptor inhibition and intracellular Ca2+ chelation prevented cyclin D1 degradation induced by oxidative stress. Furthermore, Ca2+ increase was transduced by Ca2+/calmodulin-dependent protein kinase (CaMK). In fact, H2O2 stimulated CaMK activity, CaMK inhibitors prevented H2O2-induced cyclin D1 down-modulation, and CaMK overexpression induced cyclin D1 degradation. Finally, overriding of cyclin D1 down-modulation via its forced overexpression or via CaMK inhibition increased cell sensitivity to H2O2-induced apoptotic cell death. Thus, cyclin D1 degradation enhances endothelial cell survival on oxidative stress.

Epigenetic histone modification and cardiovascular lineage programming in mouse embryonic stem cells exposed to laminar shear stress.

Experimental evidence indicates that shear stress (SS) exerts a morphogenetic function during cardiac development of mouse and zebrafish embryos. However, the molecular basis for this effect is still elusive. Our previous work described that in adult endothelial cells, SS regulates gene expression by inducing epigenetic modification of histones and activation of transcription complexes bearing acetyltransferase activity. In this study, we evaluated whether SS treatment could epigenetically modify histones and influence cell differentiation in mouse embryonic stem (ES) cells. Cells were exposed to a laminar SS of 10 dyne per cm2/s(-1), or kept in static conditions in the presence or absence of the histone deacetylase inhibitor trichostatin A (TSA). These experiments revealed that SS enhanced lysine acetylation of histone H3 at position 14 (K14), as well as serine phosphorylation at position 10 (S10) and lysine methylation at position 79 (K79), and cooperated with TSA, inducing acetylation of histone H4 and phosphoacetylation of S10 and K14 of histone H3. In addition, ES cells exposed to SS strongly activated transcription from the vascular endothelial growth factor (VEGF) receptor 2 promoter. This effect was paralleled by an early induction of cardiovascular markers, including smooth muscle actin, smooth muscle protein 22-alpha, platelet-endothelial cell adhesion molecule-1, VEGF receptor 2, myocyte enhancer factor-2C (MEF2C), and alpha-sarcomeric actin. In this condition, transcription factors MEF2C and Sma/MAD homolog protein 4 could be isolated from SS-treated ES cells complexed with the cAMP response element-binding protein acetyltransferase. These results provide molecular basis for the SS-dependent cardiovascular commitment of mouse ES cells and suggest that laminar flow may be successfully applied for the in vitro production of cardiovascular precursors.

Resection and end-to-end anastomosis for ascending aortic aneurysms associated with a bicuspid valve: case reports.

Ascending aortic aneurysms associated with a bicuspid valve are generally treated by replacement with a tubular graft because the aortic wall is claimed to be genetically pathological. We describe 9 cases in which patients with an ascending aortic aneurysm and an associated diseased bicuspid valve underwent aneurysmal resection and end-to-end anastomosis. This technique permitted us to remove the entire aneurysmal wall, avoiding graft interposition.

Shear stress-mediated chromatin remodeling provides molecular basis for flow-dependent regulation of gene expression.

Shear stress (SS), the tangential component of hemodynamic forces, modulates the expression of several genes in endothelial cells. However, no information is available about its effect on chromatin structure, which plays a key role in gene transcription. In this study, a link between SS and chromatin remodeling was established in human umbilical vein endothelial cells (HUVECs). HUVECs were exposed to SS of 10 dyne/cm2 per second, in the presence or absence of the histone deacetylase inhibitor trichostatin A, and assayed for histone H3 and histone H4 modifications. SS induced histone H3 serine phosphorylation at position 10 (S10) and lysine acetylation at position 14 (K14) but required trichostatin A to induce H3 phosphoacetylation and H4 acetylation. The phosphatidylinositol 3-kinase inhibitor wortmannin and the mitogen-activated protein kinase inhibitor PD98059 decreased SS-dependent histone H3 phosphorylation, without affecting its acetylation; the p38 inhibitor SB203580 reduced both H3 phosphorylation and acetylation, whereas the protein kinase A inhibitor PKI-tide reduced histone H3 acetylation. Remarkably, the abrogation of histone acetylation inhibited SS-dependent c-fos expression. SS also activated ribosomal S6 kinase-2 and mitogen- and stress-activated kinase-1 protein kinases and promoted the formation of a cAMP-responsive element-binding protein (CREB)/CREB-binding protein complex, providing the molecular basis for the increase in histone acetyltransferase activity observed in HUVECs exposed to SS. Finally, the effect of SS on chromatin remodeling was examined. In HUVECs exposed to SS, chromatin within c-fos and c-jun promoters was specifically immunoprecipitated by an antibody against acetylated histone H3 on K14. These results indicate that SS induces posttransduction modifications of histones; this is an early step toward the flow-dependent regulation of gene expression.

Enhanced arteriogenesis and wound repair in dystrophin-deficient mdx mice.

BACKGROUND: The absence of functional dystrophin in Duchenne muscular dystrophy (DMD) patients and in mdx mice results in progressive muscle degeneration associated with necrosis, fibrosis, and inflammation. Because vascular supply plays a key role in tissue repair, we examined whether new blood vessel development was altered in mdx mice. METHODS AND RESULTS: In a model of hindlimb ischemia on femoral artery dissection, hindlimb perfusion, measured by laser Doppler imaging, was higher in mdx mice (0.67+/-0.26) than in wild-type (WT) mice (0.33+/-0.18, P<0.03). In keeping with these data, a significant increase in arteriole length density was found in mdx mice (13.6+/-8.4 mm/mm3) compared with WT mice (7.8+/-4.6 mm/mm3, P<0.03). Conversely, no difference was observed in capillary density between mice of the 2 genotypes. The enhanced regenerative response was not limited to ischemic skeletal muscle, because in a wound-healing assay, mdx mice showed an accelerated wound closure rate compared with WT mice. Moreover, a vascularization assay in Matrigel plugs containing basic fibroblast growth factor injected subcutaneously revealed an increased length density of arterioles in mdx (46.9+/-14.7 mm/mm3) versus WT mice (19.5+/-5.8 mm/mm3, P<0.001). Finally, serum derived from mdx mice sustained formation of endothelium-derived tubular structures in vitro more efficiently than WT serum. CONCLUSIONS: These results demonstrate that arteriogenesis is enhanced in mdx mice both after ischemia and skin wounding and in response to growth factors.

p66ShcA modulates tissue response to hindlimb ischemia.

BACKGROUND: Oxidative stress plays a pivotal role in ischemia and ischemia/reperfusion injury. Because p66(ShcA)-null (p66(ShcA)-/-) mice exhibit both lower levels of intracellular reactive oxygen species and increased resistance to cell death induced by oxidative stress, we investigated whether tissue damage that follows acute ischemia or ischemia/reperfusion was altered in p66(ShcA)-/- mice. METHODS AND RESULTS: Unilateral hindlimb ischemia was induced by femoral artery dissection, and ischemia/reperfusion was induced with an elastic tourniquet. Both procedures caused similar changes in blood perfusion in p66(ShcA) wild-type (p66(ShcA)wt) and p66(ShcA)-/- mice. However, significant differences in tissue damage were found: p66(ShcA)wt mice displayed marked capillary density decrease and muscle fiber necrosis. In contrast, in p66(ShcA)-/- mice, minimal capillary density decrease and myofiber death were present. When apoptosis after ischemia was assayed, significantly lower levels of apoptotic endothelial cells and myofibers were found in p66(ShcA)-/- mice. In agreement with these data, both satellite muscle cells and endothelial cells isolated from p66(ShcA)-/- mice were resistant to apoptosis induced by simulated ischemia in vitro. Lower apoptosis levels after ischemia in p66(ShcA)-/- cells correlated with decreased levels of oxidative stress both in vivo and in vitro. CONCLUSIONS: p66(ShcA) plays a crucial role in the cell death pathways activated by acute ischemia and ischemia/reperfusion, indicating p66(ShcA) as a potential therapeutic target for prevention and treatment of ischemic tissue damage.