Long-term inhibition of myocardial infarction by postconditioning during reperfusion

Cardioprotection with postconditioning has been well demonstrated after a short period of reperfusion. This study tested the hypothesis that postconditioning reduces infarct size, vascular dysfunction, and neutrophil accumulation after a long-term reperfusion. Canines undergoing 60 min left anterior descending artery (LAD) occlusion were divided into two control groups of either 3 h or 24 h of full reperfusion and two postconditioning groups with three 30 s cycles of reperfusion and re-occlusion applied at the onset of either 3 h or 24 h of reperfusion. Size of the area at risk (AAR) and collateral blood flow during ischemia were similar among groups. In controls, infarct size as percentage of the AAR (30 ± 3 vs. 39 ± 2* %) by TTC staining, superoxide anion generation from the post-ischemic coronary arteries by lucigenin-enhanced chemiluminescence [(89 ± 5 vs. 236 ± 27* relative light units (RLU/mg)], and neutrophil (PMN) accumulation by immunohistochemical staining in the AAR (52 ± 11 vs. 84 ± 14* cells/mm² myocardium) significantly increased between 3 and 24 h of reperfusion. Postconditioning reduced infarct size (15 ± 4† and 27 ± 3.6† %), superoxide anion generation (24 ± 4† and 43 ± 11† RLU/mg), and PMN accumulation (19 ± 6† and 45 ± 8† cells/mm² myocardium) in the 3 and 24 h reperfusion groups relative to time-matched controls. These data suggest that myocardial injury increases with duration of reperfusion; reduction in infarct size and attenuation in inflammatory responses with postconditioning persist after a prolonged reperfusion. * p < 0.05 24 vs. 3 h control; † p < 0.05 postconditioning vs. time-matched control.     

In Vivo Cardioprotection by N-Acetylcysteine and Isosorbide 5-Mononitrate in a Rat Model of Ischemia-Reperfusion

Aims: We evaluated the effect of N-acetylcysteine (NAC, infused i.v.), isosorbide 5-mononitrate (IS5MN, by gavage), or their combination on cardiac injury in an in vivo rat model of 30-min ischemia followed by 24 hours or 7 days of reperfusion. Results: When administered immediately prior to reperfusion with continuous infusion for 24 h, the combination of NAC + IS5MN reduced infarct size (29 ± 6 vs. 59 ± 4% area-at-risk, p < 0.01) and the infiltration of polymorphonuclear leukocytes (226 ± 15 vs. 315 ± 18 cells mm^–2 of area-at-risk, p = 0.002) and monocytes/macrophages (118 ± 8 vs. 194 ± 22 cells mm^–2, p = 0.012), compared to vehicle. NAC or IS5MN alone did not reduce infarct size at 24 hours of reperfusion. The same dose regimen of NAC and IS5MN did not reduce infarct size with permanent ischemia for 24 hours not followed by reperfusion. After 7 days of reperfusion (3 days of treatment with NAC + IS5MN or vehicle and 4 days of wash-out), infarct size was similar in the vehicle and NAC + IS5MN groups, but LV end-diastolic pressure and diastolic LV chamber wall stress were significantly lower in the animals treated with NAC + IS5MN (5 ± 1 mmHg and 62 ± 7 dyne mm^–2, respectively) compared to vehicle (9 ± 1 mmHg and 123 ± 18 dyne mm^–2, p < 0.05). Conclusion: We demonstrate in a rat model of cardiac ischemia-reperfusion treated with NAC and IS5MN, according to a regimen that mimicked a clinical situation (drugs started at time of reperfusion), that the short-term benefit seen after 24 h of reperfusion (51% reduction of infarct size) is maintained after one week, possibly through modulation of the inflammatory response to cardiac injury.     

A critical challenge: Dosage-related efficacy and acute complication intracoronary injection of autologous bone marrow mesenchymal stem cells in acute myocardial infarction

Background

Previous studies showed improvement in heart function by injecting bone marrow mesenchymal stem cells (BMSCs) after AMI. Emerging evidence suggested that both the number and function of BMSCs decline with ageing. We designed a randomized, controlled trial to further investigate the safety and efficacy of this treatment.

Methods

Patients with ST-elevation AMI undergoing successful reperfusion treatment within 12 hours were randomly assigned to receive an intracoronary infusion of BMSCs (n = 21) or standard medical treatment (n = 22) (the numbers of patients were limited because of the complication of coronary artery obstruction).

Results

There is a closely positive correlation of the number and function of BMSCs vs. the cardiac function reflected by LVEF at baseline (r = 0.679, P = 0.001) and at 12-month follow-up (r = 0.477, P = 0.039). Six months after cell administration, myocardial viability within the infarct area by 18-FDG SPECT was improved in both groups compared with baseline, but no significant difference in the BMSCs compared with control groups (4.0 ± 0.4% 95%CI 3.1–4.9 vs. 3.2 ± 0.5% 95%CI 2.1–4.3, P = 0.237). 99mTc-sestamibi SPECT demonstrated that myocardial perfusion within the infarct area in the BMSCs did not differ from the control group (4.4 ± 0.5% 95%CI 3.2–5.5 vs. 3.9 ± 0.6% 95%CI 2.6–5.2, P = 0.594). Similarly, LVEF after 12 and 24 months follow-up did not show any difference between the two groups. In the BMSCs group, one patient suffered a serious complication of coronary artery occlusion during the BMSCs injection procedure.

Conclusions

The clinical benefits of intracoronary injection of autologous BMSCs in acute STEMI patients need further investigation and reevaluation.     

Postconditioning’s protection is not dependent on circulating blood factors or cells but involves adenosine receptors and requires PI3–kinase and guanylyl cyclase activation

Protection from postconditioning has been documented in in situ animal models and it has been proposed that it is targeting circulating leukocytes. We therefore tested whether postconditioning can protect leukocytefree, buffer–perfused rabbit hearts. Infarct size was measured with triphenyltetrazolium staining. In control hearts undergoing 30 min of regional ischemia and 2 h of reperfusion, 33.3 ± 2.2% of the risk zone infarcted. The protocol previously used in open–chest animals of four postconditioning cycles of 30 s reperfusion/30 s ischemia starting at the beginning of reperfusion decreased infarction to only 24.8 ± 2.5% of the risk zone in these isolated hearts. Because of the meager protection induced by four 30 s postconditioning cycles, we evaluated the effect of postconditioning with 6 cycles of 10 s reperfusion/10 s ischemia starting at the beginning of reperfusion. Robust salvage was seen with only 10.4 ± 3.4% of the risk zone infarcting (p < 0.001 vs control and p < 0.003 vs 4 cycles of 30 s ischemia). The 10s protocol was used in all studies of signal transduction. Wortmannin (100 nM), a phosphatidylinositol 3– (PI3–) kinase antagonist, infused for 20 min starting 5 min before reperfusion, blocked postconditionings, protection (31.2 ± 4.2% infarction) as did 1H–[1,2,4]oxadiazole[4,3–a]quinoxalin–1–one (ODQ) (2 µM) a guanylyl cyclase inhibitor (36.9 ± 5.3%) and 8–p–(sulfophenyl) theophylline (SPT) (100 µM), a non–specific adenosine receptor blocker (34.2 ± 2.8%). Thus, postconditionings protection is not dependent on circulating blood factors or cells, and its anti–infarct effect appears to require PI3–kinase activation, stimulation of guanylyl cyclase and occupancy of adenosine receptors. These signaling steps have also been identified in preconditioning and during pharmacologic cardioprotection and suggest commonality of a protective mechanism.This revised version was published online in December 2004 with a minor correction to the article title     

Frequent biomarker analysis in the isolated perfused heart reveals two distinct phases of reperfusion injury

Background

Reperfusion injury and its modulation are incompletely characterized. The purpose of the present study was to characterize the dynamics of reperfusion injury by portraying the temporal release of lactate dehydrogenase (LDH) during ischemia–reperfusion injury in an isolated heart model.

Methods

We studied infarct size and LDH release in the following groups: I) Effect of reperfusion length was evaluated in 79 rats subjected to 40 minute ischemia and 60, 90, 120 or 180 minute reperfusion and a) ischemic preconditioning (IPC) or b) No IPC (control). II) LDH release kinetics was studied in 6 rats subjected to calcium-paradox to verify the applicability of LDH as a dynamic marker of cellular injury. III) Ischemia–reperfusion injury modification was studied in 36 rats subjected to: a) ischemic postconditioning, b) prolonged ischemia, c) Reperfusion Injury Salvage Kinase (RISK) pathway inhibition with wortmannin in IPC hearts, d) RISK activation with insulin or e) mitochondrial permeability transition pore (mPTP) inhibition with cyclosporine A.

Results

Infarct size increased from 60 to 180 minute reperfusion in control hearts. LDH was released in two separate peaks from 2 to 20 and 30 to 120 min of reperfusion. IPC attenuated both peaks. Postconditioning and agents known to modify reperfusion injury attenuated the second peak.

Conclusions

Frequent measurement of myocardial ischemia markers for 120 min of reperfusion allows identification of two phases of reperfusion injury that are affected by cardioprotective stimuli. The second phase contributes significantly to final infarct size, which is modifiable and a potential target for cardioprotective interventions.     

Association of virtual histology characteristics of the culprit plaque with post-fibrinolysis flow restoration in ST-elevation myocardial infarction

Objectives

We sought to test the hypothesis that virtual histology characteristics of the culprit lesion in patients with ST-elevation myocardial infarction are associated with blood flow restoration after thrombolysis.

Methods

Consecutive patients referred for coronary angiography after successful thrombolysis were included in this correlational cross-sectional study. Evaluation with intravascular ultrasound (IVUS) and virtual histology of the culprit arterial segment was performed in all cases.

Results

Forty-eight patients (60.5 ± 10.7 years) were included. TIMI flow grade 3 was found in 24 (50%). Diabetes was strongly associated with lower TIMI flow 3 rate (26.7% vs 60.6%; p = 0.029) and there was a significant difference in the time to thrombolysis (2.0 ± 0.8 hours in those with TIMI flow 3 vs 3.0 ± 0.7 hours in TIMI flow grades 1–2; p < 0.001). Patients with TIMI flow grades 3 and 1–2 had similar absolute total plaque volume (152.8 ± 59.3 mm³ vs 147.5 ± 92.3 mm³; p = 0.817) and absolute necrotic core (NC) volume (31.2 ± 13.9 mm³ vs 33.6 ± 23.2 mm³; p = 0.671). However, there were significant differences in the relative NC content, both in proportion to the whole plaque volume (26.3% vs 29.9%; p = 0.016) and as an area fraction at the largest NC site (31.5% vs 40.3%; p < 0.001).

Conclusion

The NC content of atherosclerotic plaques is meaningful for flow restoration after the occurrence of a coronary event. This finding highlights the importance of plaque composition, as studied with virtual histology, not only for the sequence of processes leading to an acute plaque-related event, but also for thrombus formation and lysis, following the occurrence of such an event.     

Comprehensive analysis of intravascular ultrasound and angiographic morphology of culprit lesions between ST-segment elevation myocardial infarction and non-ST-segment elevation acute coronary syndrome

Background

Some plaques lead to ST-segment elevation myocardial infarction (STEMI), whereas others cause non-ST-segment elevation acute coronary syndrome (NSTEACS). We used angiography and intravascular ultrasound (IVUS) to investigate the difference of culprit lesion morphologies in ACS.

Methods

Consecutive 158 ACS patients whose culprit lesions were imaged by preintervention IVUS were enrolled (STEMI = 81; NSTEACS = 77). IVUS and angiographic findings of the culprit lesions, and clinical characteristics were compared between the groups.

Results

There were no significant differences in patients' characteristics except for lower rate of statin use in patients with STEMI (20% vs 44%, p = 0.001). Although angiographic complex culprit morphology (Ambrose classification) and thrombus were more common in STEMI than in NSTEACS (84% vs 62%, p = 0.002; 51% vs 5%, p < 0.0001, respectively), SYNTAX score was lower in STEMI (8.6 ± 5.4 vs 11.5 ± 7.1, p = 0.01). In patients with STEMI, culprit echogenicity was more hypoechoic (64% vs 40%, p = 0.01), and the incidence of plaque rupture, attenuation and “microcalcification” were significantly higher (56% vs 17%, p < 0.0001; 85% vs 69%, p = 0.01; 77% vs 61%, p = 0.04, respectively). Furthermore, the maximum area of ruptured cavity, echolucent zone and arc of microcalcification were significantly greater in STEMI compared with NSTEACS (1.80 ± 0.99 mm² vs 1.13 ± 0.86 mm², p = 0.006; 1.52 ± 0.74 mm² vs 1.21 ± 0.81 mm², p = 0.004; 99.9 ± 54.6° vs 77.4 ± 51.2°, p = 0.01, respectively). Quantitative IVUS analysis showed that vessel and plaque area were significantly larger at minimum lumen area site (16.6 ± 5.4 mm² vs 14.2 ± 5.5 mm², p = 0.003; 13.9 ± 5.1 mm² vs 11.6 ± 5.2 mm², p = 0.003, respectively).

Conclusion

Morphological feature (outward vessel remodeling, plaque buildup and IVUS vulnerability of culprit lesions) might relate to clinical presentation in patients with ACS.     

The contribution of stem cell therapy to skeletal muscle remodeling in heart failure

Background

The aim of our study was to investigate whether stem cell (SC) therapy with human amniotic fluid stem cells (hAFS, fetal stem cells) and rat adipose tissue stromal vascular fraction cells–GFP positive cells (rSVC-GFP) was able to produce favorable effects on skeletal muscle (SM) remodeling in a well-established rat model of right heart failure (RHF).

Methods

RHF was induced by monocrotaline (MCT) in Sprague–Dawley rats. Three weeks later, four millions of hAFS or rSVC-GFP cells were injected via tail vein. SM remodeling was assessed by Soleus muscle fiber cross sectional area (CSA), myocyte apoptosis, myosin heavy chain (MHC) composition, satellite cells pattern, and SC immunohistochemistry.

Results

hAFS and rSVC-GFP injection produced significant SC homing in Soleus (0.68 ± 1.0 and 0.67 ± 0.75% respectively), with a 50% differentiation toward smooth muscle and endothelial cells. Pro-inflammatory cytokines were down regulated to levels similar to those of controls.SC-treated (SCT) rats showed increased CSA (p < 0.004 vs MCT) similarly to controls with a reshift toward the slow MHC1 isoform. Apoptosis was significantly decreased (11.12. ± 8.8 cells/mm³ hAFS and 13.1 + 7.6 rSVC-GFP) (p < 0.001 vs MCT) and similar to controls (5.38 ± 3.0 cells/mm³).RHF rats showed a dramatic reduction of satellite cells(MCT 0.2 ± 0.06% Pax7 native vs controls 2.60 ± 2.46%, p < 0.001), while SCT induced a repopulation of both native and SC derived satellite cells (p < 0.005).

Conclusions

SC treatment led to SM remodeling with satellite cell repopulation, decreased atrophy and apoptosis. Modulation of the cytokine milieu might play a crucial pathophysiological role with a possible scenario for autologous transplantation of SC in pts with CHF myopathy.     

cGMP/PKG pathway mediates myocardial postconditioning protection in rat hearts by delaying normalization of intracellular acidosis during reperfusion

Ischemic postconditioning has been demonstrated to limit infarct size in patients, but its molecular mechanisms remain incompletely understood. Low intracellular pH (pHi) inhibits mitochondrial permeability transition, calpain activation and hypercontracture. Recently, delayed normalization of pHi during reperfusion has been shown to play an important role in postconditioning protection, but its relation with intracellular protective signaling cascades is unknown. The present study investigates the relation between the rate of pHi normalization and the cGMP/PKG pathway in postconditioned myocardium. In isolated Sprague-Dawley rat hearts submitted to transient ischemia both, postconditioning and acidic reperfusion protocols resulted in a similar delay in pHi recovery measured by ³¹P-NMR spectroscopy (3.6 ± 0.2 min and 3.5 ± 0.2 min respectively vs. 1.4 ± 0.2 min in control group, P < 0.01) and caused equivalent cardioprotection (48% and 41% of infarct reduction respectively, P < 0.01), but only postconditioning increased myocardial cGMP levels (P = 0.02) and activated PKG. Blockade of cGMP/PKG pathway by the addition of the guanylyl cyclase inhibitor ODQ or the PKG inhibitor KT5823 during reperfusion accelerated pHi recovery and abolished cardioprotection in postconditioned hearts, but had no effect in hearts subjected to acidic reperfusion suggesting that PKG signaling was upstream of delayed pHi normalization in postconditioned hearts. In isolated cardiomyocytes the cGMP analog 8-pCPT-cGMP delayed Na⁺/H⁺-exchange mediated pHi normalization after acidification induced by a NH₄Cl pulse. These results demonstrate that the cGMP/PKG pathway contributes to postconditioning protection at least in part by delaying normalization of pHi during reperfusion, probably via PKG-dependent inhibition of Na⁺/H⁺-exchanger.     

缺血后适应对老年冠心病患者缺血再灌注肢体血管内皮功能的影响

目的 观察缺血再灌注不同时刻给予缺血后适应,对老年冠心病患者血管内皮功能的保护作用.方法 选取老年冠心病患者54例,随机分为3组,缺血再灌注组、后适应组及延迟后适应组.建立肢体缺血再灌注模型,在再灌注不同时刻(1 min内及1 min后)分别给予后适应组及延迟后适应组缺血后适应干预,通过超声检测肱动脉血流介导的舒张功能(FMD),观察缺血再灌注前后反应性充血血管内径的变化.结果 缺血再灌注组再灌注后FMD明显减小(P＜0.05),再灌注1 min内给予缺血后适应有明显的血管内皮功能保护作用,与缺血再灌注组比较,后适应组FMD明显提高(6.70±2.36 vs 3.05±0.91,P＜0.05),而延迟后适应组则失去了内皮功能保护作用(3.17±1.04 vs 3.05±0.91,P＞0.05).结论 再灌注1 min内给予缺血后适应可以改善血管内皮功能,但延迟后适应的保护作用消失.     

Remote postconditioning by humoral factors in effluent from ischemic preconditioned rat hearts is mediated via PI3K/Akt-dependent cell-survival signaling at reperfusion

Short non-lethal ischemic episodes administered to hearts prior to (ischemic preconditioning, IPC) or directly after (ischemic postconditioning, IPost) ischemic events facilitate myocardial protection. Transferring coronary effluent collected during IPC treatment to un-preconditioned recipient hearts protects from lethal ischemic insults. We propose that coronary IPC effluent contains hydrophobic cytoprotective mediators acting via PI3K/Akt-dependent pro-survival signaling at ischemic reperfusion. Ex vivo rat hearts were subjected to 30 min of regional ischemia and 120 min of reperfusion. IPC effluent administered for 10 min prior to index ischemia attenuated infarct size by ≥55% versus control hearts (P < 0.05). Effluent administration for 10 min at immediate reperfusion (reperfusion therapy) or as a mimetic of pharmacological postconditioning (remote postconditioning, RIPost) significantly reduced infarct size compared to control (P < 0.05). The IPC effluent significantly increased Akt phosphorylation in un-preconditioned hearts when administered before ischemia or at reperfusion, while pharmacological inhibition of PI3K/Akt-signaling at reperfusion completely abrogated the cardioprotection offered by effluent administration. Fractionation of coronary IPC effluent revealed that cytoprotective humoral mediator(s) released during the conditioning phase were of hydrophobic nature as all hydrophobic fractions with molecules under 30 kDa significantly reduced infarct size versus the control and hydrophilic fraction-treated hearts (P < 0.05). The total hydrophobic effluent fraction significantly reduced infarct size independently of temporal administration (before ischemia, at reperfusion or as remote postconditioning). In conclusion, the IPC effluent retains strong cardioprotective properties, containing hydrophobic mediator(s) < 30 kDa offering cytoprotection via PI3K/Akt-dependent signaling at ischemic reperfusion.     

Randomized comparison of direct stenting with predilatation followed by stenting on vessel trauma and restenosis

Background

Direct stenting may reduce trauma to the vessel wall, thereby having a positive impact on acute and long-term results. This study evaluated acute vessel trauma and acute and follow-up angiographic and intravascular ultrasound (IVUS) results after direct stenting in comparison to conventional stenting.

Methods

Two hundred forty-nine patients were randomly assigned to direct stenting (n = 124) or stenting after predilatation (n = 125) and were followed up by angiography at 6 ± 2 months. Intracoronary serum endothelin (ET-1) levels were determined distal to the lesion before and after coronary intervention to define vessel trauma, and IVUS was performed before and after intervention and at follow-up to determine induced changes in vessel morphology and intimal hyperplasia in a subgroup of 40 patients.

Results

Feasibility of direct stenting was 91%, with 9% requiring crossover to predilatation. There were no differences between the 2 groups in immediate clinical, angiographic, and intravascular ultrasound results. Intracoronary ET-1 levels increased significantly after intervention, without differences between the 2 groups (increase in ET-1 level, 0.79 ± 1.06 vs 0.96 ± 1.22 fmol/L, P = .206). At 6-month follow-up, angiographic late loss (0.76 ± 0.86 vs 0.69 ± 1.09 mm, P = .788) and restenosis rate (21% vs 20%, P = 1.000) were similar for direct stenting versus conventional stenting, respectively. IVUS demonstrated comparable intimal hyperplasia areas for direct versus conventional stenting (2.0 ± 1.5 mm² vs 2.2 ± 1.6 mm², respectively, P = .243).

Conclusions

Direct stenting is highly feasible and results in similar vessel trauma and change in vessel morphology and acute lumen dimensions compared with stenting after predilatation. Similar acute angiographic and IVUS results persist at 6-month follow-up.     

Additional stenting promotes intimal proliferation and compromises the results of intravascular radiation therapy: an intravascular ultrasound study

Background

Vascular brachytherapy (VBT) reduces in-stent restenosis (ISR). However, additional stenting at the time of radiation may be associated with a worse outcome.

Methods and results

Intravascular ultrasound (IVUS) was performed after VBT and at 6 months follow-up in 79 native artery ISR patients treated with γ-radiation who participated in the Washington Radiation for In-Stent restenosis Trial (WRIST), Gamma-1, and Angiorad Radiation Technology for In-Stent restenosis Trial in Coronaries (ARTISTIC) trials. Patients were treated with ¹⁹²Ir at 14 or 15 Gy at 2 mm from the source. Additional stents were used to treat the ISR lesions in 45 patients; these patients were then compared with the 34 patients treated without restenting. Paired measurements included stent, lumen, and intimal hyperplasia volumes. After the VBT procedure, intimal hyperplasia volume was smaller in the group treated with additional stents (54 ± 33 mm³ vs 34 ± 33 mm³, P = .012), but minimal lumen area was similar between the 2 groups (4.3 ± 1.5 mm² vs 4.7 ± 1.4 mm² respectively, P = NS). Between the time of the VBT procedure and follow-up, intimal hyperplasia volume increased by 27 ± 19 mm³ in the restented group and by 9 ± 21 mm³ in the group treated without additional stents (P = .014). At 6 months, intimal volume was similar in the 2 groups, but minimal lumen area was slightly smaller in the group treated with additional stents (3.4 ± 1.8 mm² vs 4.2 ± 1.7 mm², P = .053). Patients treated with additional stents had more target lesion revascularizations than the group treated without additional stents (38% vs 15%, P = .02).

Conclusions

Additional stenting reduces intimal hyperplasia within the stents acutely. However, it compromises the benefit of VBT by promoting higher intimal regrowth within months after radiation.     

缺血后适应对活性氧及心肌细胞凋亡的影响

目的观察后适应和远程后适应对大鼠缺血再灌注模型活性氧生成及心肌细胞凋亡的影响，探讨活性氧在后适应和远程后适应中的作用。方法大鼠随机分为6组：①假手术组：只穿线，不结扎；②模型组：前降支缺血30min后再灌注2h：③后适应组：前降支缺血30min后进行3个循环后适应（缺血10s，再灌注10s，然后再灌注2h;④远程后适应组：前降支缺血24min时结扎右股动脉5min，在再灌注前1min开通股动脉，前降支再灌注2h；⑤2-巯基丙酰基甘氨酸组l；⑥2-巯基丙酰基甘氨酸组2：在缺血20min时尾静脉注射2一巯基丙酰基甘氨酸20mg／kg，余处理分别同组③和（或）④。实验结束后检测血丙二醛，心肌标本行HE染色、TUNEL检测和测定Bcl-2、BaxmRNA。结果①血丙二醛活性：后适应组、远程后适应组、2-巯基丙酰基甘氨酸组1和组2分别为（14．6±1．4）、（15．6±1．5）、（14．4±1．6）、（15．0±1．4）μmol／L，低于模型组（18．3±1．9）μmol／L，（P〈0．05）；②后适应组和远程后适应组Bcl-2表达高于模型组，而Bax表达低于模型组（P〈0．05）；2-巯基丙酰基甘氨酸处理有对抗作用；④细胞凋亡率：后适应组（25．3±2．3）％和远程后适应组（26．7±2．2）％低于模型组（50．0±7．9）％（P〈0．05），2-巯基丙酰基甘氨酸处理有对抗作用。结论后适应和远程后适应均能减少活性氧的产生：后适应和远程后适应都有减少细胞凋亡作用，其心肌保护作用与减少活性氧的产生有关：提示活性氧可能在后适应和远程后适应中发挥重要作用。     

Effect of plaque debulking before stent implantation on in-stent neointimal proliferation: a serial 3-dimensional intravascular ultrasound study

Background

Recent intravascular ultrasound (IVUS) studies have suggested that plaque burden has a role in promoting intimal hyperplasia after stenting. We report on volumetric assessments of in-stent neointimal formation with 3-dimensional IVUS analysis, comparing directional coronary atherectomy (DCA) plus stenting (DCA/stenting) to stenting without DCA.

Methods

Twenty-four patients (24 lesions) treated with DCA before stenting were matched to 24 patients (24 lesions) receiving stenting without DCA. All stents were a single Multilink stent. In both groups, serial IVUS was performed before and after intervention and during the 6-month follow-up period. The arterial segments that were analyzed with a computer-based contour detection program were the same as the stented segments analyzed on serial studies. These measurements were obtained: (1) lumen volume (LV), (2) stent volume (SV), (3) vessel volume (VV), (4) in-stent neointimal volume (ISV) calculated as SV-LV, and (5) percent in-stent neointimal volume (%ISV) calculated as ([SV-LV]/SV) × 100.

Results

Baseline characteristics of the 2 groups were similar. After intervention, both groups achieved similar LV (140.0 mm³ DCA/stenting vs 135.2 mm³ stenting alone). However, the follow-up ISV and %ISV were significantly smaller in the DCA/stenting group (19.6 ± 12.2 mm³ DCA/stenting vs 44.6 ± 29.5 mm³ stenting alone; P = .00040; 15.3% ± 10.6% DCA/stenting vs 31.5% ± 17.7% stenting alone; P = .00040). Consequently, the DCA/stenting group showed a significantly greater follow-up LV (121.0 ± 51.5 mm³ DCA/stenting vs 91.5 ± 26.7 mm³ stenting alone; P = .016).

Conclusions

Plaque removal with DCA before stenting inhibits in-stent neointimal hyperplasia.     

Kinetics of megakaryocyte progenitor cells in idiopathic thrombocytopenic purpura

Summary The number and proliferative state of megakaryocyte progenitor cells (CFU-Meg) were compared between 13 patients with idiopathic thrombocytopenic purpura (ITP) and hematologically normal controls. The mean frequency of CFU-Meg assayed by the plasma clot method was 27.8 ± 12.2 (± SD)/2×10⁵ bone marrow light-density cells for the ITP patients, which did not differ significantly from the control value of 31.9 ± 16.1. The percentage of CFU-Meg in DNA synthesis estimated by the³H-thymidine suicide technique was 41.3% ± 9.2% in ITP, which was significantly greater than the control value of 27.1% ± 7.4% (P < 0.01). The megakaryocyte counts for histological sections prepared from bone marrow aspirates from the ITP patients and controls were 34.5 ± 8.5/mm² and 11.2 ± 5.8/mm², respectively, with the difference being highly significant (P < 0.001). These results suggest that increased cycling activity in a quantitatively unchanged CFU-Meg pool may lead to increased megakaryocytes in the bone marrow of ITP patients.     

Insulin addition after ischemia improves recovery of function equal to ischemic preconditioning in rat heart

Background Ischemic preconditioning (IPC) is considered the most potent mechanism to improve ischemia tolerance. We have demonstrated that insulin addition during reperfusion improves recovery of function in the isolated working rat heart. We herein compare the relative importance of these two mechanisms in improving recovery of postischemic function.Methods Isolated working rat hearts were perfused with Krebs-Henseleit buffer containing glucose (5 mmol/l) plus oleate (0.4 mmol/l) for 20 min and were then subjected to 15 min of ischemia followed by 35 min of reperfusion. IPC was achieved by an ischemic period of ve minutes followed by 10 minutes of reperfusion before ischemia. Insulin (1 mU/ml) was or was not added at the beginning of reperfusion. Wortmannin (WM, 3 µmol/l), an inhibitor of phosphatidylinositol 3-kinase, was or was not present in the perfusate from the beginning of the experiments. We measured glucose uptake with [2-³H]glucose, cardiac power and tissue metabolite content at the end of the experiments.Results Cardiac power before ischemia ranged from 7.17 to 10.4 mW. After ischemia, cardiac power recovered to 65.7 ± 3.8% (Control). Insulin signicantly improved recovery (96.3 ± 10.8%, p < 0.05 vs. Control). This effect was also achieved by IPC (recovery 86.2 ± 6.2%, p < 0.05). The effects of insulin and IPC were not additive (recovery 83.4 ± 6.2%, p < 0.05). WM fully inihibited the effects of both insulin and IPC (69.5 ± 3.3, 72.0 ± 6.9, respectively). Basal glucose uptake ranged from 2.53 to 3.46 µmol/gdry, and was signicantly lower after ischemia in the presence of WM.Conclusions Insulin is a potent tool to improve postischemic contractile function. The improvement of recovery afforded by insulin added after ischemia may be mediated through a similar mechanism as ischemic preconditioning.     

Remote postconditioning

Objectives A series of brief coronary artery reperfusions and reocclusions applied during the early minutes of coronary artery reflow (“postconditioning”) attenuates reperfusion injury. However, it is not known whether brief ischemia–reperfusion applied to a distant organ at the onset of myocardial reperfusion (i.e. “remote postconditioning”, remote PostC) reduces infarct size in the reperfused myocardium. In an in vivo anesthetized rat model of myocardial infarction induced by coronary artery occlusion and reperfusion, this study tested the hypothesis that remote postC induced by a single 5 minute episode of renal artery (RA) occlusion and reperfusion applied immediately before the onset of coronary artery reperfusion protects the myocardium from reperfusion injury by mechanisms involving endogenous adenosine receptor activation. Methods All rats were subjected to a total of 30 minutes of left coronary artery occlusion (LCAO) and 3 hours of reperfusion. The rats were randomized to one of six groups: 1) Control: LCAO and reperfusion only with no other intervention; 2) Remote PostC: after 24 minutes of LCAO the RA was occluded for 5 minutes and released 1 min before coronary artery reperfusion; 3) Permanent RA occlusion: the RA was permanently occluded after 24 minutes LCAO continuing to the end of reperfusion; 4) Delayed Remote PostC: after 26 minutes LCAO the RA was occluded for 5 minutes, and its release was delayed until 1 min after coronary artery reperfusion; 5) CON + SPT: rats with LCAO and reperfusion received 10 mg/kg IV of the non–selective adenosine receptor antagonist 8–sulfophenyl theophylline [SPT] administered 5 minutes before coronary artery reperfusion; and 6) Remote PostC + SPT: after 24 minutes of LCAO the RA was occluded for 5 minutes and released 1 minute before coronary artery reperfusion in the presence of 10 mg/kg SPT given 5 min before coronary artery reperfusion. Results Myocardial infarct size (percentage necrosis/area at risk, mean ± SEM) was reduced by 50% in Remote PostC (25 ± 4%) compared to Control (49 ± 4%, p = 0.003), consistent with a reduction in plasma CK activity (44 ± 5 vs. 67 ± 6 U/ml, p = 0.023). In contrast, permanent RA occlusion before LCAO and reperfusion failed to reduce myocardial infarct size (47 ± 5%) vs Control. Delaying the release of the RA occlusion (delayed Remote PostC) abrogated the myocardial infarct reduction observed with Remote PostC (48 ± 6%). SPT alone had no effect on infarct size (47 ± 4% in CON + SPT vs. 49 ± 4% in CON); however, Remote PostC+SPT abrogated the myocardial infarct size reduction in Remote PostC (50 ± 3% in Remote PostC + SPT vs. 25 ± 4% in Remote PostC). Conclusions Remote renal postconditioning applied immediately before the onset of coronary artery reperfusion provides potent myocardial infarct size reduction likely exerted during the first minutes of coronary artery reperfusion. This inter–organ remote postconditioning phenomenon is likely mediated in part by release of adenosine by the ischemic–reperfused kidney and subsequent activation of adenosine receptors.     

Preconditioning and postconditioning: the essential role of the mitochondrial permeability transition pore

OBJECTIVE: The opening of the mitochondrial permeability transition pore (mPTP) at the time of myocardial reperfusion is a critical determinant of cell death. Emerging studies suggest that suppression of mPTP opening may underlie the cardioprotection elicited by both ischemic preconditioning (IPC) and postconditioning (IPost). To further evaluate the role of the mPTP in cardioprotection, we hypothesized that hearts deficient in cyclophilin-D (CYP-D-/-), a key component of the mPTP, will be resistant to cardioprotection conferred by ischemic and pharmacological preconditioning and postconditioning. METHODS AND RESULTS: Male/female wild type or CYP-D-/- mice were subjected to 30 min of ischemia and 120 min of reperfusion. In wild type mice subjected to in vivo myocardial ischemia-reperfusion injury, a significant reduction in myocardial infarct size was observed with the following treatments (n>/=6/group; P<0.05): (1) IPC (28+/-4% vs. 46.2+/-4% in control); (2) Diazoxide (5 mg/kg) pre-treatment (26.4+/-3% vs. 54+/-10% in vehicle control); (3) IPost-1 or IPost-2, three or six 10-s cycles of ischemia-reperfusion (27.2+/-3% and 32+/-4%, respectively vs. 46.2+/-4% in control); (4) Bradykinin (40 mug/kg) (28.3+/-1% vs. 48+/-4% in vehicle control); (5) cyclosporin-A (10 mg/kg) (32.3+/-3% vs. 48+/-4% in vehicle control) (6) sanglifehrin-A (25 mg/kg) (29.3+/-3% vs. 48+/-4% in vehicle control). Interestingly, however, no infarct-limiting effects were demonstrated in CYP-D-/- mice with the same treatment protocols: (27.9+/-5% in control vs. 31.2+/-7% with IPC, 30.2+/-5% with IPost-1, 24.7+/-8% with IPost-2; 30.1+/-4% in vehicle control vs. 26.4+/-7% with diazoxide; 24.6+/-4% in vehicle control vs. 24.9+/-5% with bradykinin, 26.8+/-7% with cyclosporin-A, 32.5+/-6% with sanglifehrin-A: n>/=6/group: P>0.05). CONCLUSION: This study demonstrates that the mPTP plays a critical role in the cardioprotection elicited by ischemic and pharmacological preconditioning and postconditioning.     

Effect of ischemic postconditioning on microvascular obstruction in reperfused myocardial infarction. Results of a randomized study in patients and of an experimental model in swine

Background

Ischemic postconditioning (PCON) appears as a potentially beneficial tool in ST-segment elevation myocardial infarction (STEMI). We evaluated the effect of PCON on microvascular obstruction (MVO) in STEMI patients and in an experimental swine model.

Methods

A prospective randomized study in patients and an experimental study in swine were carried out in two university hospitals in Spain. 101 consecutive STEMI patients were randomized to undergo primary angioplasty followed by PCON or primary angioplasty alone (non-PCON). Using late gadolinium enhancement cardiovascular magnetic resonance, infarct size and MVO were quantified (% of left ventricular mass). In swine, using an angioplasty balloon-induced anterior STEMI model, MVO was defined as the % of area at risk without thioflavin-S staining.

Results

In patients, PCON (n = 49) in comparison with non-PCON (n = 52) did not significantly reduce MVO (0 [0–1.02]% vs. 0 [0–2.1]% p = 0.2) or IS (18 ± 13% vs. 21 ± 14%, p = 0.2). MVO (> 1 segment in the 17-segment model) occurred in 12/49 (25%) PCON and in 18/52 (35%) non-PCON patients, p = 0.3. No significant differences were observed between PCON and non-PCON patients in left ventricular volumes, ejection fraction or the extent of hemorrhage. In the swine model, MVO occurred in 4/6 (67%) PCON and in 4/6 (67%) non-PCON pigs, p = 0.9. The extent of MVO (10 ± 7% vs. 10 ± 8%, p = 0.9) and infarct size (23 ± 14% vs. 24 ± 10%, p = 0.8) was not reduced in PCON compared with non-PCON pigs.

Conclusions

Ischemic postconditioning does not significantly reduce microvascular obstruction in ST-segment elevation myocardial infarction.Clinical Trial Registrationhttp://www.clinicaltrials.gov. Unique identifier: NCT01898546.