Michel Ovize

Effect of Cyclosporine on Reperfusion Injury in Acute Myocardial Infarction

BACKGROUND Experimental evidence suggests that cyclosporine, which inhibits the opening of mitochondrial permeability-transition pores, attenuates lethal myocardial injury that occurs at the time of reperfusion. In this pilot trial, we sought to determine whether the administration of cyclosporine at the time of percutaneous coronary intervention (PCI) would limit the size of the infarct during acute myocardial infarction. METHODS We randomly assigned 58 patients who presented with acute ST-elevation myocardial infarction to receive either an intravenous bolus of 2.5 mg of cyclosporine per kilogram of body weight (cyclosporine group) or normal saline (control group) immediately before undergoing PCI. Infarct size was assessed in all patients by measuring the release of creatine kinase and troponin I and in a subgroup of 27 patients by performing magnetic resonance imaging (MRI) on day 5 after infarction. RESULTS The cyclosporine and control groups were similar with respect to ischemia time, the size of the area at risk, and the ejection fraction before PCI. The release of creatine kinase was significantly reduced in the cyclosporine group as compared with the control group (P=0.04). The release of troponin I was not significantly reduced (P=0.15). On day 5, the absolute mass of the area of hyperenhancement (i.e., infarcted tissue) on MRI was significantly reduced in the cyclosporine group as compared with the control group, with a median of 37 g (interquartile range, 21 to 51) versus 46 g (interquartile range, 20 to 65; P=0.04). No adverse effects of cyclosporine administration were detected. CONCLUSIONS In our small, pilot trial, administration of cyclosporine at the time of reperfusion was associated with a smaller infarct by some measures than that seen with placebo. These data are preliminary and require confirmation in a larger clinical trial.

Regional ischemic 'preconditioning' protects remote virgin myocardium from subsequent sustained coronary occlusion.

BackgroundOne or more brief episodes of coronary artery occlusion protect or “precondition” the myocardium perfused by that artery from a subsequent episode of sustained ischemia. We sought to determine whether ischemic preconditioning protects only those myocytes subjected to brief coronary occlusion or whether brief occlusions in one vascular bed also limit infarct size andfor attenuate contractile dysfunction in remote virgin myocardium subjected to subsequent sustained coronary occlusion. Methods and ResultsIn the preliminary limb of the study, six anesthetized dogs underwent four episodes of 5-minute circumflex branch occlusion plus 5-minute reperfusion, followed by 1 hour of sustained left anterior descending coronary artery occlusion and 4.5 hours of reflow. Subendocardial blood flow during left anterior descending coronary artery occlusion (measured by injection of radiolabeled microspheres) was 0.07±0.03 mL. min-1. g tissue-1, similar to the value of 0.07±0.02 mL. min-1. g-1 observed in a group of eight concurrent control dogs. However, infarct size (assessed by triphenyltetrazolium staining) in the circumflex preconditioned group averaged 4±1% of the myocardium at risk, significantly less (p<0.05) than the value of 13+4% observed in the concurrent controls. An additional 18 dogs were then randomized to undergo either four episodes of circumflex branch occlusion (n=8) or no intervention (n=10) before 1 hour of left anterior descending coronary artery occlusion and 4.5 hours of reflow. Subendocardial blood flow averaged 0.08±0.02 versus 0.08±0.03 mL. min-1. g-1 in the control versus circumflex preconditioned groups, yet infarct size was significantly smaller in circumflex preconditioned dogs than in the controls (6±2% versus 16±5% of the risk region; p<0.05). At 4.5 hours following reperfusion, segment shortening in the left anterior descending coronary artery bed (assessed by sonomicrometry) averaged -21+19%o of baseline in control animals versus 13±12% of baseline in the preconditioned group (p=NS). Circumflex preconditioning did not, however, have an independent beneficial effect on contractile function: Regression analysis revealed that the trend toward improved function in circumflex preconditioned dogs reflected the smaller infarct sizes in this group. ConclusionsBrief episodes of ischemia in one vascular bed protect remote, virgin myocardium from subsequent sustained coronary artery occlusion in this canine model. These data imply that preconditioning may be mediated by factor(s) activated, produced, or transported throughout the heart during brief ischemia/reperfusion.

Postconditioning the Human Heart

Background— In animal models, brief periods of ischemia performed just at the time of reperfusion can reduce infarct size, a phenomenon called postconditioning. In this prospective, randomized, controlled, multicenter study, we investigated whether postconditioning may protect the human heart during coronary angioplasty for acute myocardial infarction. Methods and Results— Thirty patients, submitted to coronary angioplasty for ongoing acute myocardial infarction, contributed to the study. Patients were randomly assigned to either a control or a postconditioning group. After reperfusion by direct stenting, control subjects underwent no further intervention, whereas postconditioning was performed within 1 minute of reflow by 4 episodes of 1-minute inflation and 1-minute deflation of the angioplasty balloon. Infarct size was assessed by measuring total creatine kinase release over 72 hours. Area at risk and collateral blood flow were estimated on left ventricular and coronary angiograms. No adverse events occurred in the postconditioning group. Determinants of infarct size, including ischemia time, size of the area at risk, and collateral flow, were comparable between the 2 groups. Area under the curve of creatine kinase release was significantly reduced in the postconditioning compared with the control group, averaging 208 984±26 576 compared with 326 095±48 779 (arbitrary units) in control subjects, ie, a 36% reduction in infarct size. Blush grade, a marker of myocardial reperfusion, was significantly increased in postconditioned compared with control subjects: 2.44±0.17 versus 1.95±0.27, respectively (P<0.05). Conclusions— This study suggests that postconditioning by coronary angioplasty protects the human heart during acute myocardial infarction.

Postconditioning Inhibits Mitochondrial Permeability Transition

Background—Brief periods of ischemia performed just at the time of reperfusion can reduce infarct size, a phenomenon called “postconditioning.” After reflow, opening of the mitochondrial permeability transition pore (mPTP) has been involved in lethal reperfusion injury. We hypothesized that postconditioning may modulate mPTP opening. Methods and Results—Anesthetized open-chest rabbits underwent 30 minutes of ischemia and 4 hours of reperfusion. Control hearts underwent no additional intervention. Postconditioning consisted of 4 episodes of 1 minute of coronary occlusion and 1 minute of reperfusion performed after 1 minute of reflow after the prolonged ischemia. Preconditioning consisted of 5 minutes of ischemia and 5 minutes of reperfusion before the 30-minute ischemia. An additional group of rabbits received 5 mg/kg IV of NIM811, a specific inhibitor of the mPTP, 1 minute before reperfusion. Infarct size was assessed by triphenyltetrazolium staining. Mitochondria were isolated from the risk region myocardium, and Ca2+-induced mPTP opening was assessed by use of a potentiometric method. Postconditioning, preconditioning, and NIM811 significantly limited infarct size, which averaged 29±4%, 18±4%, and 20±4% of the risk region, respectively, versus 61±6% in controls (P≤0.001 versus control). The Ca2+ load required to open the mPTP averaged 41±4, 47±5, and 67±9 μmol/L CaCl2 per mg of mitochondrial proteins in postconditioning, preconditioning, and NIM811, respectively, significantly higher than the value of 16±4 μmol/L per mg in controls (P≤0.05). Conclusions—Postconditioning inhibits opening of the mPTP and provides a powerful antiischemic protection.

Postconditioning and protection from reperfusion injury: where do we stand?Position Paper from the Working Group of Cellular Biology of the Heart of the European Society of Cardiology

Ischaemic postconditioning (brief periods of ischaemia alternating with brief periods of reflow applied at the onset of reperfusion following sustained ischaemia) effectively reduces myocardial infarct size in all species tested so far, including humans. Ischaemic postconditioning is a simple and safe manoeuvre, but because reperfusion injury is initiated within minutes of reflow, postconditioning must be applied at the onset of reperfusion. The mechanisms of protection by postconditioning include: formation and release of several autacoids and cytokines; maintained acidosis during early reperfusion; activation of protein kinases; preservation of mitochondrial function, most strikingly the attenuation of opening of the mitochondrial permeability transition pore (MPTP). Exogenous recruitment of some of the identified signalling steps can induce cardioprotection when applied at the time of reperfusion in animal experiments, but more recently cardioprotection was also observed in a proof-of-concept clinical trial. Indeed, studies in patients with an acute myocardial infarction showed a reduction of infarct size and improved left ventricular function when they underwent ischaemic postconditioning or pharmacological inhibition of MPTP opening during interventional reperfusion. Further animal studies and large-scale human studies are needed to determine whether patients with different co-morbidities and co-medications respond equally to protection by postconditioning. Also, our understanding of the underlying mechanisms must be improved to develop new therapeutic strategies to be applied at reperfusion with the ultimate aim of limiting the burden of ischaemic heart disease and potentially providing protection for other organs at risk of reperfusion injury, such as brain and kidney.

Long-Term Benefit of Postconditioning

Background— We previously demonstrated that ischemic postconditioning decreases creatine kinase release, a surrogate marker for infarct size, in patients with acute myocardial infarction. Our objective was to determine whether ischemic postconditioning could afford (1) a persistent infarct size limitation and (2) an improved recovery of myocardial contractile function several months after infarction. Methods and Results— Patients presenting within 6 hours of the onset of chest pain, with suspicion for a first ST-segment–elevation myocardial infarction, and for whom the clinical decision was made to treat with percutaneous coronary intervention, were eligible for enrollment. After reperfusion by direct stenting, 38 patients were randomly assigned to a control (no intervention; n=21) or postconditioned group (repeated inflation and deflation of the angioplasty balloon; n=17). Infarct size was assessed both by cardiac enzyme release during early reperfusion and by 201thallium single photon emission computed tomography at 6 months after acute myocardial infarction. At 1 year, global and regional contractile function was evaluated by echocardiography. At 6 months after acute myocardial infarction, single photon emission computed tomography rest-redistribution index (a surrogate for infarct size) averaged 11.8±10.3% versus 19.5±13.3% in the postconditioned versus control group (P=0.04), in agreement with the significant reduction in creatine kinase and troponin I release observed in the postconditioned versus control group (−40% and −47%, respectively). At 1 year, the postconditioned group exhibited a 7% increase in left ventricular ejection fraction compared with control (P=0.04). Conclusions— Postconditioning affords persistent infarct size reduction and improves long-term functional recovery in patients with acute myocardial infarction.

Doppler tissue imaging quantitates regional wall motion during myocardial ischemia and reperfusion.

BACKGROUND Quantification of regional myocardial function is a major unresolved issue in cardiology. We evaluated the accuracy of pulsed Doppler tissue imaging (DTI), a new echocardiographic technique, to quantify regional myocardial dysfunction induced by acute ischemia and reperfusion. METHODS AND RESULTS In nine open-chest anesthetized pigs, various degrees of regional wall motion abnormalities were induced by graded reduction of left anterior descending coronary artery (LAD) blood flow. Pulsed Doppler tissue imaging was performed from an epicardial apical four-chamber view with the sample placed within the middle part of the septal wall. Peak septal velocities were calculated during systole, isovolumic relaxation, and early and late diastole. Regional myocardial blood flow and systolic and diastolic dysfunctions were assessed by radioactive microspheres and ultrasonic crystals, respectively. Ischemia resulted in a significant rapid reduction of systolic velocities and an early decrease in the ratio of early to late diastolic velocities. Both changes were detected by pulsed DTI within 5 seconds of coronary artery occlusion. The decrease in systolic velocity significantly correlated with both systolic shortening (r=.90, P<.0001) and regional myocardial blood flow (r=.96, P<.0001) during reduction of LAD blood flow. CONCLUSIONS These results suggest that DTI may be a promising new tool for the quantification of ischemia-induced regional myocardial dysfunction.

Inhibition of GSK3β by Postconditioning Is Required to Prevent Opening of the Mitochondrial Permeability Transition Pore During Reperfusion

Background— Opening of the mitochondrial permeability transition pore (mPTP) is a crucial event in lethal reperfusion injury. Phosphorylation (inhibition) of glycogen synthase kinase-3β (GSK3β) has been involved in cardioprotection. We investigated whether phosphorylated GSK3β may protect the heart via the inhibition of mPTP opening during postconditioning. Methods and Results— Wild-type and transgenic GSK3β-S9A mice (the cardiac GSK3β activity of which cannot be inactivated) underwent 60 minutes of ischemia and 24 hours of reperfusion. At reperfusion, wild-type and GSK3β-S9A mice received no intervention (control), postconditioning (3 cycles of 1 minute ischemia and 1 minute of reperfusion), the mPTP inhibitor cyclosporine A (CsA; 10 mg/kg IV), or the GSK3β inhibitor SB216763 (SB21; 70 μg/kg IV). Infarct size was assessed by triphenyltetrazolium chloride staining. The resistance of the mPTP to opening after Ca2+ loading was assessed by spectrofluorometry on mitochondria isolated from the area at risk. In wild-type mice, infarct size was significantly reduced by postconditioning, CsA, and SB21, averaging 39±2%, 35±5%, and 37±4%, respectively, versus 58±5% of the area at risk in control mice (P<0.05). In GSK3β-S9A mice, only CsA, but not postconditioning or SB21, reduced infarct size. Postconditioning, CsA, and SB21 all improved the resistance of the mPTP in wild-type mice, but only CsA did so in GSK3β-S9A mice. Conclusion— These results suggest that S9-phosphorylation of GSK3β is required for postconditioning and likely acts by inhibiting the opening of the mitochondrial permeability transition pore.

Translating novel strategies for cardioprotection: the Hatter Workshop Recommendations

Ischemic heart disease (IHD) is the leading cause of death worldwide. Novel cardioprotective strategies are therefore required to improve clinical outcomes in patients with IHD. Although a large number of novel cardioprotective strategies have been discovered in the research laboratory, their translation to the clinical setting has been largely disappointing. The reason for this failure can be attributed to a number of factors including the inadequacy of the animal ischemia–reperfusion injury models used in the preclinical cardioprotection studies and the inappropriate design and execution of the clinical cardioprotection studies. This important issue was the main topic of discussion of the UCL-Hatter Cardiovascular Institute 6th International Cardioprotection Workshop, the outcome of which has been published in this article as the “Hatter Workshop Recommendations”. These have been proposed to provide guidance on the design and execution of both preclinical and clinical cardioprotection studies in order to facilitate the translation of future novel cardioprotective strategies for patient benefit.

Cyclosporine before PCI in Patients with Acute Myocardial Infarction

BACKGROUND Experimental and clinical evidence suggests that cyclosporine may attenuate reperfusion injury and reduce myocardial infarct size. We aimed to test whether cyclosporine would improve clinical outcomes and prevent adverse left ventricular remodeling. METHODS In a multicenter, double-blind, randomized trial, we assigned 970 patients with an acute anterior ST-segment elevation myocardial infarction (STEMI) who were undergoing percutaneous coronary intervention (PCI) within 12 hours after symptom onset and who had complete occlusion of the culprit coronary artery to receive a bolus injection of cyclosporine (administered intravenously at a dose of 2.5 mg per kilogram of body weight) or matching placebo before coronary recanalization. The primary outcome was a composite of death from any cause, worsening of heart failure during the initial hospitalization, rehospitalization for heart failure, or adverse left ventricular remodeling at 1 year. Adverse left ventricular remodeling was defined as an increase of 15% or more in the left ventricular end-diastolic volume. RESULTS A total of 395 patients in the cyclosporine group and 396 in the placebo group received the assigned study drug and had data that could be evaluated for the primary outcome at 1 year. The rate of the primary outcome was 59.0% in the cyclosporine group and 58.1% in the control group (odds ratio, 1.04; 95% confidence interval [CI], 0.78 to 1.39; P=0.77). Cyclosporine did not reduce the incidence of the separate clinical components of the primary outcome or other events, including recurrent infarction, unstable angina, and stroke. No significant difference in the safety profile was observed between the two treatment groups. CONCLUSIONS In patients with anterior STEMI who had been referred for primary PCI, intravenous cyclosporine did not result in better clinical outcomes than those with placebo and did not prevent adverse left ventricular remodeling at 1 year. (Funded by the French Ministry of Health and NeuroVive Pharmaceutical; CIRCUS ClinicalTrials.gov number, NCT01502774; EudraCT number, 2009-013713-99.).