Long-term impact of postconditioning on infarct size and left ventricular ejection fraction in patients with ST-elevation myocardial infarction

Reperfusion Injury: How Can We Reduce It by Pre-, Per-, and Postconditioning

While early coronary reperfusion via primary percutaneous coronary intervention (pPCI) is established as the most efficacious therapy for minimizing infarct size (IS) in acute ST-elevation myocardial infarction (STEMI), the restoration of blood flow also introduces myocardial ischemia-reperfusion injury (IRI), leading to cardiomyocyte death. Among diverse methods, ischemic conditioning (IC), achieved through repetitive cycles of ischemia and reperfusion, has emerged as the most promising method to mitigate IRI. IC can be performed by applying the protective stimulus directly to the affected myocardium or indirectly to non-affected tissue, which is known as remote ischemic conditioning (RIC). In clinical practice, RIC is often applied by serial inflations and deflations of a blood pressure cuff on a limb. Despite encouraging preclinical studies, as well as clinical studies demonstrating reductions in enzymatic IS and myocardial injury on imaging, the observed impact on clinical outcome has been disappointing so far. Nevertheless, previous studies indicate a potential benefit of IC in high-risk STEMI patients. Additional research is needed to evaluate the impact of IC in such high-risk cohorts. The objective of this review is to summarize the pathophysiological background and preclinical and clinical data of IRI reduction by IC.

Effects of late, repetitive remote ischaemic conditioning on myocardial strain in patients with acute myocardial infarction

Late, repetitive or chronic remote ischaemic conditioning (CRIC) is a potential cardioprotective strategy against adverse remodelling following ST-segment elevation myocardial infarction (STEMI). In the randomised Daily Remote Ischaemic Conditioning Following Acute Myocardial Infarction (DREAM) trial, CRIC following primary percutaneous coronary intervention (P-PCI) did not improve global left ventricular (LV) systolic function. A post-hoc analysis was performed to determine whether CRIC improved regional strain. All 73 patients completing the original trial were studied (38 receiving 4 weeks' daily CRIC, 35 controls receiving sham conditioning). Patients underwent cardiovascular magnetic resonance at baseline (5-7 days post-STEMI) and after 4 months, with assessment of LV systolic function, infarct size and strain (longitudinal/circumferential, in infarct-related and remote territories). At both timepoints, there were no significant between-group differences in global indices (LV ejection fraction, infarct size, longitudinal/circumferential strain). However, regional analysis revealed a significant improvement in longitudinal strain in the infarcted segments of the CRIC group (from - 16.2 ± 5.2 at baseline to - 18.7 ± 6.3 at follow up, p = 0.0006) but not in corresponding segments of the control group (from - 15.5 ± 4.0 to - 15.2 ± 4.7, p = 0.81; for change: - 2.5 ± 3.6 versus + 0.3 ± 5.6, respectively, p = 0.027). In remote territories, there was a lower increment in subendocardial circumferential strain in the CRIC group than in controls (- 1.2 ± 4.4 versus - 2.5 ± 4.0, p = 0.038). In summary, CRIC following P-PCI for STEMI is associated with improved longitudinal strain in infarct-related segments, and an attenuated increase in circumferential strain in remote segments. Further work is needed to establish whether these changes may translate into a reduced incidence of adverse remodelling and clinical events. Clinical Trial Registration: http://clinicaltrials.gov/show/NCT01664611 .

NHLBI-Sponsored Randomized Trial of Postconditioning During Primary Percutaneous Coronary Intervention for ST-Elevation Myocardial Infarction

RATIONALE

Postconditioning at the time of primary percutaneous coronary intervention (PCI) for ST-segment-elevation myocardial infarction may reduce infarct size and improve myocardial salvage. However, clinical trials have shown inconsistent benefit.

OBJECTIVE

We performed the first National Heart, Lung, and Blood Institute-sponsored trial of postconditioning in the United States using strict enrollment criteria to optimize the early benefits of postconditioning and assess its long-term effects on left ventricular (LV) function.

METHODS AND RESULTS

We randomized 122 ST-segment-elevation myocardial infarction patients to postconditioning (4, 30 seconds PTCA [percutaneous transluminal coronary angioplasty] inflations/deflations)+PCI (n=65) versus routine PCI (n=57). All subjects had an occluded major epicardial artery (thrombolysis in myocardial infarction=0) with ischemic times between 1 and 6 hours with no evidence of preinfarction angina or collateral blood flow. Cardiac magnetic resonance imaging measured at 2 days post-PCI showed no difference between the postconditioning group and control in regards to infarct size (22.5±14.5 versus 24.0±18.5 g), myocardial salvage index (30.3±15.6% versus 31.5±23.6%), or mean LV ejection fraction. Magnetic resonance imaging at 12 months showed a significant recovery of LV ejection fraction in both groups (61.0±11.4% and 61.4±9.1%; P<0.01). Subjects randomized to postconditioning experienced more favorable remodeling over 1 year (LV end-diastolic volume =157±34 to 150±38 mL) compared with the control group (157±40 to 165±45 mL; P<0.03) and reduced microvascular obstruction ( P=0.05) on baseline magnetic resonance imaging and significantly less adverse LV remodeling compared with control subjects with microvascular obstruction ( P<0.05). No significant adverse events were associated with the postconditioning protocol and all patients but one (hemorrhagic stroke) survived through 1 year of follow-up.

CONCLUSIONS

We found no early benefit of postconditioning on infarct size, myocardial salvage index, and LV function compared with routine PCI. However, postconditioning was associated with improved LV remodeling at 1 year of follow-up, especially in subjects with microvascular obstruction.

CLINICAL TRIAL REGISTRATION

URL: http://www.clinicaltrials.gov . Unique identifier: NCT01324453.

Microvascular Obstruction in ST-Segment Elevation Myocardial Infarction: Looking Back to Move Forward. Focus on CMR

After a myocardial infarction (MI), despite the resolution of the coronary occlusion, the deterioration of myocardial perfusion persists in a considerable number of patients. This phenomenon is known as microvascular obstruction (MVO). Initially, the focus was placed on re-establishing blood flow in the epicardial artery. Then, the observation that MVO has profound negative structural and prognostic repercussions revived interest in microcirculation. In the near future, the availability of co-adjuvant therapies (beyond timely coronary reperfusion) aimed at preventing, minimizing, and repairing MVOs and finding convincing answers to questions regarding what, when, how, and where to administer these therapies will be of utmost importance. The objective of this work is to review the state-of-the-art concepts on pathophysiology, diagnostic methods, and structural and clinical implications of MVOs in patients with ST-segment elevation MIs. Based on this knowledge we discuss previously-tested and future opportunities for the prevention and repair of MVO.

Clinical translation of myocardial conditioning

Rapid admission and acute interventional treatment combined with modern antithrombotic pharmacologic therapy have improved outcomes in patients with ST elevation myocardial infarction. The next major target to further advance outcomes needs to address ischemia-reperfusion injury, which may contribute significantly to the final infarct size and hence mortality and postinfarction heart failure. Mechanical conditioning strategies including local and remote ischemic pre-, per-, and postconditioning have demonstrated consistent cardioprotective capacities in experimental models of acute ischemia-reperfusion injury. Their translation to the clinical scenario has been challenging. At present, the most promising mechanical protection strategy of the heart seems to be remote ischemic conditioning, which increases myocardial salvage beyond acute reperfusion therapy. An additional aspect that has gained recent focus is the potential of extended conditioning strategies to improve physical rehabilitation not only after an acute ischemia-reperfusion event such as acute myocardial infarction and cardiac surgery but also in patients with heart failure. Experimental and preliminary clinical evidence suggests that remote ischemic conditioning may modify cardiac remodeling and additionally enhance skeletal muscle strength therapy to prevent muscle waste, known as an inherent component of a postoperative period and in heart failure. Blood flow restriction exercise and enhanced external counterpulsation may represent cardioprotective corollaries. Combined with exercise, remote ischemic conditioning or, alternatively, blood flow restriction exercise may be of aid in optimizing physical rehabilitation in populations that are not able to perform exercise practice at intensity levels required to promote optimal outcomes.

Meta-analysis of the effects of ischemic postconditioning on structural pathology in ST-segment elevation acute myocardial infarction

In this meta-analysis, we assessed cardiac magnetic resonance imaging data to determine the effects of local and remote ischemic postconditioning (LPoC and RPoC, respectively) on structural pathology in ST-segmentel elevation acute myocardial infarction (STEMI). We searched the Pubmed, Embase and Cochrane Library databases up to May 2017 and included 12 randomized controlled trials (10 LPoC and 2 RPoC)containing 1069 study subjects with thrombolysis in myocardial infarction flow grade 0~1. Weighed mean difference (WMD), standardized mean difference (SMD), and odds ratio (OR) were used for the pooled analysis. Random-effect model was used for the potential clinical inconsistency. LPoC and RPoC increased the myocardial salvage index (n = 5; weighted mean difference (WMD) = 5.52; P = 0.005; I2 = 76.0%), and decreased myocardial edema (n = 7; WMD = -3.35; P = 0.0009; I2 = 18.0%). However, LPoC and RPoC did not reduce the final infarct size (n = 10; WMD = -1.01; P > 0.05; I2 = 68.0%), left ventricular volume (n = 10; standardized mean difference = 0.23; P > 0.05; I2 = 93.0%), the incidence of microvascular obstruction (n = 6; OR = 0.99; P > 0.05; I2 = 0.0%) or the extent of microvascular obstruction (n = 3; WMD = -0.09; P > 0.05; I2 = 6.0%). This meta-analysis shows that LPoC and/or RPoC improves myocardial salvage and decreases myocardial edema in STEMI patients without affecting final infarct size, left ventricular volume or microvascular obstruction.

A Randomized Controlled Trial of Intra-Aortic Adenosine Infusion Before Release of the Aortic Cross-Clamp During Coronary Artery Bypass Surgery

OBJECTIVES

To assess the feasibility, safety, and potential useful effect of adenosine as a postconditioning agent in patients undergoing coronary artery bypass grafting surgeries.

DESIGN

Prospective randomized controlled study.

SETTING

University hospital.

PARTICIPANTS

The study comprised 60 patients scheduled for coronary artery bypass grafting surgery.

INTERVENTIONS

Adenosine (postconditioning group) or placebo (control group). Adenosine infusion (150 µg/kg/min) for 10 minutes via a cardioplegia needle into the aortic root was started 10 minutes before aortic cross-clamp removal.

MEASUREMENTS AND MAIN RESULTS

Compared with the control group, ejection fraction, fractional shortening, cardiac index (2.9 ± 0.3 v 2.2 ± 0.3 L/min/m², p = 0.032 at 60 min postbypass) and diastolic function indices were significantly better in the postconditioning group at most time points in the postbypass period. Cardiac troponin I and creatine kinase-MB release and the inotropic score were significantly lower in the postconditioning group at most time points in the postoperative period. The need for intra-aortic balloon and epicardial pacing were comparable in both groups, whereas incidence of arrhythmia, duration of postoperative mechanical ventilation, and intensive care unit and total hospital stays were significantly lower in the postconditioning group.

CONCLUSIONS

Adenosine postconditioning provided cardiac protection as evidenced by a favorable outcome on systolic and diastolic function indices, less cardiac troponin I and creatine kinase-MB release, lower incidence of arrhythmia, lower inotropic score, and shorter duration of postoperative mechanical ventilation and intensive care unit stay.

A systematic review and meta-analysis evaluating ischemic conditioning during percutaneous coronary intervention

AIM

A systematic review and meta-analysis, evaluating ischemic conditioning during percutaneous coronary intervention (PCI).

METHODS & RESULTS

A database search of randomized trials of ischemic conditioning in PCI created three subgroups for meta-analysis: mortality in elective PCI with remote ischemic preconditioning (RIPreC; subgroup 1a, n = 3) - no outcome difference between RIPreC and control (odds ratio: 0.34; 95% CI: 0.08-1.56), myocardial salvage index in ST-elevation myocardial infarction (STEMI) with RIPreC (subgroup 1b, n = 2) - favored RIPreC (mean difference: 0.13; 95% CI: 0.07-0.19), and infarct size in STEMI with local ischemic postconditioning (LIPostC) (subgroup 4b, n = 12) - favored LIPostC (mean difference: -4.13 g.m^-2; 95% CI: -7.36 to -0.90 g.m^-2).

CONCLUSION

RIPreC and LIPostC improve myocardial salvage index and myocardial infarct size respectively in PCI for STEMI. No mortality benefit detected with RIPreC in elective PCI.

Ischemic postconditioning during primary percutaneous coronary intervention

BACKGROUND

Although some studies have shown potential benefit for ischemic postconditioning (IPoC) during primary percutaneous coronary intervention (PCI) in improving surrogate markers of reperfusion and infarction size, the benefit of this approach on clinical outcomes remains unknown.

METHODS AND RESULTS

Electronic databases were searched for randomized clinical trials that compared IPoC versus conventional treatment during primary PCI. Random effects DerSimonian-Laird risk ratios (RR) were calculated for different clinical and surrogate outcomes. The main outcome of this analysis was all-cause mortality. A total of 25 trials involving 3,619 patients were included in the analysis. At a mean follow up of 14 months (95% confidence interval (CI) 8.6-19.4 months), the incidence of all-cause mortality was 4.9% [95% CI 3.8-6.0%] in the IPoC group versus 3.8% [95% CI 1.9-5.7%] in the control group (RR 0.92, 95% CI 0.68-1.24, P = 0.74). The risk of reinfarction (2.7% [95% CI 1.1-4.3%] vs. 2.3% [0.6-4.0%]; RR 1.29, 95% CI 0.62-2.68, P = 0.72), heart failure (3.6% [95% CI 2.0-5.1%] vs. 5.7% [95% CI 3.3-8.2%]; RR 0.77, 95% CI 0.58-1.06, P = 0.24), target vessel revascularization (3.2% [95% CI 1.7-4.7%] vs. 2.4% [95% CI 1.4-3.3%]; RR 1.40, 95% CI 0.90-2.20, P = 0.20), and stent thrombosis (2.4% [95% CI 1.1-3.8%] vs. 1.8% [95% CI 0.5-3.2%]); RR 1.50, 95% CI 0.60-3.70, P = 0.40) was similar in both groups.

CONCLUSIONS

IPoC does not appear to reduce the risk of clinical adverse events in patients with ST-elevation myocardial infarction undergoing primary PCI. © 2017 Wiley Periodicals, Inc.

Long-term outcome following remote ischemic postconditioning during percutaneous coronary interventions-the RIP-PCI trial long-term follow-up

The clinical value of ischemic conditioning during percutaneous coronary intervention (PCI) and mode of administration is controversial. Our aim was to assess the long-term effect of remote ischemic postconditioning among patients undergoing PCI. We randomized 360 patients undergoing PCI who presented with a negative troponin T at baseline into 3 groups: 2 groups received remote ischemic postconditioning (with ischemia applied to the arm in 1 group and to the thigh in the other group), and the third group acted as a control group. Remote ischemic postconditioning was applied during PCI immediately following stent deployment, by 3, 5-minute cycles of blood pressure cuff inflation to >200 mm Hg on the arm or thigh (20 mm Hg to the arm in the control), with 5-minute breaks between each cycle. There were no differences in baseline characteristics among the 3 groups. Periprocedural myocardial injury occurred in 33% (P = 0.64). After 1 year, there was no difference between groups in death (P = 0.91), myocardial infarction (P = 0.78), or repeat revascularization (P = 0.86). During 3 years of follow-up, there was no difference in death, myocardial infarction, and revascularization among the groups (P = 0.45). Remote ischemic postconditioning during PCI did not affect long-term cardiovascular outcome. A similar effect was obtained when remote ischemia was induced to the upper or lower limb. ClinicalTrials.gov Identifier: NCT00970827.

Short-and long-term effects of ischemic postconditioning in STEMI patients: a meta-analysis

Background

Compelling evidence from large randomized trials demonstrates the salutary effects of ischemic postconditioning on cardioprotection against ischemic/reperfusion injury. However, some studies appear negative findings.

This study was designed to assess the short-and long-term effects of postconditioning (Poc) in studies including evolving ST-elevation myocardial infarction (STEMI).

Methods

Relevant studies were identified through an electronic literature search from the PubMed, Library of Congress, Embase, Cochrane Central Register of Controlled Trials, and ISI Web of Science. Studies published up to December 2014 were eligible for inclusion. Patients older than 18 years presenting within 12 h of the first STEMI and eligible for angioplasty were considered for the study.

Results

The 25 trials allocated 1136 patients to perform locational postconditioning cycles at the onset of reperfusion and 1153 patients to usual percutaneous coronary intervention (PCI). Ischemic postconditioning demonstrated a decrease in serum cardiac enzymes creatine kinase (CK) and CK-MB (P < 0.00001 and P =0.25, respectively) in the subgroup analysis based on direct stenting. Reduction in infarct size by imaging was showed during7 days after myocardial infarction (P =0.01), but not in the longterm (P = 0.08). The wall motion score index was improved in both the short term within 7 days (P = 0.009) and the long term over 6 months after receiving Poc (P = 0.02). All included studies were limited by the high risk of performance and publication bias.

Conclusions

Ischemic postconditioning by brief interruptions of coronary blood flow at the onset of reperfusion after PCI appears to be superior to PCI alone in reducing myocardial injury and improving left ventricular function, especially in patients who have received direct stenting in PCI.

Clinical effect of postconditioning in ST-elevation myocardial infarction patients treated with primary percutaneous coronary intervention: a meta-analysis of randomized controlled trials

OBJECTIVE

To evaluate the clinical effect of postconditioning on patients with ST-elevation myocardial infarction (STEMI) treated with primary percutaneous coronary intervention (PCI).

METHODS

Randomized controlled trials were identified by searching relevant databases published up to April 2nd, 2014. A meta-analysis of eligible studies was performed by Stata 12.0 and Review Manager 5.2 with a fixed-effect model.

RESULTS

Ten studies providing adverse cardiac events in a total of 1346 STEMI patients treated with primary PCI were identified. The occurrence of heart failure was significantly reduced in patients treated with postconditioning compared with usual care (risk ratio (RR) 0.533; 95% confidence intervals (CI) 0.368-0.770), whereas non-fatal reinfarction slightly increased in the postconditioning group (RR 2.746; 95% CI 1.007-7.488). No significant difference in total major adverse cardiac events (MACEs) was observed between the two groups (RR 0.876; 95% CI 0.671-1.144).

CONCLUSIONS

Postconditioning in STEMI patients undergoing primary PCI significantly reduces the risk of heart failure, but fails to decrease the incidence of total MACEs and the risk of non-fatal reinfarction.

Two-dimensional longitudinal strains and torsion analysis to assess the protective effects of ischemic postconditioning on myocardial function: a speckle tracking echocardiography study in rabbits

The reperfusion injury that occurs in the early reperfusion often results in myocardial dysfunction. This study evaluated global and regional left ventricular (LV) function using speckle tracking echocardiography (STE) in a rabbit ischemia-reperfusion (I/R) model with and without ischemic postconditioning (I-PostC). The aim is to investigate the potential benefit of I-PostC for myocardial function and validate whether regional longitudinal strain is an appropriate index to indicate myocardial dysfunction. Forty rabbits were divided into an ischemia-reperfusion group (group I) and an I-PostC group (group II). After the coronary arteries were ligated, LV systolic strain and twist parameters decreased, and absolute value of strain rate of isovolumetric relaxation period (SRivr) and post-systolic strain index (PSI) increased significantly in both groups (all p<0.05). After reperfusion, regional longitudinal systolic strain rate (SRsys), systolic strain (Ssys), LV twist and untwisting rate increased, and SRivr and PSI decreased in group II. These changes were not seen in group I. All STE parameters were correlated with area of necrosis (AN)/area at risk (AR) (all p<0.05). The correlations were morerelevant between SRsys and AN/AR (r=-0.673) and between Ssys and AN/AR (r=-0.777) (both p<0.001). The intra- and inter-observer repeatability of STE parameters were good with correlation coefficients (CCs) >0.8 or 0.6. The sensitivities of GSRsys, GSsys, SRsys, Ssys, and LV twist to detect the myocardial infarction were 81.3%, 62.5%, 87.5%, 93.8% and 81.3%, respectively. And the specificities of those parameters were 75.0%, 81.2%, 75.0%, 87.5% and 68.7%. These results indicate that STE is useful for quantitative detection on myocardial function improvement induced by I-PostC in a rabbit I/R model. The regional index-Ssys is an appropriate parameter to indicate myocardial dysfunction because of its sensitivity, specificity, and repeatability.

Sevoflurane in acute myocardial infarction: a pilot randomized study

BACKGROUND

Experimental evidence suggests that the inhalational anesthetic sevoflurane has a cardioprotective effect. Our objective was to determine if sedation with sevoflurane will reduce infarct size in patients with acute myocardial infarction (MI) who are treated with primary percutaneous coronary intervention (PCI).

METHODS

We randomized 50 patients presenting with a first acute ST-elevation MI treated by primary PCI within 6 hours from symptom onset to sedation with sevoflurane inhalation or standard sedation (control). Coronary flow at the end of PCI was assessed by corrected Thrombolysis In Myocardial Infarction frame count. Myocardial reperfusion was assessed by ST-segment resolution 60 minutes post-PCI. Infarct size was assessed by release of creatinine kinase (CK) and troponin T.

RESULTS

There was no difference in the primary end point: troponin T or CK release adjusted to the area at risk, between groups. However, among patients with anterior MI, there was a trend toward lower CK (P = .05) and nonsignificant decrease in troponin (P = .11) levels in the sevoflurane group. Corrected Thrombolysis In Myocardial Infarction frame count was 12.3 ± 1.5 in the sevoflurane group and 15.6 ± 9.1 in the control group (P = .16). There was more ST resolution in patients treated by sevoflurane 80.7% ± 25.8% versus 56.6% ± 35.7% (P = .01). Sevoflurane had no significant adverse effect during administration.

CONCLUSIONS

Sevoflurane administration during primary PCI did not reduce infarct size. There was a trend toward a reduction in infarct size among patients with anterior MI. Sevoflurane administration was associated with improvement in ST-segment resolution.

Postconditioning with a CpG containing oligodeoxynucleotide ameliorates myocardial infarction in a murine closed-chest model

AIMS

Toll-like receptor (TLR)9 ligand CpG-oligodeoxynucleotide (CpG-ODN) exerts preconditioning in myocardial ischemia/reperfusion. We hypothesized a postconditioning effect of CpG-ODN in a murine closed-chest model of myocardial infarction.

MATERIALS AND METHODS

C57BL/6 (12 weeks, male, WT) mice were instrumented at the left anterior descending artery, then allowed 5d of recovery before 30 min ischemia. Treatments comprised: 1) PBS: 250 μl phosphate buffer solution intraperitoneally 5 min before reperfusion and 2) IPC (ischemic postconditioning): 3 twenty-second reperfusion and occlusion episodes at the end of ischemia 3) CpG-ODN: 1668 thioate 0.2 μmol/kg BW intraperitoneally 5 min before reperfusion. Infarct size was assessed via triphenyltetrazolium chloride (TTC) staining after 2 and 24h reperfusion. Myocardial mRNA-expression of cytokines was measured using real-time PCR after 2h reperfusion. Phosphatidylinositol-3 kinase (PI3K)-inhibitor wortmannin was injected intraperitoneally in WT 15 min before postconditioning and PBS in each group. Cardiac function in WT was assessed with a left-ventricular pressure-volume catheter at 24h reperfusion.

KEY FINDINGS

Following 30 min ischemia and 2h reperfusion, infarct size was diminished by 90% in WT postconditioned with CpG-ODN (2.4 ± 1.55 IS/AAR%) and IPC (1.98 ± 1.03 IS/AAR%) compared to PBS mice (23.2 ± 3.97 IS/AAR%). Infarct size increased following 24h reperfusion but the differences remained robust. Expression of TNF-α and IL-10 was increased in CpG-ODN. Wortmannin abolished the postconditioning effect of CpG-ODN and IPC. Ejection fraction and preload-recruitable stroke work were significantly greater in CpG-ODN mice.

SIGNIFICANCE

CpG-ODN confers postconditioning via activation of TLR9. Cardiac function is preserved following CpG-ODN postconditioning. The PI3K -inhibitor wortmannin attenuates CpG-ODN postconditioning.

Cardioprotective role of ischemic postconditioning in acute myocardial infarction: a systematic review and meta-analysis

BACKGROUND

Evidence suggests that ischemic postconditioning (IPoC) may reduce the extent of reperfusion injury. We performed a meta-analysis of randomized controlled trials, which compared the role of IPoC during primary percutaneous coronary intervention (PCI) to PCI alone (control group) in ST-segment elevation myocardial infarction.

METHODS

Several databases were searched, which yielded 19 studies. The outcomes of interest were measures of myocardial damage (serum cardiac enzymes and infarct size by imaging) and left ventricular function (left ventricular ejection fraction and wall motion score index). Mean difference (MD) and standardized mean difference (SMD) were used to assess the treatment effect. An inverse variance method was used to pool data into a random-effects model.

RESULTS

Ischemic postconditioning demonstrated a decrease in serum cardiac enzymes (SMD -0.48, 95% CI -0.92 to -0.05, I(2) = 92%), reduction in infarct size by imaging (SMD -0.30, 95% CI -0.58 to -0.01, I(2) = 80%), wall motion score index (MD -0.19, 95% CI -0.29 to -0.09, I(2) = 44%), and showed improvement in left ventricular ejection fraction (IPoC 52 ± 0.4, control 49.7 ± 0.4) (MD 2.78, 95% CI 0.66-4.91, I(2) = 69%). All included studies were limited by high risk of performance and publication bias.

CONCLUSIONS

Ischemic postconditioning during PCI in ST-segment elevation myocardial infarction appears to be superior to PCI alone in reduction of both myocardial injury or damage and improvement in global and regional left ventricular function. The effect seems to be more pronounced when a greater myocardial area is at risk. Given the limitations of the current available evidence, additional data from large randomized controlled trials are warranted.

Remote ischemic postconditioning during percutaneous coronary interventions: remote ischemic postconditioning-percutaneous coronary intervention randomized trial

BACKGROUND

Remote ischemic preconditioning may result in reduction in infarct size during percutaneous coronary intervention (PCI). It is unclear whether remote ischemic postconditioning (RIPost) will reduce the incidence of myocardial injury after PCI, and whether ischemic conditioning of a larger remote organ (thigh versus arm) would provide further myocardial protection.

METHODS AND RESULTS

We randomized 360 patients presenting with stable or unstable angina (28% of patients) and negative Troponin T at baseline to 3 groups: 2 groups received RIPost (induced by ischemia to upper or lower limb), and a third was the control group. RIPost was applied during PCI immediately after stent deployment, by three 5-minute cycles of blood pressure cuff inflation to >200 mm Hg in the arm or thigh (20 mm Hg in the control) with 5-minute breaks between each cycle. The primary end-point was the proportion of patients with Troponin T levels >3×ULN postprocedure (at 6 or 18-24 hours), where ULN stands for upper limit of normal. A total of 120 patients were randomized to each group. There were no differences in baseline characteristics between the 3 groups. The primary outcome occurred in 30%, 35%, and 35% of the arm, thigh, and control groups, respectively (P=0.64). There were no differences in creatine kinase or high sensitivity C-reactive protein levels after PCI or in the incidence of acute kidney injury between the groups.

CONCLUSIONS

RIPost during PCI did not reduce the incidence of periprocedural myocardial injury. Similar effect was obtained when remote ischemia was induced to the upper or lower limb.

CLINICAL TRIAL REGISTRATION URL

http://www.clinicaltrials.gov. Unique identifier: NCT00970827.

Targeting mitochondria for cardioprotection: examining the benefit for patients

ABSTRACT: 

Mitochondria are critical for sustaining life, not only as the essential powerhouses of cells but as critical mediators of cell survival and death. Mitochondrial dysfunction has been identified as a key perturbation underlying numerous pathologies including myocardial ischemia–reperfusion injury and the subsequent development of impaired left ventricular systolic function and compensatory cardiac hypertrophy. This article outlines the role of mitochondrial dysfunction in these important cardiac pathologies and highlights current cardioprotective strategies and their clinical efficacy in acute myocardial infarction and heart failure patients. Finally, we explore novel mitochondrial targets and evaluate their potential future translation for clinical cardioprotection.