Postconditioning against ischaemia-reperfusion injury: ready for wide application in patients?

Percutaneous management of reperfusion arrhythmias during primary percutaneous coronary intervention: a case report

Background

Myocardial reperfusion may cause profound electrophysiological alterations and can lead to serious reperfusion arrhythmias (RA). Management of RA and the accompanying electrical storm that may occur remains a problem. To our knowledge, the role of balloon re-inflation of the infarct-related artery (IRA) has never been addressed as a treatment modality for RA presenting as ventricular tachycardia (VT) with pulse or supraventricular tachycardia (SVT).

Case presentation

Six patients presenting with ST elevation myocardial infarction (STEMI) in the first 12 h, who underwent successful primary percutaneous coronary intervention (PCI), developed RA in the cathlab after restoration of flow in the IRA. The RA was in the form of VT with pulse, except in one patient who had SVT. In four patients, the RA was associated with hemodynamic instability. The mean age of the studied patients was 59.16 ± 7.94 years, and four were males. Coronary artery disease risk factors were prevalent, with four patients being hypertensive, two dyslipidemic, one diabetic, and 2 current smokers. One patient had a history of prior myocardial infarction (MI), and none had a history of congestive heart failure. The coronary angiography showed 100% occlusion of IRA in all patients and 2–3-vessel disease was present in 50%. PCI was successful with restoration of thrombolysis in myocardial infarction (TIMI) 2–3 flow in IRA in all cases. The mean time to revascularization from the onset of chest pain was 4.88 ± 2.68 h. In all cases, balloon re-inflation was successful in terminating the arrhythmias. None of the patients needed direct current cardioversion or anti-arrhythmic drugs for management of the acute arrhythmia.

Conclusion

Balloon re-inflation of IRA was successful in terminating RA that develop in the form of VT with pulse or SVT.

Mechanistic Role of mPTP in Ischemia-Reperfusion Injury

Acute myocardial infarction (MI) is a major cause of death and disability worldwide. The treatment of choice for reducing ischemic injury and limiting infarct size (IS) in patients with ST-segment elevation MI (STEMI) is timely and effective myocardial reperfusion via primary percutaneous coronary intervention (PCI). However, myocardial reperfusion itself may induce further cardiomyocyte death, a phenomenon known as reperfusion injury (RI). The opening of a large pore in the mitochondrial membrane, namely, the mitochondrial permeability transition pore (mPTP), is widely recognized as the final step of RI and is responsible for mitochondrial and cardiomyocyte death. Although myocardial reperfusion interventions continue to improve, there remain no effective therapies for preventing RI due to incomplete knowledge regarding RI components and mechanisms and to premature translations of findings from animals to humans. In the last year, increasing amounts of data describing mPTP components, structure, regulation and function have surfaced. These data may be crucial for gaining a better understanding of RI genesis and for planning future trials evaluating new cardioprotective strategies. In this chapter, we review the role of the mPTP in RI pathophysiology and report on recent studies investigating its structure and components. Finally, we provide a brief overview of principal cardioprotective strategies and their pitfalls.

Featured Article: Pharmacological postconditioning with delta opioid attenuates myocardial reperfusion injury in isolated porcine hearts

Ischemic preconditioning has been utilized to protect the heart from ischemia prior to ischemia onset, whereas postconditioning is employed to minimize the consequences of ischemia at the onset of reperfusion. The underlying mechanisms and pathways of ischemic pre- and postconditioning continue to be investigated as therapeutic targets. We evaluated the administration of a delta opioid agonist or cariporide on various parameters associated with myocardial reperfusion injury upon reperfusion of isolated porcine hearts. The hearts were reperfused in vitro with a Krebs buffer containing either: (1) 1 µM Deltorphin D (delta opioid specific agonist, n = 6); (2) 3 µM cariporide (sodium-hydrogen exchange inhibitor, n = 4); or (3) no treatment (control, n = 6). Subsequently, postischemic hemodynamic performance, arrhythmia burden, relative tissue perfusion, and development of necrosis were assessed over a 2 h reperfusion period. Postconditioning with Deltorphin D significantly improved diastolic relaxation (Tau, P < 0.05 versus controls) and decreased the incidence of ventricular arrhythmias during early reperfusion. Additionally, these treated hearts demonstrated increased tissue perfusion after 2 h ( P < 0.05 versus controls), suggesting improved microvascular function. Delta opioid agonists elicited the potential to attenuate reperfusion injury, suggesting a postconditioning effect of these agents. We hypothesize that the induced benefits of delta opioids, in part, are associated with decreased calcium influx on reperfusion, independent of sodium-hydrogen exchange inhibition. Such agents may have a potential role in minimizing reperfusion injury associated with coronary stenting, bypass surgery, myocardial infarction, cardiac transplantation, or with the utilization of heart preservation systems. Impact statement In this study, we found that postconditioning with Deltorphin D significantly improved diastolic relaxation and decreased the incidence of ventricular arrhythmias during early reperfusion. Furthermore, these treated hearts demonstrated increased tissue perfusion after 2 h, suggesting improved microvascular function. Delta opioid agonists attenuated reperfusion injury, suggestive of a postconditioning effect. Such agents may have a potential role in minimizing reperfusion injury associated with coronary stenting, bypass surgery, myocardial infarction, cardiac transplantation, or with the utilization of heart preservation systems.

Ischemic Postconditioning After Routine Thrombus Aspiration During Primary Percutaneous Coronary Intervention: Rationale and Design of the POstconditioning Rotterdam Trial

BACKGROUND

Whether ischemic postconditioning (IPOC) immediately after routine thrombus aspiration (TA) reduces infarct size (IS) in patients with ST-segment elevation myocardial infarction (STEMI) undergoing primary percutaneous coronary intervention (PPCI) has not been established.

STUDY DESIGN

The POstconditioning Rotterdam Trial (PORT) is a dual-center, prospective, open-label, randomized trial with blinded endpoint evaluation enrolling 72 subjects with first-time STEMI, and an occluded infarct-related artery (IRA) without collaterals undergoing PPCI. Subjects are randomized 1:1 to a strategy of IPOC immediately after TA followed by stenting of the IRA or to conventional percutaneous coronary intervention (PCI), including TA followed by stenting of the IRA (controls). Cardiac magnetic resonance imaging (MRI) is performed at 3-5 days after STEMI and at 3 months. The primary endpoint is IS at 3 months measured by delayed enhancement MRI. Other secondary endpoints include MRI-derived microvascular obstruction (MVO), left ventricular ejection fraction, myocardial salvage index, enzymatic IS, ST-segment resolution, myocardial blush grade, microcirculatory resistance, inflammation markers, and clinical events through 3-month follow-up.

CONCLUSIONS

PORT is testing the hypothesis that adding IPOC (against lethal reperfusion injury) to TA (against distal embolization and MVO) is cardioprotective and reduces ultimate IS in STEMI patients undergoing PPCI (Dutch Trial Register identifier: NTR4040). © 2015 Wiley Periodicals, Inc.

Mechanical post-conditioning in STEMI patients undergoing primary percutaneous coronary intervention

Although early myocardial reperfusion via primary percutaneous coronary intervention (PCI) allows the preservation of left ventricular function and improves outcome, the acute restoration of blood flow may contribute to the pathophysiology of infarction, a complex phenomenon called reperfusion injury. First described in animal models of coronary obstruction, mechanical post-conditioning, a sequence of repetitive interruption of coronary blood flow applied immediately after reopening of the occluded vessel, was able to reduce the infarct size. However, evidence of its real benefit remains controversial. This review describes the mechanisms of post-conditioning action and the different protocols employed focusing on its impact on primary PCI outcome.

Molecular identity of the mitochondrial permeability transition pore and its role in ischemia-reperfusion injury

The mitochondrial permeability transition is a key event in cell death. Intense research efforts have been focused on elucidating the molecular components of the mitochondrial permeability transition pore (mPTP) to improve the understanding and treatment of various pathologies, including neurodegenerative disorders, cancer and cardiac diseases. Several molecular factors have been proposed as core components of the mPTP; however, further investigation has indicated that these factors are among a wide range of regulators. Thus, the scientific community lacks a clear model of the mPTP. Here, we review the molecular factors involved in the regulation and formation of the mPTP. Furthermore, we propose that the mitochondrial ATP synthase, specifically its c subunit, is the central core component of the mPTP complex. Moreover, we discuss the involvement of the mPTP in ischemia and reperfusion as well as the results of clinical studies targeting the mPTP to ameliorate ischemia-reperfusion injury. This article is part of a Special Issue entitled "Mitochondria: From Basic Mitochondrial Biology to Cardiovascular Disease".

Impact of multiple balloon inflations during primary percutaneous coronary intervention on infarct size and long-term clinical outcomes in ST-segment elevation myocardial infarction: real-world postconditioning

Interrupting myocardial reperfusion with intermittent episodes of ischemia (i.e., postconditioning) during primary percutaneous coronary intervention (PPCI) has been suggested to protect myocardium in ST-segment elevation myocardial infarction (STEMI). Nevertheless, trials provide inconsistent results and any advantage in long-term outcomes remains elusive. Using a retrospective study design, we evaluated the impact of balloon inflations during PPCI on enzymatic infarct size (IS) and long-term outcomes. We included 634 first-time STEMI patients undergoing PPCI with an occluded infarct-related artery and adequate reperfusion thereafter and divided these into: patients receiving 1–3 inflations in the infarct-related artery [considered minimum for patency/stent placement (controls); n = 398] versus ≥4 [average cycles in clinical protocols (postconditioning analogue); n = 236]. IS, assessed by peak creatine kinase, was lower in the postconditioning analogue group compared with controls [median (interquartile range) 1,287 (770–2,498) vs. 1,626 (811–3,057) UI/L; p = 0.02], corresponding to a 21 % IS reduction. This effect may be more pronounced in women, patients without diabetes/hypercholesterolemia, patients presenting within 3–6 h or with first balloon re-occlusion ≤1 min. No differences were observed in 4-year mortality or MACCE between groups. Four or more inflations during PPCI reduced enzymatic IS in STEMI patients under well-defined conditions, but did not translate into improved long-term outcomes in the present study. Large-scale randomized trials following strict postconditioning protocols are needed to clarify this effect.

The impact of ischemia-reperfusion injury on the effectiveness of primary angioplasty in ST-segment elevation myocardial infarction

The most effective method of reperfusion in patients with ST-segment elevation myocardial infarction (STEMI) is primary percutaneous coronary intervention (PCI), assisted by aspiration thrombectomy and administration of antiplatelet agents and anticoagulants. However, effective restoration of blood flow in the infarct-related artery may paradoxically result in further damage to the heart muscle. This phenomenon, called ischemia-reperfusion injury (IRI), can significantly reduce the beneficial effects of reperfusion therapy. The rapid restoration of blood flow to the previously ischemic area causes a number of pathophysiological mechanisms leading to increased necrosis of myocytes still viable at the end of the ischemic period. It has been postulated that there are several strategies that can reduce damage to the heart muscle. Attempts to translate the results of experimental trials has been disappointing. More recently, however, some of the clinical benefits of ischemic postconditioning in which reperfusion in patients with STEMI who are undergoing PCI is interrupted with short episodes of ischemia were demonstrated. This renewed the interest in the reperfusion phase as a target for cardioprotective therapy. Research in this field has also been reinforced by the discovery of new potential targets for treatment that protects against IRI, such as the kinase pathway to protect against damage (reperfusion injury salvage kinases – RISK) and mitochondrial permeability transition pore. It seems that these findings will help to develop strategies that will improve the efficiency of mechanical reperfusion and may translate into long-term clinical effects.

Targeting reperfusion injury in acute myocardial infarction: a review of reperfusion injury pharmacotherapy

INTRODUCTION

Acute myocardial infarction (AMI) (secondary to lethal ischemia-reperfusion [IR]) contributes to much of the mortality and morbidity from ischemic heart disease. Currently, the treatment for AMI is early reperfusion; however, this itself contributes to the final myocardial infarct size, in the form of what has been termed 'lethal reperfusion injury'. Over the last few decades, the discovery of the phenomena of ischemic preconditioning and postconditioning, as well as remote preconditioning and remote postconditioning, along with significant advances in our understanding of the cardioprotective pathways underlying these phenomena, have provided the possibility of successful mechanical and pharmacological interventions against reperfusion injury.

AREAS COVERED

This review summarizes the evidence from clinical trials evaluating pharmacological agents as adjuncts to standard reperfusion therapy for ST-elevation AMI.

EXPERT OPINION

Reperfusion injury pharmacotherapy has moved from bench to bedside, with clinical evaluation and ongoing clinical trials providing us with valuable insights into the shortcomings of current research in establishing successful treatments for reducing reperfusion injury. There is a need to address some key issues that may be leading to lack of translation of cardioprotection seen in basic models to the clinical setting. These issues are discussed in the Expert opinion section.