Preinfarction angina does not alter infarct size and in hospital outcome after acute myocardial infarction with ST elevation

Time to Give Up on Cardioprotection?

The mortality from acute myocardial infarction (AMI) remains significant, and the prevalence of post-myocardial infarction heart failure is increasing. Therefore, cardioprotection beyond timely reperfusion is needed. Conditioning procedures are the most powerful cardioprotective interventions in animal experiments. However, ischemic preconditioning cannot be used to reduce infarct size in patients with AMI because its occurrence is not predictable; several studies in patients undergoing surgical coronary revascularization report reduced release of creatine kinase and troponin. Ischemic postconditioning reduces infarct size in most, but not all, studies in patients undergoing interventional reperfusion of AMI, but may require direct stenting and exclusion of patients with >6 hours of symptom onset to protect. Remote ischemic conditioning reduces infarct size in patients undergoing interventional reperfusion of AMI, elective percutaneous or surgical coronary revascularization, and other cardiovascular surgery in many, but not in all, studies. Adequate dose-finding phase II studies do not exist. There are only 2 phase III trials, both on remote ischemic conditioning in patients undergoing cardiovascular surgery, both with neutral results in terms of infarct size and clinical outcome, but also both with major problems in trial design. We discuss the difficulties in translation of cardioprotection from animal experiments and proof-of-concept trials to clinical practice. Given that most studies on ischemic postconditioning and all studies on remote ischemic preconditioning in patients with AMI reported reduced infarct size, it would be premature to give up on cardioprotection.

Impact of prodromal symptoms on prehospital delay in patients with first-time acute myocardial infarction in Korea

BACKGROUND

Information is limited concerning how affected individuals respond to early warning signs before their acute coronary event and how the presence of prodromal symptoms impacts prehospital delay.

OBJECTIVES

This study's aim was to identify the characteristics and interpretation of prodromal symptoms in patients with a first-time acute myocardial infarction (AMI) and to determine whether the presence of prodromal symptoms was predictive of prehospital delay.

SUBJECTS AND METHODS

This was a descriptive study using semistructured interview. A total of 271 hospitalized patients diagnosed as having AMI were interviewed from November 2007 to December 2008 at a university hospital in Korea. Patients were queried regarding whether they noticed a most troubling prodromal symptom prior to their acute cardiac event and how they responded to the symptom.

RESULTS

Men (53.0%) and women (54.2%) experienced prodromal symptoms. Patients who reported prodromal symptoms were more likely to be older and to have no chest pain upon hospitalization than those with no prodromes. Many patients did not generally recognize the importance of their warning symptoms; only about 40% visited a clinic in response to any prodromal symptom. Logistic regression analyses revealed that the presence of prodromal symptoms was an independent predictor affecting prehospital delay of more than 3 hours and more than 12 hours.

CONCLUSIONS

Recognizing prodromal symptoms as needing attention could be a trigger for patients to seek medical help earlier. Educational strategies should focus on improving awareness of prodromal symptoms of AMI, particularly in those with a family history or at high risk for cardiovascular disease.

Beneficial effect of ischemic preconditioning on post-infarction left ventricular remodeling and global left ventricular function

BACKGROUND

Preinfarction angina (PA) is a clinical analogue of ischemic preconditioning that improves postinfarct prognosis. Data concerning the association of PA with post infarction left ventricular (LV) remodeling and LV diastolic function are limited. We aimed to evaluate this association in patients with acute myocardial infarction (AMI) in the modern clinical era of widespread use of revascularization and antiremodeling medical treatment.

METHODS

We studied 53 patients with anterior AMI who underwent complete reperfusion and received up to date antiremodeling medical treatment. LV remodeling, systolic and diastolic function were assessed using 2D echocardiography at baseline and 6 at months follow-up. Patients were divided into two groups regarding the presence or absence of PA.

RESULTS

LV remodeling at follow-up was less frequent in the PA group (25 vs. 55 %, P<.05). Patients with PA had lower end-systolic volume index at baseline and follow up (24.1±6 vs. 30.1±14 ml/m(2), P<.001 and 25.3±8 vs. 35.6±2 ml/m(2), P=.001 respectively). Additionally at 6 months, they had better LV ejection fraction (52.1±9 vs. 42.9±10 %, P=.002) and exhibited improved diastolic filling as reflected by mitral E/e' (14.6±5 vs. 18.8±8, P=.05).

CONCLUSIONS

Ischemic preconditioning in the form of PA promotes better LV systolic and diastolic function in the mid-term and is associated with less postinfarct LV remodeling in this specific study population. The results of the study underline the possible need for further risk stratification of AMI patients regarding the absence of PA.

Loss of cardioprotection with ageing

Not only the prevalence, but also the mortality due to ischaemic cardiovascular disease is higher in older than in young humans, and the demographic shift towards an ageing population will further increase the prevalence of age-related cardiovascular disease. In order to develop strategies aimed to limit reversible and irreversible myocardial damage in older patients, there is a need to better understand age-induced alterations in protein expression and cell signalling. Cardioprotective phenomena such as ischaemic and pharmacological pre and postconditioning attenuate ischaemia/reperfusion injury in young hearts. Whether or not pre and postconditioning are still effective in aged organs, animals, or patients, i.e. under conditions where such cardioprotection is most relevant, is still a matter of debate; most studies suggest a loss of protection in aged hearts. The present review discusses changes in protein expression and cell signalling important to ischaemia/reperfusion injury with myocardial ageing. The efficacy of cardioprotective manoeuvres, e.g. ischaemic pre and postconditioning in aged organs and animals will be discussed, and the development of strategies aimed to antagonize the age-induced loss of protection will be addressed.

Interaction of cardiovascular risk factors with myocardial ischemia/reperfusion injury, preconditioning, and postconditioning

Therapeutic strategies to protect the ischemic myocardium have been studied extensively. Reperfusion is the definitive treatment for acute coronary syndromes, especially acute myocardial infarction; however, reperfusion has the potential to exacerbate lethal tissue injury, a process termed "reperfusion injury." Ischemia/reperfusion injury may lead to myocardial infarction, cardiac arrhythmias, and contractile dysfunction. Ischemic preconditioning of myocardium is a well described adaptive response in which brief exposure to ischemia/reperfusion before sustained ischemia markedly enhances the ability of the heart to withstand a subsequent ischemic insult. Additionally, the application of brief repetitive episodes of ischemia/reperfusion at the immediate onset of reperfusion, which has been termed "postconditioning," reduces the extent of reperfusion injury. Ischemic pre- and postconditioning share some but not all parts of the proposed signal transduction cascade, including the activation of survival protein kinase pathways. Most experimental studies on cardioprotection have been undertaken in animal models, in which ischemia/reperfusion is imposed in the absence of other disease processes. However, ischemic heart disease in humans is a complex disorder caused by or associated with known cardiovascular risk factors including hypertension, hyperlipidemia, diabetes, insulin resistance, atherosclerosis, and heart failure; additionally, aging is an important modifying condition. In these diseases and aging, the pathological processes are associated with fundamental molecular alterations that can potentially affect the development of ischemia/reperfusion injury per se and responses to cardioprotective interventions. Among many other possible mechanisms, for example, in hyperlipidemia and diabetes, the pathological increase in reactive oxygen and nitrogen species and the use of the ATP-sensitive potassium channel inhibitor insulin secretagogue antidiabetic drugs and, in aging, the reduced expression of connexin-43 and signal transducer and activator of transcription 3 may disrupt major cytoprotective signaling pathways thereby significantly interfering with the cardioprotective effect of pre- and postconditioning. The aim of this review is to show the potential for developing cardioprotective drugs on the basis of endogenous cardioprotection by pre- and postconditioning (i.e., drug applied as trigger or to activate signaling pathways associated with endogenous cardioprotection) and to review the evidence that comorbidities and aging accompanying coronary disease modify responses to ischemia/reperfusion and the cardioprotection conferred by preconditioning and postconditioning. We emphasize the critical need for more detailed and mechanistic preclinical studies that examine car-dioprotection specifically in relation to complicating disease states. These are now essential to maximize the likelihood of successful development of rational approaches to therapeutic protection for the majority of patients with ischemic heart disease who are aged and/or have modifying comorbid conditions.

Preoperative unstable angina causes venous adaptation to surgical graft injury

Ischemic preconditioning may provide a systemic organ protection, evident as the phenomenon known as remote preconditioning. Unstable angina may be a clinical analogue to ischemic preconditioning. Vein graft harvesting induces inflammation of the graft wall. We hypothesized that preoperative unstable angina preconditions vein grafts and reduces the inflammatory response to graft harvesting. Consecutive patients with stable or unstable angina undergoing open heart surgery (n = 12 in each group) were studied. Saphenous vein biopsies were collected at the start of graft harvesting, and when the last proximal anastomosis to the aorta was finished (average 112 minutes later). Gene expression of inflammatory mediators (tumor necrosis factor alpha, interleukin-1beta (IL-1beta), E-selectin (CD62E), intercellular leukocyte adhesion molecule 1, inducible nitric oxide synthase, endothelin-1) increased after surgical handling (semiquantitative RT-PCR). In vein grafts from unstable patients the increase was attenuated for Il-1beta (p < 0.004) and CD62E (p < 0.001). In stable patients the protein expression of IkappaBalpha and heat shock protein72 was reduced by surgical handling (p < 0.04), but was not influenced in unstable patients (immunoblotting). In vitro relaxation to acetylcholine was enhanced, and contractions to phenylephrine and endothelin-1 were attenuated in veins rings from unstable patients (p < 0.003). In conclusion, surgical handling of vein grafts induces inflammation of the vessel wall. This response was reduced in grafts from patients with unstable angina, indicating a possible systemic preconditioning-like effect of acute coronary syndromes.

The roles of alpha- and beta-adrenoceptor stimulation in myocardial ischaemia

beta-Adrenoceptor (AR) ligands have been the mainstay of cardiovascular therapy for decades, with beta-AR antagonist being used for hypertension, angina and myocardial infarction and adrenaline in use for cardiopulmonary resuscitation for nearly 100 years. Ischaemia of the heart through coronary artery occlusion causes cell injury and death through necrosis and apoptosis. Reperfusion of the ischaemic myocardium results in cardiac dysfunction and infarction. Stimulation of alpha- and beta-ARs in the ischaemic heart have variable and inconsistent effects depending on when the agonist is applied. This review describes the different effects of stimulation of the three established beta-AR subtypes (beta(1)-, beta(2)- and beta(3)-ARs) either before ischaemia (preconditioning) or during ischaemia and reperfusion of the heart (postconditioning). Brief periods of ischaemia preceding a major ischaemic episode can have a protective effect against post-ischaemia-reperfusion damage, known as ischaemic preconditioning. This review considers the role of endogenous catecholamines released during preconditioning and the nature of the adrenoceptor subtypes that mediate these effects. The clinical significance of this to the use of beta-AR antagonists is considered. The transduction pathways and effects on apoptosis of the cardioprotective and deleterious effects of AR activation are considered. This commentary reviews the literature and attempts to bring together a unified synopsis of the effects of adrenoceptor stimulation in myocardial ischaemia and the potential clinical relevance.