Preconditioning

Abstract

Case presentation: A 45-yearold man with coronary artery disease is found to be in good condition after his annual medical checkup, and his doctor advises him to continue with the same drugs, a prudent diet, entertainment, and regular exercise; however, the patient is afraid that he will not have time to exercise regularly. Benefits of ExerciseClinicians have learned about the beneficial effects of several factors that may prevent a myocardial infarction (MI), including avoidance of smoking; treatment of high blood pressure, diabetes, dyslipidemia, and obesity; and regular performance of exercise. This last factor is based on epidemiological observations such as a decrease in the incidence of MI in men who perform heavy work 1,2 ; however, it is only in the last few years that the beneficial effect of exercise has obtained plausible explanations of its own, that is, apart from its effect on other risk factors. There are at least 3 distinct mechanisms for this benefit: (1) Improvement of endothelial function, thereby preventing atherosclerosis and coronary occlusion 3 ; (2) prevention of remodeling after MI through the expression of oxidative metabolism-related genes 4 ; and (3) delaying acute ischemic injury after a coronary occlusion by preconditioning.Since the discovery of ischemic preconditioning by Murry et al 5 in 1986, studies have appeared in the literature searching for its mechanisms and for alternative ways to trigger it. The concept that 1 or 2 episodes of brief ischemia (Ϸ5 minutes in duration each), induced a few minutes or a few hours (early preconditioning) or 24 to 72 hours (late preconditioning or second window) before a prolonged coronary occlusion, followed by reperfusion substantially decreases the speed of the ischemic injury and limits infarct size is firmly established in all animal species studied in the experimental laboratory. 6 It is one of the most powerful means of protecting the myocardium with the exception of early reperfusion. Several lines of evidence in coronary patients suggest but do not prove that the human myocardium is also protected by ischemic preconditioning. For example, preinfarction angina is associated with a smaller infarct size; a lower incidence of congestive heart failure, shock, and ventricular arrhythmias; and decreased mortality. [7][8][9] The ST-segment elevation observed during angioplasty decreases after subsequent occlusions, 10 which suggests that each occlusion provides preconditioning for the ischemic effect of the next one. Protocols of ischemic preconditioning before coronary artery bypass grafting preserve ATP levels during the subsequent global ischemic period 11 and decrease serum levels of troponin T, thereby suggesting a smaller infarct size. 12 Finally, the progressive decrease in the magnitude of ischemia during several consecutive episodes of exercise in patients with demand angina (warm-up phenomenon) suggests the preconditioning effect of each episode. 13 The protective effect of ischemic preconditioning can be reproduced by several drugs,...

Cardioprotection conferred by exercise training is blunted by blockade of the opioid system

“…In contrast to previous studies,12,31,32 our study did not demonstrate an increase in capillary density in the treated groups, in relation to the control. This might be because, in our experiment, we submitted animals to 12 weeks of ET, and, according to a previous study,33 ET causes an increase of capillary density, in relation to the control group, after 3 weeks of training, and this increase is not seen later.…”

Prenatal cocaine exposure abolished ischemic preconditioning-induced protection in adult male rat hearts: role of PKCε

“…Together, our findings strongly suggest a causal relationship between alterations to PKCε and increased myocardial sensitivity to ischemia in the adult animal with prenatal cocaine exposure. These findings could have significant clinical importance, a contention supported by the observations that preinfarction angina and exercise protect the heart from ischemic injury via the IPC pathway, as well as other evidence that IPC is an important physiological protective mechanism (9,16,18). Given that cocaine abuse in pregnant women is a significant problem, especially in urban areas, the present finding suggests that intrauterine cocaine exposure may result in significant long-term changes to the myocardiocytes and be a risk factor for morbidity and mortality secondary to myocardial ischemia in adult male offspring.…”

Circulating Levels of miR‐133a Predict the Regression Potential of Left Ventricular Hypertrophy After Valve Replacement Surgery in Patients With Aortic Stenosis

“…Surgical indication for AVR in asymptomatic patients is a particularly controversial issue that has, in the past, led to the inclusion and subsequent withdrawal of some indications in successive versions of the intersocietal guidelines for the management of patients with valvular heart disease. 36 In this regard, evolution towards irreversible hypertrophy should favor earlier surgery in asymptomatic AS patients with excessive or rapidly growing LVM for the sake of postoperative LVM normalization. 7 , 37 The discovery of biomarkers that are informative, prior to surgery, with regard to the postoperative prognosis could represent a significant advance for the identification of patients who would benefit most from earlier surgery.…”