Response of the human myocardium to ischemic injury and preconditioning: The role of cardiac and comorbid conditions, medical treatment, and basal redox status

Clinical usage of ischemic tolerance-where are its limits?

Ischemic tolerance is a robust internal defense mechanism of all living organisms. The effectiveness of this mechanism has been repeatedly demonstrated in experiments, but a comprehensive review of the clinical applicability of this phenomenon in practice has not yet been published. The results in clinical practice sound ambiguous and unconvincing in comparison with the results of experimental studies. Also, in many localities, the effect of ischemic tolerance was not clinically proven. For the reasons mentioned, the authors analyze the possible causes of the mentioned discrepancies and provide a comprehensive insight into the possible relevant clinical use of this phenomenon in practice for different groups of patients.

Role of Erythropoiesis-Stimulating Agents in Cardiovascular Protection in CKD Patients: Reappraisal of Their Impact and Mechanisms

Erythropoiesis-stimulating agents (ESAs) have markedly reduced the need for blood transfusion for renal anemia and are included in standard therapies for patients with chronic kidney disease (CKD). Various protective effects of ESAs on the cardiovascular system have been discovered through basic research, and the effects have received much attention because the rates of cardiovascular events and mortality are high in CKD patients. However, randomized clinical trials did not provide strong evidence that ESAs exert cardioprotection in humans, including CKD patients. It is difficult to assess the cardioprotective effects of ESAs in CKD patients through the clinical data that has been reported to date because the relationship between hemoglobin level rather than ESA dose and cardiovascular event rates was examined in most studies. Interestingly, recent studies using a rat model of CKD showed that the infarct size-limiting effect of an ESA was lost when its dose was increased to a level that normalized blood hemoglobin levels, suggesting that the optimal dose of an ESA for myocardial protection is less than the dose required to normalize hemoglobin levels. Furthermore, animal models of traditional coronary risk factors or comorbidities were resistant to the cardioprotective effects of ESAs because of interruptions in signal-mediated mechanisms downstream of erythropoietin receptors. In this review, we briefly discuss basic and clinical data on the impact of anemia on coronary and systemic circulation, the effects of CKD on the cardiovascular system, and the multiple pharmacological actions of ESAs to examine whether the ESAs that are prescribed for renal anemia exert any cardioprotection in patients with CKD.

Resveratrol activates PI3K/AKT to reduce myocardial cell apoptosis and mitochondrial oxidative damage caused by myocardial ischemia/reperfusion injury

Resveratrol is a kind of iPolyphenols widely existing in herbal medicine. Here we aim to investigate whether resveratrol can reduce the degree of myocardial ischemia/reperfusion (IR) injury and inhibit the development of oxidative stress, and elucidate the molecular mechanism of resveratrol in protecting myocardial cells. The primary rat cardiomyocytes were used to establish an ischemia/reperfusion model in vitro, and a series of routine biochemical experiments were conducted to explore the antioxidant and anti-apoptotic effects of resveratrol in myocardial ischemia-reperfusion injury. Compared with that of the simulated ischemia-refusion (SIR) group, cell viability in the SIR and resveratrol co-treatment groups increased significantly (P < 0.001), the release of lactate dehydrogenase (LDH) and creatine kinase MB (CKMB) decreased, the positive rate of reactive oxygen species (ROS) in cardiomyocytes decreased, and the concentration of catalase and glutathione peroxidase increased significantly (P < 0.001). Besides, resveratrol can activate PI3K/AKT signaling pathway. PI3K siRNA can inhibit the PI3K/AKT signaling mediated by resveratrol. The addition of resveratrol can significantly increase the activity of mitochondrial superoxide dismutase (SOD) and reduce the malondialdehyde (MDA), which indicates that the oxidative damage of mitochondria induced by resveratrol was significantly weakened. The mitochondrial functional changes induced by resveratrol can be reversed by PI3K siRNA. In conclusion, our study shows that resveratrol can reduce ROS in cardiomyocytes by PI3K/AKT signaling pathway activation, and effectively inhibit the apoptosis of cardiomyocytes, thus having a direct protective effect on cardiomyocytes under SR.

Does the type of cardioplegia used during valve surgery influence operative nadir hematocrit and transfusion requirements?

INTRODUCTION

Myocardial protection is performed using diverse cardioplegic (CP) solutions with various combinations of chemical and blood constituents. Newer CP formulations that extend ischemic intervals may require greater asanguineous volume, contributing to hemodilution.

METHODS

We evaluated intraoperative hemodilution and red blood cell (RBC) transfusion rates among three common CP solutions during cardiac valve surgery. Data from 5,830 adult cardiac primary valve procedures where either four-to-one blood CP (4:1), del Nido solution (DN) or microplegia (MP) was used at 173 United States surgical centers. The primary outcome was the nadir hematocrit (Hct) during cardiopulmonary bypass (CPB), with a secondary outcome of total units of RBC transfused intraoperatively. Outcomes were assessed using mixed-effects regression, with controls for patient size, age, first Hct in the operating room, ultrafiltration volume, net bypass circuit priming volume, anesthesia and perfusion asanguineous volumes, cross-clamp and total procedure times, procedure type, reoperation, hospital, surgeon and twelve other patient and procedural variables.

RESULTS

A total of 2,641 patients received 4:1 (45.3%), 1,864 received DN (32.0%) and 1,325 received MP (22.7%). There were only slight differences in the central tendency (mean (SD)) for crude nadir Hct on CPB: 4:1, 25.5 (4.5), DN, 26.0 (4.6) and MP, 26.5 (4.7). After controlling for numerous operative and patient characteristics, the regression-adjusted estimate of the nadir Hct on CPB for MP was 26.2%, compared to 25.7% for 4:1 and 25.7% for DN; differences between MP and the other methods were statistically significant (p<0.01). Unadjusted mean RBC units transfused per patient was very similar across the groups (4:1, 2.2; MP, 2.3; DN, 2.4). Regression-adjusted estimates for the number of units of RBC transfused intraoperatively showed no statistically significant differences between CP methods.

CONCLUSIONS

In patients undergoing cardiac valve surgery, the type of CP did not have a strong clinical impact on hemodilution or transfusion. Choice of a myocardial preservation solution can be made independently of its effect on intraoperative Hct.