Six-years survival and predictors of mortality after CABG using cold vs. warm blood cardioplegia in elective and emergent settings

Cardioprotection in cardiovascular surgery

Since the invention of cardiopulmonary bypass, cardioprotective strategies have been investigated to mitigate ischemic injury to the heart during aortic cross-clamping and reperfusion injury with cross-clamp release. With advances in cardiac surgical and percutaneous techniques and post-operative management strategies including mechanical circulatory support, cardiac surgeons are able to operate on more complex patients. Therefore, there is a growing need for improved cardioprotective strategies to optimize outcomes in these patients. This review provides an overview of the basic principles of cardioprotection in the setting of cardiac surgery, including mechanisms of cardiac injury in the context of cardiopulmonary bypass, followed by a discussion of the specific approaches to optimizing cardioprotection in cardiac surgery, including refinements in cardiopulmonary bypass and cardioplegia, ischemic conditioning, use of specific anesthetic and pharmaceutical agents, and novel mechanical circulatory support technologies. Finally, translational strategies that investigate cardioprotection in the setting of cardiac surgery will be reviewed, with a focus on promising research in the areas of cell-based and gene therapy. Advances in this area will help cardiologists and cardiac surgeons mitigate myocardial ischemic injury, improve functional post-operative recovery, and optimize clinical outcomes in patients undergoing cardiac surgery.

Warm versus cold cardioplegia in cardiac surgery: A meta-analysis with trial sequential analysis

Objective

This meta-analysis aimed to compare clinical outcomes of warm and cold cardioplegia in cardiac surgeries in adult patients, with trial sequential analysis (TSA) used to determine the conclusiveness of the results.

Methods

Electronic searches were performed on PubMed, Medline, Scopus, EMBASE, and Cochrane library to identify all studies that compared warm and cold cardioplegia in cardiac surgeries. Primary end points were in-hospital or 30-day mortality, myocardial infarction, low cardiac output syndrome, intra-aortic balloon pump use, stroke, and new atrial fibrillation. Secondary end points were acute kidney injury, hospital length of stay, and intensive care unit length of stay. Prespecified subgroup analyses were performed for (1) studies published since publication of Fan and colleagues in 2010, (2) randomized controlled studies, (3) studies with low risk of bias, (4) coronary artery bypass graft surgeries, and (5) studies with cold blood versus those with cold crystalloid cardioplegia. TSA was performed to determine conclusiveness of the results, using on all outcomes without significant heterogeneity from studies of low risk of bias.

Results

No significant differences were found between post-operative rates of mortality, myocardial infarction, low cardiac output syndrome, intra-aortic balloon pump use, stroke, new atrial fibrillation, and acute kidney injury between warm and cold cardioplegia. TSA concluded that current evidence was sufficient to rule out a 20% relative risk reduction in these outcomes.

Conclusions

Concerning safety outcomes, current evidence suggests that the choice between warm and cold cardioplegia remains in the surgeon's preference.

Higher Mortality in Women after Coronary Artery Bypass: Meta-analysis & Bias Analysis of Confounding

BACKGROUND

Some studies suggest the observed higher mortality in women than men after coronary artery bypass grafting (CABG) is due to confounding. Our meta-analysis aimed to 1) summarize the effect of sex on mortality following CABG and 2) identify whether unmeasured confounding likely explains the apparent higher mortality in women.

METHODS

MEDLINE, Embase, and CENTRAL databases were searched for studies examining sex and 30-day mortality following CABG. We used random-effects meta-analysis to estimate the summary odds ratio (OR) of mortality in women versus men using 1) unadjusted study results and 2) adjusted study results. Available confounders data from included studies was identified. Using the OR of measured confounders and the risk of death to inform unmeasured confounding effects, we performed bias analysis simulation to correct potential unmeasured confounding in our summary OR.

RESULTS

From 7138 retrieved studies, 112 were included (N=5,008,262 patients), 25 studies reported adjusted OR (N=770,450 patients). The overall 30-day mortality was 4.9% in women vs. 3.3% in men. The unadjusted summary OR (1.81, 95% CI 1.72 to 1.91) and adjusted summary OR (1.40, 95% CI 1.35 to 1.45) demonstrated that women had an increased risk of 30-day mortality compared to men. Simulations correcting for unmeasured confounding that mostly ranged from 1.05 to 1.80, supporting a higher risk of death in women after CABG.

CONCLUSIONS

The findings of this review suggest confounding is unlikely to account for the increased risk of mortality in women after CABG and that biological factors have a casual effect.

MicroRNA Expression Profile Changes after Cardiopulmonary Bypass and Ischemia/Reperfusion-Injury in a Porcine Model of Cardioplegic Arrest

Identification of microRNAs (miRNA) associated with cardiopulmonary bypass, cardiac arrest and subsequent myocardial ischemia/reperfusion may unravel novel therapeutic targets and biomarkers. The primary aim of the present study was to investigate the effects of cardiopulmonary bypass and temperature of cardioplegic arrest on myocardial miRNA profile in pigs' left ventricular tissue. We employed next-generation sequencing to analyse miRNA profiles in the following groups: (1) hearts were arrested with antegrade warm St Thomas Hospital No. 2 (STH2) cardioplegia (n = 5; STH2-warm, 37 °C) and (2) cold STH2 (n = 6; STH2-cold, 4 °C) cardioplegia. Sixty min of ischemia was followed by 60 min of on-pump reperfusion with an additional 90 min of off-pump reperfusion. In addition, two groups without cardiac arrest (off-pump and on-pump group; n = 3, respectively) served as additional controls. STH2-warm and STH2-cold cardioplegia revealed no hemodynamic differences. In contrast, coronary venous creatine kinase-myocardial band (CK-MB) levels were significantly lower in pigs receiving STH2-warm cardioplegia (p < 0.05). Principal component analysis revealed that cardiopulmonary bypass and cardioplegic arrest markedly affected miRNAs in left ventricular tissue. Accordingly, ssc-miR-122, ssc-miR-10a-5p, ssc-miR-193a-3p, ssc-miR-499-3p, ssc-miR-374a-5p, ssc-miR-345-5p, ssc-miR-142-3p, ssc-miR-424-5p, ssc-miR-545-3p, ssc-miR-30b-5p, ssc-miR-145-5p, ssc-miR-374b-5p and ssc-miR-139-3p were differently regulated by cardiopulmonary bypass (false discovery rate (FDR) < 0.05 versus off-pump group). However, only ssc-miR-451 was differently expressed between STH2-warm and STH2-cold (FDR < 0.05). These data demonstrate for the first time that cardiopulmonary bypass and temperature of cardioplegic solution affected the expression of miRNAs in left ventricular tissue. In conclusion, specific miRNAs are potential therapeutic targets for limiting ischemia-reperfusion injury in patients undergoing cardiac surgery.

Warm Blood Cardioplegia for Myocardial Protection: Concepts and Controversies

Warm blood cardioplegia has been an established cardioplegic method since the 1990s, yet it remains controversial in regard to myocardial protection. This review will describe the physiologic and technical concepts behind warm blood cardioplegia, as well as outline the current basic and clinical research that evaluates its usefulness. Controversies regarding this technique will also be reviewed. A long history of experimental data indicates that warm blood cardioplegia is safe and effective and thus suitable myocardial protection during cardiopulmonary bypass surgeries.

Blood cardioplegia for cardiac surgery in acute myocardial infarction: rat experiments with two widely used solutions

OBJECTIVES

Blood cardioplegia (BCP) can be used in different ways to protect the heart from ischaemia-reperfusion injury during cardiac surgery. Because there could be differences between warm and cold intermittent cardioplegia with or without warm reperfusion, we investigated the influence of 2 blood cardioplegia solutions on cardiac function, metabolism and infarct size in stable and infarcted rat hearts.

METHODS

The hearts of 32 male Wistar rats were excised and inserted into a blood-perfused isolated heart apparatus. In 16 hearts, an acute myocardial infarction was induced by ligation of the left anterior descending coronary artery at least 30 min before aortic clamping. After aortic clamping, either Calafiore or Buckberg BCP was administered. During reperfusion, coronary blood flow, left ventricular developed pressure and dp/dt max were recorded, and oxygen consumption and lactate production were determined. The infarct size after 90 min of reperfusion was measured by triphenyl tetrazolium chloride staining. The hearts of rats without infarction were investigated using transmission electron microscopy.

RESULTS

In hearts without infarction, haemodynamic recovery was similar for Calafiore and Buckberg solutions: left ventricular developed pressure [Cala 62% of baseline (BL), Buck 58% BL] and dp/dt max (Cala 83% BL, Buck 89% BL). Coronary flow, which was slightly less in infarcted hearts, also recovered similarly after the administration of the 2 BCP solutions (Cala 65% BL, Buck 68% BL). During reperfusion, lactate production was similar (Cala 0.85 ml/min, Buck 1.0 ml/min), and the cellular oedema index and mitochondrial swelling were comparable between the 2 groups. In hearts with infarction, left ventricular developed pressure (Cala 58% BL, Buck 56% BL) and dp/dt max (Cala 79% BL, Buck 72% BL) showed similar recovery for reperfusion with Calafiore or Buckberg BCP. In addition, coronary flow recovered similarly (Cala 54% BL, Buck 57% BL). During reperfusion, myocardial oxygen consumption was lower in the Cala (67% BL) than in the Buck (82% BL) group, but lactate production was similar between the Cala (1.1 ml/min) and the Buck (1.1 ml/min) groups. Myocardial infarct size was also similar in the Cala group (24%) and in the Buck group (26%).

CONCLUSIONS

In stable perfused rat hearts and in an in vitro model of acute myocardial infarction, the 2 BCP solutions offer equally good myocardial protection.

[Cardioprotection in cardiac surgical patients : Everything good comes from the heart]

BACKGROUND

Despite substantial success in the anesthetic and surgical management of cardiac surgery, patients frequently show postoperative complications and organ dysfunctions. This is highly relevant for mid- to long-term outcomes.

OBJECTIVES

To evaluate cardioprotective strategies that may offer effective protection in vulnerable cardiac surgery patients.

METHODS

To demonstrate recent cardioprotective approaches for cardiac surgery patients, aiming to modulate the body's own protective mechanisms in cardiac surgery patients.

RESULTS

Both cardioplegia and hypothermia belong to the well-established protective strategies during myocardial ischemia. Volatile anesthetics have been repeatedly shown to improve the left ventricular function and reduce the extent of myocardial injury compared to a control group with intravenous anesthesia. Furthermore, patients receiving volatile anesthetics showed a significantly shortened stay in the ICU and in hospital after cardiac surgery. In contrast, numerous other protective strategies failed translation into the clinical practice. Despite the published reduction of troponin release after remote ischemic preconditioning, two recent large-scale randomized multicenter trials were unable to demonstrate a clinical benefit.

CONCLUSIONS

Beside the use of cardioplegia and hypothermia, the use of volatile anesthetics is well-established during cardiac surgery because of its conditioning and protective properties. Regardless of the promising results derived from experimental studies and small clinical trials, the majority of other approaches failed to translate their findings into the clinic. Therefore, systematic experimental studies are needed to identify potential confounding factors that may affect the protective effects.