Adenosine instead of supranormal potassium in cardioplegic solution improves cardioprotection

Novel Strategies to Improve the Cardioprotective Effects of Cardioplegia

The use of cardioprotective strategies as adjuvants of cardioplegic solutions has become an ideal alternative for the improvement of post-surgery heart recovery. The choice of the optimal cardioplegia, as well as its distribution mechanism, remains controversial in the field of cardiovascular surgery. There is still a need to search for new and better cardioprotective methods during cardioplegic procedures. New techniques for the management of cardiovascular complications during cardioplegia have evolved with new alternatives and additives, and each new strategy provides a tool to neutralize the damage after ischemia/reperfusion events. Researchers and clinicians have committed themselves to studying the effect of new strategies and adjuvant components with the potential to improve the cardioprotective effect of cardioplegic solutions in preventing myocardial ischemia/reperfusion-induced injury during cardiac surgery. The aim of this review is to explore the different types of cardioplegia, their protection mechanisms, and which strategies have been proposed to enhance the function of these solutions in hearts exposed to cardiovascular pathologies that require surgical alternatives for their corrective progression.

Cardioplegia between Evolution and Revolution: From Depolarized to Polarized Cardiac Arrest in Adult Cardiac Surgery

Despite current advances in perioperative care, intraoperative myocardial protection during cardiac surgery has not kept the same pace. High potassium cardioplegic solutions were introduced in the 1950s, and in the early 1960s they were soon recognized as harmful. Since that time, surgeons have minimized many of the adverse effects by lowering the temperature of the heart, lowering K⁺ concentration, reducing contact K⁺ time, changing the vehicle from a crystalloid solution to whole-blood, adding many pharmacological protectants and modifying reperfusion conditions. Despite these attempts, high potassium remains a suboptimalway to arrest the heart. We briefly review the historical advances and failures of finding alternatives to high potassium, the drawbacks of a prolonged depolarized membrane, altered Ca²⁺ intracellular circuits and heterogeneity in atrial-ventricular K⁺ repolarization during reanimation. Many of these untoward effects may be alleviated by a polarized membrane, and we will discuss the basic science and clinical experience from a number of institutions trialling different alternatives, and our institution with a non-depolarizing adenosine, lidocaine and magnesium (ALM) cardioplegia. The future of polarized arrest is an exciting one and may play an important role in treating the next generation of patients who are older, and sicker with multiple comorbidities and require more complex operations with prolonged cross-clamping times.

Relevance and Recommendations for the Application of Cardioplegic Solutions in Cardiopulmonary Bypass Surgery in Pigs

Cardioplegic solutions play a major role in cardiac surgery due to the fact that they create a silent operating field and protect the myocardium against ischemia and reperfusion injury. For studies on cardioplegic solutions, it is important to compare their effects and to have a valid platform for preclinical testing of new cardioplegic solutions and their additives. Due to the strong anatomical and physiological cardiovascular similarities between pigs and humans, porcine models are suitable for investigating the effects of cardioplegic solutions. This review provides an overview of the results of the application of cardioplegic solutions in adult or pediatric pig models over the past 25 years. The advantages, disadvantages, limitations, and refinement strategies of these models are discussed.

Hyperkalemic cardioplegia for adult and pediatric surgery: end of an era?

Despite surgical proficiency and innovation driving low mortality rates in cardiac surgery, the disease severity, comorbidity rate, and operative procedural difficulty have increased. Today's cardiac surgery patient is older, has a "sicker" heart and often presents with multiple comorbidities; a scenario that was relatively rare 20 years ago. The global challenge has been to find new ways to make surgery safer for the patient and more predictable for the surgeon. A confounding factor that may influence clinical outcome is high K(+) cardioplegia. For over 40 years, potassium depolarization has been linked to transmembrane ionic imbalances, arrhythmias and conduction disturbances, vasoconstriction, coronary spasm, contractile stunning, and low output syndrome. Other than inducing rapid electrochemical arrest, high K(+) cardioplegia offers little or no inherent protection to adult or pediatric patients. This review provides a brief history of high K(+) cardioplegia, five areas of increasing concern with prolonged membrane K(+) depolarization, and the basic science and clinical data underpinning a new normokalemic, "polarizing" cardioplegia comprising adenosine and lidocaine (AL) with magnesium (Mg(2+)) (ALM™). We argue that improved cardioprotection, better outcomes, faster recoveries and lower healthcare costs are achievable and, despite the early predictions from the stent industry and cardiology, the "cath lab" may not be the place where the new wave of high-risk morbid patients are best served.

Adenosine instead of supranormal potassium in cardioplegia: it is safe, efficient, and reduces the incidence of postoperative atrial fibrillation. A randomized clinical trial

OBJECTIVE

We aimed to evaluate the efficacy and safety of a cold crystalloid cardioplegic solution with adenosine (1.2 mmol/L) instead of supranormal potassium.

METHODS

Sixty low-risk patients scheduled for elective coronary artery bypass grafting (CABG) were randomized to receive standard cold crystalloid hyperkalemic cardioplegia (hyperkalemic group) or normokalemic cardioplegia in which supranormal potassium was replaced with 1.2 mmol/L adenosine (adenosine group). End points were postoperative release of troponin T and creatine kinase MB, hemodynamics measured by PiCCO arterial thermodilution catheters, perioperative release of markers of endothelial activation and injury, and clinical course.

RESULTS

The adenosine group had a significantly shorter time to arrest than did the hyperkalemic group (mean ± standard deviation, 11 ± 5 vs 44 ± 18 seconds; P < .001). Three hearts in the adenosine group were probably not adequately drained and received additional hyperkalemic cardioplegia to maintain satisfactory cardioplegic arrest. There were no differences between groups with respect to perioperative release of markers of endothelial activation or injury and no differences between groups in postoperative release of troponin T or creatine kinase MB. Postoperative hemodynamics including cardiac index were similar between groups. The incidence of postoperative atrial fibrillation was significantly lower in the adenosine group than in the hyperkalemic group (4 vs 15; P = .01).

CONCLUSIONS

Adenosine instead of hyperkalemia in cold crystalloid cardioplegia is safe, gives more rapid cardiac arrest, and affords similar cardioprotection and maintenance of hemodynamic parameters, together with a marked reduction in the incidence of postoperative atrial fibrillation.

Cardioprotective effect of 3-iodothyronamine in perfused rat heart subjected to ischemia and reperfusion

3-iodothyronamine (T(1)AM) is an endogenous compound which shares structural and functional features with biogenic amines and is able to interact with a specific class of receptors, designed as trace amine associated receptors. T(1)AM has significant physiological effects in mammals and produces a reversible, dose-dependent negative inotropic and chronotropic effect in heart. The aim of the present study was to investigate if T(1)AM is able to reduce irreversible tissue injury in isolated rat hearts subjected to ischemia and reperfusion, as evaluated by triphenyltetrazolium chloride staining. We observed that T(1)AM reduced infarct size at concentrations (125 nM to 12.5 μM) which did not produce any significant hemodynamic action. The dose-response curve was bell-shaped and peaked at 1.25 μM. T(1)AM-induced cardioprotection was completely reversed by the administration of chelerythrine and glibenclamide, suggesting a protein kinase C and K (ATP) (+) -dependent pathway, while it was not additive to the protection induced by cyclosporine A, suggesting modulation of mitochondrial permeability transition. At cardioprotective concentration, T(1)AM reduced the time needed for cardiac attest during ischemia, but it did not affect sarcoplasmatic reticulum Ca(2+) handling, as demonstrated by unaltered ryanodine receptor binding properties. In conclusion, in isolated rat heart T(1)AM produces a cardioprotective effect which is mediated by a protein kinase C and K (ATP) (+) -dependent pathway and is probably linked to modulation of mitochondrial permeability transition and/or ischemic arrest time.

The myocardial protection of polarizing cardioplegia combined with delta-opioid receptor agonist in swine

BACKGROUND

The purpose of this study was to determine whether polarized arrest using adenosine/lidocaine cold crystalloid cardioplegia in combination with the hibernation inductor δ-opioid receptor agonist pentazocine would give satisfactory myocardial protection rather than using depolarized supranormal potassium cardioplegia, supranormal potassium cardioplegia with pentazocine, or adenosine/lidocaine cardioplegia.

METHODS

Twenty pigs were randomly divided into four groups (n=5 each) to receive the four types of cold crystalloid cardioplegia with an aortic cross-clamp time of 1 hour. Hemodynamic data were continuously measured, as was the left ventricular end-diastolic pressure (LVEDP), left ventricular end-systolic pressure (LVESP), plus or minus derivative of change in diastolic pressure over time (±dp/dt), cardiac output, pulmonary artery pressure, pulmonary capillary wedge pressure, cardiac troponin I, and left ventricular ultrastructure.

RESULTS

Both the adenosine/lidocaine/pentazocine group and the adenosine/lidocaine group got significantly better results than the hyperkalemic and hyperkalemic pentazocine groups in improving hemodynamic values, pulmonary capillary wedge pressure, LVEDP, LVESP, ±dp/dt, cardiac output, cardiac troponin I values, and left ventricular ultrastructure. There were no statistical differences between the adenosine/lidocaine/pentazocine group and the adenosine/lidocaine group at 1 hour after cross-clamp removal; but at 2 hours after cross-clamp removal, the adenosine/lidocaine/pentazocine group stands out (LVEDP 3.3±0.5, LVESP 122.5±18.9, +dp/dt 2.9±0.1, -dp/dt 2.0±0.6, cardiac output 2.6±0.4, and troponin I 4.9±0.5), with significant differences from the adenosine/lidocaine group (LVEDP 5.8±1.0, LVESP 98.5±10.1, +dp/dt 2.5±0.2, -dp/dt 1.0±0.2, cardiac output 2.2±0.2, troponin I 8.2±0.8; p<0.05). The defibrillation rate was largely decreased after the cross-clamp was released in the group containing pentazocine in cardioplegia.

CONCLUSIONS

Adenosine/lidocaine/pentazocine cold crystalloid cardioplegia gave satisfactory cardiac arrest and better myocardial protection than the other three groups, especially with regard to improving prolonged postoperative cardiac function.

Targeting for cardioplegia: arresting agents and their safety

Elective temporary cardiac arrest (cardioplegia) is often required during cardiac surgery. In the 1970 s, the development of hyperkalaemic cardioplegic solutions revolutionised cardiac surgery by offering effective chemically-induced cardiac arrest and myocardial protection during global ischaemia. Despite remaining the most widely-used cardioplegic technique, hyperkalaemia can have detrimental effects due to the Na and Ca loading of the cardiac cell induced by depolarisation of the cell membrane. Efforts over the last two decades to establish better cardioplegic agents have mainly remained limited to animal experiments. The failure of these approaches to progress to clinical trials may be due to a lack of clear criteria that a cardioplegic agent should meet at a cellular level and, more importantly, at a system level. In this review we attempt to define the criteria for the optimal cardioplegic agent. We also assess the suitability and clinical potential of previously-studied cardioplegic agents and suggest cellular targets, particularly those involved in cardiac excitation-contraction coupling, that may prove to be attractive options for the development of new cardioplegic drugs. Finally, we propose a multicellular target approach using a combination of pharmacological agents in order to offer better cardioplegic solutions.