Myocardial Protection in Mitral Valve Surgery: Comparison Between Minimally Invasive Approach and Standard Sternotomy.

OBJECTIVE: To compare antegrade and retrograde cardioplegia administration in minimally invasive mitral valve surgery (MIMS) and open mitral valve surgery (OMS) for myocardial protection. DESIGN: Retrospective study. SETTING: Tertiary care university hospital. PARTICIPANTS: The study comprised 118 patients undergoing MIMS and 118 patients undergoing OMS. INTERVENTIONS: The data of patients admitted for MIMS from 2006 to 2010 were reviewed. Patients undergoing isolated elective OMS from 2004 to 2006 were used as a control group. Cardioplegia in the MIMS group was delivered via the distal port of the endoaortic clamp and an endovascular coronary sinus catheter positioned using echographic and fluoroscopic guidance. Antegrade and retrograde cardioplegia were used in OMS. Data regarding myocardial infarction (MI) (creatine kinase [CK]-MB, troponin T, electrocardiography); myocardial function; and hemodynamic stability were collected. MEASUREMENTS AND MAIN RESULTS: There was no difference in the perioperative MI incidence between both groups (1 in each group, p = 0.96). No statistically significant difference was found for maximal CK-MB (35.9 µg/L [25.1-50.1] v 37.9 µg/L [28.6-50.9]; p = 0.31) or the number of patients with CK-MB levels >50 µg/L (29 v 33; p = 0.55) or CK-MB >100 µg/L (3 v 4; p = 0.70) between the OMS and MIMS groups. However, maximum troponin T levels in the MIMS group were significantly lower (0.47 µg/L [0.32-0.79] v 0.65 µg/L [0.45-0.94]; p = 0.0007). No difference in the incidence of difficult weaning from bypass and intra-aortic balloon pump use between the MIMS and OMS groups was found. CONCLUSIONS: Antegrade and retrograde cardioplegia administration during MIMS and OMS provided comparable myocardial protection.

Novel cardioprotection strategies for the aged heart: evidence from pre-clinical studies.

The incidence of cardiovascular disease is rising as the population ages. This has led to an increase in the need to perform cardiac surgery in older patients. However, aged hearts are particularly susceptible to reperfusion injury following periods of myocardial ischaemia that occur during cardiac surgery. Indeed, older adults experience myocardial dysfunction and reduced survival post-surgery compared to younger people and certain groups, including older women and frail older adults, are at particular risk. This highlights the need to design cardioprotective strategies specifically for the ageing heart. Cardioprotection during surgery is often accomplished by perfusing the heart with chemical arresting agents, known as cardioplegic solutions. New protective strategies have been developed and tested in animal models, where cardioplegic solutions have been modified by changing their temperature, chemical components and/or the frequency of delivery. In addition, drugs designed to activate cardioprotective mechanisms or to inhibit mechanisms involved in injury have been added to improve the efficacy of these solutions. However, most experimental studies have developed and optimized cardioplegic solutions in hearts from younger male animals. This review discusses pre-clinical models used to optimize cardioplegic solutions, with an emphasis on the few studies that have used hearts from older animals. Pharmacologic agents that have been shown to enhance the benefits of cardioplegia in younger hearts and could, in theory, protect vulnerable older hearts are also considered. We emphasize the need to conduct studies in frail older animals of both sexes to facilitate translation of laboratory-based observations to the clinic.

del Nido cardioplegia in adult cardiac surgery - scopes and concerns.

The convenience offered by a single-dose cardioplegia strategy is the avoidance of interruption of the flow of surgery and, more importantly, a significant reduction in the cross-clamp time. del Nido cardioplegia is an extracellular cardioplegic solution which serves these purposes and has been used successfully in pediatric cardiac surgery. The subsequent extrapolation of its use in adult cardiac surgery has returned encouraging results, as evidenced by recent literature. The use of del Nido cardioplegia in adults has been reported to shorten the cross-clamp time, cardiopulmonary bypass time and overall operating time. Intraoperative peak glucose value and insulin requirement have also been reported to be lower with del Nido cardioplegia, which can have prognostic significance. There have been reports of lesser incidence of atrial fibrillation and the number of defibrillations required with use of this technique. However, some unique concerns still remain. The lack of prospective randomized trials, the trend of elevation in CKMB (as reported by one study) and the need for a protocol-based approach to its use in adults are to be given due consideration while adopting its use in adults. This review attempts to have an overview on del Nido cardioplegia, its advantages, the recent studies comparing it with conventional cardioplegia techniques and the potential areas of concern with its use in adult cardiac surgery.

Esmolol added in repeated, cold, oxygenated blood cardioplegia improves myocardial function after cardiopulmonary bypass.

OBJECTIVE: This study investigated if the ß-receptor blocking agent esmolol, added to standard oxygenated blood cardioplegia, improved myocardial function after weaning from bypass. DESIGN: A block-randomized, blinded study. SETTING: A university laboratory. PARTICIPANTS: Twenty anesthetized pigs, Norwegian Landrace. INTERVENTIONS: After cardiopulmonary bypass, cardiac arrest was induced with cold (12°C), oxygenated blood cardioplegia, enriched with either esmolol or vehicle, repeated every 20 minutes. After 100 minutes the heart was reperfused and weaned. MEASUREMENTS AND MAIN RESULTS: Left ventricular function was evaluated with pressure-volume loops, local myocardial function with multilayer strain and strain rate by epicardial short-axis tissue Doppler imaging. One hour after declamping, preload recruitable stroke work did not differ between groups, but increased to 72±3 mmHg in esmolol-treated animals v 57±4 mmHg (p<0.001) in controls after 3 hours. Radial peak ejection strain rate also was increased by esmolol; 6.0±1.0 s(-1)v 2.9±0.3 s(-1) (p<0.001) in subendocardium and 3.9±0.5 s(-1)v 2.3±0.2 s(-1) (p<0.005) in the midmyocardium. Cardiac index was increased, 4.0±0.2 L/min/m(2) by esmolol v 3.3±0.1 L/min/m(2) for controls (p<0.05). Isovolumetric relaxation time constant was reduced by esmolol, 23±1 ms v 26±1 ms (p<0.025). Troponin-T did not differ and was 339±48 ng/L for the esmolol group and 357±55 ng/L for the control group (p = 0.81). CONCLUSIONS: Esmolol added to blood cardioplegia preserved systolic cardiac function during the first 3 hours after reperfusion in a porcine model with 100 minutes of cardioplegic arrest.

Future perspective of cardioplegic protection in cardiac surgery.

"Depolarized arrest", induced by hyperkalemic (moderately increased extracellular potassium) cardioplegia is the gold standard to achieve elective temporary cardiac arrest in cardiac surgery. Hyperkalemic cardioplegic solutions provide good myocardial protection, which is relatively safe and easily and rapidly reversible. However, this technique has detrimental effects associated with ionic imbalance involving sodium and calcium overload of the cardiac cell induced by depolarization of the cell membrane. Hence, the development of an improved cardioplegic solution that enhances myocardial protection would be expected as an alternative to hyperkalemic cardioplegia. In this review, we assess the potential disadvantages of "depolarized arrest" and the suitability and clinical potential of "non-depolarized arrest". "Magnesium cardioplegia" and "esmolol cardioplegia" has been shown to exert superior protection with comparable safety profiles to that of hyperkalemic cardioplegia. These alternative techniques require further examination and investigation to challenge the traditional view that hyperkalemic arrest is best. Endogenous cardioprotective strategies, termed "ischemic preconditioning" and "ischemic postconditioning", may have a role in cardiac surgery to provide additional protection. The elective nature of cardiac surgery, with the known onset of ischemia and reperfusion, lends it to the potential of these strategies. However, the benefit of preconditioning and postconditioning during cardiac surgery is controversial, particularly in the context of cardioplegia. The clinical application of these strategies is unlikely to become routine during cardiac surgery because of the necessity for repeated aortic crossclamping with consequent potential for embolic events, but offers considerable potential especially if "pharmacological" preconditioning and postconditioning could be established.

Solução cardioplégica polarizante: estado da arte / Polarizing cardioplegic solution: state of the art

A exegese do termo cardioplegia remete aos significados de lesão, golpe, ataque ou ferimento, bem diferente, portanto, do sentido em que o termo é empregado na maior parte dos centros de cirurgia cardíaca do Brasil e do mundo, ou seja, como correspondendo à proteção miocárdica. Daí a melhor denominação de solução cardioplégica, para caracterizar as soluções empregadas com finalidade de promover a parada cardíaca controlada do coração. A parada cardíaca induzida por solução cardioplégica pode acontecer por hiperpolarização, despolarização ou com bloqueadores da bomba de cálcio. No presente trabalho, discorreremos sobre os principais agentes que promovem a parada cardíaca por hiperpolarização da membrana miocárdica. Com a solução hiperpolarizante, o coração pára no perído diastólico, havendo uma redução ainda maior no seu gasto energético, o que propicia melhores condições ao coração quando este reinicia sua contração ao final do procedimento cirúrgico

Suspended animation for resuscitation from exsanguinating hemorrhage.

In dogs, isotonic saline at 0-4 degrees C, flushed into the aorta at a rate of 1-2 L/min, with drainage of the vena cava, can achieve deep to profound hypothermia of vital organs at a cooling rate of up to 3 degrees C per minute. This achieves preservation of viability of the organism during predictable durations of no flow: cardiac arrest of 15-20 mins at Tty of 30-35 degrees C, cardiac arrest of 30 mins at Tty of 25 degrees C, cardiac arrest of 60 mins at Tty of 15 degrees C, and cardiac arrest of 90 mins at Tty of 10 degrees C. So far, pharmacologic approaches have not resulted in any breakthrough effect on outcome above that achieved with hypothermia, except perhaps the antioxidant tempol. Additional studies of novel drugs and, perhaps, combination therapies remain warranted. The optimal fluids to have in the circulation during circulatory arrest and reperfusions need to be determined. As laboratory studies to optimize suspended animation proceed, clinical trials should be initiated. In addition, devices should be developed to facilitate induction of suspended animation, eventually in the field.

Myocardial protection in adult cardiac surgery: current options and future challenges.

Current techniques of myocardial protection are evolving with the use of less conventional modalities of cardioplegia and have reduced the morbidity and mortality of cardiac operations. Blood cardioplegic solutions appear superior to cold cardioplegia in terms of myocardial protection and adjuncts as glutamate/aspartate enhancement, antioxidant supplementation, nitric oxide donors and maintenance of calcium homeostasis seem effective. In the near future, further experimental and clinical investigations about pharmacological preconditioning, sodium-hydrogen exchangers inhibition and gene therapy need to be addressed to well define their potential role in the improvement of current techniques of myocardial protection that are suboptimal in high-risk clinical settings.

Myocardial protection: entering the new millennium.

Dual objectives at operation are technical success and absence of iatrogenic injury due to inadequate myocardial protection. We enter a new millennium, and the spectrum of surgical procedures used to correct abnormal structure is expanding. We need longer intervals of aortic clamping to make the correct diagnosis, and to implement a more natural correction (i.e., mitral valve repair, Ross procedure, aortic recontruction with stentless valves, homografts). Simultaneously, our patients have increased vulnerability to injury, so that growth is needed to advance our methods of protection, in the same way as we learn new operative techniques. This manuscript deals both with evolution of current methods and recognition of newer methods of protection, so that the dual relationship between protection and procedures will not separate.

Myocardial protection for coronary bypass grafting: the Toronto Hospital perspective.

BACKGROUND: The contemporary results of coronary artery bypass grafting using a variety of myocardial preservation techniques are excellent. In recent years, the number of "high-risk" patients referred for operation has increased, thus necessitating continued advances in surgical myocardial protection. METHODS: In this article, we review recent advances in clinical myocardial protective techniques and emphasize studies conducted at The Toronto Hospital. Further, on the basis of promising current research, we speculate on future prospects for myocardial protection. RESULTS: At The Toronto Hospital, we converted from crystalloid to intermittent cold blood cardioplegia in 1985. We demonstrated that "continuous" cardioplegic strategies may help resuscitate the ischemic myocardium and reduce operative complications in high-risk patients. Further improvements in myocardial protection will require refinements in cardioplegic solution temperature, direction of delivery, and additives to "precondition" the myocardium against ischemic damage. CONCLUSIONS: Major advances that meet the requirements of an increasingly high risk patient population have been made in surgical myocardial protection in recent years. The future is bright for continued progress in this area.

Warm heart surgery: concept, concerns, and future course.

Hypothermia has been considered a prerequisite for decreasing oxygen consumption and providing myocardial protection. The decrease in myocardial oxygen consumption however, is more closely related to the state of electromechanical arrest than to hypothermia. The rationale for warm blood cardioplegia is based not only on electromechanical quiescence but equally on facilitation of O2 delivery. This report outlines the basis for the concepts, the various concerns and the possible future directions of warm blood cardioplegia.

Perspectives on myocardial protection: warm heart surgery.

Continuous normothermic blood cardioplegia (CNBC), was recently introduced into clinical cardiac surgery and has generated great interest. CNBC represents the evolution of concepts which were initially described in the 1950s but which were forgotten as hypothermia became the main ingredient in all cardioplegic techniques and in heart surgery in general. The historical background to the development of CNBC is presented, as well as a review of the current state of knowledge about normothermic heart surgery. The limitations and pitfalls of the method are highlighted, along with future developments and perspectives.

[Myocardial protection: the current status and the future prospect].

Perioperative myocardial damage remains the most common cause of morbidity and death following technically successful cardiac operations. Such damage is caused by an imbalance between myocardial energy demand and supply occurring before, during, and after extracorporeal circulation. Meanwhile, since the advent of cardiac surgery, improved methods have been studied to provide a safe, quiet, and bloodless operative field. In recent years, much effort has been devoted to experimental and clinical research to improve myocardial protection during open heart surgery. With understanding on the pathophysiology of ischemic myocardium and reperfusion injury etc. significant advances have been made in myocardial protection during open heart operation, which has allowed a significant reduction in perioperative myocardial injury. In this article, recent developments in myocardial protection and currently accepted clinical techniques have been presented. Furthermore, it has been discussed to concentrate on current topics of controversy and new investigations in this field. Although some cardiac surgeons would argue that very little advanced new information is available in myocardial protection during open heart operation, my opinion is "no". Still now, there are many remained, important problems, such as 1) protective method of immature neonatal myocardium 2) effective substrates to facilitate high energy resumption, and specific scavengers to modify oxygen free radical during reperfusion, and so on. We should expect and await further experimental and clinical trials.

[Current aspects of surgery of congenital heart defects]. / Heutige Aspekte der Chirurgie angeborener Herzfehler.

A review is given concerning the development of surgery for the congenital heart in recent years, or decades, respectively. Longterm results of operative and conservative treatment should be critically considered to avoid unsuccessful operations. Data from West Germany show that this type of surgery should not be done in all places where cardiac surgery is performed.

Recent advances in cardiopulmonary bypass and the clinical application of myocardial protection.

Basic scientific research has provided the impetus to develop cardioplegic solutions that offer excellent myocardial preservation. Future research will continue to develop methods for better delivery of cardioplegia to all myocardial regions. In addition, earlier detection of evolving ischemic damage during aortic cross-clamping might provide a basis for earlier intervention to reverse developing myocardial injury. At the present time, the cardiac surgeon has many cardioplegic solutions and delivery systems from which to choose. Only by understanding the principles involved in myocardial preservation will the surgeon be able to develop a system that will work best in his or her clinical practice.