ISCHEMIC PRECONDITIONING AND POSTCONDITIONING IN CARDIOVASCULAR SURGERY

Abstract

Despite the technical improvements in the procedures of cardiovascular surgery; significant morbidity and mortality still continue in the patients undergoing cardiovascular surgery, especially in the high risk ones. Models of “conditioning” are suggested and evaluated as preserving the heart itself against ischemia - reperfusion injury which is an important cause of miyocardial injury created by the mentioned surgery and these models have been used in lots of experimental / clinical studies. In the mechanism of ischemic preconditioning; various systemic, chemical, physical stimuli, the substances affecting on the paired receptors of G - protein, proinflammatory substances, changes in the oxygen tension and various hypotheses were suggested such as protein kinase activation and activation of miyocardial potassium-ATP (KATP) channels. Lots of affirmative cardiovascular inteventions such as coronary artery bypass surgery, cardiac valve replacement, transplantation in vivo and vitro have been reported to benefit from the miyocardial preservation effect of ischemic preconditioning. Postconditioning have been widely used in various experimental / clinical studies such as acute miyocardial infarction, ventricular defibrillation, repair of tetralogy of Fallot and transplantation. Despite the fact that these “conditioning” phenomenons are promising, the demand for larger, multicenter, randomised, placebo - controlled experimental / clinical studies in this subject is increasing day by day.

Key words: Cardiovascular surgical procedure; conditioning; ischemic preconditioning; postconditioning; ischemia; reperfusion.

Özet

Kardiyovasküler cerrahi prosedürlerinde teknik ilerlemelere rağmen, hala kardiyovasküler cerrahiye giden - özellikle yüksek riskli – hastalarda, belirgin morbidite ve mortalite süregelmektedir. Anılan cerrahinin yarattığı miyokard hasarının ileri gelen nedeni olan iskemi – reperfüzyon hasarına karşı kalbin kendini koruması olarak bakılan “koşullanma” modelleri öne sürülmüş ve deneysel / klinik birçok çalışmada kullanılmıştır. İskemik önkoşullanmanın mekanizmasında; çok miktarda sistemik, kimyasal, fiziksel uyaran, G - proteinin çiftleşmiş reseptörleri üzerine etki eden maddeler, proinflamatuvar maddeler, oksijen tansiyonundaki değişimler ile birlikte protein kinaz aktivasyonu ve miyokardiyal potasyum - ATP (KATP) kanal aktivasyonu gibi daha birçok hipotez ileri sürülmüştür. İskemik önkoşullanmanın miyokard koruyuculuğu eylemi ile ilgili in vivo ve in vitro olmak üzere koroner arter “bypass” cerrahisi, kalp kapak replasmanı, transplantasyon gibi birçok olumlu kardiyovasküler cerrahi girişim raporlanmıştır. Sonradan koşullanma ise akut miyokard infarktüsü, ventriküler defibrilasyon, Fallot tetralojisi onarımı ve transplantasyon gibi alanlardaki deneysel / klinik birçok çalışmada geniş kullanım alanı bulmuştur. Bununla birlikte; bu “koşullanma” fenomenleri umut verici olsa da daha geniş, çok merkezli, randomize, placebo - kontrollü, deneysel ve klinik çalışmalara gereksinim gün geçtikçe artmaktadır.

Anahtar sözcükler: Kardiyovasküler cerrahi prosedür; koşullanma; iskemik önkoşullanma; sonradan koşullanma; iskemi; reperfüzyon.

Although the technical developments in the procedures of cardiovascular surgery; significant morbidity and mortality stil continue in the patients undergoing cardiovascular surgery, especially in the high risk ones. Models of “conditioning” are suggested and evaluated as preserving the heart itself against ischemia – reperfusion injury which is an important cause of miyocardial injury is created by the mentioned surgery and they are used in lots of experimental / clinical study. In the mechanism of ischemic preconditioning; lots of systemic, chemical, physical stimulus, the substances affecting on the paired receptors of G – protein, proinflammatuar substances, changings in the tension of oxygen with the plenty of hypothesis such, protein kinase activation and activation of miyocardial potassium – ATP (K_ATP) channels are asserted. Lots of affirmative cardiovascular intevention such coronary artery bypass surgery, cardiac valve replacement, transplantation in vivo and vitro has been reported are related to act of miyocard preservation of ischemic preconditioning. Postconditioning have the area of usages in the lots of experimental / clinical study such, acute miyocardial infarction, ventricular defibrillation, repair of tetralogy of Fallot and transplantation. However, these “conditioning” phenomenons are hopeful, though the demand of larger, multidicipliner, randomised, placebo –  controlled experimental / clinical study is increasing day by day.