www.ksmf.org/arhimed   arhimed@ksmf.org   [5/10/2025 2:25:28 PM] http://www.ksmf.org/arhimed/poglej.asp?id=55 Toplotna prevodnost prašicjega srcnega tkiva Avtor: Janez Rifel, David Koncan Mentor: Prof. dr. Metka V. Budihna, dr. med Toplotna prevodnost miokarda je pomembna pri hladni kardioplegicni ustavitvi srca pri operacijah na odprtem srcu. Hlajenje uporabljamo zato, da upocasnimo metabolizem, neželjeni ucinki pri segrevanju na telesno temperaturo pa so neenakomerna segretost tkiva in zaradi tega izzvane nepravilnosti v elektricnem in mehanskem delovanju srca. V delujocem srcu se toplota širi prek konvekcije s krvjo, ki tece skozi vencne arterije in krvjo, ki jo srce precrpa skozi srcne votline. V ustavljenem srcu je ohlajanje in segrevanje srca odvisno od toplotne prevodnosti srcnega tkiva in od temperaturnih razlik snovi, ki ustavljeno srce obdajajo. Ob ponovni vzpostavitvi telesnega krvnega obtoka nastanejo zaradi neenakomernega segrevanja temperaturne razlike med stenami prekatov, medprekatnim pretinom in manj ožiljenimi deli srca. V pricujoci nalogi sva želela izmeriti toplotno prevodnost srcnega tkiva prašica. Iz predela medprekatnega pretina in prekatne stene sva izrezala kose tkiva cimbolj pravilne kvadrne oblike. Primerjala sva prevodnost vzorcev, ki so vkljucevali epikard in površinsko mašcevje z vzorci brez mašcevja in brez epikarda. Za merjenje prevodnosti sva uporabila merilni model s planparalelno plošco in cilindricni model s sredinsko namešceno NTC sondo (sondo z negativnim temperaturnim koeficientom). Bolj zanesljive rezultate sva dobila z metodo planparalelne plošce. Vrednost koeficienta toplotne prevodnosti za tkivo brez mašcevja, dobljene s to metodo, znaša 0,75 ± 0,03 W/mK, za tkivo z epikardom in mašcevjem pa 0,60 ± 0,01 W/mK (p<0,01). Rezultati so uporabni za izdelavo racunalniškega modela za simulacijo temperaturnih dogajanj ob srcnih operacijah «» [Abstract / English version] Thermal conductivity of porcine heart tissue Author: Janez Rifel, David Koncan Mentor: Prof. dr. Metka V. Budihna, dr. med The thermal conductivity of myocardium is important in the cold cardioplegic arrest of the heart during open heart surgery. The cooling is used to slow down the metabolism. By rewarming the heart muscle takes up the heat irregularly, which, in turn, interferes with heart's electrical and mechanical work. In working heart in the body the main source of the thermal flow is obtained through the coronary arteries and by blood flow pumped through the heart cavities by convenction. In the arrested heart cooling and heating depends on thermal conductivity of the cardiac tissues and on the temperature gradient between heart and the biomaterials which surround it. At the restoration of the blood flow, the heating of the heart is uneven. This causes temperature differences between the ventricular and atrial walls, septum, and less vascularized part of the myocardium. In the present work we wished to measure the thermal conductivity of the porcine heart tissue. From the interventricular septum pieces of tissue in the form of rectangular or cylindrical blocks were excised in as much as possible regular shape. We compared the thermal conductivity of the specimens with epicardium and superficial fat tissue and the conductivity of specimens without epicardium and fat tissue. For measurement the planparallel plate model or the cylindrical model with centrally placed NTC probe (Negative temperature gradient probe) were used. The value of thermal conductivity coefficient for the heart tissue without fat obtained with the method of planparallel plate was 0.75 ± 0.03 W/mK, and for the heart tissue with epicardium and fat was 0.60 ± 0.01 W/mK (p<0.01). With cylindrical model results were more dispersed. Our results can be used for computer simulation of temperature changes in myocardium in cardiac surgery.