Dissertation committee:
Κοτανίδου Αναστασία, Καθηγήτρια, Ιατρική Σχολή, ΕΚΠΑ
Δευτεραίος Σπυρίδων, Καθηγητής, Ιατρική Σχολή, ΕΚΠΑ
Βασιλειάδης Ιωάννης, Αναπληρώτης Καθηγητής, Ιατρική Σχολή, ΕΚΠΑ
Δημοπούλου Ιωάννα-Μαρία, Καθηγήτρια, Ιατρική Σχολή, ΕΚΠΑ
Ορφανός Στυλιανός, Καθηγητής, Ιατρική Σχολή, ΕΚΠΑ
Μπουτάτη Ελένη Αναλπηρώτρια Καθηγήτρια, Ιατρική Σχολή, ΕΚΠΑ
Φιλιππάτος Γεράσιμος, Καθηγητής, Ιατρική Σχολή, ΕΚΠΑ
Summary:
Αγγλικά ή άλλη γλώσσα:
Introduction: The intracellular calcium (Ca+2) homeostasis is impaired and this is the crucial step of ischemia-reperfusion injury. Myocardial ischemia triggers increased Ca+2 release through the sarcoplasmic reticulum (SR) leading to cytosolic Ca+2 overload, subsequently resulting in additional irreversible injury. This Ca+2 release is partially carried out through major Ca+2 release channels called ryanodine receptors (RyR2). Dantrolene sodium is a RyR2 antagonist, its clinical use has been established since 1980s for effectively dealing with malignant hyperthermia. Therefore, a hypothesis has been created that dantrolene sodium could also modify SR Ca+2 release occurring during myocardial ischemia-reperfusion as a result of heart surgery under cardiopulmonary bypass or coronary artery balloon angioplasty. There is evidence that dantrolene may also have a relevant impact on cardiac muscle.
Objective: The objective of the present study was to evaluate the in-vivo impact of dantrolene sodium on myocardial ischemia-reperfusion injury in swine models. We hypothesized that administering dantrolene at the onset of the reperfusion period could be protective against myocardial ischemia-reperfusion injury. Although previous experimental attempts have successfully been conducted in rodents, this study is the first experimental study in larger mammals whose cardiac physiology and anatomy resemble those of human hearts.
Materials and Methods: Nineteen large domestic animals of similar age and body weight were included and randomized into control and study groups. The thoracic cavity of the animals was accessed through median sternotomy under general anesthesia. The left anterior descending coronary artery (LAD) was ligated distally to the second diagonal branch via a vascular tourniquet. After 75 minutes of ischemia, the tourniquet was released (time point 0) and reperfusion for 24 hours was allowed. During this reperfusion period, all animals were left intubated and sedated having their chests open. After 24 hours of reperfusion, the LAD was re-ligated at the same point, the ascending aorta was clamped and 1 mL/kg of Evan's blue dye (2%) was injected into the coronary circulation. Subsequently, the animals were euthanatized by intracoronary overdose KCl delivery. After resection and rinsing of the heart, the right ventricle and atrium were separated and discarded. The left ventricle was cut into thin sections of about 0.5-cm length. The area at risk (aaR) of each piece was recognized by the absence of Evan blue uptake. All myocardial sections were immersed in a 0.8% triphenyl tetrazolium chloride (TTC) solution for 10 minutes at 37°C. TTC solution gave an intense reddish color to the viable myocardium, whereas not stained areas were indicative of necrotizing myocardium. Planimetry, measuring surface areas and perimeters between differently traced regions, was used to accurately determine the aaR and I areas, while the relative infarct size was expressed as a percentage of I to aaR.(I/aaR). Levels of cTnI, CK, and CKMB in animals blood were measured at 0 hours (before LAD ligation), immediately after restoring the coronary flow and every 2 hours thereafter. Various hemodynamic parameters including intraventricular pressure, cardiac output (CO), cardiac index (CI), and pulmonary artery wedge pressure (PAWP) were also recorded through a Swan Ganz catheter which was preoperatively placed through the right internal jugular vein of every experimental model.
Results: A total of 19 animals (10 in group dantrolene sodium and 9 in group NaCl) were included in the study. At ischemia and at almost all the other time points dantrolene sodium group had significantly lower values of CK and CKMB as compared to NaCl group. Significantly lower values of Troponin were recorded for the dantrolene sodium group for all time points from second hour to 24 hours. CO and PCWP were not different between the study groups at any time point, while CI was greater for dantrolene sodium group from 16 to 24 hours. Calculation and comparison of AUCg and AUCi for all study indices showed significantly lower values for dantrolene sodium group concerning CK, CKMB and Troponin. No significant differences were found for the AUCs of CO and PCWP, while AUCg for CI was greater for dantrolene sodium group. PCWP showed a significant increase during follow up, while CO and CI showed a significant decrease during follow up. The interaction of study group with time was significant for all indices except for CO, indicating that dantrolene sodium group had lower increase in CK, CKMB, Troponin and PCWP compared to NaCl group. Furthermore, a significant interaction effect of study group with time was found for CI indicating that NaCl group had greater decrease in CI as compared to dantrolene sodium group.Volume comparisons between dantrolene sodium and NaCl groupsshowed significantly lower values of Total LV volume, Total viable volume, Total viable volume outside and Viable risk area in the dantrolene sodium group.
Conclusion: In conclusion, the in vivo cardioprotective role of dantrolene sodium against ischemia-reperfusion injury in 10 swine models compared to 9 control models was shown. Significantly lower post ischemic levels of CK, CKMB and cTnI which are indicative of less ischemia-reperfusion injury were reported after dantrolene administration. Greater CI in the dantrolene group, as well as significantly lower values of total LV volume, total viable volume, total viable volume outside and viable risk area also confirmed the cardioprotective role of dantrolene sodium. Therefore, modulating intracellular Ca2+ channels can be a novel cytoprotective strategy against ischemia-reperfusion injury. However, there are only experimental animal studies proving the aforementioned.
