María Teresa Politi1, Federico Ochoa1, Vanina Netti1, Raúl Ferreyra2, Guillermo Bortman2, Norberto Sanjuan3, Celina Morales4, Antonio Piazza5, Claudia Capurro1. 1. School of Medicine, University of Buenos Aires, National Scientific and Technical Research Council, Institute of Physiology and Biophysics "Bernardo Houssay" (IFIBIO-HOUSSAY), Buenos Aires, Argentina. 2. Department of Cardiology, Sanatorio de la Trinidad-Mitre, Buenos Aires, Argentina. 3. Laboratory of Experimental Pathology, Department of Microbiology (IMPaM-CONICET), School of Medicine, University of Buenos Aires, National Scientific and Technical Research Council, Buenos Aires, Argentina. 4. School of Medicine, Facultad de Medicina, University of Buenos Aires, Institute of Cardiovascular Pathophysiology (INFICA), Buenos Aires, Argentina. 5. Department of Cardiovascular Surgery, Sanatorio de la Trinidad-Mitre, Buenos Aires, Argentina.
Abstract
OBJECTIVES: Cardiopulmonary bypass (CPB) use is an essential strategy for many cardiovascular surgeries. However, its use and duration have been associated with a higher rate of postoperative complications, such as low cardiac output syndrome due to myocardial oedema and dysfunction. Though Aquaporin water channels have been implicated in myocardial water balance, their specific role in this clinical scenario has not been established. METHODS: In a consecutive study of 17 patients with severe aortic stenosis undergoing aortic valve replacement surgery, 2 myocardial biopsies of the left ventricle were taken: 1 before and 1 after CPB use. Sociodemographic, clinical and laboratory data were collected. Western blot and immunohistochemistry studies were performed. RESULTS: After CPB use, there was a mean increase of ∼62% in Aquaporin 1 protein levels (P = 0.001) and a mean reduction of ∼38% in Aquaporin 4 protein levels (P = 0.030). In immunohistochemistry assays, Aquaporin 1 was found lining small blood vessels, while Aquaporin 4 formed a circular label in cardiomyocytes. There were no changes in the localization of either protein following CPB use. During the observed on-pump time interval, there was a 1.7%/min mean increase in Aquaporin 1 (P = 0.021) and a 2.5%/min mean decrease in Aquaporin 4 (P = 0.018). Myocardial interstitial oedema increased by 42% (95% confidence interval 31-54%) after CPB use. Patients who developed low cardiac output syndrome were in the upper half of the median percentage change of Aquaporin expression. CONCLUSION: Time-dependent changes in cardiac Aquaporin expression may be associated with myocardial oedema and dysfunction related to CPB use.
OBJECTIVES: Cardiopulmonary bypass (CPB) use is an essential strategy for many cardiovascular surgeries. However, its use and duration have been associated with a higher rate of postoperative complications, such as low cardiac output syndrome due to myocardial oedema and dysfunction. Though Aquaporin water channels have been implicated in myocardial water balance, their specific role in this clinical scenario has not been established. METHODS: In a consecutive study of 17 patients with severe aortic stenosis undergoing aortic valve replacement surgery, 2 myocardial biopsies of the left ventricle were taken: 1 before and 1 after CPB use. Sociodemographic, clinical and laboratory data were collected. Western blot and immunohistochemistry studies were performed. RESULTS: After CPB use, there was a mean increase of ∼62% in Aquaporin 1 protein levels (P = 0.001) and a mean reduction of ∼38% in Aquaporin 4 protein levels (P = 0.030). In immunohistochemistry assays, Aquaporin 1 was found lining small blood vessels, while Aquaporin 4 formed a circular label in cardiomyocytes. There were no changes in the localization of either protein following CPB use. During the observed on-pump time interval, there was a 1.7%/min mean increase in Aquaporin 1 (P = 0.021) and a 2.5%/min mean decrease in Aquaporin 4 (P = 0.018). Myocardial interstitial oedema increased by 42% (95% confidence interval 31-54%) after CPB use. Patients who developed low cardiac output syndrome were in the upper half of the median percentage change of Aquaporin expression. CONCLUSION: Time-dependent changes in cardiac Aquaporin expression may be associated with myocardial oedema and dysfunction related to CPB use.