Heart-rate variability during gravitational transition in doxorubicin-induced cardiomyopathic Guinea pig

Abstract

Changes in gravitational force cause no serious problems in healthy persons but might induce vital disturbances in a person with cardiovascular abnormalities. To evaluate the potential of neuro-cardiogenic disruption in a heart at risk during abrupt gravitational transition, heart rate variability of doxorubicin-induced cardiomyopathic (CM) Guinea pigs were monitored during a parabolic flight. An electrocardiogram was continuously recorded during the change from normal gravity to 1.8g (hypergravity) and then to 0g (microgravity). Time domain heart rate variability indices, including standard deviation of intervals (RRSD) and the square root of mean squared differences of successive intervals (rMSSD), corrected QT interval (QTc), and short-term QT variability (STVQT) were compared. At normal gravity, decreases in RRSD and rMSSD with prolonged QTc interval were observed in the CM group compared to controls. Further significant reduction of RRSD was seen only in CM group during hypergravity, while a decrease in rMSSD was only found in the control group, indicating an increase in arrhythmic risk. A significant increase in STVQT was present only in the control group in microgravity, suggesting a possibility of decreased sympathetic activation to the heart. Interestingly, prolonged QTc interval in the CM group under normal gravity was reversed compared to that of the control group under microgravity. These findings indicate that a gravitational force change from normal to hypergravity acutely increases arrhythmia risk in doxorubicin-induced CM Guinea pigs, which is reduced under microgravity. These preliminary findings in animal model are pertinent if commercial space travel aims to become commonplace and safe.