Effects of inversion on cardiovascular function: the bat scan

This study was performed to measure the effect on cardiovascular functional parameters of remaining in an inverted position for a relatively short period of time. With the aid of radionuclide gated bloodpool scanning techniques, left ventricular ejection fraction (LVEF), heart rate (HR), systolic blood pressure (SBP), systolic average rate of left ventricular emptying (dV/dt), and double product (DP) measurement values were obtained from 16 normal, healthy subjects in four positions: supine, standing, half-inverted, and fully inverted. When comparing full-inversion to supine values, the HR and double product were not significantly different, the SBP was significantly higher, and the LVEF and dV/dt values were significantly lower. There were no significant differences between the partial and fully inverted positions. Comparison of standing to fully inverted positions reveals no significant change in SBP or double product. HR, LVEF, and dV/dt values were significantly lower in inverted subjects. It is suggested that these findings reflect the mechanism by which the cardiovascular system compensates for increased ventricular end-diastolic volume. Suggestions for future investigations include inverted cardiac ultrasound and right ventricular function studies.