Rangasamy V, et al. - Researchers undertook this prospective, observational analysis at a single-center teaching hospital, to test if complexity (the physiological adaptability of a system) could be used as a marker for frailty and to determine their link in cardiac surgical patients. This study included 364 adult patients receiving cardiac surgery. Preoperative beat-to-beat systolic arterial pressure (SAP) and mean arterial pressure (MAP) time series were acquired. They used multiscale entropy (MSE) analysis to calculate complexity indices. Frail patients were found to have significantly reduced complexity index (MSE_Σ) median of SAP and MAP time series. According to the findings, a correlation with frailty as well as predictive ability for frailty was demonstrated by preoperative BP complexity indices. This observation could be explained by impaired autonomic control as the underlying mechanism. The revelations are also indicative of the potential of a simple automated measure of preoperative BP complexity in the surgeon's office to offer a reliable evaluation of frailty.