Relationship between cardiac function index and left ventricular ejection fraction in 46 subarachnoid hemorrhage patients with Takotsubo cardiomyopathy. (A) Three-dimensional regression data plot showing the relationship between cardiac function index (CFI) and left ventricular ejection fraction (LVEF) and time duration (days after subarachnoid hemorrhage (SAH) onset). Correlation between CFI and LVEF was analyzed by mixed-effects logistic regression (among subjects, groups, time duration). (B) Receiver operating characteristic curves constructed based on the sensitivity and specificity of the CFI for identifying LVEF <40%. Data were obtained from a simultaneous measurement of CFI and LVEF using the PiCCO™ device and echocardiograms, respectively (N = 870 data pairs).