The Arrest Is a Trajectory, Not a Snapshot: Rethinking Point-of-Care Ultrasound During Cardiac Arrest

Point-of-care ultrasound (POCUS) is now routine during resuscitation, and clinicians may interpret a single intra-arrest finding, such as cardiac standstill, pseudo-pulseless electrical activity (PEA), or organized motion, as a fixed description of the patient's physiological state. This perspective argues that this assumption deserves scrutiny. The physiological state during cardiac arrest may evolve over time; cardiac mechanical activity may follow a trajectory that unfolds over minutes or a longer resuscitation. Published intra-arrest POCUS protocols generally define when and how imaging should be performed during brief interruptions in cardiopulmonary resuscitation (CPR) but do not provide a standardized framework for interpreting findings according to elapsed time from arrest recognition. Accordingly, the same ultrasound finding may represent different points in the resuscitation. Existing prognostic and diagnostic reviews of intra-arrest ultrasound have documented substantial variation in the timing of image acquisition without resolving what that variation means for interpretation. We propose that ultrasound findings are better interpreted as points along a trajectory than as isolated, static observations. This may provide additional temporal context for interpreting prognostic findings and help avoid overinterpretation of a single early intra-arrest observation. We translate this concept into five practical considerations: recording elapsed arrest time at acquisition, avoiding premature futility judgments from early standstill, interpreting pseudo-PEA as a potentially transitional state, considering repeat scanning where feasible without prolonging interruptions in high-quality CPR, and using ultrasound as an adjunct to established clinical assessment and resuscitation decision-making. This framework is conceptual rather than a demonstrated physiological model; available evidence does not currently establish whether observed differences reflect distinct physiological phenotypes, timing effects, or both. This hypothesis could be evaluated through prospective studies that record the timing of clinically obtained ultrasound examinations and, where serial imaging is clinically indicated, assess changes over the course of resuscitation without prolonging interruptions in CPR. Studies incorporating standardized acquisition timing and blinded interpretation of stored recordings could help determine whether acquisition timing contributes to the interpretation and prognostic value of intra-arrest ultrasound findings. Until then, clinicians should interpret intra-arrest ultrasound with attention to when a finding occurred, not only what it showed.