A retrospective cohort study found that severe heart complications were rare despite high rates of European cardio-oncology toxicity criteria being met by CAR T-cell recipients. The investigators reported that toxicity classifications were driven overwhelmingly by subclinical biomarker elevations rather than severe cardiac events. The analysis reframes how cardio-oncology safety signals should be interpreted in CAR T practice, emphasizing that biomarker-based grading may overestimate clinically meaningful cardiotoxicity. This can influence monitoring protocols, trial endpoints, and how sponsors communicate risk-benefit profiles.