How Well Do Multimodal Models Reason on ECG Signals? - Maxwell A. Xu; Harish Haresamudram; Catherine W. Liu; Patrick Langer; Jathurshan Pradeepkumar; Wanting Mao; Sunita J. Ferns; Aradhana Verma; Jimeng Sun 001; Paul Schmiedmayer; Xin Liu; Daniel McDuff; et al. (CoRR, 2026)