Ivabradine, Propranolol, and Placebo for Postural Orthostatic Tachycardia Syndrome (POTS): A Randomized Crossover Trial. - Uppal J; Deol P; Giri P; Singh A; Hamzeh R; Qi J; Chew DS; Runte M; Sheldon RS; Raj SR (Journal of the American College of Cardiology, 2026)