Disclosed herein are methods, formulations, and kits for treating or preventing a heart condition, e.g., cardiac arrhythmia, e.g., atrial arrhythmia, using selective β1 adrenergic receptor blockers. Also disclosed herein are methods, formulations, and kits for treating a heart condition via inhalation or intranasal spray administration of selective β1 adrenergic receptor blocker and class I antiarrhythmic agent.
