The "frog sign" is nothing more than the cannon-type "a" waves produced by the nearly simultaneous contractions of the atria and ventricles while the mitral and tricuspid valves are closed in the setting of a rapid tachyarrhythmia. This causes an abrupt increase in right atrial pressure that is transmitted in reversal of flow in the superior vena cava resulting in jugular venous pulsations. | Cardiophilia