Absent P waves would mean atrial stand still which can occur as an idiopathic disorder as well as following extensive radiofrequency ablation in the right atrium. Atrial stand still can also occur in certain muscular dystrophies. In severe hyperkalemia with sinoventricular conduction, P waves are absent. P waves are not visible in the surface electrocardiogram in some cases of junctional rhythm and ventricular tachycardia. Same is true of severe cases of atrioventricular nodal re-entrant tachycardia.