Complete heart block refers to a form of atrioventricular dissociation where no P wave produces a QRS complex. A sinus or ectopic atrial rhythm develops that fires independently of the ventricles. This rhythm may be junctional (as illustrated below) or ventricular in origin. The rhythm is usually regular, but may present irregularly as a result of intermittent premature ventricular beats. Patients presenting with complete heart block complain of symptoms resembling profound bradycardia (loss of atrial kick) and reduced cardiac output (syncope, angina, presyncope).