Atrial Bradycardia

This paper describes a group of patients who have chronic bradycardia, due to a slow atrial rate. This can be the result of sinus bradycardia or produced by block between the sinus node and the atrium. The distinction between the two processes may be difficult, since electrical discharge of the sinus node does not give rise to a deflection on the standard electrocardiogram. For a start, therefore, they will be grouped together as atrial bradycardia. There are three common groups of causes for atrial bradycardia: physiological, in association with an increased vagal tone in normal subjects; drug induced, as with digoxin, propranolol and the newer hypotensive agents; and in association with certain disease states, such as myxcedema, hypopituitarism, and raised intra-cranial tension. However, five years ago we saw three patients with atrial rates of about 40 per minute which could not be explained by any of these processes, and we therefore started to collect patients with the condition.