If bradycardia is confirmed or suspected in a patient, possible intrinsic or extrinsic causes must be sought, including obstructive sleep apnea (absent breathing due to obstruction in the throat by the uvula), and medications affecting heart rate (see figure 93a). The thyroid should be tested for activity.

Bradycardia must be confirmed by EKG. If the symptoms are intermittent, a 24 hour EKG Holter test (see figures 96A, 96B, 97, 98, 99, 100, 101, 102) may be necessary to assist with the diagnosis and the correlation of symptoms with the onset of bradycardia.

Also, testing with the EKG while the patient is lying on a tilt table with a head up position may be used to provoke an episode of fainting with changes in heart rate and blood pressure. Invasive electrophysiologic testing is rarely needed, but may be helpful if the mechanism responsible for bradycardia remains uncertain, or if symptoms suggest the presence of a life-threathening arrhythmia.