Healthy Subjects and Patients with and without Heart Failure

multilevel atrioventricular block. These interpretations can be made from the clinical electrocardiogram and do not require complex electrophysiologic studies. This phenomenon is not rare and occurs under a variety of clinical circumstances. It is likely that multilevel block is far more common than previously suspected, since stable 4: 1 block in atrial flutter probably represents two levels of 2: 1 block. The more complex patterns are often transient, or may simply not be recognized. The patterns presented in this series are not exhaustive of the permutations of multilevel block that can occur. Recognition that block can occur at more than one level in the A-V conduction system may facilitate the interpretation of hitherto obscure rhythm disturbances and thereby aid in the management of the patient with arrhythmia.