infranodal block /in′frənō″dəl/ [L, infra, below, nodus, knot; Fr, bloc] , a type of atrioventricular (AV) block caused by an abnormality below the AV node, either in the bundle of His or in both bundle branches. An infranodal block has more serious clinical implications than a block at the level of the AV node. The condition is often the result of arteriosclerosis, degenerative diseases, a defect in the conduction system, or a tumor. It most often occurs in older persons. Symptoms include frequent episodes of fainting and a pulse rate of 20 to 40 beats/min. Diagnosis is made by an electrocardiogram, which shows intraventricular conduction disturbances during sinus rhythm and distinguishes nodal from infranodal block. The usual therapy is implantation of a demand pacemaker. Compare bundle branch block, intraventricular block. See also Adams-Stokes syndrome, atrioventricular block, cardiac conduction defect, heart block, intraatrial block, sinoatrial (SA) block.
