Monitoring the patient with conduction disturbances and blocks

Intracardiac block can occur anywhere from the sinus node to the far reaches of the ventricular conduction system. A common site is in the AV junctional area. Block in this region ranges from simply an increased conduction time across the AV junction (first-degree block) through occasionally blocked conduction of supraventricular impulses (second-degree block) to selective block in the ventricular conduction system (BBB and hemiblocks) and finally to complete block of impulses between the atria and the ventricles. When complete block occurs, the heart is stimulated by two separate pacemakers, one above the AV node, usually the sinus node, and one below the block, either an intrinsic pacemaker or an implanted electronic device. For block to be recognized in monitored patients, the EKG lead chosen must be one in which both atrial and ventricular electrical activity can be clearly identified.