Third-Degree Atrioventricular Block

A client admitted with dizziness has a very slow monitored ventricular rhythm. The P waves are regular and the QRS complexes are regular, but they have no fixed relationship to each other. The P waves march through the tracing at their own pace, sometimes falling near a QRS complex and sometimes within a T wave. This atrioventricular dissociation is the central pattern of third-degree, or complete, atrioventricular block. No atrial impulse conducts to the ventricles. The atria continue under sinus-node control while an escape pacemaker below the block activates the ventricles. The immediate danger is inadequate cardiac output or failure of the escape rhythm. The nurse therefore assesses perfusion while confirming the rhythm and making pacing support available. A client who is hypotensive, acutely confused, in shock, experiencing ischaemic chest discomfort, or developing acute heart failure has cardiopulmonary compromise and needs an emergency response rather than observation.