ABSTRACT
Atrioventricular (AV) block is classified as first, second or third degree depending on whether conduction of atrial impulses to the ventricles is delayed, intermittently blocked or completely blocked.
FI R S T-D E G R E E AT R I OV E N T R I C U L A R B L O C K
Delay in conduction of the atrial impulse to the ventricles results in prolongation of the PR interval (Figures 15.1-15.3). The PR interval is measured from the onset of the P wave to the onset of the ventricular complex – whether this is a Q or an R wave – and is prolonged if it is greater than 0.21 s. Since conduction of the atrial impulse is only delayed, the term first-degree AV block is, in fact, a misnomer.
