If no other pacemaker begins pacing during an episode of sinus arrest it becomes a cardiac arrest. This condition is sometimes confused with sinoatrial block, a condition in which the pacing impulse is generated, but fails to conduct through the myocardium. Differential diagnosis of the two conditions is possible by examining the exact length of the interruption of cardiac activity.
In the absence of another pacemaker taking over during a period of cardiac pause, it progresses to a complete cardiac arrest. This condition can be confused with sinoatrial block, where the heartbeat is initiated but fails to spread through the heart muscle. A detailed analysis of the length of time the heart's activity comes to a halt can aid in differentiating between the two conditions.