In this tracing, we see the limb leads + V1/V2. The first two beats are sinus node beats, there is a sinus bradycardia with approx. 55 bpm. Then there is a sinus arrest with a pause of 3000 ms, which is interrupted by a junctional escape beat. After this, the sinus bradycardia is re-established.

Perhaps Dawn would like to add some text here, as I have kept my comments here very brief.
DAWN: Thank you, Dr. Roeschl. For those who are unfamiliar with the diagnosis of "sick sinus syndrome", it is a group of rhythm disturbances that occur when there is SINUS NODE DYSFUNCTION. The dysfunction can either be due to impaired pacemaker function of the node, or impaired ability of the impulse to be transmitted out of the sinus node. SSS can produce bradycardia, tachycardia, or an alternation between the two. During periods of bradycardia, escape beats can occur, making the rhythm even more irregular. There are many causes of sinus node dysfunction, the most common being age-related sinus node degeneration. Many diseases, genetic factors, and even surgery can affect the sius node. The most effective treatment, after eliminating causes that can be corrected, is permanent electronic pacing.