Single lead electrocardiogram (ECG) showing sick sinus syndrome and atrial fibrillation

Rhythm strip showing sick sinus syndrome. The initial part (left) of the tracing reveals coarse atrial fibrillation with irregular ventricular response in the absence of drugs that slow AV nodal conduction. The atrial fibrillation terminates and is followed by a sinus beat with a prolonged sinus node recovery time of nearly four seconds.

Normal rhythm strip in lead II. The PR interval is 0.15 sec and the QRS duration is 0.08 sec. Both the P and T waves are upright.