This 69-year-old woman is referred by her family doctor. For several years, she has had episodes of paroxysmal atrial fibrillation. Recently, she complains of severe fatigue and faintness:

• AV dissociation
• Marked ectopic atrial bradycardia (P waves with abnormal morphology and axis – rate 34/min)
• Junctional escape rhythm – ventricular rate 34/min
• One AV capture with aberration (right bundle branch block pattern)
• Minimal voltage criteria for left ventricular hypertrophy (SV1 + RV5 = 35 mm) 

This is a typical case of sick sinus syndrome (SSS), with a period of paroxysmal atrial fibrillation followed by severe bradyarrhythmia (sinus arrest and escape slow atrial and junctional rhythm). An AV sequential pacemaker was implanted.