A 51-year-old man was assessed prior to a cholecystectomy and found to have an arrhythmia. During the previous 6 months he had noted fatigue and mild dyspnea on walking hastily:

• Sinus rhythm with complete heart block
• Junctional escape rhythm 41/min

The ECG shows sinus rhythm, 65/min., with complete heart block. The ventricular rhythm is regular, 41/min, with narrow QRS complex. This indicates that the escape rhythm is junctional.

The patient is admitted to hospital and an atrio-ventricular sequential pacemaker is implanted: 

• DDD pacing (atrial sensed, ventricular paced rhythm)
• Underlying sinus rhythm, 64/min

Comment: This is a typical ECG of a patient in sinus rhythm with AV-sequential ventricular pacing. The atrial activation (P) is sensed and is followed by a ventricular paced output (the “spike”, a sharp vertical deflection) and ventricular activation (QRS). Because the tip of pacemaker lead is in right ventricular apex, the paced QRS complex has a left bundle branch block pattern. The QRS axis of the paced ventricular complexes is directed superiorly, to the left and to the back. (left axis deviation and negative QRS from V1 to V6) Further cardiac investigation, including an echocardiogram and and myocardial perfusion studies showed no evidence of structural heart disease. One month later the patient underwent a cholecystectomy without complication.