This 62-year-old man with a five year history of nonischemic cardiomyopathy is in stable but advanced heart failure (NYHA class III) despite optimal medical therapy. His left ventricular ejection fraction is 18%:

• Sinus rhythm, 70/min
• Left bundle branch block
• QRS duration 180 msec

The patient was referred to the Electrophysiology (EP) service, and a therapeutic procedure was carried out:

• Sinus rhythm, 69/min
• DDD pacing (atrial sensed, ventricular paced rhythm)
• Right axis deviation (130°)
• QRS pattern suggestive of biventricular pacing

Comment: In right ventricular apical pacing there is usually left axis deviation, whereas in biventricular pacing there is usually right axis deviation (more frequently right superior). A biventricular pacemaker for CRT (Cardiac Resynchronization Therapy) + ICD (Implanted Cardioverter Defibrillator) had been implanted (atrial lead in the right atrial appendage; RV lead in the  right ventricular apex; LV lead in posterolateral coronary vein branch). CRT achieved by simultaneously pacing both ventricles (biventricular pacing) has been proven to produce clinical benefits and to improve survival in patients with heart failure, low LV ejection fraction and Intraventricular Conduction Delay.