Cardiac resynchronization therapy (CRT) is a recognized treatment for patients with systolic heart failure, dyspnea with NYHA class II-IV despite optimal medical treatment, ejection fraction < or =35% and QRS duration > or =120 ms. This article reviews and comments upon the latest pacemaker guidelines by the European Society of Cardiology that were updated in 2013. The main changes in these guidelines are to take into account QRS morphology to optimize patient selection, and to prescribe CRT in patients requiring frequent ventricular pacing and reduced ejection fraction, irrespective of baseline ORS duration and heart failure status.