[Do the guidelines always show us the ideal treatment of patients for cardiac resynchronisation therapy?].

We present a case of 80-year-old man with chronic atrial fibrillation and heart failure with mildly depressed left ventricular ejection fraction who deteriorated after implantation of pacemaker to right ventricular apex. The patient improved when pacemaker was upgraded to resynchronisation therapy (CRT). The question is raised if CRT should have been implanted primarily.