Context

Cardiac resynchronisation therapy (CRT) is now a well-established therapy for certain subgroups of patients with heart failure, with a large body of evidence demonstrating improvement in symptoms and beneficial changes in cardiac structure and function. American and European guidelines support its use in patients with New York Heart Association (NYHA) class III and IV heart failure, prolonged QRS duration and left ventricular ejection fraction <35%. The COMPANION trial1 demonstrated an all-cause mortality benefit of CRT when combined with implantable cardioverter defibrillator (ICD) therapy in this subgroup, and, subsequently, the CARE-HF trial2 established a mortality benefit attributable to CRT alone when compared with optimal medical therapy (OMT). More recently, the REVERSE3 and MADIT-CRT4 trials in patients with less severe, NYHA …