MADIT-CRT was designed to investigate whether cardiac resynchronization therapy (CRT) would decrease the risk of death or heart failure events in patients with ischaemic or non-ischaemic heart disease, mild cardiac symptoms, reduced ejection fraction and broad QRS complex. Dr Clyde Yancy, medical director at the Baylor Heart and Vascular Institute, recognized the trial as one “capable of changing practice”, stressing the importance of a broad QRS duration in explaining outcomes.

CRT improves quality of life and decreases all-cause mortality and unplanned hospitalizations for major cardiovascular events. Updates on CRT recommendations from the American College of Cardiology/American Heart Association (ACC/AHA) practice guidelines indicate that, “unless contraindicated, CRT is recommended in patients with LVEF less than or equal to 35%, sinus rhythm, NYHA functional class III or ambulatory class IV symptoms despite recommended optimal medical therapy, and who have cardiac dyssynchrony (ie, QRS duration >120 ms).”

MADIT-CRT data demonstrated a particular benefit in patients with QRS duration >150 ms, with CRT reducing readmission/heart failure events by 41% in this population. Data from a recent meta-analysis involving MADIT-CRT showed improved LV remodeling without effect on mortality. The FDA panel has expanded indications for CRT to include mild-to-moderate heart failure highlighting patients with a broad QRS complex as obtaining the greatest benefit from the therapy. The increased benefit of CRT in women remains unexplained. Major implications of the study are as follows:

• There is a need to review ACC/AHA guidelines and revise accordingly
• Current data support use of CRT in mild to moderate HF
• CRT (and device therapy) remains underutilized
• New data are likely to reset indication with a longer QRS
• For all classes of HF, the correct marker of benefit may be a QRS duration longer than 120 ms