Explaining Sex Differences in Cardiac Resynchronisation Therapy Outcome

Women are less likely to receive cardiac resynchronisation therapy (CRT), yet accumulating evidence suggests that they derive more benefit than men. This review summarises existing literature elucidating why sex-specific differences in CRT outcome exist. First it is demonstrated that among CRT candidates, women exhibit different risk factors resulting in better heart failure prognosis, irrespective of CRT. Second, women more often display factors associated with good response to CRT, such as non-ischaemic cardiomyopathy with lower scar burden and left bundle branch block at shorter QRS duration, possibly due to smaller heart size. Whether differences in CRT outcome can be attributed to these factors or if, after correction, a true sex difference exists, remains a topic of debate.