For example, in the large multicentre HF-ACTION trial, 94% of patients were receiving β-blockers and angiotensin-receptor blocker or ACE inhibitors, and 45% had an implantable cardioverter defibrillator or implanted biventricular pacemaker at the time of enrolment.35 Given the proven survival advantage of these medical treatments, it might be expected that any incremental all-cause mortality benefit with exercise is likely to be small. Here, ACE is linked to hydrops fetalis.