Over the past decade, two devices have emerged as adjuncts to optimal medical treatment for people with heart failure—cardiac resynchronisation therapy, which is delivered by atrial synchronised biventricular pacemakers, and implantable cardioverter defibrillators. The evidence base underpinning these treatments has evolved rapidly. In this week's bmj, Lam and Owen have summarised mortality data from 12 randomised trials using a Bayesian network meta-analysis.1

Their analysis confirms earlier meta-analyses showing that both devices independently improve survival in patients with heart failure (these earlier analyses also showed that resynchronisation therapy, but not implantable cardioverter defibrillators, improved functional status and reduced hospital admissions). More importantly, Lam and Owen found insufficient evidence to prove that combined devices were better than either device alone even using network meta-analysis incorporating all major trials. This analysis has four important implications for clinicians.

Firstly, while these devices work in selected patients (table⇓), their role in many patients with heart failure remains uncertain. Only 1-3% of people with heart failure meet the eligibility criteria for the trials that proved the efficacy of these devices.2 The criteria were New York …