‘Device therapy’ refers to the use of implantable electronic devices to improve cardiac rhythm and function. Permanent pacemakers, initially developed in the 1960s to prevent bradycardia in patients with sinus node disease and atrioventricular block, represented the first wave of implantable devices that transformed cardiology practice. These devices are now commonplace, and advances in microprocessor and battery cell technology mean that pacemakers are small and highly programmable to patients’ individual requirements. Since then, this same technological revolution has led to the development of other implantable devices used in the treatment of patients with life-threatening ventricular tachyarrhythmias and with heart failure. The main focus of this article will be on these new advances in device therapy.