Therapeutic cardiac stimulation has been in clinical practice for many decades.¹ During the evolution of the therapy, pacing generators have shrunk in size, increased in longevity, and increased in device complexity. They offer rhythm and disease state diagnostics, with various algorithms designed to offer timing of delivery of pacing impulse and more recently diagnostics indicative of pathophysiology. Pacing leads have also reduced in size and improved in durability. Pacing electrode configurations have enhanced sensing capability and stability of long term pacing function.

With the potential for a range of biosensors that could be incorporated in pacemaker devices to further the potential for pathophysiological monitoring, cardiac pacing has achieved an extraordinary maturity in the armoury of cardiac treatments. However, it has taken much longer for there to be large scale clinical trials on the therapeutic efficacy of devices, long term patient well being, and the impact of right ventricular pacing on left ventricular function.

INDICATIONS AND MODE CHOICE

These are summarised in published European and North American guidelines.^2,3 There are three electrophysiological conditions (sinus node disease, atrioventricular (AV) node disease, and neurally-mediated (cardio-inhibitory) syncope) which may cause either prognostically or symptomatically significant bradycardia, and this review focuses only on these. These conditions may be treated by single chamber ventricular sensing/pacing, dual chamber sensing/pacing or (if AV nodal function is normal) single chamber atrial sensing/pacing.

The choice of appropriate pacing modality to treat these electrophysiological abnormalities is governed by our understanding of the morbidity that attends the conditions themselves, the influence of pacing on that morbidity, and a further morbidity that may attend the chosen pacing mode. To understand this complex interaction we need to look to the evidence base that reports efficacy and complications of pacing therapy in varying patient populations with differing electrophysiological and cardiac disease.

STUDY BACKGROUNDS

This article focuses on six …