2 The condition, current treatments and procedure
2.1 Bradyarrhythmias are abnormal heart rhythms that can result in a slow heart rate (bradycardia), usually defined as less than 60 beats per minute. There are a range of causes including diseases such as sick sinus syndrome or atrioventricular block. The most common causes are the natural ageing process, ischaemic heart disease, heart valve disorders and heart failure. If untreated, bradycardia may lead to fatigue, fainting, palpitations, dizziness, heart failure and an increased risk of death.
2.2 Bradyarrhythmias are managed with pacemakers, as described in NICE technology appraisal guidance on dual-chamber pacemakers for symptomatic bradycardia due to sick sinus syndrome and/or atrioventricular block and dual-chamber pacemakers for symptomatic bradycardia due to sick sinus syndrome without atrioventricular block. Dual-chamber pacing is recommended for symptomatic bradycardia caused by sick sinus syndrome, atrioventricular block, or a combination of sick sinus syndrome and/or atrioventricular block, and also for sick sinus syndrome in people without atrioventricular block. Single-chamber ventricular pacemakers may be used for atrioventricular block alone or with sick sinus syndrome in people with continuous atrial fibrillation, or people who have specific factors such as frailty or comorbidities that influence the balance of risks and benefits in favour of single-chamber pacing.
2.3 The aim of implanting a leadless cardiac pacemaker is to detect cardiac bradyarrhythmias and deliver electric pulses to the heart to increase the heart rate. The leadless pacemaker has a built‑in pulse generator, battery and electrodes. The procedure is done under local anaesthesia, with or without sedation, in a cardiac catheterisation laboratory. Under fluoroscopic guidance, the proximal end of the pacemaker is attached to a deflectable bespoke delivery catheter system and inserted percutaneously through the femoral vein using a dedicated introducer sheath. It is then advanced into the right atrium through the tricuspid valve, into the right ventricle and positioned near the apex or lower septum. Contrast may be injected into the right ventricle to visualise the desired location. Once positioned, the pacemaker is deployed and securely implanted into the endocardial wall using a fixation mechanism (a screw‑in helix or nitinol tines). An electrode at the distal end of the pacemaker delivers electrical impulses that pace the heart. Electrical measurements are taken and, if satisfactory, the pacemaker is released from the catheter and the catheter is removed. If the position is suboptimal, the pacemaker can be detached from the endocardium and repositioned prior to final release of the delivery catheter.
2.4 The pacemaker is programmed using an external programmer that transmits signals to it. The pacemaker can be retrieved using a catheter retrieval system, if device dislodgement is discovered at follow‑up.
2.5 The device can only detect and pace the right ventricle (single chamber) in contrast to some conventional pacemakers that can provide dual-chamber (right atrium and right ventricle) detection and pacing. It is therefore suitable for people who only need single-chamber ventricular pacing.