Lead or be led: an update on leadless cardiac devices for general physicians

Editor – I read with interest the article about leadless pacemakers in a previous issue of Clinical Medicine.¹ The subcutaneous implantable cardioverter defibrillator (S-ICD) has been around for several years and is still undergoing evaluation. Leadless pacing in the right ventricle is in its infancy with two major companies offering devices. The authors state that ‘battery life is predicted to exceed traditional devices’ and the device is ‘small enough for the right ventricle to accommodate further implantations without the need for extraction’. This rather glibly glosses over the potential problems of using these miniature devices. Elective replacement is almost completely ignored in the small number of publications about leadless pacemakers. Extraction of expired devices is not practical and would be extremely difficult because of fibrosis and tethering as occurs with standard endocardial leads and various debris lodged in the right ventricle (such as displaced renal shunt stents – personal experience). Implantation of further devices without removing the expired one could interfere with right ventricular function by various mechanisms – papillary muscle dysfunction, tricuspid valve regurgitation or stenosis, restricted annular motion, perforation, systolic and diastolic impairment. Furthermore, the indexed end systolic volume of the right ventricle in an adult is about 33 mL.² The device volume is given as 0.8 cc in the company online brochure³ but specific dimensions are not stated other than the inter-electrode distance of 18 mm. These measurements are not inconsiderable when compared to those of the right ventricle. A single device, let alone additional ones, will probably adversely affect overall right ventricular function. These effects remain to be seen. Leadless pacemakers will have clinical applications in appropriate patient groups, such as the frail and elderly. Many patients will have old standard endocardial leads in place, which may impede deployment. Careful monitoring of right ventricular function should be undertaken.

Conflicts of interest

The author has no conflicts of interest to declare.