Leadless Pacemakers: A Perspective in the Indian Context

Introduction

The Six decades after the first pacemaker implant in humans, has seen this therapy benefitting countless number of patients with serious bradyarrhythmia. ¹ The mode of pacing was almost exclusively using pacing leads and a pulse generator implanted in a subcutaneous pocket. Over the years, the pacemakers and leads saw significant advances in technology, making them safer, more adaptive to physiological needs and in programming capabilities that could be used to tailor to individual patient needs and troubleshooting using external device interrogation and programming. ²

The Need for Leadless Pacemakers

Despite improvement in technology, the conventional pacemaker has been associated with a small but definite incidence of complications; variously reported as between 1% and 8%. ³ These have included generator pocket hematoma, infection, lead displacement, and lead fracture. Repeat intervention to take care of these complications is associated with a higher morbidity and even mortality.

Leadless pacemakers attempt to deal with some of these issues. These devices, which are the size of a pen-drive, are implanted directly into the right ventricle through percutaneous, transvenous access, and are completely devoid of any lead. This potentially disruptive technology already has a small yet significant quantum of evidence in terms of clinical evidence. ⁴

The Path So Far

The first leadless pacemaker introduced was the NanoStim (St. Jude Medical, USA). This device, however, had to be withdrawn because of an unacceptable rate of early battery depletion, non- communication with the device programmer and also device disc dislodgement. ⁵ The experience with the second device from another manufacturer (Micra- Medtronic Inc, Minneapolis, USA), has been far more encouraging, with early and mid-term results showing less device-related complications and good pacemaker performance. ⁶

Issues with the Leadless Pacemaker, Particularly in the Indian Context and the Way Ahead

These pacemakers are essentially single chamber devices, with an intra-cavitary implantation and cost up to 10 times more than a conventional pacemaker. This is perhaps the most important limitation to its more widespread use even for single chamber device indication in India. The new Micra-VDDR incorporates a sensor with a downloadable program that facilitates AV synchrony. Although the MARVEL-2 study showed an acceptable rate of proper atrial activity sensing and maintenance of AV synchrony, real world data show that that this technology requires further refinement.^{7, 8} Considering that Complete Heart Block continues to be the most compelling indication for pacemaker in India, as compared to Sick Sinus Syndrome in several other countries; capability to maintain AV synchrony would be an important attribute for any pacemaker. ⁹

There are other important issues as well that remain unaddressed. These include device retrieval/repositioning and more importantly the impact of device replacement/a second device within the same chamber, at end of life of the first implant. This is particularly pertinent, as the average age of first implant is considerably lower in Indian patients as compared to the west.

The status of this amazing new technology has been well summarized by Larry A. Chinitz in a recent commentary on the technology “Despite wide adaptation and current enthusiasm over leadless technology, development is still in its infancy, and the potential seems endless.” ¹⁰