Leadless pacemakers: Future of cardiac pacing

 

Ramya K R*

*Asst Professor, Jubilee Mission College of Nursing, Jubilee Gardens, Kachery,Thrissur, Kerala, 68005

 

ABSTRACT:

There is a steady growth in the number of people requiring pacemaker implantation globally. In India there is no convincing information on the rates of permanent pacemaker; but it is expected to rise exponentially with rising incidence of heart disease and decreasing mortality. Current day pacemakers are safe and mature; but there are complications, when enumerated are many. A recent change in the pacing technology is the introduction of leadless cardiac pacemakers (LCP). Although investigational, leadless technology is the future. They are designed in such a way to achieve the same pacing results and longevity, in addition to lesser complications compared to a traditional pacemaker. Though recent trials have demonstrated safety and clinical performance, further research is needed to understand their long term performance, and cost effectiveness.

 

 

INTRODUCTION:

In India, cardiac pacing was introduced in 1966 to treat life threatening cardiac arrhythmias. The first pacing was performed in 1967 at the Institute of Post Graduate Medical Education and Research (IPGME&R). Bhatia et al. started pacemaker implantation at the All India Institute of Medical Science (AIIMS), New Delhi in 1968.² Pacemaker implantation is one of the most commonly performed cardiac interventions these days. More than one lakh pacemakers are implanted worldwide each year, of which 8000 are implanted in India. In India, approximately 20,000 pacemaker implants take place annually³.

 

Traditional cardiac pacemakers consist of a pulse generator (containing the battery and the machinery for sensing and timing of electrical impulses) and the leads (insulated wires that deliver electrical impulses from the pulse generator to the heart). Though pacemakers increase survival in at-risk patients and greatly improve quality of life; they are associated with several procedure related and device related complications. These may be attributable to either the pulse generator or venous access and lead implantation⁴. Of these the leads of traditional pacemakers are the main concern, in the long run⁵. All the above complications are associated with considerable increase in morbidity mortality and cost.

 

With increasing number of patients with heart diseases, the number of patients requiring pacemaker therapy is increasing dramatically. Cardiac pacing devices are undergoing continuous refinement based on experiences from the clinical trials and advancement of technology. The newer devices have improved clinical performance and safety features. But the basic design of cardiac pacemakers has remained relatively unchanged. Introduction of leadless or wireless pacemakers is a revolutionary advancement in the pacing technology, which exclude the weakest link in the conventional pacing system.

 

Leadless Pacemakers:

A leadless pacemaker is a small implantable device with built-in battery and electrode. it is placed directly in the heart that sends electrical pulses to the heart whenever it senses a low heartbeat. The small size of the device and lack of a surgical pocket, coupled with the exclusion of a lead, improves patient comfort and reduces complications. These devices are implanted in the same setting as traditional pacemakers in a cardiac catheterization laboratory or operating room under local anesthesia using sedative medications. The LCP is an entirely self-contained device (42 mm length; maximal diameter 5.99 mm) that includes the pacemaker, electronics, lithium battery, and electrodes. These devices have battery longevity of nearly 10 years.

 

Pacing Technologies:

There are two leadless pacemakers undergoing clinical study in the United States, the Nanostim (St. Jude Medical, St. Paul, Minnesota) and the Micra transcatheter pacing system (Medtronic, Minneapolis, Minnesota) which are currently under clinical trials. Both are self-contained unit comprising a battery, low current electronics, and fixation mechanism. The Nanostim pacemaker is less than 10% of the size of a traditional pacemaker, and the Micra TPS pacemaker is 30% smaller than the Nanostim. The average battery life ranges between 8.4 years and 12.4 years, and 10 to 15 years resp. for Nanostim and Micra TPS depending on pacing parameters. A screw-in helix fixes the Nanostim pacemaker to the right ventricle. Four tines (prongs) anchor the Micra TPS to the right ventricle. These tines are designed to minimize tissue trauma during repositioning.

 

Leadless Pacemaker Implantation:

Leadless pacemaker implantation is done via pecutaneous femoral vein approach under fluoroscopic guidance. Strict surgical sterile precautions are followed during implantation. The pacemaker is delivered into the right ventricle across the tricuspid valve with use of a deflectable/steerable delivery catheter in both devices. Once positioned the sleeve is retracted and the device is undocked from the delivery catheter while maintaining a tethered connection to permit device measurements and stability. If position is suboptimal the leadless pacemaker can be rearranged, repositioned or retrieved.

 

Advantages:

Favorable cosmetic profile: Implantation of leadless pacemakers requires no chest incision, no scar and no permanent lump under the skin where the pacemaker sits unlike a conventional pacemaker.

Fewer acute and chronic complications: Absence of subcutaneous pocket and leads provides as enormous advantage of removing pocket and lead related complications. Elimination of subcutaneous pocket avoids pocket infection, hematoma and bleeding, migration of pacemaker, wound dehiscence, erosion, twiddler’s syndrome. Absence of lead related complications (venous obstruction, pneumothorax, cardiac tamponade, lead dislodgement or fracture, insulation breaks, electrical malfunction, and infection, endocarditis, valve Injury) are one of one of the other biggest advantages with these life saving devices. In addition to this use of femoral access almost eliminates complications of subclavian puncture like penumothorax, hemothorax, DVT, air embolism.

 

Improving the quality of life: Conventional pacemaker implantation require activity restrictions to prevent lead dislodgement or damage resulting in shoulder pain and disability.LCP avoids this, improving mobility in the shoulder region promoting quality of life for patients.

 

Shorter hospital stay: The procedure is faster (averaged 28 min), minimally invasive, which may improve recovery times for patients.

 

More MRI conditional: Lack of ferrous material makes Leadless cardiac pacemakers safe for use with magnetic resonance imaging (conditionally).

 

Multisite pacing: Future advances in the technology raises the possibility of multichamber pacing and multisite pacing within a chamber.

 

Less exposure to radiation: There is potentially less radiation exposure for the implanting physician and team because of greater distance between the radiograph source and the operator.

 

Easy repositioning: These can be easily repositioned during procedure and later retrieved if necessary, such as at the time of normal battery replacement.

 

Single unit: LCP eliminates the possibility of intrasystem connection issues, such as loose set screws and air in the header, because the endocardial pacing electrode and pulse generator are a single unit.

 

LIMITATIONS:

The LEADLESS multicenter prospective trial (2014) conducted among human subjects has shown the safety, feasibility and clinical performance of leadless cardiac pacemaker. The implantation success rate was 97% (32 of 33 patients).One patient developed right ventricular perforation/cardiac tamponade and subsequently died of a stroke. There were no other associated complications in the 12 months follow up⁶. Similarly LEADLESS II trial highlighted 100% retrievability and longevity of 9.8years at 100% pacing. The other perceived limitations are the possibility of embolization, reposition difficulty for high thresholds, memory limitation, pediatric pacing and the need for larger diameter sheath during implantation⁷. It is also expected that leadless pacemakers will be more expensive than conventional pacemakers.

 

CONCLUSION:

There had been remarkable advances in the development pacemaker technology over the last 50 years. The technology has made pacemakers smaller, safe, reliable and more sophisticated. The introduction of leadless pacemaker is a game changing technology as this virtually eliminates pocket and lead related complications. But further clinical trials are required to ensure the efficacy and stability of leadless pacemakers.

 

REFERENCE:

1.     Mond HG¹, Proclemer A. The 11th world survey of cardiac pacing and implantable cardioverter-defibrillators: calendar year 2009--a World Society of Arrhythmia's project. Pacing Clin Electrophysiol. 2011 Aug; 34(8):1013-27. doi: 10.1111/j.1540-8159.2011.03150.x. Epub 2011 Jun 27

2.     Nair M, Francis J, Venugopal K. Development of pacing, electrophysiology and defibrillation in India. Indian Pacing Electrophysiol J 2002; 2:57-61

3.     www.thehindu.com/news/national/...pacemakers.../article3207221.ece

4.     Udo EO, Zuithoff NP, van Hemel NM, de Cock CC, Hendriks T, Doevendans PA, Moons KG. Incidence and predictors of short- and long-term complications in pacemaker therapy: the FOLLOWPACE study. Heart Rhythm. 2012; 9:728–735.

5.     Gard JJ, Cha YM, Friedman PA. Leadless pacing and defibrillation systems. Card Electrophysiol Clin. 2013; 5(3):327-35.

6.     Reddy VY, Knops RE, Sperzel J, Miller MA, Petru J, Simon J, et al. permanent leadless cardiac pacing: results of the LEADLESS trial. Circulation. 2014; 129:1466-71.

7.     Reddy VY. Chronic performance of leadless cardiac pacing: one year follow-up to the LEADLESS trial [webcast]. In: Heart Rhythm 2014: expedited sessions. 2015 [cited 2015 Feb 4]. Available from: http://www.hrsonline.org/Education-Meetings/Scientific-Sessions/Expedited-Sessions#axzz3QdHF5MsC

 

 

 

 

 

 

 

 

 

Received on 20.11.2015           Modified on 08.12.2015

Accepted on 01.11.2017         © A&V Publications all right reserved