Leadless Intracardiac Transcatheter Pacing System

Mrs. Sheeja Sebastian, Mrs. Neethu Jose

Asst. Professor, Jubileemission college of Nursing

*Corresponding Author Email: sheejavsebastian@yahoo.co.in

ABSTRACT:

Cardiac pacemakers are limited by device-related complications, notably infection and problems related to pacemaker leads. Innovative product development eliminates pacing leads by stimulating the heart through wireless transmission of energy. A tiny, wireless heart pacemaker showed promise in early tests and could offer an alternative to conventional, wired pacemakers. Unlike traditional pacemakers - which need a generator and wires and are implanted via surgery - the new pacemaker is a wireless tiny tube that can be attached to the right side of the heart using a catheter inserted through the leg. While most pacemakers have wires connecting the device to the right and left sides of the heart, the new device sits in the right ventricle and doesn't coordinate the two sides. The mini pacemaker is the size of a large pill and can be placed without surgery. Two leadless pacemakers, the Micra Transcatheter Pacing System (TPS) (Medtronic) and the Nanostim (St. Jude Medical), are currently in development. Each consists of a self-contained intracardiac device including the pacemaker, electronic circuits, battery, and leads⁽¹⁾. It has a low rate of complications compared to traditional pacemakers. Wireless pacemaker is now primarily intended for a small portion of patients who have an abnormal heart rhythm known as long-lasting persistent atrial fibrillation, plus a slow heartbeat. It may also be the only technology for kidney failure patients on dialysis or patients who have chronic blood vessel infections.

KEYWORDS: cardiac pacing, cardiology, pacemaker, arrhythmias, trans-catheter pacemaker.

INTRODUCTION:

For more than half a century, permanent cardiac pacing for symptomatic bradycardia has been achieved with systems that consist of a surgically implanted subcutaneous electrical generator connected to one or more transvenous leads that deliver the pacing therapy to the heart. Although Conventional Pacemakers are effective, approximately one in eight patients has an early complication, frequently related to the lead or leads or to the subcutaneous “pocket.”Complications include problems with the subcutaneous pocket, such as hematomas and infections; lead-insertion problems, such as pneumothoraxes and hemothoraxes; lead dislodgements and integrity problems; infections, including septicaemia and endocarditis; vascular obstructions; and reduced vascular access.

The pursuit of leadless pacing options has long been of interest to reduce the complications that can lead to interruption of pacemaker therapy, to hospitalization, or to death² Innovative product development eliminates pacing leads by stimulating the heart through wireless transmission of energy. The new device, called the wireless cardiac stimulation (WiCS) system. Cardiac stimulation leads considered the weak point in pacemaker systems. WiCS is the first leadless system to be successfully implanted in early human clinical trials at leading centres in Europe³. "This is another landmark in the development of pacemakers," said Dr. Christopher Granger of the American Heart Association.

Two Different Models⁴

1) Nanostim (St. Jude Medical) : looks like an AAA battery. It measures 6mm in diameter and 42mm in length. It is less than 10% of the size of a traditional pacemaker, with a battery life ranging between 8.4 years and 12.4 years, depending on pacing parameters. A screw-in helix fixes the Nanostim pacemaker to the right ventricle.

2) Micra (Medtronic): is about the size of a multivitamin. It measures a length of 25.9 mm, an outer diameter of 6.7 mm, and a weight of 2.0 g. It is 30% smaller than the Nanostim. Four tines (prongs) anchor the pacemaker to the right ventricle. Battery life ranges from 10 to 15 years

Types of Transcatheter pacing system

Functioning ^1,2,5

The new device uses focused acoustic waves that are picked up by a small receiver implanted permanently inside the heart, converting the energy into electricity. WiCS uses a leadless electrode to convert mechanical energy from an ultrasonic pulse generator, into electrical energy which is used to pace the heart as part of Cardiac Resynchronization Therapy (CRT).²

The two devices share common features. Both are inserted by catheter directly into the heart, where they help control heart rhythm by speeding up a slow heart and adjusting the rate when a boost of energy is required. Both models are single-chamber devices, meaning they can pace one side of the heart, but not both sides. This means they can only be used in patients with bradycardia who need pacing on one side of the heart.

Parts of transcatheter pacing system

Procedure^2,3,6,5

The device sits in a steerable catheter delivery system and is inserted through a femoral vein with the use of a 23-French introducer. The catheter is advanced into the right ventricle, and the device is affixed to the myocardium through four electrically inactive nitinol tines located at the distal end of the device. After verification of device fixation and adequate electrical measurements, a tether is cut, and the delivery system is removed ⁵

A very small leadless electrode is implanted in the desired location .it sense the electrical pacing pulse of the pacemaker from the right ventricle. The pulse generator then transmits an ultrasonic pulse to the implanted receiver, which converts the sonic energy into electrical energy to pace the left ventricle in synchronicity with the right.

STUDY RESULT:

A prospective, nonrandomized, single-study-group, multisite, international clinical study to evaluate the safety and efficacy of the Micra Transcatheter Pacemaker System (Medtronic) was conducted in 725 patients at 56 centers in 19 countries in North America, Europe, Asia, Australia, and Africa. Of the 725 attempted implantations, 719 (99.2%) were successfully performed by 94 physicians. The six patients who underwent unsuccessful implantation attempts included four patients with major complications (three with cardiac perforations and one with pericardial effusion), one patient with tortuous venous anatomy, and one patient in whom a satisfactory pacing capture threshold could not be obtained. Among the 725 major complications related to the system or procedure was 96.0% at 6 months after implantation (95% confidence interval [CI], 93.9 to 97.3%; P<0.001 for the comparison with the safety performance goal of 83%).There were no radiographically visible device dislodgements, no telemetry failures, and no systemic infections^1,2.

Wireless pacemaker Vs Conventional Pacemakers⁶

Wireless pacemaker

Conventional pacemakers

· Inserted directly into the heart without surgery

· Flexible tines that attach to the interior of the right ventricle/

· Cardiac injuries affected

· Less complications

· Battery is implanted under the skin through an incision in the chest

· leads' used to connect to the heart

· Leads can break, wear out or become infected

· More complications

CONCLUSION:

This new technology will ultimately eliminate all pacing leads and deliver superior cardiac pacing therapy through its flexibility in where the electrode can be placed. Eliminating the lead presents a major breakthrough in pacemaker design, and brings new hope for over 2.2 million advanced heart failure patients worldwide, who can benefit from CRT therapy. It also provides a life-saving option for those patients who do not benefit from CRT therapy, either because of the complexity of the procedure, or the limitations of the current technology.

REFERENCE:

1. https://www.cadth.ca/leadless-pacemakers-treatment-cardiac-arrhythmias

2. http://www.nejm.org/doi/full/10.1056/NEJMoa1511643

3. ww.cambridgeconsultants.com/projects/ebr-wireless-pacemaker

4. https://www.cadth.ca/leadless-pacemakers-treatment-cardiac-arrhythmias

5. https://www.cadth.ca/leadless-pacemakers-treatment-cardiac-arrhythmias

6. http://www.medgadget.com/2015/09/new-wireless-pacemaker-implanted-without-surgery-found-safe-in-clinical-study.html

Received on 03.08.2016 Modified on 15.09.2016

Asian J. Nur. Edu. and Research.2017; 7(1): 133-135.

DOI: 10.5958/2349-2996.2017.00027.1