Current Leadless Cardiac Pacemakers (LCP's):
The new era of miniaturization started with leadless devices and currently there are companie which are into leadless pacing devices. The first is the device called Micra Transcatheter Pacing System (TPS), made by Medtronic Inc. which is the ‘world's smallest pacemaker' (93% smaller than a conventional pacemaker) with dimensions of just 7 mm in width, 26 mm long and 2 g in weight. The estimated battery life was around 10 – 12 years. The TPS uses self-expanding Nitinol tines to fixate in the trabeculae.
Nanostim device is manufactured by Abbott Inc. The device is smaller than a AAA battery and can be directly placed inside the heart through the femoral route approach.
Implantation Technique: Nanostim LPS has a screw-in helix.
This 4-cm long, 6-mm wide,and just 2 g in weight LCP
It has a long battery life of 9 -10 years.
A Wireless Cardiac Stimulation system (WiCS-LV) is also being developed by
EBR Systems (Sunnyvale, CA, USA). The system utilizes ultrasound emitted from a
transmitter implanted subcutaneously in the left chest and a receiver implanted
in the ventricle which converts ultrasound energy to electrical energy that can be
used to pace the heart.
In contrast to the aforementioned devices, the WiCS-LV system has been used in cardiac resynchronization therapy (CRT) when
used with conventional right ventricular pacers. Hence both ventricles will contract almost simultaneously which allows resynchronization. It should be noted that Nanostim from St Jude Medical (now Abbott) is not available commercially while WiCS – LV is not commercially launched in many countries worldwide.
Potential Complications with Conventional Pacing System:
The pacing leads used in conventional pacemakers have long been considered the Achilles’ heel . Although low in incidence, the implantation process may result in acute or early complications such as lead dislodgement, pneumothorax, cardiac perforation, and tamponade. Overall, the rate of peri-procedural and early post-procedural complications in cardiac pacing therapy is estimated, approximately, to be 10%.
Chronic lead problems occur at a rate of 10%, they are :-
- Venous thrombosis and superior vena cava obstruction
- Significant regurgitation of the tricuspid valve
- Infections (incidence of 1-2%)
- Lead fracture (subclavian crush)
- Lead insulation break (abnormal pacing/sensing causing shortening of battery longevity)
Infection of pacemaker pocket still causes havoc despite adherence to sterile techniques. All leads and pacemaker device removal maybe warranted in case of infection. The pacemaker designs have been changed to prevent pocket erosion.
Owing to the absence of leads and no requirement for a surgical pocket the LCP have overcome these issues.