Recent Advances in Pacing and Defibrillation

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Cardiac pacemakers have been the standard therapy for patients with bradyarrhythmias for several decades. The pacing lead is an integral part of the system, serving as a conduit for the delivery of energy pulses to stimulate the myocardium. However, it is also the Achilles' heel of pacemakers, being the direct cause of most device complications both acutely during implant and chronically years afterwards. Leadless pacing with ultrasound-mediated energy has been demonstrated in animals and humans to be safe and feasible in acute studies. Implantable defibrillators revolutionised the treatment and prevention of sudden cardiac death. Subcutaneous implantable defibrillators have been under development for more than 10 years. A permanent implantable system has been shown to be feasible in treating induced and spontaneous ventricular tachyarrhythmias. These developments and recent advances in pacing and defibrillation will arouse further interest in the research and development of leadless cardiac implantable electronic devices.

Kathy L Lee has received a research grant from EBR Systems, Inc.
Kathy L Lee, Division of Cardiology, Department of Medicine, Queen Mary Hospital, Hong Kong, 102 Pokfulam Road, Hong Kong SAR, China. E:
Received date
09 September 2010
Accepted date
05 October 2010
Asia-Pacific Cardiology - Volume 3 Issue 1;2011:3(1):74-76
Kathy L Lee, Division of Cardiology, Department of Medicine, Queen Mary Hospital, Hong Kong, 102 Pokfulam Road, Hong Kong SAR, China. E:


All pacing leads are associated with complications such as infection, fracture, failure and dislodgement. Lead extraction is a high-risk procedure. With new device systems that often require implantation of multiple leads and with patients living longer, the incidence of lead complications is becoming compounded over time.1 Therefore, there is a strong demand to develop a pacing system that eliminates the pacing lead as a conduit for energy transfer. Randomised clinical trials on cardiac resynchronisation therapy have demonstrated the clinical benefits of such a system. Access to the left ventricle is achieved with the use of a pacing lead that is advanced into the coronary sinus and positioned in a coronary vein branch. Implantation of this lead is technically demanding and associated with a significant incidence of failure to implant, implantation in a suboptimal location and complications.2,3 Compared with epicardial pacing, endocardial left ventricular stimulation that minimises the conduction delay from the epicardium to the endocardium may be more physiological and therefore may give rise to greater haemodynamic benefits.4,5 Leadless pacing will enable endocardial left ventricular stimulation without the risks of systemic thromboembolism and mitral regurgitation. It will also avoid diaphragmatic stimulation and right ventricular apical pacing, enable multisite pacing and allow almost free choice of stimulation location within the left or right ventricle. It may also address challenges in paediatric pacing and allow the development of a truly magnetic resonance imaging (MRI)-compatible pacing system.

Leadless Pacing with Acoustic Energy

Many concepts have been patented for the development of a leadless pacing system. With a long history and wide application in medical technology, ultrasound energy is considered safe and was chosen to prove the concept of energy transfer. The use of ultrasound-mediated energy to drive a remotely positioned electrode for direct myocardial stimulation is the first to be reported in the medical literature. This new technology uses the mechanical-to-electrical properties of piezoelectric materials for transformation of energy.


  1. Borek PP, Wilkoff BL, Pacemaker and ICD leads: strategies for long-term management, J Interv Card Electrophysiol, 2008;23:59-72.
  2. Bax JJ, Abraham T, Barold SS, et al., Cardiac resynchronization therapy. Part 2 - Issues during and after device implantation and unresolved questions, J Am Coll Cardiol, 2005;46:2168-84.
  3. Barold SS, Herwerg B, Pacing in heart failure: how many leads and where?, Heart, 2008;94:10-13.
  4. Van Deuren C, van Hunnik A, Kuiper M, et al., Endocardial left ventricular pacing improves cardiac resynchronization therapy in canine LBBB hearts, Circulation, 2007;116:222.
  5. Rademakers LM, van Hunnik A, Lampert A, et al., Electrical and hemodynamic benefits of endocardial CRT with chronic infarction and LBBB. Presented at Heart Rhythm 2009, Boston, USA, 13-16 May 2009.
  6. Echt DS, Cowan MW, Riley RE, Brisken AF, Feasibility and safety of a novel technology for pacing without leads, Heart Rhythm, 2006;3:1202-6.
  7. Lee KL, Lau CP, Tse HF, et al., First human demonstration of cardiac stimulation with transcutaneous ultrasound energy delivery: Implications for wireless pacing with implantable devices, J Am Coll Cardiol, 2007;50:877-83.
  8. Lee KL, Tse HF, Echt DS, Lau CP, Temporary leadless pacing in heart failure patients with ultrasound-mediated stimulation energy and effects on acoustic window, Heart Rhythm, 2009;6:742-8.
  9. Sweeney MO, In a footnote, at least, Heart Rhythm, 2006;3:1207-9.
  10. Benditt DG, Goldstein M, Belalcazar A, The leadless ultrasound pacemaker: a sound idea?, Heart Rhythm, 2009;6:749-51.
  11. Wieneke H, Konorza T, Erbel R, Kisker E, Leadless pacing in the heart using induction technology: a feasibility study, Pacing Clin Eletrophysiol, 2009;32:177-83.
  12. Loeb GE, Richmond FJR, Singh J, et al., RF-powered BIONS's™ for stimulation and sensing. Presented at: 26th Annual International Conference of the IEEE Engineering in Medicine and Biology Society. San Francisco, USA, 1-5 September 2004.
  13. Ellozy SH, Carroccio A, Lookstein RA, et al., First experience in human beings with a permanently implantable intrasac pressure transducer for monitoring endovascular repair of abdominal aortic aneurysms, J Vasc Surg, 2004;40:405-12.
  14. Bardy GH, Cappato R, Smith WM, et al., The totally subcutaneous ICD system (The S-ICD), Pacing Clin Electrophysiol, 2002;24:II-578.
  15. Bardy GH, Smith WM, Hood MA, et al., An entirely subcutaneous implantable cardioverter defibrillator, N Engl J Med, 2010;363:36-44.
  16. Maisel WH, Kramer DB, Implantable cardioverter-defibrillator lead performance, Circulation, 2008;117:2721-3.