A wireless pacemaker that can be fitted inside the left ventricle and mimic physiological cardiac tissue stimulation for cardiac resynchronisation therapy, CRT.
1.What is it?
The main component is a receiver electrode the size of a grain of rice which is the first endocardial pacemaker.¹ This ensures the electrical stimulation is closer to our natural SA node to AV node pacemaker as conventional CRT devices are placed on the outside of the heart, stimulating the left ventricle from the outside in which is physiologically unnatural. ² ³
2. Why is it important?
Over 7 million people in the UK live with coronary heart disease (CHD) leading to over 150, 000 CHD related deaths per year. Hence, CHD is the leading cause of death in the UK, with the more deprived areas being the hardest hit.4Currently, CRT is unresponsive in 30- 40%5 of patients due to:
- side effects with pacemaker wires leading to thromboembolism and mitral valve mechanical defects
- complex coronary sinus anatomy which prevents pacemaker fitting
- other complications
In comparison, WiSE CRT5 shows:
- 97% cardiac resynchronisation within 1 month of surgery
- 85% patients with continued clinical benefits post 6 month follow up
Images: BHF CVD Factsheet
3. How does it work?
- a subcutaneous pulse generator over the ribcage sends signals via ultrasound waves to the tiny receiver electrode in the left ventricle
- the receiver electrode converts the energy to generate an electrical pulse to pace the heart
- this regulates irregular cardiac rhythms as required
As seen in the image above, there are 4 components in total but the co- implant, transmitter and battery are subcutaneous, only the receiver electrode is within the left ventricle of the heart.
Although they found 84.8% experienced continued clinical benefit at their 6 month follow up, serious adverse effects were experienced by 8.6% patients within 24 hours and 22.9% between 24 hours and 1 month of the surgical fitting.
Overall, results from the SELECT-LV study on 35 patients show5:
- increased left ventricular ejection fraction, LVEF
- decreased left ventricular end diastolic and systolic volume, LVEDV/ LVESV
- reduction in QRS duration
Therefore, this study concluded this is a feasible alternative to move towards wireless pacemakers with a clear emphasis on further larger studies to better evaluate risk factors and long term clinical side effects.
4. The future
As electrical activity is a natural form of communication in many areas of our body, naturally the next steps are to regulate stimulation in:
- digestive system
The Cardiac Rhythm management market is also large enough to see further releases.
5. Who is involved?
1. van Deursen C, van Geldorp I, Rademakers L. et al. Left Ventricular Endocardial Pacing Improves Resynchronization Therapy in Canine Left Bundle-Branch Hearts. Circ Arrhythmia Electrophysiol. 2009; 2: 580-7.
2. Bracke FA, van Gelder BM, Dekker LRC, terWoorst JF, Teijink JA. Left Ventricular Endocardial Pacing in Cardiac Resynchronisation Therapy: Moving from Bench to Bedside. Neth Heart J. 2012; 20(3): 118–24.
3. Bordacher P, Derval N, Ploux S, et al. Left Ventricular Endocardial Stimulation for Severe Heart Failure. J Am Coll Cardiol. 2010; 56: 747–53.
4. World Health Organisation, The Top 10 Causes of Death
5. Reddy V, Viller M, Neuzil P, Sogaard P, Butter C, Seifert M et al. Cardiac Resynchronisation Therapy With Wireless Left Ventricular Endocardial Pacing. Journal of the American College of Cardiology. 2017; 69 (17): 2119- 2129.