A ground-breaking new technology is now available at Royal Brompton & Harefield Hospitals Specialist Care, which can fracture problematic calcium in the walls of coronary arteries, enabling optimal stent expansion and improved blood flow to the heart.
Coronary artery calcification (CAC) can result in increased stiffness, preventing arteries from dilating to their full capacity and so reducing oxygen supply to the heart. Left untreated, this can greatly increase the risk of future adverse cardiovascular events.
CAC is age and gender-dependent, with 10-15% of patients with significant coronary stenosis having enough calcium to prevent optimal plaque dilatation and stent expansion. Diabetes mellitus, chronic kidney disease and a high BMI may also increase the risk of calcification.
Calcification prevents existing coronary interventions from working
There is a range of percutaneous coronary interventions (PCI) available to widen narrowed arteries and enable the placement of stents to improve blood flow. However, calcification can limit the success of existing procedures.
For example, the force applied by balloon angioplasty to vessel walls may not be sufficient to fracture calcium and enable a stent to be fully expanded – reducing its success in preventing restenosis. The calcification may also increase the risk of vessel dissection and acute vessel closure.
Other PCI techniques – orbital and rotational atherectomy – are available to specifically remove CAC. They scrape away hard, superficial calcified tissues in coronary arteries whilst sparing softer elastic tissues, to increase blood vessel compliance for a stent to be fully expanded. However, the techniques create fragments which can induce slow blood flow, cause an embolism further downstream and result in peri-procedural myocardial infarction.
An innovative solution using an old technology
With existing PCI techniques limited in their ability to safely and successfully dilate calcified coronary arteries, an entrepreneurial team of three came together to develop an innovative device to tackle calcification with a technology that has long existed.
In 2007, Daniel Hawkins, a businessman, and John Adams, an electrical engineer (who worked on early pacemakers), were working at a medical incubator to service unmet medical needs with new technology. It is here they discovered the application of lithotripsy in tackling problematic calcium in the cardiovascular system.
Lithotripsy has been used for over 30 years in medicine to safely fragment kidney and gallbladder stones, facilitating their excretion without harming soft tissues. An electrical current is used to generate a spark which vapourises fluid to produce powerful pressure waves that travel safely through the body’s soft tissues at the speed of sound, breaking up denser kidney stones.
Teaming up with Stanford University cardiologist and bioengineer, Professor Todd Brinton, they experimented with a new lithotripsy device they developed to tackle CAC. They discovered their device could crack calcium-rich egg shells whilst leaving their membranes intact – which is much like the endothelium of a blood vessel. They therefore had a proof-of-concept for cardiovascular applications.
Fast-forwarding to today and after several successful international clinical trials, Shockwave Intravascular Lithotripsy (IVL) is now available as a PCI to safely and successfully treat patients with moderate-to-severe CAC.
The device is composed of a fine 0.014-inch guide wire with an array of lithotripsy emitters enclosed in an integrated balloon. This enables clinicians to use the same minimally-invasive technique as balloon angioplasty to get directly to the site of calcified lesions and transmit the sonic pressure waves to the blood vessel wall, to fracture calcium.
“The technology enables the coronary artery to become much more compliant before dilation – much more than is possible with other methods. This allows us to fully expand a stent, to successfully increase blood flow to the heart,”
- Professor Carlo Di Mario, consultant cardiologist and professor of cardiology.
Professor Di Mario was the Co-Principle Investigator of the Disrupt CAD I and II study trialling the new Shockwave IVL technology on 160 patients. As such, Royal Brompton Hospital was the first in Europe to conduct coronary IVL in 2015 and Professor Di Mario treated most patients during both studies. Dr Jonathan Hill, also a consultant cardiologist, is now following his steps, becoming Co-Principle Investigator of the Disrupt CAD III trial, a larger US and European lithotripsy study which has already completed recruitment of its patients.
“The results of these studies demonstrated that the procedure is safe and effective for patients with moderate-to-severe calcification. Also, it has quick recovery times, with the patient able to go home the following day. It really is a game-changer in the treatment of narrowed coronary arteries,”
“I recommend any patient with angina or silent ischaemia, and moderate-to-severe CAC, be referred for treatment with Shockwave IVL.”
- Professor Di Mario.
How shockwave intravascular lithotripsy works
|The IVL catheter is delivered across a calcified lesion over an 0.014” wire and the integrated balloon is expanded to 4 atm to facilitate efficient energy transfer.||An electrical discharge from the emitters vaporises the fluid within the balloon, creating a rapidly expanding and collapsing bubble that generates sonic pressure waves.||The waves create a localised field effect that travels through soft vascular tissue, selectively cracking intimal and medical calcium within the vessel wall.||After calcium modification, the integrated balloon may subsequently be used to dilate the lesion at low pressure in order to maximise luminal gain.|
Dr Hill specialises in interventional cardiology, vardiovascular risk assessment and cardiac CT.
Consultant cardiologist, Professor of cardiology
Professor Di Mario specialises in coronary and structural (valvular) interventional cardiology.