Overview of Intravascular Lithotripsy
When you have too much calcium build-up in your coronary arteries (the blood vessels that supply your heart with blood), this can lead to major heart-related problems. This calcium build-up can also make a treatment called percutaneous coronary intervention (PCI) less successful. PCI helps improve blood flow to your heart. But in a person with a lot of calcium build-up, the procedure could face difficulties, including struggling to pass the catheter (a long, thin tube) through the hardened blood vessels, issues with inserting the stent (a small tube to hold the artery open), or increasing the chances of the artery narrowing again. As a result, outcomes are usually worse when PCI is done on people with hardened arteries due to calcium build-up.
Shockwave intravascular lithotripsy (IVL) is a new technique that has evolved from treatments used for kidney and ureter stones. In IVL, a device is inserted in the blood vessel, which releases sound pressure waves to break down the hardened calcium deposits. This makes it easier to put in a stent in the blood vessels. To determine the level of calcium build-up and decide the best treatment plan, it’s crucial to use an imaging technique, such as an ultrasound or optical coherence tomography (a non-invasive imaging test).
Clinical studies like the Disrupt Peripheral Arterial Disease (PAD) studies, the Disrupt Below the Knee (BTK) study, and the disrupt Coronary Artery Disease studies have already shown that IVL can be safely and feasibly performed to treat hardened blood vessels otherwise known as calcified coronary arteries. Current ongoing studies, such as the Disrupt PAD III study, and the Disrupt CAD III study, are looking further into this technique’s safety and effectiveness.
Anatomy and Physiology of Intravascular Lithotripsy
The inability of the tiny muscles in our blood vessels to work properly can often lead to the build up of calcium within the blood vessel walls. This happens when tiny particles, called microvesicles, are released and disrupt the inhibitors that regulate the process of mineralization, leading to the accumulation of calcium outside the cells found within the inmost and middle layers of a blood vessel. While there have been instances of calcium collecting inside cells, what this exactly means for the body isn’t well understood at the moment.
Computed tomography coronary angiography (CCTA) is a non-invasive scanning procedure that can accurately detect any build up of calcium within the inner and middle layers of the heart’s blood vessels.
Why do People Need Intravascular Lithotripsy
Intravascular lithotripsy (IVL) is a technique currently used to alter hard, calcified plaque within the heart’s innate coronary and peripheral arteries. Calcified plaque is the build-up of fats and other substances on the interior walls of the blood vessels. Smoothing down these plaques helps improve blood flow through these vessels.
There is increasing evidence that this method could also be helpful in performing interventions on the large blood vessels of the aortic arch (“aortic arch vasculature”), the lower part of the aorta (the body’s main blood vessel), and the iliofemoral vessels which supply blood to the legs and lower part of the body. This would assist in making large bore access, a procedure to insert large tubes or devices into these blood vessels for treatment.
Some of these treatment methods include procedures like transcatheter aortic valve replacement (TAVR), endovascular aneurysm repair (EVAR) and thoracic endovascular aortic repair (TEVAR). TAVR is a less invasive procedure to replace a narrow heart valve; EVAR and TEVAR are methods to repair aneurysms, which are abnormal bulges in the walls of the aorta.
The use of IVL in other unique situations like folks with chronic occlusion (complete blockage of a blood vessel), unprotected left main calcified stenosis (narrowing of the main left artery of the heart due to hard plaques) and under-expansion of stents due to calcium-related issues is currently being studied.
When a Person Should Avoid Intravascular Lithotripsy
According to the makers of a certain medical device, doctors should not use it if they can’t get a very thin wire (0.014-inch guidewire) through the blockage in the artery. Also, they advise against trying the procedure on people who have had a specific problem happen with their heart stents, called coronary in-stent restenosis (ISR). This is when the artery narrows again after putting in a stent, which is a tiny tube that keeps the artery open. However, it’s worth noting that there have been instances before where the device was used successfully for this condition even though it wasn’t initially designed for it.
Equipment used for Intravascular Lithotripsy
The Intravascular Lithotripsy (IVL) system uses a special single-use catheter with a built-in ultrasound part situated around a tiny, thin guidewire. This catheter is encased in an inflatable balloon, which has a fixed length of 12 millimeters (mm), but is available in different widths from 2.5 to 4.0mm. These different sizes allow the catheter to cross spaces within blood vessels that measure from 0.043″ to 0.046″.
This IVL system also includes a portable device that provides energy to generate ultrasound waves. Inside the balloon are pairs of markers visible under X-ray and regular transmitters that make these waves. These waves act like little hammers, creating tiny cracks in hardened plaque deposits in blood vessels. This action improves the flexibility of the blood vessel while preserving the structure of its walls, making it easier to open the blood vessel with the balloon at lower pressure levels than are often required with other methods.
Who is needed to perform Intravascular Lithotripsy?
A cardiologist, a special type of heart doctor, can carry out a certain procedure without needing any extra, specific training. This means they’ve already learned all the necessary skills during their broad education and experience in heart healthcare.
Preparing for Intravascular Lithotripsy
When doctors need to use a balloon for treatment inside your blood vessels, they first have to figure out the right size for it. They do this by examining the width of your vessel where the balloon will be inserted. To find the correct balloon size, they typically use a 1 to 1 ratio based on your vessel’s width. Most times, a device called a 6 French (Fr) system is used to insert the balloon. However, for people with smaller arteries, a 5 Fr system might be used instead. Special imaging tools are then used to ensure the balloon’s size is accurate and to understand the structure of any calcium deposits in your arteries.
How is Intravascular Lithotripsy performed
The medical device is filled with air until it reaches pressure four times higher than the pressure at sea level. It’s then pushed through the target plaque within the body. After this, it sends out ten rounds of pulsing sound waves during each cycle with the help of internal transmitters. Following this, the balloon-like device is deflated, letting any created bubbles disperse safely within your body. This entire process is then repeated at least twice for every target area that is 12 millimeters in size.
After the process, two types of imaging techniques – Intravascular Ultrasound (IVUS) and Optical Coherence Imaging (OCT) – may be performed. IVUS is a medical imaging method that uses sound waves to see inside blood vessels. OCT is another imaging test that creates detailed images of the tissues inside the body. These techniques can help identify where the calcium has fractured and assess the success of the procedure.
Possible Complications of Intravascular Lithotripsy
During the management of hardened heart arteries, doctors might use a therapy called IVL, which is similar to other treatments that break down hard deposits in the body. Some theory suggests this could lead to a change in the balance of electric charge within cells, but we still lack enough patient data to confirm this. There’s also a potential risk of the heart artery tearing. This could be caused by the low-pressure expansion of a balloon in the artery or the high-energy sound waves used in the treatment. However, it’s important to note that such complications have been rare in the clinical trials carried out so far.
What Else Should I Know About Intravascular Lithotripsy?
Procedures involving the heart’s blood vessels can sometimes be complicated by hard, calcified lesions, or plaques. Traditionally, doctors treated these hard plaques by inflating high-pressure balloons within the arteries and possibly using a technique called atherectomy to remove the plaque. However, these methods didn’t always work on all plaques.
A newer method called Intravascular Lithotripsy (IVL) offers several benefits over previous balloon-based procedures. First off, doctors who are already performing heart surgeries don’t need extra training to use IVL. Secondly, the pressure used to open the balloon is lower, lowering the chances of injuring the blood vessels. Additionally, it is effective in reducing potential blockages downstream, targets plaque all around the artery wall, and minimizes bias while threading a thin, flexible wire through the arteries for guidance.
IVL shows promise in effectively causing breaks in most calcified plaques in patients who need heart artery revascularization, a procedure to restore blood flow. It’s also associated with successful outcomes and very few complications. By allowing more effective artery widening, using IVL could potentially improve the effectiveness of stent expansion. A stent is a small, mesh tube that’s used to treat narrow or weak arteries.
