Interventional cardiology is a specialty area within the larger field of cardiology. Interventional cardiologists are specially trained doctors who have had one to two years of education and training specifically in the use of catheters – thin, flexible tubes – to perform cardiovascular procedures. These procedures, such as angioplasty and stenting, are performed by guiding tools through the body’s blood vessels. For many patients, these minimally invasive interventional procedures are an appropriate alternative to open surgery.
To learn more about the tools and devices commonly used for interventional procedures, keep reading!
A catheter is a slender, plastic tube that can be threaded into a blood vessel to deliver treatments inside that blood vessel. During a diagnostic angiogram, x-ray dye flows through the catheter into the arteries so that your cardiologist can view images of any blockages in the artery. During angioplasty, a balloon or another device is mounted on the catheter’s tip and guided to the narrowed section of the artery over a guidewire. The device on the catheter is then used to reopen the artery for blood flow.
A guidewire is a long and flexible, fine metal wire used to place balloons or stents. The guidewire is threaded through a blood vessel to the site where treatment will be delivered. A balloon or stent is then fed over the guidewire until it is in the desired position. A guidewire does just as it name implies: it helps your interventional cardiologist guide devices into place.
An angioplasty balloon is attached at the end of a special balloon catheter, the balloon is at one end and can be inflated from the other end outside the body. An interventional cardiologist threads the balloon catheter over a guidewire to the area of the artery that has become blocked with a fatty substance called plaque; the plaque is what is preventing your blood from flowing as it should. The balloon is inflated and deflated several times to push the plaque aside and restore blood flow in the artery.
A cutting balloon is a catheter device with a special balloon tip containing small blades that are activated when the balloon is inflated. Used to treat plaque that is resistant to a traditional balloon, the small blades cut slits in the plaque and then the balloon compresses the fatty matter into the wall of the artery.
A stent is a small, metal mesh tube that is delivered through a catheter to the site of a blocked artery and then permanently embedded within the artery. A stent acts as a tiny scaffold to prop an artery open and prevent it from collapsing or becoming reblocked with plaque. Your doctor may choose from three types of stents: bare metal, drug-eluting or, if you are participating in a clinical trial, bioabsorbable (also known as bioresorbable). The type of stent your doctor uses will depend on the size of the artery, the location of the blockage and other factors specific to your condition, such as whether you have diabetes.
Vascular Closure Devices
After an interventional procedure, your doctor will need to make sure that the puncture site in your skin where the catheters were inserted is fully closed. If your arteries were accessed through the upper leg, your doctor may use a collagen plug or a stitch. If your procedure was performed through an access point in your elbow or wrist, the closure device generally consists of bands that are strapped around the wrist or elbow. The bands may be filled with either air or compounds that stop bleeding.
Sometimes the fatty substance that builds up in arteries (plaque) contains calcium that makes the blockage hard. If a plaque is severely calcified, a standard angioplasty balloon may not be able to cross the blockage and push it to the sides of the artery. Rotational atherectomy is a procedure that can be performed to drill through tough blockages. A tiny rotating cutting device is used to open a narrowed artery and improve blood flow. The pieces of plaque dislodged by the rotational atherectomy device are small enough to be absorbed by the blood stream.
Fractional Flow Reserve (FFR)
FFR is a test used to measure how much blood flow is being restricted by a blockage in an artery. A special, pressure-sensing guidewire is fed through a catheter to the site of the blockage in the artery.
When water flows through a garden hose the flow is driven by the pressure in the tap. If there hose has no obstruction, the pressure at the end of the hose is the same as the pressure at the tap. In a healthy heart artery, the pressure at the end of the artery is the same as at the beginning of the artery (where it comes off of the aorta). But when a blockage reduces flow through the heart artery, or a garden hose, the pressure at the end is reduced proportionate to the restriction. The greater the restriction, the lower the pressure downstream because the flow is reduced. When the FFR wire is placed across the blockage, it measures the pressure in front of and beyond the blockage. If the blood pressure in the artery or beyond the blockage is found to be significantly reduced, then that blockage may be a good candidate for angioplasty and stenting to clear the blockage and prop the artery open.
Intravascular Ultrasound (IVUS)
All ultrasound tests, including IVUS, use sound waves to create images. IVUS is used to gather images of the inside of arteries to find out if a blockage is present, and if so, how serious the blockage is.
During an IVUS test, a catheter with an ultrasound probe at the end is threaded over a guidewire in the artery to the area to be tested. The ultrasound catheter sends out sound waves and receives echoes from the sound waves as they bounce back from the body’s tissues. These echoes are translated by a computer into images of the artery. IVUS is a test that may be performed during an angiogram (also known as cardiac catheterization). Your doctor may use IVUS if the blockages seen with the angiogram appear to be borderline-severe, or if the doctor needs more information about the plaque anatomy.
IVUS is useful because it allows the interventional cardiologist to measure the amount of plaque inside vessels as well as how much much space is available in the artery for blood to flow through. If it is determined that you need angioplasty to treat the blocked artery, IVUS can help with accurate positioning of the balloon and stent.
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|Dr. Morton J. Kern, University of California, Irvine, describes tools and techniques physicians use to make certain a procedure is necessary.
Optical Coherence Tomography (OCT) Imaging
OCT is an imaging tool used to take high-resolution pictures of blood vessel walls. OCT provides interventional cardiologists with detailed images of plaque (cholesterol and other materials that have accumulated in the walls of the artery and can rupture, causing a blood clot to form at the site and block off critical blood flow). Like IVUS, this detailed information about plaque build-up in arteries can help interventional cardiologists determine where best to place stents.
Near-Infrared Spectoscopy (NIRS)
NIRS is a new imaging method that offers interventional cardiologists more information to determine where angioplasty and stenting would be most effective. IVUS, FFR and OCT all can be used to provide information about the structure of the plaque that has built up inside the arteries, including where the plaque is located and how it is affecting blood flow. NIRS does something different: It provides real-time information about the chemical composition of the blockage, which may help interventional cardiologists pinpoint areas that could cause a problem in the near future.
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