A balloon catheter is a type of "soft" catheter with an inflatable "balloon" at its tip which is used during a catheterization procedure to enlarge a narrow opening or passage within the body. The deflated balloon catheter is positioned, then inflated to perform the necessary procedure, and deflated again in order to be removed.
Balloon catheters used in angioplasty are either of Over-the-Wire(OTW) or Rapid Exchange(Rx) design. When a balloon catheter is used to compress plaque within a clogged coronary artery it is referred to as a plain old balloon angioplasty or POBA. Balloon catheters are also utilized in the deployment of stents during angioplasty. Balloon catheters are supplied to the cath lab with a stent premounted on the balloon. When the cardiologist inflates the balloon it expands the stent. When the cardiologist subsequently deflates the balloon the stent stays behind in the artery and the balloon catheter can be removed. Stents that are used in conjunction with a balloon catheter are known as balloon expandable stents.
A coronary stent is a stent placed in a coronary artery to treat coronary heart disease as part of a procedure called percutaneous coronary intervention (PCI). Similar stents and procedures are used in non-coronary vessels eg in the legs in peripheral artery disease.
Treating a blocked ("stenosed") coronary artery with a stent follows the same steps as other angioplasty procedures with a few important differences. The interventional cardiologist nterventional cardiologist uses angiography to assess the location and estimate the size of the blockage ("lesion") by injecting a contrast medium through the guide catheter and viewing the flow of blood through the downstream coronary arteries. Intravascular ultrasound (IVUS) may be used to assess the lesion's thickness and hardness ("calcification"). The cardiologist uses this information to decide whether to treat the lesion with a stent, and if so, what kind and size. Drug eluting stents are most often sold as a unit, with the stent in its collapsed form attached onto the outside of a balloon catheter. Outside the US, physicians may perform "direct stenting" where the stent is threaded through the lesion and expanded. Common practice in the US is to predilate the blockage before delivering the stent. Predilation is accomplished by threading the lesion with an ordinary balloon catheter and expanding it to the vessel's original diameter. The physician withdraws this catheter and threads the stent on its balloon catheter through the lesion. The physician expands the balloon which deforms the metal stent to its expanded size. The cardiologist may "customize" the fit of the stent to match the blood vessel's shape, using IVUS to guide the work. It is critically important that the framework of the stent be in direct contact with the walls of the vessel to minimize potential complications such as blood clot formation. Very long lesions may require more than one stent -- this result of this treatment is sometimes referred to as a "full metal jacket".
The procedure itself is performed in a catheterization clinic ("cath lab"). Barring complications, patients undergoing catheterizations are kept at least overnight for observation.
Dealing with lesions near branches in the coronary arteries presents additional challenges and requires additional techniques