Many Americans will experience a heart attack (acute coronary syndrome) at some point in their lives. The degree of severity, however, may vary. Some can be treated just medically while others require more invasive intervention. Technology has advanced such that doctors can address significant coronary artery disease at its core. They can do it as a percutaneous coronary intervention (PCI) or as a surgical procedure.
Coronary Artery Angiography
High-risk cardiac patients need to have their coronary arteries visualized. This is done with a coronary artery angiogram. The patient is first taken to a cardiac catheterization lab in a hospital where he or she is draped from head to toe. The drape has a small window that goes over the thigh. This allows the interventional cardiologist to inject the area with local anesthetic, make a small incision, and insert a wire into the femoral artery. This wire is threaded into the vessel, through the iliac arteries, and up the aorta until it reaches the heart.
The cardiologist does this with fluoroscopic guidance. He or she has the foot on a pedal to shoot a series of x-ray images in rapid succession, almost like a video. This allows the cardiologist to see where the wire is. To minimize radiation to the patient, fluoroscopy is activated only when needed, not on a continuous basis. The wire will then need to be maneuvered into the coronary arteries that start from the base of the aorta.
Afterwards, a tube (catheter) is inserted over the wire and threaded into the same femoral artery. The purpose of the wire is to act as a guidewire. From this point on, any tool threaded to the heart follows along this guidewire like a rail. Each tool is designed like two tubes stuck alongside each other. One tube goes over the wire, and by threading this tube towards the heart, it brings the other tube with the tool along with it.
The first catheter that goes to the heart introduces dye into the coronary arteries. At this time, fluroscopic images are taken to visualize them. The cardiologist can see the vessels that have narrow segments due to atherosclerosis or vessels that are cut off at the end because of complete blockage. The patient then proceeds to either angioplasty with stenting or surgical grafting.
Percutaneous Transluminal Coronary Angioplasty
Balloon angioplasty involves threading a catheter with a deflated balloon at its end. The balloon has a metallic stent wrapped around it. When threaded to the diseased coronary artery along the guidewire, the balloon is inflated with a mixture of saline and contrast material, allowing the cardiologist to see the inflation occur on fluoroscopy. The artery is widened and the stent is placed in the process. The stent stays along the inner surface of the artery to hold it open. Over time, healing takes place so that tissue can grow right over the stent.
Restenosis, or renarrowing, of the stented coronary artery is always a possible complication. It can happen with the stent recoiling and collapsing on itself or with overgrowth of the tissue over the stent. In an effort to reduce restenosis from the latter, some stents have been coated with drugs (e.g., paclitaxel, sirolimus) that counter cellular growth. However, multiple studies have recently shown that drug-eluting stents have rates of restenosis that are not better, and may in fact be worse, than bare-metal stents. This is a topic that continues to be discussed in the medical community, but for now, experts have a reserved opinion about drug-eluting stents.
Coronary Artery Bypass Grafting
Coronary artery bypass grafting is a surgical operation performed by a cardiothoracic surgeon. The surgeon removes either one of the saphenous veins in the patient's legs or one of the internal thoracic arteries in the chest. This vessel is used as a graft. One end of this graft is attached to the base of the aorta, and the other is attached to the narrowed coronary artery past the site of obstruction.
Overall, this is a major high-risk surgical operation. The sternum in the chest has to be sawed open to access the heart and must be held closed post-operatively with wires. Plenty of time for recovery should be expected. Even so, this is a beneficial option for patients, particularly those with severe coronary artery disease.
Factors in Treatment Decision
Whether a patient receives percutaneous transluminal coronary angioplasty (PTCA) or coronary artery bypass grafting (CABG) depends on many factors. Some of them are as follows:
- Number of Vessels: PTCA is good if only one coronary artery is diseased. With involvement of two or more vessels, CABG is preferred because it already takes enough time to thread just one balloon catheter for PTCA.
- Tortuosity of Vessels: If the artery is straight enough, the cardiologist should be able to maneuver a balloon cathether into it and perform PTCA. Otherwise, CABG is the better option.
- Length of Narrowing: PTCA works only if the narrowing is in a portion of the artery since the stent is only so long. An artery that is narrow along most of its length is better corrected with CABG.
- Degree of Narrowing: In the most severe case, a coronary artery is 100% occluded. PTCA may still be attempted, but if the balloon catheter cannot pass through, this option is discontinued in favor of CABG.
- Arteries to Left Ventricle: The left ventricle of the heart is vital because it pumps blood to the whole body. If the coronary arteries involved supply the entire left side of the heart (e.g., left main coronary artery), CABG is the treatment of choice given how critical it is to save it.
References
- Teirstein, Paul S. "Percutaneous Coronary Interventions." Cecil Textbook of Medicine. 22nd ed. Ed. Lee Goldman and Dennis A. Ausiello. Philadelphia: Saunders, 2004. 424-428.
- Lytle, Bruce W. "Surgical Treatment of Coronary Artery Disease." Cecil Textbook of Medicine. 22nd ed. Ed. Lee Goldman and Dennis A. Ausiello. Philadelphia: Saunders, 2004. 428-431.
- MedicineNet.com - Coronary Balloon Angioplasty and Stents
