Before the heart can pump blood to supply the body with oxygen and other nutrients, it has to supply its own needs first. And this is where the coronary arteries take in charge. They are responsible for supplying the oxygenation needs of the heart. The normal coronary blood flow is about 225 ml/min.
What are the major coronary arteries?
There are two major coronary arteries that you should know:
- Left coronary artery (LCA) supplies the left lateral and anterior portions of the left ventricle. LCA is also divided in two branches known as the left anterior descending artery and the left circumflex artery.
- Right coronary artery (RCA) supplies most of the right ventricle and posterior part of the left ventricle. It also supplies the SA node and the AV node.
What causes coronary artery disease?
Atherosclerosis (hardening of the arteries) is one of the major factors that cause coronary artery disease. The pathophysiology of this condition starts when there is nonspecific injury to the arterial wall or what we call “endothelial injury”. The injury can be caused by different factors like cigarette smoking, hypertension, stress, and unhealthy diet. The injury attracts lipids like low density lipoprotein (LDL) and very low density lipoprotein (VLDL).
When lipids accumulate in the site of injury, oxidized lipids attracts monocytes and is transformed to macrophages. Macrophages ingest lipids, giving them a foam-like appearance and known to be called as “foam cells”. When foam cells die, they release lipid content, forming lipid pools in the intima. This is start when the plaques or atheromas begin to form, and arteries begin to harden.Over time, when plaques continue to thicken, it narrows and obstructs the blood flow creating different kinds of problems like Acute Coronary Syndrome and Acute Myocardial Infarction.
What are the managements for CAD?
Managing an individual’s cholesterol and triglyceride levels can reduce the risk for developing coronary artery disease.
Therefore, it is a nurse’s responsibility to educate patients how to decrease or eliminate modifiable risk factors of CAD by instructing them to follow a healthy balanced diet, engage in regular exercise, eliminate cigarette smoking, and manage hypertension.
However, if blood cholesterol levels and triglyceride levels are not normalized by lifestyle changes, lipid-lowering medications are prescribed.
- HMG-CoA Reductase Inhibitors or known as the “statins”
(Atorvastatin, Simvastatin, Rosuvastatin)
These are lipid-lowering agents used to reduce cholesterol or lipids (LDL) to reduce the risk of heart attack and stroke.
- Bile Acid Sequestrants
Also used to increase the clearance of cholesterol, thus decreasing LDL and cholesterol in the blood.
- Omega-3-acid ethyl esters
This medication is used to inhibit the synthesis of triglycerides, and usually combined with other medications.
What are the interventions for CAD?
- Percutaneous Transluminal Coronary Angioplasty
The purpose of PTCA is to improve blood flow by compressing the plaque using a balloon tipped catheter.
How it is done:
This procedure is usually performed in hospitals with cardiac catherization laboratory. Through the femoral artery of the patient, a special catheter is inserted with the help of a guide wire, up to the aorta until it reaches the coronary arteries. The procedure is usually done with intravascular ultrasonography (IVUS); where computers and transducers are used to visualize blood vessels, assess lesions, and plaques.
When the catheter is in place to the affected artery, the balloon is inflated. The inflation of the balloon compresses plaque, thus improve the coronary blood flow circulation. However, there is also a risk that the patient may experience reoclussion or restenosis after PTCA, thus the procedure may need to be repeated.
Several complications can also place the patient at risk with this procedure. Rupture of the artery, cardiac dysrhythmias, stroke, bleeding, and acute myocardial infarction are few examples of complications.
- Coronary Stenting
Stenting is usually done during percutaneous intervention to keep the coronary arteries open and avoid the risk of acute closure of the vessel. The effect of coronary stenting is long-term comparing to PTCA.
How it is done:
The procedure is usually the same with percutaneous transluminal angioplasty except that when the balloon catheter tip is inflated, and the balloon is withdrawn, a stent is purposely left in place to maintain the opening of the artery and restore the normal blood flow.
- Coronary artery bypass grafting
CABG is done especially for patient with one or more coronary arteries occlusion or narrowing, and if patient is not responding well to medical management.
How it is done:
This is a surgical procedure that creates diversion or a graft distal to the occluded artery using patient’s own blood vessel (internal mammary or saphenous vein). Through this, the blood can now bypass the occluded artery and coronary circulation is improved.
Coronary Artery Disease Pathophysiology
- Deglin, J. and Vallerand, A. 2007. Davis’s Drug Guide for Nurses. Davis Company. 10th edition.
- Guyton, A. & Hall, J. (2006). Textbook of Medical Physiology. Elsevier Saunders, Philadephia. 11th edition.
- Schilling McCann, J. (2007). Lippincott manual of nursing practice series: Pathophysiology. Lippincot Williams & Wilkins, Philadelphia.
- Silvestri, L. (2008). Comprehensive Review for the NCLEX-RN Examination. Saunders Elsevier. 4th edition.
- Smeltzer, S., Bare, B., Hinkle, J., Cheever, K. (2010). Brunner & Suddarth’s Textbook of Medical-Surgical Nursing. Lippincott Williams & Wilkins. 12th edition