Where it is
On the surface of the heart. The left main coronary artery divides into the left anterior descending (LAD) and circumflex arteries; the right coronary artery (RCA) supplies the right ventricle and, in most people, the inferior wall and the SA and AV nodes.
What it does
Coronary arteries fill mainly during diastole, when the heart muscle relaxes. A fast heart rate shortens diastole and reduces coronary blood flow.
Clinical relevance
- Atherosclerosis narrows the coronaries and causes angina; a clot on a ruptured plaque causes myocardial infarction.
- LAD occlusion causes an anterior MI, sometimes called the "widow maker".
- RCA occlusion often causes inferior MI with bradycardia and heart blocks.
Nursing focus
- Give sublingual nitroglycerin as prescribed: one dose every 5 minutes up to 3 doses; call emergency services if pain does not improve 5 minutes after the first dose.
- Check blood pressure before nitroglycerin and avoid it with phosphodiesterase inhibitors (sildenafil).