Coronary Circulation Asadullah Syed #307

Coronary pertaining to the heart. Circulation movement of an object or substance through a circular course so that it returns to its starting point, such as the circulation of blood through the circuitous network of arteries and veins. Coronary circulation is the circulation of blood in the blood vessels of the heart muscle. The blood fills the chambers of the heart, the muscle tissue of the heart (the myocardium) is so thick that it requires coronary blood vessels to deliver blood deep into it. The vessels that deliver oxygen-rich blood to the myocardium are known as coronary arteries. The vessels that remove the deoxygenated blood from the heart muscle are known as coronary veins.

There are two major coronary arteries: the right and the left. (the first branch) These two arteries branch out of the aorta immediately after the aortic valve. The right coronary artery splits into the marginal branch, which feeds blood into the right ventricle, and the posterior interventricular branch, which supplies the left ventricle. The left coronary artery is notably larger than the right coronary artery because it feeds the left heart, which, as a result of it's more powerful contractions, requires a more vigorous blood flow. The left coronary artery splits into the anterior interventricular branch and a circumflex branch. The anterior interventricular branch runs towards the apex of the heart, providing blood for both of the ventricles and the ventricular septum. The circumflex branch, on the other hand, follows the groove between the left atrium and the left ventricle, providing blood supply to both of these chambers until it reaches and joins with the right coronary artery in the posterior of the heart.

The coronary arteries that run on the surface of the heart are called epicardial coronary arteries. These arteries, when healthy, are capable of auto regulation to maintain coronary blood flow at levels appropriate to the needs of the heart muscle myocardium. The coronary arteries are classified as "end circulation“. They represent the only source of blood supply to the myocardium: there is very little redundant blood supply

Cardiac Cycle The cardiac cycle is the sequence of events that occur when the heart beats. There are two phases of this cycle: ◦Diastole - Ventricles are relaxed. ◦Systole - Ventricles contract. ◦During the diastole phase the atria and ventricles are relaxed and the atrioventricular valves are open. ◦De-oxygenated blood from the superior and inferior vena cava flows into the right atrium ◦The open atrioventricular valves allow blood to pass through to the ventricles. ◦The SA node contracts triggering the atria to contract. ◦The right atrium empties its contents into the right ventricle. ◦The tricuspid valve prevents the blood from flowing back into the right atrium.

What is collateral circulation? Collateral circulation is a network of tiny blood vessels, and, under normal conditions, not open. When the coronary arteries narrow to the point that blood flow to the heart muscle is limited (coronary artery disease). collateral vessels may enlarge and become active. This allows blood to flow around the blocked artery to another artery nearby or to the same artery past the blockage, protecting the heart tissue from injury.

Coronary Artery Disease Coronary artery disease (CAD), also called coronary heart disease, is a condition in which plaque builds up inside the coronary arteries. Plaque is made up of fat, cholesterol, calcium, and other substances found in the blood. When plaque builds up in the arteries, the condition is called atherosclerosis. Plaque narrows the arteries and reduces blood flow to your heart muscle. It also makes it more likely that blood clots will form in your arteries. Blood clots can partially or completely block blood flow. When your coronary arteries are narrowed or blocked, oxygen-rich blood can't reach your heart muscle. This can cause angina or a heart attack.

Symptoms Angina is usually felt as: pressure, heaviness, tightening, squeezing, or aching across the chest, particularly behind the breastbone.

Treatment for Angina Nitroglycerin is the drug most often used. It mainly relaxes the veins and relaxes the coronary arteries a little. By relaxing the veins, it reduces the amount of blood that returns to the heart and eases the heart's workload. By relaxing the coronary arteries, it increases the heart's blood supply. Invasive techniques that improve the heart and the heart's blood supply also may be used. One of these is percutaneous transluminal coronary angioplasty. It's also known as PCI, PTCA, angioplasty, balloon dilation or balloon angioplasty. In it, a thin, flexible plastic tube (catheter) with a balloon is inserted into an artery and advanced to the blockage. Then the balloon is inflated, squeezing open the fatty plaque deposit. Then the balloon is deflated and the catheter is withdrawn. Often a stent is also placed to hold the artery open. Two additional techniques used to reduce coronary blockages are laser angioplasty and atherectomy. In laser angioplasty, a catheter with a laser on its tip is used to open the blockage. In atherectomy, a catheter has a rotating shaver on its tip to cut away the plaque. These techniques also may be accompanied by stent placement. You also may need other medicines to treat angina. These medicines may include beta blockers, calcium channel blockers, ACE inhibitors, oral antiplatelet medicines, and anticoagulants. These medicines can help: ◦Lower blood pressure and cholesterol levels ◦Slow the heart rate ◦Relax blood vessels ◦Reduce strain on the heart ◦Prevent blood clots from forming

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