The heart has three main coronary arteries (one right and two left coronary arteries). These arteries supply the blood for the actual heart muscle itself. They receive 4% of all the blood, but capture 10% of all the oxygen in the body. Cardiac muscle cells have a limited capacity for anaerobic metabolism. They cannot go very long anaerobically otherwise the cardiac tissue will die.
Angina Symptoms: When oxygen demand exceeds oxygen delivery, the patient complains about chest pain. They describe this pain as something is crushing them or some say it’s a stabbing pain. Some say pain is radiating to the left shoulder, up the neck, etc.
- Atherosclerosis: Usually there is atherosclerosis in these coronary arteries (the formation of plaque; hardening of the artery) which decreases the diameter of the arteries, decreasing the volume of the blood going through, decreasing the amount of oxygen the cardiac muscle is getting. As a result the demand is exceeding the delivery. This is the primary cause and most the angina is atherosclerotic but there are other causes.
- Vasospasm: The smooth muscle around the coronary artery is having a spasm, causing the diameter of the coronary artery to shrink, decreasing the delivery of oxygen. The cause of that muscle spasm is calcium, so the treatment is going to be a calcium channel blocker.
- Thyrotoxicosis (overactivity of the thyroid)
Anginal Precipitating Factors
These are all reasons for someone who is prone to an anginal attack, to have one occur.
- Exercising (putting more demand on the heart)
- Intense emotional stimuli
- Extremes of heat and cold
- Medication: sympathetic drugs (sympathomimetics cause the drugs to speed up), anorectic agents, antidepresseants
Therapeutic Options for Angina
Invasive Angioplasty Surgery
In angioplasty, at the end of the catheter is a balloon and they pump air into the catheter and the balloon expands and the plaque gets squeezed to the sides and the amount of blood that can flow through increases. This is a risky procedure.
What can go wrong with this procedure? A part of the plaque breaks off and it gets stuck in a much smaller part of the coronary artery and they could have a heart attack. There is always a nearby operating room available during this procedure so that in case anything goes wrong, they would do a coronary artery bypass graft (replace the artery with a vein from another part of the body).
The success rate is good in the short term but angioplasty works only for about 6 months. So they add a surgical stent, a cylindrical wire-like mesh, to help keep the vessel open. The stents are now impregnated with a chemical that doesn’t allow plaque to adhere to it and that’s been having good success.
In this case we use drugs. These drugs either…
1. Decrease cardiac workload, or
2. Reverse vasospasm.
No matter what drug we talk about here, none of them treat the underlying problem.