If you have coronary artery disease (CAD), you can develop cardiac symptoms for two general reasons. First, it is possible to have acute coronary syndrome (ACS), which is a sudden deterioration caused by the formation of a blood clot within a coronary artery. ACS causes unstable angina and myocardial infarctions (heart attacks).
Second, you can have angina caused by the gradual development of partial blockages in a coronary artery. In this case, you can experience episodes of cardiac ischemia during periods of cardiac stress (such as exercise), when your heart muscle is demanding more oxygen than a partially blocked coronary artery can provide. The oxygen-starved (ischemic) heart muscle often causes the painful or uncomfortable sensation which we refer to as angina. Because this kind of angina is due to a blockage that is changing only gradually, and because the angina it produces occurs relatively predictably (that is, during a certain amount of exercise), we call it stable angina.
There are two general approaches to treating stable angina. The first approach is to use so-called "invasive therapy" -- that is, to use either bypass surgery or angioplasty and stenting to relieve specific blockages. You can read here about bypass surgery, angioplasty, and stents.
The second approach is to use medical therapies, also referred to as "non-invasive" therapies, including drugs and other non-surgical approaches. Medical therapies tend to work by reducing the "oxygen demand" of the heart muscle, that is, to reduce the amount of oxygen the heart muscle requires, so that even a partially blocked can deliver an adequate amount. The rest of this article reviews medical therapies for stable angina.
Drug Therapy For Stable Angina
Three categories of drugs are commonly used to lower the oxygen demand of the heart muscle, and to treat or prevent episodes of stable angina. These categories are nitrates, beta blockers, and calcium channel blockers. A few new drugs that are not in any of these categories are also being developed.
Nitrates: Nitrates cause dilation of blood vessels, which reduces stress on the heart muscle, thereby reducing the cardiac demand for oxygen. Read about nitrates in the treatment of angina here.
Beta blockers: Beta blockers reduce the effect of adrenaline on the heart muscle, which reduces the heart rate and the force of heart muscle contraction, thus reducing the oxygen demand of the heart. These drugs also improve survival in some patients with CAD. Read about beta blockers in the treatment of angina here.
Calcium blockers: Calcium blockers reduce the influx of calcium into the heart muscle, also into the smooth muscle of blood vessels. This results in blood vessel dilation, lowers heart rate, and reduces the forcefulness of the heart beat -- all of which lower the oxygen demand of the heart. Read about calcium blockers in the treatment of angina here.
Other anti-anginal drugs: Ranexa (ranolazine) is a new type of anti-angina drug that appears to work by blocking what is called the "late sodium channel" in heart cells which are suffering from ischemia. Blocking this sodium channel improves the metabolism in ischemic heart cells, reducing damage to the heart muscle, and also reducing angina symptoms. You can read more about Ranexa in the treatment of angina here.
How are these drugs used? In general, if you have angina your doctor usually will first give you a beta blocker, and also nitroglycerin (one of the nitrates) to treat any acute episodes you may have. If you still have episodes of angina, your doctor may next give you either a long-acting form of nitrate therapy or a calcium channel blocker (or both). Ranexa, being a new drug, is usually given as a third or fourth drug when necessary -- but some cardiologists have found it to be useful when added earlier. Finally, almost all patients with angina should be placed on aspirin, 81 to 325 mg/day. If your doctor does not do this, you should bring it up yourself.
Other Non-invasive Therapy for Stable Angina
Exercise therapy: Exercise training is an effective method of reducing episodes of angina in people with stable angina. Chronic, low-intensity aerobic exercise (for instance, walking or cycling) "trains" your cardiovascular system and the skeletal muscles to become more efficient. This means you will be able to maintain higher levels of exercise without experiencing angina.
If you have CAD you should usually begin an exercise program under medical supervision. Your doctor may perform a formal stress test to measure your exercise capacity, and to evaluate the level of exercise that begins to produce cardiac ischemia. You will then be given an exercise "prescription," advising you to maintain a heart rate during aerobic exercise that is 60% to 75% of your highest "safe" heart rate, as measured during the exercise test.
A program of aerobic exercise has many benefits in addition to reducing episodes of angina, including promoting weight control, improving vascular health, improving muscle and joint strength, and creating a better mindset for achieving other favorable lifestyle modifications such as diet control and smoking cessation.
Enhanced external counterpulsation (EECP): EECP is a unique treatment for angina that can be quite effective in some patients, but which most cardiologists studiously ignore. You can read more about EECP, the controversy that surrounds it, and whether you should consider discussing it with your doctor, here.
Fraker TD, Fihn SD, on behalf of the 2002 Chronic Stable Angina Writing Committee. 2007 Chronic Angina Focused Update of the ACC/AHA 2002 Guidelines for the Management of Patients With Chronic Stable Angina. J Am Coll Cardiol 2007; 50:2264. Available at: http://content.onlinejacc.org/cgi/content/full/j.jacc.2007.08.002 (Accessed September 4, 2008).