What do the drugs you were prescribed do?
The number one goal after a heart attack is to prevent another one. If the pump function of the heart is reduced after a heart attack, the second goal is to improve it. The key to success is strict control of risk factors, including blood pressure, cholesterol, diabetes, smoking and other lifestyle behaviours. Drug treatment is one of the cornerstones to achieving risk factor control.
Blood thinners
After a heart attack, it is mandatory to take antiplatelet drugs. These prevent new clots forming in the coronary arteries or within a stent (a tube inserted into a blocked artery to restore blood flow). Usually, a combination of two antiplatelet drugs is given for 12 months including low-dose aspirin (75 to 100 mg/day) and a P2Y12 inhibitor (ticagrelor, prasugrel or clopidogrel). As the primary function of antiplatelets is to inhibit clot formation, they increase the risk of bleeding. But the benefits largely outweigh the risks. It is extremely important not to stop taking these medications, even for a single day, unless advised by your cardiologist. Aspirin is often recommended as a lifelong therapy. The duration of P2Y12 inhibitor use depends on your risk for another heart attack. If you also have atrial fibrillation, a different blood thinner (oral anticoagulant) may be prescribed by your cardiologist instead of antiplatelets.
Proton pump inhibitors
If you are at high risk of gastrointestinal bleeding, your cardiologist or family doctor may prescribe a proton pump inhibitor to protect your stomach when you take two blood thinners.
Cholesterol-lowering drugs
To slow the progression of atherosclerosis in your arteries, your cholesterol levels need to be reduced by 50% or more. To achieve this, statins are the drugs of first choice. Statins decrease cholesterol production in the liver, shrink plaques in the arteries, and lower the risk of another heart attack. Possible side effects include muscle pain and elevated liver enzymes in the blood but they are usually harmless. Negative stories about statin therapy have been in the news, but the reality is that stopping statin treatment dramatically increases your risk of another heart attack. If your cholesterol levels are very high, your cardiologist may choose to add ezetimibe, which inhibits absorption of cholesterol by the intestine, or a PCSK9 inhibitor injection, which shifts more cholesterol from the blood into the liver.
Beta blockers
Beta blockers protect your heart from the harmful effects of adrenaline. They reduce heart rate, blood pressure, and the heart’s use of oxygen. If your heart’s pump function is reduced, they help avoid further deterioration. If heart rate is lowered too much you may feel dizzy. Common additional side effects include headache, cold hands and feet, fatigue and trouble sleeping. Different beta blockers have distinct side effects so speak to your cardiologist to find the one that is right for you.
ACE inhibitors and angiotensin receptor blockers
Angiotensin-converting enzyme (ACE) inhibitors reduce production of angiotensin II, an enzyme that narrows the blood vessels, while angiotensin receptor blockers (ARBs) inhibit its function. These effects help the vessels to widen and relax, improving blood flow and reducing blood pressure. In addition, these drugs improve the pump function of the heart if it was reduced by the heart attack. The most common side effect of ACE inhibitors is a dry cough, which can prompt switching to an ARB. If you already have normal blood pressure, you will need a modified dose of an ACE inhibitor or ARB.
MRAs
Mineralocorticoid receptor antagonists (MRAs), including spironolactone and eplerenone, should be used on top of beta blockers and ACE inhibitors if the heart’s pump function is reduced after a heart attack. MRAs are weak diuretics and help the body eliminate excess fluid. They also lower blood pressure. Possible side effects of spironolactone are elevated serum potassium and gynaecomastia (an increase in male breast size). The latter should prompt a switch to eplerenone, which does not cause this side effect.
