Antiarrhythmic Drugs

Antiarrhythmic drugs are medications that that change the electrical properties of cardiac tissue, and by doing so, change the way the heart’s electrical signal spreads across the heart. Since the tachycardias (arrhythmias that cause a rapid heart rate) are usually related to abnormalities in the electrical signal, drugs that alter the heart’s electrical signal can often improve those arrhythmias. Antiarrhythmic drugs are often effective, or at least partially effective, in treating most varieties of tachycardias.

Unfortunately, the antiarrhythmic drugs as a group tend to cause a fair amount of toxicity of one kind or another, and as a consequence, they can be difficult to take. Each antiarrhythmic drug has its own unique toxicity profile, and before prescribing any of these drugs, it is vital that your healthcare provider carefully explains the possible problems that may occur with the selected drug.

However, there is one unfortunate problem that is common to virtually all the antiarrhythmic drugs: Sometimes these drugs make the arrhythmia worse instead of better.

This feature of antiarrhythmic drugs—called “proarrhythmia”—turns out to be an inherent property of drugs that change the heart’s electrical signal. Simply put, when you do anything to change the way the electrical signal spreads across the heart, it is possible that the change will make a tachycardia better, or worse.

Commonly used antiarrhythmic drugs include amiodarone (Cordarone, Pacerone), sotalol (Betapace), propafenone (Rhythmol), and dronedarone (Multaq).

Amiodarone is the by far most effective antiarrhythmic drug and is also less likely to cause proarrhythmia than other drugs. Unfortunately, the other kinds of toxicities seen with amiodarone can be particularly nasty, and this drug should only be used (like all antiarrhythmic drugs) when absolutely necessary.

The bottom line is that healthcare providers are—and ought to be—reluctant to prescribe antiarrhythmic drugs. These drugs should be used only when an arrhythmia is producing significant symptoms or is posing a threat to cardiovascular health.

AV Nodal Blocking Drugs

The medications known as AV nodal blocking drugs—beta blockers, calcium channel blockers, and digoxin—work by slowing the heart’s electrical signal as it passes through the AV node on its way from the atria to the ventricles. This makes the AV nodal blocking drugs useful in treating SVT. Some forms of SVT (specifically, AV nodal reentrant tachycardia and the tachycardias caused by bypass tracts), require the AV node to conduct the electrical signal efficiently, and if the AV node can be made to conduct the electrical signal more slowly, the SVT simply stops.

For the SVT known as atrial fibrillation, AV nodal blocking drugs do not stop the arrhythmia, but they do slow the heart rate to help eliminate symptoms. In fact, controlling the heart rate with AV nodal blocking drugs is often the best way to manage atrial fibrillation.

ACE Inhibitors and ARBs

ACE inhibitors (angiotensin converting enzyme inhibitors) and ARBs (angiotensin II receptor blockers) work by opening blood vessels and lowering blood pressure. These medicines can:

• Reduce the work your heart has to do
• Help your heart muscle pump better
• Keep your heart failure from getting worse

Common side effects of these drugs include:

• Dry cough
• Lightheadedness
• Fatigue
• Upset stomach
• Edema
• Headache
• Diarrhea

Beta Blockers

Beta blockers slow your heart rate and decrease the strength with which your heart muscle contracts in the short term. Long term beta blockers help keep your heart failure from becoming worse. Over time, they may also help strengthen your heart.

Common beta blockers used for heart failure include carvedilol (Coreg), bisoprolol (Zebeta), and metoprolol (Toprol).

Do not abruptly stop taking these drugs. This can increase the risk of angina and even a heart attack. Other side effects include lightheadedness, depression, fatigue, and memory loss.

Water Pills or Diuretics

Diuretics help your body get rid of extra fluid. Some types of diuretics may also help in other ways. These drugs are often called “water pills.” There are many brands of diuretics. Some are taken once a day. Others are taken 2 times a day. The most common types are:

• Thiazides. Chlorothiazide (Diuril), chlorthalidone (Hygroton), indapamide (Lozol), hydrochlorothiazide (Esidrix, HydroDiuril), and metolazone (Mykrox, Zaroxolyn)
• Loop diuretics. Bumetanide (Bumex), furosemide (Lasix), and torasemide (Demadex)
• Potassium-sparing agents. Amiloride (Midamor), spironolactone (Aldactone), and triamterene (Dyrenium)

When you take these medicines, you will need regular blood tests to check how well your kidneys are working and measure your potassium levels.

Other Drugs for Heart Failure

Many people with heart disease take either aspirin or clopidogrel (Plavix). These drugs help prevent blood clots from forming in your arteries. This can lower your risk of a stroke or heart attack.

Coumadin (Warfarin) is recommended for people with heart failure who have a higher risk for blood clots. You will need to have extra blood tests to make sure your dose is correct. You may also need to make changes to your diet.

Drugs used less commonly for heart failure include:

• Digoxin to help increase the heart’s pumping strength and slow the heart rate.
• Hydralazine and nitrates to open up arteries and help the heart muscle pump better. These drugs are mainly used by people who are unable to tolerate ACE inhibitors and angiotensin receptor blockers.
• Calcium channel blockers to control blood pressure or angina (chest pain) from coronary artery disease (CAD).

Statins and other cholesterol-lowering drugs are used when needed. Antiarrhythmic medicines are sometimes used by heart failure people who have abnormal heart rhythms. One such drug is amiodarone. Another medicine, Ivabradine (Corlanor), acts to lower the heart rate and may help people with heart failure by reducing the heart’s workload.