Medical terms can be difficult to understand. Here is a list of the words we have used in this website, along with their definitions.

ACE (angiotensin-converting enzyme) inhibitor: A medicine that lowers blood pressure by relaxing arteries and helping the body get rid of salt and water.

AHA (American Heart Association): The AHA is the oldest and largest organization founded to fight heart disease and stroke.

A-HeFT (African American Heart Failure Trial): A study that enrolled African Americans only and showed that BiDil helped this population live longer, stay out of the hospital longer, and have an improved quality of life.

Aldosterone antagonist: A medicine that helps control the balance of salt and water in your body. Aldosterone antagonists are also called “potassium-sparing water pills,” as they help remove extra water from your body while helping to keep potassium levels in the normal range. Potassium is important because it helps trigger your heart to squeeze blood through your body.

ARB (angiotensin receptor blocker): A medicine that blocks a chemical that narrows blood vessels. By widening the blood vessels, ARBs help blood flow more easily through the body.

Arrhythmia: When the electrical impulses that tell your heart when to beat don’t work properly, this can cause your heart to beat too fast, too slow, or irregularly. This is known as heart arrhythmia. This may feel like a flutter inside your chest, or as if your heart is racing after a quick run. Some arrhythmias are harmless, but can be dangerous for someone with a weak or damaged heart.

Beta blocker: A medicine that helps lower your heart rate, reducing your body’s demand for oxygen and helping to improve heart failure symptoms. Beta blockers are also commonly used to lower high blood pressure.

Cardiac glycoside: Also called digoxin, made from the foxglove plant. A medicine that helps slow and strengthen the heartbeat by affecting the natural electrical system in the heart and the heart muscle.

Cholesterol: A wax-like substance made by your body and also found in fatty foods. Cholesterol does not dissolve in the blood, and must be carried through the bloodstream as particles. If the particles get stuck in an artery, they can build up and block the flow of blood through it, causing a heart attack or stroke. “Bad” cholesterol helps to build up these particles, called plaque. “Good” cholesterol helps remove the “bad” cholesterol from the arteries to the liver, where it is broken down and removed from the body.

Class 1A recommendation: The highest form of recommendation from a medical organization. “Level 1” means that a procedure or treatment should always be used for a certain condition. “Level A” means that the recommendation is based on many studies in many different people.

Congenital heart disease: Heart disease that you are born with. It happens when the fetus is growing in the uterus, resulting in the heart not forming correctly. It can be caused by conditions such as Down Syndrome, maternal abuse of drugs or alcohol during pregnancy, or when a woman is infected by a virus, such as German measles, in the first 3 months of pregnancy.

Congestive heart failure (CHF): Also called heart failure. CHF happens when a weak or stiff heart cannot pump blood through the body efficiently. It can be caused by blocked or narrowed arteries, heart attack, other damage to the heart muscle from drugs or alcohol abuse, or conditions that overwork the heart, such as high blood pressure, diabetes, or kidney disease.

Coronary artery disease (CAD): A condition in which the blood flow is reduced through the coronary arteries to the heart muscle. CAD is caused by buildup of cholesterol and fats in the arteries, which narrows them. This condition can cause chest pain or heart damage, and is also called coronary heart disease (CHD).

Coronary heart disease (CHD): A condition in which the blood flow is reduced through the coronary arteries to the heart muscle. CHD is caused by buildup of cholesterol and fats in the arteries, which narrows them. This condition can cause chest pain or heart damage, and is also called coronary artery disease (CAD).

Decompensated HF event: When symptoms of heart failure get worse quickly. Can be caused by a medical illness or infection. Can cause dangerous breathing problems and shortness of breath, as well as fluid buildup and extreme tiredness. Needs to be treated by a medical professional right away.

Diabetes: A condition that results when your body cannot produce or use insulin in the correct way. Also called “high blood sugar.” People who have diabetes will often need to urinate, and are always thirsty and hungry. Most cases of diabetes are “type 2,” meaning that the body does not produce enough insulin. Having diabetes increases the risk for developing heart disease.

Diastolic failure: A condition or process that causes the lower left chamber of the heart to stiffen or thicken, making it more difficult for the heart to fill with enough blood during the diastolic (filling) phase. This means that there is less blood for the heart to pump to the rest of your body during the systolic (pumping) phase.

Digoxin: A cardiac glycoside made from the foxglove plant. It helps the heart beat slower and stronger. Digoxin is used most often to treat irregular heartbeat.

Diuretic: Also called a “water pill.” Helps your body get rid of extra fluid by increasing urine output. This helps remove fluid buildup that can interfere with your heart pumping efficiently.

Echocardiogram: A picture of the heart made by using sound waves. This lets your doctor see how your heart is beating and pumping blood. It is similar to an ultrasound that doctors use to look at a fetus inside a woman.

Electrocardiogram: A recording of the electrical activity of the heart. Also called an ECG or EKG. The results appear on a long scroll of paper, and look like peaks and valleys.

High blood pressure: Also called “hypertension.” Refers to the force of blood pushing on artery walls as it flows through the body. Consistently high pressure can damage arteries and cause heart disease or stroke if left untreated.

Hydralazine hydrochloride: A medicine that helps your blood vessels relax, making it easier for blood to flow through your body. It is one of the ingredients in BiDil.

Hypertension: Also called “high blood pressure.” Refers to the force of blood pushing on artery walls as it flows through the body. Consistently high blood pressure can damage arteries and cause heart disease or stroke if left untreated.

Isosorbide dinitrate: Also called “nitroglycerin.” It is a medicine that helps prevent chest pain in people with certain heart conditions. It helps to relax and widen blood vessels, allowing the blood to flow through more freely. It is one of the ingredients in BiDil.

Left-sided heart failure: Occurs when the left side of your heart is too weak to pump the oxygen-rich blood that comes from the lungs to the rest of your body. This can present as systolic heart failure (meaning that the heart cannot contract with enough strength to push blood out) or diastolic heart failure (meaning that the heart muscle is too stiff to fill with enough blood).

Nitric oxide: A chemical your body produces naturally that regulates blood flow in your veins and arteries by helping them to widen and relax. Also called “nitroglycerin.”

Nitroglycerin: A medicine that helps relax and widen blood vessels to help blood flow more easily through the body. Commonly used as a quick-dissolving tablet placed under the tongue to relieve chest tightness and pain.

Right-sided heart failure: Occurs when the heart is too weak to move “used” blood from the veins back to the lungs so it can get more oxygen. Usually occurs as a result of left-sided heart failure. When the right side of the heart loses pumping power, blood backs up into the veins and causes swelling or fluid buildup in the legs, ankles, and stomach area.

Download tips on living with HF An HF diagnosis can be overwhelming. Learn to live better with HF here.

Information for Patients about BiDil® (isosorbide dinitrate/hydralazine HCl)

BiDil is approved for use with other heart medicines to treat heart failure in black patients to improve survival, improve heart failure symptoms, and help patients stay out of the hospital longer. There is little experience in patients with heart failure who experience significant symptoms while at rest. Most patients in the clinical study of BiDil also received other heart failure medicines.


Tell your doctor about any allergies you have, especially if you're sensitive to nitrates, such as nitroglycerin tablets or isosorbide dinitrate (Isordil®). BiDil has a nitrate component, so you need to let your doctor know.

Tell your doctor if you're taking any erectile dysfunction or pulmonary hypertension drugs like Viagra® or Revatio(sildenafil), Levitra® (vardenafil) or Cialis® (tadalafil).


Also tell your doctor if you are taking any medication to decrease blood pressure because when taken with BiDil, blood pressure may become too low.

It is possible you'll get headaches, especially at first, but they often lessen over time. Keep your doctor posted on your headache progress; he or she may want to adjust your dosage.

If you experience dizziness, call your doctor. Please make sure to tell your doctor about any of the signs or symptoms mentioned below or about any unusual events that worry you.

Drinking less fluids than your doctor recommends or losing fluid due to diarrhea, sweating, or vomiting may cause low blood pressure, lightheadedness, or fainting. If fainting occurs, stop taking BiDil and contact your doctor immediately.

Lightheadedness may occur when standing, especially after sitting or lying down.

If you experience any achy and/or swollen joints, unexplained fever for more than a few days, skin rashes, chest pain, prolonged weakness or fatigue (even after a good night's sleep), or any other unexplained signs or symptoms, make sure to tell your doctor as they may be signs of a serious medical condition.

You may also experience rapid heartbeat that could lead to chest pain or aggravate chest pain, or numbness or tingling in the hands or feet.


Headache and dizziness were the most frequent side effects experienced in studies with BiDil.

You are encouraged to report negative side effects of prescription drugs to the FDA. Visit or call 1-800-FDA-1088.

Please click here to see full Prescribing Information for BiDil. This information does not take the place of talking with your healthcare provider about your condition or your treatment. Ask your doctor if BiDil may be right for you.