Medical Tests & Procedures Archive


Transfusion and heart surgery: Only when needed

Unnecessary blood transfusion can do more harm than good.

Blood transfusion deserves a prominent place in the pantheon of medical advances. It has saved countless lives on the battlefield and in hospital emergency departments. It is a life-prolonging treatment for people with conditions that prevent the body from making blood or blood components, from kidney disease and cancer to disorders such as hemophilia and sickle cell anemia. But whether blood should be routinely transfused during or after heart surgery is a question that more and more people are asking. The answer is tilting toward "no."

Ask the doctor: Is high potassium a problem?

Q. You have written about low potassium in the blood and ways to improve it, but I never read about too much potassium in the blood. Can you tell me why it happens and what is done about it?

A. Relatively few people develop high levels of potassium in the blood, since the kidneys are normally quite effective in clearing this mineral from the bloodstream. A normal blood potassium measurement is 3.7 to 5.2 milliequivalents per liter.

Ask the doctor: Is it okay to have an MRI after getting a stent?

Q. I needed angioplasty in 2007 and had a stent implanted during the procedure. Due to another health problem, my doctor now wants me to have an MRI. Could this cause any problem with the stent?

A. Stents are metallic cages that hold open a coronary artery after angioplasty. Metallic objects placed in the body can pose problems for MRI scans, which use a strong magnetic field and pulses of radio waves to see inside the body. The magnetic field could dislodge the object, while radio waves could make it heat up. That kind of movement and heating has been reported for some cardiac pacemakers and implantable cardioverter-defibrillators. (MRI-safe pacemakers and implantable cardioverter-defibrillators are being developed.)

Conversation with an expert: Plavix: What you need to know

Readers often ask us about the use and safety of Plavix after angioplasty. We turned for answers to Dr. Patrick O'Gara, a member of the Heart Letter editorial board, who helped write a clinical alert about Plavix for the American Heart Association.

Almost every medical advance raises issues that demand creative problem-solving. Take artery-opening angioplasty. It uses a tiny balloon to flatten a cholesterol-filled plaque, restoring blood flow through a narrowed or blocked coronary artery without open-heart surgery. A wire-mesh stent is usually left behind to hold open the artery. However, blood clots sometimes form on a stent. This can block blood flow through the artery, causing a heart attack or sudden cardiac arrest. Taking a drug called clopidogrel (Plavix) with aspirin can fight this problem. But this combination, often called dual antiplatelet therapy, can be hard on the stomach, interacts with some drugs, and must be taken without interruption for a specified period.

On the horizon: Removing fat makes HDL ("good cholesterol") even better

High-density lipoproteins (HDL) protect the heart and arteries by removing cholesterol lodged in artery walls and riding through the bloodstream inside of low-density lipoproteins (LDL). Here's a novel way to amplify HDL's cholesterol-busting activity: Take some blood from a person. Extract the HDL. Use a process called delipidation to remove cholesterol and other fats (lipids) from the HDL. Then put the defatted HDL particles back into the bloodstream. This seems to turbocharge HDL and make it work even more aggressively against cholesterol.

In the first clinical trial of HDL delipidation in humans, the procedure was safe and effective. Treated HDL caused cholesterol-filled plaque to shrink more than did untreated HDL (Journal of the American College of Cardiology, June 15, 2010). The trial was too small and didn't last nearly long enough to see if this prevented future heart attacks or improved survival.

Ask the doctor: Do I really need surgery to fix my aortic valve?

Q. I have had a leaking aortic valve for many years. I get an echocardiogram every six months. After the latest one, my doctor told me that my heart was enlarging and asked me repeatedly whether I was getting short of breath with exercise. I told him that sure, I get tired, but it isn't like I am breathing hard while sitting still. Now he wants me to have surgery to replace the valve. Should I do this at age 68?

A. You have been getting exactly the right attention for what is called aortic regurgitation. This is the backflow of some blood into your left ventricle with each heartbeat, instead of it all going into your aorta.

Ask the doctor: What can you tell me about surgery for vertebral fractures?

Q. I have osteoporosis and a recent spine fracture. I hear there's a minor surgical procedure that can fix the fracture. Can you tell me anything about it?

A. Fractures of the bones in the spinal column (vertebrae) are common in people with osteoporosis; about 750,000 occur each year in the United States. In this type of fracture, called a compression fracture, the vertebra collapses, often causing pain, a gradual loss of height, or stooped posture. Even if the fracture doesn't cause obvious symptoms, having one fracture increases the risk of having another one. The cumulative effect of multiple fractures is chronic pain, disability, depression, and difficulty managing normal daily activities.

Radiation risk from medical imaging

Given the huge increase in the use of CT scans, concern about radiation exposure is warranted. Patients should try to keep track of their cumulative radiation exposure, and only have tests when necessary.

Clearing clogged arteries in the neck

Balloon angioplasty appears to be just as good as surgery to unblock carotid arteries.

Date of last review, March 25, 2020Opening a blocked heart artery with a balloon and then propping it open with a wire-mesh stent is more commonly used than bypass surgery for restoring blood flow to the heart. Although coronary angioplasty plus stenting isn't quite as durable as bypass surgery, it is much easier on the body, since it doesn't require opening the chest.

The situation is similar in the carotid arteries, which convey oxygen-rich blood to the brain. In that territory, carotid angioplasty plus stenting (CAS) for many people has become preferred to endarterectomy, an operation to clean out a clogged carotid artery.

Exercise stress test

The treadmill test can reveal hidden problems in the heart.

One way to judge the health of the heart and the arteries that supply it with oxygen and nutrients is to make them work harder. That's the principle behind one of the most commonly used tests in cardiology, the exercise stress test (also known as the exercise tolerance test, treadmill test, or just the stress test). It's much the same thing a mechanic does when he or she races a car's engine.

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