Dear Dr. Roach: I recently was diagnosed with A-fib and am taking metoprolol. My cardiologist also wants me on Xarelto, which is a blood thinner. Why is it necessary to take the blood thinner to avoid blood clots when the metoprolol should be averting the A-fib anyway, which would cause the blood pooling and possible clotting.
Dear F.L.: Atrial fibrillation (“A-fib”) is a chaotic lack of rhythm in the atria of the heart. This prevents the coordinated mechanical motion of the atria — the smaller chambers of the top of the heart — so they no longer fill the ventricles, the larger chambers that send the blood to the lungs (from the right side of the heart) and the body (from the left side). The rate of the ventricles normally is dependent upon the pacemaker in the right atrium: In atrial fibrillation, the ventricular heart rate can be normal, too slow or too fast.
The heart rate of most people with A-fib is too fast, at least some of the time. Metoprolol, a beta blocker, slows the heart rate down to prevent dangerously high heart rates. It is pretty effective at doing so, although people who exercise may find that their heart rates can get very high, and may need a different medication. People with A-fib and very slow heart rates may need an artificial pacemaker.
Metoprolol does not restore a normal rhythm in A-fib. There are medications, such as flecainide or amiodarone, which can convert A-fib into normal rhythm, though they are not always effective. The heart also can be electrically shocked to try to restore normal rhythm.
The decision of treating the heart rate in A-fib versus treating the rhythm depends on the individual’s symptoms and is made by a cardiologist. However, every person with A-fib needs careful consideration of treatment to prevent a blood clot, since the risk for stroke can be high. Older age, female sex and other vascular issues — such as high blood pressure, diabetes, peripheral vascular disease, heart failure and especially a previous history of blood clot or stroke — are risk factors for developing a stroke with A-fib. The anticoagulant (often inaccurately called “blood thinner”) Xarelto, like a much older drug, warfarin (Coumadin), reduce this risk.
Most people with A-fib need treatment to prevent blood clot and stroke, AND treatment of either the rate or the rhythm. If rhythm control is successful, anticoagulation may be stopped later.
Dear Dr. Roach: My doctor wants me to get more vitamin D. Can I use cod liver oil? I did as a kid.
Dear V.M.: There are many good food sources of vitamin D, and cod liver oil is near the best. A single tablespoon contains about 1,400 units of vitamin D, which is as much as almost anyone needs in a day. Swordfish and salmon are excellent sources of vitamin D as well, with about 500 units in a 3-ounce serving.
Dear Dr. Roach: My wife has wet AMD. Her ophthalmologist gave her some vitamins (to take three times a day). They include 25 mg of zinc oxide. She has read somewhere that women should not take more than 8 mg of zinc a day. These vitamins would total 75 mg daily. Are zinc and zinc oxide the same? Can she take these vitamins?
Dear J.N.: The usual dose of zinc for age-related macular degeneration is 80 mg daily of zinc oxide. Twenty-three percent of zinc oxide is elemental zinc, so this is about 18 mg of elemental zinc. The ophthalmologist is giving a very standard and safe dose for AMD.
The U.S. recommended daily allowance for zinc is 11 mg for men, 8 mg for women. Very high doses of zinc can be dangerous, but this dose is still in the safe zone.
Email questions to ToYourGoodHealth@med.cornell.edu.