DEAR DR. ROACH: I am a 62-year-old woman who has dealt with heart palpitations for many years. I have seen a cardiologist, and after many tests — including a heart catheterization after a false positive on my stress test — he has determined that I have a strong heart with no problems. I have told him repeatedly about the episodes I have where I can feel the irregular beats and almost completely pass out, but he insists everything is fine. After research, I asked him about a vagus nerve connection and his response is that he has heard from many patients that the episodes are frightening, but he is not concerned. Research says that taking a magnesium supplement can help palpitations. Can I begin taking magnesium to see if it will help? Can you get too much magnesium? If you have ever experienced these episodes, you would know how frightening each one is. Please help! — R.W.

ANSWER: Palpitations can indeed be a frightening experience. Many people feel afraid they are having a heart attack or something else dreadfully wrong in the heart. Some palpitations have specific, identifiable causes, but it sounds like your cardiologist has been thorough in looking for dangerous or treatable causes.

The vagus nerve has many functions, one of which is that it slows the heart. People with very slow heart rates have what we call “high vagal tone,” meaning the vagus nerve is responsible for the slow heart rate, and some people feel it as palpitations.

Most cases of palpitations are due to faster-than-normal beats, often coming from parts of the heart that do not normally act as the heart’s natural pacemaker. These are very common, but not always noticed. Many people notice them only at night when their lives are quieter and they are paying more attention to their body.

Magnesium is an effective treatment for some types of palpitations, but not all. While I generally prefer to test the blood magnesium level before treatment, a supplement of magnesium at a reasonable amount (such as 400 mg magnesium, 100% of the daily value) is reasonable and unlikely to cause problems. It is generally only possible to get too much magnesium if your kidneys do not work well, or unless you are taking very high amounts.

People with anxiety are more likely to be aware of, and be more worried about, palpitations than other people. A thorough cardio workup is still indicated, but treatment for anxiety may help with the worrisome nature of the symptoms.

DR. ROACH WRITES: A recent column on dry skin inspired many readers to write with suggestions.

Some emphasized the medical conditions associated with dry skin. Hypothyroidism, Sjogren’s syndrome, seborrheic dermatitis and ichthyosis all are entities that can lead to this symptom and require expertise to diagnose, the last two preferably from a dermatologist.

Others wrote with suggestions. Avoiding baths and showers that are too long or too hot was advice I heard repeatedly. Many people wrote with specific treatments, but the best treatment depends on the underlying condition, so getting an evaluation from a doctor is the best way of ensuring proper treatment if the initial advice (adequate water intake, regular skin moisturizers, evaluation of medications to look for a culprit) is inadequate.

I always appreciate the helpful advice from my readers.

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Dr. Roach regrets that he is unable to answer individual letters, but will incorporate them in the column whenever possible. Readers may email questions to ToYourGoodHealth@med.cornell.edu or send mail to 628 Virginia Dr., Orlando, FL 32803.