DEAR DR. ROACH: What causes heart explosion? I heard that it can relate to a heart attack. I knew of two people who had it. How often does it happen? — L.B.

ANSWER: The heart doesn’t actually explode, so I suspect you are talking about rupture of the wall of the left ventricle, which fortunately is a rare complication of a large heart attack. Back when I was in medical school, one of my professors noted that people seldom survive it. The mortality rate at that time was about 95%. The most recent study showed 75% of people with a wall rupture will die. Immediate surgery is the only hope, and even that has a high risk.

A heart attack is death of heart muscle cells, and after a heart attack, there is a period where the body absorbs the dead muscle cells and makes a scar. But before the scar is fully formed (almost always within two weeks of the heart attack), the dead muscle is weak and can potentially rupture under the ceaseless work and constant pressure of the heart. In the era where most heart attacks are treated by getting blood flow back to the damaged area, the incidence of wall rupture is very small, about 0.01%.

DEAR DR. ROACH: My father is 67 and has had keratoconus for approximately 40 years. He wears special contact lenses and is fully functional with them, but his eye doctor has recommended a corneal transplant. First they want to do his left eye because of the scarring and limited vision. Later, they will perform a transplant on the right, which is also scarred but very thin and conical. The doctor recommended the left eye first so that he would have some vision during the process. How successful are corneal transplants in someone his age? What is the risk of total vision loss in one or both eyes? — C.J.B.

ANSWER: Keratoconus is a thinning of the cornea with a protruding cone shape, exactly as you described. Since the cornea is responsible for much of the eye’s ability to focus, progressive visual impairment is universal. The change can be slow or sudden. The condition is not rare, perhaps two people per thousand will develop it, and there is a slight family association. Most people can get good vision correction with glasses, but contact lenses usually become necessary. Regular contact lenses are used at first, but scleral lenses, which are larger diameter so they rest on the sclerae (whites of the eye), are more comfortable and have less risk of scar formation or worsening of the keratoconus. These can be customized to provide better results.

When contact lenses are not helpful — or are uncomfortable due to scarring, which happens 10% to 15% of the time — a full-thickness corneal transplant, also called a penetrating keratoplasty, is recommended. The success rate is reported to be greater than 90%. Rejection of the graft is a serious complication, usually treated by steroid drops. Astigmatism — a cause of blurry vision — is another complication, usually treated by contact lenses or additional surgical procedures.

Another treatment that is sometimes used is called collagen cross-linking, which uses the vitamin riboflavin along with ultraviolet light to strengthen the corneal tissue. This is often used in people with progressive keratoconus, but cannot be used if the cornea is too thin, as might be the case in your father.

Permanent vision loss after surgery is uncommon.

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.

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