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In medicine, keeping the heart beating is job number one.
But it’s not always easy, because so much can go wrong with a heart. Diseases such as viruses can invade and harm it. Mechanical parts can wear out, and the muscle can weaken with age. The heart’s built-in timer can misfire. Globs of fat can block the blood vessels. What can modern medicine do about a broken heart? Mend it—sometimes.
