Cardiac conditions that required surgery have forced into retirement two winners of the Ironman Triathlon World Championship.

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However, the Centers for Medicare and Medicaid Services (CMS), an agency of the U.S. Department of Health and Human Services, has issued a "decision memo" stating that only people having certain serious heart conditions or cardiac histories are suitable candidates for ICDs.

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The team studied 18 weight-related medical conditions, including cardiac disease, type 2 diabetes, cancer, stroke and lower back pain.

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It can be a factor in developing hypertension, cardiac disease and depression, among other conditions.

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But they can also be employed by hospitals, covering conditions such as breast cancer and cardiac problems.

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Even before the surgery begins, underlying or chronic conditions such as a history of hypertension, cardiac disease or lung disease put patients at risk for complications.

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Cardiac rehabilitation isn't appropriate for everyone, though, even if you have one of these conditions.

CNN: updated