Diseases, Conditions, Syndromes

Q&A: Mild hypothyroidism may not need treatment

Dear Mayo Clinic: I recently was diagnosed with mild hypothyroidism that isn't causing symptoms. My doctor says I don't need treatment now, but she wants me to come back for regular checkups. Does hypothyroidism usually get ...

Medical research

New polymer heart valve implanted in first patient

Caltech researchers have helped to design a new generation of heart valves that are longer-lasting, cost less to manufacture, and are more biocompatible than options that are currently available to patients. As part of an ...

Cardiology

Alarming number of heart infections tied to opioid epidemic

An alarming number of people nationwide are developing infections of either the heart's inner lining or valves, known as infective endocarditis, in large part, due to the current opioid epidemic. This new trend predominantly ...

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Heart

The heart is a muscular organ in all vertebrates responsible for pumping blood through the blood vessels by repeated, rhythmic contractions, or a similar structure in annelids, mollusks, and arthropods. The term cardiac (as in cardiology) means "related to the heart" and comes from the Greek καρδιά, kardia, for "heart."

The heart of a vertebrate is composed of cardiac muscle, an involuntary striated muscle tissue which is found only within this organ. The average human heart, beating at 72 beats per minute, will beat approximately 2.5 billion times during a lifetime (about 66 years). It weighs on average 250 g to 300 g in females and 300 g to 350 g in males.

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