In terms of fingernails and toenails being gauged as an indicator of heart disease, the major trait to look for among patients is clubbing. Somewhat remarkably, this symptom was first described in the fifth century B.C. By the originator of the medical oath, Hippocrates.

Periosteal Vessels

Abnormalities in the periosteal vessels can contribute to clubbing. These vessels are part of the periosteum, a firbous membrane that funnels the circulation of blood to the bone areas of the human body. The periosteum adheres to the surface area of virtually all human bones.

When the soft tissue beneath the nail plate thickens, it results in clubbing. Although this can sometimes be a symptom of heart disease or conditions increasing the likelihood of this type of illness, clubbing can also be linked to any number of other ailments such as bowel disease, chronic bronchitis, and pulmonary malignancy. Clubbing has also been causally linked to not just congenital heart disease but also endocarditis, atrioventricular malformations, and fistulas.

Death of Young Athletes

That second to last one, atrioventricular malformations, is key. In recent years, the news has been filled with stories about the sudden deaths of high school athletes, on the basketball gymnasium hardwood, immediately following a football practice, and so on.

In many of these cases, the cause of death has turned out to be an undetected atrioventricular formation, or put more simply, a wrongly formed heart valve. Thus, clubbing of the toe or fingernails at this age is something that should be paid very serious attention.

One quick form of clubbing self-diagnosis is known as the "Shamroth sign." When a person lines up their thumbs for example front to front, there is a diamond-shaped space separateing them at the base. With clubbing, that space is obliterated and the entire length of the fingernails touch, from the base to the top. People noticing this symptom should consult a doctor.