Selenium deficiency occurs when an organism lacks the required levels of selenium, a critical nutrient in many species. Deficiency, although relatively rare in healthy well-nourished individuals, can have significant negative results, affecting the health of the heart and the nervous system; contributing to depression, anxiety, and dementia; and interfering with reproduction and gestation. Signs and symptoms
Selenium deficiency in combination with Coxsackievirus infection can lead to Keshan disease, which is potentially fatal. Selenium deficiency also contributes (along with iodine deficiency) to Kashin-Beck disease. The primary symptom of Keshan disease is myocardial necrosis, leading to weakening of the heart. Kashin-Beck disease results in atrophy, degeneration and necrosis of cartilage tissue. Keshan disease also makes the body more susceptible to illness caused by other nutritional, biochemical, or infectious diseases. Selenium is also necessary for the conversion of the thyroid hormone thyroxine (T4) into its more active counterpart triiodothyronine (T3), and as such a deficiency can cause symptoms of hypothyroidism, including extreme fatigue, mental slowing, goiter, cretinism, and recurrent miscarriage. Causes
It can occur in patients with severely compromised intestinal function, those undergoing total parenteral nutrition, those who have had gastrointestinal bypass surgery, and also in persons of advanced age (i.e., over 90).People dependent on food grown from selenium-deficient soil may be at risk for deficiency.
The PR depression is often seen early in the process as the thin atria are affected more easily than the ventricles by the inflammatory process of the pericardium.Since the mid-19th century, retrospective diagnosis of pericarditis has been made upon the finding of adhesions of the pericardium.When pericarditis is diagnosed clinically, the underlying cause is often never known; it may be discovered in only 16–22 percent of people with acute pericarditis. Imaging
On MRI T2-weighted spin-echo images, inflamed pericardium will show high signal intensity. Late gadolinium contrast will show uptake of contrast by the inflamed pericardium. Normal pericardium will not show any contrast enhancement. Classification
Pericarditis can be classified according to the composition of the fluid that accumulates around the heart.Types of pericarditis include the following:
serous
purulent
fibrinous
caseous
hemorrhagic

Acute vs. chronic
Depending on the time of presentation and duration, pericarditis is divided into "acute" and "chronic" forms. Acute pericarditis is more common than chronic pericarditis, and can occur as a complication of infections, immunologic conditions, or even as a result of a heart attack (myocardial infarction), as Dresslers syndrome. Chronic pericarditis however is less common, a form of which is constrictive pericarditis. The following is the clinical classification of acute vs. chronic:
Clinically: Acute (<6 weeks), Subacute (6 weeks to 6 months) and Chronic (>6 months)

Treatment
The treatment in viral or idiopathic pericarditis is with aspirin, or non-steroidal anti-inflammatory drugs (NSAIDs such as ibuprofen).