Cardiac tamponade can occur due to: 1  Dissecting aortic aneurysm (thoracic) 2  End-stage lung cancer. 3  Heart attack (acute MI) 4  Heart surgery. 5  Pericarditis caused by bacterial or viral infections. 6  Wounds to the heart.
Bid vs. ask and why yields matter. With many investments, the concept of bid and ask applies to prices. The bid price is what a buyer is willing to pay for a security, while the ask price is what a seller is willing to accept for the same security. The difference between those two numbers is known as the bid-ask spread, and in general, the narrower that spread, the more liquid the market is.
If you're investing in individual securities, particularly less-liquid ones, it pays to be aware of bid-ask spreads when you're buying and selling. The bid is the price that someone is willing to pay for a security at a specific point in time, whereas the ask is the price at which someone is willing to sell. The difference between the two prices is called the bid-ask spread. Bid-ask spreads have the characteristic of heads they win, tales you lose: If you're a seller, you receive the lower price (the bid), and if you're a buyer, you pay the higher price (the ask).