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.
The bid price is the highest price a buyer is willing to pay for a share of stock, and the ask price is the minimum the seller is willing to accept. The ask price is usually higher than the bid price. The difference between the bid and ask prices is the bid-ask spread, which narrows or widens depending on the trading volume. Stock exchanges typically use automated systems to match the bid and ask prices and fill orders.