1 The Romans also used a 12 hour clock. 2  The 12 hour dial became popular with mechanical clocks during the 15th and 16th centuries and this has continued to this day.  The abbreviations for am and pm are often also written as a.m. and p.m. or AM and PM.
Stress Testing/Stress Echocardiogram. A stress echocardiogram is a non-invasive test that combines two tests--a treadmill stress test (TST) and an echocardiogram (ECHO). This test is used to see how the heart muscle contracts during rest and during exercise. A stress echo is made up of three parts: a resting echo study, a stress test, and a repeat echo while the heart is beating fast. (See also Drug Induced Stress Test or Nuclear Stress Test--below)
The test shows the size and shape of your heart and how well your heart chambers and valves work. Echo also can identify areas of poor blood flow to the heart, areas of heart muscle that aren't contracting normally, and heart muscle damage caused by lack of blood flow. Echo might be done before and after a stress test (see below). A stress echo can show how well blood is flowing through your heart.