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)
During an echo test, ultrasound (high-frequency sound waves) from a hand-held wand placed on your chest provides pictures of the heart's valves and chambers and helps the sonographer evaluate the pumping action of the heart.he test is used to: 1  Assess the overall function of your heart. 2  Determine the presence of many types of heart disease, such as valve disease, myocardial disease, pericardial disease, infective endocarditis, cardiac masses and congenital heart disease. 3  Follow the progress of valve disease over time.