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)
An echo uses sound waves to create pictures of your heartâs chambers, valves, walls and the blood vessels (aorta, arteries, veins) attached to your heart. A probe called a transducer is passed over your chest. The probe produces sound waves that bounce off your heart and âechoâ back to the probe. These waves are changed into pictures viewed on a video monitor. An echo canât harm you. Why do people need an echo test? Your doctor may use an echo test to look at your heartâs structure and check how well your heart functions. The test helps your doctor find out: