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)
Contrast echocardiogramâA solution is injected into the vein and can be seen in the heart. Stress echocardiogramâThis records the heart's activity during a cardiac stress test. Echocardiogram with Doppler ultrasoundâThis helps your doctor assess blood flow. Transesophageal echocardiogramâTo provide clear images of the heart, the ultrasound device is put down your throat. Your doctor may need to use this test depending on what part of the heart needs to be viewed.