To interpret a telemetry strip, establish the basic shape of each heartbeat, and measure the spacing between them. In this initial assessment, look for irregularities in heartbeat shape and spacing. Irregularities may be harmless or could be signs of cardiac distress, according to Practical Clinical Skills.
A regular heartbeat recorded on a telemetry, or EKG, strip has the same basic shape. It starts with a small upward wave, called P. Next, in a shape called the QRS complex, there is a small downward deflection, Q, followed by a large upward deflection, R, and a small downward wave, S. The heartbeat ends with a medium upward wave, labeled T, and a slight upward wave that may not be visible, labeled U. These shapes represent heart movements as they occur in time, explains Practical Clinical Skills.
An EKG strip represents time through a grid pattern. Along a horizontal axis, black marks indicate time intervals of three seconds. Those intervals are 15 squares in length, with each square representing .2 seconds. Each square is further divided into a grid of 25 smaller squares that each represent .04 seconds. Heart rate and rhythm are indicated by the number of squares between each peak or valley in the basic heartbeat shape, reports Practical Clinical Skills.
An EKG strip also indicates voltage along the vertical axis. Each large square that indicates .2 seconds also indicates .5 millivolt. The small squares represent .1 millivolt. The height of each heartbeat shape indicates how strong the heart's electrical current is for that movement, according to Practical Clinical Skills.