A Holter monitor is a battery-operated portable device that measures and tape records your heart's activity (ECG) continuously for 24 to 48 hours or longer depending on the type of monitoring used. The device is the size of a small camera.  Most modern machines record to a memory card rather than old fashioned cassette tapes but this test is still commonly referred to as a 24 hour tape.

​

It is useful to profile a patients heart rate or detect arrhythmias that occur daily.