Understanding ECG Filtering

A common problem in ECG interpretation is the removal of unwanted artifact and noise. To help with this our cardiac monitors provide a means to filter the ECG recording.  Most cardiac monitors will choose the appropriate filter based on the situation. When performing routine monitoring, where only the cardiac rhythm is important, the filters applied are known as monitor mode filters. When performing a 12-Lead, which requires a high fidelity tracing, the filters applied are known as diagnostic mode filters. Beyond this, little emphasis is placed on understanding ECG filtering. This gap in education leads to problems for both experienced and inexperienced interpreters. Signal Processing Basics The frequency of a signal measures the cyclic rate or repetition, and is measured in Hertz (Hz). A frequency of 1 Hz means a signal repeats itself every one second. Our hearts produce electrical activity recorded by electrodes as a signal. The sinoatrial node fires at roughly 50 to 90 beats per minute, and for the sake of this post we will say 60 beats per minute is the happy median. This means the heart has a fundamental frequency of 1 Hz at this heart rate. Therefore, all of the ECG components (P, QRS, and T) will occur at or above this frequency. Because the ECG signal repeats itself, each time the heart cycles through systole and diastole, we can break it down into individual waves or harmonics. This process of breaking down a signal into a series of sine waves is known...
Source: EMS 12-Lead - Category: Cardiology Authors: Tags: ems-topics 12-Lead ECG Cardiac Monitoring Christopher Watford diagnostic filter EKG EMS 12-Lead filtering Source Type: research