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Electrocardiogram (ECG) is a graph created by an electrocardiograph, which records the heart's electrical activity within a certain time. Its name consists of a number of different parts: electro, because it relates to electronics, cardio, Greek word for heart, gram, a Greek root meaning "to write". Analysis of a number of waves and normal vectors of depolarization and repolarization produce important diagnostic information.
It is the gold standard for diagnosis of cardiac arrhythmias Guiding therapy and risk levels for patients with suspected acute cardiac infarction bibs Helping find electrolyte disturbances (eg hyperkalemia or hypokalemia) Enables discovery of conduction abnormalities (eg right bundle branch block and left) Used as a filter tool ischemic heart disease during cardiac stress test Sometimes it's not useful for detecting heart disease (eg pulmonary embolism or hypothermia)
Electrocardiogram does not directly assess cardiac contractility. However, the ECG may provide a thorough indication of the ups and downs of a contractility.
Paper ECG recorder
A typical electrocardiograph runs at a paper speed of 25 mm / s, although speeds above are occasionally used. Each small block of ECG paper is 1 mm ². With a speed of 25 mm / s, 1 small box of ECG paper translates into 0.04 s (40 ms). 5 small boxes up a large box, which is equal to 0.20 s (200 ms). Therefore, there are 5 large blocks per second. A diagnostic quality 12 lead ECG is calibrated at 10 mm / mV, so 1 mm translates into 0.1 mV. Signal "calibration" should be included in every record. Standard signal of 1 mV must move the stylus vertically 1 cm, ie, 2 large squares on ECG paper.
Filter Selection
Modern ECG monitors offer multiple filters for signal processing. The most common settings are monitor mode and diagnostic mode. In monitor mode, the low frequency filter (also called high-pass filter because signals above the threshold to pass) set at either 0.5 Hz or 1 Hz and high frequency filter (also called low-pass filter because signals below the threshold are allowed to pass ) is set at 40 Hz. This limits artifact for routine cardiac rhythm monitoring. High-pass filter helps reduce wandering baseline and low pass filter helps reduce power line noise 50 or 60 Hz (power line network frequency differs between 50 and 60 Hz in some countries). In diagnostic mode, the high pass filter set at 0.05 Hz, which allows accurate ST segments recorded. Low pass filter set at 40, 100, or 150 Hz. As a result, the monitor mode ECG display is more filtered than diagnostic mode, because its bandpass is narrower.
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