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Electrocardiography is the process of producing an electrocardiogram (ECG or EKG [a]), a recording of the heart's electrical activity through repeated cardiac cycles. [4] It is an electrogram of the heart which is a graph of voltage versus time of the electrical activity of the heart [ 5 ] using electrodes placed on the skin.
There are 6 different sinus arrhythmia. [1] [2]A normal heart should have a normal sinus rhythm, this rhythm can be identified by a ventricular rate of 60-100 bpm, at a regular rate, with a normal PR interval (0.12 to 0.20 second) and a normal QRS complex (0.12 second and less).
A digital representation of each recorded ECG channel is obtained, by means of an analog-to-digital converter and a special data acquisition software or a digital signal processing (DSP) chip. The resulting digital signal is processed by a series of specialized algorithms , which start by conditioning it, e.g., removal of noise , baselevel ...
The QT interval is a measurement made on an electrocardiogram used to assess some of the electrical properties of the heart.It is calculated as the time from the start of the Q wave to the end of the T wave, and approximates to the time taken from when the cardiac ventricles start to contract to when they finish relaxing.
High frequency QRS (HFQRS) refers to the analysis of the high frequency spectral components of the QRS complex in an electrocardiogram (ECG). High frequency analysis of the QRS complex may be useful for detection of coronary artery disease during an exercise stress test. [1] It however requires special software. [1]
ECG would be abnormal in 75 to 95% of the patients. Characteristic ECG changes would be large QRS complex associated with giant T wave inversion [4] in lateral leads I, aVL, V5, and V6, together with ST segment depression in left ventricular thickening. For right ventricular thickening, T waves are inverted from V2 to V3 leads.
The distribution of frequency and power of a waveform can be expressed as a power spectrum in which the contribution of different waveform frequencies to the waveform under analysis is measured. This can be expressed as either the dominant or peak frequency, i.e., the frequency with the greatest power or the median frequency, which divides the ...
Schematic representation of normal ECG In electrocardiography , the ST segment connects the QRS complex and the T wave and has a duration of 0.005 to 0.150 sec (5 to 150 ms). It starts at the J point (junction between the QRS complex and ST segment) and ends at the beginning of the T wave.