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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.
Wiggers diagram with mechanical (echo), electrical (ECG), and aortic pressure (catheter) waveforms, together with an in-ear dynamic pressure waveform measured using a novel infrasonic hemodynography technology, for a patient with severe aortic stenosis.
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).
Still, the real predictive value of these findings is questioned. Late potentials may be found in 0-10% of normal volunteers. When used as a prognostic factor for the development of ventricular tachycardia , they have a sensitivity of 72% and a specificity of 75%, yielding a positive predictive value of 20% and a negative predictive value of 20%.
The hexaxial reference system is a diagram that is used to determine the heart's electrical axis in the frontal plane. The hexaxial reference system, better known as the Cabrera system, is a convention to present the extremity leads of the 12 lead electrocardiogram, [1] that provides an illustrative logical sequence that helps interpretation of the ECG, especially to determine the heart's ...
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.
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.
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.