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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.
Schematic representation of a normal sinus rhythm EKG wave. In electrocardiography, the PR interval is the period, measured in milliseconds, that extends from the beginning of the P wave (the onset of atrial depolarization) until the beginning of the QRS complex (the onset of ventricular depolarization); it is normally between 120 and 200 ms in duration.
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.
Heart rate variability visualized with R-R interval changes Electrocardiogram (ECG) recording of a canine heart that illustrates beat-to-beat variability in R–R interval (top) and heart rate (bottom). Heart rate variability (HRV) is the physiological phenomenon of variation in the time interval between heartbeats. It is measured by the ...
The ILR records by "freezing" the electrical information preceding, during and after the symptoms in the format of an electrocardiogram. [1] The technician or physician can download and review the recorded events during an office visit using a special programmer [4] or via online data transmission. [5]
Upper limit of normal QT interval, corrected for heart rate according to Bazett's formula, [5] Fridericia's formula, [10] and subtracting 0.02 s from QT for every 10 bpm increase in heart rate. [13] Up to 0.42 s (≤ 420 ms) is chosen as normal QTc of QT B and QT F in this diagram.
Normal heart rate (classically 60 to 100 beats per minute for an adult). Regular rhythm, with less than 0.16-second variation in the shortest and longest durations between successive P waves The sinus node should pace the heart – therefore, P waves must be round, all the same shape, and present before every QRS complex in a ratio of 1:1.
The typical meaning of an "ECG" is the 12-lead ECG that uses 10 wires or electrodes to record the signal across the chest. Interpretation of an ECG is the basis of a number of cardiac diseases including myocardial infarction (heart attack) and arrhythmias such as atrial fibrillation .