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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.
To measure the QRS interval start at the end of the PR interval ... Shorter in children [4] ... where upper range of normal is 35 ms.
This interval reflects the time the electrical impulse takes to travel from the sinus node through the AV node. A PR interval shorter than 120 ms suggests that the electrical impulse is bypassing the AV node, as in Wolff-Parkinson-White syndrome. A PR interval consistently longer than 200 ms diagnoses first degree atrioventricular block.
The normal PR interval is from 120 ms to 200 ms in length. This is measured from the initial deflection of the P wave to the beginning of the QRS complex. [3] In first-degree heart block, the AV node conducts the electrical activity more slowly. This is seen as a PR interval greater than 200 ms in length on the surface ECG.
Sinus bradycardia is commonly seen in normal healthy persons and athletes in the absence of pathophysiological diseases or conditions. [1] Different factors or etiologies could lead to the dysfunction of the sinus node, causing a malformation or prolongation of the impulse. In terms of pathophysiological diseases, sinus rhythm may be caused by:
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).
If lead I is positive (translating to 0° on the hexaxial reference system) and lead II is positive (translating to 60°), the electrical heart axis is estimated to fall in the left lower quadrant within the normal range. On the other hand, as shown in Figure 2, if lead I is negative (translating to 180°) and lead II is positive, the ...
Lown–Ganong–Levine syndrome (LGL) is a pre-excitation syndrome of the heart. Those with LGL syndrome have episodes of abnormal heart racing with a short PR interval and normal QRS complexes seen on their electrocardiogram when in a normal sinus rhythm.