ECG 1: What is the criteria for Normal Sinus Rhythm (NSR) ?

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ECG 1: What is the criteria for Normal Sinus Rhythm (NSR) ?

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Normal sinus rhythm

asked May 22, 2013 in Medical Academics Questions by Mike Junior Resident (2,007 points)

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1 Answer

John Snow

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In normal sinus rhythm (NSR), pacemaker impulses are initiated in SA node, travel through the atrial pathways, and are delayed at the AV node. Depolarization of the atria produces a P wave. Impulse conduction proceeds unimpeded through the AV node and down the bundle branches to Purkinje fibers in the ventricles, causing ventricular depolarization and normally producing a narrow QRS complex.

Criteria:

The P wave is usually upright in leads II, III, aVF and V1. Its morphology remains constant at all times.
P-P and R-R intervals are equal and regular.
Atrial and ventricular rates are identical and range between 60 and 100 bpm.
PR interval: Normal (0.12-0.2 seconds)
QRS: Normal (0.6-0.1 seconds)

Note: A normal ECG does not exclude heart disease.