This Lead II rhythm strip is from a nine-year-old girl being monitored for an outpatient surgical procedure. She has no known heart disease. Her heart rate is 110 per minute. The PR interval is .12 seconds (120 ms), the QRS is upright and narrow at .06 seconds (60 ms), and the rhythm is regular.
Retrograde P waves
This Lead II rhythm strip shows a regular rhythm with narrow QRS complexes and retrograde P waves. The strip was taken from a nine-year-old girl. The rate is about 110 per minute and the PR interval is .12 seconds (120 ms).
A basic rhythm strip showing junctional rhythm in Lead II. The junctional pacemaker is located between the atria and the ventricles, and the resulting P wave is caused by retrograde conduction through the atria. This causes the P wave to be negatively deflected in Lead II. In junctional rhythms, the P wave can occur just before the QRS, during the QRS, or after the QRS, or may not be seen at all. If the P wave occurs before the QRS, the PR interval is usually short, reflecting the fact that the atria and the ventricles are depolarized almost simultaneously.
This rhythm strip illustrates a junctional escape rhythm. The sinus rhythm has slowed or stopped, and the junctional tissue has taken over as the pacemaker of the heart. The "junction" is loosely defined as the area between the AV node and the Bundle of His. The intrinsic rate of the pacemaking tissue in this area is 40 - 60 beats per minute. This slow rate is usually overridden by the sinus node, and the junction is not allowed to express itself as a pacemaker.
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