9/22/2023 0 Comments Junctional escape rhythm diagramThis is an example of a 2:1 rhythm because there are two P waves for each QRS. Mobitz II occurs is when the P-R interval is fixed in duration, but some P waves are not followed by a QRS, as illustrated in the second tracing below. The fifth beat starts this cycle over again. In the fourth beat, the P wave is not followed by a QRS therefore, the ventricular beat is dropped. In the first tracing below, the PR interval for the first beat is 0.16 sec and increases to 0.24 sec by the third beat. In Mobitz I (also called "Wenckebach"), the PR interval gradually increases over several beats until it is sufficiently prolonged (that is, AV conduction is sufficiently impaired) that the impulse cannot pass into the ventricles (i.e., a QRS will not follow the P wave). There are two subtypes of second-degree AV blocks: Mobitz Type I and Mobitz Type II. This results in P waves that are not followed by QRS complexes. Second-degree AV nodal block - the conduction velocity is slowed to where some impulses from the atria cannot pass through the AV node. This type of block can be caused by enhanced vagal tone, digitalis, beta-blockers, calcium channel blockers, or ischemic damage to the nodal tissue. Rate is not altered by the prolonged PR interval because it is still being controlled by the SA node. In the tracing below, the PR interval is 0.24 sec. AV nodal blocks - a conduction block within the AV node (or occasionally in the bundle of His) that impairs impulse conduction from the atria to the ventricles.įirst-degree AV nodal block - the conduction velocity is slowed so that the PR interval is increased to greater than 0.20 seconds.Junctional escape rhythm - SA node suppression can cause AV node-generated rhythm of 40-60 beats/min (not preceded by P wave).Atrial fibrillation - uncoordinated atrial depolarizations.Atrial flutter - sinus rate of 250-350 beats/min.This type of rhythm includes paroxysmal atrial tachycardia (PAT). Sinus bradycardia - low sinus rate 100/min usually because of abnormal focus within the atria and paroxysmal in nature, therefore the appearance of P wave is altered in different ECG leads.Paroxysmal - an arrhythmia that suddenly begins and ends.Tachycardia - a heart rate that is higher than normal.Bradycardia - a heart rate that is lower than normal. Normal sinus rhythm - heart rhythm controlled by sinus node at a rate of 60-100 beats/min each P wave followed by QRS and each QRS preceded by a P wave.
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