University:
West Coast University
Course:
NURS 110 | Introduction to Professional Nursing
Academic year:

2021
Views:

34

Pages:

1
Author:

Dania Lynch

2nd Degree AV Block (Mobitz Type I, Wenckebach) Rate: Atrial regular; Ventricular rate is slightly slower. Typically between 60-90 bpm Rhythm: Atrial regular. Ventricular irregular due to dropped P waves. P waves: Upright and normal. Some P’s are not followed by a QRS (more Ps than QRSs) PR Interval: Progressively longer until one P wave is not followed by a QRS complex. After the blocked beat, the cycle starts again QRS Width: VHFRQGV QT: < .40 May be longer with slower heart rates. Characteristics: Second-degree AV block- Type I is unique in that it has three different names, and all three are used interchangeably (just to keep us all on our toes!). Second degree AV Block- Type I is also called Mobitz I or it can be referred to as Wenckebach. Do not let this confuse you as all three names mean the SAME rhythm. For simplicity, we will call this rhythm “Wenckebach.” Wenckebach is characterized by a progressive prolongation of the PR interval (so the key to diagnosing this rhythm is by careful examination of each PR interval). The SA node is healthy and fires on time, thus the P to P intervals are regular. Impulses traveling through the AV node take longer and longer to fully conduct until one impulse is completely blocked. The SA node continues to fire right on time (regular P to P intervals) and the cycle of prolongation of PR intervals continues as the pattern is repeated. The repetition of this pattern results in “group beating,” (e.g. three conducted sinus beats with progressively lengthening PR intervals and a fourth sinus beat that is NOT followed by a QRS). Beats that are successfully conducted have a normal QRS width. Because QRS complexes are periodically dropped, the ventricular rhythm is irregular. This block almost always occurs at the level of the AV node (rarely at His bundle or bundle branch level), is typically a transient rhythm, and prognosis is good. Causes: Acute inferior MI, right ventricular infarction, increased vagal tone, ischemic heart disease, digitalis toxicity, beta-blockers, amiodarone, calcium channel blockers, electrolyte imbalances, rheumatic heart disease or myocarditis. Nursing Priorities: Check the patient’s blood pressure and other patient vital signs (often they are normal). Assess the patient for possible causes. Potential Treatment: Most of the time this rhythm produces no signs and symptoms and requires no treatment. If needed 2nd degree Type I AVB will respond to atropine if the patient becomes bradycardic and hypotensive. Temporary pacing should also be considered. Find and treat reversible causes, and observe for progression into higher forms of block.