Determine the following:
Rhythm: _______________________________________
Rate: ___________________________________________
P waves: _______________________________________
PR interval: ____________________________________
QRS complex: __________________________________
What's your interpretation?
(Answers on next page)
Name that strip: Answers
Rhythm: Regular atrial and ventricular rhythms
Rate: Atrial, 82 beats/minute; ventricular, 41 beats/minute
P waves: Two sinus P waves to each QRS
PR interval: 0.16 second (remains consistent)
QRS complex: 0.12 to 0.14 second.
Second-degree atrioventricular (AV) block, Mobitz type II is usually associated with an anterior wall myocardial infarction and, unlike Mobitz I, is not the result of increased vagal tone or drug toxicity. Other causes include acute myocarditis and degeneration of the electrical conduction system seen in older adults.
The patient's response to Mobitz II is usually related to the ventricular rate. If the ventricular rate is within normal limits (rare), the patient may be asymptomatic. More commonly, the ventricular rate is extremely slow, cardiac output is decreased, and signs and symptoms are present (hypotension, shortness of breath, heart failure, chest pain, or syncope).
Mobitz II is less common but more serious than Mobitz I. Mobitz II has the potential to progress suddenly to third-degree AV block or ventricular standstill (asystole) with little or no warning. A 2:1 conduction ratio is common with Mobitz II (two P waves to each QRS complex).
If the ventricular rate is slow and the patient is symptomatic with severe signs and symptoms related to the slow heart rate, Advanced Cardiovascular Life Support guidelines for clinically unstable bradycardia with a pulse (atropine, transcutaneous pacing, epinephrine infusion, and dopamine infusion) should be followed.
Second-degree AV block, Mobitz type II: Identifying ECG features
Rhythm: Atrial: Regular
Ventricular: Usually regular but may be irregular if AV conduction ratios vary
Rate: Atrial: That of the underlying sinus rhythm
Ventricular: Varies depending on number of impulses conducted through AV node (will be less than the atrial rate)
P waves: Sinus; two or three P waves (sometimes more) before each QRS complex
PR interval: Consistent; may be normal or prolonged
QRS complex: Normal if block is located at the level of bundle of His; wide if block is located in bundle branches