NREMT Paramedic Cognitive ExamCardiology & ResuscitationEasy
A 70-year-old female presents with sudden onset of dizziness, weakness, and syncope. Her ECG shows a heart rate of 40 bpm, regular rhythm, with P waves present before each QRS complex, but the PR interval is constant and prolonged (0.32 seconds). Her blood pressure is 80/50 mmHg. What type of heart block does this patient exhibit?
- ASecond-degree AV block Type I (Wenckebach)
- BFirst-degree AV block
- CSecond-degree AV block Type II
- DThird-degree AV block
Show answer & explanationAnswer & explanation
Correct answer: B. First-degree AV block
The ECG description of a regular rhythm with a heart rate of 40 bpm, P waves present before each QRS complex, and a constant, prolonged PR interval (greater than 0.20 seconds) is characteristic of a first-degree AV block. The patient's symptomatic bradycardia is likely related to the slow rate, not directly the first-degree block itself, which is often asymptomatic.
Why the other options are wrong
- A. Second-degree Type I (Wenckebach) involves progressive lengthening of the PR interval until a QRS complex is dropped.
- C. Second-degree Type II involves a constant PR interval with occasional dropped QRS complexes.
- D. Third-degree AV block (complete heart block) shows no correlation between P waves and QRS complexes.
First-Degree AV Block
First-degree AV block is an ECG finding where the conduction from atria to ventricles is delayed, resulting in a prolonged PR interval.
- PR interval > 0.20 seconds.
- Every P wave is followed by a QRS complex.
- Usually asymptomatic, but can be associated with other conduction abnormalities.
Memory trick: PR too long? First degree. Long, longer, drop? Wenckebach. Constant, drop? Mobitz II. P's and Q's don't agree? Third degree.