What would be an EKG finding in a patient with a first-degree AV block?

What would be an EKG finding in a patient with a first-degree AV block?

• A. A prolonged PR interval with QRS complex
• B. A short PR interval with multiple P waves
• C. No P waves present
• D. Consistent QRS without preceding P waves

Answer: (A)

In a first-degree AV block, the key finding on the EKG is a prolonged PR interval that is consistently longer than normal (greater than 200 ms), while the QRS complex remains unchanged, indicating that all atrial impulses are conducted to the ventricles but with a delay. This slowed conduction through the AV node is the hallmark of a first-degree AV block.

The PR interval represents the time taken for the electrical impulse to travel from the atria to the ventricles, and in this case, it is noticeably prolonged but not variable. The relationship between the P waves and the QRS complexes remains regular, indicating that for every P wave, there is a corresponding QRS complex. This differentiates it distinctly from other types of blocks, as well as normal conduction.

The other choices do not describe what occurs in a first-degree AV block. A short PR interval typically suggests increased conduction velocity to the ventricles or other forms of conduction disturbances such as pre-excitation syndromes. The absence of P waves would indicate a different type of block such as a third-degree AV block, where there is complete dissociation between atrial and ventricular activity. Lastly, consistent QRS complexes without preceding P waves suggests a junctional rhythm or ventricular rhythm