The Question is from neet-zoology body-fluids-and-circulation ecg, and it was created by the author A SUBRAMANYAM

Question

A patient presents with an ECG showing a PR interval of 0.24 seconds, a QRS complex duration of 0.08 seconds, and a heart rate of 70 bpm.  No delta waves are present. Which of the following is the MOST likely diagnosis?

A SUBRAMANYAM · Accepted Answer

## CORE INFORMATION
✓ **Answer**: A
## CONCEPT FRAMEWORK
 **Primary Concept**: ECG interpretation and heart block classification.
 **Related Topics**: Cardiac conduction system, PR interval, QRS complex duration, delta waves.
 **Prerequisites**: Understanding of normal ECG parameters and the different types of AV blocks.
## SOLUTION PATHWAY
**Given Information**:
  PR interval = 0.24 seconds
  QRS complex duration = 0.08 seconds
  Heart rate = 70 bpm
  No delta waves present
**Method & Steps**:
 1. Analyze the PR interval.
  Reasoning: The normal PR interval is 0.12-0.20 seconds. A PR interval > 0.20 seconds indicates a delay in AV nodal conduction.
  Formula/Rule: None directly applicable, but knowledge of normal PR interval range is crucial.
 2. Analyze the QRS complex duration.
  Working: The QRS complex duration of 0.08 seconds is within the normal range (0.06-0.10 seconds), indicating normal ventricular depolarization.
  Key Point: A prolonged QRS complex (>0.10 seconds) often suggests a bundle branch block or other ventricular conduction abnormality.
 3. Consider the absence of delta waves and the heart rate.
  Result: The prolonged PR interval, normal QRS duration, absence of delta waves, and normal heart rate are consistent with a first-degree AV block.  Second-degree AV block (Mobitz Type I) would show progressively lengthening PR intervals before a dropped beat. Third-degree AV block would show complete dissociation between atrial and ventricular activity. Wolff-Parkinson-White syndrome is characterized by the presence of delta waves.
  Verification: The findings align perfectly with the diagnostic criteria for first-degree AV block.
 ## OPTION ANALYSIS
A ✓: First-degree AV block: Correct. This diagnosis aligns with the prolonged PR interval and normal QRS complex and heart rate.
B :x: Second-degree AV block (Mobitz Type I): Incorrect. Mobitz Type I is characterized by progressively lengthening PR intervals until a QRS complex is dropped. This ECG shows a constant, prolonged PR interval.
C :x: Third-degree AV block: Incorrect. Third-degree AV block shows complete dissociation between atrial and ventricular rhythms, which is not present here.
D :x: Wolff-Parkinson-White syndrome: Incorrect. This syndrome is characterized by the presence of delta waves, which are explicitly absent in this case.
 ## LEARNING AIDS
 **Common Mistakes**:
  1.Confusing first-degree AV block with other types of AV blocks: Pay close attention to the PR interval pattern and the presence or absence of dropped beats.
  2.Overlooking the significance of the QRS complex duration: A prolonged QRS complex can indicate other conditions that need to be considered.
 **Quick Tips**:
  1.Remember the normal ranges for PR interval and QRS duration.
  2.Systematically analyze ECG parameters: PR interval, QRS duration, heart rate, and presence of any abnormalities like delta waves.

A SUBRAMANYAM · Answer

The correct Option is "First-degree AV block"

A SUBRAMANYAM · Answer

Second-degree AV block (Mobitz Type I)

A SUBRAMANYAM · Answer

Third-degree AV block

A SUBRAMANYAM · Answer

Wolff-Parkinson-White syndrome

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