Second Degree Heart Block Type I - Heart Blocks.

Description

• Also known as Wenckebach Phenomenon; this dysrhythmia is typically stable and often temporary with the patient remaining asymptomatic as long as the ventricular response remains within the “normal” range.
• The unique feature (hallmark) of this dysrhythmia is the presence of a prolonging P-R interval from one cardiac complex to the next, until it reaches a point where the QRS complex is non-conducted ( blocked or more simply missing). Then the pattern starts over again.

Example

• In this dysrhythmia, if the third QRS complex is dropped/blocked, then it will always be the third complex that is blocked before re-setting in a repetitious pattern.
• It is important to note the following:
  • The P – P intervals are regular and the R to R intervals are irregular.
  • here are more P waves than QRS complexes. Report the rate of each separately.

Practice Strip

Analyze this tracing using the five steps of rhythm analysis.

Show Answer

• Rhythm: Atria – Regular, Ventricles - Irregular
• Rate: Atria – 56, Ventricles - 40
• P Wave: Upright
• PR interval: Variable, progressive
• QRS: 0.10 sec
• Interpretation: Second Degree Heart Block Type I