Is an ECG with a ventricular rate of 74 bpm, PR interval of 172 ms (first-degree atrioventricular block), QRS duration of 102 ms, and corrected QT interval of 404 ms (male) or 448 ms (female) normal, and what management is recommended?

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ECG Interpretation: Normal Sinus Rhythm with Borderline QTc

This ECG is essentially normal and requires no specific intervention. The findings show normal sinus rhythm with all intervals within or near normal limits, though the QTc warrants attention to context.

Detailed Analysis

Heart Rate and Rhythm

  • Ventricular rate of 74 bpm is normal (60-100 bpm range)
  • Indicates normal sinus rhythm

PR Interval: 172 ms

  • This is normal (normal range: 120-200 ms) 1
  • This does NOT represent first-degree AV block, which requires PR >200 ms 2, 1, 3
  • The conduction delay is within physiologic limits and requires no monitoring or intervention

QRS Duration: 102 ms

  • Borderline normal/mildly prolonged (normal <120 ms in adults) 4
  • Does not meet criteria for bundle branch block (requires ≥120 ms)
  • May represent nonspecific intraventricular conduction delay
  • With the normal PR interval, this suggests the conduction is primarily through normal pathways 2

QT/QTc Interval: 404/448 ms

The corrected QT interpretation depends critically on patient sex:

If Male:

  • QTc 448 ms is normal (upper limit 450 ms) 5
  • No concern for QT prolongation

If Female:

  • QTc 448 ms is normal (upper limit 460 ms) 5
  • Well within acceptable range

Clinical Significance

No pathology is present on this ECG. The PR interval of 172 ms does not constitute first-degree AV block, which guidelines define as PR >200 ms 2, 1, 3. Even if this were first-degree AV block, it would be benign unless:

  • PR interval exceeds 300 ms (causing hemodynamic compromise from loss of AV synchrony) 2, 6
  • Patient has symptoms of pacemaker syndrome 7
  • PR fails to shorten appropriately with exercise 2

Management Recommendations

No specific management is needed 8:

  • No cardiac monitoring required
  • No restrictions on activity
  • No need for pacemaker evaluation
  • No need for electrophysiology study
  • No medication adjustments needed

When to Reassess

Consider further evaluation only if:

  • Patient develops symptoms (syncope, presyncope, fatigue, exercise intolerance)
  • PR interval progresses beyond 200 ms on future ECGs
  • QTc exceeds 460 ms (female) or 450 ms (male) on repeat testing
  • New medications are started that affect cardiac conduction

Common Pitfall: Do not misinterpret a PR interval <200 ms as first-degree AV block. First-degree AV block specifically requires PR >200 ms by definition 1, 3. A PR of 172 ms represents normal AV nodal conduction.

References

7
Research

First-degree AV block-an entirely benign finding or a potentially curable cause of cardiac disease?

Annals of noninvasive electrocardiology : the official journal of the International Society for Holter and Noninvasive Electrocardiology, Inc, 2013

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