What is the interpretation of an EKG showing a prolonged PR interval, prolonged QT and QTc intervals, and abnormal axis deviations?

EKG Interpretation

This EKG shows first-degree atrioventricular (AV) block with an abnormal cardiac axis, requiring clinical correlation but not immediate intervention in an asymptomatic patient.

Analysis of Key EKG Parameters

• Heart Rate: 75 bpm (normal range 60-100 bpm)
• PR Interval: 158 ms (borderline normal, upper limit is 200 ms) 1
• QT/QTc Interval: 382/408 ms (within normal limits)
• QRS Duration: 97 ms (normal, <120 ms)
• Axis Deviations:
  • P-wave axis: -150° (abnormal)
  • QRS-wave axis: -162° (extreme left axis deviation)
  • T-wave axis: 156° (abnormal)

Interpretation of Findings

First-Degree AV Block

While the PR interval is technically within normal limits at 158 ms (normal <200 ms), it's at the higher end of normal. First-degree AV block is characterized by a PR interval >200 ms 1. The PR interval represents the time required for the electrical impulse to travel from the sinus node through the AV node to the ventricles. Prolongation indicates delayed conduction at the level of the AV node or His-Purkinje system.

Axis Deviation

The extreme left axis deviation (QRS axis -162°) is significant and abnormal. Normal QRS axis is between -30° and +90° 1. This extreme deviation suggests:

• Possible left anterior fascicular block
• Potential conduction system disease
• Possible underlying structural heart disease

Normal QRS Duration and QT Interval

• The QRS duration of 97 ms indicates normal ventricular depolarization
• The QTc of 408 ms is within normal limits (normal <470 ms for males, <480 ms for females) 1

Clinical Significance

Prognostic Implications

First-degree AV block in isolation generally has a benign prognosis 1. However, the combination with extreme axis deviation warrants further evaluation as it may indicate more extensive conduction system disease.

Potential Causes to Consider

1. Age-related conduction system degeneration
2. Medications: Beta-blockers, calcium channel blockers, digoxin, antiarrhythmics
3. Electrolyte abnormalities: Hyperkalemia can affect AV conduction 1
4. Structural heart disease: Cardiomyopathy, valvular disease
5. Infiltrative diseases: Amyloidosis, sarcoidosis
6. Congenital heart disease: More common with abnormal axis 1
7. Myocarditis or endocarditis: Can cause non-specific conduction abnormalities 1

Risk Assessment

The risk of progression to higher-degree AV block is generally low with isolated first-degree AV block, but the extreme axis deviation raises concern for more extensive conduction system disease 1.

Management Recommendations

Immediate Actions

• No emergency intervention is required for asymptomatic first-degree AV block 1
• Clinical correlation with symptoms is essential (syncope, presyncope, exercise intolerance)

Further Evaluation

1. Complete cardiac workup including:

   • Echocardiogram to assess for structural heart disease
   • Review of current medications
   • Serum electrolyte assessment
   • Consider ambulatory monitoring if symptoms present

2. Family screening may be appropriate as some conduction disorders have genetic components 1

Long-term Monitoring

• Regular follow-up ECGs to monitor for progression of conduction disease
• Symptoms that would warrant urgent reevaluation include:
  • Syncope or presyncope
  • Palpitations
  • Unexplained fatigue
  • Exercise intolerance

Pacing Indications

Permanent pacing is generally NOT indicated for asymptomatic first-degree AV block unless:

• PR interval is extremely prolonged (>300 ms) causing hemodynamic compromise 1
• There is evidence of progression to higher-degree AV block
• Symptoms attributable to AV dyssynchrony are present

Common Pitfalls to Avoid

1. Overdiagnosis: Not all PR interval prolongations require intervention or extensive workup
2. Underestimation: Extreme axis deviation should not be dismissed as a benign finding
3. Medication oversight: Failure to review current medications that may affect AV conduction
4. Incomplete evaluation: Focusing only on the AV block without considering the axis deviation

This EKG demonstrates conduction system abnormalities that, while not requiring immediate intervention in an asymptomatic patient, warrant clinical correlation and appropriate follow-up to monitor for progression of disease.