Can a ventricular (V)-paced rhythm have right axis deviation?

Can a V-Paced Rhythm Have Right Axis Deviation?

Yes, ventricular paced rhythms can absolutely exhibit right axis deviation, and the specific axis depends primarily on the location of the pacing lead and the underlying cardiac substrate.

Understanding V-Paced QRS Axis Patterns

Right Ventricular Apical Pacing

• RV apical pacing typically produces a left superior axis (right superior quadrant), not right axis deviation 1
• During biventricular pacing with RV apical lead, the frontal plane QRS axis is usually in the right superior quadrant and occasionally in the left superior quadrant 1
• This is the most common pacing configuration and does not typically show right axis deviation 1

Right Ventricular Outflow Tract Pacing

• RV outflow tract pacing commonly produces right axis deviation 1
• During biventricular pacing with the RV lead in the outflow tract, the paced QRS in lead V1 is often negative and the frontal plane paced QRS axis is often directed to the right inferior quadrant (right axis deviation) 1
• This represents a predictable pattern based on the superior location of the pacing site 1

Clinical Context: When Right Axis Deviation Matters

Biventricular Hypertrophy Recognition

• Right axis deviation in the presence of left ventricular hypertrophy criteria suggests biventricular hypertrophy 2
• Look for prominent S waves in V5 or V6, unusually tall biphasic R/S complexes in several leads, and signs of right atrial abnormality 3
• This combination has low ECG sensitivity due to cancellation of opposing QRS vectors 3

Right Ventricular Overload Patterns

• Right axis deviation (≥90°) is required for diagnosis of right ventricular hypertrophy in nearly all cases 3, 4
• Pressure overload pattern includes predominantly tall R waves in right precordial leads, right axis deviation, and ST depression with T-wave inversion in right precordial leads 3, 4
• Volume overload pattern shows right axis deviation with findings similar to incomplete right bundle branch block 3, 4

Common Pitfalls in V-Paced Rhythm Interpretation

Lead Position Matters

• Incorrect placement of lead V1 (too high on the chest) can alter QRS morphology interpretation 1
• During biventricular pacing, a negative QRS in V1 may reflect heterogeneous biventricular substrate activation rather than lead malposition, unless middle cardiac vein pacing or dual RV leads are present 1

Fusion Beats Create Confusion

• Ventricular fusion with native conduction during biventricular pacing causes QRS narrowing that simulates appropriate biventricular capture 1
• This represents a common pitfall in device follow-up and can mask the true paced axis 1
• Elimination of fusion by shortening the AV delay often associates with clinical improvement 1

Age-Specific Axis Considerations

Adult Criteria

• Normal QRS axis: 30° to 90° 2
• Moderate right axis deviation: 90° to 120° 2
• Marked right axis deviation: 120° to 180° 2, 5

Pediatric Criteria

• Neonates: normal axis 30° to 190°; extreme right axis 190° to 90° 2
• Ages 1 month to 1 year: normal axis 10° to 120° 2
• Ages 1 to 5 years: normal axis 5° to 100° 2
• Do not apply adult criteria to pediatric patients 5

Practical Algorithm for V-Paced Axis Interpretation

1. Identify the pacing lead location (RV apex vs. outflow tract vs. biventricular) 1
2. Measure the frontal plane QRS axis using standard criteria 2, 5
3. Assess for fusion beats by evaluating QRS width and morphology consistency 1
4. Evaluate for underlying structural disease including biventricular hypertrophy or RV overload 3, 4
5. Consider lead malposition if axis is inconsistent with expected pattern for lead location 1