Deep S waves in high-lateral ECG leads
Deep S waves in the left-sided leads (I, aVL, and V5–V6) most commonly indicate an increased right-sided electrical vector, which is seen with right ventricular hypertrophy (RVH) or right axis deviation. [1] Deep S waves in these leads also have diagnostic relevance for RVH voltage criteria when paired with right-sided precordial R-wave findings. [1]
Primary physiologic interpretation
The S wave represents ventricular depolarization moving away from the lead during the QRS complex. [2] Deep S waves in I/aVL and V5–V6 occur when electrical forces shift toward the right ventricle relative to the left ventricle. [1]
Most likely clinical meaning
Right ventricular hypertrophy
- Deep S waves in V5 and V6 are part of published ECG voltage criteria for RVH. [1]
- In RVH, left precordial leads (V5–V6) tend to show deep S waves because right ventricular forces become predominant. [1]
- In ECG summaries of RVH, deep S waves in V5–V6 with tall R waves in V1–V2 support RVH pattern recognition. [2]
Right axis deviation
- A left-sided pattern with prominent negative deflection (including deep S in limb leads such as I/aVL) can accompany a shifted frontal-plane axis consistent with RVH-related electrical dominance. [2]
Lead misplacement or positional artifact
- Apparent voltage abnormalities should prompt consideration of incorrect lead placement or sudden morphology changes across leads, since these can produce misleading wave patterns. [3]
Electrocardiographic pattern elements that refine specificity
Published RVH criteria often combine left-lead S-wave amplitudes with right-lead R-wave amplitudes. [1] The AHA electrocardiogram standardization statement describes RVH criteria including deep S in V5 with thresholds and additional combined criteria using limb leads (including aVL) with right precordial findings. [1]
Common differential considerations
The RVH pattern described above can be seen with non-RVH causes of altered QRS forces, including conditions that change cardiac rotation or induce right-sided strain patterns. [2] Differential diagnosis should be guided by the full ECG pattern, including right precordial R-wave amplitude and repolarization changes. [2]
Practical next diagnostic step
Echocardiography is recommended for confirmation of suspected RVH or other structural heart disease when ECG voltage patterns suggest RVH, because ECG criteria for chamber hypertrophy have limited sensitivity. [1] Further evaluation for causes of right-sided pressure or volume overload (eg, pulmonary hypertension or congenital heart disease) is indicated when RVH pattern is supported clinically. [2]