What are the ECG differences between left ventricular hypertrophy (LVH) and left ventricular dilatation (LVD)?

ECG Differences Between Left Ventricular Hypertrophy and Left Ventricular Dilatation

Left ventricular hypertrophy (LVH) and left ventricular dilatation (LVD) produce distinct ECG patterns: LVH primarily shows increased QRS voltage with delayed ventricular activation time (VAT), while isolated LVD demonstrates increased net QRS area without significant voltage increases or VAT prolongation. 1

Key Distinguishing ECG Features

Left Ventricular Hypertrophy (Concentric)

Voltage criteria are the hallmark of concentric LVH, with multiple validated thresholds available 2:

• Increased QRS amplitude in specific leads, particularly:

  • Sokolow-Lyon Index: S wave in V1 + R wave in V5 or V6 ≥ 3.5 mV 2
  • Cornell Voltage: S wave in V3 + R wave in aVL > 2.8 mV (men) or > 2.0 mV (women) 2
  • R wave in aVL > 1.1 mV 2

• Prolonged ventricular activation time (VAT) is a critical distinguishing feature of concentric hypertrophy, reflecting delayed local activation through thickened myocardium 1

• Secondary ST-T abnormalities (lateral ST depression with T wave inversion), previously termed "strain pattern," indicate more severe LVH 3, 2

• Left atrial abnormalities frequently accompany LVH and may be the earliest ECG sign of hypertensive heart disease 3, 2

• Left axis deviation (QRS axis more negative than -30°) may be present 2

Left Ventricular Dilatation (Isolated)

The primary ECG marker of isolated LVD is increased net QRS area (AQRSmax) rather than voltage amplitude 1:

• Increased QRS area correlates well with LV internal dimension (r = 0.73) 1

• Normal or minimally increased QRS voltage, distinguishing it from concentric LVH 1, 4

• Normal ventricular activation time, unlike the prolonged VAT seen in concentric hypertrophy 1

• Horizontal plane QRS loop configuration differs from concentric LVH, with proximal-distal loop area relationships helping distinguish the two patterns 4

Clinical Algorithm for Differentiation

When evaluating ECG for LV enlargement, follow this approach:

1. Assess QRS voltage first: High voltage suggests concentric LVH rather than isolated dilatation 1, 4

2. Measure ventricular activation time: Prolonged VAT (particularly VAT-Darea, the area size where departure indices of VAT are >2) strongly indicates concentric hypertrophy 1

3. Evaluate QRS area: Increased net QRS area with normal voltage suggests isolated dilatation 1

4. Check for secondary ST-T changes: Their presence indicates more severe concentric LVH 3, 2

5. Look for left atrial abnormalities: These accompany concentric LVH more than isolated dilatation 3, 2

Important Caveats and Pitfalls

The ECG has limited sensitivity for detecting LVH (21-50% depending on criteria used) despite high specificity (95%) 5. This means:

• When true LVH prevalence is less than 10%, more false-positive than true-positive diagnoses will occur 5
• Echocardiography is superior to ECG for clinical diagnosis of LVH, with 93% sensitivity and 95% specificity 5

Bundle branch blocks significantly complicate ECG interpretation 6, 2:

• In complete LBBB, ECG diagnosis of LVH should generally not be attempted, but if necessary, use QRS duration > 155 ms combined with precordial voltage criteria (SV2 + RV6 > 4.5 mV has 86% sensitivity and 100% specificity) 2, 7
• The diagnosis of LVH in the presence of complete LBBB should be made with caution due to conflicting evidence 6, 3

Left anterior fascicular block (LAFB) affects voltage criteria: R-wave amplitude in leads I and aVL are not reliable for LVH diagnosis when LAFB is present; use criteria incorporating S wave depth in left precordial leads (V5, V6) instead 2, 8

Body surface mapping improves diagnostic performance over standard 12-lead ECG by incorporating spatial distribution of VAT prolongation and QRS voltage, achieving better correlation with wall thickness (r = 0.73) and LV internal dimension (r = 0.73) 1