[Durgical](https://durgical.com/en/) › [DurgiPedia](https://durgical.com/en/durgipedia/) › [Physiology](https://durgical.com/en/physiology/) › [Cardiovascular](https://durgical.com/en/physiology/areas/cardio/) › The ECG in chamber hypertrophy and low-voltage states

# The ECG in chamber hypertrophy and low-voltage states

- Measurement
- Exam priority: medium

More heart muscle makes bigger ECG waves; fluid, air, fat or scar between heart and skin makes them smaller.

Updated Nov 13, 2026

Also called: LVH voltage criteria, Right ventricular hypertrophy, Low QRS voltage, Electrical alternans

**See it in 3D:** [Left ventricle](https://durgical.com/en/anatomy/left-ventricle/) · [Right ventricle](https://durgical.com/en/anatomy/right-ventricle/) · [Left atrium](https://durgical.com/en/anatomy/left-atrium/) · [Right atrium](https://durgical.com/en/anatomy/right-atrium/) · [Pericardium](https://durgical.com/en/anatomy/pericardium/)

## Key points

- LVH (Sokolow–Lyon): S in V1 + R in V5 or V6 ≥ 3.5 mV (35 mm); Cornell: R in aVL + S in V3 > 2.8 mV in men, > 2.0 mV in women.
- LVH 'strain': ST depression and T inversion in lateral leads opposite to the tall R.
- RVH: right axis deviation, R ≥ S in V1, deep S in V5–V6; typical in pulmonary hypertension and mitral stenosis.
- Atrial enlargement: right gives tall peaked P in II (≥ 0.25 mV); left gives a wide notched P (≥ 0.12 s) and a deep negative end of P in V1.
- Low voltage: QRS

## What it is

QRS voltage depends on how much muscle depolarizes and how well the current reaches the skin. A thick ventricle raises voltage and pulls the axis toward itself; a dilated or thick ventricle also takes longer to activate, widening the QRS slightly. Low voltage appears when muscle is lost or when tissue or fluid around the heart damps the signal.

## How it works, step by step

- Pressure overload (hypertension, aortic stenosis) adds sarcomeres in parallel: the wall thickens and more muscle depolarizes at once.
- A bigger muscle mass makes a longer vector toward that side: tall R over the hypertrophied ventricle, deep S on the opposite side.
- The thick wall takes longer to activate from endocardium to epicardium, so the QRS widens a little (usually

### Electrocardiogram: a normal beat in lead II

**HR** 75 /min **RR** 0.80 s **PR** 0.16 s **QRS** 0.09 s **QT** 0.37 s **QTc** 0.41 s

Tap a wave (P, QRS, T, U), an interval (PR, ST, QT) or the RR.

- ECG trace (lead II)
- Small box: 0.04 s · 0.1 mV
- Big box: 0.20 s · 0.5 mV
- Selected part

The normal lead II beat: compare the R height with the 0.5 mV big box when judging high or low voltage.

## ECG thresholds (adult, standard calibration 10 mm/mV)

| Parameter | Value | Note |
| --- | --- | --- |
| Sokolow–Lyon LVH | S V1 + R V5/V6 ≥ 3.5 mV | less specific under ≈ 40 years |
| Cornell LVH | R aVL + S V3 > 2.8 mV (men), > 2.0 mV (women) | |
| Right atrial P (lead II) | ≥ 0.25 mV tall | |
| Left atrial P (lead II) | ≥ 0.12 s wide, notched | |
| Low voltage, limb leads | QRS

| Pattern | Key ECG features | Typical causes |
| --- | --- | --- |
| [Left ventricular hypertrophy](https://durgical.com/en/conditions/hypertensive-heart-disease/) | Tall lateral R, deep S V1–V2, left axis, lateral strain | Hypertension, aortic stenosis, hypertrophic cardiomyopathy |
| [Right ventricular hypertrophy](https://durgical.com/en/conditions/pulmonary-hypertension-and-cor-pulmonale/) | Right axis, tall R V1, deep S V6, right strain | Pulmonary hypertension, mitral stenosis, chronic lung disease |
| [Low voltage](https://durgical.com/en/conditions/cardiac-tamponade/) | Small QRS in all limb or all chest leads | Effusion, emphysema, obesity, hypothyroidism, amyloid, old infarcts |
| [Electrical alternans](https://durgical.com/en/conditions/cardiac-tamponade/) | Beat-to-beat change in QRS height | Large pericardial effusion; partial intraventricular block at fast rates |

## Clinical notes

- Voltage criteria are specific but insensitive: a normal ECG does not exclude LVH; echocardiography measures wall thickness directly.
- Young, thin people often exceed voltage criteria without hypertrophy because the heart lies close to the chest wall.
- A falling QRS voltage over days in a patient with pericarditis suggests the effusion is growing.

## Memory aid

Volume of muscle turns the volume up; fluid, air and fat turn it down.

## Test yourself

Think of the answer, then tap the question to see it.

## A hypertensive patient has S in V1 of 1.6 mV and R in V5 of 2.2 mV with lateral ST depression. What does this suggest?

Left ventricular hypertrophy with strain: the Sokolow–Lyon sum is 3.8 mV (≥ 3.5 mV), and the lateral ST–T changes oppose the tall R.

## Why does right ventricular hypertrophy change the ECG later than left ventricular hypertrophy?

The normal left ventricle is much thicker and dominates the QRS vector. The right ventricle must thicken a lot before its vector outweighs the left and moves the axis right.

## A patient with dyspnea has sinus tachycardia, low QRS voltage and QRS height alternating beat to beat. What is the likely cause?

A large pericardial effusion, likely with tamponade: fluid damps the voltage and the heart swinging in the fluid makes the alternans.

## Which three causes of low QRS voltage do not involve the heart muscle itself?

Pericardial effusion, emphysema (air in hyperinflated lungs), obesity; pleural effusion and poor electrode contact also lower voltage.

[Add to my cards (4)](https://durgical.app/estudiar/?add=/en/physiology/the-ecg-in-chamber-hypertrophy-and-low-voltage-states/)

[More Physiology questions →](https://durgical.com/en/practice/?f=physiology)

## Connections

## See it in 3D 5

The structures of Durgical's 3D anatomy where it happens.

- [Left ventricle](https://durgical.com/en/anatomy/left-ventricle/)
- [Right ventricle](https://durgical.com/en/anatomy/right-ventricle/)
- [Left atrium](https://durgical.com/en/anatomy/left-atrium/)
- [Right atrium](https://durgical.com/en/anatomy/right-atrium/)
- [Pericardium](https://durgical.com/en/anatomy/pericardium/)

## Related topics 5

- [The cardiac electrical axis](https://durgical.com/en/physiology/the-cardiac-electrical-axis/)
- [ECG basics: waves, intervals and leads](https://durgical.com/en/physiology/ecg-basics-waves-intervals-and-leads/)
- [How ECG waves are built: the vectors of the QRS, T and P](https://durgical.com/en/physiology/how-ecg-waves-are-built-the-vectors-of-the-qrs-t-and-p/)
- [Preload, afterload and contractility](https://durgical.com/en/physiology/preload-afterload-and-contractility/)
- [Physiology of hypertension](https://durgical.com/en/physiology/physiology-of-hypertension/)

## Related conditions 8

- [Hypertensive heart disease](https://durgical.com/en/conditions/hypertensive-heart-disease/)
- [Aortic Valve Stenosis](https://durgical.com/en/conditions/aortic-valve-stenosis/)
- [Hypertrophic cardiomyopathy](https://durgical.com/en/conditions/hypertrophic-cardiomyopathy/)
- [Pulmonary hypertension and cor pulmonale](https://durgical.com/en/conditions/pulmonary-hypertension-and-cor-pulmonale/)
- [Mitral stenosis](https://durgical.com/en/conditions/mitral-stenosis/)
- [Cardiac tamponade](https://durgical.com/en/conditions/cardiac-tamponade/)
- [Chronic obstructive pulmonary disease (COPD)](https://durgical.com/en/conditions/chronic-obstructive-pulmonary-disease/)
- [Hypothyroidism](https://durgical.com/en/conditions/hypothyroidism/)

[← All of physiology](https://durgical.com/en/physiology/)

Educational physiology content; not a diagnostic or treatment guide and no substitute for a health professional's advice. Values are approximate references. No doses are given.

Sources: [Hypertensive Heart Disease](https://www.ncbi.nlm.nih.gov/books/NBK539800/) (StatPearls (NCBI Bookshelf), 2025); [Cardiac Tamponade](https://www.ncbi.nlm.nih.gov/books/NBK431090/) (StatPearls (NCBI Bookshelf), 2025); [Chronic Obstructive Pulmonary Disease (COPD)](https://www.ncbi.nlm.nih.gov/books/NBK559281/) (StatPearls (NCBI Bookshelf), 2025).

## **Spotted a mistake?** We are always improving for the community. Tell us what is wrong and our team will review it. Report a mistake

Representative model, for educational purposes only.

---
Source: https://durgical.com/en/physiology/the-ecg-in-chamber-hypertrophy-and-low-voltage-states/
License: CC BY 4.0 (https://creativecommons.org/licenses/by/4.0/). Cite as: DurgiPedia (durgical.com), https://durgical.com/en/physiology/the-ecg-in-chamber-hypertrophy-and-low-voltage-states/