ECG Academy

ECG Basic – R wave

Clinical calculation support · Verify results before clinical use

Appcardio ECG Academy · ECG Basics

R Wave: Normal Progression and Abnormal Patterns

Understand what the R wave represents, how it normally changes across the precordial leads, and how to approach a dominant R wave in V1 or aVR and poor R-wave progression.

Foundational levelApprox. 8–10 min12-lead ECG
Schematic ECG complex highlighting the R wave A P wave, QRS complex and T wave on a subtle ECG grid. The upward R-wave deflection is highlighted in blue. R wave P QRS T

Original schematic waveform for teaching; not a patient tracing and not drawn to diagnostic scale.

At the end of this lesson

Learning objectives

01 · DefineDescribe the R wave and its relationship to ventricular depolarisation.
02 · RecogniseIdentify the expected precordial R-wave progression and transition zone.
03 · DetectRecognise a dominant R wave in V1 and understand its differential diagnosis.
04 · EvaluateInterpret a prominent terminal R wave in aVR in the appropriate context.
05 · ApproachRecognise poor R-wave progression and avoid common interpretation pitfalls.
01 · Core concept

What is the R wave?

The R wave is the first positive (upward) deflection of the QRS complex. In the supplied ECG Basics reference, it is described as representing early ventricular depolarisation.

QRS nomenclature is based on the direction and sequence of deflections:

  • Q wave: the first negative deflection before any positive deflection.
  • R wave: the first positive deflection.
  • S wave: a negative deflection following an R wave.
  • R′ (R-prime): a second positive deflection after an initial R wave.
RememberA QRS complex does not have to contain all three waves. A complex that is entirely negative is termed a QS complex; a complex with a single positive deflection may be described as an R wave.
02 · Normal pattern

R-wave progression in the chest leads

When reviewing the six precordial leads, assess the sequence from V1 through V6 rather than judging one lead in isolation. In a typical adult tracing, the R wave tends to become larger from the right-sided chest leads toward the left-sided leads, while the S wave tends to become smaller. The point at which the R and S amplitudes become approximately equal is commonly called the transition zone.

Schematic R-wave progression from V1 to V6 Six schematic QRS complexes show a small R and deep S in V1, increasing R amplitude through V4, and a dominant R in V5 and V6. V1V2V3V4V5V6 Illustrative transition region Schematic only

Conceptual illustration of the usual direction of change. Individual tracings vary; this drawing is not a set of diagnostic reference amplitudes.

A practical visual sequence

V1–V2

R waves are often relatively small and S waves relatively deep.

V3–V4

R-wave amplitude generally increases; the transition commonly occurs around this region.

V5–V6

R waves are usually dominant, with smaller terminal S waves or no prominent S wave.

Clinical contextThere is variation with age, body habitus, cardiac position, and technical factors. Do not diagnose infarction or chamber enlargement from R-wave progression alone.
03 · Abnormal pattern

Dominant R wave in V1

A prominent or dominant R wave in V1 is a finding, not a diagnosis. The supplied reference lists several possible explanations, including normal age-related patterns, right ventricular conditions, altered ventricular activation, posterior myocardial infarction, pre-excitation, lead-placement error, and other structural or neuromuscular conditions.

Possible causeClinical / ECG context to consider
Normal variantMay be seen in children and young adults; interpret using age-appropriate ECG standards.
Right ventricular hypertrophy (RVH)Consider the overall right-heart pattern and clinical context, rather than V1 amplitude alone.
Right bundle branch block (RBBB)Altered terminal ventricular activation can produce a prominent terminal positive deflection in V1 (often an rSR′-type pattern).
Posterior myocardial infarctionA tall R wave in V1–V3 may be a reciprocal mirror pattern. The supplied reference points to posterior leads V7–V9 for assessment of ST elevation.
Wolff–Parkinson–White (WPW), type A patternPre-excitation can alter initial QRS forces and produce a dominant R wave in V1.
Lead placement errorIncorrect placement or switching of chest electrodes can create an unexpected pattern; verify landmarks and lead labels.
DextrocardiaConsider when the limb-lead pattern and precordial progression are also abnormal.
Other listed causesHypertrophic cardiomyopathy, muscular dystrophy (including myotonic and Duchenne dystrophy), pulmonary embolism, persistence of an infantile pattern, and left-to-right shunt are included in the source differential.

How to approach a dominant R in V1

  1. Confirm correct patient age, calibration, lead labels, and chest-electrode placement.
  2. Inspect the complete QRS morphology and QRS duration for bundle branch block or pre-excitation clues.
  3. Review the remaining precordial leads for R-wave progression and the limb leads for axis and global patterns.
  4. Look for corroborating clinical and ECG evidence of RVH, posterior infarction, or structural disease.
Posterior infarction reminderWhen posterior MI is suspected, obtain posterior leads (V7–V9) when clinically appropriate. A dominant R wave in V1 is not sufficient by itself to diagnose posterior infarction.
04 · Limb lead finding

Dominant R wave in aVR

A dominant R wave in aVR, particularly a prominent terminal R wave, should prompt consideration of sodium-channel-blocking drug toxicity, dextrocardia, and limb-lead reversal. The supplied LITFL reference also notes that aVR may commonly be elevated in ventricular tachycardia.

Sodium-channel-blocking drug toxicity

In the setting of suspected poisoning with sodium-channel-blocking agents (for example, tricyclic antidepressants), the source describes a characteristic terminal R wave in aVR. It gives the following suggestive features:

  • R-wave height greater than 3 mm.
  • R/S ratio greater than 0.7.
Do not use these values in isolationThese are clues from the supplied educational reference, not a stand-alone toxicology rule-out or rule-in test. Interpret the ECG with the exposure history, QRS duration, haemodynamic status, and the full clinical picture. Suspected poisoning requires urgent toxicology / emergency assessment.

Dextrocardia versus right-arm / left-arm lead reversal

Dextrocardia pattern

  • Positive QRS complexes in aVR, often with upright P and T waves.
  • Negative QRS complexes in lead I, often with inverted P and T waves.
  • Marked right-axis deviation may be present.
  • Absent or reversed R-wave progression, with dominant S waves across the chest leads.

RA–LA limb-lead reversal

  • Lead I becomes inverted.
  • Leads aVR and aVL exchange appearances.
  • Leads II and III exchange appearances.
  • Precordial R-wave progression is generally preserved because chest electrodes remain in place.
Useful discriminatorBoth conditions can mimic one another in the limb leads. Preserved normal precordial R-wave progression favours limb-lead reversal; absent/reversed progression supports consideration of dextrocardia. Confirm by checking electrode placement and, when indicated, repeating the ECG with right-sided chest leads.
05 · Abnormal progression

Poor R-wave progression

The supplied reference describes poor R-wave progression as an R-wave amplitude of 3 mm or less in V3. It lists prior anteroseptal myocardial infarction, left ventricular hypertrophy (LVH), inaccurate lead placement, and a normal variant as possible causes.

Schematic comparison of expected and poor R-wave progression Two rows of schematic QRS complexes across V1 to V6. The upper row shows increasing R waves. The lower row shows persistently small R waves. Usual patternPoor progression V1V2V3V4V5V6V1V2V3V4V5V6

Original conceptual illustration only. Real ECG amplitude and morphology are variable; compare with the patient's prior tracing where available.

Causes listed in the source

  • Previous anteroseptal myocardial infarction.
  • Left ventricular hypertrophy.
  • Incorrect precordial lead placement.
  • Normal variant.

The source also notes that absent R-wave progression is characteristically seen in dextrocardia. This should be considered alongside limb-lead findings and the overall clinical context.

Threshold caveatThe ≤3 mm at V3 description is the operational definition stated by the supplied LITFL page. R-wave progression has multiple definitions in clinical literature and should not be treated as a universal isolated diagnostic criterion.
06 · Bedside workflow

A systematic approach to R-wave abnormalities

1
Check technical quality.
Confirm standard calibration, lead labels, and correct placement of V1–V6 and limb electrodes.
2
Follow the sequence.
Trace R and S amplitudes from V1 through V6 and identify the transition region.
3
Describe the abnormality precisely.
State whether there is a dominant R in V1, a terminal R in aVR, poor progression, or absent/reversed progression.
4
Search for supporting features.
Assess QRS duration and morphology, axis, ST–T changes, and other leads rather than relying on one waveform feature.
5
Integrate clinical context.
Consider age, symptoms, medications / possible ingestion, prior ECGs, and relevant cardiac or pulmonary history.
07 · Knowledge check

Test your understanding

A 32-year-old patient has a prominent terminal R wave in aVR. Which clinical context makes sodium-channel-blocking drug toxicity an important consideration?
An ECG has an inverted lead I and an unusual positive aVR. Which additional feature favours right-arm / left-arm lead reversal over dextrocardia?
08 · Review

Key takeaways

  • The R wave is the first positive deflection of the QRS complex and represents early ventricular depolarisation in the supplied reference.
  • In a typical adult ECG, R-wave amplitude generally increases from V1 toward the left precordial leads, with a transition region often around V3–V4.
  • A dominant R wave in V1 has a broad differential: normal age-related patterns, RVH, RBBB, posterior MI, WPW type A, lead-placement error, dextrocardia, and other listed conditions.
  • A prominent terminal R wave in aVR can be a clue to sodium-channel-blocking drug toxicity; the supplied source gives R height >3 mm and R/S ratio >0.7 as suggestive features.
  • Poor R-wave progression is nonspecific. Check electrode placement and interpret the whole ECG before assigning a cause.
  • Dextrocardia and RA–LA lead reversal may resemble one another in limb leads; precordial progression helps distinguish them.
Further reading

References

Cadogan M. R wave. Life in the Fast Lane (LITFL), ECG Library Basics. Published August 1, 2020. https://litfl.com/r-wave-ecg-library/. Accessed November 9, 2026. Primary supplied educational reference. Licensed under CC BY-NC-SA 4.0; this lesson uses independently written explanations and original schematic artwork, not the source's ECG images.
Straus DG, Schocken DD. Marriott’s Practical Electrocardiography. 13th ed. Wolters Kluwer; 2021. Listed as a recommended textbook in the supplied LITFL reading section.
Surawicz B, Knilans TK. Chou’s Electrocardiography in Clinical Practice: Adult and Pediatric. 6th ed. Elsevier; 2008. Listed as a recommended textbook in the supplied LITFL reading section.
Brady WJ, Lipinski MJ, et al. Electrocardiogram in Clinical Medicine. 1st ed. Elsevier; 2020. Listed as a recommended textbook in the supplied LITFL reading section.
Medical education disclaimer: This page is intended for educational purposes for healthcare professionals and learners. ECG findings must be interpreted in the context of the patient's presentation and the complete tracing. This material does not replace clinical judgement, local protocols, specialist consultation, or urgent assessment when a serious condition or poisoning is suspected.
HELP IMPROVE APPCARDIO

Found an issue or want to document this calculation?