Notching in electrocardiography

ECG with notching of the ascending branch of the QRS complex in leads aVL and aVF and Tachycardia of about 100 beats per minute.

Notching in electrocardiography refers to the presence of distinct deflections or irregularities in the waveform of an electrocardiogram (ECG or EKG), particularly within the P wave, QRS complex (fragmented QRS (fQRS)), or T wave. ^[1] These notches appear as abrupt changes in the direction or slope of the waveform and can provide critical diagnostic information about cardiac conditions. ^{[2] [3]}

Notching in different components of the ECG waveform is associated with various cardiac conditions, ranging from benign variants to serious pathologies, such as conduction delays, atrial fibrillation, ^[4] myocardial ischemia, ^[5] or structural heart disease ('crochetage sign' in atrial septal defect (ASD)). ^{[3] [6] [7] [8] [9] [10]}

Changes in left bundle branch block (LBBB) during myocardial ischemia

Definition, characteristics

Notching is identified as an abrupt change in the direction of an ECG waveform, resulting in a "notch" or dip that creates a bimodal or M-shaped appearance. It is distinct from slurring, which involves a smooth transition or slowing in the slope of the waveform without a clear change in direction. ^[11] Notching can occur in the following ECG components:

Ventricular tachycardia (VT) vs Supraventricular tachycardia (SVT) in wide complex tachycardia with LBBB configuration

• P Wavenotching: A notched P wave typically appears as a double-peaked or M-shaped wave in lead II, often reflecting delayed atrial conduction or left atrial enlargement. A notched P wave is defined by a peak-to-peak distance of ≥20 ms or ≥40 ms, depending on the diagnostic criteria used. ^{[12] [13]}
• QRScomplex notching: Notching in the QRS complex is characterized by additional deflections or peaks within the QRS waveform, often in the form of multiple R waves or notches in the R or S waves. It is commonly associated with conduction abnormalities, such as bundle branch blocks, early repolarization. It is also associated with cardiac resynchronization therapy , atrial septal defect, myocardial infarction, or myocardial scarring. ^[14]
• Twave notching: A notched T wave appears as a biphasic or double-peaked T wave, often linked to conditions like long QT syndrome type 2 (LQTS2) or electrolyte imbalances. ^[15]

Notching is typically assessed using a standard 12-lead ECG, with modern systems employing digital analysis at high sampling rates (e.g., 500 Hz) to detect subtle notches that may be missed in conventional recordings. High-frequency ECG techniques can enhance the visibility of notching, particularly in the QRS complex.

Mechanisms

Notching in ECG waveforms arises from disruptions in the normal sequence of cardiac depolarization or repolarization. Specific mechanisms include:

• Atrialconduction delay: Notched P waves result from delayed or asynchronous atrial activation, often due to left atrial enlargement or fibrosis, which slows intra-atrial conduction. ^[16]
• Ventricularconduction abnormalities: QRS notching in bundle branch blocks is caused by delayed conduction through the Purkinje system, leading to asynchronous ventricular depolarization. ^[17] In LBBB, the left ventricular lateral wall is depolarized last, producing notching in lateral leads. ^[18]
• Myocardialscarring: Notching in ischemic heart disease reflects local conduction delays due to myocardial scarring or fibrosis, altering the QRS contour. HF ECGs can detect subtle notches obscured in standard recordings. ^[19]
• Ionchannel dysfunction: T-wave notching in LQTS2 is linked to reduced potassium currents (e.g., IKr), which prolong repolarization and create a biphasic T-wave morphology. ^[20]
• Structuralheart disease: Conditions like ASD cause notching (e.g., crochetage sign) due to altered ventricular activation patterns secondary to volume overload. ^[21]

References

1. Take, Yutaka; Morita, Hiroshi (September 2012). "Fragmented QRS: What Is The Meaning?". Indian Pacing and Electrophysiology Journal. 12 (5): 213–225. doi:10.1016/s0972-6292(16)30544-7. PMC   3443879 . PMID   23071383.
2. Haukilahti, M. Anette E.; Eranti, Antti; Kenttä, Tuomas; Huikuri, Heikki V. (26 December 2016). "QRS Fragmentation Patterns Representing Myocardial Scar Need to Be Separated from Benign Normal Variants: Hypotheses and Proposal for Morphology based Classification". Frontiers in Physiology. 7: 653. doi: 10.3389/fphys.2016.00653 . PMC   5183580 . PMID   28082919.
3. Bhattacharyya, Pranab Jyoti (8 October 2016). "'Crochetage' sign on ECG in secundum ASD: clinical significance". BMJ Case Reports. 2016: bcr2016217817. doi:10.1136/bcr-2016-217817. PMC   5073604 . PMID   28049121.
4. Okuyama, Takafumi; Kabutoya, Tomoyuki; Kario, Kazuomi (June 2024). "Notched P-wave on digital electrocardiogram predicts the recurrence of atrial fibrillation in patients who have undergone catheter ablation". Journal of Arrhythmia. 40 (3): 472–478. doi:10.1002/joa3.13050. PMC   11199840 . PMID   38939783.
5. France, R. J.; Formolo, J. M.; Penney, D. G. (March 1990). "Value of notching and slurring of the resting QRS complex in the detection of ischemic heart disease". Clinical Cardiology. 13 (3): 190–196. doi:10.1002/clc.4960130309. PMID   2323119.
6. Fernandez Hazim, Carol; Shaban, Mohammed; Cordero, Dessiree; Urena Neme, Ana P; Rodriguez Guerra, Miguel A (4 October 2023). "Crochetage, the Forgotten Electrocardiographic Sign". Cureus. 15 (10): e46498. doi: 10.7759/cureus.46498 . PMC   10624559 . PMID   37927770.
7. Shen, Lei; Liu, Jian; Li, Jin-kang; Xu, Meng; Yuan, Lang; Zhang, Guo-qin; Wang, Jian-yi; Huang, Yu-juan (June 2018). "The Significance of Crochetage on the R wave of an Electrocardiogram for the Early Diagnosis of Pediatric Secundum Atrial Septal Defect". Pediatric Cardiology. 39 (5): 1031–1035. doi:10.1007/s00246-018-1857-0. PMID   29564520.
8. Lane, Kory; Layell, Roger L (February 2022). "Crochetage Sign". EMS World.
9. Smith, Steve (2020-01-08). "A young woman with epigastric pain. ECG Crochetage sign? What is the significance?". Dr. Smith's ECG Blog. Retrieved 2025-06-09.^{[ self-published source? ]}
10. Heng, Sijie Jacob; Clark, Elaine N.; Macfarlane, Peter W. (September 2012). "End QRS Notching or Slurring in the Electrocardiogram". Journal of the American College of Cardiology. 60 (10): 947–948. doi:10.1016/j.jacc.2012.03.061. PMID   22796253.
11. Macfarlane, Peter W.; Clark, Elaine N. (2013). "ECG measurements in end QRS notching and slurring". Journal of Electrocardiology. 46 (5): 385–389. doi:10.1016/j.jelectrocard.2013.06.011. PMID   23866291.
12. CORP, ROINOVA. "EKGDX - The P waves". EKGDX. Retrieved 2025-06-09.
13. Kabutoya, Tomoyuki; Hoshide, Satoshi; Kario, Kazuomi (2022). "Notched P-Wave on Digital Electrocardiogram Predicts Cardiovascular Events in Patients with Cardiovascular Risks: The Japan Morning Surge Home Blood Pressure Study". Cardiology. 147 (3): 307–314. doi:10.1159/000522508. PMID   35152222.
14. Take, Yutaka; Morita, Hiroshi (September 2012). "Fragmented QRS: What Is The Meaning?". Indian Pacing and Electrophysiology Journal. 12 (5): 213–225. doi:10.1016/s0972-6292(16)30544-7. PMC   3443879 . PMID   23071383.
15. Kenny, Brian J.; Brown, Kristen N. (2025). "ECG T Wave". StatPearls. StatPearls Publishing. PMID   30855852.
16. Okuyama, Takafumi; Kabutoya, Tomoyuki; Kario, Kazuomi (June 2024). "Notched P-wave on digital electrocardiogram predicts the recurrence of atrial fibrillation in patients who have undergone catheter ablation". Journal of Arrhythmia. 40 (3): 472–478. doi:10.1002/joa3.13050. PMC   11199840 . PMID   38939783.
17. Blondeel, Maarten; Robyns, Tomas; Willems, Rik; Vandenberk, Bert (9 January 2025). "Ventricular Depolarization Abnormalities and Their Role in Cardiac Risk Stratification — A Narrative Review". Reviews in Cardiovascular Medicine. 26 (1): 25921. doi:10.31083/RCM25921. PMC   11759958 . PMID   39867187.
18. Arnold, Ahran D.; Whinnett, Zachary I.; Vijayaraman, Pugazhendhi (November 2020). "His-Purkinje Conduction System Pacing: State of the Art in 2020". Arrhythmia & Electrophysiology Review. 9 (3): 136–145. PMC   7675135 . PMID   33240509.
19. Noordman, Alwin B. P.; Maass, Alexander H.; Groenveld, Hessel; Mulder, Bart A.; Rienstra, Michiel; Blaauw, Yuri (17 August 2021). "Myocardial Scar Characterization and Future Ventricular Arrhythmia in Patients With Ischemic Cardiomyopathy and an Implantable Cardioverter-Defibrillator". Frontiers in Cardiovascular Medicine. 8. doi: 10.3389/fcvm.2021.708406 . PMC   8415981 . PMID   34485409.
20. Porta-Sánchez, Andreu; Spillane, David R.; Harris, Louise; Xue, Joel; Dorsey, Pat; Care, Melanie; Chauhan, Vijay; Gollob, Michael H.; Spears, Danna A. (April 2017). "T-Wave Morphology Analysis in Congenital Long QT Syndrome Discriminates Patients From Healthy Individuals". JACC: Clinical Electrophysiology. 3 (4): 374–381. doi:10.1016/j.jacep.2016.10.013. PMID   29759450.
21. Schiavone, William A.; Majdalany, David S. (29 March 2024). "The Value of the Electrocardiogram in Adult Congenital Heart Disease". Journal of Personalized Medicine. 14 (4): 367. doi: 10.3390/jpm14040367 . PMC   11051035 . PMID   38672995.