Bachmann's bundle

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A Moment in History

William S. Halsted, MD
(1852 – 1922)

American anatomist, teacher, and surgeon, William Stewart Halsted was born in New York City, USA to a wealthy family of English origin. His father was involved in charitable work and Governor and trustee to a city hospital. Not a brilliant student initially, Halsted took an undergraduate in Liberal Arts in Yale, CT., after which he entered the Medical College of Physicians at the Columbia College, where he excelled.

As a second-year medical student Halsted applied and obtained a position in surgery at a local hospital. In here he learned about Lister’s antiseptic technique and became an adamant proponent of it to reduce infection. In 1877 Halsted obtained his MD. After a short time as House Physician at the New York Hospital, Halsted traveled to Europe to further his education studying for two years at the Universities of Vienna, Leipzig, and W?rzburg.

Besides being at the forefront of surgical and antiseptic techniques (introducing the use of rubber gloves in surgery), Halsted was extremely concerned with the way medical students were taught in the US. He pioneered bedside clinical round discussions with the medical students after two years of basic sciences studies. Halsted developed the idea of a patient chart; he also developed the residency program for medical students in use today.

Halsted is probably the most influential researcher and surgeon at the turn of the century. He dedicated time to the study of intestinal anastomoses and the use of silk as a suture material. His experimental work in 1887 proved that the inclusion of the submucosa layer in an anastomosis was mandatory, as well that a single layered anastomosis was enough to attain closure. Perhaps Halsted’s most important contribution was the application and use of the scientific method to surgical questions. Halsted’s principles, also known as "Halsted's Rules of Surgery", set the standards used today in surgical suturing and surgical stapling.

He also pioneered the development and surgical techniques for radical mastectomy as a treatment for breast cancer.

As a side effect of this studied in anesthesia and the use of cocaine for anesthesia, Halsted became addicted to this substance, a problem that followed him through the years. Without impairing his capacity as a researcher and a surgeon, Halsted eventually recovered. He died in Baltimore in 1922 as a complication to surgery.

Sources:
1. Dubay, A. D., & Franz, G. M. (2003). Acute Wound Healing: The Biology of Acute Wound Failure. Surg Clin NA, 83, 463-481.
2. Halsted, W. S. (1887). Circular Suture of the Intestine - An Experimental Study. Am J Med Sci, 436-461.
3. “William Stewart Halsted: his life and contributions to surgery” Osborne, P. Lancet Oncol 2007; 8: 256–65
4. “William Stewart Halsted: Surgical pioneer” Burress, P Endoc Today (2010), 8: (2) 22
5. “William Stewart Halsted (1852–1922) Neurological stamp” Haas, LF J Neurol Neurosurg Psych 2000;69:641
Original image courtesy of "Images from the History of Medicine" at www.nih.gov

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Details: Written by: Efrain A. Miranda, Ph.D.; Published: December 15, 2025

Click for a larger image

The term “Bachmann’s bundle” refers to an eponymic structure associated with Jean George Bachmann (1877-1959) a French physician and physiologist. The proper anatomical term for this structure is “interatrial bundle” (Lat. fasciculus interatrialis).

In 1916 Bachmann published a paper titled “The Inter-Auricular Time Interval” in the American Journal of Physiology. He measured activation times between the right and left atria and demonstrated that interruption of this distinct anterior interatrial muscular band resulted in delayed left atrial activation. He concluded that this band constituted the principal route for rapid interatrial conduction. The image, from his original publication, shows a dog’s heart with Bachmann’s bundle.

Bachmann’s bundle is a broad, flat band of atrial myocardium that crosses the superior aspect of the interatrial sulcus. It extends from the right atrium close to the junction of the right atrial appendage and the superior vena cava, and courses leftward across the interatrial groove to insert into the base of the left atrial appendage and the anterosuperior left atrial wall. The bundle is well-delineated and in most cases, a fine fatty layer is interposed between the underlying myocardium and the bundle.

This bundle contains predominantly longitudinally oriented myocardial fibers, aiding in fast passage of the electrical depolarization from the right atrium to the left atrium. This explains why, under normal conditions, the left atrium contracts only milliseconds after the right atrium. Bachmann's bundle is one of the components of the cardiac conduction system, and forms part of the specialized bundles of myocardial tissue that take the electrical impulses from the sinoatrial node to the atrioventricular node and the left atrium,

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When Bachmann’s bundle is intact, left atrial activation is almost simultaneous with the right atrium. If it is damaged, it can cause varying degrees of interatrial block (IAB), and electrical conduction must proceed through other less effective pathways, resulting in atrial dyssynchrony and altered cardiac rhythm. Advanced IAB is strongly associated with atrial fibrillation, left atrial mechanical dysfunction, and increased risk of stroke even in sinus rhythm.

IAB can be caused by fibrosis, fatty infiltration, atrial dilation, aging, ischemia, and iatrogenic damage in prior cardiac surgery or ablation. All these preferentially affect the anterosuperior interatrial region, explaining the bundle’s vulnerability.

There are anatomical variations of Bachmann's bundle. In some cases, the bundle is separated from the atrial wall by epicardial fat, and in some cases it hugs the surface of the atria. In this last instance the bundle is more susceptible to damage by internal ablation in the left atrial wall. The location of the bundle can also vary.

Bachmann’s bundle shows some bifurcations, helping to distribute the depolarization to the left atrium. The image, from Testut & Latarjet (1931), shows one of these bifurcations (yellow arrows). The bundle splits around the base of the left atrial appendage (LAA).

Historically, all pacemakers terminal wires have been implanted in the right atrium. but the potential dysfunction of Bachmann's bundle would require biatrial pacing, which is not used today.

Sources and references
1. Bachmann G. “The inter-auricular time interval”. Am J Physiol. 1916;41:309–320.
2. Hurst JW. “Profiles in Cardiology: Jean George Bachmann (1877–1959)”. Clin Cardiol. 1987;10:185–187.
3. Lemery R, Guiraudon G, Veinot JP. “Anatomic description of Bachmann’s bundle and its relation to the atrial septum”. Am J Cardiol. 2003;91:148–152.
4. Antonio Bayés de Luna, Albert Massó-van Roessel, Luis Alberto Escobar Robledo, The Diagnosis and Clinical Implications of Interatrial Block, European Cardiology Review 2015;10(1):54–9
5. Knol WG, de Vos CB, Crijns HJGM, et al. “The Bachmann bundle and interatrial conduction” Heart Rhythm. 2019;16:127–133.
6. “Iatrogenic biatrial flutter. The role of the Bachmann’s bundle” Constán E.; García F., Linde, A.. Complejo Hospitalario de Jaén, Jaén. Spain
7. "Tratado de Anatomia Humana" Testut et Latarjet 8th Ed. 1931 Salvat Editores, Spain
8. 4. Rigamonti F, Shah DC. "Bachmann Bundle Block Occurring During Radiofrequency Ablation at the Inter-Atrial Septum" J Clin Med. 2012;15(9):263.
9. Zhang Y, Wu F, Gao Y, Wu N, Yang G, Li M, Zhou L, Xu D, Chen M. "Bachmann bundle impairment following linear ablation of left anterior wall: impact on left atrial function". Int J Cardiovasc Imaging. 2022 Jan;38(1):41-50
10. Platonov, PG; Mitrofanova, L, et al.Substrates for intra-atrial and interatrial conduction in the atrial septum: Anatomical study on 84 human hearts Heart Rhythm,(2008)5:8,1189-1195.

Bachmann's bundle

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