Medical Terminology Daily - Est. 2012

Medical Terminology Daily (MTD) is a blog sponsored by Clinical Anatomy Associates, Inc. as a service to the medical community. We post anatomical, medical or surgical terms, their meaning and usage, as well as biographical notes on anatomists, surgeons, and researchers through the ages. Be warned that some of the images used depict human anatomical specimens.

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A Moment in History

Jean George Bachman

Jean George Bachmann
(1877 – 1959)

French physician–physiologist whose experimental work in the early twentieth century provided the first clear functional description of a preferential interatrial conduction pathway. This structure, eponymically named “Bachmann’s bundle”, plays a central role in normal atrial activation and in the pathophysiology of interatrial block and atrial arrhythmias.

As a young man, Bachmann served as a merchant sailor, crossing the Atlantic multiple times. He emigrated to the United States in 1902 and earned his medical degree at the top of his class from Jefferson Medical College in Philadelphia in 1907. He stayed at this Medical College as a demonstrator and physiologist. In 1910, he joined Emory University in Atlanta. Between 1917 -1918 he served as a medical officer in the US Army. He retired from Emory in 1947 and continued his private medical practice until his death in 1959.

On the personal side, Bachmann was a man of many talents: a polyglot, he was fluent in German, French, Spanish and English. He was a chef in his own right and occasionally worked as a chef in international hotels. In fact, he paid his tuition at Jefferson Medical College, working both as a chef and as a language tutor.

The intrinsic cardiac conduction system was a major focus of cardiovascular research in the late nineteenth and early twentieth centuries. The atrioventricular (AV) node was discovered and described by Sunao Tawara and Karl Albert Aschoff in 1906, and the sinoatrial node by Arthur Keith and Martin Flack in 1907.

While the connections that distribute the electrical impulse from the AV node to the ventricles were known through the works of Wilhelm His Jr, in 1893 and Jan Evangelista Purkinje in 1839, the mechanism by which electrical impulses spread between the atria remained uncertain.

In 1916 Bachmann published a paper titled “The Inter-Auricular Time Interval” in the American Journal of Physiology. Bachmann measured activation times between the right and left atria and demonstrated that interruption of a distinct anterior interatrial muscular band resulted in delayed left atrial activation. He concluded that this band constituted the principal route for rapid interatrial conduction.

Subsequent anatomical and electrophysiological studies confirmed the importance of the structure described by Bachmann, which came to bear his name. Bachmann’s bundle is now recognized as a key determinant of atrial activation patterns, and its dysfunction is associated with interatrial block, atrial fibrillation, and abnormal P-wave morphology. His work remains foundational in both basic cardiac anatomy and clinical electrophysiology.

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. "Remembering the canonical discoverers of the core components of the mammalian cardiac conduction system: Keith and Flack, Aschoff and Tawara, His, and Purkinje" Icilio Cavero and Henry Holzgrefe Advances in Physiology Education 2022 46:4, 549-579.
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. Keith A, Flack M. The form and nature of the muscular connections between the primary divisions of the vertebrate heart. J Anat Physiol 41: 172–189, 1907.


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Esophageal hiatus hernia in situ.The arrow points to stomach and greater omentum herniating into the thorax
Esophageal hiatus hernia in situ.
The arrow points to stomach and greater
omentum herniating into the thorax

UPDATED: An esophageal hiatus hernia (also known as a hiatal hernia) is caused by a dilation of the esophageal hiatus and its component structures, the phrenoesophageal membranes (ligaments).

Since the intraabdominal pressure is higher than the intrathoracic pressure, abdominal contents -usually stomach and greater omentum- can herniate through the dilated esophageal hiatus into the mediastinum, the central region of the thoracic cavity. This presents as a hernia sac whose walls are formed by endothoracic fascia, phrenoesophageal membranes and parietal peritoneum. 

There are two main types of esophageal hiatus hernias. Type I is known as a "sliding hiatal hernia" and is characterized by a complete ascension of the esophagogastric junction and abdominal esophagus into the thoracic hernia sac. This is usually accompanied by a typical "hourglass image" in a radiographic assessment, and also presents with gastroesophageal reflux disease (GERD). Type I esophageal hiatus hernias are more common.

Esophageal hiatus hernia, reduced. The dotted line shows the edge of the enlarged esophageal hiatus
Esophageal hiatus hernia, reduced.
The dotted line shows the edge of
the enlarged esophageal hiatus

Type II esophageal hiatus hernia is known as a "paraesophageal hernia" and represent about 5 - 15% of esophageal hiatus hernias. In this case, the esophagogastric junction maintains its anatomical position inferior to the respiratory diaphragm, but the fundus and body of the stomach, along with some greater omentum herniate alongside the esophagus into the mediastinal region of the thoracic cavity. Although there can be GERD, this type of hernia usually presents with little symptomatology, and when it does, symptoms are related to ischemia or partial to complete obstruction. There are variations of type II hernia, which are classified as Type III and IV. Type IV, although rare, will include other viscera in the hernia sac, including colon, spleen, or even small intestine.

The accompanying images above depict a Type I esophageal hiatus hernia. The superior image shows the hernia in situ where the stomach and greater omentum are still in the hernia sac. The inferior image shows the contents reduced and the abdominal esophagus being pulled into the abdominal cavity. The dotted line shows the dilated esophageal hiatus that needs to be repaired to prevent recurrence of the pathology.

Click on this link for additional information on esophageal hiatus hernia surgery.

The image below answers a question by Victoria Guy Ratcliffe, who asked via Facebook "What would it be if it feels like you've got a blockage right at the level of the heart? That's too high for a hiatal hernia, isn't it?" The image answers the question. It shows a dissection of the left side of the thorax. The anterior thoracic wall and the left lung have been removed. The heart is immediately superior and anterior to the esophageal hiatus, and the hernia sac of a Type I esophageal hiatus hernia is seen immediately posterior and in contact with the heart. Whether this means that you will "feel" the hernia, it is up for debate, as all these structures have visceral innervation. Most probably, a well-developed Type II esophageal hiatus hernia might interfere with swallowing at this level, causing the sensation she mentions. Thanks for the question, Tori.

Type I esophageal hiatus hernia<em>.</em>The hernia sac can be seen posterior to the heart

For additional information:
"Approaches to the Diagnosis and Grading of Hiatal Hernia" Kahrilas et al Best Pract Res Clin Gastroenterol. 2008 ; 22(4): 601–616.