Leadless pacemaker implantation and azygos continuation in the inferior vena cava: a case description

Xinhong Wang, Xinfa Ding, Mengxi Xu, Cong Chen, Linlin Ma, Rui Wang, Rongliang Chen, Haipeng Liu

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Azygos continuation (AC) of the inferior vena cava (IVC), also known as the absence of the hepatic segment of the IVC with AC, is a rare anatomic variant in the general population with an incidence of 0.6% (1). AC of the IVC is congenital and independent from other anatomical variants. It is primarily caused by the absence or hypoplasia of the IVC’s hepatic segment. The IVC below the hepatic segments flows upward through the azygos into the superior vena cava (SVC) and eventually drains into the right atrium. The renal portion of the IVC receives blood flow from the kidneys and lower extremities and drains into the SVC through the azygos vein. The azygos vein, azygos arch, and SVC dilate to accommodate the increase in blood flow (2). Usually, AC in the IVC is asymptomatic and does not affect the functionality of the cardiovascular system. However, it significantly impacts leadless pacemaker (LP) implantation via the femoral vein. The LP is a feasible alternative to the single-ventricle pacemaker; that is, a pacemaker that simply paces the ventricle but not the atrium. LP is a novel technique that differs from traditional pacemakers in terms of the electronic components, implantation procedure, possible complications, and postoperative management. Unlike the conventional pacemaker implantation, where the lead is delivered to the heart by puncturing the subclavian veins to approach the SVC, the LP implantation involves puncturing the femoral vein and delivering the LP to the heart via the IVC (3). If a patient has AC of the IVC, an LP cannot be implanted through the IVC pathway or could be delivered to the wrong location, such as the SVC. Furthermore, routine preoperative examinations (e.g., cardiac ultrasound and chest X-ray) are ineffective in detecting AC. Herein, we report a case of AC of the IVC observed during LP implantation, which resulted in the abandonment of this procedure. Electrocardiogram (ECG)- gated computed tomography (CT) venography was used to identify the anatomic variant of the IVC as an AC. This patient eventually underwent conventional pacemaker implantation via the SVC.
Original languageEnglish
Pages (from-to)2751-2757
Number of pages7
JournalQuantitative Imaging in Medicine and Surgery
Issue number4
Early online date3 Mar 2023
Publication statusPublished - 1 Apr 2023

Bibliographical note

This is an Open Access article distributed in accordance with the Creative Commons Attribution-NonCommercial-NoDerivs 4.0 International License (CC BY-NC-ND 4.0), which permits the non-commercial replication and distribution of the article with the strict proviso that no changes or edits are made and the original work is properly cited (including links to both the formal publication through the relevant DOI and the license). See: https://creativecommons.org/licenses/by-nc-nd/4.0/.


This study was supported by the National Key
Research and Development Program of China (No. 2018YFE0198400) and the National Natural Science Foundation of China (No. 81702958).


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