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Archivos de cardiología de México

On-line version ISSN 1665-1731Print version ISSN 1405-9940

Arch. Cardiol. Méx. vol.91 n.2 Ciudad de México Apr./Jun. 2021  Epub May 14, 2021 

Imágenes en cardiología

Unexpected location of pacemaker electrode: Is it right?

Ubicación inesperada del electrodo marcapasos: ¿es correcto?

Juan F. Vasquez-Rodriguez1  * 

Ramón Medina-Mur1 

Lukas Salazar1 

Daniel Isaza1  2 

Claudia P. Jaimes1  3 

1Department of Cardiology

2Coronary Critical Care Unit, Division of Cardiology

3Department of Cardiovascular Imaging, Division of Cardiology, Fundación Cardioinfantil – Instituto de Cardiología, Bogotá D.C, Colombia

A 74-year-old woman presented with weakness, dizziness, dyspnea, and chest pain. A 2nd degree atrioventricular block was found. Transvenous temporary pacemaker (TTP) was implanted. Post-TTP implantation electrocardiography (ECG) showed a paced rhythm with a right branch block (RBBB) morphology, inconsistent with the right ventricular stimulation – as expected for this type of device. Chest X-ray showed the lead entering the right atrium through the superior vena cava, but the tip directed toward the left ventricular apex (Fig. 1). ECG pattern and location on chest X-ray suggested a left ventricle (LV) location of the electrode.

Figure 1 A: ECG: paced rhythm with a right branch block morphology. B: chest X-ray: lead in the right atrium with its tip directed toward the left ventricular apex (red arrow). 

Transthoracic echocardiogram (TTE) documented a patent foramen ovale (PFO). The TTP lead crossed the PFO into the left atrium, and its distal segment formed a loop in the LV apex (Fig. 2).

Figure 2 A: apical 2 chamber view: TTP lead forming a loop in the left ventricle apex (yellow arrow). B: subcostal 4 chamber view: TTP lead crossing through a PFO (red arrow). C: subcostal 4 chamber view: color Doppler at the interatrial septum (blue arrowhead). D: parasternal long-axis view: TTP lead in the left ventricle (red arrow). LA: left atria, LV: left ventricle, RA: right atria, RV: right ventricle. 

TTP insertion is usually performed using ultrasound-guided venous punctures, but with blind electrode positioning. This procedure is considered safe and few complications are seen like as non-pericardial bleeding (2.4%), cardiac tamponade (0.6%), and iatrogenic pneumothorax (2.4%)1. Unnoticed stimulation of LV after a venous puncture is infrequent. The available data highlight the fortuitous passage of the lead through interatrial septum defects as a possible cause. Other possibilities include left ventricular location due to interventricular septum (IVS) perforation; RV apical location with depolarization vector going from left to right, in dilated cardiomyopathy, secondary to left displacement of the IVS and RV; and epicardial stimulation due to RV free wall perforation or by accessing LV coronary venous tributaries through the coronary sinus with presence of QS in D1 and aVL. The left location of these devices is a potential cause of embolism2.

A pacemaker stimulation with RBBB morphology after TTP insertion could help to predict the electrode location. Complementary studies such as chest X-ray, TTE, and fluoroscopy are useful to confirm the correct positioning of the electrode. The latter being less accessible to the patient’s bedside, but allowing the correct lead placement.


1. Metkus TS, Schulman SP, Marine JE, Eid SM. Complications and outcomes of temporary transvenous pacing:an analysis of >360,000 patients from the national inpatient sample. Chest. 2019;155:749-57. [ Links ]

2. Gelder BM, Bracke FA, Oto A, Yildirir A, Haas PC, Seger JJ, et al. Diagnosis and management of inadvertently placed pacing and ICD leads in the left ventricle:a multicenter experience and review of the literature. Pacing Clin Electrophysiol. 2000;23:877-83. [ Links ]

FundingThis research did not receive any specific grant from funding agencies in the public, commercial, or not-for-profit sectors.

Ethical disclosures

Protection of human and animal subjects. The authors declare that no experiments were performed on humans or animals for this study.

Confidentiality of data. The authors declare that they have followed the protocols of their work center on the publication of patient data.

Right to privacy and informed consent. The authors declare that no patient data appear in this article.

Received: April 11, 2020; Accepted: June 18, 2020

* Correspondence: Juan F. Vasquez-Rodriguez E-mail:

Conflicts of interest


Creative Commons License Instituto Nacional de Cardiología Ignacio Chávez. Published by Permanyer. This is an open ccess article under the CC BY-NC-ND license