Radiography of Cardiac Conduction Devices: A Pictorial Review of Pacemakers and Implantable Cardioverter Defibrillators

Stephanie C Torres-Ayala; Guido Santacana-Laffitte; José Maldonado

doi:10.4103/2156-7514.148269

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PICTORIAL ESSAY

2014

:4;

doi:

10.4103/2156-7514.148269

Radiography of Cardiac Conduction Devices: A Pictorial Review of Pacemakers and Implantable Cardioverter Defibrillators

Stephanie C Torres-Ayala, Guido Santacana-Laffitte, José Maldonado

Department of Diagnostic Radiology, School of Medicine, University of Puerto Rico, Puerto Rico, United States

Address for correspondence: MS. Stephanie C Torres-Ayala, Department of Diagnostic Radiology, School of Medicine, University of Puerto Rico, HC 05 BOX 50873, Mayaguez - 00680, Puerto Rico, United States. E-mail: Stephanie.torres19@upr.edu

Received: 2014-09-10, Accepted: 2014-11-22, Published: 2014-12

Licence

This is an open-access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.

Disclaimer:
This article was originally published by Medknow Publications & Media Pvt Ltd and was migrated to Scientific Scholar after the change of Publisher.

Abstract

Cardiac conduction devices (CCDs) depend on correct anatomic positioning to function properly. Chest radiography is the preferred imaging modality to evaluate CCD's anatomic location, lead wire integrity, and help in identifying several complications. In this pictorial review, our goal is to familiarize radiologists with CCD implantation techniques, appropriate positioning of the device, common causes of malfunction, methods to improve report accuracy, and assure maximal therapeutic benefit.

Keywords

Cardiac conduction device

implantable cardioverter defibrillator

pacemaker

radiography

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INTRODUCTION

Cardiac conduction devices (CCDs) were created in the 1950s to prevent asystole. The Swedish implanted the first permanent pacemaker, increasing the average life expectancy to over 40 years.[1] By 2002, 3 million people worldwide had pacemakers. Each year 600,000 devices are implanted.[2] Numbers continue to increase, with 1 million people in the United States with a permanent CCD in the year 2011.[3]

CCDs have three main parts: A pulse generator, an electrode, and lead wires. The electrode line is proximally introduced into the generator via a terminal connector pin, which should be engaged. The distal end of the electrode is composed of lead wires with different tips for attachment to the heart [Figure 1]. Helical lead tips are screwed onto the myocardium, this is known as active fixation. The tips can have other shapes that anchor onto heart trabeculae by development of fibrosis, this is known as passive fixation.[4]

Chest radiography is used for evaluation of lead location and integrity after device implantation and for diagnosis of complications and malfunction. At least two well-penetrated chest radiographic views are required for thorough examination.[3] A posterio-anterior (PA) radiograph provides a two-dimensional view for physical integrity evaluation of the lead. To evaluate lead tip location, both PA and lateral (LAT) chest views are necessary. PA views provide a presumed lead location; therefore, a misplaced lead cannot be ruled out without a LAT view, which provides a third chest dimension.[5] LAT views, important for ventricular lead evaluation, allow distinction to be made between an anteriorly coursed right ventricle (RV) lead and a posteriorly coursed left ventricle lead.[3] It is important to be familiar with conventional chest PA and LAT radiographic cardiac anatomy [Figure 2] to distinguish correct lead locations.

PLACEMENT TECHNIQUES

Different anatomical approaches and techniques are used for CCD implantation. The percutaneous transvenous technique is used almost exclusively as the first-line intracardiac approach for lead placement. Fluoroscopically guided leads are inserted via the subclavian vein (preferred), cephalic, or jugular vein for RV or atrial access. The generator is placed in a subcutaneous pocket in the left infraclavicular fossa, right infraclavicular fossa, axilla, submammary, or under the pectoralis major muscle.[6] A video-assisted thoracoscopy is an alternative approach for cases where endocardial lead placement is not possible. Currently, sternotomy for direct placement of leads on the epicardium is rarely necessary.

TYPES OF CARDIAC CONDUCTION DEVICES

Pacemaker

The sinoatrial (SA) node, located at the junction of the superior vena cava and the right atrium, is the heart's natural pacemaker which generates electrical impulses to stimulate myocardial contraction. When disrupted by myocardial infarction or disease, cardiac electrical activity is altered causing dysrhythmia or bradycardia. An artificial pacemaker is then programmed and implanted to provide electrical impulses and maintain a stable heart rate and cardiac output.

Pacemakers vary according to lead amount, paced heart chambers, and placement approach. The simplest, a single-chamber pacemaker, contains one lead. Through the transvenous approach, the lead can pace the right atrium in patients with sinus node disease or the RV in patients with atrial fibrillation with slow ventricular response.[6] In right atrial pacing, PA chest radiograph shows an inferiorly directed lead into the right atrium, which then curves anteriorly, known as the “J loop,” with the tip at the right atrial appendage. When pacing the RV, the lead is directed inferiorly through the right atrium, curves through the tricuspid valve, and ends in an anterior–inferior position at the RV apex, and is seen left of the spine on PA X-ray. The LAT view showing an anteriorly oriented lead confirms the lead tip is in the RV. Note that in some cases, the right ventricular outflow tract (RVOT) may be used as an alternate site for pacing if the RV apex is not electrophysiologically suitable. Dual-chamber pacemakers contain two lead wires allowing pacing of the right atrium and RV simultaneously [Figure 3]. These CCDs are used to coordinate electrical signals and contraction between the atrium and ventricle in heart block patients.[3] RV leads are commonly misplaced when the lead takes a “snake-like” course and goes through the coronary sinus, ending in a posterior or lateral epicardial vein instead of the RV apex [Figure 4]. Misplacement of either lead can cause device malfunction and recurrence of symptom [Figures 5 and 6]. Radiography can demonstrate the inadvertent placement of leads in unintended sites, including: (1) Through a patent foramen ovale or atrial septal defect and then coursing through the mitral valve into the left ventricle; (2) leads that inadvertently puncture the subclavian artery and then course through the aortic valve into the left ventricle; (3) leads that go through a ventricular septal defect or perforate the interventricular septum; or (4) leads that go beyond the heart by perforating the cardiac chamber walls [Figure 7]. All of the above have distinct radiological features.

Biventricular pacemakers, also called cardiac resynchronization therapy (CRT) devices, treat refractory heart failure associated with ventricular dyssynchrony.[3] These devices have one lead pacing each ventricle; some have a right atrial lead. In the transvenous approach, the left ventricular lead enters the right atrium through the coronary sinus orifice, taking an endovenous “snake-like” course until the tip reaches a left ventricular wall epicardial vein [Figure 8]. This is confirmed using a lateral view showing a posteriorly oriented lead. Biventricular pacing can also be achieved using epicardial leads placed through a thoracotomy [Figure 9]. Even though more invasive, epicardial pacing is used in pediatric populations due to small heart size or congenital anatomical defects restricting access to the desired area.[6] It is also an alternative for patients with aberrant cardiovascular anatomy or unsuitable transvenous access.

In efforts to eliminate pacemaker wires, leadless cardiac pacemakers (LCPs) were recently introduced. LCPs are similar to an AAA battery in size and shape. Device implantation involves a minimally invasive procedure where the device is delivered via a steerable catheter through the femoral vein into the RV where it is attached.[7] As of the date of completion of this manuscript, LCPs have not yet received US Food and Drug Administration (FDA) approval.

Implantable cardioverter defibrillator

Implantable cardioverter defibrillator (ICD) is an electronic device with a defibrillator unit capable of generating and delivering an electrical impulse and shock to abort dysrhythmias and return the heart to sinus rhythm. ICDs can be either transvenous (T-ICD) or subcutaneous (S-ICD). T-ICDs contain a lead with either one or two metal shock coils placed at the brachiocephalic vein/superior vena cava junction and the RV [Figures 10–12]. T-ICDs are often combined with biventricular pacemakers to provide CRT to high-risk heart failure patients [Figure 13].[3] Combined biventricular devices have three leads; pacemaker leads are placed in the right atrial appendage and left ventricle and the ICD lead in the RV. T-ICDs can also be combined with single-lead pacemakers or epicardial leads [Figures 14–16]. An S-ICD is a novel technology that does not require transvenous lead insertion for defibrillation. Instead, a pulse generator placed at the left lateral chest delivers a transthoracic shock via a left parasternal subcutaneous lead containing sensing electrodes and shock coils [Figure 17]. These devices can be implanted in patients requiring an ICD as long as pacing for tachycardia or bradycardia is not required.[8]

MALFUNCTIONING CCD

CCD may malfunction due to physical damage to the lead such as kinked, pinched, or fractured leads [Figures 18–20]. A kinked lead results from bending of the lead during implantation, causing impaired conduction. Conduction is also impaired when leads are pinched by anatomical structures, commonly seen in subclavian crush syndrome where the wire is hindered proximal to the generator before it enters the vein through the clavicle.[4] Subclavian crush can also cause lead fracture: Incomplete fracture, seen as lead thinning, or complete fracture, seen as lead discontinuation with distal wire migration.[4] To be able to detect subtle damages, radiologists must cautiously evaluate the radiograph and follow the leads from the generator origin to the tip on the heart.

Malfunctioning CCD can also occur due to patient device manipulation. Twiddler syndrome occurs when patients rotate the CCD generator and reel the wire [Figure 21]. Leads dislodge from their position and end around the generator, eliminating therapeutic benefit of the CCD. Twitching of the arm or diaphragm can occur if electrodes contact the brachial plexus or phrenic nerve. More serious complications including ventricular perforation can also occur as the leads are pulled back.

RADIOLOGIST CHECKLIST

In order to assure a thorough evaluation and complete report, when interpreting chest radiographs containing CCDs, radiologists should go through the following checklist and make sure all points are addressed:

Device type (pacemaker, T-ICD/cardiac resynchronization therapy device, S-ICD, LCP)
Connector pin insertion
Number and position of leads
Lead integrity (fractured/kinked/pinched lead)
Complications (e.g. lead dislodgement, pneumothorax, heart chamber perforation).

CONCLUSION

In conclusion, it is crucial for radiologists to be familiar with the radiographic appearance of different types of CCD and correct lead locations to be able to detect complications and abnormal lead position because suboptimal cardiac electrical therapy can be life threatening for the patient.

ACKNOWLEDGMENT

The authors would like to thank Dr. Juan C. Sotomonte (Centro Cardiovascular de Puerto Rico, Ave. Americo Miranda, Esq Centro Medico 1, suite 10, San Juan, PR 00936) for his valuable collaboration.

Available FREE in open access from: http://www.clinicalimagingscience.org/text.asp?2014/4/1/74/148269

Source of Support: Nil

Conflict of Interest: None declared.

REFERENCES

Sutton R, Fisher JD, Linde C, Benditt DG, . History of electrical therapy for the heart. Eur Heart J Suppl. 2007;9(Suppl I):I3-10.
[Google Scholar]
Wood M, Ellengogen K, . Cardiology patient pages. Cardiac pacemakers from the patient's perspective. Circulation. 2012;105:2136-8.
[Google Scholar]
Aguilera AL, Volokhina YV, Fisher KL, . Radiography of cardiac conduction devices: A comprehensive review. Radiographics. 2011;31:1669-82.
[Google Scholar]
Costelloe CM, Murphy WA Jr, Gladish GW, Rozner MA, . Radiography of pacemakers and implantable cardioverter defibrillators. AJR Am J Roentgenol. 2012;199:1252-8.
[Google Scholar]
Sonnex E, Coulden R, . Cardiac pacemaker lead placement: Do you need a lateral chest radiograph? Radiography. 2010;16:248-52.
[Google Scholar]
Burney K, Burchard F, Papouchado M, Wilde P, . Cardiac pacing systems and implantable cardiac defibrillators (ICDs): A radiological perspective of equipment, anatomy and complications. Clin Radiol. 2004;59:699-708.
[Google Scholar]
Reddy VY, Knops RE, Sperzel J, Miller MA, Petru J, Simon J, . Permanent leadless cardiac pacing: Results of the LEADLESS trial. Circulation. 2014;129:1466-71.
[Google Scholar]
Hauser RG, . The subcutaneous implantable cardioverter-defibrillator: Should patients want one? J Am Coll Cardiol. 2013;61:20-2.
[Google Scholar]