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Radiographic and electrocardiography-gated noncontrast cardiac CT assessment of lead perforation: Modality comparison and interobserver agreement
J o u r n a l o f C a r d i o v a s c u l a r C o m p u t e d T o m o g r a p h y 8 ( 2 0 1 4 ) 3 8 4 e3 9 0
Available online at www.sciencedirect.com
ScienceDirect journal homepage: www.JournalofCardiovascularCT.com
Original Research Article
Radiographic and electrocardiography-gated noncontrast cardiac CT assessment of lead perforation: Modality comparison and interobserver agreement Christian Balabanoff MDa,b, Cristopher E. Gaffney MDc,d, Eduard Ghersin MDc, Yoji Okamoto MDa,e, Roger Carrillo MDa, Joel E. Fishman MD, PhDc,* a Department of Surgery, Division of Cardiothoracic Surgery, University of Miami Miller School of Medicine, Miami, FL, USA b Division of Cardiology, Abington Memorial Hospital, Abington, PA, USA c Department of Radiology, Jackson Memorial Hospital, University of Miami Miller School of Medicine, 1611 N.W., 12th Avenue, Miami, FL, USA d Department of Radiology, Texas Children’s Hospital, Baylor College of Medicine, Houston, TX, USA e Department of Medicine, Division of Cardiology, Kurashiki Central Hospital, Okayama, Japan
article info
abstract
Article history:
Background: Pacemaker or implantable cardioverter-defibrillator lead extraction may be
Received 4 August 2013
required because of infection, malfunction, or breakage. The preprocedural identification
Received in revised form
of lead tip position may help ensure safe performance of the procedure.
20 June 2014
Objective: To analyze the ability of chest radiography and CT imaging to characterize lead
Accepted 16 August 2014
tip position and identify perforation in a population of patients who underwent lead extraction. Methods: Among patients who underwent lead extraction between November 2008 and
Keywords:
April 2011, a nonrandom subset of 50 patients with 116 leads was selected for retrospective
Pacemaker
analysis. All patients had undergone chest radiography and thin-section electrocardiog-
Artificial
raphy-gated noncontrast cardiac CT. Two radiologists independently evaluated the imag-
Defibrillators
ing studies, using oblique multiplanar image reconstruction techniques for the CT
Tomography
examinations. Beam hardening artifacts were graded (0e3). Likelihood of perforation on
X-ray computed
each imaging study was graded on a 5-point scale.
Radiography
Results: Among 116 leads, 17 were identified as perforated on CT, 12 leads were equivocal,
Thoracic
and 87 were not perforated. Interobserver agreement for CT perforation vs nonperforation was good (k ¼ 0.71); weighted kappa for the entire 5-point scale was moderate (k ¼ 0.54). Beam hardening artifacts were common, with a mean value of 2.1. The 2 observers
Conflict of interest: Roger Carrillo is a consultant for Spectranetics, Medtronic, Inc., St. Jude Medical, Sorin, and Sensormatic and receives grants or research support from St. Jude Medical (NCT # 00940888), Medtronic (NCT # 00893386). The other authors declare no conflicts of interest. * Corresponding author. E-mail address: [email protected] (J.E. Fishman). 1934-5925/$ e see front matter ª 2014 Society of Cardiovascular Computed Tomography. All rights reserved. http://dx.doi.org/10.1016/j.jcct.2014.08.004
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385
identified perforation on chest radiography with an average sensitivity of 15% compared with CT. The 2 observers did not agree on any cases of chest radiographic perforation (k ¼ 0.1). Conclusion: Electrocardiography-gated noncontrast cardiac CT imaging with oblique multiplanar analysis can identify potential lead perforation with a moderate-to-good level of interobserver agreement. Chest radiography demonstrates poor sensitivity and interobserver agreement compared with CT. ª 2014 Society of Cardiovascular Computed Tomography. All rights reserved.
1.
Introduction
Approximately 67,000 defibrillators, 178,000 pacemakers, 33,000 cardiac resynchronization defibrillators, and 7000 cardiac resynchronization pacemakers were implanted in the United States in 2004.1 Subsequent device and lead extraction may be required for indications such as infection, device malfunction, and lead breakage. Lead extraction may be accomplished by mechanical or energy-assisted means such as thoracotomy, electrocautery, and lasers. In any patient with cardiac leads, early or late lead perforation may occur through the myocardium, into the epicardial space, pericardium, or chest wall. Lead perforation is often clinically occult and only infrequently accompanied by symptoms such as pain. Pre-extraction knowledge of the presence of lead perforation could significantly impact the method and techniques chosen for lead extraction. Chest radiography in 2 views may occasionally demonstrate clear evidence of perforation but is inherently limited because distinction between the ventricular cavity, myocardium, and pericardium cannot be made. Chest CT would seem to have much to recommend it for lead tip identification, and there have been numerous case reports and occasional larger series published to this end.2e6 CT images of leads, however, can be challenging to interpret for 2 main reasons: the heart and leads are in motion, and metallic materials can produce severe streak artifacts.7 Our objective was to analyze a series of chest radiographs and electrocardiography (ECG)-gated noncontrast cardiac CT scans of patients with device leads before extraction to determine the degree of confidence in identifying perforation, calculate interobserver agreement, and compare radiographic results with those of CT.
2.
Methods
This project was approved by the University of Miami institutional review board with waiver of informed consent. A cardiothoracic surgeon (R.C.) has been performing laserassisted and operative lead extraction at the University of Miami Hospital since September 2008. As part of clinical protocol, ECG-gated noncontrast cardiac CT scanning was performed before the extraction. Among all 329 patients who underwent lead extraction between November 2008 and April 2011, a nonrandom convenience subset of patients was selected for retrospective radiographic and CT analysis. To capture as many patients with potentially perforated leads as possible, the subset included all patients (n ¼ 16) who had a preprocedure suspicion of possible lead perforation based on
the radiographic and/or CT report generated at the time of the study. A larger group (n ¼ 34) of randomly selected patients whose imaging did not suggest perforation was added for a total group size of 50 nonrandom patients with 116 leads. The obtained images included single anteroposterior (n ¼ 25) or 2view (n ¼ 25) chest radiography. Chest CT was performed on a Siemens ASþ 128-slice, single-source scanner (Siemens Healthcare, Malvern, PA) using ECG gating at 120 kVP, 150 to 190 mAs, and a mixture of both prospective and retrospective technique. Prospectively gated studies were centered at 70% of the R-R interval. The “best diastolic” phase selected by the scanner was used for retrospectively gated studies, which ranged from 66% to 86% of the R-R interval. Multiphase images were isovolumetrically (0.6 0.6 mm) reconstructed with no overlap using a B26f smooth cardiac kernel and interpreted using oblique multiplanar reformat (MPR) in TeraRecon iNtuition (version 4.4.7; Foster City, CA). Heart rate was not recorded and no beta blockers were administered. Subsequently, patients underwent laser lead extraction with concurrent transesophageal ECG of a total of 106 leads. Ten leads were not extracted. Each extracted lead was transected proximally and a laser sheath was inserted over the lead, advanced in the direction of the lead tip, and activated at points of lead adhesion. Lasering was halted 1 cm from the lead tip in the myocardium unless the CT scan demonstrated lead perforation, in which case the laser sheath was halted at a prudent distance from the tip to prevent a larger perforation. One patient whose preprocedure CT demonstrated lead perforation had a left anterior minithoracotomy performed to assist in safe removal of the lead, which was directly observed extending out the right ventricular chamber. Two other patients without perforation also had thoracotomies performed for other reasons. There were 4 deaths among the 50 patients during their hospitalizations, all due to sepsis and resulting multiorgan failure in patients whose indication for lead removal was infection. There were no deaths attributable to the lead extraction procedure itself. One patient had a surgical site hematoma requiring drainage, constituting a minor complication of lead removal.
2.1.
Image analysis
Two radiologists (E.G., J.F.), who were not involved in the initial clinical interpretation of the CT scans and who were unaware of whether there was suspected lead perforation, independently and randomly evaluated the imaging studies. Using an image reconstructed in mid-diastole, orthogonal oblique MPRs were created to demonstrate the length of the lead tip in 2 orthogonal views with the third view being a
386
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cross-section of the lead. Dual-window and level Hounsfield unit (HU) settings were routinely applied. The first setting was designed for optimal demarcation of the lead tip while minimizing streak artifacts, to most closely demonstrate the architecture of the lead tip as seen on the CT scout view (Fig. 1AeC). This used a relatively wide window (w1400) with a center of approximately 300 HU, equivalent to a modified bone setting. As on nonecontrast-enhanced CT the density of the right ventricle blood pool is generally within 100 HU of epicardial fat, a higher contrast window and level setting was then applied for optimal demarcation of the interface between the right ventricular myocardium and blood pool and the epicardial fat. This was similar to a mediastinal setting, using a center around 50 HU and a narrower width of approximately 400 HU (Fig. 1D). Using these images, the presence of perforation was graded on a 5-point scale according to the following. Grade 1: tip clearly within the region of the blood pool and myocardium. Grade 2: tip abutting the blood pool and myocardiumepicardial fat interface but does not measurably cross the interface.
Grade 3: tip passes no more than 2 mm past the blood pool and myocardium-epicardial interface, 2 mm being chosen because that is the approximate length of the lead tip screw. Grade 3 was considered equivocal for perforation. Grade 4: tip crosses >2 mm and no greater than 4 mm past the blood pool and myocardium-epicardial fat interface. Grade 5: tip crosses >4 mm past the blood pool and myocardium-epicardial fat interface. After all independent readings, a consensus reading was performed when the independent readings were not either grade 1 or 2, grade 3, or grade 4 or 5. Motion artifacts were noted when sufficient to degrade interpretation of lead position (absent ¼ 0, present ¼ 1), and metallic streak artifacts were graded on a 4-point scale (from none ¼ 0 to severe ¼ 3). Chest radiographs were reviewed using a picture archiving and communication system workstation (Philips iSite, Andover, MA). A 5-point scale was used to judge lead position (1 ¼ definitely not perforated, 2 ¼ probably not perforated, 3 ¼ equivocal, 4 ¼ probably perforated, and 5 ¼ definitely perforated). Consensus interpretations were not performed in cases of disagreement.
Fig. 1 e Perforated right ventricular implantable cardioverter-defibrillator lead. (A) CT scout image demonstrating the architecture of the lead. (B, C) orthogonal multiplanar reformat images using modified bone settings redemonstrate the lead tip architecture. (D) Same image as (C) using mediastinal settings better demonstrates grade-5 perforation of the lead tip (arrow) past the pericardium (arrowheads).
J o u r n a l o f C a r d i o v a s c u l a r C o m p u t e d T o m o g r a p h y 8 ( 2 0 1 4 ) 3 8 4 e3 9 0
2.2.
Statistical analysis
Continuous and categorical variables were analyzed using SAS, version 9.1 (SAS Institute Inc., Cary, NC). Continuous variables are analyzed as mean standard deviation. Categorical variables are analyzed as numbers or percentages. The Fisher exact test was used for 2 2 contingency tables. P values <.05 were considered statistically significant. Interobserver agreement was calculated using MedCalc, version 12.5.0 (MedCalc Software, Ostend, Belgium).
3.
Results
Table 1 e Subject and lead characteristics. Characteristic
time for all leads studied was 4.8 4.8 years; of these, the mean implantation time of all the leads that were perforated was 2.6 3.1 years. The perforated leads included 8 pacemaker leads and 9 ICD leads. The mean implantation times for perforated leads were 3.5 3.7 years (pacemaker) and 1.9 2.1 years (ICD), respectively. All perforations were through the right ventricular wall. Intraprocedural transesophageal ECG demonstrated 1 pericardial effusion in a patient with a perforated lead. The echocardiograms were performed for monitoring purposes rather than perforation detection without attention to leads, and no perforations were thereby visualized.
3.1.
Clinical data regarding the patients and leads are listed in Table 1. The patients included 32 men (64%) and 18 women (36%), with an age of 67.8 17.6 years. The ejection fraction was 35.0 13.8% and the average New York Heart Association class was 2.7 0.8. Significant comorbidities included coronary artery disease in 29 patients (58%), diabetes mellitus in 17 (34%), and hypertension in 40 (80%). Fourteen patients (28%) had previous heart surgery. The patient indications for lead extraction were infection (29 patients) and malfunction (21 patients). Within our nonrandomly selected group, leads excised for infection were less likely to be perforated than not perforated, whereas leads excised for malfunction were more likely to be perforated than not perforated (both P < .001). There were 116 leads studied with 2.0 0.9 leads per patient. There were 78 pacemaker leads, 35 implantable cardioverterdefibrillator (ICD) leads, and 3 epicardial leads. Within our nonrandomly selected group, ICD leads were more likely to be perforated than pacer leads (P ¼ .046). The mean implantation
Perforated Nonperforated (n ¼ 17) (n ¼ 33)
Age (y), mean SD 70.1 16.1 Gender Male 12 Female 5 31.3 8.9 BMI (kg/m2), mean SD Ejection fraction (%), 34.7 13.7 mean SD NYHA class, 2.7 0.8 mean SD Hemodialysis 1 CAD 9 DM 3 HTN 14 Indication Infection 4 Malfunction 13 Lead type ICD 9 Pacer 8 Epicardial 0
P value
66.8 18.6
NS
20 13 28.2 6.1
NS NS NS
35.1 13.7
NS
2.7 0.8
NS
3 20 14 26
NS NS NS NS
25 8
<.001 <.001
26 70 3
.046 vs pacer ()
BMI, body mass index; CAD, coronary artery disease; DM, diabetes mellitus; HTN, hypertension; ICD, implantable cardioverterdefibrillator; NS, not significant; SD, standard deviation.
387
Chest CT results
Among 116 leads, 17 were identified as perforated on MPR CT, 12 leads were graded as equivocal (grade 3), and 87 were considered not perforated (Figs. 1, 2). For interobserver agreement of all MPR CT readings, weighted kappa for the 5-point scale was moderate (k ¼ 0.54). After consolidating results into 2 categories (not perforated, grades 1e3, vs perforated, grades 4e5), interobserver agreement for CT perforation vs nonperforation was good (k ¼ 0.71). Of 17 leads judged to be perforated, in 7 cases both readers indicated grade 5; in 5 cases 1 reader indicated 5 and the other, 4; in 2 cases both indicated 4; and in 3 cases there was a disagreement regarding the presence of perforation, which in consensus was determined to be grade 4. There were 16 leads suspected of perforation based on initial CT scan results (which did not use oblique MPR analysis). Of these, 12 were perforated and 4 not perforated according to MPR CT. There were 5 cases judged to be perforated by oblique MPR analysis that were not suspected of perforation based on the clinical CT reading; 3 of these were the consensus cases assigned grade 4, and the other 2 were grade 4 and grade 4 or 5. Sensitivity and specificity of clinical CT assessment vs MPR CT readings were 71% and 96%, respectively; positive and negative predictive values were 75% and 95%, respectively. Leads were graded on both metallic streak artifact and motion artifact. Using a 4-point scale (maximum grade 3), metallic artifact among all leads was 2.1 0.7. In the 9 cases in which there was a disagreement about perforation, the value was slightly higher (2.3 0.7) but not significantly different. Motion artifact (0 ¼ no, 1 ¼ yes) was 0.3 0.4 for both all leads and for the 9 cases of disagreement (Fig. 3).
3.2.
Chest radiographic results
Observer 1 judged 6 leads to be probably or definitely perforated, of which 3 were judged perforated by MPR CT, yielding a sensitivity of 18% and a specificity of 97%. Observer 2 judged 6 leads to be probably or definitely perforated, of which 2 were judged perforated by MPR CT, yielding a sensitivity of 12% and a specificity of 96%. Of the 7 cases where both readers independently judged a definite perforation (grade 5) on MPR CT, 1 observer identified 1 perforation on chest radiography. The 2 observers did not agree on any cases of perforation on chest radiography. For interobserver agreement of all radiographic readings, weighted kappa for the 5-point scale was poor (k ¼ 0.12). After consolidating results to 2 categories (not
388
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Fig. 2 e Dual right ventricular leads. (A) CT scout view shows both a right ventricular pacemaker lead and an ICD (implantable cardioverter-defibrillator) lead (more caudal in location). (B) Multiplanar reformat CT image using modified bone display setting shows the architecture of the leads. (C) Image (B) using mediastinal display setting shows grade-4 perforation of the pacemaker lead more than 2 mm past the blood pool and myocardium-epicardial interface (arrow shows junction of lead and interface). The inferiorly positioned ICD lead abuts but does not pass the interface.
perforated vs perforated), interobserver agreement for perforation vs nonperforation on chest radiographs was worse than random chance (k ¼ 0.1).
4.
Discussion
Pacemakers and ICD devices are being implanted in ever increasing numbers of patients and a small proportion are requiring subsequent lead removal for a variety of indications. Despite the proliferation of such devices and the increasing utilization of CT scanning of the heart and chest, there has been relatively little published regarding the use of CT to accurately identify lead tip position or perforation. Most of the published literature on this topic has consisted of case reports of perforated leads. Reefat et al8 described 2 cases of late lead perforation (defined as the perforation of the lead through the myocardium >1 month after implantation), and summarized the literature concerning 51 other such cases. They concluded that CT may be a useful imaging modality but imply that there are limitations in sensitivity and specificity because of metallic streak artifacts. In part because of these limitations, they suggest that the meaning of detecting a “near perforation” in an asymptomatic patient is unclear, indicating follow-up. In another report of 3 cases of perforation, 2 patients underwent
“cardiac CT,” presumably meaning ECG gated, and both axial and coronal images were used to demonstrate the findings.3 However, the authors did not provide a rationale for using gating nor did they use an oblique multiplanar analysis method to optimally visualize the lead tip. Standard (ie, noneECG gated) CT and straight reconstruction planes were also used in the largest series of lead CT scanning published to date.9 Rather than patients with suspected perforation or other lead-related problems, that study reviewed a consecutive series of 100 patients with leads who were scanned for other reasons. The authors diagnosed lead perforation in 15% of the atrial leads and 6% of the ventricular ones. A relative shortcoming of their study is the variety of slice thicknesses used (up to 5 mm). Leads are commonly <5 mm in diameter; optimally, CT slice thicknesses should be less than half of the size of the object being imaged. In addition, diagnostic-quality MPR images require slice thicknesses of 2 mm or less. Furthermore, they identified the lead tip as the center of the star artifact rather than from optimal visualization of the lead structure. These factors may help account for the significant difference in identification of atrial lead perforations, of which we did not encounter any in our study. Our study is the first of which we are aware that assesses the performance of CT and chest radiography in a large series of patients requiring lead removal. Our motivation was to
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Fig. 3 e Motion artifact. (A) CT scout view demonstrating right atrial and ventricular pacemaker leads. (B) Coronal CT image demonstrating the right ventricular lead (arrow) and an artifactual “second” lead more cephalad in location. (C, D) Magnified mediastinal display setting multiplanar reformat images show perforation of the lead into the pericardium (arrowheads).
potentially improve the safe performance of lead extraction. Laser lead extraction involves the advancement of a laser sheath over the lead to disrupt fibrous bands and facilitate extraction. Should a lead be perforated and the sheath advanced too close to the tip, the potential exists to enlarge the perforation orifice. The procedural instructions advise advancing the sheath no closer than 1 cm from the tip, but this is a recommendation only, and if the lead is perforated by >1 cm then complications may ensue. At our center, the performance of laser lead removal is a safe procedure with a combined major and minor complication rate of 6.3%; the extent to which our preprocedural CT scanning has benefited safety is unknown. In our study, ECG-gated cardiac CT demonstrated good interobserver agreement for the identification of perforation. In most cases, we were able to use MPR reconstructions to achieve an image demonstrating the known lead tip configuration, increasing confidence in the assessment of tip position. There are, however, several challenges to the precise identification of the lead tip, mainly due to metallic streak artifacts. There are several research methods described for the generation of images with fewer metallic artifacts which may eventually be relevant to this application of CT.10,11 Despite using cardiac gating, motion artifacts were
nevertheless identified in approximately 30% of the imaged leads. Heart rate was not recorded during this study; therefore, we do not know the extent to which tachycardia or irregular rhythms were present and thus the extent to which b-blocker administration might have reduced motion artifacts. All the consensus grade-5 perforations were detected on the clinical review of the CT scan (ie, without oblique MPR analysis). Our use of MPR image reconstruction identified 5 potential perforations not detected clinically or by routine reading of the preprocedure CT scans, but 4 of those 5 perforations were grade 4 (ie, <4 mm past the myocardium and not into the pericardium). The clinical relevance of identifying perforation into the epicardial fat (in contrast to perforation of the pericardium) is unknown, as is the most appropriate management. Presuming that a “minor” perforation may eventually progress to a “major” perforation by continued pulsatile motion of the screw-tipped lead, follow-up imaging would appear to be appropriate. Our study showed that chest radiography is not a reliable method for evaluating lead perforation, demonstrating both very poor sensitivity and interobserver agreement compared with CT scanning. There are nevertheless valid clinical reasons for obtaining a chest radiograph in patients suspected
390
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of problems with device leads, such as inappropriate positioning (eg, atrial lead not engaged superiorly into the right atrial appendage), evidence of infection (eg, septic emboli), or sequela of perforation (eg, pleural or pericardial effusions). Limitations of our study include the use of a nonrandom subset of all patients who underwent ECG-gated noncontrast cardiac CT for the evidence of lead perforation. There was no definitive gold standard for the presence of lead perforation such as direct assessment via thoracotomy or thoracoscopy. Only 1 of the 17 perforated leads detected on CT was directly visualized at thoracotomy. We did not observe a high rate of complications of lead removal despite the presence of 17 perforated leads; the extent to which preprocedural suspicion of 12 of those perforations (including all the grade 5 perforations) may have improved procedural outcomes is unknown. Our population was not consecutive so we are unable to comment on overall perforation rates in patients referred for lead removal. We did not have access to methods of reducing metal artifact on the CT images nor did we use a “sharp” reconstruction kernel. Our retrospective study design resulted in a combination of retrospectively and prospectively ECGgated exams. However, only a single “best diastolic” phase was routinely archived to picture archiving and communication system for the retrospective studies. We are unable to compare the relative merits of those 2 acquisition methods for lead evaluation, specifically whether motion artifact might be reduced if a phase other than “best diastolic” were analyzed. We cannot determine the radiation dose for our patients because the values were not archived consistently during the period of time from which patients were selected. Dose is substantially lower with prospective than retrospective gating and would be preferable assuming that image quality is equivalent. We did not incorporate measurements of intrarater reliability into our project design. Regarding chest radiography, we did not have 2-view radiographs in half of the patients.
5.
Conclusion
ECG-gated noncontrast cardiac CT with oblique MPR and dualwindow analysis demonstrates good interobserver agreement for the identification of lead perforation. Future improvements in image generation and processing might reduce metallic streak artifacts and allow improved confidence in lead tip position assessment. Chest radiography is not an accurate method for identifying lead perforation.
Acknowledgments The authors thank Noam Alperin, PhD, and Ahmet M Bagci, PhD, Advanced Image Processing Laboratory, Department of Radiology, University of Miami Miller School of Medicine, for calculations of kappa statistics.
references
1. Zhan C, Baine WB, Sedrakyan A, Steiner C. Cardiac device implantation in the United States from 1997 through 2004: a population-based analysis. J Gen Intern Med. 2008;23(Suppl 1):13e19. 2. Sussman SK, Chiles C, Cooper C, Lowe JE. CT demonstration of myocardial perforation by a pacemaker lead. J Comput Assist Tomogr. 1986;10(4):670e672. 3. Henrikson CA, Leng CT, Yuh DD, Brinker JA. Computed tomography to assess possible cardiac lead perforation. Pacing Clin Electrophysiol. 2006;29:509e511. 4. Merla R, Reddy NK, Kunapuli S, Schwarz E, Vitarelli A, Rosanio S. Late right ventricular perforation and hemothorax after transvenous defibrillator lead implantation. Am J Med Sci. 2007;334(3):209e211. 5. Schroeter T, Doll N, Borger MA, Groesdonk HV, Merk DR, Mohr FW. Late perforation of a right ventricular pacing lead: a potentially dangerous complication. Thorac Cardiovasc Surg. 2009;57(3):176e177. 6. Yoshimori A, Kobori A, Michihiro N, Furukawa Y. Delayed perforation of the right ventricular wall by a single standardcaliber implantable cardioverter-defibrillator lead detected by multidetector computed tomography. Korean Circ J. 2011;41:689e691. 7. Barrett JF, Keat N. Artifacts in CT: recognition and avoidance. Radiographics. 2004;24(6):1679e1691. 8. Refaat MM, Hashash JG, Shalaby AA. Late perforation by cardiac implantable electronic device leads: clinical presentation, diagnostic clues, and management. Clin Cardiol. 2010;33(8):466e475. 9. Hirschl DA, Jain VR, Spindola-Franco H, Gross JN, Haramati LB. Prevalence and characterization of asymptomatic pacemaker and ICD lead perforation on CT. Pacing Clin Electrophysiol. 2007;30:28e32. 10. Boas FE, Fleischmann D. Evaluation of two iterative techniques for reducing metal artifacts in computed tomography. Radiology. 2011;259(3):894e902. 11. Bamberg F, Dierks A, Nikolaou K, Reiser MF, Becker CR, Johnson TR. Metal artifact reduction by dual energy computed tomography using monoenergetic extrapolation. Eur Radiol. 2011;21(7):1424e1429.
Available online at www.sciencedirect.com
ScienceDirect journal homepage: www.JournalofCardiovascularCT.com
Original Research Article
Radiographic and electrocardiography-gated noncontrast cardiac CT assessment of lead perforation: Modality comparison and interobserver agreement Christian Balabanoff MDa,b, Cristopher E. Gaffney MDc,d, Eduard Ghersin MDc, Yoji Okamoto MDa,e, Roger Carrillo MDa, Joel E. Fishman MD, PhDc,* a Department of Surgery, Division of Cardiothoracic Surgery, University of Miami Miller School of Medicine, Miami, FL, USA b Division of Cardiology, Abington Memorial Hospital, Abington, PA, USA c Department of Radiology, Jackson Memorial Hospital, University of Miami Miller School of Medicine, 1611 N.W., 12th Avenue, Miami, FL, USA d Department of Radiology, Texas Children’s Hospital, Baylor College of Medicine, Houston, TX, USA e Department of Medicine, Division of Cardiology, Kurashiki Central Hospital, Okayama, Japan
article info
abstract
Article history:
Background: Pacemaker or implantable cardioverter-defibrillator lead extraction may be
Received 4 August 2013
required because of infection, malfunction, or breakage. The preprocedural identification
Received in revised form
of lead tip position may help ensure safe performance of the procedure.
20 June 2014
Objective: To analyze the ability of chest radiography and CT imaging to characterize lead
Accepted 16 August 2014
tip position and identify perforation in a population of patients who underwent lead extraction. Methods: Among patients who underwent lead extraction between November 2008 and
Keywords:
April 2011, a nonrandom subset of 50 patients with 116 leads was selected for retrospective
Pacemaker
analysis. All patients had undergone chest radiography and thin-section electrocardiog-
Artificial
raphy-gated noncontrast cardiac CT. Two radiologists independently evaluated the imag-
Defibrillators
ing studies, using oblique multiplanar image reconstruction techniques for the CT
Tomography
examinations. Beam hardening artifacts were graded (0e3). Likelihood of perforation on
X-ray computed
each imaging study was graded on a 5-point scale.
Radiography
Results: Among 116 leads, 17 were identified as perforated on CT, 12 leads were equivocal,
Thoracic
and 87 were not perforated. Interobserver agreement for CT perforation vs nonperforation was good (k ¼ 0.71); weighted kappa for the entire 5-point scale was moderate (k ¼ 0.54). Beam hardening artifacts were common, with a mean value of 2.1. The 2 observers
Conflict of interest: Roger Carrillo is a consultant for Spectranetics, Medtronic, Inc., St. Jude Medical, Sorin, and Sensormatic and receives grants or research support from St. Jude Medical (NCT # 00940888), Medtronic (NCT # 00893386). The other authors declare no conflicts of interest. * Corresponding author. E-mail address: [email protected] (J.E. Fishman). 1934-5925/$ e see front matter ª 2014 Society of Cardiovascular Computed Tomography. All rights reserved. http://dx.doi.org/10.1016/j.jcct.2014.08.004
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385
identified perforation on chest radiography with an average sensitivity of 15% compared with CT. The 2 observers did not agree on any cases of chest radiographic perforation (k ¼ 0.1). Conclusion: Electrocardiography-gated noncontrast cardiac CT imaging with oblique multiplanar analysis can identify potential lead perforation with a moderate-to-good level of interobserver agreement. Chest radiography demonstrates poor sensitivity and interobserver agreement compared with CT. ª 2014 Society of Cardiovascular Computed Tomography. All rights reserved.
1.
Introduction
Approximately 67,000 defibrillators, 178,000 pacemakers, 33,000 cardiac resynchronization defibrillators, and 7000 cardiac resynchronization pacemakers were implanted in the United States in 2004.1 Subsequent device and lead extraction may be required for indications such as infection, device malfunction, and lead breakage. Lead extraction may be accomplished by mechanical or energy-assisted means such as thoracotomy, electrocautery, and lasers. In any patient with cardiac leads, early or late lead perforation may occur through the myocardium, into the epicardial space, pericardium, or chest wall. Lead perforation is often clinically occult and only infrequently accompanied by symptoms such as pain. Pre-extraction knowledge of the presence of lead perforation could significantly impact the method and techniques chosen for lead extraction. Chest radiography in 2 views may occasionally demonstrate clear evidence of perforation but is inherently limited because distinction between the ventricular cavity, myocardium, and pericardium cannot be made. Chest CT would seem to have much to recommend it for lead tip identification, and there have been numerous case reports and occasional larger series published to this end.2e6 CT images of leads, however, can be challenging to interpret for 2 main reasons: the heart and leads are in motion, and metallic materials can produce severe streak artifacts.7 Our objective was to analyze a series of chest radiographs and electrocardiography (ECG)-gated noncontrast cardiac CT scans of patients with device leads before extraction to determine the degree of confidence in identifying perforation, calculate interobserver agreement, and compare radiographic results with those of CT.
2.
Methods
This project was approved by the University of Miami institutional review board with waiver of informed consent. A cardiothoracic surgeon (R.C.) has been performing laserassisted and operative lead extraction at the University of Miami Hospital since September 2008. As part of clinical protocol, ECG-gated noncontrast cardiac CT scanning was performed before the extraction. Among all 329 patients who underwent lead extraction between November 2008 and April 2011, a nonrandom convenience subset of patients was selected for retrospective radiographic and CT analysis. To capture as many patients with potentially perforated leads as possible, the subset included all patients (n ¼ 16) who had a preprocedure suspicion of possible lead perforation based on
the radiographic and/or CT report generated at the time of the study. A larger group (n ¼ 34) of randomly selected patients whose imaging did not suggest perforation was added for a total group size of 50 nonrandom patients with 116 leads. The obtained images included single anteroposterior (n ¼ 25) or 2view (n ¼ 25) chest radiography. Chest CT was performed on a Siemens ASþ 128-slice, single-source scanner (Siemens Healthcare, Malvern, PA) using ECG gating at 120 kVP, 150 to 190 mAs, and a mixture of both prospective and retrospective technique. Prospectively gated studies were centered at 70% of the R-R interval. The “best diastolic” phase selected by the scanner was used for retrospectively gated studies, which ranged from 66% to 86% of the R-R interval. Multiphase images were isovolumetrically (0.6 0.6 mm) reconstructed with no overlap using a B26f smooth cardiac kernel and interpreted using oblique multiplanar reformat (MPR) in TeraRecon iNtuition (version 4.4.7; Foster City, CA). Heart rate was not recorded and no beta blockers were administered. Subsequently, patients underwent laser lead extraction with concurrent transesophageal ECG of a total of 106 leads. Ten leads were not extracted. Each extracted lead was transected proximally and a laser sheath was inserted over the lead, advanced in the direction of the lead tip, and activated at points of lead adhesion. Lasering was halted 1 cm from the lead tip in the myocardium unless the CT scan demonstrated lead perforation, in which case the laser sheath was halted at a prudent distance from the tip to prevent a larger perforation. One patient whose preprocedure CT demonstrated lead perforation had a left anterior minithoracotomy performed to assist in safe removal of the lead, which was directly observed extending out the right ventricular chamber. Two other patients without perforation also had thoracotomies performed for other reasons. There were 4 deaths among the 50 patients during their hospitalizations, all due to sepsis and resulting multiorgan failure in patients whose indication for lead removal was infection. There were no deaths attributable to the lead extraction procedure itself. One patient had a surgical site hematoma requiring drainage, constituting a minor complication of lead removal.
2.1.
Image analysis
Two radiologists (E.G., J.F.), who were not involved in the initial clinical interpretation of the CT scans and who were unaware of whether there was suspected lead perforation, independently and randomly evaluated the imaging studies. Using an image reconstructed in mid-diastole, orthogonal oblique MPRs were created to demonstrate the length of the lead tip in 2 orthogonal views with the third view being a
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cross-section of the lead. Dual-window and level Hounsfield unit (HU) settings were routinely applied. The first setting was designed for optimal demarcation of the lead tip while minimizing streak artifacts, to most closely demonstrate the architecture of the lead tip as seen on the CT scout view (Fig. 1AeC). This used a relatively wide window (w1400) with a center of approximately 300 HU, equivalent to a modified bone setting. As on nonecontrast-enhanced CT the density of the right ventricle blood pool is generally within 100 HU of epicardial fat, a higher contrast window and level setting was then applied for optimal demarcation of the interface between the right ventricular myocardium and blood pool and the epicardial fat. This was similar to a mediastinal setting, using a center around 50 HU and a narrower width of approximately 400 HU (Fig. 1D). Using these images, the presence of perforation was graded on a 5-point scale according to the following. Grade 1: tip clearly within the region of the blood pool and myocardium. Grade 2: tip abutting the blood pool and myocardiumepicardial fat interface but does not measurably cross the interface.
Grade 3: tip passes no more than 2 mm past the blood pool and myocardium-epicardial interface, 2 mm being chosen because that is the approximate length of the lead tip screw. Grade 3 was considered equivocal for perforation. Grade 4: tip crosses >2 mm and no greater than 4 mm past the blood pool and myocardium-epicardial fat interface. Grade 5: tip crosses >4 mm past the blood pool and myocardium-epicardial fat interface. After all independent readings, a consensus reading was performed when the independent readings were not either grade 1 or 2, grade 3, or grade 4 or 5. Motion artifacts were noted when sufficient to degrade interpretation of lead position (absent ¼ 0, present ¼ 1), and metallic streak artifacts were graded on a 4-point scale (from none ¼ 0 to severe ¼ 3). Chest radiographs were reviewed using a picture archiving and communication system workstation (Philips iSite, Andover, MA). A 5-point scale was used to judge lead position (1 ¼ definitely not perforated, 2 ¼ probably not perforated, 3 ¼ equivocal, 4 ¼ probably perforated, and 5 ¼ definitely perforated). Consensus interpretations were not performed in cases of disagreement.
Fig. 1 e Perforated right ventricular implantable cardioverter-defibrillator lead. (A) CT scout image demonstrating the architecture of the lead. (B, C) orthogonal multiplanar reformat images using modified bone settings redemonstrate the lead tip architecture. (D) Same image as (C) using mediastinal settings better demonstrates grade-5 perforation of the lead tip (arrow) past the pericardium (arrowheads).
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2.2.
Statistical analysis
Continuous and categorical variables were analyzed using SAS, version 9.1 (SAS Institute Inc., Cary, NC). Continuous variables are analyzed as mean standard deviation. Categorical variables are analyzed as numbers or percentages. The Fisher exact test was used for 2 2 contingency tables. P values <.05 were considered statistically significant. Interobserver agreement was calculated using MedCalc, version 12.5.0 (MedCalc Software, Ostend, Belgium).
3.
Results
Table 1 e Subject and lead characteristics. Characteristic
time for all leads studied was 4.8 4.8 years; of these, the mean implantation time of all the leads that were perforated was 2.6 3.1 years. The perforated leads included 8 pacemaker leads and 9 ICD leads. The mean implantation times for perforated leads were 3.5 3.7 years (pacemaker) and 1.9 2.1 years (ICD), respectively. All perforations were through the right ventricular wall. Intraprocedural transesophageal ECG demonstrated 1 pericardial effusion in a patient with a perforated lead. The echocardiograms were performed for monitoring purposes rather than perforation detection without attention to leads, and no perforations were thereby visualized.
3.1.
Clinical data regarding the patients and leads are listed in Table 1. The patients included 32 men (64%) and 18 women (36%), with an age of 67.8 17.6 years. The ejection fraction was 35.0 13.8% and the average New York Heart Association class was 2.7 0.8. Significant comorbidities included coronary artery disease in 29 patients (58%), diabetes mellitus in 17 (34%), and hypertension in 40 (80%). Fourteen patients (28%) had previous heart surgery. The patient indications for lead extraction were infection (29 patients) and malfunction (21 patients). Within our nonrandomly selected group, leads excised for infection were less likely to be perforated than not perforated, whereas leads excised for malfunction were more likely to be perforated than not perforated (both P < .001). There were 116 leads studied with 2.0 0.9 leads per patient. There were 78 pacemaker leads, 35 implantable cardioverterdefibrillator (ICD) leads, and 3 epicardial leads. Within our nonrandomly selected group, ICD leads were more likely to be perforated than pacer leads (P ¼ .046). The mean implantation
Perforated Nonperforated (n ¼ 17) (n ¼ 33)
Age (y), mean SD 70.1 16.1 Gender Male 12 Female 5 31.3 8.9 BMI (kg/m2), mean SD Ejection fraction (%), 34.7 13.7 mean SD NYHA class, 2.7 0.8 mean SD Hemodialysis 1 CAD 9 DM 3 HTN 14 Indication Infection 4 Malfunction 13 Lead type ICD 9 Pacer 8 Epicardial 0
P value
66.8 18.6
NS
20 13 28.2 6.1
NS NS NS
35.1 13.7
NS
2.7 0.8
NS
3 20 14 26
NS NS NS NS
25 8
<.001 <.001
26 70 3
.046 vs pacer ()
BMI, body mass index; CAD, coronary artery disease; DM, diabetes mellitus; HTN, hypertension; ICD, implantable cardioverterdefibrillator; NS, not significant; SD, standard deviation.
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Chest CT results
Among 116 leads, 17 were identified as perforated on MPR CT, 12 leads were graded as equivocal (grade 3), and 87 were considered not perforated (Figs. 1, 2). For interobserver agreement of all MPR CT readings, weighted kappa for the 5-point scale was moderate (k ¼ 0.54). After consolidating results into 2 categories (not perforated, grades 1e3, vs perforated, grades 4e5), interobserver agreement for CT perforation vs nonperforation was good (k ¼ 0.71). Of 17 leads judged to be perforated, in 7 cases both readers indicated grade 5; in 5 cases 1 reader indicated 5 and the other, 4; in 2 cases both indicated 4; and in 3 cases there was a disagreement regarding the presence of perforation, which in consensus was determined to be grade 4. There were 16 leads suspected of perforation based on initial CT scan results (which did not use oblique MPR analysis). Of these, 12 were perforated and 4 not perforated according to MPR CT. There were 5 cases judged to be perforated by oblique MPR analysis that were not suspected of perforation based on the clinical CT reading; 3 of these were the consensus cases assigned grade 4, and the other 2 were grade 4 and grade 4 or 5. Sensitivity and specificity of clinical CT assessment vs MPR CT readings were 71% and 96%, respectively; positive and negative predictive values were 75% and 95%, respectively. Leads were graded on both metallic streak artifact and motion artifact. Using a 4-point scale (maximum grade 3), metallic artifact among all leads was 2.1 0.7. In the 9 cases in which there was a disagreement about perforation, the value was slightly higher (2.3 0.7) but not significantly different. Motion artifact (0 ¼ no, 1 ¼ yes) was 0.3 0.4 for both all leads and for the 9 cases of disagreement (Fig. 3).
3.2.
Chest radiographic results
Observer 1 judged 6 leads to be probably or definitely perforated, of which 3 were judged perforated by MPR CT, yielding a sensitivity of 18% and a specificity of 97%. Observer 2 judged 6 leads to be probably or definitely perforated, of which 2 were judged perforated by MPR CT, yielding a sensitivity of 12% and a specificity of 96%. Of the 7 cases where both readers independently judged a definite perforation (grade 5) on MPR CT, 1 observer identified 1 perforation on chest radiography. The 2 observers did not agree on any cases of perforation on chest radiography. For interobserver agreement of all radiographic readings, weighted kappa for the 5-point scale was poor (k ¼ 0.12). After consolidating results to 2 categories (not
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Fig. 2 e Dual right ventricular leads. (A) CT scout view shows both a right ventricular pacemaker lead and an ICD (implantable cardioverter-defibrillator) lead (more caudal in location). (B) Multiplanar reformat CT image using modified bone display setting shows the architecture of the leads. (C) Image (B) using mediastinal display setting shows grade-4 perforation of the pacemaker lead more than 2 mm past the blood pool and myocardium-epicardial interface (arrow shows junction of lead and interface). The inferiorly positioned ICD lead abuts but does not pass the interface.
perforated vs perforated), interobserver agreement for perforation vs nonperforation on chest radiographs was worse than random chance (k ¼ 0.1).
4.
Discussion
Pacemakers and ICD devices are being implanted in ever increasing numbers of patients and a small proportion are requiring subsequent lead removal for a variety of indications. Despite the proliferation of such devices and the increasing utilization of CT scanning of the heart and chest, there has been relatively little published regarding the use of CT to accurately identify lead tip position or perforation. Most of the published literature on this topic has consisted of case reports of perforated leads. Reefat et al8 described 2 cases of late lead perforation (defined as the perforation of the lead through the myocardium >1 month after implantation), and summarized the literature concerning 51 other such cases. They concluded that CT may be a useful imaging modality but imply that there are limitations in sensitivity and specificity because of metallic streak artifacts. In part because of these limitations, they suggest that the meaning of detecting a “near perforation” in an asymptomatic patient is unclear, indicating follow-up. In another report of 3 cases of perforation, 2 patients underwent
“cardiac CT,” presumably meaning ECG gated, and both axial and coronal images were used to demonstrate the findings.3 However, the authors did not provide a rationale for using gating nor did they use an oblique multiplanar analysis method to optimally visualize the lead tip. Standard (ie, noneECG gated) CT and straight reconstruction planes were also used in the largest series of lead CT scanning published to date.9 Rather than patients with suspected perforation or other lead-related problems, that study reviewed a consecutive series of 100 patients with leads who were scanned for other reasons. The authors diagnosed lead perforation in 15% of the atrial leads and 6% of the ventricular ones. A relative shortcoming of their study is the variety of slice thicknesses used (up to 5 mm). Leads are commonly <5 mm in diameter; optimally, CT slice thicknesses should be less than half of the size of the object being imaged. In addition, diagnostic-quality MPR images require slice thicknesses of 2 mm or less. Furthermore, they identified the lead tip as the center of the star artifact rather than from optimal visualization of the lead structure. These factors may help account for the significant difference in identification of atrial lead perforations, of which we did not encounter any in our study. Our study is the first of which we are aware that assesses the performance of CT and chest radiography in a large series of patients requiring lead removal. Our motivation was to
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Fig. 3 e Motion artifact. (A) CT scout view demonstrating right atrial and ventricular pacemaker leads. (B) Coronal CT image demonstrating the right ventricular lead (arrow) and an artifactual “second” lead more cephalad in location. (C, D) Magnified mediastinal display setting multiplanar reformat images show perforation of the lead into the pericardium (arrowheads).
potentially improve the safe performance of lead extraction. Laser lead extraction involves the advancement of a laser sheath over the lead to disrupt fibrous bands and facilitate extraction. Should a lead be perforated and the sheath advanced too close to the tip, the potential exists to enlarge the perforation orifice. The procedural instructions advise advancing the sheath no closer than 1 cm from the tip, but this is a recommendation only, and if the lead is perforated by >1 cm then complications may ensue. At our center, the performance of laser lead removal is a safe procedure with a combined major and minor complication rate of 6.3%; the extent to which our preprocedural CT scanning has benefited safety is unknown. In our study, ECG-gated cardiac CT demonstrated good interobserver agreement for the identification of perforation. In most cases, we were able to use MPR reconstructions to achieve an image demonstrating the known lead tip configuration, increasing confidence in the assessment of tip position. There are, however, several challenges to the precise identification of the lead tip, mainly due to metallic streak artifacts. There are several research methods described for the generation of images with fewer metallic artifacts which may eventually be relevant to this application of CT.10,11 Despite using cardiac gating, motion artifacts were
nevertheless identified in approximately 30% of the imaged leads. Heart rate was not recorded during this study; therefore, we do not know the extent to which tachycardia or irregular rhythms were present and thus the extent to which b-blocker administration might have reduced motion artifacts. All the consensus grade-5 perforations were detected on the clinical review of the CT scan (ie, without oblique MPR analysis). Our use of MPR image reconstruction identified 5 potential perforations not detected clinically or by routine reading of the preprocedure CT scans, but 4 of those 5 perforations were grade 4 (ie, <4 mm past the myocardium and not into the pericardium). The clinical relevance of identifying perforation into the epicardial fat (in contrast to perforation of the pericardium) is unknown, as is the most appropriate management. Presuming that a “minor” perforation may eventually progress to a “major” perforation by continued pulsatile motion of the screw-tipped lead, follow-up imaging would appear to be appropriate. Our study showed that chest radiography is not a reliable method for evaluating lead perforation, demonstrating both very poor sensitivity and interobserver agreement compared with CT scanning. There are nevertheless valid clinical reasons for obtaining a chest radiograph in patients suspected
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of problems with device leads, such as inappropriate positioning (eg, atrial lead not engaged superiorly into the right atrial appendage), evidence of infection (eg, septic emboli), or sequela of perforation (eg, pleural or pericardial effusions). Limitations of our study include the use of a nonrandom subset of all patients who underwent ECG-gated noncontrast cardiac CT for the evidence of lead perforation. There was no definitive gold standard for the presence of lead perforation such as direct assessment via thoracotomy or thoracoscopy. Only 1 of the 17 perforated leads detected on CT was directly visualized at thoracotomy. We did not observe a high rate of complications of lead removal despite the presence of 17 perforated leads; the extent to which preprocedural suspicion of 12 of those perforations (including all the grade 5 perforations) may have improved procedural outcomes is unknown. Our population was not consecutive so we are unable to comment on overall perforation rates in patients referred for lead removal. We did not have access to methods of reducing metal artifact on the CT images nor did we use a “sharp” reconstruction kernel. Our retrospective study design resulted in a combination of retrospectively and prospectively ECGgated exams. However, only a single “best diastolic” phase was routinely archived to picture archiving and communication system for the retrospective studies. We are unable to compare the relative merits of those 2 acquisition methods for lead evaluation, specifically whether motion artifact might be reduced if a phase other than “best diastolic” were analyzed. We cannot determine the radiation dose for our patients because the values were not archived consistently during the period of time from which patients were selected. Dose is substantially lower with prospective than retrospective gating and would be preferable assuming that image quality is equivalent. We did not incorporate measurements of intrarater reliability into our project design. Regarding chest radiography, we did not have 2-view radiographs in half of the patients.
5.
Conclusion
ECG-gated noncontrast cardiac CT with oblique MPR and dualwindow analysis demonstrates good interobserver agreement for the identification of lead perforation. Future improvements in image generation and processing might reduce metallic streak artifacts and allow improved confidence in lead tip position assessment. Chest radiography is not an accurate method for identifying lead perforation.
Acknowledgments The authors thank Noam Alperin, PhD, and Ahmet M Bagci, PhD, Advanced Image Processing Laboratory, Department of Radiology, University of Miami Miller School of Medicine, for calculations of kappa statistics.
references
1. Zhan C, Baine WB, Sedrakyan A, Steiner C. Cardiac device implantation in the United States from 1997 through 2004: a population-based analysis. J Gen Intern Med. 2008;23(Suppl 1):13e19. 2. Sussman SK, Chiles C, Cooper C, Lowe JE. CT demonstration of myocardial perforation by a pacemaker lead. J Comput Assist Tomogr. 1986;10(4):670e672. 3. Henrikson CA, Leng CT, Yuh DD, Brinker JA. Computed tomography to assess possible cardiac lead perforation. Pacing Clin Electrophysiol. 2006;29:509e511. 4. Merla R, Reddy NK, Kunapuli S, Schwarz E, Vitarelli A, Rosanio S. Late right ventricular perforation and hemothorax after transvenous defibrillator lead implantation. Am J Med Sci. 2007;334(3):209e211. 5. Schroeter T, Doll N, Borger MA, Groesdonk HV, Merk DR, Mohr FW. Late perforation of a right ventricular pacing lead: a potentially dangerous complication. Thorac Cardiovasc Surg. 2009;57(3):176e177. 6. Yoshimori A, Kobori A, Michihiro N, Furukawa Y. Delayed perforation of the right ventricular wall by a single standardcaliber implantable cardioverter-defibrillator lead detected by multidetector computed tomography. Korean Circ J. 2011;41:689e691. 7. Barrett JF, Keat N. Artifacts in CT: recognition and avoidance. Radiographics. 2004;24(6):1679e1691. 8. Refaat MM, Hashash JG, Shalaby AA. Late perforation by cardiac implantable electronic device leads: clinical presentation, diagnostic clues, and management. Clin Cardiol. 2010;33(8):466e475. 9. Hirschl DA, Jain VR, Spindola-Franco H, Gross JN, Haramati LB. Prevalence and characterization of asymptomatic pacemaker and ICD lead perforation on CT. Pacing Clin Electrophysiol. 2007;30:28e32. 10. Boas FE, Fleischmann D. Evaluation of two iterative techniques for reducing metal artifacts in computed tomography. Radiology. 2011;259(3):894e902. 11. Bamberg F, Dierks A, Nikolaou K, Reiser MF, Becker CR, Johnson TR. Metal artifact reduction by dual energy computed tomography using monoenergetic extrapolation. Eur Radiol. 2011;21(7):1424e1429.