A Comparative Study of Defibrillator Leads at a Large-Volume Implanting Hospital: Results From the Pacemaker and Implantable Defibrillator Leads Survival Study ("PAIDLESS")

Abstract: Objectives. The purpose of the study was to examine survival in the implantable defibrillator subset of implanted leads at a large-volume implanting hospital. Background. Implantable lead survival has been the subject of many multicenter studies over the past decade. Fewer large implanting volume single-hospital studies have examined defibrillator lead failure as it relates to patient survival and lead construction. Methods. This investigator-initiated retrospective study examined defibrillator lead failure in those who underwent implantation of a defibrillator between February 1, 1996 and December 31, 2011. Lead failure was defined as: failure to capture/sense, abnormal pacing and/or defibrillator impedance, visual insulation defect or lead fracture, extracardiac stimulation, cardiac perforation, tricuspid valve entrapment, lead tip fracture and/or lead dislodgment. Patient characteristics, implant approach, lead manufacturers, lead models, recalled status, patient mortality, and core lead design elements were compared using methods that include Kaplan Meier analysis, univariate and multivariable Cox regression models. Results. A total of 4078 defibrillator leads were implanted in 3802 patients (74% male; n = 2812) with a mean age of 70 ± 13 years at Winthrop University Hospital. Lead manufacturers included: Medtronic: [n = 1834; 801 recalled]; St. Jude Medical: [n = 1707; 703 recalled]; Boston Scientific: [n = 537; 0 recalled]. Kaplan-Meier analysis adjusted for multiple comparisons revealed that both Boston Scientific’s and St. Jude Medical’s leads had better survival than Medtronic’s leads (P<.001 and P=.01, respectively). Lead survival was comparable between Boston Scientific and St. Jude Medical (P=.80). A total of 153 leads failed (3.5% of all leads) during the study. There were 99 lead failures from Medtronic (5.4% failure rate); 56 were recalled Sprint Fidelis leads. There were 36 lead failures from St. Jude (2.1% failure rate); 20 were recalled Riata or Riata ST leads. There were 18 lead failures from Boston Scientific (3.35% failure rate); none were recalled. Kaplan Meier analysis also showed lead failure occurred sooner in the recalled leads (P=.01). A total of 1493 patients died during the study (mechanism of death was largely unknown). There was a significant increase in mortality in the recalled lead group as compared with non-recalled leads (P=.01), but no significant difference in survival when comparing recalled leads from Medtronic with St. Jude Medical (P=.67). A multivariable Cox regression model revealed younger age, history of percutaneous coronary intervention, baseline rhythm other than atrial fibrillation or atrial flutter, combination polyurethane and silicone lead insulation, a second defibrillation coil, and recalled lead status all contributed to lead failure. Conclusion. This study demonstrated a significantly improved lead performance in the Boston Scientific and St. Jude leads as compared with Medtronic leads. Some lead construction variables (insulation and number of coils) also had a significant impact on lead failure, which was independent of the manufacturer. Recalled St. Jude leads performed better than recalled Medtronic leads in our study. Recalled St. Jude leads had no significant difference in lead failure when compared with the other manufacturer’s non-recalled leads. Defibrillator recalled lead status was associated with an increased mortality as compared with non-recalled leads. This correlation was independent of the lead manufacturer and clinically significant even when considering known mortality risk factors. These results must be tempered by the largely unknown mechanism of death in these patients.

J INVASIVE CARDIOL 2015;27(6):292-300

Key words: defibrillator lead failure, defibrillator lead survival

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Since Hauser and colleagues first reported on the Medtronic Sprint Fidelis defibrillator lead failure in 2007, two wide-ranging class I defibrillator lead recalls have been issued by the United States (US) Food and Drug Administration (FDA). These recalled leads included the Sprint Fidelis (Medtronic) in 2007, and the Riata and Riata ST (St. Jude Medical) in 2011.^1,2 Many studies have analyzed the performance of these leads and have highlighted their specific design flaws, ie, conductor fracture in the Sprint Fidelis, and insulation failure with externalization of the lead’s conductor in the Riata family of leads.^2-13 Most of these studies were multicenter in design, and if only one hospital was involved, they often did not have a high volume of lead implantation (less than 500 leads per manufacturer) or a complete assortment of the major US leads (including the previously mentioned St. Jude and Medtronic leads, plus those manufactured by Boston Scientific).^2-13

The purpose of this study was to compare patient characteristics, implant approach, lead construction, recalled status, and lead survival of each manufacturer’s leads at Winthrop University Hospital (a single large-volume implanting hospital). The primary endpoint was defibrillator lead failure with a secondary endpoint of patient mortality.

Methods

This was a non-randomized retrospective investigator-initiated study, and was approved by the Winthrop University Hospital Institutional Review Board. Patient and implant data were de-identified according to the Health Insurance Portability and Accountability Act. The patient database was designed and populated to include patient and lead characteristics. Appendix A shows the complete list of variables (Lead Database Glossary). 

Lead failure was defined according to the Medtronic System Longevity Study, which included failure to capture and sense, abnormal pacing impedance (less than 400 ohms or greater than 2000 ohms), abnormal defibrillation impedance (less than 20 ohms or greater than 200 ohms), insulation defect, lead fracture, extracardiac stimulation, cardiac perforation, tricuspid valve entrapment, lead tip fracture, and/or lead dislodgment.¹ The review of all lead failures was blinded to the implant doctor’s name and patient identifiers.

All Winthrop University Hospital defibrillator leads that were implanted between February 1, 1996 and December 31, 2011 were included in this study. Exclusion criteria included non-Winthrop implants and records missing critical data such as

unidentifiable leads. Data were obtained from the Electrophysiology Database Management System, Paceart System, remote web-based device monitoring systems, manufacturer-provided lead analysis data, and mortality status as derived from the Social Security Death Index.¹⁵

Statistical analysis. Patient characteristics were compared among the different manufacturers. In addition, the patient characteristics including implant approach were examined as it relates to lead failure. The specific lead manufacturers as well as their families were compared. Leads were also categorized according to recalled and non-recalled status, and their performances were compared as well as their association to patient mortality (obtained from the Social Security DeathIndex). In addition, the study compared lead construction characteristics, which included fixation, polarity, lead diameter, distal coil diameter, lead body design (isodiametric or not isodiametric, insulation coating silicone/polyureth

ane combination), construction symmetry (asymmetrical vs symmetrical), steroid elution, number of coils, tip to ring spacing, cathode and anode surface areas, helix extension, coil treatment/overlay (none vs silicone backfield), number of compression lumens, number of filled lumens, total number of lumens, and cable construction (1 x 19 vs 7 x 7).  

Continuous data were represented as mean ± standard deviation (unless otherwise specified) and the categorical data as proportions. The main endpoint of the study was time to lead failure. Survival estimates and accumulative event rates 

were compared by the Kaplan-Meier method using the time to first event from the endpoint. The log-rank test was used to compare the Kaplan-Meier survivor curves between manufacturers and lead families. Hazard ratios with 95% confidence intervals (CIs) were calculated using Cox proportional model. Unadjusted Cox with regression analysis was performed on all appropriate clinical variables using time-dependent failure variables (implant age failures) as the endpoint. All variables with unadjusted P-values of <.25 were considered for a multivariable model except for the co-linear variables, which were not included in the multivariable model. A stepwise multivariable Cox proportional hazard model was built to find risk 

factors of lead failures. Ties in the failure times were handled by the Exact method. The proportionality assumption was tested using all time-dependent variables in the model to make sure that the assumption was met.¹⁷ All calculations were performed using SAS 9.3 (SAS Institute) for Windows. P<.05 was considered statistically significant.

Results

Table 1 shows the patient characteristics in this study. There were 3846 unique patients who underwent defibrillator lead implantation; 44 of these had an unknown status and were removed from the study.  The remaining 3802 patients had amean age of 70 ± 13 years. A total of 2812 patients (74%) were men; 2731 patients (72%) had coronary artery disease. Table 1 shows the specific patient characteristics as they relate to the variables, which were specifically categorized on the implant report.

The implanting approach for 2199 leads (54%) was via the left subclavian and/or axillary approach vs 1628 leads (40%) via the left cephalic venous approach. The remaining minority were performed on the right side, including 104 via the right cephalic venous approach (3%) and 138 via the right subclavian and/or axillary approach (3%). The approach was unclear in 9 implants. A total of 1111 leads (27%) were singularly implanted as the defibrillator lead. A total of 1690 leads (41%)were implanted with one prior ICD lead previously implanted, 1199 leads were implanted with two prior leads previously implanted, and 78 leads were implanted with three or more leads previously in place. There was no significant difference in lead failure rates among the eight operating physicians (P=.33). At the end of the study (December 31, 2011), there were 2211 active leads (54%). The reasons for inactivity included 1549 leads (38%) were out of service 

as a result of patient death, 137 leads (3%) were extracted without evidence of failure, and 178 leads (4%) 

were either capped or replaced. The rationale for removal of the leads included 33 for infection (0.81%), 151 for failure (4%), 39 for upgrade/change (0.96%), and 92 were based on operator and/or patient preference with respect to their clinical situation as it related to the recalled status (2%).  

Leads were classified within the given manufacturer as pertaining to a particular family of leads. The Medtronic family included the Sprint leads (n = 158; 4%), Sprint Fidelis leads (n = 801; 20%), and Sprint Quattro leads (n = 875; 21%). St. Jude Medical leads included Riata leads (n = 479 leads; 12%), Riata ST leads (n = 227; 6%), and Durata leads (n = 1001; 25%). Boston Scientific leads included Endotak Endurance leads (n = 105; 3%), Endotak Reliance leads (n = 324; 8%), and Endotak DSP leads (n = 108; 3%). The following leads underwent first-time implantation at Winthrop University Hospital: 537 Boston Scientific leads (13%) as compared with 1834 Medtronic leads (45%) and 1707 St. Jude Medical leads (42%).

The overall lead survival rate was 86.8% and the total follow-up period was 15.6 years with mean lead survival time of 14 years (standard error [SE] = 0.12). Non-recalled lead survival rate was 88.5% with mean survival time of 14.6 years (SE = 0.13) as compared with the recalled lead survival rate of 86.7% with a mean survival time of 9 years (SE = 0.07).

Table 2 shows all 153 defibrillator lead failures (3.5% of all leads) in this study by manufacturer and specific model number. There were 99 lead failures from Medtronic (5.4% failure rate); 56 were recalled Sprint Fidelis leads. There were 36 lead failures from St. Jude (2.1% failure rate); 20 were recalled Riata or Riata ST leads. There were 18 lead failures from Boston Scientific (3.35% failure rate); none were recalled. 

Table 3 shows risk factors of failure from unadjusted Cox proportional hazard model. Unadjusted hazard ratios and P-values of all variables are reported. Table 4 shows variables that were significant via the adjusted Cox proportional hazard model and includes the adjusted hazard ratios and P-values. A stepwise Cox proportional hazard model revealed our final model (Table 4), which included age (hazard ratio [HR] = 0.98; P=.01), percutaneous coronary intervention (HR = 1.74; P=.01), rhythms (sinus rhythms vs atrial fibrillation and/or atrial flutter [HR = 2.72; P=.01]); significant conduction disease vs atrial fibrillation and/or atrial flutter (HR = 4.7; P<.001), insulation (silicone with polyurethane combination vs silicone [HR = 2.47; P<.001]), number of coils (one vs two [HR = 0.26; P=.01]) and recalled status (HR = 2.08; P<.001) as the independent predictors of failure. Importantly, age had a slight impact on lead survival, ie, for every year increase of patient age, there was a 2% decrease in lead failure (HR = 0.98; P=.01). In addition, characteristics such as coronary artery disease did not have a significant impact. Many of the lead construction variables were significant by unadjusted analysis. However, only variables with P<.25 after unadjusted analysis were considered for multivariable analysis. All co-linear variables were removed from the multivariable analysis (Appendix 1). 

The 4078 defibrillator leads implanted in the study included Medtronic (n = 1834; 801 recalled), St. Jude Medical (n = 1707; 703 recalled), and Boston Scientific (n = 537; 0 recalled). Figure 1 shows Kaplan-Meier analysis adjusted for multiple comparisons, which revealed that Boston Scientific leads had better survival compared to Medtronic (P<.001), but survival rate was similar when compared with St. Jude Medical (P=.80). St. Jude Medical leads had better survival than Medtronic leads (P=.01). Figure 2A shows Kaplan Meier curves comparing recalled vs non-recalled leads. Lead failure occurred sooner in the recalled leads (P=.01). Figure 2B shows Kaplan Meier curves comparing Medtronic with St. Jude leads. Medtronic recalled leads failed sooner than St. Jude recalled leads (P<.001). Figure 2C shows Kaplan Meier analysis of St. Jude recalled leads vs all non-recalled leads. There was no significant difference in lead survival between St. Jude recalled leads and all non-recalled leads (P=.45). There was no significant difference among the non-recalled leads with respect to lead failure. 

A total of 1549 patients died during our study period, of which 1493 had only the original defibrillator lead. The mechanisms of death were largely unknown. Figures 3A and 3B show a Kaplan Meir analysis of recalled leads as compared with the non-recalled leads with respect to patient mortality as obtained from the Social Security Death Index. The analysis was performed only on the first Winthrop University Hospital implantable defibrillator lead (n = 3802) and time to mortality was analyzed. This analysis demonstrated that there was a significant increase in mortality in the recalled lead group (P=.01), but no significant difference in survival when comparing recalled leads from Medtronic to St. Jude (P=.67).

Discussion

This investigator-initiated study confirmed many of the findings of most multicenter or smaller single-hospital trials.^1-13 Specifically, our study identified a correlation between recalled lead status and mortality that was independent of known mortality risk factors such as age, congestive heart failure, and ejection fraction. Although the etiology of death was largely unknown, it is intriguing to consider that these leads may have impacted patient mortality. Second, this study demonstrated that recalled leads fail sooner than non-recalled leads. In addition, the St. Jude recalled leads (Riata and Riata ST) appeared to perform equivalent to non-recalled leads with respect to lead survival. The same could not be said of the Medtronic Sprint Fidelis lead, which had a significantly higher failure rate than the other non-recalled leads (Medtronic, St. Jude, and Boston Scientific). The present study may be distinguishable from those earlier trials based on it being a single large-volume implanting hospital examining lead performance over 16 years.^1-13 In addition, this study examined all aspects of the implant procedure including patient characteristics, implant approach, and number of leads implanted, and included a very detailed lead construction design analysis.  

A multivariable analysis in the current study demonstrated a number of unique findings. First, for every year increase in patient age, there was a 2% decrease in lead failure. Gerard and colleagues also found that younger age was associated with a higher rate of lead failure in the recalled Medtronic Sprint Fidelis lead.¹⁸ Their analysis looked at certain age cut-offs, whereas we analyzed age as a continuous variable. Our findings appeared to generalize those of Gerard and colleagues to all three US manufacturers regardless of recalled lead status. Second, history of percutaneous coronary intervention was associated with a 74% increase in lead failure. The reason for this is unclear. Third, atrial fibrillation and/or atrial flutter at the time of implant was associated with a lower risk of lead failure than other rhythms (paced rhythm, heart block, bundle branch block, or sinus rhythm). The reason for this finding is not entirely clear; however, it might have been related to the presence of fewer leads, since an atrial lead implant would have been less likely implanted in those with atrial dysrhythmias at the time of the procedure. This appeared to be the case in univariate, but not multivariable analysis. Fourth, the combination of polyurethane and silicone was associated with a higher lead failure rate than silicone alone. Fifth, a single coil lead had a 74% less risk of failure than a dual coil lead. The increased complexity of the latter’s lead design might explain this increased failure rate. Interestingly, the Sudden Cardiac Death in Heart Failure trial failed to demonstrate any improved outcome measures from the addition of a second coil lead as compared to a single coil lead.¹⁹ Finally, the presence of a recalled lead status was associated with twice the risk of lead failure vs those without such a status. The increased risk of failure in recalled leads was also demonstrated by the University of Pittsburgh Medical Center team.¹² Importantly, Groarke and his team demonstrated that these lead failures have significant cost implications that undermine the cost effectiveness of implantable defibrillators as a whole.²⁰

Surprisingly, the current study failed to demonstrate a significant independent effect of lead diameter, type of fixation, type of lead cable construction, or even lumen design (compression lumens and number of lumens). At first glance, one would think that lead diameter must play a significant role in lead design. Intuitively, a more complicated lead design in a smaller volume must be more prone to more error. But this analysis is complicated by the fact that over 40% of the Medtronic and St. Jude leads in this study were considered small diameter and/or were recalled. Our failure to conclusively prove that diameter is an important variable stands in contrast with other less-detailed lead construction studies which seemed to show an effect of lead diameter on failure.^21-23 

Study limitations. Our study has a number of important limitations. First, it was a non-randomized retrospective study. There is a need for a large, prospective, independent, longitudinal lead survival trial involving all major manufacturers’ leads with consistent detailed follow-up. The outcome of such a trial may shed further insight on lead failure. Second, only known captured lead failures were included in the failure group, and therefore the reported lead failure rates may significantly underestimate the true lead failure number. Third, mortality as determined via the Social Security Death Index is a very accurate survival tool, and thereby the association between mortality and recalled lead status appears real. However, the etiology of that mortality and the cause and effect linking lead failure to mortality remains unclear. Fourth, the study included implants between February 1, 1996 and December 31, 2011. The Medtronic Sprint Fidelis lead recall occurred in 2007, which permitted widespread patient notification and lead surveillance with a significant follow-up period following the notification. A medical device advisory regarding problems with the Riata and Riata ST leads was issued by St. Jude Medical on November 28, 2011 (33 days before the end of our trial).²⁴ This left almost no time to notify the patients and begin any significant lead surveillance and/or follow-up program. 

Conclusion

In closing, this study not only addressed all three major US manufacturers, but had the advantage of both patient number and follow-up time at a single hospital. This study highlighted the importance of recalled lead status and found that the presence of recalled lead status contributes to lead failure independent of manufacturer and may even play a role in patient mortality. The latter hypothesis is only conjecture at this point, and needs to be investigated in a much more rigorous and controlled prospective study in which the true etiology of mortality can be identified.  

Acknowledgment. We acknowledge the support and encouragement of the Winthrop University Hospital Administration including John Collins, CEO; Garry Schwall, COO; and Solomon Torres, Vice President of Cardiology. In addition, we appreciate the statistical support of the Winthrop University Hospital Research Institute and are grateful for the financial support of our research coordinators by Medtronic as well as Boston Scientific.   

References 

1. Hauser RG, Kallinen LM, Almquist AK, Gornick CC, Katsiyiannis WT. Early failure of a small-diameter high-voltage implantable cardioverter-defibrillator lead. Heart Rhythm. 2007;4(7):892-896.
2. Liu J, Brumberg G, Rattan R, Jain S, Saba S. Class I recall of defibrillator leads: a comparison of the Sprint Fidelis and Riata families. Heart Rhythm. 2012;9(8):1251.
3. Hauser RG, Hayes DL. Increasing hazard of Sprint Fidelis implantable cardioverter-defibrillator lead failure. Heart Rhythm. 2009;6(5):605-610. 
4. Faulknier BA, Traub DM, Aktas MK, et al. Time-dependent risk of Fidelis lead failure. Am J Cardiol. 2010;105(1):95-99.
5. Hauser RG, Maisel WH, Friedman PA, et al. Longevity of Sprint Fidelis implantable cardioverter-defibrillator leads and risk factors for failure: implications for patient management. Circulation. 2011;123(4):358-363. 
6. Ha AC, Vezi BZ, Keren A, et al. Predictors of fracture risk of a small caliber implantable cardioverter defibrillator lead. Pacing Clin Electrophysiol. 2010;33(4):437-443. Epub 2009 Dec 1.
7. Fazal IA, Shepherd EJ, Tynan M, Plummer CJ, McComb JM. Comparison of Sprint Fidelis and Riata defibrillator lead failure rates. Int J Cardiol. 2013;168(2):848-852. Epub 2012 Nov 6. 
8. Abdelhadi RH, Saba SF, Ellis CR, et al. Independent multicenter study of Riata and Riata ST implantagble cardioverter-defibrillator leads. Heart Rhythm. 2013;10(3):361-365. Epub 2012 Nov 2.
9. Parakash R, Exner D, Champagne J, et al. Failure rate of the Riata lead under advisory: a report from the CHRS Device Committee. Heart Rhythm. 2013;10(5):692-695. Epub 2013 Jan 17.
10. Rordorf R, Poggio L, Savastano S, et al. Failure of implantable cardioverter-defibrillator leads: a matter of lead size? Heart Rhythm. 2013;10(2):184-190. Epub 2012 Oct 11.
11. Schwartz J, Blangy H, Zinzius PY, Freysz L, Aliot E, Sadoul N. Recall alerts in implantable cardioverter-defibrillator recipients: implications for patients and physicians. Pacing Clin Electrophysiol. 2011;34(1):96-103.
12. Liu J, Brumberg G, Rattan R, et al. Longitudinal follow-up of implantable cardioverter defibrillator leads. Am J Cardiol. 2014;113(1):103-106.
13. Sung RK, Massie BM, Varosy PD, et al. Long-term electrical survival analysis of Riata and Riata ST silicone leads: National Veterans Affairs experience. Heart Rhythm. 2012;9(12):1954-1961.
14. Medtronic Criteria  for Cardiac Rhythm Disease Management (CRDM) and System Longevity Study. https://wwwp.medtronic.com/productperformance/content/method_for_estimating_leads.html
15. Social Security Death Index cross-referenced with manufacturer-supplied data to ensure up-to-date status of Out of Service leads that are due to the death of the patient (OOS-D) Social Security Death Index. https://www.genealogybank.com/gbnk/ssdi/
16. FDA Safety Communication. https://www.fda.gov/MedicalDevices/Safety/AlertsandNotices/ucm314930.htm
17. Fisher DL, Lin DY. Time-dependent covariates in the cox proportional-hazards regression model. Ann Rev Public Health. 1999;20:145-157.
18. Girerd N, Nonin E, Pinot J, et al. Risk of Sprint Fidelis defibrillator lead failure is highly dependent on age. Arch Cardiovasc Dis. 2011;104(6-7):388-395.
19. Aoukar PS, Poole JE, Johnson GW, et al. No benefit of a dual coil over a single coil ICD lead: evidence from the Sudden Cardiac Death in Heart Failure Trial. Heart Rhythm. 2013;10(7):970-976.
20. Groarke JD, Buckley U, Collison D, O’Neill J, Mahon NG, Foley B. Cost implications of defibrillator lead failures. Europace. 2012;14(8):1156-1160.
21. Van Rees JB, van Weisenes GH, Borleffs CJ, et al. Update on small-diameter implantable cardioverter-defibrillator leads performance. Pacing Clin Electrophysiol. 2012;35(6):652-658.
22. llis CR, Rottman JN. Increased rate of subacute lead complications with small-caliber implantable cardioverter-defibrillator leads. Heart Rhythm. 200;6(5):619-624. Epub 2009 Feb 14.
23. Borleffs CJ, van Erven L, van Bommel RJ, et al. Risk of failure of transvenous implantable cardioverter-defibrillator leads. Circ Arrhythm Electrophysiol. 2009;2(4):411-416.
24. Cheung JW, Al-Kazaz M, Thomas G, et al. Mechanisms, predictors, and trends of electrical failure of Riata leads. Heart Rhythm. 2013;10(10):1453-1459. Epub 2013 Jun 21.

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Baseline characteristics and unadjusted analysis:

Gender, age, implant age, coronary artery disease, myocardial infarction, coronary artery bypass grafting surgery, mitral valve replacement, aortic valve replacement, percutaneous coronary intervention, ischemic cardiomyopathy, dilated cardiomyopathy, hypertrophic cardiomyopathy, congestive heart failure, syncope, implantable defibrillator lead failure, significant conduction disease, left ventricular dysfunction, valvular heart disease, AV junction ablation, left ventricular ejection fraction, baseline rhythm (sinus, atrial fibrillation and/or atrial flutter, significant conduction disease as determined by presence of bundle branch block, AV block, and/or pacemaker requirement), implant approach (left or right side; cephalic versus axillary or subclavian venous approach), number of implanted leads, type of implant procedure, lead status (active or inactive), if inactive reason for inactive status, alive or dead, rationale for lead removal, lead failure, lead model, manufacturer family of leads, manufacturer, fixation type (active or passive), polarity, lead diameter, distal coil diameter, lead body diameter, insulation coating, lead construction, steroid elution, number of coils, tip to ring spacing, cathode surface area, anode surface area, helix extension distance, coil treatment overlay, tip to RV coil spacing, tip to SVC coil spacing, RV coil surface area, SVC coil surface area, recalled lead status, number of unfilled lumens, number of compression lumens, number of filled lumens, total number of lumens, cable construction type, cable size, cable insulation size.

Removed from multivariable analysis as a result of co-linearity between variables:

Manufacturer family, distal coil diameter, steroid elution, tip to ring spacing, anode surface area, helix extension distance, coil treatment overlay, tip to RV coil spacing, tip to SVC coil spacing, RV coil surface area, SVC coil surface area, number of unfilled lumens, number of compression lumens, cable size, cable insulation size.

Considered for multivariable model (with P<.25 and after removing co-linear variables):

Age, coronary artery bypass graft surgery, percutaneous coronary intervention, significant conduction disease, AV junction ablation, baseline rhythm (sinus, atrial fibrillation, and/or atrial flutter), significant coronary artery disease, implant approaches (left versus right side), cephalic versus axillary or subclavian venous, multiple leads, lead fixation type (active versus passive), polarity, lead diameter, lead body type, type of insulation coating (silicone versus silicone/polyurethane mixture), type of lead construction, number of coils, recalled lead status, number of filled lumens, total number of lumens, type of cable construction.

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From the Department of Medicine at Winthrop University Hospital, Mineola, New York.

Funding: This study was submitted to each of the manufacturers listed in the manuscript (Medtronic, Boston Scientific, and St. Jude Medical); however, the study was only partially funded by Medtronic and Boston Scientific.

Presented in part at the following meetings: American Heart Association Scientific Sessions 2010 (November 2010), Venice Arrhythmias 2011 (October 2011), Heart Rhythm 2012 (May 2012), The 11th International Dead Sea Symposium on Cardiac Arrhythmias and Device Therapy 2012 (February 2012), and Heart Rhythm 2014 (May 2014).

Disclosure: The authors have completed and returned the ICMJE Form for Disclosure of Potential Conflicts of Interest. The authors report no conflicts of interest regarding the content herein.

Manuscript submitted March 5, 2014, provisional acceptance given May 2, 2014, final version accepted May 8, 2014.

Address for correspondence: Todd J. Cohen, MD, Director of Electrophysiology, Winthrop University Hospital, 120 Mineola Boulevard, Suite 500, Mineola, NY 11501. Email: tcohen@winthrop.org