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Research Papers

Design of an Experimental Test System to Investigate Parameters Affecting Distal Tip Loads of Pacemaker and Defibrillator Leads

[+] Author and Article Information
Elizabeth A. Stephen, Nandini Duraiswamy, Oleg Vesnovsky

U.S. Food and Drug Administration,
Center for Devices and Radiological Health,
10903 New Hampshire Avenue,
Silver Spring, MD 20993

Donna L. Walsh

U.S. Food and Drug Administration,
Center for Devices and Radiological Health,
10903 New Hampshire Avenue,
Silver Spring, MD 20993
e-mail: donna.walsh@fda.hhs.gov

L. D. Timmie Topoleski

U.S. Food and Drug Administration,
Center for Devices and Radiological Health,
10903 New Hampshire Avenue,
Silver Spring, MD 20993
Department of Mechanical Engineering,
University of Maryland–Baltimore County,
1000 Hilltop Circle,
Baltimore, MD 21250

1Corresponding author.

Manuscript received November 6, 2013; final manuscript received September 2, 2014; published online November 14, 2014. Assoc. Editor: John LaDisa.

J. Med. Devices 9(1), 011001 (Mar 01, 2015) (8 pages) Paper No: MED-13-1272; doi: 10.1115/1.4028517 History: Received November 06, 2013; Revised September 02, 2014; Online November 14, 2014

The purpose of this study was to design and evaluate a system to test the mechanical behavior of pacemaker and defibrillator leads. Over 300,000 pacemaker and implantable cardioverter defibrillator (ICD) procedures are performed every year in the U.S. for the treatment of cardiac arrhythmias, ventricular dysrhythmias, and congestive heart failure. These procedures require implanting transvenous leads into the interior wall of the heart. A serious and sometimes fatal complication that may occur during or after lead implantation is perforation of the lead tip through the heart wall. The factors that lead to perforation are not fully understood. This illustrates that the mechanical interactions between the lead tip and the cardiac tissue need to be further investigated to improve the outcome for pacemaker and ICD patients. To improve the performance of lead tips, the testing protocols must reproduce physiological and clinically relevant tip-tissue interactions. As a first step toward this goal, testing parameters that influence those interactions must be identified. We investigated the effect of test system parameters, which reproduce potentially critical physiological constraints, on the load experienced at the distal tip of thirteen pacemaker and defibrillator active-fixation leads. We evaluated the use of a constraint to simulate the effect of the right ventricle (RV constraint) in vivo, how and where the lead was fixed in the test configuration, location of the load cell in the test system, rotation and frequency of the test protocol, and the effect of stylets. Results showed the RV constraint and load cell placement had the largest impact on lead tip load, while rotation of the test setup and test frequency had a minimal impact. Recommendations are made for a test system and protocol for in vitro testing of leads that take into consideration in vivo conditions. Better approximations of the in vivo environment may lead to improved product development. The potential of this system to more effectively evaluate new pacemaker and defibrillator lead designs will require further study.

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References

Figures

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Fig. 1

Schematic of test setup and comparison to reported anatomical values

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Fig. 2

Schematic of test setup showing lead fixation configuration 1—secured at top of SVC/RA tube; configuration 2—secured at top of SVC/RA tube with PTFE disk at bottom of SVC/RA tube; and configuration 3—secured at bottom of SVC/RA tube

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Fig. 3

Test setup for stylet comparison

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Fig. 4

Maximum load values for ICD and pacing leads with and without the RV constraint. There were statistically significant differences in maximum compressive load (p < 0.0001) with RV constraint versus without RV constraint.

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Fig. 5

Lead response (a) without RV constraint (pacing lead shown) and (b) with RV constraint (ICD lead shown). Note that a PTFE RV constraint was used in the actual testing, but a polycarbonate tube is shown here to allow imaging of the lead response.

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Fig. 6

QS loading profiles for (a) ICD leads with RV, (b) pacing leads with RV, (c) ICD leads with no RV, and (d) pacing leads with no RV. Note the difference in y-axis scales for (a) and (b) versus (c) and (d).

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Fig. 7

Influence of lead fixation configuration on peak load values. Lead fixation configurations are: (1) lead secured at top of SVC/RA tube; (2) lead secured at top of SVC/RA tube with PTFE disk at bottom of SVC/RA tube; and (3) lead secured at bottom of SVC/RA tube.

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Fig. 8

Influence of load cell placement on peak load values. The peak load was significantly higher when the load cell was placed below the lead tip versus load cell placement at the top of the SVC/RA tube (p < 0.0001).

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Fig. 9

Sample load profile for dynamic test, 1 Hz, 20 cycles. Maximal displacement distance 25 mm.

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Fig. 10

Peak load values for varying rotation and cycle frequencies. QS = quasi-static. No significant differences in maximum compressive load were observed between the 7 test groups tested (p = 0.497).

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Fig. 11

Maximum load of pacing and defibrillator leads with no stylet, manufacturer supplied stylet, and a single reference stylet. Graph (a) shows average values for all leads by lead type (pacing and ICD leads) and (b) shows individual lead response for each condition to illustrate the differences in peak load for each lead-stylet pair. Defibrillator leads are numbered 1–8 and pacing leads are numbered 9–13. Maximum compressive loads were significantly lower without a stylet than when using either the manufacturer supplied stylet or the reference stylet for both pacing and defibrillator leads (p < 0.0001). Pacing leads showed significantly lower maximum compressive loads than defibrillator leads for each stylet condition tested (p = 0.030 for no stylet, p = 0.0004 for manufacturer supplied stylet, and p = 0.009 for the reference stylet).

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