Functional properties and performance of new and reprocessed coronary angioplasty balloon catheters

Functional Properties and Performance of New and ReprocessedCoronary Angioplasty Balloon Catheters

Mariangela Fedel,1 Francesco Tessarolo,1 Paolo Ferrari,2 Christian Losche,3 Nikou Ghassemieh,3

Giovanni Maria Guarrera,4 and Giandomenico Nollo2,5

1 Department of Materials Engineering and Industrial Technologies, University of Trento, Trento, Italy

2 Department of Physics, University of Trento, Trento, Italy

3 Department of Research and Development, Vanguard AG, Berlin, Germany

4 Department of Care and Rehabilitation, Azienda Provinciale per i Servizi Sanitari, Trento, Italy

5 ITC-irst, Trento, Italy

Received 18 March 2005; revised 19 September 2005; accepted 27 September 2005Published online 27 February 2006 in Wiley InterScience (www.interscience.wiley.com). DOI: 10.1002/jbm.b.30496

Abstract: The need of health costs control has prompted the reuse of devices originallymanufactured for single use only. To assess reprocessing feasibility of disposable medicaldevices, hygienic, technical, and functional aspects must be taken into account in addition toeconomical, ethical, and legal implications. This study aims to characterize coronary angio-plasty catheters and to evaluate performance changes induced by reprocessing. Multipleanalysis including crossing profile, slipperiness, compliance, mechanical, and burst pressuretests were performed at different steps of the protocol on 25 catheters reprocessed up to twotimes. The results highlighted that both use and reprocessing can affect the features ofangioplasty catheters. Mechanical stress caused by clinical inflation and thermal–chemicalstress undergone by polymers during cleaning and sterilization procedures caused partialmodifications of material properties, inducing an overall shrinking effect on balloons. Com-pliance tests reported a maximum variation of 6.2% from nominal values, showing theconformity of reprocessed devices with manufacturers’ original specifications (�10%). Theburst pressure of reprocessed devices was 80% higher than the rated burst pressure certifiedby manufacturers, thus reducing concerns of breakage during reuse. A strict dependence ondevice model in the behavior of catheters was found, especially for balloons crossing profileand slipperiness. Main changes occurred after the first reprocessing cycle, while a secondcleaning and sterilization did not introduce further significant alterations. On the whole, themagnitude of modifications introduced up to two reprocessing cycles did not compromisecatheters performance. © 2006 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater 78B:364–372, 2006

Keywords: single use medical devices; PTCA catheters; reuse; reprocessing; functionalitytests

INTRODUCTION

The rapid development of minimally invasive procedures fordiagnosis and therapy has led to a considerable increase in thecost of medical equipment. Many medical devices, and inparticular devices for interventional cardiology, are nowa-days placed on the market as single use devices (SUDs), but

their reuse is common practice in many developed countriesas a cost saving measure. National and regional directivesabout SUDs reuse have been developed in the USA andCanada by the Food and Drug Administration (FDA)1,2 andby the Conseil d’Evaluation des Technologies de la Sante duQuebec (CETS),3 respectively. On the other side, there is apaucity of European studies on the practicability of repro-cessing procedures4 and the European juridical approach isstill quite heterogeneous. Nowadays, Germany represents theonly European country with specific recommendations by theRobert Koch Institute,5 concerning the requirements for re-processing of medical devices.

Correspondence to: M. Fedel (e-mail: [email protected])Contract grant sponsor: Fondo Unico per la Ricerca 2001, Provincia Autonoma di

Trento (SICC-SIX Project)

© 2006 Wiley Periodicals, Inc.

364

With more than 1 million interventions performed annu-ally worldwide, angioplasty represents one of the most com-mon and successful procedures of minimally invasive cardio-vascular surgery. During percutaneous transluminal coronaryangioplasty (PTCA) a balloon-tipped catheter is inserted intothe vessel clogged by atherosclerosis and inflated to widenthe artery lumen and to restore a proper blood flow to thecardiac muscle. Balloon PTCA catheters represent an exam-ple of medical devices labelled by manufacturers as SUDs,with significant financial burden on health services.6,7 Al-though safeness and effectiveness of reused angioplasty cath-eters are debated,8–12 the practice of their reprocessing isactually of large extent in western countries.13,14 To assurethe safety of restored devices, the conformity to the intendeduse, and the equivalence of performance between new andreprocessed devices, both hygienic and technical require-ments must be satisfied.5,15–17 Possible modifications of cath-eter materials and functional properties that might occurduring decontamination and cleaning with chemical aggres-sive agents or during sterilization must be carefully exam-ined.18 In addition to standardized material and mechanicalinvestigations, specific tests must be carried out to evaluatethe performance of the particular devices considered. In thecase of balloon coronary catheters, crossing profile, ballooncompliance, crossability and burst pressure (BP) are the mostcritical parameters that describe the functional behavior of thedevices.19–21 The assessment of such parameters is thereforemandatory to certify a qualified reprocessing protocol forangioplasty catheters.

This work aims to evaluate the functional properties ofPTCA restored catheters and to compare them with respect tonew device specifications. With this purpose a multifacedanalysis of performance was carried out on new and repro-cessed devices by using specifically developed instrumenta-tion and testing set-up.

MATERIALS AND METHODS

PTCA Catheters

Modern rapid-exchange angioplasty catheters consist of aproximal stainless steel hypotube and a polymeric (poly-amide-urethane/polyethylene) double-lumen distal portion,usually covered with an hydrophilic coating,22 ending with adilating balloon. Compliant and semicompliant polymers areemployed to produce catheters with different specifications,such as balloon size (length and nominal diameter), compli-ance (diameter vs. inflation pressure), and operative pressure.Polymeric guiding catheters and radio-opaque guide-wiresare employed during clinical use to support the advancementof balloons up to the stenosis.

In this study 25 rapid exchange PTCA catheters fromdifferent manufacturers, with variable balloon size (2.0–3.5mm) and balloon length (10–30 mm), have been tested. Ninecatheters (hereafter referred as “new”) were taken from theshelf in sterile original packages and 12 devices were col-lected from the catheterization laboratory of the Departmentof Cardiology at S. Chiara Hospital, Trento, after clinical useon patient (hereafter referred as “used”). As reported in TableI, new and used devices subjected to performance analysiswere grouped according to manufacturer (A–F) and sizefeatures (1–3). Seven catheters were reprocessed once beforedestructive bursting test, while 14 were reprocessed twice. Atotal amount of 56 complete functional testing cycles wascarried out. Furthermore, four new catheters (Adante, BostonScientific, 3.0–30 mm) underwent pseudo-tensile mechanicaltesting.

Reprocessing Protocol

The reprocessing protocol consisted basically of two mainsteps: preconditioning (decontamination and cleaning) andsterilization. Catheters were decontaminated by immersion in

TABLE I. Catheters Tested and Nominal Specifications

Group Article Manufacturer Balloon Material ND (mm) L (mm) NP (atm) RBP (atm)

New cathetersA (n � 4) Amadeus� EuroCOR GmbH NA 3.5 20 6 16B1 (n � 2) Adante™ Boston Scientific NA 3.0 30 6 14B2 (n � 2) Adante™ Boston Scientific NA 2.5 20 6 14C (n � 1) U-Pass™ Cordis J&J Duralyn™a 2.75 10 6 14

Used cathetersD1 (n � 3) Maverick2™ Boston Scientific LEAP�a 2.0 20 6 12D2 (n � 2) Maverick2™ Boston Scientific LEAP�a 2.5 20 6 14E1 (n � 2) AquaT3™ Cordis J&J Duralyn™a 2.0 20 8 14E2 (n � 2) AquaT3™ Cordis J&J Duralyn™a 2.5 20 8 14E3 (n � 1) AquaT3™ Cordis J&J Duralyn™a 3.5 30 8 14F1 (n � 1) Avion Invatec FLEXITEC™ HFa 2.0 20 7(bar) 15(bar)F2 (n � 1) Avion Invatec FLEXITEC™ HFa 2.5 20 7(bar) 17(bar)

Catheters were divided in two main groups, including new products taken from the shelf and products used once on patient. The devices were subgrouped according tomanufacturer (A–F) and balloon size (1–3).

n � number of products tested; ND � nominal diameter; L � balloon length; NP � nominal pressure; RBP � rated burst pressure. NA, not available.a Trade name.

Journal of Biomedical Materials Research Part B: Applied BiomaterialsDOI 10.1002/jbmb

365FUNCTIONAL PROPERTIES OF REPROCESSED PTCA CATHETERS

Perfektan Endo (3% in water, 15 min) and Instru Plus (5% inwater, 15 min) and then cleaned with an automatic machinethat repeatedly flushed catheter lumens and external surfaceswith detergent and disinfectant solutions at 55°C. Specificchemical agents for thermosensitive instruments, effectiveagainst bacteria, fungi, and viruses (including HBV and HIV)were employed. Cleaning was followed by rinsing with pu-rified water, and finally, with sterile water. Catheters weredried by hanging them in an inverted position overnight in aclean room. Balloon lumens were connected to a vacuumpump to facilitate drying and to avoid germ reproduction inresidual moisture or the formation of toxic substances duringsterilization. External surface of the catheters was then wipedwith a gauze soaked in disinfectant solution. Balloons werefinally reshaped with a three-blade folding-machine, coveredwith a plastic cap of suitable dimensions, and double-wrapped in standard sterilization packaging. Because of thecomplex design of the products, the presence of long narrowlumens, and the humidity and thermal sensitivity of poly-meric materials, ethylene oxide (EtO) was adopted as electivetechnique for the sterilization (180 min at 6% EtO concen-tration, 94% CO2, 42°C, 1.7 bar).

Functional Tests

Crossing Profile. Crossing profile, defined as the diame-ter of the smallest aperture that a folded catheter can cross,was measured by means of a laser scan micrometer (ODAC®32xy, Zumbach Electronics). The distal portion of the cath-eter was positioned on a straight, rigid guide-wire while twoperpendicular laser beams scanned the balloon for the wholelength without direct touching. As original crossing profile ofused balloons could not be assayed, this test was performedonly on new devices (groups A–C) before and after repro-cessing. Every device was tested three times and the crossingprofile was calculated as the mean of the maximum valuesregistered during each single measurement.

Slipperiness. The sliding behavior of a PTCA catheterduring clinical intervention is influenced by the interaction ofthe catheter with coronary vessels, guiding catheter andguide-wire. The quantification of the friction forces exertedby balloon catheters was accomplished by means of a specialcoronary-vessel model.23,24 This model, realized in accor-dance with anatomic considerations, simulated the structureof an healthy right coronary vessel with a properly shapedpolyethylene sleeve (1.5 mm internal diameter). The coronaryand associated models of aorta and arteria femoralis wereimmersed in injectable water at 37°C so as to reproducephysiological conditions.

Rapid exchange catheters were mounted on a guide-wire(0.014��, BBraun, Melsungen AG) fixed at the end of theartificial vessel, and inserted in a guiding catheter (7FR JR4100 cm, Vista Brite tip®, Cordis) acting as support track.Balloon catheters were then clamped at their proximal end,advanced for 65 mm into the coronary-vessel model by astepper motor at a constant speed of 8 mm/s, and withdrawn

at the same speed. The system was equipped with forcetransducers positioned in four critical points of the model[Figure 1(a)] to evaluate, respectively, insertion forces (A),support forces on the tip of the guiding catheter (B), wallreaction forces (C), and friction forces exerted on the guide-wire (D). All the sensors integrated in the coronary-modelwere based on strain gauge technology. The four identicalforce transducers employed were designed as flexible alumi-nium beams fitted with wire strain gauges (EA-06–125PC-350, Fa. Measurements group, nominal sensitivity: 2.075mV/V � 0.5%, output resistance: 350 �� 0.2%) made fromconstantan fully clad in polymer [Figure 1(b)]. Each sensorwas temperature-compensated and calibrated separately. Theforce transducers presented a linear behavior in the range0.0–1.4 N, with a maximum linearity error of 2.97% fullscale (FS) in the case of sensor B, a minimum of 0.34% FS(sensor C) and a typical hysteresis of 1.52% FS. Experimentswere pursued in the range 0.0–1.3 N.

A computer was responsible for control of the activecomponents of the system and for data acquisition. Eachcatheter was tested three times in a row in the coronary-vesselmodel, with a rotation of 120° over the guide-wire after everyadvancement. As for the crossing profile, slipperiness wasmeasured only on new catheters (groups A–C), comparingdata before and after reprocessing.

Compliance. The compliance curve (balloon diameter vs.inflating pressure), was measured by a laser scan micrometer(ODAC 32xy, Zumbach Electronics), as used in crossingprofile evaluation.

Operative clinical procedures were taken into account inthe definition of the experimental measurement protocol.Catheters were filled with water by means of an automaticinflator at a constant rate of 0.7 atm/s up to the nominalpressure. According to mean clinical inflation time, nominalpressure was maintained for 15 s; balloons were then deflatedand re-inflated three times consecutively. Figure 2 representsa schematic description of balloons inflating protocol andillustrates the response of materials to consecutive inflations.By holding the nominal pressure, balloons underwent a pro-gressive dilatation and the diameter continued to increase,reaching a plateau in few seconds. Moreover, an expansionbetween the first and subsequent inflations was elicited. Be-cause of this behavior of the polymers, the experimentaldiameter was collected at the third inflation cycle, 7 s after theachievement of nominal pressure, when diameter values weresteady and representative of polymer real expansion.

To validate compliance functional tests and to completethe understaning of materials characteristics, pseudotensiletests have been performed on four new catheters. Short-timecreeping tests, adapted to the specific devices and procedures,have been performed. Balloons were cut into rectangular-shaped samples and clamped to an Instron 4500 testingsystem. Each polymer specimen was loaded at a constantdisplacement rate of 3 mm/min, up to the nominal load

�N �PNDN

2t(PN � nominal pressure, DN � nominal dia-


366 FEDEL ET AL.

meter, t � wall thickness). When the desired level of strainwas reached, the load was held constant for 15 s before thesample was being downloaded. The test was repeated three

times in a row for each balloon (loading cycles 1A–3A).After a resting period of 1 h, the polymer was tested twiceagain (cycles 4B–5B), and the last cycle was prolonged to10 min.

Burst Pressure. Manufacturers provide the rated BP(RBP), defined as the maximum statistically guaranteed pres-sure withstood by 99.9% of an inflated balloon with a 95%confidence level, as pressure operative limit value. To verifythe absence of leakages and the resistance to high pressure,catheters were inflated 10 times up to the RBP. Balloons werethen finally brought to rupture and the BP value was regis-tered as the maximum inflating pressure reached before burst-ing.

Statistical Analysis

To compare products with different features, in particularwith different balloon size and RBP, data collected after oneand two reprocessing cycles were normalized to theoreticalnominal values when reported on the packaging, and tomeasured reference values otherwise. Thus, percent valueswere obtained by assessing the increase or decrease of thephysical quantities with respect to new devices.

Continuous data were presented as the mean � standarddeviation. Continuous variables were analyzed using Kruskal–Wallis and Mann–Whitney U-test. p-values � 0.05 wereconsidered statistically significant.

Figure 1. (a) Simplified representation of the coronary-vessel set-up for the quantification of slipperi-ness of catheters. The geometrical structure of the coronary-vessel model simulated the anatomy ofan healthy right coronary branch. Four sensors were positioned on PTCA catheter drive unit (A),guiding catheter tip (B), bending vessel (C), and guide-wire tip (D) to measure, respectively, the forceexerted during catheter advancement/withdrawal (A), the support force on the tip of the guidingcatheter (B), the reaction force of the coronary-model wall (C), and the friction force on the guide-wire(D). (b) Strain-gauge-based transducer system. All the sensors integrated into the coronary-vesselmodel were designed as flexible aluminium beams fitted with wire strain gauges.

Figure 2. Balloon inflation protocol (lower panel) and typical compli-ance curve (upper panel). Catheters were inflated at 0.7 atm/s up tothe nominal pressure and maintained at this pressure for 15 s. Ex-perimental diameter values were collected at the third inflation cycle,7 s after the achievement of nominal pressure. Accuracy of themeasurements: 0.001 mm.



RESULTS

Crossing Profile

After one reprocessing cycle, catheters showed a mean in-crease in crossing profile of 29% � 18%. Partial deteriorationof balloon folding after reconditioning was assessed, docu-menting higher effects for larger balloons. However, asshown in Table II, the degree of changes was different for thevarious groups of devices tested. On the average, the crossingprofile did not increase significantly further on after thesecond complete cycle of cleaning and sterilization (33% �18% vs. new).

Slipperiness

Figure 3 reports the typical behavior of the force intensitiesregistered by the four different sensors during advancementand withdrawal of the catheter into the coronary-vesselmodel. Insertion force [Figure 3(a)] represents the most im-portant sliding feature, as it characterizes the friction actuallyfelt by the clinician during catheter positioning and could berelated to intervention duration and efficacy.8,13 Each devicepresents a typical slipperiness curve that carries informationabout tip conformation, friction exerted by radio-opaquemarkers, materials stiffness, and flexibility.

The maximum force intensities registered during catheteradvancement into the bending artery-model were extrapo-lated and selected as meaningful parameters. Figure 4 sum-marizes the results and compares data relative to the differentdevice classes (A, B1, B2, and C). The maximum intensity ofthe insertion force required to advance the catheter wasgenerally smaller than 1 N, but different catheter classespresented characteristic values. Changes induced on the slip-periness of catheters by reprocessing procedures were alsostrictly model related. The most significant variations be-tween new and restored devices occurred after the first re-processing cycle, with a decrease of 21% � 4% for the group

TABLE II. Crossing Profile of New and Reprocessed Devices

Group New (mm)

1Reprocessing

(mm)

2Reprocessings

(mm)

A 1.02 � 0.05 1.50 � 0.02* 1.57 � 0.10*B1 0.99 � 0.05 1.02 � 0.01 1.16 � 0.05B2 1.07 � 0.01 1.44 � 0.12 1.37 � 0.01*C 0.94 � 0.01 1.24 � 0.02* 1.25 � 0.01*

*p � 0.05 vs. new balloon (U-test).

Figure 3. Forces exerted during advancement (0–65 mm) and withdrawal (65–130 mm) of the PTCAcatheter in the coronary vessel model: (a) insertion force, (b) support force on the tip of the guidingcatheter, (c) wall reaction force, and (d) friction force exerted on the guide-wire. Black arrows indicatethe maximum values registered by each sensor, which are summarized in Figure 4.


368 FEDEL ET AL.

A, and a variable increase for groups B1, B2, and C, rangingfrom 13 to 32%. After the second reprocessing cycle, therewere no further significant modifications in the maximumfriction measured during catheter insertion.

Support forces exerted on the tip of the guiding catheter,wall reaction forces, and friction forces exerted on the guide-wire presented a similar trend [Figure 3(b–d)], with variabledependence on the class of products tested. Withdrawalforces usually showed the same behavior as that of therelative forces registered during advancement of cathetersand are not reported here for sake of brevity.

Compliance

New devices always presented smaller diameters when com-pared with the nominal values, ranging from –2.3% � 1.6%to –5.2% � 1.0%, while used catheters exhibited eitherincreased or decreased dimensions (�1.5% � 2.8% and–1.3% � 2.3% vs. nominal) (Figure 5). New and used cath-eters followed the same trend during reconditioning. The firstcleaning caused a decrease in balloons diameter and a furtherappreciable shrink was evidenced at the end of the firstcomplete reprocessing cycle. Neither new, nor used balloons

changed their diameter significantly, at nominal pressure,after a second reprocessing cycle, and original specificationlimits were never exceeded.

Figure 4. Comparison among maximum force intensity of new and reprocessed catheters for groupsA, B1, B2, and C. Data were measured during catheter advancement in the coronary-vessel model: (a)insertion force, (b) support force on the tip of the guiding catheter, (c) wall reaction force, (d) frictionforce exerted on the guide-wire. Reprocessing did not seem to univocally affect catheters slidingbehavior, but slipperiness is highly dependent on device classes.

Figure 5. Effects of cleaning and reprocessing on balloon working diameter(D) normalized to nominal specifications (ND). Data refer to new devices (�),and to products used once on patients (Œ). The gap between new andused catheters could be caused by exceeding the nominal pressureduring in vivo inflation of used balloons. Both new and used cathetersunderwent a progressive shrinking after cleaning and first completereprocessing. (Manufacturers declared interval of confidence, �10%.)



Response of the polymers to consecutive loading cycles isdisplayed in Figure 6, where the unloading curves are notreported for clarity. Supporting compliance results, time-dependent mechanical tests evidenced creep effects even atshort loading times. On the average, catheters underwent anelongation of 0.6% � 0.4% after 15 s, at constant nominalload. If maintained under load for longer periods (i.e. cycle5B), polymers continued slowly to expand. Creeping testsshowed similar time-courses for the different catheters tested,with a range of variability related to features of catheters andnominal parameters. As shown in Figure 6b, deformation ofpolymers was linear in the range tested, with a similar mod-

ulus, both at first and subsequent cycles. Stress–strain curvesunderwent a progressive shift, and tended to assume asymp-totic values after multiple loading cycles.

Burst Pressure

Three out of 25 catheters underwent fractures in the Luer-Lock, and could not therefore be tested for BP. The tightnessof these products was compromised either by cracks or leak-ages in the Luer-Lock.

All the other catheters tolerated repeated inflations up tothe RBP without pressure leakages. The mean pressure re-quired to reach bursting for regenerated balloons was alwayslargely above the RBP limits recommended by manufactur-ers. On the average, the BP after one and two reprocessingcycles was, respectively, 81% � 21% and 76% � 32% higherif compared with RBP reference values (Figure 7), andno significant differences between new and used catheterswere registered. PTCA catheters always burst causing longlongitudinal fractures on balloon walls, as previously docu-mented,19,20 but no pinhole ruptures were detected.

DISCUSSION

This study aimed at testing recent models of PTCA catheterscurrently in use in clinical practice. Devices from manymanufacturers and with different nominal specification havebeen selected, thus to consider a wide spectrum of the currentmarket, even though the number of new devices tested waslimited by the cost of the catheters. Because of the shortageof information about technical characteristics of originalproducts and about the exact composition of materials em-ployed, a first analysis of new catheters was undertaken to geta reference baseline for subsequent comparisons with usedand reprocessed devices.

Figure 7. Mean burst pressure (BP) of balloon catheters subjected,respectively, to one and two reprocessing cycles. Data were normal-ized to the rated burst pressure (RBP) values provided by manufac-turers. Reprocessing does not seem to affect bursting pressure, asthe breaking point value did not change significantly from first tosecond cycle and was always markedly higher than the nominal value.

Figure 6. Pseudotensile tests for a 3.0-mm balloon. Polymer sam-ples were loaded at 3 mm/min up to nominal load (i.e. 20 MPa), andthe load was then held constant for 15 s. Three consecutive loadingcycles (1A–3A) were performed, followed by a resting period of 1 h.Specimens were then loaded twice more (cycles 4B–5B) with a load-ing time of 10 min for the final cycle (5B). (a) Each device testedshowed polymers creep within the 15-s loading time. (b) Stress–straincurves evidenced a progressive deformation of balloon materials,partially reabsorbed within 1-h resting time.


370 FEDEL ET AL.

By testing the most crucial functional parameters of PTCAcatheters at different steps of the reprocessing protocol, weevidenced that both use and regeneration process can affectthe behavior of the catheters and introduce functional changesat different degree. On the whole, the functionality of thedevices up to the second reprocessing cycle was howeverpreserved.

Balloons refolding represented one of the most criticalparameters for quality control of reconditioned devices. Oncedeflated, balloons were unlikely to regain the original cross-ing profile. The attempt to lower crossing profile by coveringthe balloon with a plastic cap of proper diameter duringsterilization did not always succeed and it sometimes origi-nated wrinkles in balloon wings. It is worthy to note thathigher crossing profile does not necessarily mean lower cath-eter crossability or increased difficulty in catheter position-ing. As highlighted by the slipperiness measurements per-formed in the coronary-vessel model, no direct correlationseemed to exist between the friction forces registered duringcatheters advancement/withdrawal and the diameter of foldedballoons. On the contrary, catheter sliding features proved tobe highly model related, as also supported by recent studies.19

In our research, force profiles seemed to be affected bymanufacturing characteristics, such as flexibility of the cath-eter shaft, tip conformation, and lubricious properties ofpolymer surfaces, rather than by reprocessing procedures.

Polymeric materials used for manufacturing of balloonspresented the characteristic behavior of thermoplastics. Thecompliance test performed here could be considered a “non-conventional” stress–strain test, as the stress exerted on bal-loon walls during inflation is proportional to the appliedpressure and to balloon diameter. As evidenced by compli-ance tests and confirmed by pseudotensile tests, the polymersexamined showed a deformational response proportional tothe stress applied, both at first and subsequent loadings. Ifmaintained under load, polymers entered a region of nonlin-ear viscoelastic regimen and presented an evident creeping.Tensile tests seemed to show a cumulative effect of repeatedinflations on polymers. A progressive residual strain re-mained in balloons after loading, causing a shift of stress–strain curves at consecutive cycles. This effect may be due toviscoelastic flow and temporary reorganization of polymericchains inside the material and seemed to be almost partiallyreabsorbed within 1 h when the stress applied was in the orderof magnitude of the nominal operative conditions suggestedby catheter manufacturers. Both compliance and mechanicaltests evidenced the tendency of deformation curves to reachlimit values after multiple loading cycles, thus suggesting apossible decrease of balloon ductility. In the case of newcatheters, there was, however, no evidence of polymers pastthe yield point.

The compliance of used catheters showed dependence onthe total strain applied, that is, on the number and duration ofinflations and on the maximum pressure sustained. The needto dilate hard-calcified atherosclerotic plaques during clinicaluse may lead to exceed the nominal pressure, thus causing anoverstretching of the balloon. Cleaning and resterilization

procedures could, on the other side, introduce thermal andchemical stresses on materials,25 affecting balloons diameter.Compliance tests documented an appreciable shrinking ofballoons at the first reprocessing, which did not increasesignificantly after the second cleaning and sterilization.

Several studies reported the effects of EtO on polymericbiomaterials.26 According to some authors, EtO could gener-ate structural modifications by oxidizing polymeric chains.27

Despite this hypothesis, other studies found that repeatedexposure of polyethylene catheters to EtO had no significanteffects on their mechanical strength.28,29 The shrinking ofballoon materials reported in this work could be caused byexceeding the glass transition temperature of polymers duringautomatic cleaning, or by the chemical action of decontami-nation and cleaning agents. EtO sterilization process could, infact, increase the crystallinity of polymers and promote thestiffening of the materials. Nevertheless, it is noteworthy toreport that diameter variations induced by reprocessing neverexceeded the limit of variability given by manufacturers fornew products, usually certified as 10% of the nominal values.On the average, reprocessed catheters showed, in fact, amaximum diameter decrease of 5.2% � 1.0%. By theseconsiderations we underline that compliance tests, if per-formed regularly on each device, can provide more preciseinformation about the functionality of the single product,whether new or reprocessed.

Bursting of both new and used balloons after one or tworeprocessing cycles was achieved at pressure values �80%higher than those of the RBP certified by manufacturers. Thewide gap between experimental and nominal bursting pres-sure seems to assure a large margin of safety. Moreover,bursting pressure is a device-specific feature and does notseem to be affected by multiple reprocessing. The presence ofhard calcified coronary plaques represents a possible cause ofdamage on balloon surface, which however could not betested in vitro.

The leakages in the Luer-Lock that affected 3 out of 25devices underlined the weakness of this part of the catheter,and could be related to the quality of the materials (intendedfor single use only) or to the reprocessing technique. Todetect these failures, as well as kinks or lumen obstructions,and to reject macroscopically damaged catheters, a first in-spection by means of conventional microscopy is fundamen-tal before starting reprocessing procedure.

Further clinical trials are required to relate in vitro and invivo performance of reprocessed catheters and to evaluate thepossibility of clinical complications to take place. The presentstudy for the assessment of PTCA catheters performance was,in fact, completely conducted in vitro, thus providing a po-tential limitation. As reported in some recent clinical studies,there is however little evidence of increased risks related toreprocessing of balloon catheters.8,9 According to some au-thors, reuse strategy is in fact not associated with increasedprocedure time or worsening of other procedural vari-ables.12,13



CONCLUSIONS

This study aimed to assess the performance of PTCA cathe-ters before and after reconditioning. Testing performed dur-ing this trial on angioplasty catheters succeeded in character-izing both new and reprocessed devices and crossing profile,slipperiness, compliance, and BP proved to be relevant pa-rameters to describe functional properties of balloon cathe-ters.

Response of the devices to reprocessing showed to behighly related to the model of catheter tested. This resultsupports the statement that, for a safe reuse, each productshould undergo individual evaluations so as to establish theconformity of the restored device with nominal performance.A reprocessing facility, whether represented by hospital orthird-part reprocessor, should thus hold suitable laboratoriesto validate regeneration procedures and to perform methodi-cally adequate and up-to-date testing and quality controls.

Nevertheless, further clinical trials need to be carried outin order to assess the degree of importance of functionalchanges induced by use and reprocessing, and to establishwhether catheter modifications could negatively affect clini-cal practice in terms of procedure time or adverse clinicalevents.

The authors would like to acknowledge the staff of the Hemo-dynamics Laboratory at the S. Chiara Hospital, Trento, for cathetersretrieval.

REFERENCES

1. Food and Drug Administration Center for Devices and Radio-logical Health. US Department of Health and Human Services.FDA proposed strategy on reuse of single-use devices (updated1 November 1999). Available at http://www.fda.gov/cdrh/comp/guidance/1168.pdf.

2. Food and Drug Administration Center for Devices and Radio-logical Health, US Department of Health and Human Services.Medical device user fee and modernization act of 2002, valida-tion data in premarket notification submissions (510(k)s) forreprocessed single-use medical devices; guidance for industryand FDA staff (issued 1 June 2004). Available at http://www.fda.gov/cdrh/ode/guidance/1216.pdf.

3. Conseil d’Evaluation des Technologies de la Sante du Quebec.The reuse of single-use cardiac catheters: safety, economicalethical and legal issues. Can J Cardiol 1994;10:413–421.

4. Fecht G. Requirements for reprocessing single-use medical de-vices. Zentral Sterilization 1998;6:12–27.

5. Robert Koch Institute and Federal German Institute for MedicalDrugs and Medical Products. Hygienic requirements for pro-cessing of medical devices. Bundesgesundheitsblatt-Gesund-heitsforschung-Gesundheitsschutz 2001;44:1115–1126.

6. Milandri M, Saviotti M. Reuse of single-use catheters: a di-lemma to be clarified. G Ital Cardiol 1994;24:1175–1186.

7. Lesh MD. Cost efficacy modelling of catheter reuse for percu-taneous transluminal coronary angioplasty. J Am Coll Cardiol1996;28:1640–1641.

8. Plante S, Strauss BH, Goulet G, Watson RK, Chisholm RJ.Reuse of balloon catheters for coronary angioplasty: a potentialcost-saving strategy? J Am Coll Cardiol 1994;24:1475–1481.

9. Mak KH, Eisenberg MJ, Plante S, Strauss BH, Arheart KL,Topol EJ. Absence of increased in-hospital complications withreused balloon catheters. Am J Cardiol 1996;78:717–719.

10. Shaw JP, Eisenberg MJ, Azoulay A, Nguyen N. Reuse ofcatheters for percutaneous transluminal coronary angioplasty:effects on procedure time and clinical outcomes. Cathet Car-diovasc Intervent 1999;48:54–60.

11. Bourassa MG. The reuse of single-use balloon angioplastycatheters: is it now legitimate? Am J Cardiol 1996;78:673–674.

12. Burton J, Tymchak W, Dzavik V, Lucas A, Muzyka T, Hogg N,Yim R, Montagne T, Teo K. Randomized controlled trial of reuseof PTCA balloon catheters. Circulation 1995;92(Suppl I):I-661.

13. Zubaid M, Thomas CS, Al-Rashdan I, Hayat N, Habashi A,Abraham MT, Varghese K, Thalib L. A randomized study of thesafety and efficacy of reused angioplasty balloon catheters.Indian Heart J 2001;53:167–171.

14. Browne KF, Maldonaldo R, Telatnik M, Vlietstra RE, Brenner AS.Initial experience with reuse of coronary angioplasty catheters inthe United States. J Am Coll Cardiol 1997;30:1735–1740.

15. Mak KH, Eisenberg MJ, Eccleston DS, Cornhill JF, Topol EJ.Reuse of coronary angioplasty equipment: technical and clinicalissues. Editorial. Am Heart J 1996;131:624–630.

16. Grimandi G, Sellai O, Grimandi F, Crochet D. Risks of reusingcoronary angioplasty catheters: results of an experimental study.Cathet and Cardiovasc Diagn 1996;38:123–130.

17. Krause G, Dziekan G, Daschner FD. Reuse of coronary angio-plasty balloon catheters: yes or no? Eur Heart J 2000;21:185–189.

18. Karov J, Chawla AS, Hinberg I. Effect of reuse on surfacecharacteristics of balloon angioplasty catheters. Art Cells BloodSubs Immob Biotech 2000;28:229–240.

19. Brown SA, Merritt K, Woods TO, Hitchins VM. The effects ofuse and simulated reuse on percutaneous transluminal coronaryangioplasty balloons and catheters. Biomed Intrum Technol2001;35:312–322.

20. Unverdorben M, Quaden R, Werner C, Bloss P, Degenhardt R,Ackermann H, Vallbracht C. Change of the mechanical prop-erties of two different balloon catheters with increasing numbersof cycles of resterilization. Catheter Cardiovasc Interv 2003;58:29–33.

21. Marmieri G, Pettenati M, Cassinelli C, Morra M. Evaluation ofslipperiness of catheter surfaces. J Biomed Mater Res (ApplBiomater) 1996;33:29–33.

22. Park S, Bearinger JP, Lautenschlager EP, Castner DG, HealyKE. Surface modifications of poly(ethylene terephthalate) an-gioplasty balloons with a hydrophilic poly(acrylamide-co-eth-ylene glycol) interpenetrating polymer network coating.J Biomed Mater Res (Appl Biomater) 2000;53:568–576.

23. Kraft M, Schmitz H, Schulte R, Boenick U. Multifunctionaltesting of PTCA catheters. Biomed Tecknik 2000;45:146–153.

24. Kraft M. Entwicklung eines multifuktionalen Prufstandes undDurchfuhrung vergleichender Untersuchungen an Ballonkath-etern zur Dilatation von Koronararterien. Dissertation at theTU-Berlin. Boenick U, editor. Biomedizinische Technik, Fors-chungsberichte fur die Praxis, Bd. 9. Berlin: Schiele und Schon;2000.

25. Granados DL, Jimenez A, Cuadrado TR. Assessment of param-eters associated to the risk of PVC catheter reuse. J BiomedMater Res (Appl Biomater) 2001;58:505–510.

26. Hermanson NJ, Navarrete LY, Crittenden P. The effects of highenergy and EtO sterilization on thermoplastics. Med DeviceDiagn Ind Mag 1997; August:1–9.

27. Zapf S, Thelen M. Possibilities and limitations of preparationfor reusing angiography catheters. Dtsch Med Wochenschr1988;113:1117–1120.

28. Zapf S, Muller K, Haas L. Reuse of angiography catheters. II.Effect of multiple sterilization on the properties of the cathetermaterial—Physiochemical studies. Rontgen-Blatter 1987a;40:154–158.

29. Bentolia P, Jacob R, Roberge F. Effects of reuse on the physicalcharacteristics of angiographic catheters. J Med Eng Technol1990;14:254–259.


372 FEDEL ET AL.

Functional properties and performance of new and reprocessed coronary angioplasty balloon catheters

Documents

Transcript of Functional properties and performance of new and reprocessed coronary angioplasty balloon catheters