Preliminary Reports . . . works in progress

Single Device Approach toUltrasound-Guided PercutaneousTransluminal CoronaryAngioplasty and Stenting:Initial Experience With a CombinedIntracoronary Ultrasound/VariableDiameter Balloon

Christian Mu¨ ller, MD, Axel W. Frey,* MD, PHD,Helmut Roskamm, MD, and John McB. Hodgson, MD

We evaluated the use of both intracoronary ultrasound (ICUS)information and unique balloon characteristics provided by acombined ICUS/variable diameter balloon catheter during coro-nary interventions to achieve the maximal residual lumen usingthe least number of devices. In 47 patients, 64 coronary lesionswere treated with either sequential percutaneous transluminalcoronary angioplasty (PTCA) (n 5 40) or stenting (primary[n 5 17], secondary [n 5 7]). The result after PTCA was judgedsatisfactory if the lumen cross sectional area (by ICUS) in thelesion exceeded 65% of themean reference area. Stent implanta-tion was judged according to revised MUSIC trial criteria. PTCAor stenting was successful in all 64 lesions using 47 combina-tion devices and 10 conventional balloons (mean number ofballoons per lesion: 0.90). PTCA group: diameter stenosisdecreased from 78 6 11 to 23 6 13% following inflation at 10.3 63.0 atm. ICUS lumen area was 4.6 6 1.9 mm2 (proximal refer-ence: 7.4 6 3.3 mm2, distal reference: 5.7 6 1.8 mm2) resultingin a residual area stenosis of 28 6 15%. Stent group: diameterstenosis was reduced from 77 6 14 to 10 6 10% after stenting.ICUS defined minimal lumen area in the stent was 8.2 6 2.2 mm2

(proximal reference: 8.7 6 2.6 mm2, distal reference: 8.0 6 2.2mm2) resulting in a residual area stenosis of 7.2 6 14.6%. Nopatient death, myocardial infarction, or emergency surgeryoccurred and only one target lesion required re-PTCA duringhospitalization. In conclusion, use of a combined ICUS/variablediameter balloon catheter allows a single device strategy forICUS-guided PTCA and stenting in the majority (84%) of unse-lected lesions. Cathet. Cardiovasc. Diagn. 40:393–399, 1997.r 1997 Wiley-Liss, Inc.

Key words: intracoronary ultrasound; PTCA; stenting; athero-sclerosis

INTRODUCTION

For both percutaneous transluminal coronary angio-plasty (PTCA) and coronary stenting, ultrasound guid-ance has been demonstrated to improve acute results [1–5].However, several practical issues have hampered thewidespread application of intracoronary ultrasound (ICUS)guidance for interventions. Typically, multiple exchangeshave been necessary to perform ICUS examinationsduring PTCA. This prolongs the procedure and is techni-cally problematic at times. Therefore, the option of acombination device integrating the ultrasound transducerin the balloon catheter has been attractive. Unfortunately,previous combination catheters [6–8] had limitations andwere never used in a large unselected patient population.This study sought to establish the feasibility of using a

combination imaging/dilatation catheter for pre-, per-,and postinterventional evaluation and to determine thefeasibility of using a single catheter to achieve a mini-mum target level of lumen gain in angioplasty and stentcases by utilizing the device’s special characteristics.

METHODS

Patients

Elective coronary interventions were performed in 47unselected patients with symptomatic coronary arterydisease (Table I). For logistic reasons, cases could not beconsecutive. A total of 64 coronary lesions were treated.Lesion distribution and morphology are described indetail in Table II. Balloon only PTCA procedures wereperformed on 40 lesions; 17 had primary (planned) and 7secondary (bailout) stenting.

Combination Device

The device used for this study (Oracle Focust, Endo-sonics, Pleasanton, CA) combines a 20 mm balloon withan electronic ICUS transducer on a rapid exchangeplatform. The variable diameter balloon has a central 10mm portion which may expand up to 0.7 mm above thenominal size at high pressures. During low pressureinflations (up to 6 atm) the 10 mm central segment has thesame diameter as the proximal and distal ends of theballoon. During high pressure inflations (6–16 atm), thecentral portion expands to a greater diameter than theends (Fig. 1). In vitro, the higher the pressure, the greateris the difference between the central and end portions.The degree of expansion in vivo depends on the lesion

Division of Clinical Research, Herz-Zentrum Bad Krozingen,Germany

*Correspondence to: Axel W. Frey, M.D., Ph.D., Herz-Zentrum BadKrozingen, Su¨dring 15, 79189-Bad Krozingen, Germany.

Received 15 July 1996; Revision accepted 30 October 1996

Catheterization and Cardiovascular Diagnosis 40:393–399 (1997)

r 1997 Wiley-Liss, Inc.

compliance and varies from patient to patient. Theballoon has a rated burst pressure of 12 atm and a meanburst pressure of 18 atm. Crossing profile for the 3.5 mmdevice is 0.035 in.; distal shaft, proximal shaft, andtransducer diameter are 3.0, 3.4, and 3.5 F, respectively.A circumferential array of electronic ultrasound trans-

ducers is arranged on the catheter surface 5 mm proximalto the balloon. The center frequency is 24 MHz and theimage displayed is a continuous 360° tomographic viewof the vessel perpendicular to the catheter shaft. Minoraxial movement of the catheter allows ICUS assessment

of the lesion prior to, between, and after balloon inflationsor stent implantation.

Selection of Balloon Size

Nominal balloon size was visually chosen to match theangiographic reference. While the angiogram gives onlyinformation about the lumen diameter, our aim was to usea balloon sized as the ICUS defined mean of the lumenand total vessel diameter of the smaller of both referencesegments [1]. In only moderately diseased vessels withlittle plaque burden in the reference segment, this size canbe achieved by using nominal (#6 atm) inflation pres-sures. In heavily diseased vessels, this size can beachieved at high (.6 atm) inflation pressures by centralexpansion of the balloon.

PTCA Procedure

Before ultrasound imaging, a low pressure (4 atm)balloon dilatation was performed to restore blood flowaround the catheter and in the distal vessel. Ultrasoundimaging of the lesion as well as the proximal and distalreference was performed by positioning the integratedultrasound transducer (5 mm proximal to the balloon) inthe area of interest. The inflation pressure of the nextdilatation was chosen to achieve the ICUS definedballoon size. The lesion underwent sequential dilatationsuntil the angiogram appeared satisfactory. ICUS imagingof the lesion then was repeated.By predefined criterion, the procedure was judged

complete if the lumen area in the lesion exceeded 65% ofthe mean of the proximal and distal reference lumina.This criterion was chosen based on prior studies indicat-ing that this area can be achieved in the majority of PTCAlesions [1]. When ICUS showed an inadequate lumen,higher pressure dilatations were performed, thus increas-ing balloon size in the central portion of the device. Ifafter this procedure the area in the lesion still did not meetthe 65% criterion, the protocol required the use of a largerballoon or stent implantation at the operator’s discretion.

Secondary Stent Deployment

Secondary stenting was chosen either because ofsevere lesion recoil or National Heart, Lung and BloodInstitute (NHLBI) type D, F, and unstable type C

TABLE I. Baseline Clinical Characteristics of 47 Patients

n (%)

Age (years) 63 (43–76)Male 38 (81)Previous conditionsMyocardial infarction 31 (66)Coronary artery bypass 3 (6)Restenosis 13 (28)

Risk factorsSmoking 22 (47)Hypercholesteremia 40 (85)Diabetes mellitus 11 (23)Family history 5 (11)Hypertension 32 (68)Obesity 21 (45)

No. of vessels diseased1 15 (32)2 17 (36)3 15 (32)

Unstable angina 6 (13)Left ventricular function0 (normal) 16 (34)1 (marginally depressed) 24 (51)2 (moderately depressed) 7 (15)3 (severely depressed) 0 (0)

TABLE II. Distribution and Angiographic Characteristics of 64Lesions Treated in 47 Patients

Artery n (%)

Left anterior descending 12 (19)Diagonal branch 2 (3)Left circumflex 22 (34)Marginal branch 5 (8)Intermediate branch 1 (2)Right coronary artery 21 (33)Saphenous vein graft 1 (2)Lesion typea

A 3 (5)B1 28 (44)B2 26 (41)C 7 (11)

Lesion calcification0 (none/mild) 56 (88)1 (moderate) 5 (8)2 (severe) 3 (5)

Lesion length (mm) 9.686 6.03aModified American Heart Association—American College of Cardiologycriteria [9].

Fig. 1. Combination device: the radioopaque markers (arrows)indicate the proximal and distal ends of the central compliantsegment. The electronic ultrasound transducers (arrowhead)are positioned 5 mm proximal to the balloon.

394 Muller et al.

dissections [10] after attempted PTCA. The stent wasdelivered and implanted with the same combinationballoon already used for PTCA. The procedure wasotherwise the same as described under primary stenting.

Primary Stent Deployment

After the lesion was predilated with low pressure (4atm) inflations, ultrasound imaging of the lesion as wellas the proximal and distal reference was performed. APalmaz-Schatz (Johnson & Johnson Interventional Sys-tems, Warren, NJ) or Pura (DEVON Medical, Hamburg,Germany) stent was manually mounted on the mid-portion of the balloon. Depending on lesion length eithera 7, 8, 14, or 15 mm stent was used. The stent wasimplanted and high pressure inflations were performed.ICUS imaging then was used to assess the proximal anddistal stent-vessel transitions for optimal stent expansion.If the struts were poorly apposed to the arterial wall or amarked lumen difference at the transition was detected,further high pressure inflations were performed until bothangiogram and ICUS revealed an optimal result. Theminimal lumen area (MLA) in the stent was judgedaccording to revised MUSIC trial criteria [4,5,20] (.90%of the mean reference andmore than the smaller referencefor MLA ,9 mm2; .80% of the mean and.90% of thesmaller for MLA $9 mm2). Use of additional largerconventional non-compliant balloons was allowed ifnecessary.

Analysis

Angiography. Quantitative coronary angiography(QCA) was performed using the CAAS II system (PIEMedical, Maastricht, The Netherlands). The guidingcatheter was used as the calibration reference. Measure-ments were made from the frame that best demonstratedthe stenotic site without overlap. The minimal lumendiameter (MLD) at the stenosis and the reference diam-eter were measured prior to intervention, after PTCA,and/or after complete stent deployment. For the referencediameter, the proximal reference was used wheneverpossible and appropriate.The balloons were also analyzed quantitatively. The

central and end portions were measured independently toallow calculation of the degree of variable central expan-sion in vivo.ICUS. Recorded SVHS videotapes were reviewed off-

line and ICUS images of the proximal reference, smallestdiameter in the lesion (or stent), and distal reference weredigitized. Lumen boundaries were defined using standardsoftware (NIH IMAGE 1.57). Minimal and maximaldiameters as well as lumen area were recorded.

Statistics

Data are expressed as mean value6 1 SD. Compari-sons within patient groups were performed using the

paired Student’s t-test. Differences were considered statis-tically significant atP, 0.05.

RESULTS

Procedure

PTCA or stenting was successful (% diameter stenosis,50% without adverse clinical events) in all 64 lesionsusing 47 combination devices and 10 conventional bal-loons. In 6 lesions (9%), a very low profile balloon wasnecessary for predilatation, as the combination cathetercould not pass primarily. In 2 of them (3%), the devicecould not reach the lesion even after predilatation, soPTCAwas completed with the conventional balloon usedfor predilatation. After stenting an additional largerballoon was necessary in 2 lesions (3%). In 2 patientswith multiple lesions (3%), a smaller balloon was neededin addition to the combination device (one for ‘‘kissingballoon technique’’). In 2 patients (4%), the imagingfacility failed after high pressure stent implantation.

PTCAGroup

QCA analysis showed a decrease in percent diameterstenosis from 786 11 pre to 236 13% followinginflation at 10.36 3.0 atm (Table III). The mean diameterof the reference vessel was 2.86 0.6 mm. At lowpressure, the central portion of the balloon was notdifferent in diameter from the ends (QCA:D 5 0.0460.12 mm,P5 not significant [NS]). At high pressures(10.36 3.0 atm), the central portion was selectivelyexpanded (D 5 0.256 0.09 mm,P, 0.0001). By ICUS,the proximal and distal reference lumen areas were 7.463.3 and 5.76 1.8 mm2, respectively. ICUS defined MLAincreased to 4.66 1.9 mm2 (286 15% area stenosis)after higher pressure dilatation. An example of the

TABLE III. QCA and ICUS Data for the PTCAGroup (n 5 41)

Pre-PTCALow

PressureHigh

Pressure

Inflation pressure (atm) 4.06 1.4 10.36 3.0QCAProximal reference (mm) 2.816 0.61 2.766 0.61MLD (mm) 0.636 0.35 2.196 0.54% diameter stenosis 77.66 11.2 23.06 12.5Balloon central portiona

(mm) 2.506 0.30 2.916 0.34*Balloon end portiona (mm) 2.466 0.28 2.666 0.39D central2 enda (mm) 0.046 0.12 0.256 0.09**Balloon/artery ratio 1.016 0.18

ICUSProximal reference (mm2) 7.46 3.3Distal reference (mm2) 5.76 1.8MLA (mm2) 4.66 1.9% area stenosis 28.36 15.0

aBalloon QCAwas performed in the first 16 lesions only.*P, 0.001 vs. low pressure.** P, 0.001 vs. end portion.

Single Device ICUS-Guided Intervention 395

improvement in lumen diameter after PTCA assessed byangiography and ICUS imaging is shown in Figure 2.

Stent Group

QCA analysis showed a decrease in diameter stenosisfrom 77 6 14 prestenting to 106 10% after stenting(Table IV). The diameter of the proximal referencemeasured 3.26 0.6 mm. The mean final dilatationpressure was 14.36 3.6 atm. Even with the stentpositioned on the balloon, the central balloon portionexpanded 0.216 0.16 mm more than the balloon ends(3.046 0.33 mm compared to 2.836 0.31 mm,P, 0.001). By ICUS, the proximal and distal referencelumen areas were 8.76 2.6 and 8.06 2.2 mm2,respectively. ICUS defined MLA in the stent was 8.262.2 mm2 resulting in a residual area stenosis of 7.2614.6% (stent area compared to reference area). Anexample of the improvement in lumen diameter afterstenting assessed by angiography and ICUS imaging isshown in Figure 3.The mean procedure time, defined as the interval from

the doctor entering the catheterization laboratory toprepare the arterial puncture until the catheters areremoved, was 69.06 28 min (range 40–140 min).

DISCUSSION

This study demonstrates the feasibility of a singledevice strategy for ultrasound-guided PTCAand stenting.In the majority (84%) of lesions in an unselected patientpopulation, ICUS imaging pre-, per-, and postinterven-

Fig. 2. PTCA of a proximal right coronary artery stenosis. Theangiograms show the lesion before, after low pressure, andafter high pressure inflations. The arrows indicate the positionof the cross sectional ultrasound images on the angiogram (A:distal reference; B: proximal reference; C: lesion after dilatation

with 5 atm; D: lesion after dilatation with 10 atm). Note the NHLBItype A dissection on the preangiogram and ultrasound image Awhich was produced at an earlier intervention distal to thecurrent lesion. The lumen area in the lesion increased from 3.9mm2 (C) to 7.5 mm 2 (D).

TABLE IV. QCA and ICUS Data for the Stent Group (n 5 23)

Prestent Poststent

Inflation pressure (atm) 14.36 3.6QCAProximal reference (mm) 3.196 0.62 3.196 0.58MLD (mm) 0.716 0.47 2.986 0.67% diameter stenosis 76.96 13.5 10.46 10.1Balloon central portiona (mm) 3.046 0.33Balloon end portiona (mm) 2.836 0.31D central2 enda (mm) 0.216 0.16*Balloon/artery ratio 1.066 0.12

ICUSProximal reference (mm2) 8.76 2.6Distal reference (mm2) 8.06 2.2MLA (mm2) 8.26 2.2% area stenosis 7.26 14.6

aBalloon QCAwas performed in the first 14 lesions only.*P, 0.001.

396 Muller et al.

tional, as well as PTCA or stent implantation wassuccessfully performed with a single combined ICUS/variable diameter balloon catheter. This strategy yieldsexcellent results by QCAand ultrasound analysis withoutmajor adverse cardiac events and with procedure timesthat are very typical for coronary interventions withangiographic guidance alone [11].ICUS provides unique quantitative and qualitative

information about the lesion and the reference segments.Preliminary criteria for selecting the optimal balloon size,based on ICUS measurements and ICUS assessed lesionmorphology, have been developed in recent studies[1,12]. Such criteria may prove helpful in achievingmaximal lumen gain with a minimal risk for acutecomplications. In the CLOUT study [1], the referencesegment plaque burden was used to determine finalballoon size. This approach increased the MLD (ICUS)after PTCA from 1.82 to 2.11 mm.The present trend in the interventional community is to

manage coronary lesions with primary stenting. Themedical and economic implications of this approach areobviously dramatic. In a good number of lesions, how-ever, a ‘‘stent-like’’ result can be achieved by aggressive

PTCA. Only ICUS allows an assessment of the extent ofarterial wall remodeling in the lesion and in the referencesegments. This information is mandatory for an aggres-sive PTCA approach optimizing the MLD in a safemanner. If ‘‘stent-like’’ MLDs can be obtained with thisapproach, with stent comparable restenosis rates, this willclearly have an impact on management decisions, andmore than justify the added cost of the combined device.In the current study, not only the plaque burden in the

reference segment, but also the MLA and the plaqueburden in the lesion influenced the procedure. ICUSMLAand ICUS MLD have been shown to be even morepowerful predictors of restenosis than angiographic MLD[12,13]. If the lesional lumen area did not exceed 65% ofthe mean reference lumen area, further dilatations withhigher pressures were performed. In all but one PTCApatient, we were able to meet this criterion withoutstenting. The criterion for the MLAwas selected based onexperience from the CLOUT pilot trial [1] (mean residualarea5 76% of the reference) and proved a realistic goalin our unselected patient group. We tried to be even moreaggressive in lesions with considerable remodeling andextensive residual plaque area.

Fig. 3. Primary stenting of a proximal left anterior descendingartery lesion. Angiograms show the lesion before (left) and after(right) stenting with a 14 mm Palmaz-Schatz stent. Ultrasoundimages after stenting are shown in positions A (proximal

reference), B (within the stent), and C (distal reference). Thelumen areas are 10.8, 10.5, and 10.0 mm 2, respectively, indicat-ing an acceptable result.

Single Device ICUS-Guided Intervention 397

The residual angiographic stenosis achieved by thisapproach (236 13% by QCA) was significantly less thanthat seen for routine PTCA in prior trials (33% inBENESTENT [14] and 35% in STRESS [15]). Accordingto the ‘‘bigger is better’’ concept [16–18], these patientsshould have a favorable prognosis as well as a low rate ofangiographic and clinical restenosis.Incorporating ICUS findings in our PTCA strategy is

one contributor for these excellent results. An additionalpoint is the unique balloon design of the FOCUS catheter.The length of most coronary lesions undergoing interven-tion is less than 10 mm [14,15]. In our study, the meanlesion length was 9.686 6.03 mm. Locating the pressureof balloon dilatation in a focal 10 mm central areaprotects the reference segments from excessive force andmay help avoid acute complications (dissection, vesselrupture). At the same time, plaque deformation in thelesion can be maximized during high pressure dilatations.QCA demonstrates a significant difference in balloondiameter (central segment minus end segments) duringboth PTCA (Table III) and stenting (Table IV). Theadvantage of this balloon design has recently beendescribed for stenting [19].To limit subacute stent thrombosis, it is generally

accepted that it is important to avoid inflow or outflowobstruction. Therefore, in our stent group, we paid greatattention to the stent-vessel transition regions. The re-sidual percent diameter stenosis in our stented lesions(106 10% by QCA) is similar to values recently re-ported for stent deployment with high pressure dilatations[20–22]. It is, however, somewhat higher than thatpublished by investigators following a more aggressivestrategy using oversized balloons [4]. Oversized balloonsmay lead to acute complications (including vessel rup-ture) in an unacceptable number of patients, but mayprovide additional benefit to those patients who do nothave adverse events immediately after the procedure.ICUS imaging may help define a strategy to achievemaximal lumen gain while minimizing risk of acutevessel closure, dissection, or rupture. However, inflationpressures and ICUS criteria that result in the best short-and long-term outcome after stent implantation have yetto be defined. The disparity between the relative highangiographic residual stenosis (106 10%) and the favor-able residual area stenosis by ICUS (76 15%) is mainlydue to the selection of different references. For QCAanalysis, the proximal reference segment was used when-ever possible. For ICUS analysis, however, the residuallumen area was calculated relative to the mean of bothproximal and distal lumen areas.The use of a combined imaging balloon catheter for

coronary stenting was first described by Mudra et al. [8].PTCA had been performed with conventional balloons inover 50% of their patients. In addition, in 6 of 16 patients

a second combination catheter was necessary to completethe procedure. In order to preserve the major advantage ofa combination device—the avoidance of catheter changesfor IVUS imaging—a single device strategy is necessary.As the selection of a combination device is necessarilyalways according to angiographic information, only avariable diameter balloon allows the operator to respondto ultrasound findings and change balloon size withoutusing a second balloon. In the protocol used for this study,the operator adapted the inflation pressure so that theresulting central balloon size matched ultrasound-derivedcalculations. With this strategy, in only 2 lesions (3%)was a catheter exchange necessary due to balloon size.In this study, a very low profile balloon was necessary

for predilatation in 6 lesions (9%), as the combinationcatheter could not pass primarily. These vessels weretortuous and often heavily calcified. This problem wasnoted predominantly in the circumflex artery (4 of 6).Further improvements in the balloon profile may decreasethe incidence of failure to reach or cross the lesion.Although the combination device is currently more

expensive than a conventional balloon catheter, the costsof ICUS-guided interventions may be significantly re-duced with a single device strategy. Such a strategy notonly eliminates the need for additional balloon catheters,but provides additional information without increasingtime in the catheterization laboratory. The mean proce-dure time in our institution for standard PTCA was 73638 min for 125 consecutive patients; Bonzel et al. [11]reported 666 27 min in a series of 832 patients. Themean procedure time in this study was 69 min (range40–140 min).

Limitations

Although this study demonstrates the feasibility of apotentially cost-limiting single device strategy, we cannotassess cost-effectiveness. Cost-effectiveness can only beestablished in a randomized prospective trial comparingthe combination device to conventional balloons. How-ever, as our patients represent an unselected series ofelective PTCA patients in a large tertiary care referralcenter, we believe the lesions treated with the strategydescribed in this report are typical. ICUS, even whenpresent as part of a combination catheter, is an expensivetechnique. Despite the fewer number of balloons neededto complete the procedure, it is likely that additionalsavings during follow-up (i.e., lower restenosis rate,fewer clinical events) will be needed to compensate forthe primary expense.

CONCLUSIONS

A strategy using a combined ICUS/variable diameterballoon catheter allows a single device procedure with

398 Muller et al.

excellent angiographic and ICUS results in the majorityof an unselected patient population undergoing PTCA orstenting. By reducing the number of balloons needed tocomplete the procedure and ensuring maximal lumengain, such a strategy could prove to be cost-effective.Follow-up studies will be required to show whetherincorporating ICUS information in the decision makingprocess during interventions benefits the patient in thelong term.

ACKNOWLEDGMENTS

We thank Drs. A. Bu¨ttner, K. Werner, H.P. Bestehorn,N. Jander, V. Bassignana, M. Dambacher, A. Grove, E.Langer, MTRA, and H. Sheehan, RN, who assisted inperforming patient studies, as well as I. Rietdorf and U.Poppenburg for QCAanalysis.

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