the II was unable to be weanedfiom PCB. Statistical comparisons were done using the SAS (version 6) sta- tistical package.

Reji-actory cardiovascular collapse was defined as the inability to maintain a systolic blood pressure MO mm Hg with signs of hypoperfusion (decreased menta- tion, respiratory arrest, cardiac arrhythmia, clammy skin). This occurred despite the use of high-dose pres- sor agents, aggressive volume repletion and often me- chanical support, including intraaortic balloon pumps (4 patients), and usually requiring cardiopulmonary re- suscitation. The mean time ji-om such collapse to insti- tution of PCB was 13.1 minutes (9.4 minutes in survivors and 16.3 minutes in nonsurvivors, p ~0.035). The time interval from the initial intentention for hemodynamic instability (initiation of pressers, volume repletion or mechanical support) to initiation of PCB was 41 min- utes (29.8 minutes in survivors and 50.7 minutes in non- survivors p ~0.055). Among the survivors, 2 of 5 re- ceived intraaortic balloon pumping before PCB, compared with 2 of 6 of the nonsurvivors. Pressor agents were used in 10 of 11 patients. Thus, these interventions were not clearly related to patient outcome. There was no relation between these interventions and time delay to PCB. All nonsurvivors died within 48 hours of low- cardiac output.

The mortality rate from cardiac catheterization pro- cedures, although relatively low, can thus be decreased.

The benefit is greatest if hemodynamic collapse is rec- ognized early and PCB is promptly begun. Appreciation of this option may allow physicians to begin to mobi- lize the necessary support personnel at the earliest pos- sible time if hemodynamic instability develops in the catheterization laboratory. Because even small differ- ences in time to bypass may be important for survival, patients in the cardiac catheterization laboratory may be ideal candidates for this approach to refractory hemo- dynamic collapse.

In summary, PCB is an effective “salvage” tool for patients with refractory hemodynamic collapse who otherwise would have died on the catheteriza- tion table, but must be initiated promptly.

i. Mooney MR. Arom KV, Joyce LD, Mooney JF, Goldenberg IF, Van Rucden TJ, Emery RW. Emergency cardiopulmonary support in patients with cardiac ar- rest. J Thorac Cardiovaw Surg 1991;101:45&454. 2. Overlie PA. Emergency use of portable cardiopulmonary bypass. Cother Car- diovasc Diqn 1990;20:27-3 1. j. Phillips SJ, Zeff RH, Kongtabwom C, Skinner JR, Toon RS, Grignon A, Ken- nedy M, Wickemeyer W, Iannone LA. Percutaneous cardiopulmonary bypass: ap- plication and indication for use. Ann Thorac Surg 1989;47:121-123. 4. Reichman RT, Joyo CI, Dcmbitsky WP, Griftitb LD, Adamson RM, Daily PO, Overlie PA, Smith SC, J&i BE. Improved patient survival after cardiac arrest us- ing a cardiopulmonary support system. Ann Thorac Surg 1990;49:101-105. 1. Shawl FA, Domanski MJ, Wish MH, Davis M, Pnnja S, Hemandez TJ. Emer- gency cardiopulmonary bypass support in patients with cardiac arrest in tbe catheter- ization laboratory. Cathe? Cordiovmc Diagn 1990;19:8-12. 6. Rees MR, Bmwne T, Sivanatban UM, Wbittaker S, Hick D, Verma SP, Tan LB, Davies GA. Cardiac resuscitation with percutaneous cardiopulmonary support. Lmcet 1992;340:513-514.

Absence of Movement of Coronary Stents After Placement in a Magnetic Resonance Imaging Field Neal A. Scott, MD, PhD, and Roderic I. Pettigrew, MD, PhD

C oronary stenting is an effective therapy for the treat- ment of acute occlusion during percutaneous trans-

luminal coronary angioplasty.’ In selected cases, stent- ing may also decrease the incidence of restenosis.2 These devices, fuxt implanted in humans in 1987,3 are now

From the Andreas Gruentzig Cardiovascular Center and the Depart- ment of Radiology, Emory University Hospital, Suite F-606, 1364 Clifton Road, Atlanta, Georgia 30322. Dr. Scott is a fellow of the Robert Wood Johnson Foundation for Minority Faculty Development, Princeton, New Jersey. Manuscript received June 18, 1993; revised manuscript received August 25, 1993, and accepted August 30.

widely available. Coronary stents are typically made from stainless steel or tantal~m.4*~ Because they are ir- retrievable after implantation into the artery, they become endothelialized and incorporated into the vessel wa11.6 Magnetic resonance imaging (MRI) has become an im- portant tool in the imaging of many internal organs in- cluding the heart. 7~8 Recently, cardiac Ml31 has also been shown to provide accurate images of the coronary ar- teries.9 Because of the very strong magnetic fields re- quired by current imaging systems (up to 1.5 Tesla), there has been concern regarding the possible dislodgment of previously implanted coronary stents in patients who un-

TABLE I Movement of Coronary Stents in a Magnetic Field

Weight Deflection Rotation Vendor Stent Name Metal (g) (degrees) (degrees)

Cook Inc. Gianturco-Roubin Stainless steel 0.225 0 0 (304)

Johnson + Johnson Palmaz-Schatz Stainless steel 0.176 0 0 Interventional (316L) Systems

Boston Scientific Corp. Strecker Tantalum 0.230 0 0 Medtronic Inc. Wiktor Tantalum 0.238 0 0 Cordis Corp. Cordis Tantalum 0.495 0 0 Ethicon, Inc. 6-O Suture Stainless steel 0.0064 78 90

Needle (proprietary alloy)

900 THE AMERICAN JOURNAL OF CARDIOLOGY VOLUME 73 MAY 1,1994

dergo MRI. This study was performed to quantify the movement of coronary stents within the field of a mag- net often used in MRI studies.

Coronary stems (4.0 mm expanded diameter) were obtained from several stent manufacturers: Johnson & Johnson Interventional Systems (Warren, New Jersey), Cook Inc. (Bloomington, Indiana), Cordis Corp. (Miami Lakes, Florida), Medtronic Inc. (San Diego, California), and Boston Scientific Corp. (Watertown, Massachusetts). All stents were expanded to their nominal diameter with a 4.0 mm percutaneous transluminal coronary angio- plasty balloon. A IO-cm length of 6-O polypropylene su- ture material was tied to the longitudinal midportion of each stent. The stent was then vertically suspended by the suture material at the entrance of the bore of a Philips 1.5 Tesla MRI magnet (Best, the Netherlands). The dej¶ection of the stentfiom the vertical into the mag- netic field was measured with a protractor. The align- ment of the longitudinal axis of the stent was also recorded. As a control, a stainless steel suture needle (Ethicon, Inc., Somerville, New Jersey) was suspended from a IO-cm length of 6-O polypropylene suture mate- rial and similarly placed into the magnetic field.

There was no signt$cant dejlection of any of the stents into the magnetic field (Table I). In addition, there was no evidence of alignment of the stent along its longitu- dinal axis with the magneticJield. The needle used as a control deflected approximately 78” into the magnetic field and aligned its longitudinal axis along the longitu- dinal direction of the magnetic field.

These results demonstrate that coronary stents are not significantly influenced by the magnetic fields that are used for imaging in clinical MRI systems. A possible explanation for these findings is the rela- tively low ferromagnetic nature of the metals used for manufacturing coronary stents. We would there- fore expect that routine MRI of patients with coro- nary or saphenous vein graft stents should not cause significant motion of the prostheses.

1. Roubin GS, Cannon AD, Agrawal SK, Macander PJ. Dean LS, Baxley WA, Breland J. Intracoronary stating for acute and threatened acute closure complicat- ing percutaneous transluminal coronary angioplasty. Circulation 1992;83:91&927. 2. Carrozza JP, Kuntz RE, Levine MI, Pomerantz RM, Fishman RF, Mansour M, Gibson CM, Senerchia CC, Diver DJ, Satian RD, Bairn DS. Angiographic and clin- ical outcome of intracoronary stenting: immediate and long-tam results from a large single-center experience. .I Am Co/l Cardiol 1992;20:328-337. S. Sigwat U, Poe1 J, Mirkovitch V, Joffre F, Kappenberger L. Intravascular stents to prevent occlusion and restenosis after transluminal angioplasty. N En.@ .I Med 1987;316:701-706.

4. Scott NA, King SB III. Coronary stems. Coronary Artery Dis 1992;3:901-907. 5. Palmaz JC. Intravascular stems: Tissue-stat interactions and design considera- tions. AJR 1993;160:613418. 6. Roubin GS, Robinson KA, King SB 111, Giantorco C, Black Al, Brown JE, Siegel RJ, Douglas JS. Early and late results of intracoronary aterial stating af- ter coronary angioplasty in dogs. Circuhzion 1987;76:891-897. 7. P&grew RI. Dynamic magnetic resonance imaging in acquired heart disease. Semin Ultrasound CT MR 1991;12:61-91. 8. Nienaber CA, van Kodolitsch Y, Nicolas V, Siglow V, Piepho A, Brockoff C, Koschyk DH, Spielmann RP. The diagnosis of thoracic aortic dissection by non- invasive imaging procedures. N EngI J Med 1993;328: l-9. 9. Manning WJ, Edelman RR. A preliminary report comparing magnetic resonance coronary angiography with conventional angiography. N En& J Med 1993;328: 828-832.

Resutts of Coronary Stenting uf Ostial Lesions Patrizio Zampieri, MD, Antonio Colombo, MD, Yaron Almagor, MD, Luigi Maiello, MD, and Leo Finci, MD

0 stial stenosis is an unusual manifestation of coro- nary atherosclerosis, occurring in 13 patients

(0.25%) with angiographically defined disease.‘T2 The management of symptomatic patients with this type of coronary artery disease leaves a choice between percu- taneous transluminal coronary angioplasty (PTCA) and bypass surgery for myocardial revascularization. The published results with PTCA of ostial lesions are not very encouraging when compared with PTCA of nonos- tial coronary stenosis, showing a lower procedural suc- cess rate and higher complication and restenosis rates.3-7 Recently, several new technologies for coronary inter- vention have been introduced with the intention of im- proving acute success rate and decreasing the restenosis rate.8-13 The present study was undertaken to define and evaluate the role of balloon-expandable Palmaz-Schatz stents in the treatment of coronary ostial stenosis.

Between December 1990 and September 1992,1,871 patients underwent PTCA at our institution. In 31 pa- tients (1.6%) there was signigcant atherosclerotic dis- ease involving the ostium of a coronary artery, a venous bypass graft or an internal mammary artery conduit. A

From Centro Cuore Columbus, Via Buonarroti 48,20145 Milano, Italy. Manuscript received April 27, 1993; revised manuscript received Au- gust 9, 1993, and accepted August 10.

significant ostial lesion was defined as a stenosis of >50% involving the ostium of a coronary or a mammary artery or a venous bypass graft within 0.3 cm from the orifice of the aorta. Ostial lesions of the left anterior de- scending and left circumjlex arteries were not consid- ered; all patients underwent coronary angioplasty on an elective basis. No patient had previous aortic valve re- placement, syphilitic cardiovascular disease or Takayasu’s arteritis, conditions that have been associated with coro- nary artery ostial stenosis.4 Objective evidence of my- ocardial ischemia by either exercise treadmill testing or clinical unstable angina was present in all patients. Thir- teen of the initial 31 patients were considered suitable for stent insertion. Patients with a contraindication to aggressive anticoagulant therapy or with an artery di- ameter of c3.0 mm were not considered suitablefor stent placement and were treated with other methods. Table I summarizes relevant data of the 13 patients who had elective stent implantation. In 4 patients a multivessel PTCA was attempted during the same session.

The following angiographic data were analyzed: lo- cation of all significant coronary artery stenosis, quan- titative lesion measurement and lesion morphology. Quantitative lesion measurement was pe$ormed using an electronic caliper in 2 orthogonal views. The mini- mal luminal diameter of each treated lesion was mea-

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