- Email: [email protected]
Non-elective intra-coronary stenting: are the clinical outcomes comparable to elective stenting at 6 months?
International Journal of Cardiology 71 (1999) 121–127 www.elsevier.com / locate / ijcard
Non-elective intra-coronary stenting: are the clinical outcomes comparable to elective stenting at 6 months? Foaud R. Amin MBBCh, MSc*, Mohammed Yousufuddin MBBS, MSc, MRCP, MRCPI, Rod Stables MD, MRCP, Arvinder S. Kurbaan MRCP, Jonathan Clague MD, MRCP, Andrew J.S. Coats DM, FRACP, FACC, Ulrich Sigwart MD, FRCP, FESC, FACC Division of Cardiology, National Heart and Lung Institute, Imperial College, Royal Brompton and Harefield Hospitals, Sydney Street, London SW3 6 NP, UK Received 22 March 1999; received in revised form 7 July 1999; accepted 9 July 1999
Abstract The aim of this study was to compare prospectively the clinical outcome of patients treated with intra-coronary stents as a non-elective / bailout procedure for acute or threatened vessel closure, with those undergoing elective stenting at 6 months. Sixty-four patients (60.2611.7 y) who underwent non-elective stenting for abrupt or threatened vessel closure and / or sub-optimal results were prospectively compared with 68 patients (62610.0 y) who were stented electively. All patients had broadly similar pre-procedural clinical profiles. However, patients in the elective group had a higher incidence of previous PTCA (10.2% vs. 0%, P 5 0.01) and bypass surgery (30.9% vs. 6.3%, P 5 0.0003) compared with the non-elective group. A total of 158 stents (1.19 per patient) were implanted in 132 patients with a procedural success rate of 99.3%. At 6 months follow-up there was no statistical difference in the primary composite end-point of death, myocardial infarction and the need of repeat revascularisation (10.9% vs. 5.8%, P 5 0.35) between the two groups. However, patients in the non-elective group showed a higher incidence of unstable angina compared with the elective group (25% vs. 1.4%, P 5 0.0004). The findings of this study suggest that stents (single or multiple) can be effectively implanted in non-elective situations with no increase in the incidence of death, non-fatal myocardial infarction, and the need of repeat revascularisation at 6 months compared with elective stenting. 1999 Elsevier Science Ireland Ltd. All rights reserved. Keywords: Coronary angioplasty; Elective stent; Non-elective stent; Abrupt occlusion; Sub-optimal results
1. Introduction Percutaneous transluminal coronary angioplasty (PTCA) is widely used in contemporary clinical practice to treat patients with coronary artery disease. Threatened or established abrupt coronary artery occlusion (4–8%) and re-stenosis (30–50%) remain the major limitations of PTCA [1–3]. Abrupt vessel *Corresponding author. Tel.: 144-171-352-8121; fax: 144-171-351861. E-mail address: [email protected] (F.R. Amin)
closure after PTCA may result in major clinical events of death, myocardial infarction, and the requirement for emergency bypass surgery. Patients who were treated with elective stents showed improved angiographic and clinical outcomes compared with those treated with PTCA [4]. Intra-coronary stents have revolutionised the treatment of acute complications associated with standard PTCA with a significant decrease in mortality, incidence of nonfatal myocardial infarction and the need of emergency bypass surgery. There are no prospective studies examining the clinical outcome of elective
0167-5273 / 99 / $ – see front matter 1999 Elsevier Science Ireland Ltd. All rights reserved. PII: S0167-5273( 99 )00124-2
122
F.R. Amin et al. / International Journal of Cardiology 71 (1999) 121 – 127
stenting in comparison with non-elective stenting. In view of the remarkable progress in the operator’s experience, stent technology and the use of ticlopidine, we believe that the results of elective and non-elective stenting are likely to be similar. The aim of this prospective study was to compare the outcomes of patients treated with intra-coronary stenting as a planned, elective procedure with those receiving stents non-electively for abrupt or threatened closure and / or sub-optimal results, following PTCA
2. Methods
2.1. Patient population The study population consisted of a consecutive series of patients with native coronary artery or saphenous vein bypass graft disease who were treated by intra-coronary stenting over a 6 month period in our institution. Patients with restenotic lesions following standard PTCA, selected primary saphenous vein graft and native coronary artery lesions were considered for elective stenting following case conferences involving three or more experienced interventional cardiologists. Patients who developed complications including abrupt or threatened vessel closure and / or sub-optimal results (post-procedural residual diameter stenosis of .25% after PTCA) were included in the non-elective group. Of a total of 132 patients, 68 underwent elective stenting and the remaining 64 underwent non-elective stenting. All patients had either unstable angina or limiting stable symptoms with objective evidence of reversible myocardial ischaemia. Patients with a history of hypersensitivity to aspirin or ticlopidine, contraindication to anticoagulation, recent myocardial infarction or significant left ventricular dysfunction (,35% EF) were excluded. The angiographic exclusion criteria included: target vessel diameter ,2.5 mm, severe proximal tortuosity and diffuse distal disease with poor runoff. The study was approved by the Ethics Committee of the Royal Brompton Hospital and National Heart and Lung Institute. Patient characteristics are summarised in Table 1.
Table 1 Patient characteristics a Non-elective
Elective
P
Number of patients Age (years) Males
64 60.2611.7 47 (73.4%)
68 62.8610.0 51 (75.6%)
NS NS
Risk factors Hypertension Positive family history Diabetes mellitus Hypercholesterolaemia Cigarette smoking
22 27 15 39 33
(34.4%) (42.5%) (23.4%) (60.9%) (51.6%)
16 (23.5%) 26 (38.2%) 14 (20.6%) 33 (48.5%) 24 (35.3%)
NS NS NS NS NS
Angina ( CCS class) Class 1 Class 2 Class 3 Class 4
3 16 23 22
(4.7%) (25.0%) (35.6%) (34.4%)
3 (4.4) 16 (23.5%) 26 (38.2%) 24 (35.3%)
NS NS NS NS
Previous myocardial infarction Restenosis lesion Previous bypass surgery
36 (56.3%) 0 4 (6.3%)
24 (39.7%) 7 (10.3%) 21 (30.9%)
NS 0.01 0.0003
Angiographic variables Location of the lesion LMS LAD RCA LCX SVG
0 30 (46.9%) 21 (32.8%) 13 (20.3%) 0
1 (1.5%) 21 (30.9%) 17 (25.0%) 15 (22.1) 14 (20.6%)
NS NS NS NS 0.001
AHA /ACC class A B1 B2 C
13 19 28 4
(23.3%) (29.7%) (43.8%) (6.3%)
22 (32.5%) 25 (36.8%) 14 (20.6%) 7 (10.3%)
NS NS NS NS
Single vessel disease Double vessel disease Multi vessel disease Reference vessel diameter MLD (mm) Percentage stenosis
17 (26.6%) 25 (39.1%) 22 (34.4%) 3.460.7 1.160.3 66.2610.7
25 (22.1%) 24 (35.3%) 29 (42.6%) 3.760.8 1.460.4 68.7610.7
NS NS NS NS NS NS
a CCS, Canadian Cardiovascular Society; LMS, left main stem; LAD, left anterior descending; RCA, right coronary artery; LCX, left circumflex; SVG, saphenous vein graft; AHA /ACC, Class American Heart Association /American College of Cardiology; MLD, minimal lumen diameter.
2.2. Objectives 2.2.1. Primary end-points Composite of death, non-fatal myocardial infarction, and the need of repeat revascularisation as indicated clinically at 6 months. 2.2.2. Secondary end-points Procedural success rate, vascular complications,
F.R. Amin et al. / International Journal of Cardiology 71 (1999) 121 – 127
recurrence of angina and exercise-induced myocardial ischaemia at 6 months.
2.3. Angiographic assessment Angiographic characteristics were assessed using a computerised quantitative coronary angiographic analysis system (Digitron 3 VACI, Siemens). The angiographic view demonstrating maximum stenosis was used to assess the severity of the lesion. The reference vessel diameter, percentage stenosis, and the minimal luminal diameters were measured before and immediately after the procedure. The degree of tortuousity of the vessel in relation to the obstructive lesion was classified as mild (,458), moderate (45– 908) and severe (.908). The lesions were classified as A, B 1 , B 2 , or C according to the modified American Heart Association /American College of Cardiology scheme. Anterograde flow was assessed using the Thrombolysis in Myocardial Infarction (TIMI) Study flow grade [5] and dissection was classified as either ‘simple’ or ‘complex’.
123
lesions (10.2%) were considered for elective stenting. The remaining 69.3% of patients in the elective group had specific coronary abnormalities where intra-coronary stenting was believed to be superior to PTCA. A mean pressure of 1262.32 atm was applied to implant the stents in both groups. In the non-elective group 7.8 and 29.7% of patients had bailout stents for abrupt closure and dissection, respectively. The remaining 62.5% of this group had intra-coronary stents placed for sub-optimal results. All patients had been on aspirin prior to the procedure. Ticlopidine was commenced a day prior to the procedure in the elective group and after the deployment of the stent in the non-elective group. A 10,000 unit intravenous bolus of unfractionated heparin was administered shortly before the intervention and additional boluses (5000–10,000) were given to maintain an activated clotting time (ACT) of .300 s throughout the procedure. No further heparin was administered after the completion of the interventional procedure. However, aspirin and ticlopidine were continued, the former indefinitely and the latter for 3 weeks.
2.4. Interventional procedure 2.5. Follow-up 2.4.1. Percutaneous transluminal coronary angioplasty Balloon angioplasty was performed using standard techniques via the femoral approach using an 8 French guiding catheter. The mean inflation pressure used to dilate the lesion was 4.7166.10 atm. Multiple inflations with a balloon-to-vessel ratio of 1.1:1 were used before classifying the results as sub-optimal. The development of peri-procedural dissection, intraluminal thrombus, complete or partial coronary obstructions was assessed by computerised quantitative coronary angiographic analysis, clinical and electrocardiographic criteria. 2.4.2. Stent placement Although nine different types of stents were used in this study, the most commonly used was the ACS Multi-Link stent (Guidant /Advanced Cardiovascular System Inc.). Patients with saphenous vein graft disease (20.5%) and patients with previous restenotic
Patients were screened for the development of primary and secondary end-points at 6 months. Patients with recurrent unstable angina following interventional procedure were promptly reassessed by coronary angiography. All the remaining patients with stable symptoms had exercise ECG or Thallium scan and were referred for repeat coronary angiograms when positive.
2.6. Statistical analysis The results are expressed as mean6standard deviation (SD). Two-tailed Fisher’s exact test was used to compare the primary and secondary end-points between elective and non-elective groups. The results were considered to be statistically significant when P , 0.05. The Statistical Program for Social Science (SPSS) for Microsoft Windows was used to analyse the data.
F.R. Amin et al. / International Journal of Cardiology 71 (1999) 121 – 127
124
3. Results The risk factor profile, angina class and angiographic characteristics were broadly similar in both groups. However, patients considered for elective stenting had a higher incidence of prior PTCA (10.2% vs. 0%, P 5 0.01) and bypass surgery (30.9% vs. 6.3%, P 5 0.0003) compared with those in the non-elective group. A total of 158 stents (84 in the elective and 74 in the non-elective group) were implanted in 132 patients (1.19 stents per patient) with a procedural success rate of 99.3%. Only one patient in the elective group required emergency CABG. Three patients in the elective group and one patient in the non-elective group required DC cardioversion for ventricular fibrillation during the procedure
3.1. Angiographic results ( Table 2) After stent implantation the mean minimal luminal diameter (MLD) was increased from 1.1660.39 to 3.1560.77 mm in the non-elective group and from 1.4360.49 to 3.3860.72 mm in the elective group. There was no statistically significant difference in the luminal gain (89% vs. 85%, P 5 0.65) between the two groups.
3.2. Primary end-points ( Fig. 1) There were two deaths (3.3%) in the non-elective group (one in hospital and one out of hospital) and one out-of-hospital death (1.6%) in the elective group. The cause of death of the patient in the elective group was non-Hodgkin’s lymphoma. There was one out-of-hospital non-fatal myocardial infarction in the non-elective group and none in the elective group. In the non-elective group three patients subsequently required surgical revascularisation and one Table 2 Angiographic results Variable Reference vessel Diameter MLD a Residual stenosis a
Non-elective (n 5 64) 3.461.0 3.160.7 7.3612.5%
MLD, minimal lumen diameter.
Elective (n 5 68) 3.660.7 3.360.7 9.8610.6%
P
0.89 0.88 0.75
Fig. 1. Incidence of primary composite end-points in the elective and non-elective groups.
patient underwent repeat PTCA. In the elective group one patient underwent emergency CABG and two patients underwent repeat PTCA within 6 months.
3.3. Secondary end-points ( Table 3) The overall procedural success rate was high at 99.3%. Only one patient in the elective group required emergency bypass surgery. The overall incidence of bleeding complications was low at 3%. In the elective group one patient required blood transfusion and another underwent surgical repair of a false aneurysm. Twenty-two patients (52.3%) in the nonelective group and 14 patients (31.8%) in the elective group had either positive exercise ECG or thallium Table 3 Secondary end-points End-point
Non-elective
Elective
P
1. Procedural success 2. Vascular complications 3. Unstable angina 4. Positive exercise test
64 1 16 22
67 (98.5%) 3 (4.4%) 1 (1.4%) 14 (31.8%)
0.9 0.62 0.0004 0.12
(100%) (1.5%) (25%) (52.3%)
F.R. Amin et al. / International Journal of Cardiology 71 (1999) 121 – 127
scan (P 5 0.12) and were subsequently referred for repeat coronary angiography. However, they were still on the waiting list for coronary angiography at the time of follow-up. During the follow-up period, more patients presented with unstable angina (25% vs. 1.4%, P 5 0.0002) in the non-elective group compared with the elective group. This was reflected in an increased need for hospitalisation and repeat coronary angiography within 6 months following stenting in this group. Of those patients, only two were detected to have in-stent restenosis in the target lesion. One was treated by repeat PTCA and the second by CABG.
4. Discussion To our knowledge this is the first prospective study that has examined the clinical outcome of patients undergoing elective and non-elective stent implantation. In this study the clinical and angiographic characteristics of the two groups of patients were broadly similar. However, patients considered for elective stenting had a higher incidence of prior PTCA and bypass surgery compared with the nonelective group. The procedural success rate was 100% in the non-elective group and 98.5% in the elective group. This study demonstrated an overall low incidence of major clinical events (3%) of death, non-fatal myocardial infarction or the need for repeat revascularisation when both groups were considered at 6 months, in keeping with the results of more recent studies [6,14]. Furthermore, there was no significant difference in the occurrence of these events between the two groups. Several earlier studies have demonstrated a higher incidence of inhospital clinical events in patients undergoing bailout stenting compared with patients undergoing elective stenting [4,12,13]. The low rate of in-hospital events in this study may be due to several factors, including optimal vessel dilation, appropriate stent selection, complete coverage of the stenotic lesion, or dissection and the use of the two-pronged anti-platelet combination (aspirin and ticlopidine) as adjunctive pharmacological agents. A total of 15.6% of patients in the non-elective group and 20.6% of patients in the elective group required placement of multiple stents to completely
125
cover the lesions. The frequency of use of multiple stents in previous trials has varied between 4 and 47% [7–10]. Some investigators have reported the use of multiple stents as a significant risk factor for subsequent sub-acute stent thrombosis [11,12]. This assertion is not confirmed by the present study. There was no difference in the incidence of sub-acute stent thrombosis in patients receiving multiple stents and those receiving a single stent. The first uncontrolled study of emergency coronary stenting reported no deaths or need for CABG in 11 patients at 3 months follow-up [15]. However, several subsequent observational studies of bailout stenting have reported striking differences in the frequency of adverse clinical events between bailout and elective cohorts [11,16]. The data from a large multi-centre registry of Gianturco–Roubin stent placement has shown similar mortality rates (2% vs. 3%), but significantly higher rates of myocardial infarction (5% vs. 1%) and need for bypass surgery (12% vs. 6%) at 90 days in patients undergoing bailout stenting compared with those undergoing elective stenting [11]. Lincoff and colleagues have also reported a higher incidence of myocardial infarction in a bailout group in comparison with an elective group [17]. The frequency of the primary composite end-point of death, non-fatal myocardial infarction and the need for repeat revascularisation in this study was 10.9% among patients who underwent non-elective stenting compared with 5.8% in electively stented patients at 6 months follow-up, and this was not statistically significant. Several comparative studies concerning bailout versus elective stenting have not included the recurrence of unstable or severe limiting angina as an end-point. The rate of recurrence of unstable angina at 6 months follow-up in this study was several times greater in the non-elective group compared with the elective group (25% vs. 1.4%, P 5 0.0004). The increased frequency of unstable angina following non-elective stenting was presumably related to the events surrounding complete or threatened closure of the target vessel rather than placement of the stent per se, as there was no statistical difference in the procedural success and the in-hospital ischaemic complications. In contrast to previous reports [18–20] this study showed an overall low incidence of sub-acute stent
126
F.R. Amin et al. / International Journal of Cardiology 71 (1999) 121 – 127
thrombosis (2.2%) and no significant difference between the elective and the bailout groups. The vascular access site complications were formerly an important source of morbidity and prolonged inhospital stay of patients undergoing stent implantation. These bleeding complications were shown to occur in 7–10% of patients in trials utilising oral anticoagulants [5,21]. This study has clearly demonstrated a low overall incidence of bleeding complications (3%). This was almost certainly ascribed to the avoidance of intense anti-coagulation with heparin and warfarin after the procedure. This study was not designed to identify the rate of restenosis following stent implantation. However, a total of 25% of the patients in the non-elective group and 1.4% in the elective group underwent repeat cardiac catheterisation within 6 months because of recurrence of angina. At the end of the follow-up period, the event-free survival was 62.5% in the bailout group and 89% in the elective group (P 5 0.0009). Despite a higher frequency of complicated lesions and use of multiple stents in several patients, the incidence of event-free survival among electively stented patients in this trial was similar to that of the Stent Restenosis Study (STRESS) [4]. The lack of significant difference in in-hospital ischaemic complications in these two cohorts of patients is a striking feature. This suggests that implantation of stent(s) is equally effective and safe in the emergency setting as it is in the elective situation. The lack of a significant difference in the occurrence of primary end-points between elective and non-elective groups in this study might also be related to proportionately more patients (approximately two-thirds) undergoing stent implantation because of sub-optimal results as opposed to abrupt vessel closure. The higher incidence of event-free survival in the elective group compared with the non-elective group was mainly due to the increased frequency of unstable angina in the latter group and may be independent of stent deployment per se. In this group of patients intra-coronary stenting may decrease the incidence of in-hospital events but not the incidence of clinically significant angina in the medium term. Unlike previous trials, we considered non-elective stenting for failed PTCA at a residual diameter stenosis of just .25%. Therefore, this subgroup of patients with sub-optimal results in the
non-elective cohort were not true emergencies for stenting. The results of earlier trials that examined the comparison between bailout or emergency stenting and more elective stenting may not therefore be comparable to the current study.
5. Study limitations This study was not randomised. There were some differences in baseline characteristics of the two groups. The elective group included patients with saphenous vein graft disease and restenotic lesions. The relatively small number of patients included in this trial may preclude meaningful independent analysis of major clinical outcomes such as death, which are relatively infrequent occurrences. Further, a comparison between sub-groups (sub-optimal versus threatened or established abrupt coronary occlusion) within the non-elective cohort would be inconclusive because of the small number of patients. Longer-term follow-up would be desirable to examine the relative incidence of major adverse clinical events. Finally, routine angiographic follow-up is not available and therefore only clinical restenosis in the two groups can be compared.
6. Conclusions Over the last 10 years intra-coronary stents have emerged as important tools to treat acute complications after angioplasty and to prevent restenosis in native or saphanous vein graft lesions. Earlier studies raised serious concerns over the short- and mediumterm outcomes of patients receiving stents in the emergency situation. This study examined the clinical outcome and procedural efficacy of non-elective stenting compared with more elective stenting with less thrombogenic modern stents in the post-ticlopidine era. The study has clearly demonstrated that stents can be safely implanted in non-elective situations with no significant increase in mortality, incidence of non-fatal myocardial infarctions and vascular complications compared with elective stenting. Although the incidence of unstable angina necessitating hospital admission and repeat coronary angiography was significantly higher in patients undergoing
F.R. Amin et al. / International Journal of Cardiology 71 (1999) 121 – 127
non-elective stenting there was no statistical difference in the frequency of positive exercise test between the two groups. Further large studies are needed to support our findings and to elucidate the mechanisms of increased incidence of angina in the non-elective group.
References [1] Detre K, Holub Kov R, Kelseys S, Cowley M, Kent K, Williams D, Myler R, Faxon D, Holmes D, Bourassa M, Black P, Gosselin A, Bentivoglio L, Leatherman L, Dorrosb G, King SB, Galichia J, Al Bassam M, Martin L, Robertson T, Passaman E. Percutaneous transluminal angioplasty in 1985–1986 and 1977–1981: The National Heart, Lung and Blood Institute Registry. N Engl J Med 1988;318:265–70. [2] Simpfendorfer C, Belardi J, Bellamy G, Galan K, Franco I, Hollman J. Frequency, management and follow-up of patients with acute coronary occlusions after percutaneous transluminal coronary angioplasty. Am J Cardiol 1987;59:267–74. [3] Leimgruber PP, Roubin GS, Hollman J, Cotsonis GA, Meier B, Douglas JS, King Jr. SB, Gruentzig AR. Restenosis after successful coronary angioplasty in patients with single vessel disease. Circulation 1986;73:710–7. [4] Fischman DL, Leon MB, Baim DS, Schatz RA, Savage MP, Penn I, Detre K, Veltri L, Ricci DR, Nobuyoshi M et al. A randomized comparison of coronary stent placement and balloon angioplasty in the treatment of coronary artery disease (the STRESS trial). New Engl J Med 1994;331:496–501. [5] TIMI Study Group. The Thrombolysis in Myocardial Infarction (TIMI) trial Phase I findings. N Engl J Med 1985;310:932–936. [6] Robinson NMK, Thomas MR, Jewitt DE, Wainwright RJ. Comparison of clinical outcome after elective and bail out coronary stent insertion. J Invas Cardiol 1995;7:156–64. [7] Haude M, Issa H, Herber M, Meyer J, Erbel R. Restenosis after intracoronary implantation of Palmaz–Schatz stents. Dtsch Med Wochenschr 1993;118:1349–54. [8] Ellis SG, Savage Fischman MD, Baim DS, Leon M, Goldberg S, Hirshfield JW, Cleman MW, Teirstein PS, Walker C, Bailey S, Buchbinder M, Topol EJ, Schatz RA. Restenosis after placement of Palmaz–Schatz stents in native coronary arteries: initial results of a multi-center experience. Circulation 1992;86:1836–44.
127
[9] Fajadet J, Marco J, Cassagneau B, Robert G, van Dormael M. Coronary stenting with the Palmaz–Schatz stent: the Clinique Pasteur interventional Cardiology Unit experience. In: Sigwart U, Frank Gl, editors, Coronary stenting, Berlin: Springer, 1992, pp. 57–77. [10] Metz D, Urban P, Hoang V, Camenzind E, Chatelain P, Meier B. Predicting ischaemic complications after bailout stenting following failed coronary angioplasty. Am J Cardiol 1994;74:271–4. [11] Kastrati A, Schomig A, Dietz R, Neumann FJ, Richrdt G. Time course of restenosis during the first year after emergency coronary stenting. Circulation 1993;87:1498–505. [12] Sutton JM, Ellis SG, Roubin GS et al. Major clinical events after coronary stenting. The multi-center registry of acute and elective Gianturco–Roubin stent placement. Circulation 1994;89:1126–37. [13] Serruys PW, de Jaegere P, Kiemeeiji C, Macaya H, Rutsch W, Heyndrichx G, Emanuelsson G, Marco J, Legrand V, Maren P, Belardi J, Sigwart U et al. A comparison of balloon expandable stent implantation with balloon angioplasty in patients with coronary artery disease (the Benestent study). New Engl J Med 1994;331:489–95. [14] Chauhan A, Zubaid M, Buller C, Moscovich M, Ricci D et al. Comparison of bail out versus elective stenting: time to reassess our benchmarks of outcome. Catheter Cardiovasc Diagn 1997;41:40–7. [15] Sigwart U, Urban P, Golf S et al. Emergency stenting for acute occlusion after coronary balloon angioplasty. Circulation 1988;78:1121–7. [16] Foley JB, Brown RIG, Penn IM. Thrombosis and restenosis after stenting in failed angioplasty: comparison with elective stenting. Am Heart J 1994;128:12–20. [17] Lincoff AM, Topol EJ, Chapekis AT et al. Intracoronary stenting compared with conventional therapy for abrupt vessel closure complicating coronary angioplasty: a matched case-control study. J Am Cardiol 1993;21:866–75. [18] Nath CF, Muller DWM, Ellis SG. Thrombosis of a flexible coil coronary stent: frequency, predictors and clinical outcome. J Am Coll Cardiol 1993;21:622–7. [19] Haude M, Erbel R, Issa H et al. Subacute thrombotic complication after intracoronary implantation of Palmaz–Schatz stents. Am Heart J 1993;126:15–22. [20] Tamura T, Nakagawa Y, Sawada Y et al. Comparison with three different indications of Palmaz–Schatz stent implantation (abstract). J Invas Cardiol 1995;7:8A. [21] Strauss BH, Serruys PW, Bertrand ME et al. Quantative angiographic follow-up of the coronary Wallstent in native vessels and bypass graft (European experience, March 1986 to March 1990). Am J Cardiol 1992;69:475–81.
Non-elective intra-coronary stenting: are the clinical outcomes comparable to elective stenting at 6 months? Foaud R. Amin MBBCh, MSc*, Mohammed Yousufuddin MBBS, MSc, MRCP, MRCPI, Rod Stables MD, MRCP, Arvinder S. Kurbaan MRCP, Jonathan Clague MD, MRCP, Andrew J.S. Coats DM, FRACP, FACC, Ulrich Sigwart MD, FRCP, FESC, FACC Division of Cardiology, National Heart and Lung Institute, Imperial College, Royal Brompton and Harefield Hospitals, Sydney Street, London SW3 6 NP, UK Received 22 March 1999; received in revised form 7 July 1999; accepted 9 July 1999
Abstract The aim of this study was to compare prospectively the clinical outcome of patients treated with intra-coronary stents as a non-elective / bailout procedure for acute or threatened vessel closure, with those undergoing elective stenting at 6 months. Sixty-four patients (60.2611.7 y) who underwent non-elective stenting for abrupt or threatened vessel closure and / or sub-optimal results were prospectively compared with 68 patients (62610.0 y) who were stented electively. All patients had broadly similar pre-procedural clinical profiles. However, patients in the elective group had a higher incidence of previous PTCA (10.2% vs. 0%, P 5 0.01) and bypass surgery (30.9% vs. 6.3%, P 5 0.0003) compared with the non-elective group. A total of 158 stents (1.19 per patient) were implanted in 132 patients with a procedural success rate of 99.3%. At 6 months follow-up there was no statistical difference in the primary composite end-point of death, myocardial infarction and the need of repeat revascularisation (10.9% vs. 5.8%, P 5 0.35) between the two groups. However, patients in the non-elective group showed a higher incidence of unstable angina compared with the elective group (25% vs. 1.4%, P 5 0.0004). The findings of this study suggest that stents (single or multiple) can be effectively implanted in non-elective situations with no increase in the incidence of death, non-fatal myocardial infarction, and the need of repeat revascularisation at 6 months compared with elective stenting. 1999 Elsevier Science Ireland Ltd. All rights reserved. Keywords: Coronary angioplasty; Elective stent; Non-elective stent; Abrupt occlusion; Sub-optimal results
1. Introduction Percutaneous transluminal coronary angioplasty (PTCA) is widely used in contemporary clinical practice to treat patients with coronary artery disease. Threatened or established abrupt coronary artery occlusion (4–8%) and re-stenosis (30–50%) remain the major limitations of PTCA [1–3]. Abrupt vessel *Corresponding author. Tel.: 144-171-352-8121; fax: 144-171-351861. E-mail address: [email protected] (F.R. Amin)
closure after PTCA may result in major clinical events of death, myocardial infarction, and the requirement for emergency bypass surgery. Patients who were treated with elective stents showed improved angiographic and clinical outcomes compared with those treated with PTCA [4]. Intra-coronary stents have revolutionised the treatment of acute complications associated with standard PTCA with a significant decrease in mortality, incidence of nonfatal myocardial infarction and the need of emergency bypass surgery. There are no prospective studies examining the clinical outcome of elective
0167-5273 / 99 / $ – see front matter 1999 Elsevier Science Ireland Ltd. All rights reserved. PII: S0167-5273( 99 )00124-2
122
F.R. Amin et al. / International Journal of Cardiology 71 (1999) 121 – 127
stenting in comparison with non-elective stenting. In view of the remarkable progress in the operator’s experience, stent technology and the use of ticlopidine, we believe that the results of elective and non-elective stenting are likely to be similar. The aim of this prospective study was to compare the outcomes of patients treated with intra-coronary stenting as a planned, elective procedure with those receiving stents non-electively for abrupt or threatened closure and / or sub-optimal results, following PTCA
2. Methods
2.1. Patient population The study population consisted of a consecutive series of patients with native coronary artery or saphenous vein bypass graft disease who were treated by intra-coronary stenting over a 6 month period in our institution. Patients with restenotic lesions following standard PTCA, selected primary saphenous vein graft and native coronary artery lesions were considered for elective stenting following case conferences involving three or more experienced interventional cardiologists. Patients who developed complications including abrupt or threatened vessel closure and / or sub-optimal results (post-procedural residual diameter stenosis of .25% after PTCA) were included in the non-elective group. Of a total of 132 patients, 68 underwent elective stenting and the remaining 64 underwent non-elective stenting. All patients had either unstable angina or limiting stable symptoms with objective evidence of reversible myocardial ischaemia. Patients with a history of hypersensitivity to aspirin or ticlopidine, contraindication to anticoagulation, recent myocardial infarction or significant left ventricular dysfunction (,35% EF) were excluded. The angiographic exclusion criteria included: target vessel diameter ,2.5 mm, severe proximal tortuosity and diffuse distal disease with poor runoff. The study was approved by the Ethics Committee of the Royal Brompton Hospital and National Heart and Lung Institute. Patient characteristics are summarised in Table 1.
Table 1 Patient characteristics a Non-elective
Elective
P
Number of patients Age (years) Males
64 60.2611.7 47 (73.4%)
68 62.8610.0 51 (75.6%)
NS NS
Risk factors Hypertension Positive family history Diabetes mellitus Hypercholesterolaemia Cigarette smoking
22 27 15 39 33
(34.4%) (42.5%) (23.4%) (60.9%) (51.6%)
16 (23.5%) 26 (38.2%) 14 (20.6%) 33 (48.5%) 24 (35.3%)
NS NS NS NS NS
Angina ( CCS class) Class 1 Class 2 Class 3 Class 4
3 16 23 22
(4.7%) (25.0%) (35.6%) (34.4%)
3 (4.4) 16 (23.5%) 26 (38.2%) 24 (35.3%)
NS NS NS NS
Previous myocardial infarction Restenosis lesion Previous bypass surgery
36 (56.3%) 0 4 (6.3%)
24 (39.7%) 7 (10.3%) 21 (30.9%)
NS 0.01 0.0003
Angiographic variables Location of the lesion LMS LAD RCA LCX SVG
0 30 (46.9%) 21 (32.8%) 13 (20.3%) 0
1 (1.5%) 21 (30.9%) 17 (25.0%) 15 (22.1) 14 (20.6%)
NS NS NS NS 0.001
AHA /ACC class A B1 B2 C
13 19 28 4
(23.3%) (29.7%) (43.8%) (6.3%)
22 (32.5%) 25 (36.8%) 14 (20.6%) 7 (10.3%)
NS NS NS NS
Single vessel disease Double vessel disease Multi vessel disease Reference vessel diameter MLD (mm) Percentage stenosis
17 (26.6%) 25 (39.1%) 22 (34.4%) 3.460.7 1.160.3 66.2610.7
25 (22.1%) 24 (35.3%) 29 (42.6%) 3.760.8 1.460.4 68.7610.7
NS NS NS NS NS NS
a CCS, Canadian Cardiovascular Society; LMS, left main stem; LAD, left anterior descending; RCA, right coronary artery; LCX, left circumflex; SVG, saphenous vein graft; AHA /ACC, Class American Heart Association /American College of Cardiology; MLD, minimal lumen diameter.
2.2. Objectives 2.2.1. Primary end-points Composite of death, non-fatal myocardial infarction, and the need of repeat revascularisation as indicated clinically at 6 months. 2.2.2. Secondary end-points Procedural success rate, vascular complications,
F.R. Amin et al. / International Journal of Cardiology 71 (1999) 121 – 127
recurrence of angina and exercise-induced myocardial ischaemia at 6 months.
2.3. Angiographic assessment Angiographic characteristics were assessed using a computerised quantitative coronary angiographic analysis system (Digitron 3 VACI, Siemens). The angiographic view demonstrating maximum stenosis was used to assess the severity of the lesion. The reference vessel diameter, percentage stenosis, and the minimal luminal diameters were measured before and immediately after the procedure. The degree of tortuousity of the vessel in relation to the obstructive lesion was classified as mild (,458), moderate (45– 908) and severe (.908). The lesions were classified as A, B 1 , B 2 , or C according to the modified American Heart Association /American College of Cardiology scheme. Anterograde flow was assessed using the Thrombolysis in Myocardial Infarction (TIMI) Study flow grade [5] and dissection was classified as either ‘simple’ or ‘complex’.
123
lesions (10.2%) were considered for elective stenting. The remaining 69.3% of patients in the elective group had specific coronary abnormalities where intra-coronary stenting was believed to be superior to PTCA. A mean pressure of 1262.32 atm was applied to implant the stents in both groups. In the non-elective group 7.8 and 29.7% of patients had bailout stents for abrupt closure and dissection, respectively. The remaining 62.5% of this group had intra-coronary stents placed for sub-optimal results. All patients had been on aspirin prior to the procedure. Ticlopidine was commenced a day prior to the procedure in the elective group and after the deployment of the stent in the non-elective group. A 10,000 unit intravenous bolus of unfractionated heparin was administered shortly before the intervention and additional boluses (5000–10,000) were given to maintain an activated clotting time (ACT) of .300 s throughout the procedure. No further heparin was administered after the completion of the interventional procedure. However, aspirin and ticlopidine were continued, the former indefinitely and the latter for 3 weeks.
2.4. Interventional procedure 2.5. Follow-up 2.4.1. Percutaneous transluminal coronary angioplasty Balloon angioplasty was performed using standard techniques via the femoral approach using an 8 French guiding catheter. The mean inflation pressure used to dilate the lesion was 4.7166.10 atm. Multiple inflations with a balloon-to-vessel ratio of 1.1:1 were used before classifying the results as sub-optimal. The development of peri-procedural dissection, intraluminal thrombus, complete or partial coronary obstructions was assessed by computerised quantitative coronary angiographic analysis, clinical and electrocardiographic criteria. 2.4.2. Stent placement Although nine different types of stents were used in this study, the most commonly used was the ACS Multi-Link stent (Guidant /Advanced Cardiovascular System Inc.). Patients with saphenous vein graft disease (20.5%) and patients with previous restenotic
Patients were screened for the development of primary and secondary end-points at 6 months. Patients with recurrent unstable angina following interventional procedure were promptly reassessed by coronary angiography. All the remaining patients with stable symptoms had exercise ECG or Thallium scan and were referred for repeat coronary angiograms when positive.
2.6. Statistical analysis The results are expressed as mean6standard deviation (SD). Two-tailed Fisher’s exact test was used to compare the primary and secondary end-points between elective and non-elective groups. The results were considered to be statistically significant when P , 0.05. The Statistical Program for Social Science (SPSS) for Microsoft Windows was used to analyse the data.
F.R. Amin et al. / International Journal of Cardiology 71 (1999) 121 – 127
124
3. Results The risk factor profile, angina class and angiographic characteristics were broadly similar in both groups. However, patients considered for elective stenting had a higher incidence of prior PTCA (10.2% vs. 0%, P 5 0.01) and bypass surgery (30.9% vs. 6.3%, P 5 0.0003) compared with those in the non-elective group. A total of 158 stents (84 in the elective and 74 in the non-elective group) were implanted in 132 patients (1.19 stents per patient) with a procedural success rate of 99.3%. Only one patient in the elective group required emergency CABG. Three patients in the elective group and one patient in the non-elective group required DC cardioversion for ventricular fibrillation during the procedure
3.1. Angiographic results ( Table 2) After stent implantation the mean minimal luminal diameter (MLD) was increased from 1.1660.39 to 3.1560.77 mm in the non-elective group and from 1.4360.49 to 3.3860.72 mm in the elective group. There was no statistically significant difference in the luminal gain (89% vs. 85%, P 5 0.65) between the two groups.
3.2. Primary end-points ( Fig. 1) There were two deaths (3.3%) in the non-elective group (one in hospital and one out of hospital) and one out-of-hospital death (1.6%) in the elective group. The cause of death of the patient in the elective group was non-Hodgkin’s lymphoma. There was one out-of-hospital non-fatal myocardial infarction in the non-elective group and none in the elective group. In the non-elective group three patients subsequently required surgical revascularisation and one Table 2 Angiographic results Variable Reference vessel Diameter MLD a Residual stenosis a
Non-elective (n 5 64) 3.461.0 3.160.7 7.3612.5%
MLD, minimal lumen diameter.
Elective (n 5 68) 3.660.7 3.360.7 9.8610.6%
P
0.89 0.88 0.75
Fig. 1. Incidence of primary composite end-points in the elective and non-elective groups.
patient underwent repeat PTCA. In the elective group one patient underwent emergency CABG and two patients underwent repeat PTCA within 6 months.
3.3. Secondary end-points ( Table 3) The overall procedural success rate was high at 99.3%. Only one patient in the elective group required emergency bypass surgery. The overall incidence of bleeding complications was low at 3%. In the elective group one patient required blood transfusion and another underwent surgical repair of a false aneurysm. Twenty-two patients (52.3%) in the nonelective group and 14 patients (31.8%) in the elective group had either positive exercise ECG or thallium Table 3 Secondary end-points End-point
Non-elective
Elective
P
1. Procedural success 2. Vascular complications 3. Unstable angina 4. Positive exercise test
64 1 16 22
67 (98.5%) 3 (4.4%) 1 (1.4%) 14 (31.8%)
0.9 0.62 0.0004 0.12
(100%) (1.5%) (25%) (52.3%)
F.R. Amin et al. / International Journal of Cardiology 71 (1999) 121 – 127
scan (P 5 0.12) and were subsequently referred for repeat coronary angiography. However, they were still on the waiting list for coronary angiography at the time of follow-up. During the follow-up period, more patients presented with unstable angina (25% vs. 1.4%, P 5 0.0002) in the non-elective group compared with the elective group. This was reflected in an increased need for hospitalisation and repeat coronary angiography within 6 months following stenting in this group. Of those patients, only two were detected to have in-stent restenosis in the target lesion. One was treated by repeat PTCA and the second by CABG.
4. Discussion To our knowledge this is the first prospective study that has examined the clinical outcome of patients undergoing elective and non-elective stent implantation. In this study the clinical and angiographic characteristics of the two groups of patients were broadly similar. However, patients considered for elective stenting had a higher incidence of prior PTCA and bypass surgery compared with the nonelective group. The procedural success rate was 100% in the non-elective group and 98.5% in the elective group. This study demonstrated an overall low incidence of major clinical events (3%) of death, non-fatal myocardial infarction or the need for repeat revascularisation when both groups were considered at 6 months, in keeping with the results of more recent studies [6,14]. Furthermore, there was no significant difference in the occurrence of these events between the two groups. Several earlier studies have demonstrated a higher incidence of inhospital clinical events in patients undergoing bailout stenting compared with patients undergoing elective stenting [4,12,13]. The low rate of in-hospital events in this study may be due to several factors, including optimal vessel dilation, appropriate stent selection, complete coverage of the stenotic lesion, or dissection and the use of the two-pronged anti-platelet combination (aspirin and ticlopidine) as adjunctive pharmacological agents. A total of 15.6% of patients in the non-elective group and 20.6% of patients in the elective group required placement of multiple stents to completely
125
cover the lesions. The frequency of use of multiple stents in previous trials has varied between 4 and 47% [7–10]. Some investigators have reported the use of multiple stents as a significant risk factor for subsequent sub-acute stent thrombosis [11,12]. This assertion is not confirmed by the present study. There was no difference in the incidence of sub-acute stent thrombosis in patients receiving multiple stents and those receiving a single stent. The first uncontrolled study of emergency coronary stenting reported no deaths or need for CABG in 11 patients at 3 months follow-up [15]. However, several subsequent observational studies of bailout stenting have reported striking differences in the frequency of adverse clinical events between bailout and elective cohorts [11,16]. The data from a large multi-centre registry of Gianturco–Roubin stent placement has shown similar mortality rates (2% vs. 3%), but significantly higher rates of myocardial infarction (5% vs. 1%) and need for bypass surgery (12% vs. 6%) at 90 days in patients undergoing bailout stenting compared with those undergoing elective stenting [11]. Lincoff and colleagues have also reported a higher incidence of myocardial infarction in a bailout group in comparison with an elective group [17]. The frequency of the primary composite end-point of death, non-fatal myocardial infarction and the need for repeat revascularisation in this study was 10.9% among patients who underwent non-elective stenting compared with 5.8% in electively stented patients at 6 months follow-up, and this was not statistically significant. Several comparative studies concerning bailout versus elective stenting have not included the recurrence of unstable or severe limiting angina as an end-point. The rate of recurrence of unstable angina at 6 months follow-up in this study was several times greater in the non-elective group compared with the elective group (25% vs. 1.4%, P 5 0.0004). The increased frequency of unstable angina following non-elective stenting was presumably related to the events surrounding complete or threatened closure of the target vessel rather than placement of the stent per se, as there was no statistical difference in the procedural success and the in-hospital ischaemic complications. In contrast to previous reports [18–20] this study showed an overall low incidence of sub-acute stent
126
F.R. Amin et al. / International Journal of Cardiology 71 (1999) 121 – 127
thrombosis (2.2%) and no significant difference between the elective and the bailout groups. The vascular access site complications were formerly an important source of morbidity and prolonged inhospital stay of patients undergoing stent implantation. These bleeding complications were shown to occur in 7–10% of patients in trials utilising oral anticoagulants [5,21]. This study has clearly demonstrated a low overall incidence of bleeding complications (3%). This was almost certainly ascribed to the avoidance of intense anti-coagulation with heparin and warfarin after the procedure. This study was not designed to identify the rate of restenosis following stent implantation. However, a total of 25% of the patients in the non-elective group and 1.4% in the elective group underwent repeat cardiac catheterisation within 6 months because of recurrence of angina. At the end of the follow-up period, the event-free survival was 62.5% in the bailout group and 89% in the elective group (P 5 0.0009). Despite a higher frequency of complicated lesions and use of multiple stents in several patients, the incidence of event-free survival among electively stented patients in this trial was similar to that of the Stent Restenosis Study (STRESS) [4]. The lack of significant difference in in-hospital ischaemic complications in these two cohorts of patients is a striking feature. This suggests that implantation of stent(s) is equally effective and safe in the emergency setting as it is in the elective situation. The lack of a significant difference in the occurrence of primary end-points between elective and non-elective groups in this study might also be related to proportionately more patients (approximately two-thirds) undergoing stent implantation because of sub-optimal results as opposed to abrupt vessel closure. The higher incidence of event-free survival in the elective group compared with the non-elective group was mainly due to the increased frequency of unstable angina in the latter group and may be independent of stent deployment per se. In this group of patients intra-coronary stenting may decrease the incidence of in-hospital events but not the incidence of clinically significant angina in the medium term. Unlike previous trials, we considered non-elective stenting for failed PTCA at a residual diameter stenosis of just .25%. Therefore, this subgroup of patients with sub-optimal results in the
non-elective cohort were not true emergencies for stenting. The results of earlier trials that examined the comparison between bailout or emergency stenting and more elective stenting may not therefore be comparable to the current study.
5. Study limitations This study was not randomised. There were some differences in baseline characteristics of the two groups. The elective group included patients with saphenous vein graft disease and restenotic lesions. The relatively small number of patients included in this trial may preclude meaningful independent analysis of major clinical outcomes such as death, which are relatively infrequent occurrences. Further, a comparison between sub-groups (sub-optimal versus threatened or established abrupt coronary occlusion) within the non-elective cohort would be inconclusive because of the small number of patients. Longer-term follow-up would be desirable to examine the relative incidence of major adverse clinical events. Finally, routine angiographic follow-up is not available and therefore only clinical restenosis in the two groups can be compared.
6. Conclusions Over the last 10 years intra-coronary stents have emerged as important tools to treat acute complications after angioplasty and to prevent restenosis in native or saphanous vein graft lesions. Earlier studies raised serious concerns over the short- and mediumterm outcomes of patients receiving stents in the emergency situation. This study examined the clinical outcome and procedural efficacy of non-elective stenting compared with more elective stenting with less thrombogenic modern stents in the post-ticlopidine era. The study has clearly demonstrated that stents can be safely implanted in non-elective situations with no significant increase in mortality, incidence of non-fatal myocardial infarctions and vascular complications compared with elective stenting. Although the incidence of unstable angina necessitating hospital admission and repeat coronary angiography was significantly higher in patients undergoing
F.R. Amin et al. / International Journal of Cardiology 71 (1999) 121 – 127
non-elective stenting there was no statistical difference in the frequency of positive exercise test between the two groups. Further large studies are needed to support our findings and to elucidate the mechanisms of increased incidence of angina in the non-elective group.
References [1] Detre K, Holub Kov R, Kelseys S, Cowley M, Kent K, Williams D, Myler R, Faxon D, Holmes D, Bourassa M, Black P, Gosselin A, Bentivoglio L, Leatherman L, Dorrosb G, King SB, Galichia J, Al Bassam M, Martin L, Robertson T, Passaman E. Percutaneous transluminal angioplasty in 1985–1986 and 1977–1981: The National Heart, Lung and Blood Institute Registry. N Engl J Med 1988;318:265–70. [2] Simpfendorfer C, Belardi J, Bellamy G, Galan K, Franco I, Hollman J. Frequency, management and follow-up of patients with acute coronary occlusions after percutaneous transluminal coronary angioplasty. Am J Cardiol 1987;59:267–74. [3] Leimgruber PP, Roubin GS, Hollman J, Cotsonis GA, Meier B, Douglas JS, King Jr. SB, Gruentzig AR. Restenosis after successful coronary angioplasty in patients with single vessel disease. Circulation 1986;73:710–7. [4] Fischman DL, Leon MB, Baim DS, Schatz RA, Savage MP, Penn I, Detre K, Veltri L, Ricci DR, Nobuyoshi M et al. A randomized comparison of coronary stent placement and balloon angioplasty in the treatment of coronary artery disease (the STRESS trial). New Engl J Med 1994;331:496–501. [5] TIMI Study Group. The Thrombolysis in Myocardial Infarction (TIMI) trial Phase I findings. N Engl J Med 1985;310:932–936. [6] Robinson NMK, Thomas MR, Jewitt DE, Wainwright RJ. Comparison of clinical outcome after elective and bail out coronary stent insertion. J Invas Cardiol 1995;7:156–64. [7] Haude M, Issa H, Herber M, Meyer J, Erbel R. Restenosis after intracoronary implantation of Palmaz–Schatz stents. Dtsch Med Wochenschr 1993;118:1349–54. [8] Ellis SG, Savage Fischman MD, Baim DS, Leon M, Goldberg S, Hirshfield JW, Cleman MW, Teirstein PS, Walker C, Bailey S, Buchbinder M, Topol EJ, Schatz RA. Restenosis after placement of Palmaz–Schatz stents in native coronary arteries: initial results of a multi-center experience. Circulation 1992;86:1836–44.
127
[9] Fajadet J, Marco J, Cassagneau B, Robert G, van Dormael M. Coronary stenting with the Palmaz–Schatz stent: the Clinique Pasteur interventional Cardiology Unit experience. In: Sigwart U, Frank Gl, editors, Coronary stenting, Berlin: Springer, 1992, pp. 57–77. [10] Metz D, Urban P, Hoang V, Camenzind E, Chatelain P, Meier B. Predicting ischaemic complications after bailout stenting following failed coronary angioplasty. Am J Cardiol 1994;74:271–4. [11] Kastrati A, Schomig A, Dietz R, Neumann FJ, Richrdt G. Time course of restenosis during the first year after emergency coronary stenting. Circulation 1993;87:1498–505. [12] Sutton JM, Ellis SG, Roubin GS et al. Major clinical events after coronary stenting. The multi-center registry of acute and elective Gianturco–Roubin stent placement. Circulation 1994;89:1126–37. [13] Serruys PW, de Jaegere P, Kiemeeiji C, Macaya H, Rutsch W, Heyndrichx G, Emanuelsson G, Marco J, Legrand V, Maren P, Belardi J, Sigwart U et al. A comparison of balloon expandable stent implantation with balloon angioplasty in patients with coronary artery disease (the Benestent study). New Engl J Med 1994;331:489–95. [14] Chauhan A, Zubaid M, Buller C, Moscovich M, Ricci D et al. Comparison of bail out versus elective stenting: time to reassess our benchmarks of outcome. Catheter Cardiovasc Diagn 1997;41:40–7. [15] Sigwart U, Urban P, Golf S et al. Emergency stenting for acute occlusion after coronary balloon angioplasty. Circulation 1988;78:1121–7. [16] Foley JB, Brown RIG, Penn IM. Thrombosis and restenosis after stenting in failed angioplasty: comparison with elective stenting. Am Heart J 1994;128:12–20. [17] Lincoff AM, Topol EJ, Chapekis AT et al. Intracoronary stenting compared with conventional therapy for abrupt vessel closure complicating coronary angioplasty: a matched case-control study. J Am Cardiol 1993;21:866–75. [18] Nath CF, Muller DWM, Ellis SG. Thrombosis of a flexible coil coronary stent: frequency, predictors and clinical outcome. J Am Coll Cardiol 1993;21:622–7. [19] Haude M, Erbel R, Issa H et al. Subacute thrombotic complication after intracoronary implantation of Palmaz–Schatz stents. Am Heart J 1993;126:15–22. [20] Tamura T, Nakagawa Y, Sawada Y et al. Comparison with three different indications of Palmaz–Schatz stent implantation (abstract). J Invas Cardiol 1995;7:8A. [21] Strauss BH, Serruys PW, Bertrand ME et al. Quantative angiographic follow-up of the coronary Wallstent in native vessels and bypass graft (European experience, March 1986 to March 1990). Am J Cardiol 1992;69:475–81.