Utilization of the Coronary Balloon-Expandable Coil Stent Without Anticoagulation or Intravascular Ultrasound
Background The balloon-expandable coil stent has been proved effective in the management of acute and threatened closure after coronary balloon angioplasty and has been shown to reduce restenosis in patients with suboptimal results after coronary balloon angioplasty. Coronary artery stenting has been limited by the occurrence of stent thrombosis and comorbidity related to anticoagulation. This study was undertaken to determine whether anticoagulation may be removed from poststenting protocols, thus reducing comorbidity without increasing stent thrombosis.
Methods and Results Between September 1994 and May 1995, 369 patients received balloon-expandable coil stents in native coronary arteries at our institution. Of these patients, 216 were selected for a protocol of aspirin and ticlopidine (for 1 month) without anticoagulation. Eligibility for this protocol followed satisfaction of certain procedural and angiographic criteria. These criteria included adequate coverage of intimal dissections, absence of residual filling defects, and normal (TIMI grade 3) flow in the stented vessel after high-pressure balloon inflations. Intravascular ultrasound was not used to guide stent deployment. The stenting procedure was planned in 37% of patients and unplanned in 63% of patients, including 25 (12%) for acute or threatened closure. During the 30-day follow-up period, stent thrombosis occurred in 2 patients (0.9%), there was 1 death (0.5%), and 2 patients (0.9%) underwent coronary bypass surgery. Vascular access-site complications occurred in 4 patients (1.9%), and bleeding that required blood transfusion occurred in 4 patients (1.9%).
Conclusions Patients who receive the coronary balloon-expandable coil stent with optimal angiographic results without intravascular ultrasound guidance can be managed safely with a combination of aspirin and ticlopidine without anticoagulation.
The coronary balloon-expandable coil stent has proved effective in the management of acute or threatened closure complicating percutaneous coronary balloon angioplasty (PTCA).1 2 Recently,3 this device was shown to reduce late restenosis in patients who had suboptimal angiographic results after PTCA. Although long-term anticoagulation was not used during initial clinical work with this stent design, prolonged intravenous heparin administration and anticoagulation with warfarin were adopted as reports of subacute thrombosis emerged from other investigators.4 5 6 During the last 8 years of experience with coronary stents, a variety of extensive anticoagulation regimens have been used. Patients have required prolonged hospitalization while they received intravenous heparin and were stabilized on warfarin therapy. In addition to the increased cost of prolonged hospitalization, extensive anticoagulation has been associated with a substantial incidence of hemorrhagic and vascular access-site complications.1 2
The first reports of extensive coronary stent use without anticoagulation after intravascular ultrasound–guided stent deployment appeared in 1994.7 8 Using intravascular ultrasound, Colombo et al7 8 demonstrated that intracoronary stents were frequently suboptimally deployed and that high-pressure inflations with noncompliant balloons were required to optimize stent deployment. Subsequently, poststenting anticoagulation was successfully omitted in this group of patients. Other investigators9 10 who adopted this strategy of poststenting high-pressure balloon dilation reported similar results using both slotted, tubular stents and coil stents with a combination of aspirin and ticlopidine, without intravascular ultrasound guidance. These studies demonstrated that coronary stents can be placed without the use of anticoagulants and raised questions about the necessity of intravascular ultrasound–guided stent deployment. The present study reports our prospective observational experience using the balloon-expandable coil stent in native coronary arteries guided by angiography alone without subsequent anticoagulation.
From September 1994 through May 1995, 1207 patients underwent PTCA at the University of Alabama at Birmingham. Balloon-expandable coil stents (Cook, Inc) were successfully implanted in the native coronary arteries of 369 patients for various indications, including acute or threatened closure1 2 and elective use3 for suboptimal results after PTCA. Of these patients, 216 were selected for a new drug regimen of antiplatelet therapy without anticoagulation. These patients were selected on the basis of the satisfaction of certain procedural and angiographic criteria. These criteria included adequate coverage of intimal dissections, normal (TIMI grade 3) flow, and absence of residual filling defects in the stented vessel after high-pressure balloon inflations. Some patients were excluded from this new regimen because concurrent medical conditions necessitated chronic anticoagulation (ie, atrial fibrillation or history of thromboembolism). The remaining patients received either the standard poststent anticoagulation therapy1 or anticoagulation with subcutaneous heparin for a period of 14 days. Early in the study, only patients who received single stents as an elective treatment with good angiographic results were selected for this protocol. As experience with this regimen increased, patients who received multiple stents, those who were undergoing multiple-vessel stenting, and those with stenting of infarct-related arteries and stenting after reconstitution of chronic total occlusions were included. During the second half of the study period, 79% of stented patients were selected for this protocol. The proportion of patients who received anticoagulation versus antiplatelet agents during the study period is shown in Fig 1⇓ and represents increasing confidence by the investigators in the new regimen.
All patients received soluble aspirin 325 mg and ticlopidine 250 mg before the angioplasty procedure. When patients were admitted the day before the procedure, they received at least two doses of each of these medications. Patients admitted on the day of the procedure (n=92) received a single dose of each of these drugs. During the procedure, heparin was administered by intra-arterial injection and the dose was adjusted to achieve an activated clotting time between 250 and 350 seconds. Dextran 40 solution was administered in 92 patients. This preparation was removed from the protocol in February 1995, and the last 124 patients in the series received no dextran. All patients received intravenous nitroglycerin during the procedure. Generally, heparin was not administered after the procedure. Sheaths were removed the same day with compression applied with a mechanical device. Patients (n=23) who had their procedure performed late in the day were maintained on intravenous heparin at approximately 1000 U/h overnight, and sheaths were removed early the next morning. Early in the study, 34 patients (16%) received intravenous heparin for a period of 24 to 48 hours after the procedure. No patient received warfarin. Aspirin 325 mg twice daily and ticlopidine 250 mg twice daily were administered during hospitalization and continued for 4 weeks. White blood cell counts were performed after 2 weeks of therapy with ticlopidine. After 4 weeks, patients were managed with aspirin alone.
PTCA and Stenting Procedure
Coronary angioplasty was performed by use of conventional techniques with 8F (ID, 0.086 in) guide catheters via the femoral approach. Coronary lesions were dilated by use of balloon catheters equivalent to the target-vessel size. When a decision was made to proceed with coronary artery stenting, vessel sizing was performed by use of on-line quantitative coronary angiography or visual estimation, and stent size was selected for a stent-to-artery ratio of 1.1:1 to 1.2:1 according to current recommendations.11 Stents were deployed by use of stent balloon-inflation pressures of 4 to 6 atm. After initial deployment, high-pressure balloon inflations were then performed in all patients within the stent by use of a noncompliant balloon equivalent in size to the nominal size of the stent. Adequacy of stent placement was assessed angiographically. The result was considered inadequate if dissection flaps were not completely covered by stent struts, if residual filling defects were present within the stented segment, or if flow was less than TIMI grade 3 in the stented vessel. In these cases, additional high-pressure balloon inflations were performed and/or additional stents were deployed. If optimal results were not achieved, the patient was treated with anticoagulation. Intravascular ultrasound was not used in any patient to ascertain adequacy of stent deployment. Patients were allowed to mobilize 10 to 12 hours after removal of the arterial sheath. If they remained stable, they were generally discharged from the hospital 2 days after the procedure.
In-hospital stent thrombosis was defined as angiographic TIMI grade 0 to 1 flow in the stented vessel or myocardial infarction with the development of new Q waves on the ECG. Non–Q-wave myocardial infarction was defined as creatine kinase (CK) elevation more than twice 250 IU/L with a positive CK-MB isoenzyme. Out-of-hospital stent thrombosis was defined as any unexplained sudden death or myocardial infarction within the 30-day period after the procedure or readmission to the hospital with symptoms and ECG or laboratory evidence of myocardial infarction in the distribution of the stented vessel. Vascular access-site complications were categorized as pseudoaneurysm, arteriovenous fistula, or hematoma requiring blood transfusion. Pseudoaneurysm was clinically identified as an expansile groin mass and was confirmed by an ultrasound examination. Major bleeding was defined as that which required a blood transfusion.
All demographic, clinical, and technical data were collected prospectively on standard forms and entered into a computerized database. Subsequently, all hospital charts were audited for accuracy and completeness of the database information. All patients were contacted by telephone at least 30 days after hospital discharge. This follow-up information was also entered on standard forms for analysis. Follow-up information was 99% complete. ECGs were recorded immediately after the procedure, then daily before discharge. CK levels were measured immediately after the procedure and twice thereafter at 8-hour intervals. If the patient had recurrent symptoms after the procedure, additional ECGs and CK estimations were performed. Quantitative angiographic measurements were performed by use of electronic calipers. Data are expressed as mean±1 SD.
The study group consisted of 158 men and 58 women. The mean age was 61±11 years (range, 32 to 92 years); 50 (23%) of the patients were older than 70 years. Forty-two (19%) of the patients had undergone previous bypass surgery, and 73 (34%) of them had undergone previous PTCA. Sixty-nine (32%) of the patients had single-vessel disease, 90 (42%) had two-vessel disease, and 57 (26%) had three-vessel disease. Other demographic data are shown in Table 1⇓. The indication for PTCA was stable angina in 26% of patients, unstable angina in 48%, ischemia after myocardial infarction in 14%, and other indications in 12%. Coronary artery stenting was performed as a planned procedure in 80 (37%) of the patients and was unplanned in 136 (63%). Of the planned stenting procedures, 46 (58%) were de novo lesions, 24 (30%) were restenotic lesions, and 10 (12%) were ostial lesions. The unplanned stenting procedures were performed for suboptimal results in 111 (82%) of the patients, threatened closure in 22 (16%), and acute closure in 3 (2%) (Fig 2⇓).
Lesion and Stent Characteristics
There were a total of 346 balloon-expandable coil stents implanted in 240 vessels. Thirteen patients had additional single, slotted, tubular stents implanted during the same procedure. One hundred twenty (56%) of the patients received a single stent, 68 (31%) received two stents, and 28 (13%) received three or more stents. Twenty-four (11%) of the patients underwent double-vessel stenting. The mean number of stents per vessel was 1.5±0.7 (range, 1 to 4), and the mean number of stents per patient was 1.6±0.9 (range, 1 to 6). The left anterior descending coronary artery was stented in 38% of patients, the right coronary artery in 39%, and the left circumflex coronary artery in 30%. One patient underwent stenting of a protected left main coronary artery. Two patients had concurrent balloon angioplasty and stenting of vein grafts. Nineteen patients (9%) had stents deployed after reconstitution of chronic total occlusions. Thirty patients (14%) with recent myocardial infarction (<10 days before the procedure) underwent stenting of the infarct-related artery. Twenty-five patients (12%) had conventional balloon angioplasty performed of one or more additional vessels during the same procedure.
Average reference-vessel diameter was 2.97±0.52 mm. Of the 240 vessels stented, 38 (16%) were 2.0 to 2.5 mm in diameter, 98 (41%) were 2.5 to 3.0 mm, 67 (28%) were 3.0 to 3.5 mm, 28 (12%) were 3.5 to 4.0 mm, and 9 (4%) were 4.0 to 4.5 mm (Table 2⇓). Minimal luminal diameter before PTCA was 0.69±0.44 mm, and the percentage diameter stenosis was 77±14%. Lesion length was 12.9±8.4 mm. Final minimal luminal diameter after stenting was 2.99±0.56 mm, with a final percent stenosis of 5±12%. Average nominal stent size was 3.44±0.4 mm. Of the 359 stents deployed, 5 (1%) were 2.5 mm in diameter, 125 (35%) were 3.0 mm, 138 (38%) were 3.5 mm, and 91 (25%) were 4.0 mm. Final balloon size was equivalent to nominal stent size in 91% of stents, 0.5 mm larger in 8%, and 0.5 mm smaller in 1%. The mean final balloon-inflation pressure was 15.3±2.1 atm (range, 12 to 22 atm). The nominal stent size–to–vessel diameter ratio was 1.17±0.17 (Table 3⇓).
Clinical Outcome and Ischemic Complications
During the 30-day follow-up period, stent thrombosis occurred in 2 (0.9%) of the patients, and there was 1 death (0.5%). Of the 2 patients with stent thrombosis, one underwent salvage PTCA for acute myocardial infarction after failed thrombolytic therapy, and the dilated segment was stented because of threatened closure. This patient underwent urgent bypass grafting on day 5 for subacute thrombosis. The other patient developed severe bleeding from the large bowel and hypotension 14 days after stenting that required cessation of antiplatelet agents and subsequently a colectomy. The patient died suddenly with ventricular fibrillation in the postoperative period and was found at postmortem to have stent thrombosis. There were no Q-wave myocardial infarctions. Non–Q-wave myocardial infarction occurred in 8 patients (3.7%) and was associated with side-branch occlusion in 7. In 1 patient, non–Q-wave myocardial infarction was attributed to embolization during concurrent PTCA of a vein graft. Repeat angiography was performed on only 19 patients (9%) during the follow-up period; in all cases, stent patency and TIMI grade 3 flow were demonstrated. One patient who underwent repeat angiography because of recurrent ischemic chest pain was found to have a suboptimal angiographic result, with tissue prolapse between the stent struts. A decision was made to send this patient for bypass surgery in view of multiple previous interventions and multivessel coronary disease. The average hospital stay from procedure to hospital discharge was 2.5±1.5 days (range, 1 to 10 days); 48 (22%) patients were discharged from the hospital the day after the procedure.
Hemorrhagic and Vascular Access-Site Complications
Pseudoaneurysm of the cannulated femoral artery occurred in two patients. Both patients were in the early phase of the study and had received postprocedural heparin infusions. One pseudoaneurysm was closed by mechanical compression; the other required surgical closure. One patient developed transient femoral neuropathy related to groin compression with a mechanical device. Bleeding that required blood transfusion occurred in four (1.9%) of the patients.
Adverse Drug Reactions
During the 30-day follow-up period, five (2%) of the patients had adverse reactions attributed to ticlopidine, which required its cessation. Two patients developed gastrointestinal upset, one developed a decrease in hematocrit attributed to gastrointestinal blood loss, and two developed a rash. Neutropenia was not documented in any patient during the follow-up period.
The present study demonstrates that patients who receive the balloon-expandable coil stent with optimal angiographic results without intravascular ultrasound guidance may be managed safely with a combination of the antiplatelet agents aspirin and ticlopidine without anticoagulation. Outcomes observed in the present study were stent thrombosis (0.9%), vascular access-site complications (1.9%), and major bleeding (1.9%). This protocol simplifies patient management after stenting and reduces the morbidity, length, and cost of hospitalization.
Comparison With Other Studies
Studies that incorporated standard anticoagulation regimens after coronary stenting for acute or threatened closure reported stent thrombosis rates of 8%1 2 to 16%.12 Other adverse outcomes reported were myocardial infarction in 6%2 to 20%, urgent coronary bypass surgery in 4%1 2 to 13%,12 and death in 2%1 2 to 4%.12 Adverse event rates were lower in studies that incorporated standard anticoagulation in patients undergoing elective coronary artery stenting, with stent thrombosis rates of 3% to 4%, myocardial infarction in 5% to 6%, and coronary bypass surgery in 2% to 3%.13 14 Standard anticoagulation regimens were associated with vascular access-site complications in 6% to 16%1 6 15 and bleeding that necessitated blood transfusion in 5% to 20%.1 2 15 The current study, which incorporated both “bailout” and elective stenting, compares favorably with respect to the incidence of stent thrombosis and vascular access-site and bleeding complications.
Recently, Colombo et al8 reported the results of 338 patients who received slotted, tubular stents without postprocedural anticoagulation. The incidence of stent thrombosis was 0.9%. That study differed from the present study in that the majority of patients had intravascular ultrasound–guided stent deployment, whereas in the present study, stent deployment was guided by angiography alone. In addition, the present study had an increased number of patients with bailout as the indication for stenting (12% versus 5%), stenting of an infarct-related artery (14% versus 1%), and stenting after reconstitution of a chronic total occlusion (9% versus 5%). Multiple stents were deployed in 44% of patients in the present study, and 57% of vessels stented were ≤3.0 mm in diameter. Despite the unfavorable profile of the present study population,16 the incidences of stent thrombosis, myocardial infarction, and coronary artery bypass surgery were comparable to the study reported by Colombo et al.8 These favorable results were achieved with careful selection of stent size relative to reference-artery size (ratio of 1.1:1 to 1.2:1) and with supplementary high-pressure balloon inflations after stent deployment. Meticulous care was taken to cover all intimal dissections. Patients were excluded from the present study if there was reduced flow, residual dissection, or filling defects within the stented vessel.
Role of Intravascular Ultrasound
The role of intravascular ultrasound–guided stent deployment and selection of patients for poststenting protocols without anticoagulation remains uncertain. Optimal stent deployment guided by intravascular ultrasound has been defined as achieving a cross-sectional area within the stent equal to or greater than the cross-sectional area of the distal reference lumen. In addition, ultrasound should demonstrate symmetrical stent expansion with good apposition of the stent wires against the vessel wall and no significant residual luminal narrowing. This has been postulated to be the critical element in the reduction of stent thrombosis and the removal of anticoagulation from poststenting protocols.8 Although a low incidence of stent thrombosis was reported in a study that used ultrasound guidance,8 a comparable outcome has been achieved in studies in which angiography was used to guide stent deployment.9 10 17 Complete stent expansion can be confirmed more accurately with intravascular ultrasound than with angiography.18 19 20 Likewise, the full extent of intimal dissections and their subsequent management may be better defined with intravascular ultrasound than with angiography.21 Nonetheless, in the present study with routine use of high-pressure balloon inflations within the coil stent, absence of ultrasound guidance does not appear to have adversely affected early clinical outcomes. Routine use of intravascular ultrasound increases procedural time and cost and on occasion has been reported to cause complications.8 18 19 Given the excellent outcomes achieved with angiography-guided stent deployment and no postprocedural anticoagulation, it would appear that the coil stent can be deployed safely and effectively without intravascular ultrasound guidance. It currently is not known whether angiographically guided stent deployment will have similar late outcomes and restenosis rates compared with intravascular ultrasound–guided stent deployment.
Role of Ticlopidine
Although ticlopidine was used in the present study, its value as an adjunct to aspirin after coronary artery stenting is unproved. Ticlopidine has been demonstrated to reduce ischemic outcomes in patients after thromboembolic stroke compared with placebo.22 One study23 demonstrated reduced acute closure after coronary angioplasty in patients who received ticlopidine compared with placebo. However, another study24 demonstrated equivalent efficacy between ticlopidine and aspirin for this indication. Others8 have reported equivalent poststenting outcomes in patients who received aspirin compared with patients who received the combination of aspirin and ticlopidine. The role of ticlopidine after coronary artery stenting needs to be defined further.
This study was a nonrandomized, prospective, observational study, and the criteria for patient selection changed during the period of the study. Initially, only elective patients who were having single stents deployed were selected. As physician confidence with the regimen increased, the selection criteria broadened to include patients who were receiving multiple stents, patients undergoing multivessel stenting, and patients who presented with acute ischemic syndromes or who required bailout stenting. Although not all stented patients were eligible for the study, this series does represent a consecutive series of patients assigned to this new regimen. The relative importance of the factors responsible for the results achieved, that is, the use of ticlopidine, disuse of warfarin and dipyridamole, or use of high-pressure inflations with noncompliant balloons, cannot be determined from the present study. Physicians involved in the present study represented a group of experienced operators who perform large numbers of stenting procedures.
This observational study indicates that patients who receive the balloon-expandable coil stent in native coronary arteries can be managed safely with a combination of aspirin and ticlopidine without anticoagulation provided that certain procedural and angiographic criteria are satisfied. These criteria include adequate coverage of intimal dissections, absence of residual filling defects, and TIMI grade 3 flow in the stented vessel after high-pressure balloon inflations. Intravascular ultrasound–guided stent deployment was not used in achieving these results.
We wish to thank Anne Cameron, RN, Cynthia Sutor, RN, MPH, and Phyllis Slaughter for their assistance with data management and patient follow-up.
- Received July 31, 1995.
- Revision received November 16, 1995.
- Accepted November 21, 1995.
- Copyright © 1996 by American Heart Association
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