Ann Thorac Surg 1999;68:1644-1647
© 1999 The Society of Thoracic Surgeons
Original Articles
Favorable impact of stents after emergent coronary artery bypass for failed angioplasty
Harold L. Lazar, MDa,
Yusheng Bao, MDa,
Diane Lancaster, PhDa,
Oz M. Shapira, MDa,
Gabriel S. Aldea, MDa,
Richard J. Shemin, MDa
a Department of Cardiothoracic Surgery, Boston Medical Center, and Boston University School of Medicine, Boston, Massachusetts, USA
Address reprint requests to Dr Lazar, Department of Cardiothoracic Surgery, Boston Medical Center, 88 E Newton Street, Suite B404, Boston, MA 02118
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Abstract
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Background. This study was undertaken to determine the impact of the use and availability of coronary stents on outcomes in patients requiring emergent coronary artery bypass graft (CABG) surgery following a failed percutaneous transluminal coronary angioplasty (PTCA).
Methods. Patients were divided into two groups based on the year of their CABG for a failed PTCA and the availability of stents: group 1, 1992 to 1994, stents not available (n = 34); and group 2, 1995 to 1997, stents available (n = 26).
Results. CABG patients in the group where stents were not available were more likely to have had an abrupt coronary occlusion (26 of 34 versus 3 of 26; p < 0.0001) and less likely to have had a dissection (8 of 34 versus 23 of 26; p < 0.0001) as their indication for emergent CABG. Patients in the stent era had a lower incidence of perioperative myocardial infarction (5 of 26 versus 17 of 34; p < 0.01) and a decreased mortality rate (0 of 26 versus 6 of 34; p< 0.03). In the 9 patients where stents were employed, patency of the lumen was restored in 8 patients and there was only 1 myocardial infarction.
Conclusions. Stents have had a favorable impact on patients requiring an emergent CABG following a failed PTCA.
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Introduction
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The operative mortality and incidence of myocardial infarction (MI) following emergent coronary artery bypass graft (CABG) surgery for a failed percutaneous transluminal coronary angioplasty (PTCA) has not changed significantly over the past decade despite advances in surgical techniques, myocardial protection, and circulatory support devices. In many series, it remains greater than 10% [1–4]. The emergence of coronary stents has significantly lowered the incidence of abrupt coronary occlusion during PTCA and has decreased the need for emergent CABG [5–10]. Despite the availability of stents, a small percentage of PTCA patients continue to require emergent CABG because of persistent coronary occlusion or dissection resulting in ischemia. This study was therefore undertaken to determine the impact of the use and availability of coronary stents on outcomes in patients requiring emergent CABG following a failed PTCA.
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Patients and methods
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Patients were divided into two groups based on the year of their CABG following a failed PTCA and the availability of stents: group 1, 1992 to 1994, stents not available (n = 34); and group 2, 1995 to 1997, stents available (n = 26). During 1995 to 1997, the stents used in the majority of cases were the Palmaz-Schatz stent (Johnson and Johnson International Systems Co, Warren, NJ) and the Gianturco-Roubin stent (Cook Inc, Bloomington, IN). Patients who developed restenosis following stent insertion after leaving the catheterization laboratory, or in whom recurrent ischemia developed following discharge and ultimately required CABG, were excluded from the study.
The study population consisted only of those patients transported directly to the operating room from the cardiac catheterization laboratory following a failed PTCA. Ischemia resulting from acute or threatened coronary closure or dissections were indications for emergent CABG. Acute closure was defined as occlusion of the vessel with thrombolysis in myocardial infarction (TIMI) 0 or 1 flow. Threatened closure occurred when two or more of the following criteria existed: (1) a residual stenosis greater than or equal to 50%, (2) TIMI grade 2 flow, (3) angiographic dissection with extraluminal dye extravasation for a length of greater than 15 mm, and (4) evidence of clinical ischemia (angina or electrocardiogram (ECG) changes). A significant dissection was present if extraluminal dye was present for a length of greater than 15 mm. A PTCA was considered to be a failure if flow could not be restored to the vessel or a significant dissection persisted.
The decision to insert an intraaortic balloon pump (IABP) or a bailout reperfusion catheter was made by the interventional cardiologist. Inotropic agents were used when necessary to maintain a systolic blood pressure of 90 mm Hg or greater and a cardiac index of at least 2.0 L/min/m2. Decisions regarding whether to use an internal mammary artery graft and which type of delivery system to use for cardioplegic solutions were made by the individual surgeon. All vessels with a lesion of 50% or greater were grafted. A perioperative MI was defined as the development of new pathological Q-waves (
40 msec) and/or elevation of the myocardial fraction of creatine kinase (CK-MB) to greater than 50 IU in the initial 24 hours following CABG. Mortality was defined as any in-hospital death or death within 30 days of CABG.
Univariate differences between patients in the period where stents were not available and those when stents were available were assessed using Fisher’s exact test or 
2 analysis for discrete variables and the unpaired Student’s t test for continuous data. All mean data represent the mean ± standard error. Differences were considered significant when p values were less than 0.05.
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Results
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The results are summarized in Tables 1–4. Prior to the availability of stents, the incidence of emergent CABG for failed PTCA was 1.68% (34/2018). Although the incidence of emergent CABG fell to 1.29% (26/2003) during the period when stents were available, this decrease was not statistically significant.
Table 1 reviews the profiles of patients who underwent emergent CABG following a failed PTCA in both groups. There was no significant difference in mean age or female gender or the incidence of diabetes, hypertension, peripheral vascular disease, or renal dysfunction between the two groups. Although ejection fraction was similar in both groups, patients in the group where stents were available had a higher incidence of unstable angina (19 of 34 versus 23 of 26; p < 0.01).
The catheterization data is reviewed in Table 2. Stents were placed in 9 patients undergoing emergent CABG from 1995 to 1997. Although the stent era patients had a higher incidence of multivessel disease (13/26 versus 20/34), this was not statistically significant. The mechanism of PTCA failure was more likely to be coronary occlusion in the period prior to stent availability (26 of 34 versus 3 of 26; p < 0.0001) as opposed to coronary dissection when stents were available (8 of 34 versus 23 of 26; p < 0.0001). Preoperative IABPs were more likely to be used during the stent era (21 of 26 versus 17 of 34; p < 0.02), whereas "bailout" reperfusion catheters were more frequently used prior to stent availability (13 of 34 versus 7 of 26; p = not significant [NS]). There was no difference in the need for inotropic agents between the two groups. Although the incidence of post-PTCA ECG changes was higher in the patients prior to stent availability, this did not reach statistical significance (15 of 34 versus 7 of 26; p = NS). The distribution of culprit vessels was similar in both groups.
The operative data is summarized in Table 3. Patients undergoing emergent CABG during the period when stents were available had significantly more vessels bypassed during surgery (2.76 ± 0.02 versus 2.09 ± 0.01; p < 0.005), which was reflected in a longer cross-clamp time (25.5 ± 2.1 minutes versus 37.2 ± 2.8 minutes;p < 0.001). The type and delivery of cardioplegia was similar in both groups. Although the stent era patients had a higher incidence of the use of an internal mammary artery graft, this did not reach statistical significance (15 of 26 versus 13 of 34; p = NS).
Table 4 reviews the clinical outcomes. Patients undergoing emergent CABG in the period when stents were available had a significantly lower incidence of myocardial infarction (17 of 34 versus 5 of 26; p < 0.02), and a significantly decreased mortality rate (6 of 34 versus 0 of 26; p < 0.03). There was no statistical difference in the incidence of sternal infections, respiratory insufficiency, sepsis, reoperation for bleeding, and postoperative hemodialysis between the groups. Each of the 6 patients who expired in the non-stent available group experienced a total coronary occlusion in the catheterization laboratory during PTCA. These occlusions could not be crossed with bailout catheters, required IABP and inotropic support, and had ECG changes immediately following the PTCA. All 6 of these patients had a documented MI and their cause of death was cardiac related. In the 9 patients who received a stent prior to their emergent CABG, only 1 patient had a coronary occlusion; the remaining patients had a dissection not covered by the stent. Seven of the 9 patients had a preoperative IABP and none required inotropic support. One patient had ECG changes following the PTCA; that patient was the only stented patient to have a perioperative MI.
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Comment
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The availability of coronary stents has decreased the incidence of abrupt coronary artery closure following a PTCA, which has been shown to be the most important factor influencing mortality, the incidence of an MI, and the need for emergent CABG [11]. In a multicenter investigation of coronary stents employed to treat abrupt coronary occlusion, there was a significant increase in coronary blood flow in over 95% of stented patients [6]. In several series, the incidence of an emergent CABG following a failed PTCA fell below 3% when stents were employed [7–9].
Our previous studies and those of others have shown that the presence of ischemia and hemodynamic instability in the catheterization laboratory is the most important factor in determining clinical outcomes following a failed PTCA [1–4]. The post-PTCA angiographic appearance of the dilated vessel is most predictive of an acute ischemic event [7]. A persistent coronary occlusion results in severe injury that is often not fully reversible by the time coronary blood flow is reestablished after an emergent CABG [1–4]. Although a significant (> 15 mm) coronary dissection can be associated with an increased risk of an acute occlusion or an ischemic event [12], some blood flow is still present in the injured vessel, which greatly decreases the incidence of a MI during emergent CABG.
In our study, the presence of a coronary occlusion was the most common indication for emergent CABG in the period when stents were not available. The patients in this group had a higher mortality rate than in the period when stents were available. All 6 patients who expired had a total coronary occlusion, required an IABP, and inotropes, and had evidence of acute ECG changes in the catheterization laboratory. The presence of these changes has been associated with a higher incidence of a perioperative MI and increased mortality in our earlier series [1–3]. In contrast, only 11.5% of patients in the period when stents were available had a total coronary occlusion, which probably accounted for the decreased incidence of MIs in this group. In the 9 patients where stents were placed, only 1 had a persistent coronary occlusion. That patient went on to develop ECG changes in the catheterization laboratory and was the only stented patient to sustain a MI. These results are similar to those observed by Craver and coworkers who studied the results of CABG in patients after coronary stenting [13]. In patients undergoing CABG within 24 hours after stent placement for an unsuccessful PTCA, the incidence of an MI was 14%. However, in those patients undergoing CABG for abrupt closure 1 to 7 days after the initial stent placement, the rate of MI increased to 50%. These data, as well as our own, support the concept that increasing blood flow by stenting following an abrupt closure decreases the incidence of MI and leads to a lower mortality rate following emergent CABG for a failed PTCA.
Despite the success of coronary stenting in treating abrupt coronary occlusion following a PTCA, a small, but significant number of patients require emergent CABG. In our series, the most common indication for CABG was a persistent dissection greater than 15 mm in length that could not be covered by a stent. Dissections greater than 15 mm in length have a higher incidence of abrupt occlusion [12, 14]. In the presence of a long dissection, our interventional cardiology colleagues were less likely to place an antegrade perfusion catheter, which explains the decreased incidence of bailout catheters in the group where stents were available and the more frequent use of the IABP in these patients. The newer models of stents currently being used are likely to result in a further reduction in abrupt closure and more complete "covering" of dissections when they occur following a PTCA.
In conclusion, our study has demonstrated that the availability of stents has had a favorable impact on patients who undergo emergent CABG. Stents have contributed to a decreased incidence of ischemia and hemodynamic instability in the catheterization laboratory when a PTCA has failed. This has resulted in a significant decrease in mortality and the incidence of perioperative MIs.
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Accepted for publication April 14, 1999.
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Abstract
Introduction
