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Ann Thorac Surg 2000;70:1997-2003
© 2000 The Society of Thoracic Surgeons
a Department of Cardiology and Angiology/Institute for Arteriosclerosis Research, Hospital of the Westfälische Wilhelms-University, Münster, Germany
b Department of Cardiothoracic Surgery, Hospital of the Westfälische Wilhelms-University, Münster, Germany
c Hospital of the Westfälische Wilhelms-University, Münster, Germany
Accepted for publication June 26, 2000.
Address reprint requests to Dr Schmid, Klinik und Poliklinik für Thorax- Herz- & Gefäßchirurgie, Universitätsklinik Münster, Albert-Schweitzer-Str 33, 48129 Münster, Germany
e-mail: schmid{at}uni-muenster.de
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Abstract |
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 Top Abstract IntroductionPatients and methodsResultsCommentAcknowledgmentsReferences |
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Methods. Patients who underwent PTCA and subsequent emergency CABG were identified from the databases of the Departments of Cardiology and Cardiothoracic Surgery.
Results. Two periods of clinical practice were compared. In 1989 to 1993, 2,880 PTCAs were performed, 64 patients underwent emergency CABG (2.3%), and 7 patients died (10.9%). During 1994 to 1998, 46 patients of 3,801 PTCAs underwent emergency CABG (1.2%, p < 0.01), and 7 patients died (15.2%, NS). The average rate of stenting increased from 0.8% to 24% in 1994 to 1998 as well as the frequency of arterial bypass grafts (0% vs 39%). In the latter period, patients were older, were more often females, had more cardiovascular risk factors, a higher Cleveland score (each p < 0.05), and suffered more often from periprocedural myocardial infarctions (p < 0.001) and nonfatal periprocedural complications (p < 0.01).
Conclusions. Although the frequency of emergency CABG after failed PTCA declined, perioperative mortality tended to increase according to an unfavorable shift in patient risk factors and morbidity.
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Introduction |
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TopAbstractIntroductionPatients and methodsResultsCommentAcknowledgmentsReferences |
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During recent years, the experience of PTCA operators and their teams has increased. PTCA results have especially been improved by application of premounted coronary stents. Simultaneously, indications for PTCA have been continuously extended and new groups of patients presented for PTCA. The value of PTCA has even been demonstrated in patients with multivessel disease [8] and with acute myocardial infarction [9]. Thus, there are obviously opposing trends, with improved PTCA performance on the one hand and an increase in severity of coronary artery disease and general morbidity on the other. The purpose of this evaluation was to assess the impact of patient characteristics and procedural performance on perioperative outcome of patients undergoing emergency CABG after failed PTCA, and to analyze whether changes in these factors influence acute and long-term outcome.
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Patients and methods |
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TopAbstractIntroductionPatients and methodsResultsCommentAcknowledgmentsReferences |
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Data acquisition and evaluation
Hospital records were reviewed for cardiovascular risk factors, concomitant diseases, previous surgery, and periprocedural complications. The diagnosis of periprocedural myocardial infarction was based on a perioperative increase of CK levels of 100 U/L or more with a 10% fraction of CK-MB, or occurrence of new Q-waves in the predischarge electrocardiogram (Minnesota Code).
All data recorded during PTCA were analyzed with regard to the type of catheters, number of inflations, periprocedural problems (eg, need for intensive treatment), and time delays (eg, from initial onset of a problem to surgery). Angiographies of the PTCA patients who underwent subsequent emergency CABG were evaluated in a blinded manner by two experienced cardiologists for the type of stenosis (according to the AHA/ACC classification) and the angiographic problem leading to surgery.
Left ventricular ejection fraction (EF) was assessed from the pre-PTCA angiogram and determined by biplane ventriculography. It was classified into the categories "normal" (EF > 60%), "mildly reduced" (EF 50% to 59%), "moderately reduced" (EF 40% to 49%), and "severely reduced" (EF < 40%) in accordance with others [1, 10].
Patients were classified as having undergone intensive treatment if any of the following treatments had been performed: intubation, pacemaker stimulation for bradycardia, administration of catecholamines, implantation of an intraaortic balloon counterpulsation (IABP), or cardiocompression.
Complete revascularization after emergency CABG for failed PTCA was defined as revascularization (by angioplasty or coronary bypass grafting) of all major coronary arteries with a stenosis of 50% or more. Incomplete revascularization was characterized by at least one major coronary artery with a residual stenosis of greater than 50% without successful angioplasty or bypass grafting [11, 12].
The individual perioperative risk of each patient was assessed by calculating the so-called Cleveland score according to the studies of Higgins and associates [10]. It classifies the patient’s perioperative risk, which is considered to be increased with more than 5 points and to be severely increased with 10 or more [13, 14].
Revascularization procedures
Coronary angioplasty was performed following the standard techniques of Judkins or Sones. Each patient received 1 g acetylsalicylic acid intravenously and at least 7,500 units of heparin at the beginning of the procedure. Intracoronary nitrates were regularly and repeatedly administered.
All PTCAs were performed with in-house cardiovascular surgical backup. Rapid surgical support in the catheter laboratory was provided within a few minutes. The operating rooms of the Department of Cardiothoracic Surgery were located two floors below the catheterization laboratories. CABG was performed in moderate hypothermia with cold cardioplegic arrest using Brettschneider’s cardioplegia or cold retrograde blood cardioplegia since 1997.
Follow-up
Follow-up information was obtained by telephone interviews with the patients, their relatives, or general practitioners (if the patient was deceased). The questions focused on actual physical abilities and recurrence of angina pectoris or exercise-related dyspnea. Answers were classified in accordance with the grading of the Canadian Cardiovascular Society (CCS). In addition, patients were asked for occurrence of myocardial infarctions or subsequent need for diagnostic or interventional procedures (angiography, PTCA, or CABG).
Statistical analysis
All statistical tests were performed with SPSS 9.0. for Windows, license number 7127699. Univariate analyses were made using Student’s unpaired t test for continuous variables (displayed as means ± SEM), cross-tables with the 
2 test for dichotomous variables, and the Mann-Whitney rank sum test for categorical variables. Analyses for predictors of death during follow-up were performed with Kaplan-Meier models and the log rank test. Statistic significance was assumed if a p value of 0.05 or less was achieved. Multivariable analyses were performed by logistic regression with a step-wise backward algorithm. The variables used for multivariable analyses were: age, body surface area, cardioplegia technique, Cleveland score, gender, grade of revascularization, left ventricular function, number of diseased coronary vessels, stent implantation, total bypass time, and use of arterial grafts.
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Results |
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TopAbstractIntroductionPatients and methodsResultsCommentAcknowledgmentsReferences |
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The angiographic problems that were associated with emergency CABG were (numbers of patients in brackets): dissection at the culprit lesion (64), occlusion (22), thrombus formation (13), a vessel segment that cannot be reached with wire/balloon/stent (7), perforation of the vessel (3), and rupture of the guide wire with a residual fragment in the coronary artery that cannot be removed (1).
At the end of PTCA and before surgery, 93 patients (85%) suffered from angina pectoris at rest, 84 patients (76%) showed significant ST-segment alterations, and 45 patients (41%) needed at least one of the intensive treatments as described above.
Factors influencing in-hospital mortality after emergency CABG
Characteristics and procedural variables of patients surviving emergency CABG compared with those who died during the 30-day postoperative period are presented in Table 2. The frequency of patients with multivessel disease was higher among the nonsurvivors (85% vs 60%, p < 0.05). Renal failure (27% vs 11%, NS), diabetes (35% vs 15%, NS), and peripheral occlusive disease (28% vs 18%, NS) were each observed more frequently in nonsurvivors after emergency CABG.
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No association was found between periprocedural death and type of catheter, number of inflations, or previous PTCAs. GpIIb/IIIa inhibitors were used in only two of the patients who underwent emergency CABG, of whom none died. Retrograde cold blood cardioplegia was performed in 11 patients, of whom 1 (8.3%) died, compared with 99 patients with cold crystalloid cardioplegia, of whom 13 patients died (13%, NS).
Multivariable analyses with logistic regression identified higher Cleveland score (odds ratio 1.73, 95% CI 1.14 to 2.61, p = 0.0092), lower body surface area (odds ratio 0.014, 95% CI 0.0004 to 0.42, p = 0.014), and incomplete revascularization (odds ratio 0.21, 95% CI 0.05 to 0.82, p = 0.025) to be predictive for perioperative death.
Complications after emergency CABG
The causes of in-hospital death after emergency CABG included (number of patients in brackets) cardiac low-output failure (8), septic multiorgan failure (4), and fatal thromboembolic events (2). Redo sternotomy had to be performed in 3 patients (in 2 patients because of pericardial tamponade and in 1 patient because of suspected bypass occlusion). Other nonfatal in-hospital complications included atrial tachyarrhythmias (9), low-output failure demanding high-dose catecholamines or IABP placement (8), neurological disorders (6), systemic infections (5), pleural effusions (4), respiratory insufficiency (4), acute renal failure (3), deep vein thrombosis (3), nonfatal thromboembolic events (2), bradycardias requiring pacemaker stimulation (2), and hematoma of the groin (2). Ventricular tachycardia, pancreatitis, and a transitory ischemic attack were observed in 1 patient each.
Influence of time period on patient and procedural characteristics
For statistical analysis of any time-dependent changes, the observed 10-year period was split into two halves: 1989 to 1993 and 1994 to 1998. With regard to PTCA procedures and patients in general, an unfavorable shift in patient risk profile could be observed from 1989 to 1993 compared with 1994 to 1998 (Table 1): PTCA patients were significantly older (+2.3 years), more often female (+3.1%), and more often underwent emergency PTCAs due to unstable angina or acute myocardial infarction (+3.8%).
Similarly, patients who underwent emergency CABG after failed PTCA were also older (+4.0 years), were more often female (+10%), and more frequently had concomitant diseases such as diabetes (+12%) or hypertension (+24%) in the recent time period (Table 3). This trend was confirmed by calculation of the Cleveland score, which was significantly lower in patients of 1989 to 1993 compared with those of 1994 to 1998. Furthermore, the rate of patients who needed intensive treatment during PTCA increased significantly in 1994 to 1998 compared with 1989 to 1993 (54.3% vs 31.3%, p < 0.05). This is important, because only 1 patient died of the 65 patients who did not need preoperative intensive treatment (1.7%), whereas of the 45 patients with intensive interventions, 13 patients died (29%, p < 0.001).
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Analysis of the in-hospital complications demonstrated a significantly higher rate of periprocedural myocardial infarctions during the recent time period (20% vs 61%, p < 0.001) and an increase in nonfatal periprocedural complications from 30% in 1989 to 1993 to 59% in 1994 to 1998 (p < 0.01, only survivors after emergency CABG).
Long-term follow-up
The 30-day perioperative period was survived by 96 patients. Long-term follow-up of these patients was 100% complete for information on survival or late death. In 2 patients, no information could be obtained about their functional status and recent interventions (97.9% complete). Follow-up time was 5.3 ± 2.5 years (range 157 days to 9.7 years). At census, 8 patients have died (8.3%), 80% of the surviving patients were described to have physical abilities according to CCS grade I or II, 39% again experienced angina or exercise dyspnea, in 24% at least one invasive intervention (coronary angiography, PTCA or CABG) had been performed again, and 8% had suffered from new myocardial infarctions.
In the group of patients operated on during 1989 to 1993, the mean follow-up time was 8.0 ± 0.4 years (95% CI 7.2 to 8.8 years); during that time, 7 patients died. The number of patients still in follow-up was 50 and 7 at 5 and 9 years, respectively. In the group of the latter period from 1994 to 1998, the mean follow-up was 3.9 ± 0.3 years (95% CI 3.4 to 4.5 years). During that follow-up, only 1 patient died. The number of patients still in follow-up was 34 and 9 at 1 and 4 years, respectively. In a Kaplan-Meier model, the survival curves met each other at 4.2 years with a cumulative survival of 82.5% of the patients of both groups. A log-rank analysis found no differences in the long-term survival (p = 0.65) between the patients of the early compared with the recent time period.
Patients who had experienced an anterior myocardial infarction had a reduced long-term survival (7.9 ± 0.5 years, 95% CI 6.8 to 8.9 vs 9.5 ± 0.2 years, 95% CI 9.1 to 9.8; p < 0.01, log-rank test) as well as patients with renal failure (6.0 ± 0.6 years, 95% CI 4.8 to 7.3 vs 9.3 ± 0.2 years, 95% CI 8.9 to 9.7; p < 0.001). Nonsignificant trends were observed in patients who died during follow-up with regard to higher age (+6.7 years) and longer cardiopulmonary bypass time during emergency CABG (+19 minutes). Furthermore, patients in which the left anterior descending artery was the culprit vessel tended to have a reduced survival (8.4 ± 0.4 years, 95% CI 7.6 to 9.2 vs 9.3 ± 0.3 years, 95% CI 8.8 to 9.8; p = 0.2). Long-term survival of patients with or without complete revascularization was similar (9.0 ± 0.3 years, 95% CI 8.6 to 9.6 vs 8.7 ± 0.6 years, 95% CI 7.5 to 9.9; p = 0.7). None of the patients who received stents (n = 22) or arterial bypass grafts (n = 17) died during follow-up.
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Comment |
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TopAbstractIntroductionPatients and methodsResultsCommentAcknowledgmentsReferences |
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In accordance with many others, the incidence of emergency CABG for failed PTCA declined significantly over time in our analysis, whereas the total number of PTCAs and the proportion of stenting increased continuously. One may discuss whether the proportion of stenting in our institution was too low. The relatively low rate of 24% stenting in the period of 1994 to 1998 was from the fact that this was a calculated average over the 5 years. However, the annual rates of stenting were comparable with other centers at that time [1, 2]. Nevertheless, emergency CABG will remain important and necessary even if stent implantation will further increase.
Factors influencing clinical outcome
Most important risk factors for a fatal outcome after PTCA as well as after CABG are multivessel disease, impaired left ventricular function, age, female gender, diabetes, renal failure, and low body surface area [1, 15, 16]. All of these factors were also found to be important factors in our emergency CABG patients. Thus, our study is in good accordance with these mostly larger settings.
Another confounding factor in analysis of patient outcome after emergency CABG is whether patients have been in an unstable hemodynamic condition, which would be a more strict definition of emergency CABG as stated by others [6], or whether they have been operated on because of an unfavorable angiographic result. Such differences in the clinical status might be the reason why previous studies reported a relatively high rate of patients who underwent emergency CABG for failed PTCA but a low rate of subsequent myocardial infarctions and mortality [3, 17]. In contrast, all of our patients were in an unstable situation, with chest pain at rest and significant ST alterations refractory to all conservative treatments, and about 40% of them required intensive treatment because of hemodynamic instability. Thus, our perioperative mortality of 12.7% is in good agreement with other studies that also used a stricter definition of emergency CABG [4, 6, 18] and with analyses using the Cleveland score for risk evaluation, revealing that a score of 5 or even 10 is associated with a preoperative mortality of 5% or 13%, respectively [13, 14].
The delay from onset of myocardial ischemia to emergency CABG has also been considered to determine patient outcome. Some authors have reported such a time-dependent relationship [17], whereas other studies with larger numbers of patients including this one failed to prove this relationship [4, 18]. Because benefit of a more rapid emergency CABG could not be demonstrated, some authors suggested a less rigorous surgical standby [18]. Nevertheless, we, like others [7, 17], still would argue that if CABG without delay because of hemodynamic instability or ongoing cardiopulmonary resuscitation is required, prognosis of patients is extremely poor, and therefore would favor surgery as fast as possible.
Grade of revascularization
Complete revascularization by elective CABG [11] or PTCA [12] has been shown to be an important factor for outcome that has yet to be analyzed in patients undergoing emergency CABG after failed PTCA. Our results demonstrated a significant association between incomplete revascularization and death after emergency CABG for failed PTCA. However, the degree of revascularization might be influenced by the hemodynamic status of the patient. Most surgeons aim to reduce bypass time, especially in patients who arrive in the operation room with advanced myocardial ischemia. Whether the increased mortality in the patients with incomplete revascularization is indeed because of the incomplete revascularization and a subsequent ischemic burden, or merely reflects the poor preoperative condition of the patients, can therefore not be definitely decided. Furthermore, not all coronary vessels can be grafted with bypasses due to unfavorable anatomy, eg, small or diffusely altered vessels. Nevertheless, in patients with multivessel disease, optimizing coronary blood flow in as many vessels as possible might increase myocardial perfusion by retrograde flow through collateral vessels and thereby improve left ventricular function and clinical outcome [4, 11].
Similarly, the harvest of arterial grafts may be much more time consuming and therefore inappropriate in an emergency setting. Our data show that the small subset of patients who received an arterial graft tended to have a lower perioperative mortality. However, considerations made above for complete revascularization concerning unfavorable hemodynamic or anatomic conditions also apply to the use of arterial bypass grafts.
Cardioplegia techniques
Special cardioplegia techniques, especially those using blood cardioplegia, have been shown to improve outcome significantly in patients with elective CABG and represent the current state of the art [19]. However, in this and also in other studies [4, 7], a protective effect of these techniques to lower myocardial damage and to improve outcome could not be identified in patients undergoing emergency CABG. Because most of the emergency CABG studies were limited by a relatively small number of patients, this might be one confounding factor for these results. Additionally, there is a controversial discussion as to whether ischemic myocardial damage in this patient cohort mostly occurs before cardioplegic arrest and therefore cannot be salvaged even by a very effective myocardial protection during extracorporal circulation [4]. There is further evidence from recent studies that substrate-enhanced blood cardioplegia [19] or cardioplegia solutions with esmolol [20] improve outcome even in patients with emergency CABG.
Time-dependent changes
Apart from the correlation between increased rate of stenting and declined incidence of emergency CABG, in our study, the patients of the more recent period had a significantly higher cardiovascular and general morbidity concerning age, gender, multivessel disease, and important risk factors such as diabetes, hyperlipidemia, hypertension, or renal failure. The calculated Cleveland score, which includes the most important risk factors, was significantly higher in the patients of the recent period. Similarly, we observed a significant increase in postoperative myocardial infarctions, periprocedural intensive treatment, nonfatal postoperative complications, and a nonsignificant trend toward a higher mortality after emergency CABG. It remains unclear whether these developments resulted from an unfavorable shift in the general PTCA population or whether the patients of the recent period who finally underwent emergency CABG represented a more "negative selection" compared with previous years. However, the result is an increase in mortality after emergency CABG.
Despite the observed higher in-hospital mortality in the recent patient group, at 4.2 years after operation, the cumulative survival was identical. One can speculate whether this might result from the higher proportion of patients with stents and arterial grafts in the recent period, which are known to be associated with an improved long-term outcome, although a significant effect of those factors could not be shown.
Limitations
Because our study is a retrospective analysis, it is limited by several factors. The data presented are based on a 10-year single-center experience, which will not necessarily be representative for other institutions. We therefore presented detailed information about definitions and patient and procedural data to enable a comparison with other institutions. However, most of the factors identified to be predictive (eg, age, gender) are independent from procedural performance and cannot be influenced. Factors like the need for intensive treatment during and after PTCA can also not or hardly be influenced and just reflect the critical condition of the patients. Because performance of complete revascularization and harvest of arterial grafts were not randomized in this study, these factors need further evaluation to determine whether they really can improve patient outcome or if the observed effects are biased by other factors. Thus, the consequences from this analysis focus on risk stratification before and during PTCA performance.
Conclusion
Despite great procedural advances, emergency CABG after failed PTCA remains a serious complication with a high morbidity and mortality rate. Although the frequency of emergency CABG has decreased, its mortality tended to increase in our analysis according to an unfavorable shift in patient cardiovascular and general morbidity. Knowledge of factors influencing clinical outcome allow risk stratification and patient selection for PTCA. Further studies will have to prove whether special cardioplegia techniques or complete revascularization even during emergency CABG have a positive impact on patient outcome.
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Acknowledgments |
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TopAbstractIntroductionPatients and methodsResultsCommentAcknowledgmentsReferences |
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References |
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TopAbstractIntroductionPatients and methodsResultsCommentAcknowledgmentsReferences |
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