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Ann Thorac Surg 2005;80:131-135
© 2005 The Society of Thoracic Surgeons

Original article: Cardiovascular

Using the EuroSCORE to Assess Changes in the Risk Profiles of the Patients Undergoing Coronary Artery Bypass Grafting Before and After the Introduction of Less Invasive Coronary Surgery

Toshihiro Ohata, MD, PhD*, Mitsunori Kaneko, MD, Toru Kuratani, MD, Hideki Ueda, MD, Kazuo Shimamura, MD

Division of Cardiovascular Surgery, Osaka Prefectural General Hospital, Osaka, Japan

Accepted for publication February 1, 2005.

* Address reprint requests to Dr Ohata, Department of Cardiovascular Surgery, Hyogo College of Medicine, 1-1 Mukogawa, Nishinomiya, Hyogo, 663-8501, Japan (Email: tohata{at}aol.com).


   Abstract
Top
 Abstract
Introduction
 Patients and Methods
 Results
 Comment
 Requirements for...
 References
 
BACKGROUND: Patients undergoing coronary artery bypass grafting seem to be older and have more comorbidity than patients in prior decades. We retrospectively assessed changes in the predicted mortality risk of patients who underwent coronary artery bypass surgery before and after the introduction of minimally invasive surgical techniques.

METHODS: Between 1993 and 2002, 345 consecutive patients underwent coronary bypass surgery at Osaka Prefectural General Hospital. Minimally invasive direct coronary artery bypass was introduced in 1997 and off-pump bypass in 1999. Patients were divided into two groups, based on the year of surgery (1993 to 1996 and 1997 to 2002), and mortality risk was assessed with the European System for Cardiac Operative Risk Evaluation (EuroSCORE).

RESULTS: The in-hospital mortality was 3% overall (11 of 345), 8% during the early period (6 of 106), and 2% during the later period (5 of 239). Multiple regression analysis identified an emergent operation to be an independent predictor of in-hospital mortality (p = 0.035). Factors associated with higher scores were recent myocardial infarction (p = 0. 028), preoperative intraaortic balloon pumping (p = 0.026) and preoperative ventilation (p = 0.026), but not age. Scores were higher in the minimally invasive (6.5 ± 3.6, p = 0.004) and off-pump (5.0 ± 3.7, p = 0.04) groups than in the conventional bypass group (4.1 ± 3.3). The arterial graft in coronary artery bypass graft group was significantly less than in off-pump coronary artery bypass group (0.8 ± 0.8 vs 1.2 ± 0.8, p = 0.0001). Despite the increasing risk scores, overall in-hospital mortality decreased.

CONCLUSIONS: The EuroSCORE was useful for assessing changes in the risk profile of patients undergoing bypass surgery over the past decade. The decrease in in-hospital mortality despite the increased risk might reflect the introduction of less invasive coronary surgery in high-risk patients.


   Introduction
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 Abstract
 Introduction
Patients and Methods
 Results
 Comment
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 References
 
Patients undergoing coronary artery bypass grafting (CABG) seem to be older and have more comorbidity than patients in prior decades. However, there have been few objective reports on changes in risk profile. Cardiopulmonary bypass and cardioplegic arrest have become mainstays of CABG in the last three decades. The major benefits of these innovations – a bloodless operative field and greater accessibility of the coronary vessels – have made this procedure safe and common [1]. Nevertheless, cardiopulmonary bypass has long been claimed to be responsible for systemic inflammation and multiple organ dysfunction after CABG [2]. To minimize these complications, off-pump coronary artery bypass grafting (OPCAB) was introduced. As the number of patients undergoing CABG without cardiopulmonary bypass has increased, operative mortality [3] and morbidity [4], ICU and hospital stays [5], and cost [4, 5] have decreased. These findings are often cited as arguments in favor of OPCAB.

Improvements in operative techniques have made cardiac surgery possible in higher-risk patients. Owing to the increasing age, disease severity, and comorbidity of such patients, risk stratification has become an important tool in assessing the quality of surgical care. The European System for Cardiac Operative Risk Evaluation (EuroSCORE) was designed to predict in-hospital mortality and allow risk-adjusted assessment of quality of surgical care [6, 7]. In this retrospective study, we used the EuroSCORE to assess changes in the mortality risk of patients undergoing CABG in our hospital over the past decade before and after the introduction of minimally invasive surgical techniques.


   Patients and Methods
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 Abstract
 Introduction
 Patients and Methods
Results
 Comment
 Requirements for...
 References
 
Patients
Between 1993 and 2002, 345 consecutive patients underwent CABG at Osaka Prefectural General Hospital. There were 248 men and 97 women, with a mean age of 66.9 ± 9.7 years (range 33 to 89 years old). In our hospital, minimally invasive direct coronary artery bypass (MIDCAB) was introduced in 1997 and OPCAB in 1999. The patients were divided into two groups, based on the year of surgery: 1993 to 1996 and 1997 to 2002. During the early period, 106 patients underwent conventional CABG. During the later period, CABG was performed in 134 cases, OPCAB in 77, and MIDCAB in 28.

EuroSCORE
Mortality risk was assessed with the EuroSCORE [6, 7], which consists of three groups of weighted risk factors: patient related, cardiac related, and operation related (Table 1). Each factor is assigned a score representing the additive percent predicted mortality. The sum of the scores is the predicted mortality risk (Tables 1 and 2).


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  		Table 1. EuroSCORE
 
Surgical Technique
Conventional CABG
CABG was performed through a median sternotomy under moderate (early period) or mild (later period) hypothermic cardiopulmonary bypass. Myocardial protection is obtained by intermittent glucose-insulin-potassium solution or by antegrade and retrograde cold-blood cardioplegia with topical cooling. Proximal anastomoses were performed under partial or single aortic clamping. Internal thoracic artery or saphenous vein grafts were harvested with standard technique. In the later period, radial artery graft was used.

MIDCAB
The patient was placed in a spine position with the left shoulder elevated about 30 degrees. A left anterior minithoracotomy (8–10 cm) was performed, and the fourth intercostal space was entered, the fourth rib was resected, and the left internal thoracic artery was harvested under direct vision. In high-risk patients, saphenous vein graft was used, with inflow from left subclavian artery. Proximal coronary artery flow was controlled with silicone rubber loops (Retract-O-tape; Quest, Allen, TX). Suction-type tissue stabilizers (Octopus I, II and III; Medtronic, Inc, Minneapolis, MN) were used to maximize access and stabilize coronary arteries. Heparin (1.5 mL/kg) was administered before vessel occlusion and was fully reversed before closure of the sternum.

OPCAB
OPCAB was carried out through a median sternotomy. The left internal thoracic artery was harvested with standard techniques; during the later period, a harmonic scalpel was used. Deep pericardial traction sutures were placed on the left side for exposure of the left anterior descending artery. The Starfish heart positioner (Medtronic, Inc.) was used for exposure of left circumflex artery, posterior descending and atrioventricular branches. Vessels were stabilized and managed as described above.

Both conventional and OPCABG patients were discharged receiving aspirin and warfarin sodium.

Statistical Analysis
Continuous data are expressed as means ± standard deviation. Continuous variables are compared by paired or unpaired t tests and the Mann-Whitney rank-sum test where applicable. Multivariate logistic regression analysis was performed to derive independent predictors of hospital mortality. Univariate analysis was performed to determine the elevation of EuroSCORE. All analyses including univariate analyses were performed using the Statview v4.5 statistical package (Abacus Concepts Inc., Berkeley, CA). Differences were considered significant at p less than 0.05.


   Results
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 Abstract
 Introduction
 Patients and Methods
 Results
Comment
 Requirements for...
 References
 
In-Hospital Mortality
The in-hospital mortality was 3% overall (11 of 345), 8% during the early period (6 of 106) of the study (1993 to 1996), and 2% (5 of 239) during the later period (1997 to 2002). During the early period, 2 patients died of acute myocardial infarction and one each of methicillin-resistant Staphylococcus aureus enterocolitis, low-output heart failure, mediastinitis, and intraoperative aortic dissection. During the later period, 2 patients died of acute myocardial infarction, and 1 patient each of methicillin-resistant Staphylococcus aureus mediastinitis, multiple organ failure due to duodenal perforation, and intraoperative aortic dissection. Two of 11 patients who died were in the OPCAB group, and 9 were in the CABG group. There was no mortality in the MIDCAB group.

Multivariate logistic regression analysis identified an emergent operation to be an independent predictor of in-hospital mortality (p = 0.0345, Table 3).


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  		Table 3. Multiple Logistic Regression Analysis
 
Mid-Term Mortality
The mid-term mortality was 11.8% overall (38 of 322), 24.4% during the early period (22 of 90), and 6.9% during the later period (16 of 232). It was 7% (2 of 28) in the MIDCAB group during 1997 to 2004, 7% (5 of 75) in the OPCAB group during 1999 to 2004, and 13% (31 of 231) in the CABG group during 1993 to 2004. Two patients were lost followed in the OPCAB group and ten in the CABG group. In the MIDCAB group, 1 patient died of cerebral hemorrhage and 1 patient died of ventricular fibrillation. In the OPCAB group, 2 patients died of infection, 1 of heart failure, 1 of cerebral hemorrhage, and 1 of cancer. In the CABG group, 14 patients died of heart failure, 7 of cerebral hemorrhage, 3 of ventricular fibrillation, 2 of digestive bleeding, 2 of infection, 2 of sudden death, and 1 of cancer.

EuroSCORE
The mean EuroSCORE increased from 2.9 in 1993 to 5.8 in 2002 (Fig 1), and the change of EuroSCORE increased significantly (Fig 2). The score during 2001 and 2002 was significantly higher than during 1995 and 1996, and 1993 and 1994 (p = 0.0133, p = 0.0003). The score during 1999 and 2000, and during 1997 and 1998 were significantly higher than during 1993 and 1994 (p = 0.0108, p = 0.0017). Among patients who died, the mean score was 8.0 ± 4.4 (range, 0 to 15). The scores were significantly higher in the MIDCAB (6.5 ± 3.6, p = 0.004) and OPCAB (5.0 ± 3.7, p = 0.04) groups than in the CABG group (4.1 ± 3.3) (Fig 3).



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  		Fig 1. The change of EuroSCORE: the mean EuroSCORE in 1993 was 2.9 and it doubled in 2002 to 5.8. (EuroSCORE = European System for Cardiac Operative Risk Evaluation.)

 


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  		Fig 2. The comparison of the EuroSCORE within 2-year ranges: the score during 2001 and 2002 was significantly higher than during 1995 and 1996, and 1993 and 1994 (p = 0.0133, p = 0.0003). The scores during 1999 and 2000, and during 1997 and 1998 were significantly higher than during 1993 and 1994 (p = 0.0108, p = 0.0017). *p < 0.05; **p < 0.01. (EuroSCORE = European System for Cardiac Operative Risk Evaluation.)

 


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  		Fig 3. The comparison of the EuroSCORE between the procedures: the scores in the MIDCAB and OPCAB groups were significantly higher than in the CABG group (p < 0.004 and p < 0.04, respectively). (CABG = coronary artery bypass grafting; EuroSCORE = European System for Cardiac Operative Risk Evaluation; MIDCAB = minimally invasive coronary artery bypass; OPCAB = off pump coronary artery bypass.)

 
There were more cases of unstable angina and renal dysfunction in the later period than in the early period (p = 0.003, p = 0.0445). Recent myocardial infarction, preoperative intraaortic balloon pumping (IABP), and preoperative ventilation were significantly correlated with the score (p = 0.028, p = 0.026, and p = 0.025, respectively, Table 4). Age was not a significant factor in score elevation; the mean age was 65.1 ± 1.5 years in the early period and 67.2 ± 1.9 in the latter period (p = 0.086).


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  		Table 4. Univariate Analysis of Risk Factors for EuroSCORE
 
Clinical Outcome
The total graft number in CABG group was 2.6 ± 0.9, 2.2 ± 0.9 in OPCAB group, and 1.0 in MIDCAB group. The graft number of CABG group was significantly higher than OPCAB (p = 0.0005) and MIDCAB group (p < 0.0001). The graft number in OPCAB group was higher than in MIDCAB (p < 0.0001). The arterial graft number was 0.5 ± 0.3 in the early period and 1.0 ± 0.6 in the later period. The arterial graft was significantly less used in the early period than the later period (p < 0.0001). The arterial graft number was 0.7 ± 0.5 in MIDCAB group, 1.2 ± 0.8 in OPCAB group, and 0.8 ± 0.8 in CABG group. The arterial graft in OPCAB group was significantly higher than in MIDCAB (p = 0.0095) and CABG group (p = 0.0001). The venous graft number was 0.3 ± 0.5 in MIDCAB, 1.0 ± 1.0 in OPCAB, and 1.9 ± 1.1 in CABG group. The venous graft in CABG group was significantly higher than in MIDCAB (p < 0.0001) and OPCAB group (p < 0.0001). The venous graft in OPCAB was higher than in MIDCAB (p = 0.0002).

The hospital stay was 22.4 ± 11.7 days in MIDCAB group, 19.1 ± 7.6 in OPCAB group, and 28.6 ± 31.0 in CABG group. There was no significant difference in three groups.


   Comment
Top
 Abstract
 Introduction
 Patients and Methods
 Results
 Comment
Requirements for...
 References
 
This study shows that the predicted mortality risk of patients undergoing coronary artery bypass surgery doubled between 1993 and 2002, as assessed with the EuroSCORE, and significantly increased in the later part of the decade. Factors associated with higher scores were recent myocardial infarction, preoperative IABP, and preoperative ventilation, but not age. The scores were significantly higher in the MIDCAB and OPCAB groups than in the conventional CABG group. Despite the increasing the risk score, overall in-hospital mortality decreased. Multiple regression analysis identified an emergent operation to be an independent predictor of in-hospital mortality.

Several factors may have contributed to the increased risk. First, more patients with recent myocardial infarction and preoperative IABP are being treated surgically, possibly because of improvements in catheter devices for diagnosis and in circulatory assist devices such as IABP and percutaneous cardiopulmonary support that make possible a smooth transition from cardiologist to surgeon. Second, advance of preoperative respiratory management may improve the outcome among the patients with preoperative ventilation. On the other hand, owing to better hemodialysis techniques and to the increasing number of patients with diabetes mellitus, more patients with renal dysfunction are undergoing CABG. Advances in the perioperative management including continuous hemodialysis and hemofiltration may improve the outcome among those with end-stage renal disease. Since the percentage of patients with renal dysfunction will likely grow, one can anticipate increased risk related to renal factors.

Even though the mortality risk among our patients doubled during the decade of the study, the overall in-hospital mortality decreased. Thus, one might question whether the EuroSCORE accurately reflected the prognosis. One possibility is the emergence of OPCAB as a viable alternative in certain high-risk groups, such as octogenarians and those with impaired left ventricular function [8, 9]. In addition, OPCAB for multivessel revascularization in high-risk patients significantly reduced perioperative myocardial infarction and mortality rates [9]. The introduction of minimally invasive procedures, such as MIDCAB and OPCAB, that are more suitable for high-risk patients likely contributed to improved clinical outcome and decreased in-hospital mortality.

Despite the perception that CABG is being performed an increasing number of older patients, the mean age of our patients rose from 65.1 to 67.2 and did not contribute to the elevation in risk scores. The presence of some younger patients in the later period of the study might be responsible for this finding.

In summary, the EuroSCORE was useful for assessing changes in the risk profiles of our patients undergoing coronary artery bypass surgery between 1993 and 2002. The decrease in in-hospital mortality despite the increased risk might reflect the introduction of less invasive coronary surgery in high-risk patients.


   Requirements for Recertification/Maintenance of Certification in 2006
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 Patients and Methods
 Results
 Comment
 Requirements for...
References
 
Diplomates of the American Board of Thoracic Surgery who plan to participate in the Recertification/Maintenance of Certification process in 2006 must hold an active medical license and must hold clinical privileges in thoracic surgery. In addition, a valid certificate is an absolute requirement for entrance into the recertification/maintenance of certification process. if your certificate has expired, the only pathway for renewal of a certificate is to take and pass the Part I (written) and the Part II (oral) certifying examinations.

The American Board of Thoracic Surgery will no longer publish the names of individuals who have not recertified in the American Board of Medical Specialties directories. The Diplomate’s name will be published upon successful completion of the recertification/maintenance of certification process.

The CME requirements are 70 Category I credits in either cardiothoracic surgery or general surgery earned during the 2 years prior to application. SESATS and SESAPS are the only self-instructional materials allowed for credit. Category II credits are not allowed. The Physicians Recognition Award for recertifying in general surgery is not allowed in fulfillment of the CME requirements. Interested individuals should refer to the Booklet of Information for a complete description of acceptable CME credits.

Diplomates should maintain a documented list of their major cases performed during the year prior to application for recertification. This practice review should consist of 1 year’s consecutive major operative experiences. If more than 100 cases occur in 1 year, only 100 should be listed.

Candidates for recertification/maintenance of certification will be required to complete all sections of the SESATS self-assessment examination. It is not necessary for candidates to purchase SESATS individually because it will be sent to candidates after their application has been approved.

Diplomates may recertify the year their certificate expires, or if they wish to do so, they may recertify up to two years before it expires. However, the new certificate will be dated 10 years from the date of expiration of their original certificate or most recent recertification certificate. In other words, recertifying early does not alter the 10-year validation.

Recertification/maintenance of certification is also open to Diplomates with an unlimited certificate and will in no way affect the validity of their original certificate.

The deadline for submission of applications for the recertification/maintenance of certification process is May 10 each year. A brochure outlining the rules and requirements for recertification/maintenance of certification in thoracic surgery is available upon request from the American Board of Thoracic Surgery, 633 N St. Clair St, Suite 2320, Chicago, IL 60611; telephone: (312) 202-5900; fax: (312) 202-5960; e-mail: mailto:info{at}abts.org. This booklet is also published on the website: www.abts.org.


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  		Table 2. Application of Scoring System
 

   References
Top
 Abstract
 Introduction
 Patients and Methods
 Results
 Comment
 Requirements for...
 References
 
  1. Favaloro RG. Saphenous vein graft in the surgical treatment of coronary artery diseaseOperative technique. J Thorac Cardiovasc Surg 1969;58:178-185.[Medline]
  2. Westaby S. Organ dysfunction after cardiopulmonary bypassA systemic inflammatory reaction initiated by the extracorporeal circuit. Intensive Care Med 1987;13:89-95.[Medline]
  3. Buffolo E, de Andrade CS, Branco JN, Teles CA, Aguiar LF, Gomes WJ. Coronary artery bypass grafting without cardiopulmonary bypass Ann Thorac Surg 1996;61:63-66.[Abstract/Free Full Text]
  4. Calafiore AM, Di Mauro M, Contini M, et al. Myocardial revascularization with and without cardiopulmonary bypass in multivessl diseaseimpact of the strategy on early outcome. Ann Thorac Surg 2001;72:456-463.[Abstract/Free Full Text]
  5. Puskas JD, Thourani VH, Marshall JJ, et al. Clinical outcomes, angiographic patency, and resource utilization in 200 consecutive off-pump coronary bypass patients Ann Thorac Surg 2001;71:1477-1484.[Abstract/Free Full Text]
  6. Roques F, Nashef SAM, Mitchel P, et al. Risk factors and outcome in European cardiac surgeryanalysis of the EuroSCORE multinational database of 19030 patients. Eur J Cardiothorac Surg 1999;15:816-823.[Abstract/Free Full Text]
  7. Nashef SAM, Roques F, Mitchel P, et al. European System for Cardiac Operative Risk Evaluation (EuroSCORE) Eur J Cardiothorac Surg 1999;16:9-13.[Abstract/Free Full Text]
  8. Jasinski MJ, Wos S, Olszowka P, et al. Dysfunction of left ventricle as an indication for off-pump coronary artery bypass grafting Heart Surg Forum 2003;6:E85-E88.[Medline]
  9. AI-Ruzzeh S, Nakamura K, Athanasiou T, et al. Does off-pump coronary artery bypass (OPCAB) surgery improve the outcome in hig-risk patients? A comparative study of 1398 high-risk patients Eur J Cardiothorac Surg 2003;23:50-55.[Abstract/Free Full Text]



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