The relationship between predicted and actual cardiac surgical mortality: impact of risk grouping and individual surgeons

Analysis of mortality in low-risk patients undergoing coronary artery bypass grafting

Aim

The aims of this study were to determine the early mortality rate in low-risk coronary artery bypass graft (CABG) patients and examine the causes of death, to identify problems that could be avoided in future surgeries.

Methods

All low-risk patients (EuroSCORE ≤ 2) who died after CABG were included. Their peri-operative information was meticulously studied by internal and independent external reviewers to identify causes of death, which were classified as: cardiac or non-cardiac; and a further division as: (1) non-preventable, (2) preventable (technical error), and (3) preventable (system error).

Results

Early mortality was 0.93% (24/2 570). Eleven patients (45.8%) were classified as preventable deaths. In six of them the main problem was identified as graft thrombosis, which was secondary to a technical error of either the harvesting or anastomosis of the left internal mammarian artery. There were also five system errors identified as delays in the treatment of an identified and potentially reversible problem.

Conclusions

Correction of technical and system errors, such as harvesting of the left internal mammarian artery, haemostasis during surgery, and establishing standard protocols for the transfer of patients from ward to intensive care units will eventually lead to improvement in both the quality of care and patient outcomes, even in low-risk groups.

Training of Cardiac Surgeons for Bosnia and Herzegovina: Outcomes in Coronary Bypass Grafting Surgery

BACKGROUND

Bosnia and Herzegovina did not have invasive cardiac diagnosis or cardiac surgery before the recent war. With assistance from the United States and Norway, a cardiovascular clinic was developed. This study reports center-specific and surgeon-specific clinical outcomes. Since off-pump coronary bypass grafting surgery was prioritized in the treatment of coronary disease, a comparison was made between operations performed with and without cardiopulmonary bypass.

METHODS

Surgeons and key staff members were trained in the United States. A Norwegian data management system for cardiac surgery was implemented and cases entered after quality review of the data. A total of 1276 patients were entered; operations were performed with cardiopulmonary bypass in 540 and without in 736. The primary surgeon was entered as a variable in an anonymous fashion.

RESULTS

Overall mortality for coronary bypass grafting surgery was 1.6%, and the major complication rate was 4.5%. Patients operated on off-pump received fewer grafts and had a shorter length of stay. Unfavorable outcome was more common in patients when cardiopulmonary bypass was used in the operation. Regression analysis demonstrated that the European System for Cardiac Operative Risk Evaluation (EuroSCORE) and use of cardiopulmonary bypass were predictors of poor outcome. The individual surgeon factor did not impact on outcomes.

CONCLUSIONS

Our study confirms that coronary artery bypass grafting surgery may be performed safely in a poor country in a hospital without experience with cardiac surgery. Selection of talented staff and cooperation with international cardiac centers are crucial. Off-pump coronary artery bypass grafting surgery is suitable for a new center and does not require more training than standard procedures.

Risk stratification for adverse outcome in cardiac surgery

Risk-adjusted outcome prediction is mainly important in two separate fields. The first is quality monitoring: measuring actual versus predicted mortality in an institution allows assessment of the clinical surgical and anaesthesia performance while adjusting for the risk profile of the patients. Without risk stratification, surgeons and hospitals treating high-risk patients will appear to have worse results than others. This may prejudice referral patterns, affect the allocation of resources and even discourage the treatment of high-risk patients. The second field is that of informed consent and clinical decision-making. Risk-adjusted predicted mortality should form an important part of patient and surgeon decisions on whether or not to proceed with surgery. Clearly, no 'perfect' model can be produced as some aspects of mortality will always be related to risk factors not included in the model (e.g. the quality of the distal coronary artery vessels in coronary artery surgery) or due to chance happenings not related to preoperative patient characteristics (such as surgical error). An individual patient will either survive or die after cardiac surgery. Clearly, no scoring system will predict the specific outcome for every patient. However, risk stratification will inform patients and clinicians of the likely risk of death for a group of patients with a similar risk profile undergoing the proposed operation. This information is useful and should form part of the basis on which the patient and surgeon decide whether to proceed.

[Does the EuroSCORE identify patients at minimum risk of mortality from heart surgery?]

INTRODUCTION AND OBJECTIVES

Risk of hospital death is one of the key factors considered by the clinical cardiologist when weighting indications for surgery. Risk estimation scales establish distinct levels of risk in quantitative terms. The aim of the present study was to investigate whether a low EuroSCORE value corresponds to low mortality in our setting.

PATIENTS AND METHODS

During 1999-2000 we prospectively calculated the EuroSCORE for all patients who underwent isolated coronary (CS) or valvular (VS) surgery. We then analyzed intrahospital mortality of patients with a low EuroSCORE. The validation group consisted of patients who underwent surgery in 2001 and obtained a low EuroSCORE.

RESULTS

During 1999-2000 we identified 116 patients (16.2% of all patients treated with isolated CS or CV) with a low EuroSCORE (50 8.6 years; 65% male). Fifty-seven of these patients underwent isolated CS, and 59 of them isolated VS. Intrahospital mortality was zero. In 2001 we identified 59 (16.1%) such patients (49 8.7 years; 68% male), of whom 35 underwent isolated CS and 24 underwent isolated VS. Intrahospital mortality during this period was again zero.

CONCLUSIONS

A low EuroSCORE identifies a population of patients with minimum risk of mortality after isolated coronary or valve surgery. The score may be useful as a sentinel indicator in analyses of the complex issue of quality of cardiac surgery.