Thorac cardiovasc Surg 2014; 62(07): 634-636
DOI: 10.1055/s-0034-1383819
Letter to the Editor
Georg Thieme Verlag KG Stuttgart · New York

Clinical Performances of the EuroSCORE II Risk Stratification Model Compared with Old EuroSCORE Models

Dusko Nezic
1  Department of Cardiac Surgery, “Dedinje” Cardiovascular Institute, Belgrade, Serbia, Serbia
,
Milorad Borzanovic
1  Department of Cardiac Surgery, “Dedinje” Cardiovascular Institute, Belgrade, Serbia, Serbia
› Author Affiliations
Further Information

Publication History

11 May 2014

19 May 2014

Publication Date:
01 August 2014 (online)

We read with great interest the article by Velicki et al[1] regarding external validation of the EuroSCORE (European System for Cardiac Operative Risk Evaluation) II performances compared with original additive and logistic EuroSCORE models. Since the original EuroSCORE has been introduced in daily cardiac surgical practice in 1999,[2] it has been used as a measure of a perioperative risk and as a benchmark for the assessment of the quality of adult cardiac surgery in more than 1,300 formal citations in the medical literature.[2] Although both additive and logistic version of EuroSCORE have remained a very good discriminatory power, suspicions were raised that model may now be inappropriately calibrated for current cardiac surgery.[2] Therefore, the old EuroSCORE was renewed into EuroSCORE II (database of more than 22,000 consecutive patients undergoing adult cardiac surgery over a 12-week period [May to July] in 2010) to optimize its discriminatory power and especially its calibration.[2] A note of caution occurred about the study period. Although EuroSCORE II was developed and validated on data from patients who underwent surgery between May and July 2010, there are doubts that EuroSCORE II can lose external validity if applied to patients who underwent cardiac surgery before that period. From that point of view, article by Velicki et al[1] is indeed a very nice contribution.

However, there are few facts which have to be clarified. The authors stated that their study[1] examined the data of 1,247 consecutive patients who had undergone major cardiac surgery at their institute over a 14-month period since the beginning of 2012. Major cardiac surgery has been defined by EuroSCORE II authors[2] as follows: coronary artery bypass grafting (CABG) surgery, valve repair or replacement, replacement of part of the aorta, repair of a structural defects, resection of cardiac tumor, and, of course, any form of combined major surgery. How so, that in 1,247 consecutive patients there were no patients with surgery of the thoracic aorta? In EuroSCORE II database almost 2,000 patients (7.3% of the sample) with thoracic aorta surgery[2] were included. We would understand such an approach if the authors wanted to compare EuroSCORE models with the Society of Thoracic Surgeons' (STS) risk model (STS risk model recognizes only CABG surgery, single valve surgery—aortic valve replacement or mitral valve replacement/repair, and combined CABG and single valve surgery). Although they did not perform such a comparison and if patients with thoracic aorta surgery were deliberately excluded, it would be beneficial to know the reasons for that.

The patient-related and surgery-related data were summarized in Table 1 of the article by Velicki et al.[1] In the row entitled—left ventricular ejection fraction (EF) %—we can find that the median left ventricular EFs were 55.00 (all patients, range 46–60), 55.00 (coronary surgery, range 46–60), 60.00 (valvular surgery, range 50–63), and 54.00 (combined surgery, 40–60). Does it mean that only patients with left ventricular EF of 40% and greater were operated? Although all consecutive patients were included irrespective of the priority level (elective, urgent, emergency, salvage), is it possible that there were no patients with left ventricular EF less than 40%? According to World Health Organization data (link—http://apps.who.int/bmi/index.jsp?introPage=intro_3.html), obese persons have body mass index (BMI, kg/m2)  ≥  30, with obese class I ranging from 30.00 to 34.99, and obese class Ia ranging from 30.00 to 32.49. The same group of authors has recently reported impact of obesity on early mortality after CABG surgery.[3] That cohort of patients (operated during 2010) had 791 patients, and more than 30% of them (239 patients) were obese (BMI  ≥  30 kg/m2). Furthermore, from that article (Fig. 1 of the article by Velicki et al—number of patients in relation to a BMI value), it can be calculated that almost 180 patients (more than 22%) had a BMI  ≥  31 kg/m2. Although reported BMI for CABG patients in present study[1] was 27.72  ±   2.52 kg/m2, there is only 2.5% (distribution according to Gaussian curve) of current CABG cohort with BMI greater than 31 kg/m2. Is it possible that obese patients belonging to obese class Ib, II, or III undergoing CABG surgery have disappeared? It would be perfect if preventive measures and education of the patients influenced on this, more than eightfold reduction of obese patients category undergoing CABG surgery. However, regarding the presented data of left ventricular EF and patients BMI, we wonder whether there is a possibility that some data were incorrectly entered into Table 1 of the article by Velicki et al.[1]

The authors divided observed population into quartiles according to the EuroSCORE II values. Therefore, they suggested[1] that low-risk patients appeared to be those with predicted risk of 0 to 0.79% (which is incorrect, as the lowest EuroSCORE II predicted risk is 0.5%), mild-risk patients are those with predicted risk of 0.8 to 1.27%, and moderate-risk patients are those with predicted risk of 1.28 to 2.34%. We can hardly agree that all patients with EuroSCORE II predicted risk of more than 2.35% are high-risk patients. Therefore, we do believe that somewhat different grading of low, mild, moderate, high, and very high classes of EuroSCORE II risk prediction should be created.