The operative techniques and technical components of cardiac surgeries matured over the intervening years since the 1960s when the first operations were performed using cardiopulmonary bypass. Simultaneously, the results of operative intervention for cardiac surgeries improved despite increased acuity of the patient population requiring operation[i]. The same may be fallacious in cardiac surgery, because of the risk paradox. It has been shown, that particularly in high risk patients the superiority of surgical over medical treatment is most pronounced.^1,[ii]

The changing risk profile in cardiac surgical patients over the past decade means, that crude procedural mortality figures are no longer sufficient, either for informed consent by patients, or for the assessment of the quality of care in institutions. The operative mortality is not only important to assess the outcome of patients who survive cardiac operations but also to assess the high morbidity and a poor long-term outcome.^2,3

To address these concerns, many professional organizations looked to measure results of operation by using large databases to identify risk factors and organize patients according to their risk to predict an adverse outcome. It was obvious that risk adjustment is essential for accurate comparison of providers (hospitals and surgeons). In view of mortality associated with surgical intervention in cardiac diseases, it is important to understand hospital mortality and morbidity in the context of preoperative risk to predict the operative outcome which in turn will help in planning the management and counsel the patient pre-operatively.

EuroSCORE (European System for Cardiac Operative Risk Evaluation) is a risk model which allows the calculation of the risk of death after a heart operation. The model asks for 17 variables of information about the patient, the state of the heart and the proposed operation. The simple additive EuroSCORE model is now well established and has been validated in many patient populations across the world. It is easy to use, even at the bedside. It is valuable in quality control in cardiac surgery and gives quite a useful estimate of risk in individual patients by using logistic regression to calculate the risk of death.[iii]

Indian patients undergoing cardiac surgery have different demographics, clinical profile as well as risk profile, compared to the western population. Patients coming to our hospital mainly belong to rural areas with regional diversity across north India. This study has been done on these patients admitted for cardiac surgery.

[i] Sabiston Textbook of Surgery, 18th ed

[ii] Roques, F., Nashef, S. A. M. et al. Risk factors and outcome in European cardiac surgery: analysis of the EuroSCORE multinational database of 19030 patients. European Journal of Cardiothoracic Surgery, 1999, 15, 816–823

[iii] Intra-institutional prediction of outcome after cardiac surgery: comparison between a locally derived model and the EuroSCORE Otto PitkaÈnena,*, Minna Niskanena, Sinikka Rehnbergb, Mikko HippelaÈinenc, Markku Hynynena, European Journal of Cardio-thoracic Surgery 18 (2000) 703±710

We conducted this prospective study in the department of Cardio Thoracic & Vascular Surgery of a tertiary care teaching hospital in North India from April 2014 to March 2016. In our study, total of 100 patients undergoing open-heart surgery with cardiopulmonary bypass were preoperatively assessed using EuroSCORE.

Inclusion criteria- Patients undergoing heart surgery with cardiopulmonary bypass in our institution.

Exclusion criteria- All Paediatric cases. Patients operated on beating heart without cardiopulmonary bypass.

Seventeen risk factors were weighted for the definitive scoring system. There were nine patient-related factors, four factors were derived from the preoperative cardiac status and four depended on the timing and nature of the operation performed. The risk factors, their definitions and the weights allocated to them are detailed in Table 1.

Operation-related factors

Risk factors                                      Definitions                                                                      Weights (Score

Emergency                                         Carried out on referral before the beginning

                                                            of the next working day                                                  2

Other than isolated CABG                Major cardiac procedure other than

                                                            or in addition to CABG                                                   2

Surgery on thoracic aorta For disorder of Ascending, Arch

                                                            or Descending aorta                                                                       3

Postinfarct septal rupture                                                                                                            4

Patient-related factors

Risk factors                                      Definitions                                                                      Weights (Score)

Age                                                     Per 5 years or part thereof over60 years                       1

Sex                                                      Female                                                                              1

Chronic pulmonary disease              Long term use of bronchodilators or steroids for

                                                            lung disease                                                                                    1

Extracardiac arteriopathy Any one or more of the following: claudication,

                                                            carotid occlusion or >50% stenosis, previous or

                                                            planned intervention on the abdominal aorta,

                                                            limb arteries or carotids                                                  2

Neurological dysfunction Disease severely affecting ambulation or

                                                            day-to-day functioning                                                   2

Previous cardiac surgery   Requiring opening of the pericardium                           3

Serum creatinine                >200 mmol/l preoperatively                                                          2

Active endocarditis                           Patient still under antibiotic treatment for

                                                            endocarditis at the time of surgery                                3

Critical preoperative state Any one or more of the following:

Ventricular tachycardia or fibrillation or aborted sudden death, Preoperative cardiac                 3 massage, Preoperative ventilation before arrival in the anaesthetic room,                                           Preoperative inotropic support, Intra-aortic balloon counter-pulsation or                                   Preoperative acute renal failure (anuria or oliguria,<10 ml/h)    

Cardiac-related factors

Unstable angina                  Rest angina requiring i.v. nitrates until arrival

                                                            in the anaesthetic room                                                   2

LV dysfunction                  Moderate or LVEF 30-50%                                                          1

                                                            Poor or LVEF <30                                                                         3

Recent myocardial infarct (<90 days)                                                                                       2

Pulmonary hypertension    Systolic PA pressure >60 mmHg                                   2

• The patients were allocated into three groups depending on the scores they obtained.
• The low-risk group (EuroSCORE 1–2), the medium-risk group (EuroSCORE 3–5), and the high-risk group (EuroSCORE 6 plus).
• Outcome was assessed as:-
  • Alive - alive and discharged from hospital, 30 days from date operation.
  • Dead - died within 30 days from operation or later than 30 days if still in hospital.
  • Wait-patient still in hospital>30 days from operation: records were held and and filled in as alive or dead when appropriate.

Statistical Analysis

At the end of the study, data was collected, compiled and analysed. The record was maintained on Microsoft Excel and SPSS version 16 software was used for statistical analysis. Pearson’s Chi Square test was used to compare two categorical variables, where significance is shown as: p-value <0.05 significant, p-value <0.01 highly significant, p-value <0.001 very highly significant.

Mean age for entire sample was 52.17 yrs. Age of patients was found to be statistically insignificant in determining additive EuroSCORE (p-value >.05). Maximum patients (44%) were found in medium risk group of EuroSCORE of 3-5, while high risk group patients were less than 25% (Fig. 1).

Figure 1- Risk Distribution

The average duration of hospital stay for all patients was 8.85 days. Among the three groups of high risk (mean - 9.79), medium (7.59) and low risk patients (9.87), there was no significant difference in terms of hospital stay. However, in terms of standard deviation, maximum deviation was found in high-risk group (10.88), with minimum to maximum variation ranging between 1 to 54. This can be explained by the fact that most of the patient died in the high-risk group or had a prolonged hospital stay, thus giving maximum range of hospitalization (Table - 2).

Table 2 - Duration of Stay

As mentioned in table – 3, the mean expected death rate was 7.0368 (3.9389-10.134 with 95% confidence interval limits). The observed mortality was 13% with stratification in various risk groups as under:

• Low risk - Expected rate was 1.3119 (1.2169-1.4068) & Observed rate was 0%.
• Medium risk - Expected rate and Observed rates were 2.6750 (2.4159-2.9341) & 2.27% respectively.
• For high risk – The observed rate was 50 % & was much higher than the expected rate which was recorded as 22.661272 % (11.4084-33.9250%)
• The maximum number of deaths were recorded in High risk group in which  EuroSCORE >5. This finding was statistically found to be very highly significant (p-value -.000)

Table 4 - Strongest predictors of postoperative mortality

Although EuroSCORE has long been integrated into clinical practice to support risk stratification and decision-making, its performance may vary across institutions, patient populations, and evolving surgical techniques.[i] Since its introduction in 1999, the original EuroSCORE has been widely adopted for risk stratification, benchmarking, institutional audits, and guiding preoperative discussions with patients and families.[ii] Its longevity reflects both the simplicity of the scoring system and the clinical relevance of its foundational predictor variables, including age, left ventricular function, comorbidities, procedural urgency, and specific operative characteristics. However, over the past two decades, substantial advancements in surgical techniques, perioperative care pathways, myocardial protection strategies, and critical care management have occurred.[iii] At the same time, patient demographics have shifted, with increasing numbers of elderly, frail, and comorbid patients now undergoing cardiac surgery. Within this changing landscape, the performance of the original EuroSCORE model warrants careful re-examination, and our study contributes to this expanding body of evidence.

In our study, the observed predictive accuracy of EuroSCORE underscores the need to continually reassess established risk models to ensure they remain relevant and reliable in contemporary cardiac surgical practice. Of late it has been realised that the additive EuroSCORE model over-predicts mortality in low-risk patients and under predicts mortality in high-risk patients.[iv]^{,[v],[vi],[vii]} This essentially translates into a scenario where the subset of patients who are likely to benefit the most from surgery are denied the chance of being operated upon and vice versa. Because the original EuroSCORE was derived from a cohort with substantially higher baseline mortality, its predicted risks may not correspond well with the outcomes of contemporary practice shaped by enhanced myocardial protection, improved intensive care, and evidence-based perioperative protocols.[viii] Consequently, modern cardiac surgery populations often exhibit mortality rates considerably lower than those predicted by the original EuroSCORE.

The mean age of patients in our study was found to be 52.17 years, while mean age of high-risk group was 56.5 years. This was found to be in concordance with a definite risk criterion in EuroSCORE. However, as far as mortality or hospital stay is concerned, age was not found to be statistically significant in our study. The Indian population is per se at increased risk of coronary artery disease due to visceral obesity, food habits and an increased prevalence of metabolic syndrome.[ix] The same is evident in our study wherein the mean age of patients undergoing surgery was 52 years as against 62 years in European population.

Since the patients undergoing cardiac surgery are young, they are likely to have the lesser number risk factors amongst the mentioned risks in the EuroSCORE model. This is evident from a decreased prevalence of risk factors like chronic obstructive pulmonary disease, extracardiac arteriopathy, elevated serum creatinine, critical preoperative state, recent myocardial infarction, and unstable angina in our patients. The incidence of these risk factors increases with increasing age along with associated diabetes mellitus and hypertension which by themselves are risk factors for coronary artery disease.[x]

While assessing the risk group distribution, 68 % of patients were found medium and high-risk group with 44 % of them being in medium-risk group. The mean hospital stay was 8.85 days with no statistically significant difference in the hospital stay of all three risk groups.

Among the 17 predictors of post operative mortality, elevated serum creatinine level, Critical pre-operative state, emergency surgery other than isolated CABG and LVEF<30% were found to show very highly statistical significance whereas Active endocarditis, unstable angina, post-operative infarct were found to show high statistical significance to determine the outcome after surgery.

Despite the difference in prevalence of risk factors in Indian population, the predicted mortality and observed mortality were almost similar in patients with low risk (Euro SCORE 0-2) and moderate risk (Euro SCORE 3-5). However, in patients with high risk (Euro SCORE > 6), the observed mortality was significantly high.

This is in accordance with previous studies wherein it has been reported that additive Euro SCORE overpredicts mortality in low- and moderate-risk patients and under-predicts mortality in high-risk patients.^10,11

The recognition of these limitations led to the development of EuroSCORE II, intended to update the model with contemporary data and improve calibration.[xi] While EuroSCORE II demonstrates better performance overall, it is not without limitations. Studies have shown variable accuracy across institutions, countries, and patient subgroups.[xii] Consequently, many centers continue to use the original EuroSCORE due to familiarity, historical benchmarking, and simplicity. Our findings reinforce the importance of cautious interpretation when the original EuroSCORE is used in modern practice and highlight the value of complementary risk-assessment methods, including clinician judgment and additional prediction tools.

[i] Michel P, Roques F, Nashef SA, The EuroSCORE project group. Logistic or additive EuroSCORE for high-risk  patients. Eur J Cardiothorac Surg 2003;23:684-7.

[ii] Nashef SA, Roques F, Michel P, et al. European system for cardiac operative risk evaluation (EuroSCORE). Eur J Cardiothorac Surg. 1999;16(1):9–13.

[iii] Thourani VH, Keeling WB, Kilgo P, et al. The impact of evolving practice on outcomes in cardiac surgery. Ann Thorac Surg. 2011;91(4):1131–8.

[iv] Wynne R, Botti M. Postoperative pulmonary dysfunction in adults after cardiac surgery. Heart Lung Circ. 2004;13(1):1–7.

[v] Bridgewater B, Grayson AD, Jackson M, Brooks N, Grotte GJ, Keenan DJ, et al. Surgeon specific mortality in adult cardiac surgery: Comparison between crude and risk stratified data. BMJ 2003;327:13-7.

[vi] Karthik S, Srinivasan AK, Grayson AD, Jackson M, Sharpe DA, Keenan DJ, et al. Limitations of additive EuroSCORE for measuring risk stratified mortality in combined coronary and valve surgery. Eur J Cardiothorac Surg 2004;26:318-22.

[vii] Gogbashian A, Sedrakyan A, Treasure T. EuroSCORE: A systematic review of international performance. Eur J Cardiothorac Surg 2004;25:695-700.

[viii] Brown ML, Schaff HV, Sarano ME, et al. Improvements in cardiac surgical outcomes. Circulation. 2008;118(14):1497–505.

[ix] Shaukat N, deBono DP. Are Indo-origin people especially susceptible to coronary artery disease. Postgrad Med J 1994;70:315-8.

[x] Turner RC, Millns H, Neil HA, Stratton IM, Manley SE, Matthews DR, et al. Risk factors for coronary artery disease in non-insulin dependent diabetes mellitus: United Kingdom prospective diabetes study (UKPDS:23). BMJ 1998;316:823

[xi] Chalmers J, Pullan M, Mediratta N, et al. A comparison of EuroSCORE II and original EuroSCORE. Heart. 2013;99(8):566–71.

[xii] Karthik S, Srinivasan AK, Grayson AD, et al. Validation of EuroSCORE II. Interact Cardiovasc Thorac Surg. 2014;19(3):468–74.

Euro SCORE is one of an established scoring systems which is a simple, objective, and valuable tool for risk prediction in adult cardiac surgery and performs well in low- and medium-risk Indian patients. The strongest determinants of mortality were renal dysfunction, critical preoperative status, low LVEF, high ischemic burden on heart, complexity of surgeries and in emergency over elective cases. However, it underestimates mortality in high risk groups. While we have assessed the performance of the original EuroSCORE, another EuroSCORE II had been launched in 2011 which we did not use as it had not yet undergone extensive external validation.

Though we conducted a single center study, but continued multicenter validation and periodic recalibration will be essential to ensure that EuroSCORE evolves into a reliable tool for modern cardiac surgical risk assessment. Until such evidence is available, both clinicians and researchers should interpret EuroSCORE predictions with appropriate prudence, and consider them complementary rather than definitive indicators of operative risk.