30 August 2010
Dan Lindblom MD, PhD, Associate professor
Department of Cardiothoracic Surgery and Anesthesiology
+46 8 517 70824 (office)
+46 70 48 40172 (cell phone)
[email protected]Medical coordinator Gina Portella
Executive director Gino Strada
Coordinator Rossella Miccio
Dr Fadwa GassimDr Alessandro Salvati
Report on the EuroSCORE 2010 update at Salam Centre, Khartoum, Sudan
Background
EuroSCORE (European System for Cardiac Operative Risk Evaluation) is a system for preoperative risk stratification for patients undergoing cardiac surgery. It is based on data on 19030 patients from 128 centres in 8 European countries operated on between September-November 1995. The scoring system was presented 1999 and has been widely used in Europe since then and has largely replaced older scoring systems such as Parsonnet and Higgins. In USA a more complicated system (the Society of Thoracic Surgeons system) is the most widely used system for risk scoring.
As the data and outcomes for EurosSCORE were collected 15 years ago and with a hopefully ongoing improvement of cardiac surgery procedures since then, it can be assumed that EuroSCORE today overestimates the operative risk. There are in fact a few published papers indicating that the risk today is considerably smaller than EuroSCORE predictions.
To update and recalibrate the risk stratification system a new data collection was performed from May 3- July 25, 2010. Approximately 300 centres from all over the world have participated in this up-date (“EuroSCORE goes global”), including two centers from Africa.
It is anticipated that this will provide 40000 patients for analysis (twice as many as in the original data base) which will enable an equally robust scoring system even if the mortality rates in 2010 would have been reduced by half since 1995.
Patients younger than 18 years are not included in the EuroSCORE database, otherwise all patients undergoing heart surgery, on-pump or off-pump, are included.
The EuroSCORE organisation has asked for in-hospital mortality for all patients, and 30-days mortality when possible. In addition they would like to have 90 days mortality from centres that can provide this.
2 (6)
EuroSCORE statistical methods
Risk factors for early mortality are analysed by multiple regression analysis. The predicted mortality (%) is calculated as: e (βo +Σβ i Xi) / 1+ e (βo + Σβi Xi) where e is the natural logarithm (= 2.718...), βo is a constant in the logistic regression (= -4.789594) and βi is the coefficient for the risk variable Xi.
This calculation can be performed easily on the on-line calculator at
www.euroscore.org.
A simplified calculation (“standard” or “additative”) EuroSCORE is also available where the calculations can be performed without computer or calculator.
The logistic and standard EuroSCORE predictions are similar in low- and medium- risk patients, whereas the standard Euroscore is underestimating the risk in high- and very high-risk patients. As mentioned above, both systems probably overestimate the risk in current practice, at least for low- and medium-risk patients.
Risk definition
1.
Low risk Additative Euroscore 0-2
2.
Medium risk Additative Euroscore 3-5
3.
High risk Additative Euroscore ≥ 6
Data collection
The data collection for the 2010 update at Salam Centre was performed in a prospective way, starting to collect data for each patient as soon as they where on the OT list. Data were extracted from preoperative files at the out-patient department (NYHA classification, echo findings etc), from files at the ward (creatinine values), from the surgical report (type of procedures, cross-clamp time etc) and from discharge notes. Finally a 30-day follow-up was conducted on all patients. No patient was lost during this early follow-up period.
Data collection was mainly handled by
Doctor Fadwa Gassim and Doctor Alessandro Salvati at the centre. I participated in this work during the first 3 weeks and we had consensus discussions on most patients during this period. After the closing date I returned for a few days (July 30-August 2) to the centre to meet with
Doctors Gassim and Salvati for further discussions. After the 30-days follow-up period (closing August 24) I personally reviewed all files on-line to check for inaccuracies.
All data were entered on-line at EuroSCORES web-site.
Number of patients operated
During the 12 week data collection period 236 patients underwent cardiac surgery at the centre. This corresponds to an annual volume of more than 1000 patients.
107 patients were younger than 18 years and were not included in the data collection according to EuroSCORE rules, which leaves 129 patients for analysis.
3 (6)
Demographics
The mean age was 30 years (range 18-59) and 60 % were females. As many patients does not know their exact birthday but they usually know their age we have entered birthday as 1st of July (the midpoint of the year) for patients with missing data. This was done after discussion with Dr S. Nashef at EuroSCORE. The proportion of females in higher than in the total database for the Salam Centre (2007-2010) where 52 % were females. As only patients >17 years were included the mean age is higher than in the total database (26 years).
Type of procedures
112 patients (87 %) underwent valve procedures (in two patients combined with replacement of the ascending aorta)
11 adult patients (9 %) underwent surgery for congenital heart disease
6 patients (5 %) underwent coronary artery bypass surgery
Valve surgery
Out of 112 valve surgery patients 64 (57 %) underwent single valve procedures (mitral valve replacement in 40, mitral valve repair in 7 and aortic valve replacement in 17 patients (two also had ascending aortic replacement).
48 valve patients (43 %) underwent multiple valve surgery including 9 (8 %) with triple valve procedures.
Multiple valve procedures were;
29 double (aortic and mitral) valve replacement,
o
in 9 patients combined with tricuspid annuloplasty
15 mitral valve replacement combined with tricuspid valve repair
2 aortic valve replacement combined with mitral repair
2 mitral valve repair combined with tricuspid valve repair
Nine (8 %) of these valve procedures were re-do´s.
Procedures for congenital disease
Out of 12 adult patients undergoing surgery for congenital heart disease, 4 had Tetralogy of Fallot, 3 had subaortic stenosis, 1 had ASD, 1 had anomalous pulmonary venous return and 3 patients had off-pump procedures for aortic coarctation and patent ductus.
There were no re-do´s in this group of patients.
Specific risk factors
Age
Euroscore assigns 1 risk point ( ≈ 1 % added risk of mortality) for every 5-year period over 60 years of age. Age is the most important risk factor in most surgical series from Europe and USA. No patient in this group was 60 or older so age was not a risk factor in this group of patients.
4 (6)
Left ventricular function
Euroscore assigns 1 risk point for LVEF between 30-50 % and 3 points for LVEF < 30 %. Only six patiens out of 129 (5 %) had a LVEF less than 50 %, and one had an LVEF less than 30 %.
Pulmonary hypertension
Pulmonary hypertension is a serious risk factor adding 2 risk points. This factor is not very prevalent in surgical series from Europe or USA but is common among patients with longstanding mitral valve disease. In this series PA systolic pressures (as measured by transthoracic echocardiography preoperatively) were available in 105 of 129 (81 %) patients. In the remaining 24 patients it was probably normal in most, as this group mainly consists of patients undergoing surgery for ischemic or congenital heart disease, some aortic valve replacements and only one mitral valve replacement.
52 of 105 (50 %) patients had a PA pressure of 60 mm Mercury or more. The mean systolic PA pressure in those with available figures was 59,6 mm Mercury (range 20-145).
Among 112 patients undergoing valve procedures PA pressures were available in 100 (89 %) and 51 (51 %) patients had a PA pressure of 60 mm Mercury or more. The mean systolic PA pressure in those with available figures was 61,0 mm Mercury (range 20-145).
Among 93 patients undergoing a mitral valve procedure (with or without aortic or tricuspid valve procedures) PA pressures were available in 90 (98 %) and 51 (57 %) patients had a PA pressure of 60 mm Mercury or more. The mean systolic PA pressure in those with available figures was 65 mm Mercury (range 20-145).
Critical preoperative state
Critical preoperative state is defined as any one or more of the following: ventricular tachycardia or fibrillation or aborted sudden death, preoperative cardiac massage, preoperative ventilation before arrival in the anaesthetic room, preoperative inotropic support, intraaortic balloon counterpulsation or preoperative acute renal failure.
Four patients with preoperative inotropic support (in one also preoperative ventilation) were classified as “critical”.
Urgency of the operation
Operations performed as a true emergency adds 2 points. Given the admission criteria for Salam centre true emergencies are very uncommon, and only one patient in this series was classified as an emergency procedure.
Other than CABG
Most surgical series from Europe and USA are dominated by CABG patients. For anything else than CABG (or any combination with CABG) 2 points are added. In the present series all but six patients underwent “other than CABG”
Previous cardiac surgery
A prior cardiac procedure adds 3 risk points. Nine patients (7 %) in the present series were re-
5 (6)
do´s (all were valve procedures)
Risk profile at the Salam centre
Given the low age of our patients and thus less comorbidities, but on the other hand with a majority of patients undergoing surgery other than CABG and with a high prevalence of pulmonary hypertension our patients can be stratified in different risk groups;
Low risk (Additative Euroscore 0-2) 34/129 (26 %)
Medium risk (Additative Euroscore 3-5) 82/129 (64%)
High risk (Additative Euroscore ≥ 6) 13/129 (10 %)
The proportion of patients with high risk is lower than what is reported from centres in Europe and USA which is due to the low mean age of our patients and the very low number of true emergencies.
Mortality
Two patients (1,6 %) died in hospital. No deaths occurred between discharge and 30 days.
One death occurred in an adult Tetralogy patient and the other in an emergency redo for a thrombosed mitral prosthesis.
The mortality in patients undergoing valve surgery was thus one in 112 patients (0,9 %)
“Expected mortality”
The “expected mortality” as calculated with the “old” EuroSCORE in the total group of patients (n=129) was 3,8 % (additative EuroSCORE) and 3,5 % (logistic EuroSCORE), respectively.
The “expected mortality” for patients undergoing valve surgery (n=112) was 4,0 % (additative) and 3,8 (logistic), respectively.
Summary
Data collection has been carried out prospectively with extremely few missing data points. The 30-days follow-up is 100 % complete.
40000 patients from 300 centres are expected to be entered into the 2010 EuroSCORE update with a mean of 133 patients per centre. One hundred and twenty-nine patients reported from Salam is thus a good number!
This group of patients seems to be a representative sample from the overall experience at Salam centre with one exception; the proportion of female patients was higher in this group, 60 %, as compared to the total group, 52 %. As no patients under 18 years of age were included the mean age is higher in this series (30 years v 26 years).
The proportion of multiple valve procedures (43 %) is similar to our total experience, whereas the proportion of triple valve procedures (8 % v 6 %) and redos (8% v 5 %) is
6 (6)
slightly higher in the present group.
It is not possible to do a formal statistical analysis of observed versus expected mortality as the number of patients (and deaths) is to low. However, with an early mortality among valve patients of only 0,9 % (1/112) as compared with the “expected mortality” of 3,8-4,0 % our results in this series are outstanding. Also the mortality rate in the total group (n=129, mortality 1,6 %) compares very favourably with the “expected mortality” of 3,5-3,8 %. I think that we can congratulate the Centre (and ourselves) to these good results!
If possible, we should collect 90-days follow-up (dead or alive only) on these patients which is a non-obligatory request from the EuroSCORE organisation. I would like your opinion on the feasibility of this.
Finally, it has been a great pleasure for me personally to participate in this update and I think that it is good for the centre to be engaged in this type of research and follow-up work.
Best personal regards to all of you
Dan