Comparison of 19 pre-operative risk stratification models in open-heart surgery

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1 Euroen Hert Journl (2006) 27, doi: /eurhertj/ehi720 Clinicl reserch Crdiovsculr surgery Comrison of 19 re-oertive risk strtifiction models in oen-hert surgery John Nilsson 1 *, Lrs Algotsson 2, Peter Höglund 3, Crsten Lührs 1, nd John Brndt 1 1 Dertment of Crdiothorcic Surgery, Hert nd Lung Centre, Lund University Hositl, SE Lund, Sweden; 2 Dertment of Crdiothorcic Anesthesiology, Hert nd Lung Centre, Lund University Hositl, Lund, Sweden; nd 3 Cometence Centre for Clinicl Reserch, Lund University Hositl, Lund, Sweden Received 23 August 2005; revised 2 November 2005; cceted 16 December 2005; online ublish-hed-of-rint 18 Jnury 2006 See ge 768 for the editoril comment on this rticle (doi: /eurhertj/ehi792) KEYWORDS Mortlity; Risk fctors; Sttistics; Surgery; Survivl Aims To comre 19 risk score lgorithms with regrd to their vlidity to redict 30-dy nd 1-yer mortlity fter crdic surgery. Methods nd results Risk fctors for tients undergoing hert surgery between 1996 nd 2001 t single centre were rosectively collected. Receiver oerting chrcteristics (ROC) curves were used to describe the erformnce nd ccurcy. Survivl t 1 yer nd cuse of deth were obtined in ll cses. The study included 6222 crdic surgicl rocedures. Actul mortlity ws 2.9% t 30 dys nd 6.1% t 1 yer. Discrimintory ower for 30-dy nd 1-yer mortlity in crdic surgery ws highest for logistic (0.84 nd 0.77) nd dditive (0.84 nd 0.77) Euroen System for Crdic Oertive Risk Evlution () lgorithms, followed by (0.82 nd 0.76) nd (0.82 nd 0.76) scoring systems. None of the other 15 risk lgorithms hd significntly better discrimintory ower thn these four. In coronry rtery byss grfting (CABG)-only surgery, followed by New York Stte () nd risk score showed the highest discrimintory ower for 30-dy nd 1-yer mortlity. Conclusion,, nd risk lgorithms showed suerior erformnce nd ccurcy in oen-hert surgery, nd,, nd in CABG-only surgery. Although the models were originlly designed to redict erly mortlity, the 1-yer mortlity rediction ws lso resonbly ccurte. Introduction Desite technologicl dvncements, oen-hert oertions still crry risk of mortlity nd morbidity. To id in the selection of tients for crdic surgery, severl riskscoring systems hve been develoed during the lst decdes. These im to estimte the risk of eri-oertive deth, bsed on the occurrence of different risk fctors. Oertive mortlity is lso incresingly used s n indictor of the qulity of crdic surgery. 1 To mke n ccurte comrison between different institutions or surgeons, mortlity dt must be djusted to the risk rofiles of the tients. 2,3 Differences between the vilble risk lgorithms regrding score design nd the tient oultion on which the score develoment ws bsed could influence their ccurcy nd erformnce. Idelly, risk model should be useful for outcome rediction t different surgicl centres, both t the institutionl level nd for individul tients. 4 Oertive mortlity is the outcome vrible most commonly used s qulity indictor, but long-term mortlity my be more relevnt from tient ersective. * Corresonding uthor. Fx: þ E-mil ddress: john.nilsson@thorx.lu.se A few comrtive studies of different risk lgorithms exist. 4 8 However, the reltive erformnce of the riskscoring systems currently used remins uncler. The urose of this study ws to comre 19 oen-source risk score lgorithms with regrd to their vlidity to redict 30-dy nd 1-yer mortlity fter crdic surgery in lrge single-institution tient oultion. Methods Study design nd tients The study ws roved by the Ethics Committee of the Medicl Fculty t Lund University. Risk fctors for ll dult tients undergoing hert surgery t the University Hositl of Lund between Jnury 1996 nd Februry 2001 were rosectively collected when the tients were dmitted to the Dertment of Crdiothorcic Surgery. The tient record form contined totl of 248 vribles (80 re-, 106 intr-, nd 62 ost-oertive) bsed on the Society of Thorcic Surgeons (STS) 9 tient record form. The dt ws stored in locl dult crdic surgery dtbse. Dt collection nd risk-score clcultion From the totl of 248 vribles, those corresonding to the risk fctors in the different risk models were selected. Thus, subset & The Euroen Society of Crdiology All rights reserved. For Permissions, lese e-mil: journls.ermissions@oxfordjournls.org Downloded from htts://cdemic.ou.com/eurhertj/rticle-bstrct/27/7/867/436822

2 868 J. Nilsson et l. of 104 of the re- nd intr-oertive vribles were imorted into the sttisticl softwre ckge, together with 30-dy nd 1-yer mortlity for the oultion. Missing vlues were relced using the robbility imuttion technique 10 before the risk score ws clculted. The robbility imuttion technique substitutes conditionl robbilities for missing covrite vlues when the covrite is qulittive. The risk score for ech lgorithm ws clculted for every tient ccording to the ublished definitions (Tble 1). Follow-u The vitl sttus t 1 yer fter the oertion ws obtined for ll tients from the Poultion nd Welfre Sttistics Sweden, Sttistisk Centrlbyrån, Stockholm, Sweden, s ws the dte nd cuse of mortlity. Sttisticl nlysis Mens (+SD) were used to describe the continuous vribles, nd frequencies were clculted for ctegoricl vribles. Scoreredicted oertive mortlity (deth within 30 dys of oertion) ws clculted using the men score from the different risk models, excet for the lgorithm where the ublished score-mortlity tble 11 ws used. Receiver oerting chrcteristics (ROC) curves were used to describe the erformnce nd redictive ccurcy for the different lgorithms. 12 The discrimintory ower, i.e. the c-index, ws evluted by clculting the res under ROC curves. 13 The res under curves re resented with 95% confidence limits. An re of 1.0 under the ROC curve indictes erfect discrimintion, wheres n re of 0.50 indictes comlete bsence of discrimintion. Any intermedite vlue is quntittive mesure of the bility of the risk redictor model to distinguish between survivors nd non-survivors. To comre the res under the resulting ROC curves (used s n index for the redicted vlue), the non-rmetric roch described by DeLong et l. 14 ws used. The ROC re for ech risk lgorithm ws systemticlly comred with the ROC re of the other 18 lgorithms. The numbers of lgorithms with significntly lrger or smller ROC re ws then comuted. The robbility significnce level ws djusted for the effect of multile comrisons using Sidk s method. Grhs nd sttisticl nlyses were erformed using the Intercooled Stt version 9.0 (2005) sttisticl ckge (SttCor LP, College Sttion, TX, USA) nd GrhPd Prism 4b, 2004 for Mc OS X, GrhPd Softwre, Inc., USA. Results Ptient oultion Between Jnury 1996 nd Februry 2001, 6499 consecutive hert oertions were erformed on 6414 tients. During the eriod Jnury Mrch 1998, dtbse service nd ugrde resulted in missing vlues in 30% of the dt oints. All oertions (n ¼ 277) from this eriod were excluded from the study. Thus, 6153 tients, undergoing 6222 oertions, were included in the nlysis. In 2% of the totl dt oints, missing vlues were relced using the robbility imuttion technique. 10 There ws ccurte documenttion of dt including mortlity nd cuse of deth in ll cses, nd no tient ws lost to follow-u. The verge ge ws yers (rnge 18 95). The mjority of tients were men (72%). A coronry rtery byss grfting (CABG)-only oertion ws erformed in 4351 cses (70%), 1340 (22%) cses hd vlve rocedure with or without CABG surgery, nd 531 (8%) were miscellneous rocedures, e.g. ost-infrction setl ruture (37 cses), ortic neurysm or dissection (209 cses), nd crdic trnslnttion (78 cses). Previous crdic surgery hd been erformed in 457 cses (7.3%). Seventyeight tients (1.3%) were in crdiogenic shock t the strt of the oertion nd 628 (10%) were oerted within 24 h fter ccetnce for surgery (emergency surgery). The ctul 30-dy mortlity ws 2.9% (n ¼ 180) nd the 1-yer mortlity ws 6.1% (n ¼ 377). Tble 1 Synosis of originl dt of 19 risk score lgorithms Region Yer of dt collection Yer of ubliction Number of tients (centers) Risk vribles ROC re Amhiscore 23 Netherlnds (1) Cbdel,24 Finlnd (1) Clevelnd clinic 25 USA (1) 13 N/A (dd.) 26 Euroe (128) (log.) 27 Euroe (128) Frnce (42) ,29 USA (1) ,3,30 USA (33) NNE,11 USA (N/A) 8 N/A 31 Cnd (9) Prsonnet 32 USA (1) 16 N/A Prsonnet (mod.) 33 Frnce (42) Sin (7) 11 N/A,35 Cnd (2) (mod.),36 Cnd (1) 9 N/A Trembly 37 Cnd (1) 8 N/A Tumn 38 USA N/A (1) 10 N/A UK ntionl score,5 UK (2) Veterns Affirs,39 USA (43) 10 N/A Add, dditive; log, logistic; mod, modified; NNE, ; N/A, not vilble. risk score lgorithm is lso known s Higgins score, NNE s Americn College of Crdiology/Americn Hert Assocition (ACA/AHA) score, nd s Provincil Adult Crdic Cre Network (PACCN) score. Algorithms develoed for CABG-only surgery. Downloded from htts://cdemic.ou.com/eurhertj/rticle-bstrct/27/7/867/436822

3 Comrison of 19 re-oertive risk strtifiction models in oen-hert surgery 869 Performnce nd redictive ccurcy for the lgorithms The discrimintory ower (i.e. the re under the ROC curve) for 30-dy mortlity nd 1-yer mortlity ws highest for the logistic (0.84 nd 0.77) nd dditive (0.84 nd 0.77) Euroen System for Crdic Oertive Risk Evlution () lgorithms, followed by the (0.82 nd 0.76) nd the (0.82 nd 0.76) scoring systems (Figures 1 nd 2). None of the other risk lgorithms hd significntly better discrimintory ower (lrger ROC re) thn these four (Figure 3). In the subnlysis with CABG-only tients, the discrimintory ower for the two lgorithms were highest, followed by the New York Stte () nd risk lgorithm (Tble 2). The mortlity redictions of the different scoring systems re shown in (Figure 4). Follow-u The most common cuse of deth within 30 dys ws crdiovsculr disese (n ¼ 163, 91%), followed by cerebrovsculr disese (n ¼ 3, 1.7%), mlignnt neolsm (n ¼ 3, 1.7%), nd chronic lower resirtory disese (n ¼ 2, 1.1%). Crdiovsculr disese ws lso the most common cuse of deth within 1 yer (n ¼ 280, 74%), followed by mlignnt Figure 2 The ROC curves. The sensitivity of rediction of 30-dy mortlity vs. 1-secificity for the 19 risk lgorithms is lotted. The solid line reresents the bsence of discrimintion. Oen-hert surgery (n ¼ 6222). Figure 1 The ROC re (dimonds) with 95% confidence intervls (horizontl brs) for 30-dy mortlity nd 1-yer mortlity. (A) 30-dy mortlity nd (B) 1-yer mortlity. Oen hert surgery (n ¼ 6222). See Tble 1 for bbrevitions. Figure 3 Comrison of the ROC re for different risk lgorithms. For ech risk scoring system (left y-xis), the number of risk lgorithms with significntly (P, 0.05) lrger (blck br) or smller (grey br) ROC re re shown. (A) 30-dy mortlity nd (B) 1-yer mortlity. Oen-hert surgery (n ¼ 6222). See Tble 1 for bbrevitions. Downloded from htts://cdemic.ou.com/eurhertj/rticle-bstrct/27/7/867/436822

4 870 J. Nilsson et l. Tble 2 ROC re for the five risk lgorithms with best erformnce nd ccurcy in CABG-only surgery (n ¼ 4351) 30-dy mortlity ROC re (95% CI) 1-yer mortlity ROC re (95% CI) (logistic) 0.86 ( ) 0.75 ( ) (dditive) 0.85 ( ) 0.75 ( ) 0.84 ( ) 0.75 ( ) 0.84 ( ) 0.75 ( ) Prsonnet (modified) 0.84 ( ) 0.73 ( ) risk score lgorithm is lso known s Higgins score. Figure 4 Observed 30-dy mortlity with 95% confidence intervls (verticl lines) in comrison to score-redicted 30-dy mortlity (dimonds) with 95% confidence intervls (horizontl brs). (A) All oen-hert surgery nd (B) CABG-only surgery. Asterisk denotes the redicted mortlity clculted from ACC/AHA score mortlity tble 11 secified for CABG-only surgery. See Tble 1 for bbrevitions. neolsm (n ¼ 22, 5.8%), cerebrovsculr disese (n ¼ 16, 4.2%), chronic lower resirtory disese (n ¼ 10, 2.7%), nd seticemi (n ¼ 10, 2.7%). For ech risk lgorithm, the ROC res for crdiovsculr-relted (n ¼ 163) nd totl 30-dy mortlity (n ¼ 180) were lmost identicl (difference or less). The discrimintory ower for crdiovsculrrelted 1-yer mortlity (n ¼ 280) incresed by roximtely 0.03 for ll 19 lgorithms comred with the discrimintory ower for totl 1-yer mortlity (n ¼ 377) (logistic Euro- SCORE 0.80, dditive 0.80, 0.79, nd 0.78). However, it did not chnge their reltive order of discrimintory ower. Discussion The urose of this study ws to comre 19 commonly used crdic surgicl risk scores with regrd to their vlidity in lrge single-institute tient oultion. The results show tht four of the lgorithms hd suerior erformnce nd ccurcy to redict 30-dy nd 1-yer mortlity, exressed s discrimintory ower, comred with the other 15 lgorithms. Desite the fct tht ll of the lgorithms were designed to redict erly mortlity, they lso redict 1-yer mortlity well, esecilly when the cuse of deth ws crdiovsculr disese. Most lgorithms overestimted the 30-dy mortlity in this tient oultion. The sme finding hs been reorted in other studies. 4,6 Rther thn reflecting weknesses in the risk score lgorithm, these findings re robbly exlined by differences in tient mix nd temorl eriods comred to the originl dtbses used for develoment of the lgorithms. 6 Prediction of mortlity rte in the CABGonly subgrou ws lmost erfect using the Northern New Englnd nd lgorithms, which re both for use in CABG surgery nd newly develoed. The otentil of ROC curves in medicl dignostic testing ws recognized s erly s Even if comrison of ROC curves in sttisticlly vlid fshion to evlute models remins controversil, the ROC curve is currently the best develoed sttisticl tool for describing erformnce. 12 The model, which hd the highest discrimintory ower, hs been shown to work well to redict 30-dy mortlity in mny Euroen countries 16 nd in the United Sttes. 17 It comred fvourbly with the STS risk strtifiction lgorithm 7 (which is not oen source nd ws therefore not included in the resent nlysis). Recently, it ws demonstrted tht could redict intensive cre unit sty nd costs of oen-hert surgery. 18 The Clevelnd Clinic model hs lso shown high discrimintion to redict erly mortlity. 8 An imortnt finding in the resent study is tht these lgorithms could be used lso to redict longterm mortlity (1 yer), esecilly for crdiovsculr deths. Erlier studies hve comred the erformnce of different risk lgorithms to redict 30-dy mortlity, 4,6,8 but hve not shown significnt differences in erformnce nd ccurcy. This my be exlined by smller tient mterils. 6,8 The redictive ccurcy of different risk scoring systems my be influenced by numerous fctors, such s differences in vrible definitions, mngement of incomlete dt fields, surgicl rocedure selection criteri, nd geogrhicl differences in tient risk fctors. The revlence of risk fctors in tients referred for hert surgery my lso chnge over time. Difficulties thus rise when comrison of the ccurcy nd redictive ower of lrge dtbses re ttemted. However, ROC nlysis is robust technique for such comrisons. Imortntly, the shes of the ROC curves were similr mong the comred risk models (Figure 2), mking direct comrison ossible. 12 Murhy- Filkins et l. 19 showed tht n increse u to five times of Downloded from htts://cdemic.ou.com/eurhertj/rticle-bstrct/27/7/867/436822

5 Comrison of 19 re-oertive risk strtifiction models in oen-hert surgery 871 low-frequency vrible (for exmle, due to difference in vrible definition) did not recibly chnge the model fit. All surgicl rocedures were included in the study, irresective of the number of oertions the tients underwent. Thus, tient could rticite two or more times in the nlysis. This could be debted, s deendence of the dt tht rises from multile rocedures erformed within tient my occur. An lterntive would be to include only the first rocedure for ech tient. A subnlysis using this roch (n ¼ 6153) showed only very smll differences in the ROC re for the different risk lgorithms (in verge 0.001). A drwbck of excluding tients hving second rocedure during the study eriod is tht some high-risk cses will be eliminted from the nlysis. Regrdless of which method used, the differences cused by this deendence ws negligible, most likely due to the smll number of tients (1%) who hd more thn one rocedure. The robbility imuttion technique, used in this study, hs been shown to work well in rognostic fctor studies. 20 Another strtegy to hndle incomlete dt is to exclude the tients with missing vlues from nlysis, but becuse missing vlues re more likely in emergent highrisk tients, this could result in bis. Geogrhicl differences in the occurrence of tient risk fctors my hve influenced the design of different riskscoring systems, but do not seem to influence the resent results. The best-erforming risk scores in this study were develoed in two different geogrhicl res: Euroe nd the USA. Eight of the included risk lgorithms (Cbdel,,,,, (modified), UK ntionl score, nd Veterns Affirs) were originlly designed to redict erly mortlity in CABG-only tients, which lso could ffect the redictive ccurcy. A subnlysis of CABG-only tients in this mteril identified the sme two risk-scoring systems with the lrgest ROC res ( dditive nd logistic), followed by the nd the risk-scoring systems. The smller ROC re for the 1-yer thn for the 30-dy mortlity rediction ws exected. Risk models originlly designed to redict 30-dy mortlity will minly redict crdiovsculr deth, which ws the most common cuse of erly ost-oertive mortlity (91%). At 1 yer, the cuses of deth will be more diverse nd the roortion of crdiovsculr-relted deth will decrese (74%). The strength of the resent study is tht the lgorithms could be comred using reltively lrge tient mteril, where the tient dt were collected on regulr bsis in the dily clinicl work. The dt ws re-oertively entered into the dtbse, generlly by residents, nd not by the surgeon erforming the oertion. During the lst decdes, severl different risk score lgorithms for crdic surgery hve been ublished, but it still remins difficult to risk strtify individul tients. 4,8 One method to imrove risk lgorithm develoment could be to include more tients with higher risk scores s suggested by Wyse nd Tylor. 21 However, we found tht the score, which ws develoed on 5051 tients, erformed lmost s well s the, develoed on tients. Most risk lgorithms re bsed on logistic regression nlysis with riori ssumtions of liner reltionshis. Another method to imrove risk rediction could be to use more comlex risk model, such s the rtificil neurl network, which hs the dvntge of the ccity to model comlex, non-liner reltionshis nd is reltively robust nd tolernt of missing dt. 22 There re only few studies done in this re, which merits further investigtion. Even if erfect risk rediction lgorithm in crdic surgery is never chieved, identifiction of the besterforming risk lgorithms is imortnt. Pre-oertive risk strtifiction my id in the selection between crdic surgery nd other thereutic modlities currently vilble, fcilitte the lnning of hositl resource utiliztion, nd enble ccurte comrison between different institutions or surgeons. Conflict of interest: none declred. Aendix Tble A1 Pre-oertive generl risk fctors in 6222 oen-hert oertions Pre-oertive risk fctor Men (+SD) or n (%) Amhiscore Cbdel Prsonnet Prsonnet (modified) Trembly Tumn UK ntionl score Veterns Affirs Age b (yers) 66.3 (10.6) Femle gender 1765 (28.4) Height b (centimetres) (8.0) Weight b (kilogrms) 78.7 (13.8) Hb b (g/l) (16.3) Serum cretinine b 95.2 (40.5) (mmol/l) Hyertension 2458 (40.0) (sys.140 mmhg) Continued Downloded from htts://cdemic.ou.com/eurhertj/rticle-bstrct/27/7/867/436822

6 872 J. Nilsson et l. Tble A1. Continued Pre-oertive risk fctor Men (+SD) or n (%) Amhiscore Cbdel Prsonnet Prsonnet (modified) Trembly Tumn UK ntionl score Veterns Affirs Dibetes 1106 (17.9) Hyercholesterolemi 2274 (37.0) (treted) Chronic ulmonry 477 (7.7) disese Active smoker 539 (8.8) Cerebrovsculr 448 (7.2) disese Periherl vsculr 636 (10.3) disese Kidney disese by 248 (4.0) history Dilysis 28 (0.5) Adult congenitl hert 11 (0.2) disese ASA mediction 4346 (69.9) Diuretic mediction 2203 (35.4) Immunosuressive 71 (1.2) mediction ASA indictes cetylslicylic cid; Hb, hemoglobin; sys, systolic rteril blood ressure. Additive nd logistic. b Continuous vribles re resented s men (þsd). The nlysis is bsed on oertions where the risk fctor dt were vilble. Tble A2 Pre-oertive crdic risk fctors in 6222 oen-hert oertions Pre-oertive risk fctor Men (+SD) or n (%) Amhiscore Cbdel Prsonnet Prsonnet (modified) Trembly Tumn UK ntionl score Veterns Affirs Previous crdic surgery 457 (7.3) Active endocrditis 55 (0.9) Hert filure 1156 (18.6) Crdiomegly 327 (5.3) Unstble ngin 744 (12.0) CCS b 2.6 (1.0) NYHA b 2.4 (1.0) Recent MI (within 24 h) 144 (2.3) Recent MI (within 48 h) 207 (3.3) Recent MI (within 21 dys) 793 (12.9) Ventriculr rrhythmi (cute) 64 (1.0) Atril fibrilltion 508 (8.3) Pcemker 33 (1.0) Left min stenosis 964 (17.9) Trile vessel disese 2690 (50.7) LVEF b 49.7 (11.6) Aortic grdient.120 mmhg 278 (4.5) Pulmonry hyertension 191 (3.1) CCS, Cndin Crdiovsculr Society; LVEF, left ventriculr ejection frction; NYHA, New York Hert Assocition; MI, myocrdil infrction. Additive nd logistic. b Continuous vribles re resented s men (þsd). The nlysis is bsed on oertions where the risk fctor dt were vilble. Downloded from htts://cdemic.ou.com/eurhertj/rticle-bstrct/27/7/867/436822

7 Comrison of 19 re-oertive risk strtifiction models in oen-hert surgery 873 Tble A3 Criticl re-oertive situtions in 6222 oen-hert oertions Pre-oertive risk fctor n (%) Amhiscore Cbdel Prsonnet Prsonnet (modified) Trembly Tumn UK ntionl score Veterns Affirs Urgent surgery 1376 (22.2) Emergency surgery 628 (10.1) PTCA filure/comliction 138 (2.2) Intubted 71 (1.1) IABP 134 (2.2) Uncontrolled systemic disturbnce b 1135 (18.2) Crdiogenic shock 78 (1.3) Hemodynmiclly unstble 286 (4.6) Criticl stte c 308 (5.0) Ctstrohic sttes d 206 (3.3) IABP, intr-ortic bllon um; PTCA, ercutneous trnsluminl coronry ngiolsty. Additive nd logistic. b Any one or more of the following: systolic ulmonry rteril ressure. 50 mmhg; uncontrolled systemic rteril hyertension; renl insufficiency; chronic lung disese; oor hetic function; cerebrovsculr insufficiency; severe rrhythmis; ctive endocrditis; cchexi. c Any one or more of the following: ventriculr tchycrdi or fibrilltion or borted sudden deth; re-oertive crdic mssge; re-oertive ventiltion before rrivl in the nesthetic room; re-oertive inotroic suort; intrortic blloon counterulstion; or re-oertive cute renl filure (nuri or oliguri, 10 ml/h) d Any one or more of the following: cute structurl defect (cute ventriculr setl defect or cute mitrl vlve regurgittion); crdiogenic shock; cute renl filure. Tble A4 Surgicl informtion in 6222 oen-hert oertions Oertion n (%) Amhiscore Cbdel Prsonnet Prsonnet (modified) Trembly Tumn UK ntionl score Veterns Affirs Venous grft lone 572 (9.2) Single vlve surgery only 657 (10.6) Vlve surgery only 721 (11.6) Aortic vlve surgery b 1106 (17.9) Mitrl vlve surgery c 449 (7.3) Tricusid vlve surgery b 40 (0.6) Vlve surgery nd CABG 619 (9.9) Other d thn isolted CABG 1871 (30.1) Hert trnslnttion 78 (1.3) Post-infrction setl ruture 37 (0.6) Left ventriculr neurysm 16 (0.3) Surgery on thorcic ort 209 (3.4) Aortic dissection (cute) 79 (1.3) Additive nd logistic. b With or without CABG surgery. c With or without CABG surgery, excet for Amhiscore where the definition is mitrl vlve surgery with CABG surgery. d Totl number of vlve or miscellneous rocedures with or without CABG surgery. Downloded from htts://cdemic.ou.com/eurhertj/rticle-bstrct/27/7/867/436822

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