Australia, Queen Elizabeth I1 Medical Centre, and tBiostatistica1 Consulting Service, Department of Public Health,. University of Western Australia, Nedlands, ...
Ausr. N.Z. 1. Surg. (1998) 68,
16-20
ORIGINAL ARTICLE
PROGNOSTIC FACTORS IN ELECTIVE AORTIC RECONSTRUCTIVE SURGERY A. J. A. HOLLAND,*R. BELL,' E. G. IBACH," R. W. PARSONS,* H. T. V. Vu'
AND
A. K. HOUSE+
*Department of Vascular Surgery, Sir Charles Gairdner Hospital, ?Department of Surgery, University of Western Australia, Queen Elizabeth I1 Medical Centre, and tBiostatistica1 Consulting Service, Department of Public Health, University of Western Australia, Nedlands, Western Australia, Australia Background: The present study was carried out to determine the risk factors associated with peri-operative mortality and longterm survival in patients undergoing abdominal aortic reconstructive surgery (ARS). Methods: A retrospective review was performed of the case notes of all patients having ARS at a university teaching hospital during a 5.5-year period, and their details entered onto a pro forma. Results: A total of 252 patients underwent ARS between July 1989 and December 1994. The peri-operative mortality was 7.5%. The most frequent adverse events were cardiac events, accounting for 8 (42%) of the peri-operative deaths. The risk of a peri-operative cerebrovascular accident was low ( n = 3, 1.2%) as was the risk of peri-operative renal failure requiring dialysis (n = 3, 1.2%). Factors independently linked to increased peri-operative mortality included moderate-to-severe hypertension ( P = 0.05, odds ratio = 3.54), those with renal impairment ( P = 0.05, odds ratio = 2.69), and blood transfusion requirements ( P < 0.001, odds ratio = 1.26). Long-term survival was independently shortened by occlusive disease ( P = 0.004, hazard ratio = 2.78) and ischaemic heart disease ( P < 0.001, hazard ratio = 3.58). Conclusions: The risks of ARS were significantly increased in patients with severe hypertension, those with renal impairment and those requiring blood transfusion. Long-term survival was shortened for those patients with occlusive aortic disease and ischaemic heart disease. These risk factors should be carefully assessed in each patient before performing elective ARS.
Key words: elective aortic reconstructive surgery, long-term survival, mortality, risk factors.
INTRODUCTION
that classified illness severity according to acute physiological variables, chronological age and chronic disease, has been used to assess overall risk based on these parameters."." The aim of the present review was to investigate the impact of a number of these putative risk factors, not only on peri-operative mortality following aortic reconstructive surgery, but also on their relationship to long-term outcome.
The primary aim of vascular reconstructive surgery is to achieve durable graft patency. This should be accomplished with low operative mortality and must provide the patient with significant long-term benefit. Since the first aortic grafting procedure for aneurysmal disease by Dubost i n 1951, the morbidity and mortality associated with elective aortic surgery have steadily improved.'.* Many factors have contributed to these improved results, METHODS including refinement of operative techniques and improvements in anaesthesia and peri-operative care.' With these improveAll patients having elective ARS at Sir Charles Gairdner Hosments has arisen the capability of performing aortic reconstrucpital from July 1989 to December 1994 were identified by using tive surgery (ARS) on higher-risk candidates; enthusiasm for the Hospital Morbidity Data System maintained by the Health operating on these patients needs to be tempered with the Department of Western Australia, and by review of their case knowledge that peri-operative morbidity and mortality are notes. Patients undergoing surgery for aorto-iliac occlusive increased, and the long-term benefit for which the operation disease and aneurysmal disease of the infrarenal aorta and/or was initially intended could be l o ~ t . ~ . ~ iliac arteries were included. Patients with occlusive and aneuOperative risk is a function of not only the nature of the prorysmal disease were classified according to the more dominant cedure but also a number of patient-dependent variables. Deterpathology. Those presenting as emergencies with leaking aneumining individual operative risk involves identifying and rysms and patients requiring renovascular reconstruction were assessing the severity of coexisting disease. This may then allow excluded. pre-operative intervention in order to modify the risk i n v o l ~ e d . ~ . ~ A total of 252 patients underwent aortic reconstructive Correlation between physical status and peri-operative morsurgery during the study period. Nearly three-quarters tality has been well documented.' Acute Physiology And (n = 187, 74%) of the patients were male. The mean age was Chronic Health Evaluation (APACHE), a multi-system index 6 9 years with a range of 38-86 years. The primary indication for operation was aneurysmal disease in 135 patients and occlusive disease in 117 patients. Correspondence: Mr R. Bell, University Department of Surgery, Queen The following risk factors were examined and classified Elizabeth II Medical Centre, Nedlands, WA 6907, Australia. according to the suggested reporting standards of the International Society for Cardiovascular Surgery (Table I ) : ischaemic Accepted for publication 9 J u l y 1997.
17
PROGNOSTIC FACTORS IN AORTIC SURGERY
Table 1. Risk factor categories ~~
Risk factor
0
1
Normal
Mild
2 Moderate
3 Severe
IHD
Asymptomatic, normal ECG
Asymptomatic, remote MI (> 6 months), occult MI on ECG
Stable angina, asymptomatic arrhythmia, controlled failure
Unstable angina, symptomatic or poorly controlled arrhythmia, poorly compensated failure, MI < 6 months
HTN
Diastolic < 90 mmHg
Requires two drugs
> two drugs or
Diabetes
None
Easily controlled, single drug Adult onset, no insulin
Tobacco use
None (or not for > I0 years)
RI
No renal disease, creatinine level: < 130 Fmol/L
uncontrolled Adult onset, insulin controlled
Juvenile onset
None currently, abstinence 1-10 years
Currently < 1 pack per day or abstinence < 1 year
Currently > 1 pack per day
Creatinine level: 130-260 pmol/L
Creatinine level: 260-520 @mol/L
Creatinine level: > 520 pmol/L, dialysis or transplant
IHD, ischaemic heart disease; HTN, hypertension; RI, renal impairment; ECG, electrocardiogram; MI, myocardial infarction.
Table 2. Patient characteristics and incidence of risk factors Variable Gender Male Female Indication Aneurysmal disease Occlusive disease Risk factors IHD Mild Moderate Severe HTN Mild Moderate Severe Diabetes Mild Moderate Severe Tobacco use Mild Moderate Severe RI Mild Moderate Severe Blood transfusion Not required 1-5 units > 5 units
No. patients
%
I87 65
74.2 25.8
135 117
53.6 46.4
45 56 11
17.9 22.2 4.4
106 44 2
42.1 17.5 0.79
13 8 0
5.2 3.2
110 80
4
43.7 31.8 1.6
50 I 3
19.8 0.4 1.2
60 171 21
23.8 67.9 8.3
-
IHD, ischaemic heart disease; HTN, hypertension; RI, renal impairment.
heart disease (IHD), hypertension (HTN), diabetes mellitus (DM), tobacco use and renal impairment (RI).'" A total of 112 (44%) patients had IHD identified pre-operatively and 152
(60.3%) patients were hypertensive. Diabetes mellitus was relatively uncommon, affecting only 21 (8.3%) patients. A total of 194 (77%) patients were active smokers or had ceased smoking within 10 years prior to surgery. Fifty (19.8%) patients had some degree of renal impairment as defined by having a serum creatinine level greater than 130 pmol/L. Three patients were on regular haemodialysis (Table 2). Patients were assessed for coronary disease on the basis of history and electrocardiogram (ECG). Those who were unable to exercise on account of advanced occlusive disease underwent a dipyridamole thallium scan. Areas of reversible ischaemia were further followed with a cardiological opinion and coronary angiography if revascularization was considered to be necessary. Using these criteria we identified 112 (44.5%) patients with coronary artery disease pre-operatively. No patient underwent elective aortic reconstruction within 3 months of myocardial infarction, and those patients with angina who did not require coronary artery intervention were optimized medically prior to surgery. All operations were undertaken via a midline transperitoneal approach under general anaesthesia. Aortic reconstruction was performed using woven Dacron grafts: either a tube or bifurcate graft depending on the pathology. Haemodynamic monitoring occurred continuously and fluids and blood were administered as required. The transfusion requirement for blood products was defined as the number of units of packed cells or whole blood transfused within 24 h of surgery. Twenty-one (8.3%) patients required a peri-operative transfusion in excess of five units. All patients were managed in the intensive care unit (ICU) for the first 24 h postoperatively and were then returned to the ward if they were stable. In-hospital stay was for a period of 7- 10 days unless complications supervened. Peri-operative morbidity and mortality were defined as those events occurring within 30 days of surgery. Particular note was taken of postoperative acute myocardial infarction (AMI), cerebrovascular accident (CVA), peak creatinine levels and requirement for dialysis. Survival data were obtained by checking the Registrar General's register of deaths for Western Australia."
18
HOLLAND ET AL.
Statistical analysis Univariate analysis of peri-operative mortality was performed for each risk factor using logistic regression. Age was considered as a continuous variable. After each risk factor had been examined independently, adjustment for age and sex was performed. In the case of DM and RI, the relatively small number of patients in the moderate-to-severe categories required analysis on combined data from these two subgroups. Multivariate analysis was used to examine long-term results. Factors that were independently related to long-term survival were identified using the Cox proportional hazard model. Age, sex, indication and R1 were the variables that were initially forced into the model, which was then extended by including IHD, HTN, DM, tobacco use, procedure and blood transfusion. Forward stepwise selection was performed to choose the best model. In order to adjust for age, the best model was then extended by including the interaction term between age and time. As this was not significant ( P = 0.425) the Cox proportional hazard model was accepted, and age was considered as a continuous variable. For those variables found to have a significant long-term effect, survival curves were constructed using the Kaplan-Meier technique (Figs 1,2).
h c
d
2Q -
.___........__...
0.6-
0.5-
.-9 0.4> L
0.3-
v)
0.2.
1
O 0 0.0
3
2 .
4
5l
Year
Fig. 1. Kaplan-Meier survival curve for patients (-) without ischaemic heart disease.
0.9-
*.
.,.- -L.
a'.
- -
.. -.-. ..
....._._ I_._
0.7-
A total of 19 patients died within 30 days of surgery, resulting
0.6-
(---) with
and
LI
-__. ____. --,__
0.8 -
Peri-operative morbidity and mortality i n a peri-operative mortality of 7.5% for this series. The causes of death are shown in Table 3. The most common complications were cardiac. Fourteen patients (5.6%) survived a peri-operative AMI, of which four were silent and were diagnosed on the basis of ECG changes in association with elevated cardiac enzymes. Twenty-seven patients experienced angina, cardiac failure or a dysrhythmia which required medical intervention. Eight patients died as a result of a cardiac event. Nineteen patients developed a chest infection requiring antibiotic therapy, but there were no deaths as a result of this complication. Only three patients (1.2%) had a clinically obvious peri-operative CVA, of whom one died. Nine patients who had not previously required renal support experienced deteriorating renal function postoperatively. Five of these patients had required suprarenal aortic clamping for a mean period of 27 min but none required dialysis postoperatively. The remaining four patients became dialysis-dependent prior to their demise; three from multi-organ failure and one from renal failure. Univariate analysis (Table 4) revealed a strong association between blood transfusion and an increased risk of peri-operative death ( P < 0.001). For example, a patient requiring six or more units of blood transfused peri-operatively had a fourfold increased risk of mortality within the first 30 days of surgery. Two putative risk factors were linked to an increased risk of peri-operative mortality; moderate-to-severe hypertension ( P = 0.05, odds ratio = 3.54) and RI ( P = 0.05, odds ratio = 2.69). Multivariate analysis did not reveal any additional risk factors, in particular IHD and smoking, which might have been masked by the strength of the association with blood transfusion. The peri-operative mortality was no different for those undergoing ARS for aneurysmal as opposed to occlusive disease.
...~..... ....-. . L .-. ..._,
5 units
< 0.001 < 0.001
*For each unit of blood transfused. IHD, ischaemic heart disease; HTN, hypertension.
Table 4. Multivariate analysis of risk factors and long-term survival Risk factor
Age (increasing) Sex (female) IHD Indication (occlusive) Renal impairment
No. patients 235 63 104 114 44
P
0.16 0.09 < 0.001 0.004 0.24
Hazard ratio
9.5% confidence intervals
1.03 0.46 3.58 2.78 I .60
0.99-1.08 0.19-1.14 1.69-7.59 1.38-5.59 0.73-3.52
IHD, ischaemic heart disease.
DISCUSSION With the advances in vascular surgery and anaesthesia during the past three decades, the results following elective aortic surgery have steadily improved. Mortality rates of < 2% have been reported following elective aortic aneurysm repair, although reporting bias may mean that the true figure is rather higher.2,1Z-14 Certainly, most series of ARS report peri-operative mortality rates in the region of 5% or less, and by these standards the early outcomes reported in the present study are di~appointing.~.~~ Peri-operative mortality was significantly associated with three prognostic indicators: transfusion requirement, moderateto-severe hypertension, and pre-operative renal failure. The relationship to transfusion requirement has been well documented and usually reflects technical difficulties encountered at the time of surgery.16 Whether patients have a history of symptomatic ischaemic heart disease or not, a transfusion requirement in the peri-operative phase in excess of six units is indicative of a poor outcome. Technical considerations such as the size of the aneurysm, the length of the neck below the renal arteries, extension into the iliac vessels and the extent of calcification of the juxtarenal aorta and iliac vessels should therefore be carefully considered before embarking upon ARS. Our
finding of an association between moderate-to-severe hypertension and increased risk of peri-operative death has not been previously clearly identified. Our results would suggest that patients with HTN should have treatable causes excluded and their control optimized prior to elective surgery. The increased risks of ARS in patients with renal impairment mean that this factor must be carefully considered prior to any elective surgery.3.4.17.18 Because atherosclerosis is known to be a generalized condition, it is not surprising that most studies of outcomes following vascular surgery focus on cardiac-related morbidity and mortality.2-6,'2~1y In one study the incidence of coronary artery disease in patients with aorto-occlusive disease was 54%, and in 13% of cases the disease was severe enough to warrant correction prior to vascular reconstruction.z0 Another review of patients with aneurysmal disease found that 56% had coronary artery disease and that in as many as 22% this was unsuspected?[ The incidence of coronary artery disease reported in the present study is slightly less than those reviews, which may well indicate that even in the so-called 'asymptomatic' group there may have been a number of patients with significant coronary artery disease. This might explain why a history of ischaemic heart disease was not an independent risk factor for peri-operative death in the present study. Alternatively, we may have been able to identify in advance those patients most likely to experience cardiac complications, and in so doing, the perioperative medical management of these patients was optimized. This would seem to be the more plausible explanation, given that the long-term outcome of these patients was certainly worse. This finding is not in keeping with all studies, and several authors have identified myocardial disease, defined as a history of previous infarction and 'ongoing' angina, as significant factors for peri-operative mortality.?' Other risk factors for vascular disease were not found, in the present study, to influence immediate outcome. The failure of tobacco use to influence peri-operative mortality has previously been reported.22 A review of the influence of diabetes on
20
HOLLAND ET AL.
outcome following vascular surgery also supports our findings. Although diabetics, whether insulin-dependent or not, did not have an increased risk of death, they have been shown to have a higher incidence of peri-operative morbidity.23 The finding in the present study that long-term outcome was worse in patients with aorto-iliac occlusive disease as compared to those with aneurysmal disease, independent of other associated risk factors, was surprising. The two groups did not seem to differ in all other respects. It demonstrates nevertheless the durability of aortic surgery for aneurysmal disease and that the good early outcomes reported for this condition are maintained in the long term. The negative influence of ischaemic heart disease on long-term outcome has been demonstrated consistently in other ~ t u d i e s . ~ ~ ~ ~ ~ ~ ~ The present review reaffirms the impact of technical difficulties on peri-operative mortality and stresses the importance of considering these aspects in decision-making for elective aortic surgery. It would seem that a history of IHD is not a prognostic indicator of peri-operative mortality, providing that the patient’s cardiac status can be satisfactorily managed in the peri-operative period, although the risks are increased in patients with established RI and moderate-to-severe hypertension. Long-term survival is adversely and independently linked to occlusive disease and IHD.
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8. Knaus WA, Zimmerman JE, Wagner DP, Draper EA, Lawrence DE. APACHE: acute physiology and chronic health evaluation: A physiologically based classification system. Crit. Care Med. 1981; 9: 591-7. 9. Knaus WA, Draper EA, Wagner DP, Zimmerman JE. APACHE 11: A severity of disease classification system. Crit. Care Med. 1985; 13: 818-29. 10. Baker JD, Rutherford RB, Bernstein EF, Kempczinski RF, Zarins CK. Suggested standards for reports dealing with cerebrovascular disease. J. Vasc. Surg. 1988; 8: 721-9. 11. Holrnan CDJ, Brooks BH. Morbidity Statistics in Western Australia: An Overview of the Data Collections and their Applications. Perth: Health Department of Western Australia, 1987. 12. Taylor P. The management of aortic aneurysms. Br. J. Clin. Pract. 1992; 46: 6-8. 13. Buck N, Devlin HB, Lunn JN. Report of a Confidential Enquiry into Perioperarive Deaths (CEPOD). London: Nuffield Provincial Hospitals Trust, 1987. 14. Pilcher DB, Davis JH, Ashikage T et al. Treatment of abdominal aortic aneurysm in an entire state over 7 and a half years. Am. J. Surg. 1992; 4: 135-40. 15. Darling RC, Brewster DC. Elective treatment of abdominal aortic aneurysm. World J. Surg. 1980; 4: 661-7. 16. Goldstone J. Aneurysms of the aorta and iliac arteries. In: Moore WS (ed.). Vascular Surgery-A Comprehensive Review, 4th edn. Philadelphia: WB Saunders, 1993; Ch. 23. 17. Cohen JR, Mannick JA, Couch NP, Whittemore AD. Abdominal aortic aneurysm repair in patients with preoperative renal failure. J. Vasc. Surg. 1986; 3: 867-70. 18. Brenowitz JB, Williams CD, Edwards WS. Major surgery in patients with chronic renal failure. Am. J. Surg. 1977; 134: 765-9. 19. Roger VL, Ballard DJ, Hallett JW, Osmundson PJ, Puetz PA, Gersh BJ. Influence of coronary artery disease on morbidity and mortality after abdominal aortic aneurysmectomy: A population based study, 1971-1987. J. Am. Coll. Cardiol. 1989: 14: 1245-52. 20. Hertzer NR, Yeung JR, Kramer J et al. Routine coronary angiography prior to elective aortic reconstruction. Arch. Surg. 1979; 114: 1336-40. 21. Brown DW, Hollier LH, Pairolero PC et al. Abdominal aortic aneurysm and coronary artery disease. Arch. Surg. I98 I ; 116: 1484-8. 22. Samy AK, Murray G , MacBain G. Glasgow aneurysm score. Cardiovasc. Surg. 1994; 2: 41-4. 23. Treiman GS, Treiman RL, Foran RF et al. The influence of diabetes mellitus on the risk of abdominal aortic surgery. Am. Surg. 1994; 60: 436-40. 24. Feinglass J, Pearce WH, Martin GJ. Prognosis after graft replacement operation for abdominal aortic aneurysm. West. J . Med. 1993; 159: 474-80. 25. Johnston KW. Nonruptured abdominal aortic aneurysm: Six year follow-up results from the multicentre prospective Canadian aneurysm study. J. Vasc. Surg. 1994; 20: 163-70.
