Asian Cardiovasc Thorac Ann 1999;7:200-203
© 1999 Asia Publishing EXchange Pte Ltd
Is Surgery Justifiable for Treatment of Small Abdominal Aortic Aneurysms?
Murat Bayazit, MD,
M Kamil Göl, MD,
H Zafer I
can, MD,
Tulga Ulus, MD,
O
uz Tademir, MD,
Kemal Bayazit, MD
Department of Cardiovascular Surgery
Türkiye Yüksek  htisas Hospital
Ankara, Turkey
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For reprint information contact: M Kamil Göl, MD Tel: 90 312 310 3080/1232 Fax: 90 312 312 4120 email: nkgol{at}ato.org.tr Department of Cardiovascular Surgery, Türkiye Yüksek htisas Hospital, 06100 Sihhiye, Ankara, Turkey.
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Abstract
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Patients who underwent elective surgery for abdominal aortic aneurysms between January 1990 and December 1996 were evaluated retrospectively. Forty-six patients (group 1) with aneurysms of less than 5 cm in diameter were compared with 121 patients (group 2) with larger aneurysms. There were no differences in age, sex, or associated pathology between the two groups. Hypertension, coronary artery disease, and chronic obstructive lung disease were the most frequently associated conditions. Hospital mortality was not significantly different; 4.3% for group 1 and 2.5% for group 2. At 7 years, the cumulative long-term survival rates for group 1 and group 2 were 97% and 90% respectively (p > 0.05). For any infrarenal aortic aneurysm, indication for surgery should be based on the rate of aneurysm expansion, development of increased aneurysm-related symptoms or complications, and patient anxiety.
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Introduction
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Since the first report by Dubost and colleagues1 in 1951, there have been many advances in the diagnosis and treatment of abdominal aortic aneurysms (AAAs), especially in the last two decades. These advances have led to controversy over the treatment of small AAAs. Many factors influence the decision to perform elective repair of AAAs but undoubtedly the risk of rupture and the expected mortality and morbidity are the most important. Since small AAAs have a lower rupture risk (0% to 12%), some investigators recommend watchful waiting and close observation with ultrasonography every 6 months.2–7 Others advocate early elective surgery in the expectation of lower early and late mortality and morbidity.3,8 A recent report concluded that in view of the safety of elective aneurysm surgery compared with the risk of rupture, patients with small AAAs who are good surgical risks should be considered for elective repair.9 In order to clarify this issue, we evaluated our experience retrospectively.
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Patients and Methods
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Between January 1990 and December 1996, 188 patients with infrarenal AAAs underwent surgery in our clinic. Twenty-one were treated on an emergency basis due to rupture and they were excluded from this study that comprised 167 cases of elective repair. The patients were divided into two groups: group 1 consisted of 46 patients with infrarenal AAAs between 4 and 4.9 cm in diameter; group 2 consisted of 121 patients with infrarenal AAAs with a diameter of 5 cm or greater. Patient characteristics and concomitant risk factors are listed in Table 1
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Physical examination and palpation of the pulsatile abdominal mass usually suggested the diagnosis. Diagnosis was confirmed by ultrasonography, computed axial tomography, or aortography. The aneurysmal diameters measured by the diagnostic techniques agreed with intraoperative measurements. All patients were screened for coronary artery disease by coronary angiography and ventriculography prior to surgery. In patients with severe coronary artery disease in whom coronary bypass surgery was indicated, it was performed 2.3 ± 1.1 months before AAA repair.
During aneurysm repair, radial or brachial artery blood pressure, cardiac rhythm, pulmonary artery pressure (using a Swan-Ganz catheter), central venous pressure, and urine output was monitored in all patients and continued for 48 hours postoperatively. A subumbilical transverse laparo-tomy incision was used. In 12 cases, the operation was performed retroperitoneally. In group 1, bifurcated Dacron grafts (recently, sealed Dacron grafts) were used in 16 patients (35%) and 30 patients received tube grafts (65%). In group 2, bifurcated grafts were used in 71 cases (59%) and tube grafts were used in 50 (41%).
Statistical analyses and comparisons between the two groups were made with the two-sample t test for age, chi-squared analysis was used for comparisons of sex, operative mortality, and prevalence of associated diseases. The Kaplan-Meier method was used to analyze survival. A log-rank test was used to compare survival rates between the two groups. A p value of less than 0.05 was considered statistically significant.
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Results
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There was a statistically significant difference in the use of tube or bifurcated grafts between the two groups (p < 0.001). There was no significant difference between the mean ages of the two groups and patient age was not a risk factor for early or late mortality in either group. Inoperable coronary artery disease was more frequent in group 2 compared to group 1, although not statistically significant.
Death within the first 30 days after the operation was accepted as early mortality. Early mortality was 4.3% (2/46) and 2.5% (3/121) for groups 1 and 2, respectively. One of the deaths in group 1 was due to malignant arrhythmia and intractable ventricular fibrillation, the other involved a 71-year-old patient with a peptic ulcer (operated) and chronic obstructive lung disease. His operation was performed retroperitoneally and the inferior mesenteric artery was tied; after one week, he was investigated again for colon necrosis and the Hartman procedure was performed. His death was due to multiorgan failure and sepsis. Two of the 3 deaths in group 2 were of patients classified as inoperable for coronary artery bypass grafting. One of these deaths was due to excessive postoperative bleeding; the other 2 involved cardiac events (myocardial infarction and intractable ventricular fibrillation). There was no statistically significant difference between the two groups for early mortality (p > 0.05). Early postoperative complications are shown in Table 2.
Late follow-up data was obtained in all of those who survived hospitalization. In group 1, the mean follow-up period was 2.71 ± 1.43 years (2 to 79 months). In group 2, the mean follow-up period was 3.17 ± 2.26 years (3 to 87 months). One patient in group 1 who was known to have coronary artery disease and chronic renal failure, died 25 months after surgery. Five patients died in group 2 (at 13, 21, 22, 34, and 63 months after surgery). These deaths were due to cerebrovascular events in 2 patients, lung malignancy in one, and cardiac events in 3. The late mortality rates for groups 1 and 2 were 2.3% and 4.2%, respectively. No significant difference between the two groups was found for late mortality (p > 0.05). When the survival rates of the two groups were compared, no significant difference was found; after 7 years of follow-up, the cumulative survival rates were 97.1% for group 1 and 90% for group 2. Cumulative long-term survival rates for both groups, excluding hospital mortality, is shown in Figure 1. A significant difference was found by log-rank test in the survival rates for patients with chronic obstructive lung disease (p < 0.0017).
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Figure 1. Actuarial survival rates in patients with small (group 1) and large (group 2) abdominal aortic aneurysms.
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Discussion
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The high mortality rate associated with ruptured aortic aneurysms (range, 15% to 94%) contrasts with the low mortality rate of elective resection (range, 1.4% to 7.5%) and this has encouraged elective aneurysm repair in all patients at risk of rupture, even if the risk is low.9–13 An important influence in the acceptance of 4 cm as a safety limit was the autopsy study of Darling and colleagues3 which found a similar incidence of rupture in aneurysms of 4.1 to 5 cm in diameter as in larger aneurysms (5.1 to 7 cm).
The rate of growth of an aneurysm is variable, even within the same individual. Some aneurysms remain quiescent for months or years and then show a sudden increase in the rate of growth.14–16 The growth rate cannot be accurately predicted for the aneurysm in any given individual. In a recent study, the growth of 514 aortic aneurysms was followed at 6 to 12-month intervals by ultrasonography.17 With an initial size varying from 2.5 to 6 cm, the expansion rates of the aorta were 0.5 cm per year or less in 78%, between 0.5 and 1 cm per year in 10%, and 1 cm per year or more in 12%. The incidence of rapid expansion increased significantly in older patients with aneurysms larger than 3 cm and in younger patients with aneurysms larger than 4 cm.
Early repair of small AAAs has been based on the assumption of a lower operative mortality rate, inevitable aneurysm expansion and worsening operative risk with age, improved late survival if repair is performed earlier in life, and the desire to end the patient's anxiety.6 The results of our study do not support a lower operative mortality for small AAAs than for larger aneurysms. Both groups of patients were in the same age range and the mean ages did not differ. Survival rates in the long-term were also similar. As the ages were similar, long-term survival would not be expected to differ in the two groups since the size of the aneurysm is irrelevant to mortality.
A series of studies was published during the preparation of this report. One noted that ultrasonic surveillance of small AAAs was safe and early surgery did not provide a long-term survival advantage.18 These results from the UK Small Aneurysm Trial do not support a policy of open surgical repair of aneurysms between 4 and 5.5 cm in diameter. Also, the mean cost of treatment in the early surgery group was significantly higher than ultrasonic surveillence.19 The difference in cost of the two approaches is likely to be greater in Turkey and most Asian countries where medical staff costs are lower. One of the most important conclusions of the UK Small Aneurysm Trial was that there was an improvement in some features of health-related quality of life in the early surgery group. However, this is a subjective result on which a justification of early open surgery cannot be based.19
It is not our intention to discuss the indications for resection of AAAs. Every surgeon should be aware of the surgical risks and long-term survival for any given abdominal aortic aneurysm. Social and environmental factors in our country make it very hard to follow-up patients regularly and may justify surgical intervention in cases of small aneurysms, since life has no comparable cost. Develop-ment of increased aneurysm-related symptoms or complications such as coexistence of significant aortoiliac disease, embolization, fistulization, or thrombosis, are also solid indications for surgical management of small AAAs. However, it should be stressed that surgical repair of a small aneurysm does not lower the risks for the patient.
In this study, both groups were similar with respect to patient characteristics, early and late mortality rates, and the prevalence of associated diseases. The numbers in our study were not large enough to derive firm conclusions but they seem to parallel the UK Small Aneurysm Trial findings. Perhaps a mulitcenter randomized trial should be carried out in countries like ours where inputs of survival and cost are quite different from those of the UK. With the encouraging efforts of the medical industry, maybe in future we will all come to the conclusion that "endovascular repair of small abdominal aortic aneurysms is safer and cheaper than any other measure."
We concluded that operations for all AAAs carry the same operative risks and survival rates, regardless of size. Resection upon diagnosis in good risk patients appears to be the safest overall course of management but the surgeon's decision to operate depends on precise knowledge of the balance between the risks and benefits of surgery.
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References
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Abstract
Introduction
