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Management of small abdominal aortic aneurysms. Early surgery vs watchful waiting
D A Katz1, B Littenberg, J L Cronenwett
1Department of Medicine, Veterans Administration Medical Center, White River Junction, VT 05001.
Insights
For small abdominal aortic aneurysms (AAAs) under 5 cm, early surgery generally offers better long-term survival than watchful waiting. However, watchful waiting may be preferred for very small AAAs (<4 cm) or when rupture risk is low.
Area of Science:
- Vascular Surgery
- Decision Analysis
- Health Economics
Background:
- Small abdominal aortic aneurysms (AAAs) less than 5 cm require careful management strategies.
- Two primary approaches include early surgical repair and watchful waiting with periodic monitoring.
Purpose of the Study:
- To compare the long-term survival outcomes of early surgery versus watchful waiting for small AAAs.
- To inform clinical decision-making for managing abdominal aortic aneurysms based on size and risk.
Main Methods:
- A Markov decision tree model was developed to simulate patient outcomes.
- Data on AAA rupture/expansion rates were derived from a longitudinal study and literature review.
- Quality-adjusted life years (QALYs) were used to assess long-term survival.
Main Results:
- Early surgery improved survival for patients presenting with a 4-cm AAA, considering a 3.3% annual rupture rate and 4.6% operative mortality.
- The benefit of early surgery diminished with increasing patient age.
- Watchful waiting became favored if the AAA rupture rate was low (0.4 per 100 patient-years) or operative risk increased.
Conclusions:
- Early surgical intervention is generally the preferred strategy for abdominal aortic aneurysms (AAAs) less than 5 cm.
- Watchful waiting is a viable option for patients with very small AAAs (<4 cm) or those at low risk of rupture.
- Improved data on rupture risk for small AAAs (<5 cm) is crucial for refining clinical management decisions.
Objective:
To compare two clinical strategies for the management of small abdominal aortic aneurysms (AAAs) less than 5 cm in diameter: early surgery (repair small AAAs when diagnosed) and watchful waiting (measure AAA size every 6 months and repair when the diameter reaches 5 cm).
Data Sources:
We reviewed data from an earlier longitudinal study of patients with small AAAs to estimate incidence rates of rupture or acute expansion. Estimates for other parameters in the model were obtained by searching the medical literature (MEDLINE, 1966 to present).
Data Synthesis:
We constructed a Markov decision tree to compare early surgery with watchful waiting in patients with asymptomatic AAAs less than 5 cm in diameter, with respect to long-term survival in quality-adjusted life years. The average annual rates of rupture or acute expansion for AAAs with a maximal transverse diameter of less than 4.0, 4.0 to 4.9, and at least 5.0 cm, are 0, 3.3, and 14.4 events per 100 patient-years of observation, respectively. At an average rupture rate of 3.3 events per 100 patient-years and an average operative risk for elective surgery (4.6%, 30-day mortality), our model predicts that early surgery improves survival in patients who present with a 4-cm AAA. The benefit of early surgery decreases with increased age at presentation. If the average rupture rate for AAAs less than 5 cm is assumed to be low (eg, 0.4 event per 100 patient-years), watchful waiting if favored, particularly as operative risk increases. The decision in this subgroup, however, is sensitive to possible future increases in operative risk.
Conclusions:
In the majority of scenarios that we examined, early surgery is preferred to watchful waiting for patients with AAAs less than 5 cm in diameter. Watchful waiting is generally favored, however, for patients with a low risk of AAA rupture or acute expansion, including those patients who present with very small AAAs (eg, < 4 cm). More accurate data concerning the rupture risk of AAAs less than 5 cm would improve clinical decision making.
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