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Monday, 16 October 2006 - 3:15 PM


William Dale, MD, PhD, University of Chicago, Chicago, IL, Joshua Hemmerich, PhD, University of Chicago, Chicago, IL, Elizabeth Ghini, MA, University of Chicago, Chicago, IL, and Margaret L. Schwarze, MD, University of Wisconsin, Madison, WI.

Purpose: With higher detection and therefore increased prevalence of asymptomatic abdominal aortic aneurysms (AAA), an increasing number of vascular surgeons are making decisions about the timing of surgery. Overall peri-operative mortality is approximately 5% for elective open repair. The growth-related risk of rupture crosses this operative mortality risk when AAA reach 5.5cm. Until this size is reached, guidelines recommend that expansion be monitored by imaging every 3-6 months. Such “watchful waiting” may be anxiety-provoking. The “availability bias” may make recent, emotionally-vivid, anxiety-provoking events -- such as AAA rupture -- influence statistically-optimal choices. We investigated the role of induced anxiety in the decision to “operate” on an expanding AAA analogue among vascular surgeons.

Methods: In a randomized field experiment, vascular surgeons (n = 81) participated in a computer-based, decision-making task in which they chose when to stop inflating an expanding AAA-analogue. While performing the task, participants received updated information concerning size and bursting probabilities. These matched literature-based AAA sizes and burst probabilities, including a constant “opt-out” (i.e. operative) risk of 5%. Participants were randomly assigned to a pre-task demonstration in which the analogue either burst (anxiety induction condition) or did not (control condition). The number of expansions before “opting out” (choosing surgery) or a burst occurred (AAA rupture) were recorded. Additional information collected included pre-manipulation anxiety levels, risk-aversion, uncertainty intolerance, demographics, surgical experience, and game strategy. To account for censoring resulting from bursts, Kaplan-Meier curves and Cox-survival regression on “opting out” were conducted.

Results: On Kaplan-Meier curves, anxiety induction led to an average of 3 fewer expansions versus controls (12 vs. 15) at the median “survival” time. Cox-regression survival analyses demonstrate the anxiety induction increased the likelihood for “opting out” among surgeons at each decision point (HR = 3.32; p < 0.05), even after controlling for age, pre-manipulation anxiety levels, risk attitudes, uncertainty intolerance, and surgical experience. The only other significant predictor of opting out was attention to statistical risk (HR = 3.82; p < 0.05).

Conclusions: Induced anxiety accelerated surgeons' choice for “surgery” for an expanding AAA. Clinically, this corresponds to 9-18 fewer months of “watchful waiting”. There may be an underappreciated role played by emotions like anxiety in medical decision-making among experts, even when evidence-based, statistical guidelines are known.

See more of Concurrent Abstracts A: Decision Support and Preferences
See more of The 28th Annual Meeting of the Society for Medical Decision Making (October 15-18, 2006)