The natural history of guidelines: The case of aortopathy related to bicuspid aortic valves

- Clinical guidelines seek to synthesize the best evidence to guide decisions.
- Bicuspid valve aortopathy was mentioned in 10 guidelines between 1998 and 2014.
- Surgical thresholds changed from 5.5 cm diameter to 4-4.5, and then back to 5.5 cm.
- No conclusive proof supports either an aggressive or conservative strategy.
- Guidelines may be affected by subjectivity when evidence is not definitive.

Clinical guidelines represent statements that seek to synthesize the best evidence to guide a course of action to improve health outcomes and more cost-effective use of resources. However, even when the evidence is not definitive, comprehensive documents are still needed to guide clinical decision-making. In these circumstances, guidelines are inevitably affected by perceptions of the problem and their possible solutions. From 1998 to 2014, 10 different international guidelines have focused on the aortopathy related to bicuspid aortic valves. Recommended thresholds for intervention started at a cutoff level of 5.5 cm in 1998, reached a nadir of 4 to 4.5 cm in 2010, and returned to a 5.5 cm cutoff level in 2014. During this time, no conclusive objective proof was published to support either an aggressive or conservative strategy. The consequence was that an undefined number of patients underwent surgery (and potential complications thereof) at an earlier disease stage than might have been necessary. This experience might provide a clue as to how guidelines evolve, and provide insight as to how to avoid a similar process in the future.