Role of interatrial block in modulating cryptogenic stroke risk in patients with patent foramen ovale: a retrospective study.

Background: The patent foramen ovale (PFO) and interatrial block (IAB) are associated with cryptogenic stroke (CS). However, the role of the interaction between PFO and IAB in CS remains unclear.

Methods: This case-control study enrolled 256 patients with CS and 156 individuals without a history of stroke or transient ischemic attack. IAB was defined as P wave duration > 120 ms. PFO was evaluated by contrast transesophageal echocardiography, and classified as no-PFO, low-risk PFO and high-risk PFO. Multiplicative and additive interaction analysis were used to assess the interaction between PFO and IAB in CS.

Results: Multiplicative interaction analysis unveiled a significant interaction between IAB and low-risk PFO in CS (OR for interaction = 3.653, 95% CI, 1.115-12.506; P = 0.037). Additive interaction analysis indicated that 68.4% (95% CI, 0.333-1.050; P < 0.001) of the increased risk of CS related to low-risk PFO was attributed to the interaction with IAB. The results were robust in multivariate analysis. However, but no significant multiplicative or additive interaction was observed between IAB and high-risk PFO. When stratified by IAB, high-risk PFO was associated with CS in both patients with IAB (OR, 4.186; 95% CI, 1.617-10.839; P = 0.003) and without IAB (OR, 3.476; 95% CI, 1.790-6.750; P < 0.001). However, low-risk PFO was only associated with CS in patients with IAB (OR, 2.684; 95% CI, 1.007-7.149; P = 0.048) but not in those without IAB (OR, 0.753; 95% CI, 0.343-1.651; P = 0.479).

Conclusion: The interaction between IAB and PFO might play an important role in CS, particularly in cases with low-risk PFO.