Interatrial septal mobility predicts larger shunts across patent foramen ovales: an analysis with transmitral Doppler scanning.

BACKGROUND

The association of patent foramen ovale (PFO) with cryptogenic stroke is strongest in patients with larger shunts and patients with atrial septal aneurysms (ASAs). We postulated that the potency of ASA as a risk factor for stroke relates to the size of shunt across PFOs associated with mobile atrial septae. The purpose of this study was to investigate the relationship between atrial septal mobility and the degree of right-to-left shunting with a transthoracic transmitral Doppler scanning (TMD) contrast technique.

METHODS

In 165 consecutive patients, transthoracic TMD recordings were made during a saline contrast study with the patient at rest and after a maneuver to increase right atrial pressure. Bubble transit corresponded to high intensity signals in the velocity envelope of the mitral inflow profile and was quantified by a bubble score.

RESULTS

A PFO was diagnosed in 59 patients (36%). In 50 patients with PFO and adequate echocardiography images, the incidence of ASA was 52%. In this group, both total septal mobility and leftward deviation predicted the TMD bubble score at rest (Spearman rho 0.64, 0.64, respectively, P <.001) and after the maneuver (Spearman rho 0.74, 0.73, P <.001). In 28 patients with cerebral ischemic events, the maneuver bubble score was predictive for cryptogenic stroke (P =.02, odds ratio 7.58). There was a trend toward significance between total septal motion and cryptogenic stroke (P =.06).

CONCLUSION

Atrial septal mobility predicts the degree of right-to-left shunts across PFOs. The role of excessive septal mobility in the etiology of stroke may therefore be caused by the greater opportunity for paradoxical embolism because of the size of the associated trans-PFO shunt.