CASE 11832 Published on 30.05.2014

MRI of permanent righ-to-left shunt in patent foramen ovale



Case Type

Clinical Cases


Lucio Olivetti1, Mohammed Abualkheir1, Sara Ceccomancini2

1Department of Radiology
2Department of Cardiology
Istituti Ospitalieri di Cremona
Viale Concordia 1
26100 Cremona Italy

51 years, female

Area of Interest Cardiac, Neuroradiology brain ; Imaging Technique Echocardiography, MR
Clinical History
A 51-year-old woman presented at Emergency Department with stroke. The medical history excluded hypertension, diabetes mellitus, heart disease and smoking; the patient did not use oral contraceptives. An accurate but negative clinical history was taken focusing on symptoms related to a paroxysmal cardiac arrhythmia and carotid atherosclerotic disease.
Imaging Findings
Brain MRI, performed three day after a negative CT, revealed an ischaemic lesion of the right globus pallidus (Fig. 1). In the following, otherwise normal, diagnostic workup searching for a cardiac origin of cerebral embolism, a transthoracic echocardiography associated with i.v. injection of 10 ml of agitated saline solution (contrast echocardiography, CE) was suggestive for patent foramen ovale (PFO) with right-to left shunt but was inconclusive in description of anatomic type and definite site of PFO (Fig. 2). A complex anatomic abnormality of the fossa ovalis was documented at transoesophageal echocardiography (TEE) (Fig. 2); CE during TEE was not useful to demonstrate the anatomic passage of CE with certainty. Patent foramen ovale (PFO) with permanent right-to-left shunt was otherwise clearly evident during cine-heart MRI, performed to exclude possible causes of right to left shunt, such as anomalous venous returns (Fig. 3).
Approximately 196, 000 people experience stroke each year in Italy; 39, 000 are recurrent attacks. About 25% to 40% of strokes are caused by unknown, undetermined or unclear causes and are commonly termed cryptogenic strokes (CS) [1]. The correlation between PFO and CS was first suggested in 1988: the prevalence of PFO detected by CE was significantly higher in patients with stroke (40%) than in the control group (10%) [2]. Thrombo-emboli, originating either in the right atrium or venous vasculature, may pass through PFO into the systemic circulation and then to the brain. Actions, such as Valsalva manoeuvre during urination or defecation, can transiently reverse the normal left-to-right pressure gradient existing in the atrial cavities [3]. Patients with permanent right-to-left shunt represent a subgroup at potentially higher risk of paradoxical embolism. Permanent shunt usually corresponds to large shunt induced by Valsalva manoeuvre but the correlation is not always linear [4, 5]. Transthoracic echocardiography has a limited value to characterize complex defects associated with PFO, and to detect pulmonary venous abnormalities, often associated to atrial septal defect. TEE is the imaging diagnostic test of choice to detect and characterize PFO [6]. However, during TEE patients may have problems in performing a correct Valsalva manoeuvre and stress-induced elevation of systemic pressures may abolish the transient inversion of left-to-right atrial pressure gradient. MRI has a significant role to play because it delineates not only the fossa ovalis anatomy but also the atrial shunt without the limitations of CE. Multi-slice two dimensional balanced steady-state free precession (b-SSFP) sequences are useful in imaging congenital heart diseases: they allow high spatio-temporal resolution and have a good myocardial/blood pool contrast with relatively fast acquisition times; high velocity flow will lead to signal loss, allowing qualitative analysis of blood flow jets. However, b-SSFP sequences require multiple breath-holds that may be not tolerated in some patients, particularly children. In this case we do not use phase-contrast (PC)-MRI but this flow technique can accurately size the cross-sectional dimensions of the defect. According to present guidelines, CMRI is indicated to detect anomalous venous returns [7]. The recognition of an anomalous venous returns in combination with a PFO after a cryptogenic ischaemic event may favour surgical treatment [8]. MR findings are more powerful predictors of successful transcatheter closure of fossa ovalis defects than transthoracic or TEE [9].
Differential Diagnosis List
Patent cardiac foramen ovale with permanent shunt right-left shunt.
Atrial septal defects
Intra-pulmonary shunt
Final Diagnosis
Patent cardiac foramen ovale with permanent shunt right-left shunt.
Case information
DOI: 10.1594/EURORAD/CASE.11832
ISSN: 1563-4086