Transesophageal Contrast Echocardiography is Not Always the Gold Standard Method in the Identification of a Patent Foramen Ovale: A Clinical Case.

In the embryo, Eustachian valve is a crescent-shaped membrane extending from the lower margin of the inferior vena cava and the ostium of the coronary sinus into the right atrium toward fossa ovalis and tricuspid valve. At birth, after the functional closure of the foramen ovale, the Eustachian valve loses its function, reducing to an embryo remnant. According to growing evidence, a persistent Eustachian valve is a frequent finding in patients with a patent foramen ovale (PFO). By directing the blood from the inferior cava to the interatrial septum, it may prevent the spontaneous closure of PFO after birth and indirectly predispose to paradoxical embolism. Transesophageal contrast enhanced echocardiography (cTEE) is considered the gold standard to diagnose a PFO in postnatal life, but its accuracy maybe is not so high in the presence of a persistent Eustachian valve. In these cases, color Doppler TEE is more sensitive and simplifies the diagnostic process, reducing the duration of TEE and improving the patient compliance.

CASE HISTORY

A 23-year-old woman, V.M., came to the outpatient service of noninvasive cardiovascular diagnostic imaging of the University Hospital “G. Martino” of Messina, in June 2013.

Since March 2008, she was suffering from asthenia, dizziness and occasional syncopes (3-4 times a year), that were independent from physical or emotional stressors and happened anywhere. Because of this, she underwent blood tests, electrocardiogram and tilting testing but all these examinations resulted normal. Doctors that the patient initially consulted supposed that the cause of this was just stress, because in the meantime she was starting her university studies, but symptoms were going to get worse: Tachycardia, insomnia, sweating. Finally, in December 2012, the patient was forced to ask for the intervention of an emergency room. After a short period of observation, she was discharged and turned to a neurologist who advised her to undergo an encephalic magnetic resonance, which revealed an ischemic lesion of 12 ml in the subcortical white matter in the right frontal encefalic region. On the basis of these clinical and instrumental data, it was suspected the presence of a patent foramen ovale (PFO), so the young woman underwent further investigation. A transthoracic echocardiographic (TTE) examination revealed the presence of atrial septal laxity, in the presence of a mild, paradox shunt, during, and after the valsalva maneuver. According to the protocol, the patient underwent a genetic analysis in search of possible mutations of the homocysteine gene and propensity to thrombophilia, but all these tests resulted negative.

Thus, a transcranial Doppler ultrasound was performed injecting shacken saline solution plus gelplex in the vein of the antecubital surface of the arm, and a mild-moderate passage of microbubbles was highlighted in the cerebral circulation (>20 MES without “curtain effect”) during and after the valsalva maneuver.

Subsequently, it was recommended to the young woman to undergo, as soon as possible, a multiplanar transesophageal echocardiographic examination with contrast (cTEE), in order to highlight the presence of a PFO determining shunting of blood from the right to the left atrium and in order to exactly define where it was placed in the interatrial septum, its size and its functional characteristics.

Unfortunatly, during the infusion of shacken saline solution plus gelplex, any shunt was detectable, neither in basal conditions nor during/after Valsalva maneuver because of the presence of a hypertrophic, redundant Eustachian valve [Figure 1], that prevented the microbubbles to reach the right surface of the interatrial septum [Figure 2].

Figure 1

Evidence of a hypertrophic, redundant Eustachian valve

Figure 2

The Eustachian valve preventing the microbubbles to reach the right surface of the interatrial septum

Then a shunting was well demonstrated by color Doppler-guided technique, in the presence of a PFO of about 2 mm, with high sensitivity [Figure 3].

Figure 3

A shunting was well-demonstrated by color Doppler-guided technique

Nowadays, the patient is treated with low doses of acetylsalicylic acid, and she is healthy.

In the embryo, Eustachian valve is a crescent-shaped membrane extending from the lower margin of the inferior vena cava and the ostium of coronary sinus into the right atrium toward fossa ovalis and tricuspid valve. During fetal life, its role is to direct the blood flow to the left atrium through a valve tunnel between the septum primum and secundum called foramen ovale, bypassing the pulmonary circulation. At birth, pulmonary vascular resistances decrease because of the expansion of pulmonary vessels and, subsequently, the pressure in the left atrium exceeds that in the right one. This gradient pushes the septum primum to bear on the secundum, resulting in the functional closure of the foramen ovale. The Eustachian valve loses its function, reducing to an embryo remnant. According to growing evidences, a persistent Eustachian valve is a frequent finding in patients with a PFO. By directing the blood from the inferior cava to the interatrial septum, it may prevent spontaneous closure of PFO after birth and indirectly predispose to paradoxical embolism.[1]

The first diagnosis of PFO by contrast TTE (cTTE) often fails because patients cannot properly perform provocative manouvers (cough, valsalva) or also in the presence of organic heart disease increasing left atrium pressure; in these conditions, the femoral vein rout should be preferred because inferior vena cava flow is just directed forwad fossa ovalis, with a complication rate only slightly higher than the traditional route.[2]

According to recent evidences, the real-time three-dimensional echocardiography over cTTE is a feasible, sensitive, and reproducible technique to detect PFO without the need of saline contrast injection.[3] Its accurancy is close to that of cTEE, which is considered, among diagnostic strategies in cryptogenic stroke, the gold standard in detecting a large right-to-left shunt,[1456] particularly if associated with an atrial septal aneurysm.[7]

However, some authors noticed that in the presence of other anatomical abnormalities predisposing to the paradoxical shunt, in particular a persistent large Eustachian valve, color Doppler TEE is more sensitive than cTEE for detecting PFO, provided that a low pulse repetition frequency is used,[15] so that it simplifies the diagnostic process, reduces the duration of TEE and improves the patient compliance.

This is very important, since the presence of a Eustachian valve in addition to a PFO is likely to increase the risk of clinical disorders as embolism, stroke, platypnea-orthodeoxia syndrome, carcinoid heart disease, atrial flutter, and endocarditis.[8910] Moreover, it has been demonstrated that a redundant Eustachian valve could interfere with the placement of a PFO occluder, and this may influence the choice of treatment (medical or surgical).[1112]

In some recent studies on outcomes with transcatheter closure of PFO, only the identification of an Eustachian valve was associated with recurrent neurologic events[13] and the presence of a prominent Eustachian valve alone or with an atrial septum aneurysm positively correlated with the occurrence of residual shunt.[1415]

In conclusion, our experience confirms that, in the diagnosis of PFO, “the only certainty is (still) doubt” and therefore, the operator must take the most of all the available technical means to make a proper assessment of the individual case, even when the anatomic features make it surprisingly difficult. In particular our case has demonstrated that color Doppler TEE may be superior than traditional cTEE for the diagnosis of PFO and it may define more precisely its position, size, and functional characteristics, when a redundant Eustachian valve is simultaneously present, increasing by itself the risk of thromboembolic complications and also interfering with a proper percutaneous closure of the shunt. Obviously these conclusions should be confirmed by a larger number of cases. In order to define more and more clearly a nosological pattern still very debated by the international scientific community.

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