Aortic stenosis (AS) is the most prevalent valvular disease in the Western world, and surgical valve replacement remains the standard treatment. However, approximately one third of patients are not referred or are rejected for surgical treatment due to high risk. In recent years, transcatheter aortic valve implantation (TAVI) has emerged as an alternative treatment for these patients.1–3

Different cardiac imaging techniques are essential in the proper selection of patients for TAVI, in intraprocedural monitoring and in subsequent follow-up. Of these techniques, transesophageal echocardiography (TEE) is very helpful for selecting prosthesis size, guiding valve positioning and release, checking the final result and detecting complications.4–6 Moreover, three-dimensional (3D) TEE, due to its ability to characterize soft structures, has a growing role during percutaneous interventions of structural heart disease.

During all the steps of TAVI, mobile echogenic images (MEI) can be observed in some patients. These are defined as small mobile masses, mainly attached to catheters, after valvuloplasty or prosthetic vale implantation, or as remains of the former valve structure.

The aim of our study was to clarify the incidence and clinical significance of MEI detected by 3D TEE, as there are no specifically designed studies for this purpose.

Out of the 104 patients, 81 (78%) underwent TAVI by a transfemoral approach. The clinical characteristics of the study population are summarized in Table 1.

This is the first study specifically focused on MEI during TAVI with TEE monitoring. Our findings show that in up to 11% of cases MEI can be observed during 3D TEE monitoring of TAVI procedures. These images are in most cases a thrombus attached to catheters or remains of former valve structures, which represent a potential source of emboli.7 However, we did not observe an increase in the incidence of periprocedural stroke in patients with MEI (Figure 1).

Figure 1.

An 85-year-old woman with a history of severe aortic stenosis who was accepted for transfemoral valve replacement. After the valve was crossed with the hydrophilic wire, a mobile echogenic image (MEI) was observed by the TEE operator and identified as thrombus. 2000 U of heparin were administered, but unfortunately the thrombus embolized. Cerebral angiography was then performed and showed occlusion of the right mid cerebral artery, and thrombectomy was successfully performed. The patient was discharged without neurological deficit. (A) Three-dimensional determination of aortic valvular area (0.6 cm2); (B and C) mobile echogenic image observed during the procedure and identified as thrombus; (D) macroscopic image of the thrombus that was extracted from the right mid cerebral artery.

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TEE monitoring of non-coronary interventional procedures is an essential safety tool and is considered one of the great challenges of cardiac imaging. Traditional fluoroscopy provides an inaccurate display of soft cardiac structures and is dependent on high doses of iodinated contrast and long exposure to ionizing radiation. Sector scanning and safety of the procedure are better with TEE than with intracardiac echocardiography. In our series, the presence of MEI was highly reproducible by experienced TEE operators, and there was a 100% correlation between two qualified physicians.8 In our experience, 3D TEE is particularly useful for characterization, since real-time imaging provides information about location of MEI, time of onset and relation to cardiac structures, and devices used during the procedure. The characterization of MEI can in some cases help to correct their precipitating factors and thereby minimize the risk of embolism. With the use of 3D TEE, up to 55% of MEI in our series were identified as thrombus attached to the catheters, and probably allowed the operator to modify the precipitating factors and increase the dose of heparin used, thus preventing clinical consequences (stroke or systemic embolism).9,10

Although TAVI is considered an effective and safe therapeutic option for patients with aortic stenosis and high surgical risk, 30-day mortality of patients undergoing this procedure is still around 8%–10%.2 This mortality is largely associated with the main complications inherent to the procedure: vascular complications, device embolization and stroke.11 The prognosis of patients with periprocedural stroke after TAVI is poor and remains one of the limitations of the technique. Previous studies estimated 30-day mortality in these patients at 42.3%, compared with patients without stroke of around 5.1%.12–14

The PARTNER B study showed a higher incidence of stroke at 30 days in patients undergoing TAVI compared with those randomized to medical therapy (5.0% vs. 1.1%, p=0.06).3 The main contributing factors are post-valvuloplasty valve remains, formation of thrombus attached to catheters, erosion of aortic plaques or even thrombosis of the implanted valve. Other factors, such as the presence of spontaneous echo contrast in the left atrium or supraventricular arrhythmias such as atrial fibrillation or flutter, are common and may increase the risk of embolism.15–17 These phenomena were not observed in the PARTNER A study, in which patients undergoing TAVI and surgical aortic valve replacement showed no significant differences in periprocedural stroke rates (3.8% vs. 2.1%, p=0.20).2

In our study, we observed MEI mainly during valve implantation. The Edwards SAPIEN device used in all patients is designed similarly to a stent, being mounted on a balloon, which is inflated to high pressure once it is positioned at the level of the annular plane. Analogously to the compression involved in coronary balloon angioplasty, valve implantation excludes the calcified aortic leaflets, which are compressed between the ring and the valve. Total or partial disintegration of the leaflets, aggravated in most cases by high calcification, makes them into pedunculated mobile structures, with embolic potential.18,19

It is noteworthy that in 45% of cases, the MEI disappeared during the procedure and no correlation with a higher incidence of periprocedural stroke was observed. Previous studies have shown high incidences of brain microbleeds associated with TAVI, with a variable incidence that can approach 70%. There is considerable interest in the clinical, cognitive and functional impairment that these injuries may cause and that in most cases remains unnoticed. The role played in this context by MEI visualized during the procedure remains unclear.20–24

Visualization of MEI during 3D TEE monitoring of TAVI is relatively common (11% of cases in our study). Echocardiographic characterization identifies them in over 50% of cases as thrombi. The clinical implications of this finding are uncertain, as despite their frequency, there was no increased incidence of clinical stroke in this patient population. 3D TEE is a useful tool for diagnosis and can alert the operator to their presence.

The authors have no conflicts of interest to declare.