Use of intra-cardiac ultrasound in the diagnosis of prosthetic valve malfunction.

A 46-year old lady was under regular follow up for aortic valve replacement done in 2002 for aortic stenosis. The valve was a Carbomedics 19 mm bi-leaflet aortic valve prosthesis for which she had adequate anticoagulation since implantation. She had a past history of end stage renal failure, type 2 diabetes, hypertension, cerebrovascular disease and systemic lupus erythematosus. She was asymptomatic and had a routine transthoracic echocardiogram performed which revealed that her aortic valve prosthesis was well seated with an elevated velocity across the valve; the aortic valve leaflets were poorly visualised but appeared to be mobile. A transoesophageal echocardiogram (TOE) confirmed the markedly increased forward velocity across the aortic valve (maximum velocity 4.6 m/s) with small aortic root raising the possibility of pressure recovery phenomenon. Once again the leaflets were not clearly seen but appeared mobile despite the use of deep trans-gastric view. Fluoroscopy was performed and revealed that one of the leaflets was not moving. The patient had an intra-cardiac ultrasound scan (ACUSON AcuNav; Siemens) with the probe of the scanner within the right atrium. A long-axis view demonstrated the prosthetic aortic valve leaflets clearly (Fig. 1). A short-axis view of the prosthetic valve revealed an echogenic area at the six o'clock position; this may be due to pannus formation (Fig. 2); colour flow across the valve during systole revealed absence of colour flow though one of the leaflets due to the leaflet being stuck (Fig. 3). The sewing cuff of the Carbomedics valve is coated with biolite carbon, which is an anti-thrombotic agent that prevents adhesion of thrombus or pannus on the sewing cuff. There are few reports of Carbomedics valve dysfunction by pannus formation in the mitral position but none in the aortic position. Fluoroscopy can be used to visualize mobility of valve leaflets but is unable to identify thrombus/pannus formation that may be causing the valve to stick. Intra-cardiac echocardiography (ICE) can provide additional information regarding potential causes of valve dysfunction such as pannus/thrombus formation. However, ICE does suffer from the same limitations as TOE in obtaining sufficiently adequate images of the aortic valve to allow appropriate assessment of leaflet motion and insight into flow channels; it is also more invasive and expensive compared with other imaging modalities. In our patient ICE provided better images than TOE, possibly due to the closer proximity of the probe to the aortic root compared with TOE. ICE is a novel tool in the assessment of prosthetic valve function, which can complement data obtained from transthoracic/transoesophageal echocardiography and fluoroscopy.