FORUM MŁODYCH CHIRURGÓW
Intraoperative use of transoesophageal echocardiography in routine mitral valve replacement – a justified standard

Introduction
Intraoperative transoesophageal echocardiography (TEE) is a valuable tool with regard to cardiac surgery, particularly in valve repair [1-3] and complex congenital lesions surgery [4].
However, its routine application in valve replacement surgery is less clear. Recent studies have provided additional data on the importance of intraoperative TEE in valve replacement operations with an emphasis on the pre-bypass data [4-11]. Nevertheless, the American College of Cardiology/ American Heart Association (ACC/AHA) Task Force, in its 2006 update for the clinical application of echocardiography, considered intraoperative TEE in valve replacement as only a class IIA indication, namely, a condition for which there is conflicting evidence and/or a divergence of opinion about the usefulness and/or efficacy of the procedure, but the weight of evidence and/or opinion is in favour of its usefulness and/or efficacy [12].
The preoperative TEE assessment may introduce important modifications into the surgical plan and the post-pump assessment, as well as providing quality control of the surgical result including the efficiency of the removal of air and the haemodynamic status in terms of effective intravascular volume and biventricular contraction [4].
We would like to report a case of a stuck prosthetic valve, detected by intraoperative TEE, despite an uneventful weaning from cardiopulmonary bypass (CPB).

Case
A 71-year-old woman was electively admitted to the hospital for surgical treatment of mild aortic stenosis, mixed mitral valve disease and coronary artery disease. She was in CCS class 1 and NYHA class 3. Her preoperative risk assessed by Parsonnet score was 23, by EuroSCORE 6 and by logistic EuroSCORE 4.52. Preoperative TTE revealed: good left ventricle function, calcified non-coronary cusp of aortic valve causing moderate aortic stenosis with mean gradient across the valve 28 mmHg. Mitral valve in preoperative assessment was calcified with mild stenosis and severe regurgitation. Coronary angiogram revealed occluded right coronary artery (RCA). Intraoperative pre-CPB TEE confirmed the results of preoperative TTE. During surgery single vein graft to distal RCA was anastomosed. Because of extended rheumatic mitral valve disease with severe calcifications, both leaflets were removed without sparing of subvalvular apparatus. The mitral valve was replaced with a mechanical St. Jude prosthesis size 27 mm in the anti-anatomical position. Intraoperative assessment of the aortic valve revealed restricted movement of the non-coronary cusp due to severe calcifications causing moderate stenosis. During surgery calcifications were removed, restoring good leaflet movement in postoperative TEE. After completion of the heart surgery, the patient was weaned from CPB under no inotropic support without difficulty, and her haemodynamic condition was stable. However, when the prosthesis was assessed for the first time using TEE during weaning from CPB, one of the leaflets of the prosthesis was seen to be stuck in the closed position (Fig. 1). The next assessment after weaning from CPB revealed movement of both leaflets although there was an extra echo shadow above the valve in the left atrium (Fig. 2). CPB was instituted again, cardioplegia was given, and the left atrium was reopened. On inspection of the prosthesis, both leaflets were moving; however, on the side of the anterolateral commissure there was residual tissue (secondary chord) coming from the left ventricle across the valve. Normal valve function was restored by resection of the extra tissue. The further postoperative period was uncomplicated and the patient was discharged home 10 days after surgery.

Discussion
Intraoperative TEE during cardiac surgery permits immediate assessment of left ventricular function and native or prosthetic valve function and de-airing, immediate detection of aortic disease such as dissection or atheromatous changes of the aorta, and confirmation of the position of an intra-aortic balloon pump [1, 2]. In particular, recent adoption of frequent intraoperative assessment of valve repair using TEE may contribute significantly to the success and popularity of mitral valve repair [1, 3]. In recent years, the results of valve replacement have improved, and controversy persists as to whether routine intraoperative TEE is indicated in valve replacement, as opposed to its established indication in repair.
Leaflet sticking due to residual tissue like that detected in the present case is believed to be rare [1-3], and this was the first case in our institution. Elsewhere, Kumano and associates [1] presented a case of blocked CarboMedics prosthesis in the mitral position. In their case weaning from CPB was under inotropic support also without any difficulty. In this case prosthetic valve dysfunction was due to residual tissue [1]. Similar complications were described by Shapira and associates in 3 cases [4]. Also Jaggers and associates [15] described a case of MVR in which one leaflet of a St. Jude Medical mitral prosthesis had become stuck, although the underlying cause of this valve dysfunction was not identified. In their case, weaning from CPB could not be achieved because the patient developed marked pulmonary hypertension. Upon assessment using TEE, they found a stuck leaflet, and operatively corrected the valve dysfunction.
Successful management in our case resulted from the use of TEE in the initial phase of operation, permitting assessment of the unexpectedly malfunctioning prosthetic valve immediately after the termination of CPB. Because patients may be haemodynamically stable despite prosthetic valve dysfunction undetected by the electrocardiogram, arterial pressure, or Swan-Ganz catheter monitoring, intraoperative TEE should be added to other routine assessments in valve replacement operations to prevent postoperative complications. Valves like St. Jude even with one leaflet blocked may provide periods of adequate cardiac output with transient periods of haemodynamic instability. Moreover, postoperative instability with an extra echo shadow above the prosthetic valve may suggest endocarditis requiring urgent redo operation.
According to Daniel and associates [16], complications associated with TEE occurred in 18 cases (0.18%) of 10,218; bleeding due to insertion occurred in only two, including a case where bleeding was caused by an oesophageal tumour. In our institution, TEE monitoring has started to be used routinely in the initial phase of cardiac surgery without complications. Insertion of the TEE probe should precede CPB with its associated systemic heparinization in order to avoid bleeding.
In conclusion, we emphasize the importance of performing routine intraoperative TEE in cardiac surgery from the initial phase of operation, for immediate management of unpredicted events.

References
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