Transoesophageal echocardiography in mitral valve surgery
November 19, 2009 2 Comments
Blog Post by Barbora Parizkova, Stephen Webb
Mitral valve (MV) repair and MV replacement are classified as Class I and IIA indications for intraoperative transoesophageal echocardiography (TOE) by the American College of Cardiology and the American Heart Association.
Recently the cause of MV pathology in most industrialised nations has changed over the last decades from predominantly rheumatic to degenerative and ischemic valve disease. Rheumatic heart disease usually presents as mitral stenosis, while myxomatous degeneration is the most common cause of native mitral regurgitation. Mitral regurgitation can also develop in patients with left ventricular (LV) dysfunction, endocarditis or acute myocardial infarction with papillary muscle rupture.
The MV consists of a fibrous annulus, two leaflets and the subvalvular apparatus. The anterior mitral valve leaflet originates from the anterior part of the MV annulus and is continuous with the aortic root. The posterior mitral valve leaflet originates from the free LV wall, enclosing the greater part (about 70%) of the MV annulus, which is poorly supported and therefore prone to dilatation under pathological conditions. The subvalvular apparatus consists of the left ventricular wall, papillary muscles and chordae tendineae.
To determine the feasibility of valve reconstruction, TOE is vital. The TOE examination consists of four standard mid-oesophageal views (four-chamber, commissural, two chambers and long-axis) and two transgastric views (basal short axis, two chamber). In each view the valve should be assessed with 2-D imaging and colour flow Doppler. Evaluation of the transmitral and pulmonary venous Doppler waveforms should be part of the complete examination. The annulus should be screened for calcification and annulus dilatation is determined by measuring the anteroposterior diameter. A diameter of less than 35 mm may be considered normal. The MV leaflets should be screened for thickening, calcification or excessive leaflet tissue.
The information from TOE examination is important for the choice of treatment. The postoperative TOE examination assesses the result of the surgical procedure.
Following MV repair, the presence of residual regurgitation, systolic anterior motion (SAM) or valvular stenosis must be assessed. After MV replacement any significant paravalvular leak must be excluded.
For more information, please see Core Topics in Cardiac Anaesthesia, 2nd edition, edited by Joseph Arrowsmith and Jonathan Mackay, published by Cambridge University Press.