Copyright © 1989 by the European Society of Cardiology.
© 1989 The European Society of Cardiology
What is the ideal orientation of a mitral disc prosthesis? An in vivo haemodynamic study based on colour flow imaging and continuous wave Doppler
Thoraxcenter, University Hospital Rotterdam-Dijkzigt and Erasmus University Rotterdam The Netherlands
Received 11 May 1988; revised 20 June 1988; .
Correspondence: G. R. Sutherland, Deapartment of Echocardiography, Thoraxcenter, Erasmus University Rotterdam, P.O. Box 1738, 3000 DR Rotterdam, The Netherlands.
Abstract
Doppler colour flow imaging demonstrates normal laminar flow to enter the left ventricle in diastole through the mitral inflow tract located posteriorly in the left ventricle. Laminar flow then passes around the left ventricular apex to the anteriorly located outflow tract. As this is the normal physiologic flow pattern, it would seem appropriate that in the surgical implantation of a mitral tilting disc prosthesis the greater orifice should be directed posteriorly to mimic the normal native valve flow pattern.
To determine whether variable positioning of the greater orifice had any significant haemodynamic conse–quences, intracavitary blood flow patterns were studied in 30 patients with mitral Björk-Shiley prostheses variously orientated in the mitral orifice. The orientation of the greater orifice (OGO) of the prosthesis was determined by fluoroscopy and the pattern of the left ventricular inflow from Doppler colour flow imaging. Twelve patients had their OGO and inflow directed towards the inflow tract (orientation I): nine patients had their OGO and inflow directed anteriorly towards the outflow tract (orientation II) and nine patients had their prosthesis with OGO and inflow in an intermediate position (orientation III). The mean prosthetic diastolic gradient, calculated using continuous wave Doppler, averaged 2.8 mmHg (±0.5mmHg) for the 25-mm prosthesis in orientation I, but 6.0 mmHg (±0.7mmHg) for the same size prosthesis in orientation II and 5.8 mmHg (±0.9 mmHg) with a 25-mm prosthesis in orientation III. Similarly, for prostheses of 27 mm and 29–31 mm the lowest mean diastolic gradient was found in orientation I (2.7 mmHg ± 0.8 and 2.8 mmHg ± 0.5, respectively). However, the difference in mean gradient between orientations I, II (5.6 mmHg±0.2 and 3.6 mmHg) and III (5.1 mmHg ±0.7 and 3.8 mmHg ±0.4) was less pronounced for the larger prostheses. From these results, it was concluded that the best haemodynamic result is obtained by a mitral disc prosthesis when its greater orifice is orientated posteriorly. This would appear to be especially important for the smaller disc prosthesis.
Key Words: Mitral valve prosthesis • colour flow imaging • continuous wave Doppler