The assessment of right ventricular function during and following routine cardiac surgery and the evaluation of preserving pericardial integrity

Abstract

The assessment of right ventricular tricuspid annular velocities and excursion is a robust and common technique of evaluating right ventricular function. The measurement of peak systolic myocardial velocities using pulsed wave tissue Doppler imaging correlates well with estimates of systolic function. It is well known that right ventricular velocities are significantly reduced in patients following cardiac surgery; however the precise cause of this post-operative phenomenon remains unknown despite a number of proposed mechanisms. In this thesis I have carried out observational studies before, during and after surgery in number of patients undergoing different cardiac and thoracic operations. I found using intra-operative transoesophageal and pre and post-operative transthoracic echocardiography that the onset of right ventricular myocardial velocity reduction is immediately marked by the full opening of the pericardium following traditional-midline thoracotomy. I also identified that this reduction is present in all operations where the pericardium is opened fully regardless of the underlying pathology i.e. cardiac or noncardiac. By measuring simultaneous pericardial support pressures and intra-operative transoesophageal velocities during a staged pericardiotomy I also showed, in patient where there pericardium was to be opened fully, that this loss occurs consistently and specifically during the second-stage of a three-staged pericardiotomy which demonstrated in a novel way the substantial and localised mechanical support provided by the intact pericardium. Furthermore, I found that right ventricular longitudinal velocities do not reduce in those patients undergoing minimally invasive cardiac surgery where pericardial integrity is preserved. I believe this thesis has helped to prune the range of possible mechanism for this post operative phenomenon which is frequently seen and commented upon.