AbstractThe importance of quantifying right ventricular (RV) function has become clear in recent years. Following adult cardiac surgery right ventricular dysfunction has emerged as a significant cause of morbidity and mortality, particularly after transplantation and during left ventricular (L V) assist device support. In the field of congenital heart disease, which has undergone rapid development in the last 20 years, many of the anatomical defects and corrective procedures directly involve the right ventricle. Furthermore the successful therapy for hypoplastic left heart syndrome has provided a group of patients in whom the right ventricle is the only pumping chamber.
Twenty-five years ago Hiroyuki Suga described the active and passive properties of an isolated left ventricle as constants that relate pressure to volume during systole and diastole and proposed the model of "time-varying elastance". One success of this approach has been the development of contractile indices that are generally independent of loading conditions. These indices, Emax, preload recruitable stroke work index and dP/dtmax-end-diastolic volume have been used extensively in the assessment of left ventricular function in clinical and experimental studies. However, the evaluation of right ventricular pump performance is confounded by its complex geometry, which precludes an accurate volume determination using currently available imaging techniques. Furthermore indices developed for L V assessment may not be applicable in the quantification of right ventricular function because of the major anatomical and physiological differences between the two chambers.
This thesis records my research work on assessment of right ventricular function using the conductance catheter method to measure real-time continuous right ventricular volume. The initial part of the thesis, chapters 2 and 3,, deals with the 2 accuracy and limitations of the conductance method in measuring right ventricular volume. In chapter 2 conductance-derived right ventricular volumes are correlated with "real" volume in an excised porcine heart. Chapter 3 deals with the conductance method in the intact circulation and specifically examines the role of right ventricular parallel conductance (a major limitation of the method) in this situation.
The second part of the thesis involves quantifying right ventricular contraction in the pressure-volume plane. In chapter 4, RV contractility is determined using analysis of multiple pressure-volume loops over a loading range; the effect of altered inotropic conditions on RV systolic function is examined. Finally, chapter 5 deals with the effect of isolated RV infarction on right and left ventricular function, and the effect of partial unloading by a cavo-pulmonary shunt.
|Date of Award||Dec 2000|
|Supervisor||Lishan Aklog (Supervisor), John Byrne (Supervisor) & Desmond Allen (Supervisor)|