Echocardiographic assessment of systolic function in dialysis patients.

Echocardiography has been widely used to investigate cardiac function in uraemic patients. There is no doubt about the validity of this technique in certain situations, particularly the demonstration of structural abnormalities and pericardial effusions. However, the assessment of cardiac function by measurement of cardiac dimensions and their rate of change is complicated by the profound influence of altered loading conditions, common in uraemia, on the measurements obtained. This is a particular problem in the assessment of changes in cardiac function during haemodialysis. Even studies utilising isovolaemic dialysis are open to criticism, due to the effects of altered afterload on cardiac emptying. Recently the experimental finding that end-systolic volume is independent of end-diastolic volume and linearly related to afterload has raised the possibility that non-invasive assessment of end-systolic indices may allow load-independent assessment of intrinsic cardiac contractility in patients. However, none of the studies using these indices in uraemic patients has validated the assumption that they are indeed load-independent in this clinical situation. Evidence is presented suggesting that the end-systolic pressure:volume relationship is altered by the administration of a volume load and that manipulation of afterload without autonomic blockade results in markedly increased contractility, presumably due to reflex sympathetic activity. More work is required before these indices are used uncritically in dialysis patients.