Haemodynamic Impact of Diuretic Therapy in Chronic Heart Failure

An immediate improvement in haemodynamic variables and cardiac performance is achieved in chronic heart failure following diuretic therapy, primarily due to reductions in plasma and extracellular fluid volumes. Humoral markers of these alterations are increased plasma renin, angiotensin and aldosterone levels; these increase maximally over the ñrst week of treatment but attenuate during sustained therapy. There are reciprocal alterations in plasma α-atrial natriuretic peptide levels. These findings suggest that the initial volume contraction is maintained, though somewhat attenuated, during chronic therapy. The neurohumoral consequences of diuretic therapy are of particular interest in heart failure, as they may contribute to diuretic resistance. Activation of the renin-angiotensin system favours the proximal tubular reabsorption of sodium and water, which may result in dilutional hyponatraemia. Diuretics have both direct vascular and non-vascular (volume-dependent) haemodynamic actions. Together these substantially reduce the left heart filling pressure (-29%) with a consequent fall in cardiac output ( 10%). Systemic vascular resistance initially increases but subsequently normali