Loop diuretic therapy in left ventricular systolic dysfunction: has familiarity bred contempt for a critical but potentially nephrotoxic cardio renal therapy?

Long highlighted as the ‘odd man out’ in modern heart failure care, loop diuretic therapy has no cardiovascular outcomes studies for its use in any clinical setting. Although ostracized by some for this evidence gap, diuretic treatment remains beloved for good reason. It is often one of the first to be employed with great effect by the newly qualified physician, salvaging the critical patient from death due to hypoxic acute pulmonary oedema with rapid and gratifying effectiveness. However, has this widely recognized efficacy in this setting masked a potential for iatrogenic renal injury in less abrupt but no less fatal cardio renal decline? The use of aggressive diuretic therapy in heart failure due to left ventricular systolic dysfunction (LVSD) is well known to be associated not only with obvious benefit in acute pulmonary oedema, but it also has a linkage to progressive renal dysfunction and death in chronic LVSD. The practical problem is based on difficulties in the recognition of volume loading of the heart and of renal venous pressure following the relative demise of regular monitoring of invasive pulmonary pressure. Invasive monitoring has been deemed inappropriate by many critical care authorities and is itself, associated with morbidity and mortality concerns. As with every clinical study, the setting is the key to interpretation of therapeutic effects. Cardiorenal failure, marked by hyponatraemia; disordered electrolyte clearance; acidosis and diuretic resistance, is a prominent feature of terminal decline and death in patients with heart failure due to LVSD. Unlike other more dramatic events such as arrhythmic sudden death, this phenomenon has been relatively ignored in the medical literature. Loop diuretic therapy is at the heart of the management of this critical setting and may play a role in the cycle of decline given its independent but unclear linkage to cardiac death.