EDITOR—The burden on echocardiography services could indeed be reduced if natriuretic peptide concentrations plus electrocardiography were used as screening tools for left ventricular systolic dysfunction.1 Nielsen et al's paper confirms the high negative predictive value of these tests. Concomitant drug treatment could, however, be a crucial contaminating factor.

The use of natriuretic peptides to diagnose left ventricular dysfunction in patients who are already taking cardiac drugs deserves particular attention. Diuretics, digoxin, and angiotensin converting enzyme inhibitors reduce natriuretic peptide concentrations.2 Especially important is the fact that frusemide (furosemide) reduces these concentrations3 but will have virtually no effect on an echocardiogram; it will not alter left ventricular dysfunction. Obviously, therefore, frusemide could severely distort the relation between natriuretic peptides and the echo finding of left ventricular systolic dysfunction.

The predictive value of natriuretic peptides could conceivably be considerably affected by the presence of frusemide and other cardiac drugs. This could explain why …