Demonstration of a relation between urinary digoxin-like immunoreactive substance and cardiac performance.

Objective: To determine the relation between urinary digoxin-like immunoreactive substance (DLIS) and cardiac performance.

Design: Cohort study.

Setting: Echocardiography laboratory of a university-affiliated teaching hospital.

Subjects: Thirty-four individuals referred for echocardiographic studies who had never received cardiac glycosides or other substances known to cross-react with a digoxin radioimmunoassay and had no condition that has been associated with increased DLIS.

Measurements: Cardiac dimensions and indices of cardiac performance derived from echocardiograms and cardiac Doppler flow studies and concentrations of urinary DLIS, creatinine, and electrolytes.

Results: Urinary DLIS ranged from < 0.125 ng (digoxin equivalents) per milliliter (below the sensitivity of the assay) to 0.99 ng/ml, averaging 0.22 +/- 0.24 ng/ml. On bivariate analyses, UDLIS was found to correlate significantly with body weight, left ventricular (LV) end-diastolic dimension, LV fractional shortening, mitral transvalvular flow velocity following atrial systole, and urinary calcium. On multivariate analyses, the association between urinary DLIS (alone or adjusted for urinary creatinine) and LV fractional shortening emerged as the paramount independent relation.

Conclusion: Urinary DLIS can be related to cardiac performance under steady-state conditions. This suggests that DLIS may be a ligand for a cardiac glycoside receptor.