Increased plasma concentration of atrial natriuretic factor with squamous cell carcinoma invasion of the right and left atria of the heart

Atrial natriuretic factor is a new peptide hormone synthesized in the heart which has potent natriuretic, diuretic, and vasodilatory properties. A 47-year-old man with squamous cell carcinoma of the lung resected 6 months previously presented with syncope secondary to hypotension and a low serum sodium. He was evaluated to determine if atrial natriuretic factor (ANF) might be the etiology of this clinical picture. His plasma concentration of atrial natriuretic factor was increased three-fold over that of 70 normotensive persons. Further evaluation revealed metastatic lesions in the right and left cardiac atria with the mass on the left occluding 75% of the left atrial chamber. The mass effect in the atria increasing atrial stretch and atrial pressure one would expect was the main contributor to the increased ANF level. The contribution of direct tumor invasion into the atria and/or production of atrial natriuretic factor by the tumor itself to produce this elevated plasma level of atrial natriuretic factor could not be determined, but this markedly elevated level of atrial natriuretic factor does appear to be the etiology of this patient's clinical picture.