Sir.—Stern et al, in their article "Heart Failure in Cystic Fibrosis" (Journal 134:267-272, 1980), reconfirmed both the dismal outlook for cystic fibrosis (CF) patients in whom overt right-sided heart failure develops and the relative lack of efficacy of digitalis in treating overt failure.1 However, two questions arise. Fishman2 has described an escalating continuum of pulmonary hypertension, cor pulmonale (secondary enlargement of the right ventricle), and overt right-sided heart failure. The patients described by Stern et al fall into the last category. Do the authors have data on the efficacy of treatment of patients with pulmonary hypertension or with cor pulmonale without overt right-sided heart failure?
The second question concerns the mixed venous Po2 (Pv̄o2) of these patients. Mithoefer et al3 studied the relationship of arterial blood gases (ABG) to Pv̄o2 in 55 adult patients with chronic obstructive lung disease. However, their diagnoses were