Left ventricular function during pregnancy.

As emphasized by Watkins et al.,9 the variability in plasma renin activity in CHF is explained by the degree of compensation in maintaining arterial pressure and plasma volume; the latter measurement was not obtained in the Curtiss or Gavras study. The observations in these two recent studies reaffirm the importance of the RAA system in maintaining systemic vascular resistance (SVR) in CHF. Curtiss's observation of a paradoxical correlation between the RAA system and circulating catecholamines is most provocative and suggests an important synergistic action; this deserves further investigation. Recently Freeman et al.4 investigated the role of the RAA system in the mechanism of edema formation in CHF in caval constricted dogs. This group observed significant increases in sodium excretion both in acutely and chronically treated animals. Their conclusions emphasized the direct tubular affect of aldosterQne in this sodium retaining state; one must, however, conclude that a decrease in both SVR and renal vascular resistance is equally important. The RAA system clearly plays a critical role in the pathogenesis of the syndrome of CHF. Continuing studies should increase our understanding of its role in systemic and renal hemodynamic adjustments in heart failure. As demonstrated by Watkins,' the compensatory increase in RAA system activity is crucial to the maintenance of arterial pressure; therefore, caution must be taken in the use of CEI and CHF inasmuch as profound hypotension and its serious consequences may occur in an unidentifiable group of patients. JOHN C. BURNETT, JR., M.D. Mayo Foundation Rochester, Minnesota 55901