Effects of digitalis and dobutamine
2. Plus GE, Brower AJ, Clagett OT: Chronic constrictive pericarditis: Roentgenologic findings in 35 surgically proven cases. Proc Staff Meet Mayo Clin 1957;32:555 Reply Dr. Mantri and colleagues argue that because the left atrial to aorta ratio in their patients with constrictive pericarditis was higher than we reported,' limitation of atrial distension is not a feature of constrictive pericarditis and therefore cannot contribute to the pathogenesis of edema in these patients. We found that the
... . We found that the left atrial to aorta ratio in our patients with constrictive pericarditis (1.29; SEM, 0.04) was lower than that in patients with congestive heart failure (1.8; SEM, 0.14) with similar elevation of atrial pressures. This does not imply that the atria in patients with constrictive pericarditis do not dilate. It only suggests that patients with constrictive pericarditis have less distended atria in comparison with patients who have congestive heart failure. We argued that this limitation of atrial distension may explain the substantially lower levels of circulating atrial natriuretic peptide found in these patients. The relatively low levels of atrial natriuretic peptide in constrictive pericarditis probably explain the greater salt and water accumulation that occurs in this condition. These findings are, therefore, consistent with the suggestion that limitation of atrial distension contributes to fluid retention in constrictive pericarditis, and this hypothesis is not challenged by the findings of Mantri et al. There is other evidence to suggest that atrial distension is limited by constrictive pericarditis: Wolozin et a12 showed that in patients with constrictive pericarditis, relief of atrial constriction during pericardiectomy caused an immediate increase in atrial natriuretic peptide, although during this period, the left and right atrial pressures were decreasing. This "paradoxical" response is explained by the increased atrial stretch permitted by stripping the pericardium.