The anteroposterior pericardial sac diameter measured by echocardiography correlates with the volume of pericardial effusion and with effort dyspnea.

AIMS To examine the value of the anteroposterior pericardial sac diameter (APD) for prediction of the volume of pericardial effusion. METHODS AND RESULTS We measured the APD by echocardiography before 52 pericardiocentesis procedures and correlated it with the aspirate volume, etiology, symptoms, and clinical outcome. The volume of the aspirate ranged from 60 to 2300 ml (median 650 ml). The APD (range 8.0 cm-15.9 cm, median 12 cm) correlated well with the cubic root of the volume of the effusion [volume=(0.8APD-0.6)3, r2=0.533, p<0.01]. An APD>or=12 cm had a positive predictive value of 88% and a negative predictive value of 83% for effusion volume above the sample median (>or=650 ml) and a positive predictive value of 100% for effusion in the middle or upper aspirate volume tertiles. Effort dyspnea was more common among patients with APD>or=12.0 cm (n=13) than in those with APD<12.0 cm (n=11) (p=0.007). One-year survival after pericardiocentesis was closely related to the severity of the underlying etiology and was not influenced by the volume of the effusion before aspiration. CONCLUSIONS The APD is a simple, valuable method for non-invasive prediction of pericardial fluid volume. A greater APD is associated with, and may explain, effort dyspnea.