Pericardial rub in pericardial effusion: lack of correlation with amount of fluid.

The relation between the amount of pericardial fluid and the presence of a pericardial rub was examined in 76 patients with echocardiographic evidence of pericardial effusion. A pericardial rub was noted in 4 of 13 patients with small pericardial effusion (less than 100 ml), in 23 of 40 patients with moderate effusion (100 to 500 ml), and in ten of 23 patients with a large effusion. No difference in the amount of fluid was demonstrated in the group of patients with a rub when compared to the group without one. There was a statistically significant relation between the presence of a rub and the cause of the effusion. No inference as to the amount of pericardial fluid should be drawn from the presence or absence of a pericardial rub.