EFFECT OF ACUTE PERICARDIAL TAMPONADE ON THE RELATIVE CONTRIBUTIONS OF SYSTOLIC AND DIASTOLIC PULMONARY VENOUS RETURN - A TRANSESOPHAGEAL PULSED DOPPLER STUDY

The effect of acute pericardial tamponade on pulmonary venous return w as assessed by transesophageal pulsed Doppler echocardiography. In 14 open-chest anesthetized dogs peak pulmonary venous flow velocities in systole (V-J) and in diastole (VK) were measured during apnea and atri al pacing while acute tamponade was induced by intrapericardial instil lation of 0.9% sodium chloride solution. Before intravascular volume e xpansion, induction of acute tamponade resulted in a significant decli ne in V-K(43 +/- 17 to 19 +/- 8 cm/sec; p < 0.05) but no change in V-J or the ratio V-J/V-K After intravascular volume expansion, induction of acute tamponade resulted in significant reductions in V-J (43 +/- 9 to 29 +/- 10 cm/sec; p < 0.001) and V-K (37 +/- 19 to 15 +/- 11 cm/se c; p < 0.001). The effect was disproportionately greater on V-K, howev er, resulting in a significant increase in V-J/V-K (1.51 +/- 0.84 to 2 .58 +/- 1.41; P < 0.001). The disproportionate effect of acute tampona de on VK suggests that increased pericardial pressure directly constra ins diastolic filling of the left atrium as a conduit to the left vent ricle and that it does not decrease the systolic and diastolic phases of pulmonary venous return uniformly. Intravascular volume expansion i ncreases cardiac output before acute tamponade, but during acute tampo nade it amplifies the disproportionate impact of increased pericardial pressure on left ventricular diastolic filling as the left ventricle is constrained within the fluid-filled pericardial sac.