ATRIAL WALL TENSION CHANGES AND THE RELEASE OF ATRIAL-NATRIURETIC-FACTOR ON RELIEF OF CARDIAC-TAMPONADE

Cardiac tamponade causes elevation and equalization of cardiac filling pressures, sodium and water retention, and a paradoxically low plasma atrial natriuretic factor (ANF) concentration despite increased intra atrial pressures. Recent reports suggested that plasma ANF concentrati ons rise after relief of tamponade. The purposes of the present study were (1) to determine the time course and extent of ANF release on rel ief of cardiac tamponade; (2) to measure the atrial transmural wall pr essures, atrial sizes, and atrial wall tension changes associated with relief of tamponade; and (3) to determine the biologic activity of el evated plasma ANF during and after relief of tamponade. We sampled blo od for ANF and cyclic guanosine monophosphate (cGMP) immediately befor e and up to 24 hours after relief of cardiac tamponade in 10 patients. Atrial and pericardial pressures were measured immediately before and shortly after pericardiocentesis, and atrial dimensions were determin ed by two-dimensional echocardiography before and within 1 hour after the tap. Urine volumes were measured in 8-hour increments before and a fter the procedure. Relief of cardiac tamponade was associated with a prompt and massive increase in plasma ANF concentrations, reaching pha rmacologically active levels. The rise in ANF was negatively correlate d with atrial pressures but positively correlated with atrial transmur al pressures, atrial sire, and calculated wall tension. Plasma ANF lev els peaked at 515 +/- 95 pg/ml 40 minutes after relief of tamponade an d leveled off at 140% to 180% of the pretap concentrations. Plasma cGM P exhibited a slightly delayed but similar time course to the rise in ANF levels, and urine flow rate increased fourfold in the 8 hours afte r relief of tamponade. We conclude that (1) the relief of cardiac tamp onade stimulates the release of atrial natriuretic factor by increasin g atrial transmural wall pressures, atrial Size, and calculated wall t ensions; (2) evidence for the biologic activity of the increased plasm a ANF concentrations is provided by the temporal association of increa sed cGMP levels and increased urine flow rate; and (3) that the releas e of ANF is governed by changes in atrial transmural wall pressures an d calculated atrial wall tensions.