Inferior Vena Cava Diameter and Left Atrial Diameter Measure Volume but Not Dry Weight

BACKGROUND AND OBJECTIVES: Hypervolemia is an important and modifiable cause of hypertension. Hypertension improves with probing dry weight, but its effect on echocardiographic measures of volume is unknown. DESIGN, SETTING, PARTICIPANTS, & MEASUREMENTS: Shortly after dialysis, echocardiograms were obtained at baseline and longitudinally every 4 weeks on two occasions. Among 100 patients in the additional ultrafiltration group, 198 echocardiograms were performed; among 50 patients in the control group, 104 echocardiograms were performed. RESULTS: Baseline inferior vena cava (IVC)(insp) diameter was approximately 5.1 mm/m(2); with ultrafiltration, change in IVC(insp) diameter was -0.95 mm/m(2) more compared with the control group at 4 weeks and -1.18 mm/m(2) more compared with the control group at 8 weeks. From baseline IVC(exp) diameter of approximately 8.2 mm/m(2), ultrafiltration-induced change at 4 weeks was -1.06 mm/m(2) more and at 8 weeks was -1.07 mm/m(2) more (P=0.044). From a baseline left atrial diameter of 2.1 cm/m(2), ultrafiltration-induced change at 4 weeks was -0.14 cm/m(2) more and at 8 weeks was -0.15 cm/m(2) more. At baseline, there was no relationship between interdialytic ambulatory BP and echocardiographic parameters of volume. The reduction in interdialytic ambulatory BP was also independent of change in the echocardiographic volume parameters. CONCLUSIONS: The inferior vena cava and left atrial diameters are echocardiographic parameters that are responsive to probing dry weight; thus, they reflect excess volume. However, echocardiographic volume parameters are poor determinants of interdialytic BP, and their change does not predict the BP response to probing dry weight.