Bedside Ultrasound in Fluid Assessment: Correlation of Internal Jugular and Subclavian Vein Diameter Variation with Invasive Right Heart Catheterization

Abstract

Introduction Accurate estimation of fluid status is of paramount importance in patients with heart failure. Frequent invasive right heart catheterization is not feasible and accurate inferior vena cava imaging requires training. Internal jugular vein (IJV) and subclavian vein (SCV) could provide easier alternatives. Methods Patients scheduled to undergo right heart catheterization were prospectively enrolled in the study. Body surface area (BSA) was noted. Patient was positioned flat supine. IJV was imaged at the apex of the right sternocleidomastoid muscle and SCV was imaged at the lateral third of the right clavicle. Using M-mode on a portable ultrasound machine, the maximum (Dmax) and minimum (Dmin) anteroposterior diameters were noted during normal breathing, without applying any external pressure. Respiratory collapsibility was assessed with sniff. Respiratory variation in diameter (RVD) was calculated as: [(Dmax - Dmin)/ Dmax] and expressed as percent. Diameter variation index (DVI) was calculated as: (Dmax - Dmin)/ BSA. Results Total 72 patients enrolled with mean age 61 ± 14 years, mean BSA 2 ± 0.3m2, left ventricular (LV) ejection fraction 45 ± 20%. SCV could not be imaged in 7 patients. Elevated right atrial [RA] pressure (>=10mmHg) patients showed less RVD with resting respiration (14 vs. 41% for IJV and 24% vs. 46% for SCV, p= 0.01) and less likely to show total collapsibility with sniff (table 1). Similarly, DVI was lower with high RA pressure. Dmax alone did not correlate for SCV (table 1). For RA pressure >=10mmHg, lack of IJV collapsibility with sniff had a sensitivity of 84% and ROC area 0.75. Dmax >1cm and RVD =10mmHg. Conclusion There is a positive correlation between fluid status with IJV and SCV diameters (absolute and respiratory variation). The diagnostic performance of these veins was similar to inferior vena cava, but easier to perform.