By Michael H. Crawford, MD, Editor
SYNOPSIS: Using a handheld point-of-care ultrasound device to estimate right atrial pressure from images of the jugular vein resulted in a higher imaging success rate vs. visual inspection and a reasonably accurate estimation, especially in those with elevated right atrial pressures.
SOURCE: Wang L, Harrison J, Dranow E, et al. Accuracy of ultrasound jugular venous pressure height in predicting central venous congestion. Ann Intern Med 2021; Dec 28. doi: 10.7326/M21-2781. [Online ahead of print].
There are difficulties often encountered at the bedside when estimating right atrial pressure (RAP) from the jugular venous pressure (JVP) height. There are several ultrasound techniques, but few have been validated against invasively measured RAP, and some are too time consuming for routine bedside clinical use. Investigators from the University of Utah sought to study whether measuring JVP height by ultrasound (uJVP) in the semi-upright and full upright positions would predict RAP.
The study population consisted of 100 patients undergoing right heart catheterization, largely for heart failure (79%), who underwent uJVP assessment immediately before the catheterization. Two trained physicians performed uJVP using a point-of-care ultrasound (POCUS) device. They recorded uJVP in the semi-upright position (30° to 45°) and at 90°. If the JV was not visualized at 30°, a Valsalva maneuver was used to identify it. If the JV was visualized, these patients were given a JVP value of 5 cm. In those with the JV visible at rest, it was imaged vertically until it tapered to smaller than the adjacent carotid artery throughout the entire respiratory cycle. The vertical height of this taper point was measured from the sternal angle and, per convention, 5 cm were added to arrive at the uJVP height.
Before recording the uJVP, the JVP was visually estimated in the usual fashion. A value > 8 cm was considered elevated. An abnormal mean RAP was considered ≥ 10 mmHg. There was a correlation between invasive RAP and uJVP (r = 0.79). The receiver operating characteristic analysis resulted in an area under the curve (AUC) of 0.84 (95% CI, 0.76-0.92). A uJVP of > 8 cm detected a RAP ≥ 10 mmHg, with a sensitivity of 73% and a specificity of 79%. The uJVP performed better in non-obese patients vs. obese patients (AUC, 0.95 vs. AUC, 0.77). A uJVP was imaged in 100% of the patients, but a visual JVP was seen in only 61%. In those in whom it was visualized, the accuracy was similar to the uJVP (AUC, 0.82). The sensitivity of the visual JVP for detecting a RAP ≥ 10 mmHg was 53% and the specificity was 84%. The two physician scanners were pitted against one another in 20 patients, and the interobserver agreement was good (r = 0.97). The authors concluded POCUS measurements of the uJVP were feasible, reproducible, and accurate at predicting RAP.
COMMENTARY
The bedside assessment of RAP is critical for managing patients with heart failure. The JVP, when detectable, has been shown to be of clinical value. The problem is JVP is not always detectable, especially in obese and thick-necked patients. Small, handheld POCUS devices often linked to a mobile phone deployed at the bedside have shown considerable promise for improving the estimation of RAP. However, assessing the inferior vena cava (IVC) size and respiratory variation may not be useful in the emergency department. Obesity and other conditions (e.g., obstructive lung disease) also affect IVC. Peripheral edema on physical exam can be non-specific in diagnosing heart failure and not useful for the management of heart failure patients. Using the JVP, which is much closer to the heart, remains the best noninvasive way to estimate RAP. Studying POCUS to enhance the estimation of RAP using the JVP is of interest. The study population was one of convenience — patients undergoing right heart catheterization mainly for heart failure-related indications. Also, it was a challenging population, with an average body mass index of 33 kg/m2. The authors used POCUS to enhance the assessment of JVP combined with the convention of adding 5 cm to the measurement to represent the distance from the sternal angle to the mid-RA. Of course, this is an estimate, and it probably is not 5 cm in everyone.
The correlation between uJVP and RAP was reasonably good, but it was better at separating those with an elevated RAP from those with a normal value. The specificity for detecting an RAP ≥ 10 mmHg was 79%. Notably ,with POCUS, the JVP could be seen in 100% of their patients vs. 61% by visual inspection. However, obesity still affected the estimation of RAP with much better accuracy in those without obesity. Additionally, respiratory variation can affect the JVP; when it was excessive, the authors used the end-expiration measurement. This is the case with invasive measurements, where the mean value over a respiratory cycle is used often. Also, the RAP can vary greatly during the cardiac cycle with certain conditions, such as tricuspid regurgitation. This was not addressed in this study. Finally, for those in whom the JVP could be visualized at the bedside, it performed robustly in this study. Thus, when the JVP cannot be seen clearly at the bedside, a POCUS exam in trained hands can enhance its detection and the estimation of RAP.
Using a handheld point-of-care ultrasound device to estimate right atrial pressure from images of the jugular vein resulted in a higher imaging success rate vs. visual inspection and a reasonably accurate estimation, especially in those with elevated right atrial pressures.
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