From the Guidelines
The ECHO IVC criteria for right atrial pressure (RAP) estimates uses inferior vena cava (IVC) diameter and collapsibility during respiration to predict central venous pressure, with a normal IVC diameter (<2.1 cm) and >50% collapse suggesting a low RAP of 0-5 mmHg, a dilated IVC (>2.1 cm) with <50% collapse indicating a high RAP of 10-20 mmHg, and intermediate findings suggesting an intermediate RAP of 5-10 mmHg 1. The criteria are based on the measurement of the IVC diameter and its collapsibility during inspiration, which correlates with RA pressure.
- A normal IVC diameter (<2.1 cm) with >50% collapse during inspiration suggests a low RAP of 0-5 mmHg.
- A dilated IVC (>2.1 cm) with <50% collapse indicates a high RAP of 10-20 mmHg.
- Intermediate findings, such as a normal IVC with poor collapse or a dilated IVC with good collapse, suggest an intermediate RAP of 5-10 mmHg. This assessment should be performed with the patient in a supine position, measuring the IVC diameter approximately 1-2 cm from the right atrial junction, and observing respiratory variation during quiet breathing 1. The technique is valuable because it provides a non-invasive method to estimate right heart filling pressures, which helps in evaluating volume status, right heart function, and guiding management of conditions like heart failure, pulmonary hypertension, and shock 1. However, the accuracy may be affected by mechanical ventilation, severe tricuspid regurgitation, or constrictive pericardial disease. It is essential to consider these limitations when interpreting the results of the ECHO IVC criteria for RAP estimates. The most recent and highest quality study 1 supports the use of these criteria for estimating RAP, and it is recommended to use this approach in clinical practice.
From the Research
ECHO IVC Criteria for RAP Estimates
The ECHO IVC criteria for estimating right atrial pressure (RAP) involve measuring the inferior vena cava (IVC) diameter and its respirophasic variations. The following are some of the key criteria:
- IVC maximum diameter cut-off for detecting RAP >10mmHg: 19mm (sensitivity, 75%; specificity, 78%) 2
- Percent collapse cut-off for detecting RAP >10mmHg: 30% (sensitivity, 75%; specificity, 83%) 2
- IVC size cutoff with optimum predictive use for RAP above or below 10 mm Hg: 2.0 cm (sensitivity 73% and specificity 85%) 3
- Optimal IVC collapsibility cutoff: 40% (sensitivity 73% and specificity 84%) 3
- Caval index (percent collapse) cutoff for discriminating RA pressure ≥ or < 10 mm Hg: 50% (sensitivity and specificity maximized at this level) 4
Comparison of Criteria
The optimal cut-offs for IVC maximum diameter and percent collapse may vary depending on the population being studied. For example, the cut-offs reported in 2 were smaller than those previously reported in patients from Western countries. In contrast, the study in 3 reported cut-offs that were similar to those reported in other Western populations.
Limitations of IVC-Based Estimates
While IVC-based estimates of RAP can be useful, they have limitations. For example, the study in 5 found that a multi-parametric approach using IVC indexes extracted by a semi-automated approach was more accurate than traditional IVC-based estimates. Similarly, the study in 6 found that a multiparametric estimate of RAP (eRAPmean) did not provide an advantage over IVC-based estimates (eRAPIVC) despite being more complex and time-consuming.