Egbe AC, Connolly HM, Pellikka PA, Anderson JH, Miranda WR. Circ Cardiovasc Imaging. 2022 Sep;15(9):e014308. doi: 10.1161/CIRCIMAGING.122.014308. Epub 2022 Sep 20.PMID: 36126125
Take Home Points:
- In this retrospective, single center study, the authors aimed to correlate between invasively measured right atrial pressures (RAP) and non-invasively assessed RAP using echocardiographic measurement of the inferior vena cava (IVC) diameters and inspiratory collapsibility. Echocardiographic images from 918 ACHD patients aged>18 years who had a right heart catheterization within 7 days of the echo study were included, and patients with a Fontan circulation were excluded.
- The study cohort was divided into derivation and validation cohorts, each consisting of 459 patients. The definition for elevated RAP was >10 mm Hg.
- The prognostic implications of elevated RAP were also compared between the invasive and non-invasive measurement methods. For this purpose, a composite end point consisting of heart failure hospitalization, heart transplant, or cardiovascular death occurring from the time of cardiac catheterization to the end of the study period was used.
- The most common congenital heart lesions were tetralogy of Fallot (n=264, 29%), coarctation of aorta (n=120, 13%), and Ebstein anomaly (n=71, 8%). Tetralogy of Fallot was more common in the derivation cohort but the other diagnoses were equally distributed between the 2 groups. Table 1 shows the hemodynamic measurements of the cohort, divided into the derivation and validation groups.
Commentary from Dr. Yonatan Buber (Seattle, USA), section editor of ACHD Journal Watch
Table: invasive and noninvasive hemodynamic indices of the study patients.
As shown in Table 2, the correlation between the maximal diameter of the IVC (IVC max), the minimal diameter of the IVC (IVC min) and the collapsibility index of the IVC (IVCCI) and the invasively measured RAP were excellent. Similar strong correlations were present when the IVC diameters were indexed to the body surface area. Reproducibility of the reads was excellent with minimal inter-observer variability.
Table 2. Correlation Between IVC Dynamics and Invasively Measured RAP in the Derivation Cohort
- Using logistic regression and receiver operating characteristic curve, IVC max of 1.8 cm, IVC min of 1.2 cm and IVCCI of 60% were found to be the best discriminatory points for invasively measured elevated RAP of >10 mm Hg. However, IVCCI<60% had the best discriminatory power to identify patients with increased RAP (AUC 0.84 [95% CI, 0.80–0.88]; P<0.001), with IVCCI <60% providing the optimal cutoff point to detect increased RAP with a sensitivity of 93% and specificity of 89%.
- RAP was estimated from IVC dynamics using the formula: (RAP=16.89–0.12 [IVCCI])
- Similarly, in the validation cohort, IVCCI <60% had a more robust diagnostic performance as compared with IVC max >1.8 cm and IVC min >1.2 cm. Furthermore, IVCCI <60% had superior diagnostic performance as compared to the American Society of Echocardiography (ASE) criteria for the diagnosis of elevated RAP (IVC max >2.1 cm and IVCCI of<50%)
- Several sub-group analyses were performed, and showed that among patients with right heart disease, IVCCI <60% performed better the ASE recommended criteria for the diagnosis of elevated RAP.
- In patients without right heart disease and in patients with>moderate degree of tricuspid valve regurgitation this effect was much less robust. There was no difference between men and women and between patients who did or did not undergo prior sternotomies or thoracotomies.
- During a median follow up of 6.9 years, 25% of the study patients experienced an outcome event. As shown in Table 6 of the manuscript, invasively measured RAP and estimated RAP based on IVCCI had a comparable prognostic power, while estimated RAP based on ASE criteria had a less robust prognostic power.
Table 6. Multivariable Cox Models Showing Risk Factors Associated with Cardiovascular Events
Right atrial pressure is a good metric surrogate of right heart function and reflects right ventricular diastolic function, right atrial compliance and general function, and overall volume status. Due to various reasons that include the native anatomical lesion, prior surgeries, lung disease and others, these factors are often different and abnormal in ACHD patients, particularly those with lesions involving the right heart. The finding by Egbe et al. that the cutoff values for the diagnosis of elevated RAP in a large group of ACHD patients were different from those used for the general population should therefore come as no surprise. This is a meticulously performed study that identifies a new cutoff value in the form of IVCCI <60% as the best method to diagnose elevated RAP in ACHD patients, especially those with right heart disease. The authors also provide a useful formula (RAP=16.89–0.12 [IVCCI]) which can be used to divide the patients into 3 categories based on estimated RAP (0–5, 6–10, and >10 mm Hg).
The lower cutoff values of IVC max (1.8 cm in this study vs 2.1 cm in the general population) to diagnose elevated RAP likely reflect high incidence of low-compliant right atria and right ventricles in the population, which is more prominent in patients with right heart disease. The reason why an IVCCI<60% (a value that is higher than traditional 50% used by the ASE in the general population) was found to have the strongest correlation with elevated RAP in not entirely clear. A possible explanation offered by the authors is that ACHD patients are younger and are potentially able to generate more negative intrathoracic pressure, and hence a lower IVC collapsibility will correlate with higher RAP as compared to the older patients with acquired heart disease. While this is a possibility, it is also well accepted that accurate measurement of IVC collapsibility is notoriously difficult and is associated with high rates of inter-observer variability (although apparently not in this study). Outside validation of this study’s results will be needed to confirm this finding and to make it generalizable to other medical centers around the world.