Tricuspid Valve Annulus Size by Echocardiography: Predictor of Cardiac Limitation in Pediatric Pectus Excavatum

Background The severity of pectus excavatum (PEX) as measured by Haller index (HI) does not always correlate with symptoms of aerobic capacity. Transthoracic echocardiograms (TTE) are generally reported as normal which may influence the pediatrician’s decision to refer for corrective surgery. The aim of this study was to find a reproducible TTE marker as an indicator of right ventricular compression and compare it to severity of PEX and cardiopulmonary exercise test (CPET) indices. Methods The study included patients aged 10-19 years with an institution-based protocol for preoperative PEX evaluation with TTE, chest computed tomography (CT) for HI, and CPET from 2015-2021. We divided the patients into two groups, mild/moderate PEX (HI 2-3.5) and severe PEX (HI > 3.5). Tricuspid valve annulus size (TVAS) was compared between the groups as well as with other CPET and TTE indices using Student’s t-test. Spearman’s rank correlation coefficient was used to evaluate correlations between the severity of PEX by HI with the TTE and CPET parameters. Results Of the 124 patients, 82 (66.1%) had severe PEX and 42 (33.9%) had mild/moderate PEX. The mean TVAS z-scores in the mild/moderate PEX group was -1.98(SD 0.51) and -2.24 (SD 0.71) in the severe PEX group (p 0.046). There was a negative correlation between the TVAS z-score and the severity of PEX but this was not statistically significant (r = -0.154, p = 0.087). There was no significant difference in peak oxygen uptake (peak V O2 ) or left ventricular ejection fraction between the severity groups. However, the TVAS z-score positively correlated with peak V O2 (median 43 ml/kg/min, r = 0.023, p = 0.01), peak V O2 percent predicted (median 86%, r = 0.19, p = 0.04), and O 2 pulse (median 12.7 ml/beat, r = 0.20, p = 0.025), and negatively correlated with V E /V CO2 (median 29, r = -0.23, p = 0.01). Conclusion The severity of PEX by HI does not factor in the location of cardiac compression and may not always reflect the degree of cardiac limitation. The Tricuspid valve annulus size is a good TTE indicator of cardiopulmonary compromise from PEX. A TVAS z score <-2 is a good predictor of cardiac compromise in pediatric PEX. This may provide additional functional parameters in the decision-making process for corrective surgery.