Chest Shape Influences Ventricular-Arterial Coupling Parameters in Infants with Pectus Excavatum

BACKGROUND: The present study was designed to investigate the possible influence of chest shape, noninvasively assessed by modified Haller index (MHI), on ventricular-arterial coupling (VAC) parameters in a population of term infants with pectus excavatum (PE). METHODS: Sixteen consecutive PE infants (MHI >2.5) and 44 infants with normal chest shape (MHI ≤2.5) were prospectively analyzed. All infants underwent evaluation by a neonatologist, transthoracic echocardiography, and MHI assessment (ratio of chest transverse diameter over the distance between sternum and spine) within 3 days of life. Arterial elastance index (EaI) was determined as end-systolic pressure (ESP)/stroke volume index, whereas end-systolic elastance index (EesI) was measured as ESP/left ventricular end-systolic volume index. Finally, VAC was derived by the Ea/Ees ratio. RESULTS: At 2.1 ± 1 days after birth, compared to controls (MHI = 2.01 ± 0.2), PE infants (MHI = 2.76 ± 0.2) were diagnosed with significantly smaller size of all cardiac chambers. Biventricular systolic function, left ventricular filling pressures, and pulmonary hemodynamics were similar in both the groups of infants. Both EaI (4.4 ± 1.0 mmHg/ml/m(2) vs. 3.4 ± 0.6 mmHg/ml/m(2), P < 0.001) and EesI (15.1 ± 3.0 mmHg/ml/m(2) vs. 12.7 ± 2.5 mmHg/ml/m(2), P = 0.003) were significantly increased in PE infants than controls. The resultant VAC (0.30 ± 0.10 vs. 0.30 ± 0.08, P > 0.99) was similar in both the groups of infants. Both EaI (r = 0.93) and EesI (r = 0.87) were linearly correlated with MHI in PE infants, but not in controls. On the other hand, no correlation was found between MHI and VAC in both the groups of infants. CONCLUSIONS: Chest deformity strongly influences both Ea and Ees in PE infants, due to extrinsic cardiac compression, in the absence of any intrinsic cardiovascular dysfunction.