Occult RV systolic dysfunction detected by CMR derived RV circumferential strain in patients with pectus excavatum

Abstract

Aims: To investigate the right ventricular (RV) strain in pectus excavatum (PE) patients using cardiac magnetic resonance tissue tracking (CMR TT).

Materials and methods: Fifty consecutive pectus excavatum patients, 10 to 32 years of age (mean age 15 ± 4 years), underwent routine cardiac magnetic resonance imaging (CMR) including standard measures of chest geometry and cardiac size and function. The control group consisted of 20 healthy patients with a mean age of 17 ± 5 years. RV longitudinal and circumferential strain magnitude was assessed by a dedicated RV tissue tracking software.

Results: Fifty patients with images of sufficient quality were included in the analysis. The mean right and left ventricular ejection fractions were 55 ± 5% and 59 ± 4%. The RV global longitudinal strain was -21.88 ± 4.63%. The RV circumferential strain at base, mid-cavity and apex were -13.66 ± 3.09%, -11.31 ± 2.79%, -20.73 ± 3.45%, respectively. There was no statistically significant decrease in right ventricular or left ventricular ejection fraction between patients and controls (p > 0.05 for each). There was no significant difference in RV global longitudinal strain between two groups (-21.88 ± 4.63 versus -21.99 ± 3.58; p = 0.93). However, there was significant decrease in mid-cavity circumferential strain magnitude in pectus patients compared with controls (-11.31 ± 2.79 versus -16.19 ± 2.86; p < 0.001). PE patients had a significantly higher basal circumferential strain (-13.66 ± 3.09% versus -9.76 ± 1.79; p < 0.001) as well as apical circumferential strain (-20.73 ± 3.45% versus -12.07 ± 3.38) than control group.

Conclusion: Mid-cavity circumferential strain but not longitudinal strain is reduced in pectus excavatum patients. Basal circumferential strain as well as apical circumferential strain were increased as compensatory mechanism for reduced mid-cavity circumferential strain. Further studies are needed to establish clinical significance of this finding.

Fig 1. Pectus index and CMR tissue tracking.

(A) The Haller Index (HI) is a ratio of the transverse diameter of the chest (line a) to the distance between the posterior aspect of the sternum and the anterior portion of the vertebra (line b): HI = a/b. The correction index (CI) measures the depression of the sternum relative to the anterior chest: CI = [(c-b)/c] x 100. (B) Right ventricular longitudinal strain. (C) and (D) Mid-cavity circumferential strain and peak value was recorded. The yellow colored contours show the tracking of the ventricle.

Fig 2. Relationship between pectus severity index and right ventricular ejection fraction, myocardial strain.