Cardiac Magnetic Resonance Imaging with Myocardial Strain Assessment Correlates with Cardiopulmonary Exercise Testing in Patients with Pectus Excavatum.

Objectives

To evaluate correlations between cardiac magnetic resonance imaging (cMRI) at rest including strain imaging and variables derived from quantitative cardiopulmonary exercise testing using a treadmill in patients with pectus excavatum.

Methods

We retrospectively correlated the results of cMRI and cardiopulmonary exercise testing in 17 patients with pectus excavatum, in whom both examinations were performed during their pre-operative clinical evaluation. In addition to cardiac volumetry, we assessed the strain rates of both ventricles using a feature-tracking algorithm of a piece of commercially available post-processing software.

Results

Right ventricular (RV) ejection fraction correlated negatively with heart rate at anaerobic threshold (rho = -0.543, p = 0.024). A positive correlation between radial strain rate at the RV base and percentage of predicted maximum heart rate (rho = 0.72, p = 0.001) was shown, with equivalent results for circumferential strain rate (rho = -0.64, p = 0.005). Radial strain rate at the RV base correlated in a strongly negative way with maximum oxygen uptake (rho = -0.8, p < 0.001), with a correspondingly positive correlation for circumferential strain rate (rho = 0.73, p = 0.001).

Conclusions

Quantitative parameters derived from cMRI at rest, especially those acquired at the most severely compressed RV base, correlated with cardiopulmonary exercise testing variables. The compression of the RV base by the sternum might be partially compensated by an increased strain rate to induce higher heart frequencies during exercise. However, high strain rates were associated with a higher disease severity and a lower maximum oxygen uptake, indicating a limitation of this compensation mechanism.