Date Published: September 27, 2018
Publisher: Public Library of Science
Author(s): Aleksandra Trzebiatowska-Krzynska, Eva Swahn, Lars Wallby, Niels Erik Nielsen, Carl Johan Carlhäll, Lars Brudin, Jan E. Engvall, Otavio Rizzi Coelho-Filho.
Prior studies suggested that myocardial deformation is superior to conventional measures for assessing ventricular function. This study aimed to evaluate right ventricular (RV) myocardial deformation in response to increased afterload. Patients with the RV in the systemic position were compared with patients with the RV in the sub-pulmonic position with normal or only slightly elevated systolic right ventricular pressure. Correlations between global longitudinal strain (GLS), radial strain, atrioventricular plane displacement (AVPD), and exercise capacity were evaluated.
44 patients with congenital heart defect were enrolled in the study. The control group consisted of seven healthy volunteers. All patients underwent cardiovascular magnetic resonance (CMR) and cardiopulmonary exercise testing. We assessed biventricular myocardial function using CMR based feature tracking and compared the results to anatomic volumes.
Strain analysis and displacement measurements were feasible in all participants. RVGLS and RVAVPD were reduced in both study groups compared to the control group (p<0.001). Left ventricular (LV) radial strain was significantly lower in patients with a systemic RV than in those with a subpulmonic RV and lower than in controls (p<0.001). Both LVAVPD and RVAVPD were significantly depressed in patients compared to controls (p<0.05). RVAVPD was more depressed in patients with a high systolic RV pressure than in those with normal RV pressure (p<0.001). RVAVPD did not correlate with exercise capacity in either study group. Exercise capacity in both patient groups was depressed to levels reported in previous studies, and did not correlate with RVGLS. Both study groups had abnormal myocardial deformation and increased RV volumes. RVGLS in patients was lower than in controls, confirming the effect of increased afterload on myocardial performance.
Right ventricular (RV) function exerts an important influence on morbidity and mortality in patients with heart disease  . Research over the last few decades has revealed the importance of RV function for prognosis  , particularly in persons with CHD (Congenital Heart Disease) as those patients are often young and face repeated cardiac surgery. Assessment of RV function is challenging due to the crescentic shape of the RV and its central position in the thoracic cavity complicating visualization with ultrasound , especially in case of congenital cardiac malformations and after surgery   . Measurements of RV volume and its derivative ejection fraction (EF) are crucial  in research as well as in clinical decision making. As cardiovascular magnetic resonance (CMR) has the highest reproducibility for RV volume measurement it is considered to be the gold standard  . However, the assessment of EF is only one part of the functional evaluation and must be complemented with other parameters. Tissue characterization with CMR and the use of new functional measurements (myocardial deformation, strain) from either echocardiography or CMR help to understand mechanisms of ventricular adaptation and interaction. It is known from previous studies that in patients with congenital heart defect , both RV volume overload and RV pressure overload can lead to RV dilatation, decreased RVEF, and eventually RV failure  . Causes of RV pressure overload that can lead to untimely RV failure include atrially repaired transposition of the great arteries (TGA) and congenitally corrected transposition (CCTGA). Understanding the mechanisms of the RV response to various loading conditions and mechanisms of interventricular interaction    is important in global assessment, but the exact mechanisms of adaptation and how adaptation affects different aspects of RV function remains largely unknown. Myocardial strain has been suggested to provide additional information about ventricular function,  however very few studies have investigated the specific adaptive mechanisms in conditions of CHD.
Various aspects of RV and LV strain differ between the disease groups. We observed differences of radial and longitudinal strain  when comparing each study group with the control group as well as when comparing the study groups to each other.
This study demonstrates that differences in RV and LV longitudinal strain and AVPD, correlate with the degree of pressure load. This observation can be related, in part, to ventricular adaptation to altered loading conditions. These findings are at least partly consistent with those of previous studies describing adaptation processes in terms of increases in circumferential and decreases in the longitudinal deformation in the systemic RV .