Abstract 18804: Relationship of Left Ventricular Circumferential Strain with Preload and Afterload Using Feature-Tracking MRI

Abstract

Background: Myocardial Strain is a sensitive measure of left ventricular (LV) global and regional myocardial deformation. Its association with preload and afterload is yet to be elucidated. We assessed circumferential strain using Feature-tracking (FT) MRI and investigated the relationship of strain with preload and afterload using hemodynamics assessed during left heart catheterization.

Methods: Forty nine patients undergoing clinical cardiac catheterization were prospectively recruited for same day research cardiac MRI. Circumferential strain was assessed by analyzing endocardial deformation of the cine images in mid LV short axis planes using FT-MRI (Diogenes TomTec Imaging Systems). LV end diastolic pressure (LVEDP) and LV end systolic pressure (LVESP) were assessed during cardiac catheterization. Meridional wall stress was calculated using the formula: σ_m=PR/2h (l+h/2R) where p was the pressure, R the radius and h the average myocardial wall thickness. LV preload and afterload were defined as the meridional wall stress at end diastole and systole.

Results: The cohort mean age was 60 ± 13 years, 32 (65%) male. The average circumferential strain was -22.5±7.9%, LV ejection fraction (LVEF) 50 ± 14%, LVEDP 16±7 mmHg and LVESP 135±28 mmHg. In a univariate analysis, circumferential strain was most strongly associated with LVEF (r=-0.91, p < 0.001) followed by LV end systolic volume (r= 0.864, p< 0.001), LV end diastolic volume (r= 0.790, p < 0.001) and LV mass (r=0.572, p<0.001). Of LV hemodynamic properties, strain was associated with LVEDP (r=0.517, p< 0.001) but not with LVESP (r=-0.110, p = 0.450). However, the association became much stronger when hemodynamics were expressed as preload (r=0.681, p<0.001) and afterload (r= 0.820, p< 0.001). In a multivariate linear regression model adjusting for LVEF, LV mass, LVESP, LVEDP, preload and afterload , circumferential strain was only associated with LVEF (p <0.001) and afterload (p=0.009).

Conclusion: Circumferential strain assessed by FT- MRI is a sensitive measure of left ventricular systolic function. Preload and afterload are more important than intraventricular pressure alone in the relationship of strain to hemodynamics. However, afterload is likely the most important hemodynanic variable.