Abstract 12155: Analysis of Stress-Strain Relationships Using Cardiac MRI
Background: The stress-strain relationship is central to the understanding of myocardial mechanical performance. We compared noninvasive myocardial wall stress assessed using noninvasive hemodynamics acquired during cardiac MRI (CMR) with wall stress calculated using invasive hemodynamics and assessed stress-strain relationships.
Methods: Forty two patients undergoing clinically indicated cardiac catheterization were prospectively recruited for same day research CMR. Invasive left ventricular end systolic pressure (LVESP) and end diastolic pressure (LVEDP) were obtained during catheterization. Endocardial systolic circumferential strain and wall stress were assessed in the mid-ventricular short-axis plane. CMR feature tracking software was used for circumferential strain analysis. Noninvasive circumferential strain was calculated using cuff systolic blood pressure (SBP) during CMR and LVEDP estimation from left atrial gadolinium transit time during first pass perfusion.
Results: Mean age was 61 years and 57% were males. Cuff SBP and LVESP were similar, 122±16 mmHg vs 129±22 mmHg (paired t-test p=0.010). LVEDP by noninvasive estimation (14±6 mmHg) did not differ significantly from the invasive measure (13 ± 6 mmHg) (paired t-test p=0.207). Noninvasive end systolic wall stress was comparable to the invasive measure (195±124 vs 185±122 dynes/cm2 x 103, paired t-test p=0.049) and at end diastole (24±13 vs 27±11 dynes/cm2 x 103, paired t-test p=0.122). Reduced circumferential strain correlated strongly with increased systolic wall stress (r= 0.890, p≤ 0.001) and increased diastolic wall stress (r=0.580, p≤ 0.001). In multivariate regression analyses adjusting for LV ejection fraction (EF), LV mass, LVEDP, diastolic BP, wall stress at end systole and at end diastole, reduced LVEF and increased wall stress at end systole were the significant correlates of reduced circumferential strain demonstrating a strong stress-strain relationship.
Conclusion: Circumferential strain assessed by CMR feature tracking correlated strongly with noninvasive circumferential wall stress demonstrating strong load dependence of myocardial strain. CMR is a promising modality in assessing stress-strain relationships noninvasively.
- © 2013 by American Heart Association, Inc.