BackgroundThe pathophysiology responsible for the significant outcome disparities between men and women with cardiac disease is largely unknown. Further investigation into basic cardiac physiological differences between the sexes is needed. This study utilized magnetic resonance imaging (MRI)-based multiparametric strain analysis to search for sex-based differences in regional myocardial contractile function.MethodsEnd-systolic strain (circumferential, longitudinal, and radial) was interpolated from MRI-based radiofrequency tissue tagging grid point displacements in each of 60 normal adult volunteers (32 females).ResultsThe average global left ventricular (LV) strain among normal female volunteers (n = 32) was significantly larger in absolute value (functionally better) than in normal male volunteers (n = 28) in both the circumferential direction (Male/Female = -0.19 ± 0.02 vs. -0.21 ± 0.02; p = 0.025) and longitudinal direction (Male/Female = -0.14 ± 0.03 vs. -0.16 ± 0.02; p = 0.007).ConclusionsThe finding of significantly larger circumferential and longitudinal LV strain among normal female volunteers suggests that baseline contractile differences between the sexes may contribute to the well-recognized divergence in cardiovascular disease outcomes. Further work is needed in order to determine the pathologic changes that occur in LV strain between women and men with the onset of cardiovascular disease.

Background Global systolic strain has been described previously in patients with chronic aortic insufficiency (AI). This study explored regional differences in contractile injury. Methods Tagged magnetic resonance images of the left ventricle (LV) were acquired and analyzed to calculate systolic strain in 42 patients with chronic AI. Multiparametric systolic strain analysis was applied to relate cardiac function in AI patients to a normal strain database (N = 60). AI patients were classified as having normal or poor function based on their results. A two-way repeated-measures analysis of variance was applied to analyze regional differences in injury. Results The mean and standard deviation of raw strain values (circumferential strain, longitudinal strain, and minimum principal strain angle) are presented over the entire LV in our normal strain database. Of the 42 patients with AI, 15 could be defined as having poor function by multiparametric systolic strain analysis. In AI patients with poor function, statistical analysis showed significant differences in injury between standard LV regions (F369,44.33 = 3.47, p = 0.017) and levels (F1.49,17.88 = 4.41, p = 0.037) of the LV, whereas no significant differences were seen in the group with normal cardiac function. Conclusions Patients with poor function, as defined by multiparametric systolic strain z scores, exhibit a consistent, heterogeneous pattern of contractile injury in which the septum and posterior regions at the base are most injured.

Objectives Clinical guidelines for asymptomatic patients with chronic MR utilize ejection fraction (EF) to trigger surgical referral. We hypothesize that 1) EF is not sensitive enough to detect the earliest contractile injury in chronic MR and 2) that the injury associated with chronic MR is not global but heterogeneous, occurring regionally and predictably, prior to the onset of global left ventricular (LV) dysfunction. Methods Fifteen patients with chronic MR and normal LV EF by echocardiography underwent cardiac MRI with tissue tagging. Point-specific comparisons (at 15,300 LV grid points) of multiple strain parameters to a normal human strain database allowed normalization of patient-specific regional contractile function. Data were mapped over patient-specific 3D geometry, then averaged across six LV regions. Results Global LV longitudinal and circumferential myocardial strains were normal for all 15 MR patients when compared to normal controls (p>0.05). Despite preserved global function, the anteroseptum and posteroseptum demonstrated significantly worse contractile function when compared to other regions of the LV (p=0.003 and p=0.035, respectively). Hyper-contractile regions (lateral walls) appeared to compensate (p=0.002) for the reduced septal contractile function thereby masking injury detection by global indices. Conclusion The earliest contractile injury seen in MR patients is heterogeneous, and consistently distributed along the LV septum. Compensatory responses include hypercontractility of other regions. These data suggest that rather than relying upon global LV contractile metrics, which do not detect early injury, patients may be better served by undergoing directed surveillance of “sentinel” LV regions (LV septum) with high-resolution metrics of regional contractile function.

Background Guidelines for referral of chronic aortic insufficiency (AI) patients for aortic valve replacement (AVR) suggest that surgery can be delayed until symptoms or reduction in left ventricular (LV) contractile function occur. The frequent occurrence of reduced LV contractile function after AVR for chronic AI suggests that new contractile metrics for surgical referral are needed. Methods In 16 chronic AI patients, cardiac MRI tagged images were analyzed before and 21.5 ± 13.8 months after AVR to calculate LV systolic strain. Average measurements of three strain parameters were obtained for each of 72 LV regions, normalized using a normal human strain database (n=63), and combined into a composite index (multi-parametric strain z score [MSZ]) representing standard deviation from the normal regional average. Results Preoperative global MSZ (72-region average) correlated with post-AVR global MSZ (R2 = .825, p < .001). Preoperative global MSZ also predicts improvement of impaired regions (N=271 regions from 14 AI patients, R2 = .392, p < .001). Preoperative MRI-based left ventricular ejection fraction (LVEF) is also predictive (r = .410, p < .001). Although global preoperative MSZ had a significantly higher correlation than preoperative LVEF with improvement of injured regions (p < .001), both measures convey the same phenomenon. Conclusions Global preoperative MRI-based multi-parametric strain predicts global strain postoperatively, as well as improvement of regions (n=72/LV) with impaired contractile function. Global contractile function is an important correlate with improvement in regionally impaired contractile function, perhaps reflecting total AI volume-overload burden (severity/duration of AI).

Introduction: Left ventricular (LV) regional contractile information is currently limited to subjective interpretation of low-resolution echocardiography. In order to establish a more specific and standardized form of imaging, this study compared strain patterns in normal patients to patients with coronary artery disease (CAD) using high-resolution contractile data from cardiac MRI. Methods: Sixty normal test subjects underwent cardiac MRI with multiple 3D strain parameters calculated from tissue tag-plane displacement data. 15,300 LV grid points contributed to a normal human strain database. Sixty patients with known CAD underwent cardiac MRI. Normalized z-scores for 3 strain parameters at each of the LV grid-points were calculated by comparing raw strain values to the normal database. The z-scores at each point were then averaged to generate 15,300 normalized strain z-scores. Clinical evidence for prior ischemic events was sought in each patient’s medical record. Results: Multi-parametric strain information was successfully obtained in all 60 CAD patients with post-processing display of “quantified” regional ischemic injury over patient-specific LV geometry. We displayed “normalized” micro-regional contractile function by intuitive z-score color-coding of regions (<1 standard deviation=blue; 1-2=yellow; >2=red) over patient-specific 3D LV geometry (Figure). Clinical evidence for prior ischemic events obtained from echo, viability studies, ECG, and left heart catherization correlated well with regional injury patterns. Conclusions: The quantitative “normalization” of raw patient-specific values by z-score calculation from a normal human strain database can effectively create vivid displays of prior ischemic events. These high-resolution images provide detailed contractile information that may shape a new paradigm in preoperative surgical evaluation prior to revascularization.