Longitudinal function of heart and its correlation with cardiac diseases

Background: Left ventricular pump function requires a complex interplay involving myocardial fibers orientated in the longitudinal, oblique and circumferential directions. Long axis dysfunction is an early marker for several pathological states. In fact, assessment of long axis function can provide independent prognostic information in patients with left ventricular dysfunction. Currently, longitudinal systolic function can be evaluated either by cardiac magnetic resonance or echocardiography, using two main techniques: mitral annular plane systolic excursion (MAPSE) and global longitudinal strain (GLS). The aims of these Cardiac Magnetic Resonance (CMR) studies were therefore: 1. To assess whether lateral MAPSE, as a surrogate for long axis function, is a predictor of major adverse cardiovascular events (MACE). 2. To evaluate the prognostic value of lateral MAPSE in a large multicenter sample of patients with reduced ejection fraction (EF). 3. To evaluate if lateral MAPSE may provide incremental prognostic information in patients with hypertension. 4. To assess whether CMR feature-tracking derived GLS may provide independent prognostic information in patients with cardiomyopathy in a single center and then in a multicenter study. Methods: Study 1. Patients referred at the Illinois University of Chicago for clinical CMR with both cine and late gate enhancement (LGE) imaging were prospectively enrolled. Patients were followed for the combined primary outcome of MACE: death, non-fatal myocardial infarction, hospitalization for heart failure or unstable angina, and late revascularization (>90 days after CMR). Study 2, 3, 4. Four geographically diverse universities in the United States participated in these observational, multicenter studies. We enrolled patients that had undergone clinical CMR at the involved Universities with both cine and late gate enhancement (LGE) imaging. Patients were followed for the primary outcome of all-cause mortality using the Social Security Death Index. 3 Lateral MAPSE was measured in 4 chamber view as the simple linear displacement between end-diastole and end-systole. Endocardial left ventricular contours were manually traced in all 3 long-axis cine views to derive GLS using the Qstrain feature tracking package. Results: Study 1. Patients with reduced lateral MAPSE experienced significantly higher incidence of MACE. After adjustment for established clinical risk factors which were univariate predictors, lateral MAPSE remained a significant independent predictor of MACE. Incorporation of lateral MAPSE into this risk model resulted in a net reclassification improvement (NRI). Study 2. In patients with lower tertiles of lateral MAPSE the risk of death increased significantly. After adjustment for risk factors which were univariate predictors, lateral MAPSE remained a significant independent predictor of death. Addition of lateral MAPSE to this model resulted in significant improvement in model discrimination. Study 3. In patients with hypertension lateral MAPSE is a significant independent predictor of mortality. By Kaplan-Meier-analysis, the risk-of-death was significantly higher in patients with lateral MAPSE<median (10mm). Lateral MAPSE was associated with an increased risk-of-death after adjustment for clinical and imaging risk factors. Addition of lateral MAPSE in this model resulted in significant-improvement in the C-statistic. Moreover, lateral MAPSE remained independently associated with death amongst the subgroup of patients with preserved EF as well as in those without a history of myocardial infarction. Study 4. The risk of death increased significantly with decreasing tertiles of GLS. After adjustment for risk factors, which were univariate predictors, GLS remained a significant independent predictor of death. Addition of GLS to this model resulted in significant improvement in the global chi-square and C statistic. Conclusions: Reduced long axis function assessed either with lateral MAPSE or GLS during routine cine-CMR is an independent predictor of MACE and all-cause mortality in patients with left ventricle (LV) disfunction and in hypertensives 4 patients incremental to common clinical and imaging risk factors including EF and LGE. Future studies are needed to explore the role of CMR derived lateral MAPSE and GLS in clinical decision making for these patients.