| Outcome Measures: |
Primary: Change in LV Mass, Variability seen in change in LV mass with ISMN administration measured with steady-state free precession cardiac MRI, outcomes reflect the change, in grams, Measured at Baseline Visit and 24 Week Visit | Secondary: Changes in Diffuse Myocardial Fibrosis, Myocardial ECV was assessed using a modified Look-Locker inversion recovery sequence to assess T1 times before and following the IV administration of gadolinium contrast in a mid-ventricular short-axis slice. Parameters for modified Look-Locker inversion recovery were: field of view=340mm2; matrix size=144×192; slice thickness=6mm; repetition time=2.4ms; echo time=1.18ms; flip angle=30 degrees, bandwidth=1000 Hz/pixel, integrated parallel acquisition techniques=2. Myocardial T1measurements were performed before and at several time points (5, 10, 15, and 20-40 min) post-gadolinium administration. Modified Look-Locker inversion recovery was performed with a 5-3-3 schema with (2 inversions, 5 echo times after inversion 1, 3 T1 recovery heartbeats, and 3 echo times after inversion 2). All T1 measurements were used to compute lambda (the myocardium-blood partition coefficient) as the slope of the myocardial 1/T1 over the blood 1/T1 change, by linear regression., Measured at Baseline Visit and 24 Week Visit|Changes in Myocardial Systolic and Diastolic Function, Variability in changes in myocardial function with ISMN administration, assessed via systolic longitudinal strain (measured with tissue tracking MRI) with adequate data for tissue tracking. Strain is the shortening during contraction, expressed as a promotion of the end-diastolic myocardial length. Shortening is indicated by a negative value. Strain is a unit-less metric and is thus expressed in %. A change with negative sign indicates more pronounced shortening of baseline compared to 6 months; a change with positive sign indicates less pronounced shortening during contraction., Measured at Baseline Visit and 24 visits|Pulse Wave Reflection Magnitude, Measured by arterial tonometry and echocardiography. The data reflects estimated changes in each group utilizing all available measurements, collected at all timepoints (baseline visit and weeks 1, 2, 3, 12, and 24 visits). Numbers are estimated changes in each group utilizing available measurements. The change represents the absolute change in the ratio of backward to forward wave amplitudes, multiplied by 100., Measured between Baseline Visit-Week 24|Aerobic Capacity, Variability in changes in aerobic capacity (peak oxygen consumption during maximal supine bicycle exercise test), Change from Baseline at Week 24 reported
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