Abstract 3382: Discrimination of Mechanical Dyssynchrony from Regional Dysfunction due to Myocardial Infarction Using Novel Magnetic Resonance Imaging Strain Based Indices
Introduction: Regional dysfunction due to myocardial infarction can confound image based assessments of global dyssynchrony. As these akinetic and electrically inactive myocardial segments do not stand to benefit from cardiac resynchronization therapy (CRT), image based methods to isolate pure resynchronizable dyssynchrony may improve candidate selection. Accordingly, we present a novel MRI strain based method for discriminating between infarct-induced dyssynchrony (IID) and timing-delayed dyssynchrony (TDD).
Methods: Patients with dyssynchronous heart failure (N=4) and ischemic cardiomyopathy but no intraventricular conduction delay (N=4) and normal volunteers (N=4) underwent tagged MRI studies. Circumferential strains of each mid-ventricular slice were measured in the septum and lateral wall. Strain-time curves were then analyzed and two indices computed: the average of instantaneous strains at end-systole (ES) which is a metric of global function and the average of the peak strains which represents the maximally achievable global function assuming theoretically perfect segmental resynchronization.
Results: Pooled mean peak strain versus mean ES strain resulted in three distinct clusters for each of the three subject categories (Fig⇓). The averages for mean ES strains and mean peak strains, respectively, are: 10.95±3.79 and 15.01±2.69 for TDD, 4.87±1.84 and 9.25±1.91 for IID, and 18.51±3.77 and 19.06±3.34 for Normal.
Conclusions: Pure resynchronizable mechanical dyssynchrony can be differentiated from non-resynchronizable infarct related myocardial dysfunction. This capability may improve selection of patients likely to benefit from CRT.