The Impact of Infarct Location and Extent on LV Motion Patterns : Implications for Dyssynchrony Assessment

ObjectivesThis study sought to investigate the influence of scar extent and location on the motion pattern of the left ventricle (LV) and its interaction with LV conduction delays.BackgroundDifferent echocardiographic parameters have been proposed to identify responders to cardiac resynchronization therapy based on the detection of LV mechanical dyssynchrony. However, the impact of infarct scar on the diagnostic performance of these parameters remains unknown.MethodsWe included 11 healthy volunteers and 122 patients with normal and severely reduced function, wide and narrow QRS, as well as with and without infarct scar. Location and extent of infarct scar was defined by contrast-enhanced cardiac magnetic resonance. Influence of infarct scar on the motion pattern of the LV was examined by measuring direction and amplitude of apical rocking. The influence of scar on different echocardiographic dyssynchrony parameters was investigated.ResultsScar in the absence of conduction delay caused most apical rocking in the presence of 3 to 4 infarct segments. Pure apical infarction caused no rocking. In wide QRS patients without infarct scar, apical rocking was mainly dominated by the conduction delay, whereas in wide QRS patients with ischemic cardiomyopathy, this pattern was modulated by the scar. Apical rocking was inversely related to scar extent (r = −0.54, p < 0.05). Apical rocking was better associated with cardiac resynchronization therapy response than conventional dyssynchrony measurements.ConclusionsLV motion patterns are mainly dominated by conduction delays, but they are also modulated by infarct scar. Higher scar burden resulted in less pronounced apical rocking. Apical rocking is more strongly associated with cardiac resynchronization therapy response than with conventional echocardiographic parameters and may therefore be used as a screening parameter.