The Cardiac MR Images and Causes of Paradoxical Septal Motion

vexity that is determined by a left-to-right positive transseptal pressure gradient, and this shape is maintained during the cardiac cycle (1, 2). Changes in the position and geometry of the ventricular septum occur when there is an acute or chronic imbalance between the left and right ventricular loading conditions, such as a postoperative state of tetralogy of Fallot, an atrial septal defect, pulmonary thromboembolism, mitral stenosis, constrictive pericarditis or left bundle branch block (2-4). The phenomenon that alters the function of one ventricular function by changes in the filling of the other ventricle is called interventricular dependence or ventricular coupling (4). Delayed left ventricular filling leads to an abnormal trans-septal pressure gradient and this accentuates early diastolic septal movement, which gradually returns rightward when the left ventricular filling continues. Further, the anterior movement of the ventricular septum in systole can be detected during the cardiac cycle after coronary artery bypass grafting, although the cause of this is unclear (5). Doppler echocardiography is currently the first choice of image modalities for assessing septal motion. The advent of magnetic resonance imaging (MRI) with stronger and faster gradient systems has recently enabled evaluating the septal motion and the real-time dynamic contraction of the heart chambers, and this potentially gives cardiac MRI the same ability as that of echocardiography for evaluatJ Korean Soc Radiol 2010;62:427-434