Quantitative two-dimensional echocardiographic analysis of motion and thickening of the interventricular septum after cardiac surgery

Abstract

Septal and lateral wall motion and septal thickening were evaluated with quantitative two-dimensional echocardiography in 20 patients who underwent cardiac surgery without complications. Postoperative mean ejection fraction (48 +/- 10%) measured by radionuclide ventriculography was unchanged from the preoperative value (45 +/- 8%). Mean postoperative systolic thickening of the septum (33 +/- 15%) was also unchanged from the preoperative value (26 +/- 10%). However, septal endocardial motion as measured by an external frame-of-reference (fixed-axis) system fell from a 22 +/- 10% mean percent shortening (MPS) of septal radii to a postoperative value of -8 +/- 15% (p less than .001). Fixed-axis analysis also led to an increase in MPS of lateral radii: preoperative 16 +/- 5%; postoperative 28 +/- 9% (p less than .001). With an internal frame-of-reference (floating-axis) system, which compensates for the effects of translation and rotation on wall motion, postoperative MPS of septal radii (22 +/- 10%) was unchanged from preoperative MPS (25 +/- 8%; p = NS). Similarly, MPS of lateral wall radii was unchanged (preoperative, 15 +/- 5%; postoperative, 12 +/- 5%; p = NS). Thus systolic translation of the ventricle accounts for abnormal postoperative septal motion seen in a fixed-axis system and can be corrected by a floating-axis system. These data have important implications for the noninvasive evaluation of regional wall motion after cardiac surgery. Systems using a fixed external frame of reference such as radionuclide ventriculography are prone to systematic error. A combination of systolic thickening analysis by two-dimensional echocardiography and analysis of endocardial motion by the floating-axis system is a more appropriate method for evaluating the effects of cardiac surgery on regional left ventricular function.