Value of gated SPECT in the analysis of regional wall motion of the interventricular septum after coronary artery bypass grafting

Purpose: The aim of this study was the evaluation of septal wall motion, perfusion and wall thickening after CABG in two groups of consecutive patients, one with grafted left anterior coronary artery and no history of myocardial infarction, and the other with previous anteroseptal myocardial infarction and impaired septal motion before surgery. The issue addressed was the ability of gated SPECT to differentiate between true paradoxical septal motion, characterised by paradoxical wall motion, depressed ejection fraction (EF), poor viability and compromised wall thickening, and pseudo-paradoxical motion, characterised by abnormal wall motion and regional EF but preserved perfusion and wall thickening. Methods: One hundred and thirty-two patients with previous anterior myocardial infarction, 82 patients with left anterior descending coronary disease and no history of myocardial infarction and 27 normal subjects underwent rest gated SPECT after Tc-99m-sestamibi injection, according to the standard QGS protocol. Quantitative regional EF, regional perfusion, regional wall motion and regional wall thickening were determined using a 20-segment model. Results: Despite the presence of similar regional wall motion impairment in patients with and patients without septal infarction, in terms of regional EF (2.5% +/-3% vs 1.9% +/-4.9% p=NS) and inward septal motion (3 +/-4.9 mm vs 2.3 +/-6.1 mm p=NS), significant differences were observed in both perfusion (74.7%+/-6.2% vs 63.3%+/-13%, p>0.0001) and regional wall thickening (17.2%+/-7.4% vs 12.6%+/-7.2%, p>0.0001). Conclusion: Gated SPECT with perfusion tracers can reliably differentiate pseudo-paradoxical from true paradoxical septal motion in patients with previous CABG, and it may be the method of choice for evaluating left ventricular performance in this patient population.