['The optimal strategy for spinal cord protection during thoracoabdominal aortic aneurysm (TAAA) repair remains unclear. We evaluated the protective effect of left heart bypass (LHB) during repair of extensive TAAAs.', 'During a 12-year period, 710 patients had repair of extent I or II TAAAs. Left heart bypass was used in 312 (43.9%) patients. This group was retrospectively compared with 398 (56.1%) patients who had operations without LHB.', 'The overall 30-day survival rate was 94.8% (673 patients). In 42 patients, (6.0%) paraplegia or paraparesis developed. In patients with extent I TAAAs, paraplegia and paraparesis rates in LHB (6 of 123, 4.9%) and non-LHB (9 of 246, 3.7%) groups were similar (p = 0.576) despite longer aortic clamp times in the former group. In patients with extent II TAAAs, the LHB group had a lower incidence of paraplegia or paraparesis (9 of 189, 4.8%) compared with the non-LHB group (18 of 137, 13.1%; p = 0.007).'] Does left heart bypass reduce paraplegia rates after thoracoabdominal aortic aneurysm repair?