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Background: Chronic postsurgical pain (CPSP) worsens patients' mortality, morbidity, and quality of life. Cardiopulmonary bypass is mandatory for cardiac surgery, but it induces intense inflammation. The presence of inflammation is a crucial part of pain sensitization. An extreme inflammatory response due to cardiopulmonary bypass might cause a high prevalence of CPSP after cardiac surgery. We hypothesized that the prevalence and severity of CPSP are higher in patients after on-pump coronary artery bypass graft (CABG) surgery than in those after off-pump CABG surgery. Methods: This prospective, observational study was performed on a cohort from a randomized trial (on-pump CABG: 81 patients, off-pump CABG: 86 patients). A questionnaire about the severity of surgical wound pain that evaluated pain with the numerical rating scale (NRS) was filled out by the patients. NRS responses for current pain, peak pain in the last 4 weeks, and average pain in the last 4 weeks were evaluated. The main outcomes were the severity of CPSP as evaluated using the NRS and the prevalence of CPSP. CPSP was defined as pain with an NRS score > 0. Differences in severity between groups were analyzed using multivariate ordinal logistic regression models adjusted for age and sex, and differences in prevalence between groups were analyzed using multivariate logistic regression models adjusted for age and sex. Results: The questionnaire return rate was 77.0%. During a median follow-up of 17 years, 26 patients complained of CPSP (on-pump CABG: 20 patients, off-pump CABG: 6 patients). Ordinal logistic regression showed that the NRS response for current pain (odds ratio [OR] 2.34; 95% CI 1.12–4.92; P = 0.024) and the NRS response for peak pain in the last 4 weeks (OR 2.71; 95% CI 1.35–5.42; P = 0.005) were significantly higher in patients who underwent on-pump CABG surgery than in those who underwent off-pump CABG. Logistic regression showed that on-pump CABG surgery was an independent predictor of CPSP (OR 2.59; 95% CI 1.06–6.31; P = 0.036). Conclusions: The prevalence and severity of CPSP are higher in patients with on-pump CABG surgery than in those with off-pump CABG surgery. [ABSTRACT FROM AUTHOR]