Autonomic nervous system (ANS) dysfunction has emerged as a central feature of post-infectious syndromes, including post-COVID syndrome (PCS), chronic fatigue syndrome (CFS), and late-stage Lyme disease. This cross-sectional study included 1036 patients evaluated in the Neurocardiological Laboratory of the Institute for Cardiovascular Diseases “Dedinje,” divided into four groups: PCS, CFS after COVID-19, CFS of insidious onset, and Lyme disease. All patients underwent head-up tilt testing (HUTT), and serological testing was performed in accredited institutions. The Lyme disease group demonstrated the highest prevalence of positive HUTT responses and a significantly greater frequency of orthostatic hypotension and syncope. Approximately 50–65% of patients in the PCS and Lyme groups were positive for IgM antibodies against at least one microorganism, with more than 10% showing positivity for three or more pathogens. Logistic regression analysis revealed that, beyond classical hemodynamic parameters, antibody status served as a significant predictor of HUTT outcomes, with specific associations identified for HSV-1, HHV-6, Coxiella burnetii, Toxoplasma gondii, and Borrelia spp. Multinomial regression further indicated that negative IgG antibodies, particularly to HSV-1 and VZV, predicted Lyme disease group membership. These findings support the hypothesis that ANS dysfunction in post-infectious syndromes may be driven by persistent or prior infections, highlighting the need for integrative diagnostic approaches.

Background/Objectives: Coronary artery disease (CAD) is highly prevalent in patients undergoing vascular surgery and is a major determinant of postoperative morbidity and mortality. Preoperative anemia is a well-recognized risk factor for adverse outcomes, including major adverse cardiac events (MACEs), but its independent impact in patients with CAD undergoing abdominal aortic aneurysm (AAA) repair remains unclear. Methods: We conducted a retrospective cohort study of 410 consecutive patients undergoing open AAA repair at a tertiary vascular center between 2023 and 2025. Preoperative anemia was defined as hemoglobin < 130 g/L and significant CAD as ≥70% luminal narrowing for non-left main disease or ≥50% for left main disease. The primary outcome was MACE (cardiovascular death, myocardial infarction, or stroke) during hospitalization. Baseline covariates included age, sex, diabetes mellitus (DM), chronic kidney disease (CKD), congestive heart failure (CHF), peripheral artery disease (PAD), and other relevant comorbidities. Multivariable logistic regression models were used to evaluate associations of anemia, CAD, and their interaction with MACE. Additionally, a composite risk group was created to examine MACE rates across mutually exclusive subgroups. Results: Among 410 patients, 314 (76.6%) had CAD and 116 (28.3%) had preoperative anemia. Overall, 67 patients (16.3%) experienced MACE. In the reduced model including only anemia and CAD, anemia remained a strong independent predictor of a MACE (OR 4.46, 95% CI 2.57–7.72, p < 0.001), and CAD was also independently associated (OR 2.20, 95% CI 1.00–4.72, p = 0.044). In the full multivariable model adjusting for DM, CHF, CKD, PAD, and age, anemia was the strongest predictor (OR 4.53, 95% CI 2.49–8.26, p < 0.001), while CAD showed a borderline association (OR 2.07, 95% CI 0.94–4.57, p = 0.071). Interaction analysis indicated no statistically significant modification in risk by the combination of anemia and CAD. The composite risk group variable was omitted due to collinearity with its components. Conclusions: Preoperative anemia, particularly in patients with CAD, is a significant and independent predictor of major adverse cardiac events following open AAA repair. These findings support the importance of early identification and correction of anemia before surgery to improve perioperative cardiac outcomes in this high-risk population.