The effects of exercise training on cardiovascular responses to muscle metaboreflex activation in patients after coronary artery bypass grafting.

PURPOSE: To investigate cardiovascular responses to muscle metaboreflex activation in patients with coronary artery disease (CAD) after coronary artery bypass grafting (CABG) and assess the effects of exercise training on these responses.

METHODS

Cardiovascular responses of 11 post-CABG patients (60 ± 8 years) and 9 controls (CTL, 54 ± 6 years) were compared at rest, during a cold pressor test (CPT), and muscle metaboreflex activation using a post-exercise circulatory arrest (PECA) protocol. After baseline comparisons, the post-CABG group underwent 12 weeks of exercise training and was reevaluated.

RESULTS

During CPT, the post-CABG group exhibited greater increases in mean arterial pressure [MAP] (38.0 ± 9.0 vs. 18.7 ± 16.8 mmHg; P < 0.01) and systemic vascular resistance [SVR] (1053.0 ± 600.5 vs. 499.8 ± 481.0 mmHg.s/mL; P = 0.04) than CTL group. Muscle metaboreflex activation induced greater increases from rest in post-CABG than CTL for systolic blood pressure [SBP] (27.5 ± 17.3 vs. 14.2 ± 4.5 mmHg; P = 0.04), diastolic blood pressure [DBP] (10.1 ± 6.5 vs. 4.2 ± 1.8 mmHg; P = 0.02), MAP (27.5 ± 17.3 vs. 14.2 ± 4.5 mmHg; P = 0.04), SVR (149.7 ± 86.9 vs. 61.0 ± 47.4 mmHg.s/mL; P = 0.02), and blood lactate (0.48 ± 0.42 vs. - 0.18 ± 0.40 mmol/L; P < 0.01). After training, the post-CABG group reduced DBP response to CPT by 30% (P = 0.05). In addition, changes from rest induced by muscle metaboreflex in DBP, MAP, and blood lactate decreased by 28% (P = 0.05), 28% (P = 0.04), and 85% (P = 0.01), respectively.

CONCLUSION

Patients who underwent CABG exhibit exacerbated pressor responses to muscle metaboreflex activation, driven by increased SVR and blood lactate levels. This response potentially involves dysregulation in the brain stem or the efferent pathway of the muscle metaboreflex. Exercise training effectively attenuated these responses, highlighting its beneficial impact in CAD management.

TRIAL REGISTRATION: The study was registered on 01/12/2023 at EnsaiosClinicos.gov.br (RBR- 497 mxmm).