Hipotensão pós-exercício em pessoas com histórico de acidente vascular cerebral: uma análise metodológica e fisiológica do fenômeno

Abstract

This thesis is composed by two studies addressing the methodological and physiological aspects of post-exercise hypotension (PEH) in people after stroke. Methodological study aims: (i) to assess the occurrence and reproducibility of PEH using different approaches [A_1 =post‐exercise-pre‐exercise; A_2=post‐exercise-post‐CTL; A_3=(post‐exercise-pre‐exercise)-(post‐CTL-pre‐CTL)] after two bouts of mixed circuit training (MCT); (ii) to assess the proportion using different cut-off values for BP variation (4 mmHg vs. minimal detectable difference, MDD). Physiological study aims: (i) to investigate if a single bout of MCT would promote PEH in people after stroke; (ii) to assess possible mechanisms associated to PEH. Seven participants (58 ± 12 yr) performed two bouts of MCT and a non-exercise control session (CTL). Systolic (SBP) and diastolic (DBP) blood pressure (BP) and mean arterial pressure (MAP), heart rate (HR), cardiac output (Q), systemic vascular resistance (SVR), baroreflex sensitivity (BRS) and heart rate variability (HRV) were assessed 10 min before and 40 min after (at laboratory) the experimental sessions. BP and HRV were assessed during the following 24h (ambulatory). Results from the methodological study: The two-way random intraclass correlation coefficient for single measurements (ICC 2,1) ranges for SBP were: A1: 0.580-0.829, A2: 0.937-0.994, and A3: 0.278-0.774; for DBP: A1: 0.497-0.916, A2: 0.133-0.969, and A3: 0.175-0.930. The proportion of PEH responders was greater (SBP: ~14-57%, DBP: ~42-57%; p < 0.05) when using 4mmHg vs. MDD as cut-off values in A1 and A2, but not in A3. Results from the physiological study: SBP (∆‐22%), DBP (∆‐28%), SVR (∆‐43%), BRS (∆‐63%), and parasympathetic activity (HF; high‐frequency component: ∆‐63%) were reduced during 40 min post‐MCT vs. CTL (p < 0.05), while Q (∆35%), sympathetic activity (LF; low‐frequency component: ∆139%) and sympathovagal balance (LF:HF ratio: ∆145%) were higher (p < 0.001). In the first 10 h of ambulatory assessment, SBP (∆‐7%), MAP (∆‐6%), and HF (∆‐26%) remained lowered, and LF (∆11%) and LF:HF ratio (∆13%) remained elevated post‐MCT vs. CTL (p < 0.05). Conclusions: A2 was more reliable than A1 or A3 to determine PEH in people after stroke. MDD was a more conservative approach than the 4-mmHg cut-off value to identify PEH responders. A single bout of MCT elicited prolonged PEH in chronic hemiparetic stroke patients. This occurred concurrently with increased sympathovagal balance and lowered SVR and BRS.