Parasympathetic tone and its adaptation to aerobic training (Fitwalking®) in HIV patients on anti-retroviral therapy

Recent evidences showed that in HIV patients Highly Active Antiretroviral Therapy (HAART) and HIV per se may affect parasympathetic tone; this may increase the cardiovascular risk and contribute to HIV associated lipodystrophy. Such impairment may be reversed by a regular physical activity, which is known to increase vagal tone. PURPOSE: To evaluate vagal tone and its change after 3 months of aerobic training in HIV patients on HAART. METHODS: 12 non-hypertensive and non-smoker patients (F/M 2/10; 47±5 yrs; 71±14 kg) with HIV infection (H) on HAART were enrolled. A group of 12 control (C) subjects (F/M 3/9; 48±12 yrs; 76±13 kg), matched for gender, age and anthropometric features, was enrolled for baseline comparisons. Heart rate variability (HRV) indexes of parasympathetic tone in time (RMSSD, pNN50) and frequency (High Frequency [HF] in absolute and normalized units [nu]) domains, and a HRV index of sympathovagal balance (LF/HF ratio) were calculated in basal condition in H and C subjects, both in supine and standing position for 5 min each, by a HR monitor. The H group was then trained by walking at 60-70% of maximal HR 3 times/week for 12 weeks, and the HRV measures were repeated thereafter. A 6-min walking test (6MWT) was executed before and after the training. RESULTS: In basal condition, despite similar values in supine position between H and C subjects, HIV patients showed a lower parasympathetic tone during standing, which was significant in the linear indexes (RMSSD: H 16.7±5.1 vs C 25.3±10.5 ms [p<0.05]; pNN50: H 1.4±1.3 vs C 5.4±5.3% [p<0.05]; HF: H 180±207 vs C 196±139 ms2; HFnu: H 21.6±23.5 vs C 27.0±16.2), and a higher sympathetic activation (LF/HF: H 9.2±7.0 vs C 4.1±2.7 [p=0.04]) compared to C subjects. Fitwalking® training significantly improved the distance covered by 6MWT (from 667±50 to 802±160 m, p=0.01) and the physical work done (from 451±96 to 538±132 J, p=0.01). However, standing values of HRV indexes did not significantly change after training in H patients (RMSSD 15.2±6.6 ms, pNN50 1.1±1.7%, HF 100±93 ms2, HFnu 11.5±6.7, LF/HF 9.7±7.5; p=ns vs pre-training for all comparisons). CONCLUSIONS: 12-weeks aerobic training improved cardiovascular fitness in HIV patients, but did not affect the heart parasympathetic control, which remained reduced compared to healthy subjects.