Hypobaric hypoxia exerts higher sympathetic activation in patients after myocardial infarction than in normal volunteers
Laederach-Hofmann, K.1, Messerli-Bürgy, N.2, and Meyer, K.3
1Autonomes Labor, Departement Klinische Forschung, Universität Bern; 2Psychologisches Institut, Universität Bern; 3Gesundheitsobservatorium Neuchâtel
During a high altitude exposure of 3564m (Jungfraujoch) 10 patients after myocardial infarction (MI) and 10 normal volunteers (NV) were tested by non-invasive assessment of cardiovascular and autonomic functions (TFM-System) during rest and mental stress (Stroop). Values were compared with normal altitude at 544m (Bern).
Compared to NV, MI patients demonstrated lower resting stroke volume (p<0.05). High altitude exposure was accompanied by unchanged low-frequency(LF) band and total power values in MI compared to NV: MI patients demonstrated higher LF/HF values whereas there was a decrease in values in patients with NV (p<0.01). The groups did not differ in BRS.
Conclusions: Although all MI patients were either on beta blockade or A-II inhibition medication, they exhibited higher sympathetic activity during exposure to high altitude compared to NV and were found to have a lower capacity to adapt to mental stress. This might indicate a higher pro-arrhythmogenic risk for MI at 3564m.