Electrocardiographic Changes in the High Altitude Environment

Objective: This thesis sets out to identify the rate, rhythm and morphological changes that occur in the ECG’s of healthy lowland residents who are exposed to hypoxic conditions at sea level and high altitude.
Methods: Three separate ECG studies were performed on healthy lowland residents. The first was conducted on 16 members of the Caudwell Xtreme Everest Expedition (CXE) during a stay at Mt Everest Base Camp (EBC) (5300m). The second was conducted on 37 members of the Team Everest Expedition (TE) during an ascent to EBC. Finally, a group of
10 participants were studied whilst breathing a range of hypoxic gas mixtures (12-18% oxygen) at sea level (AHS).
Results: Rate - CXE - The median resting heart rate increased following ascent to Mt Everest Base Camp (EBC) (5300m) (P<0.05). TE - The mean resting heart rate of male and female participants increased following ascent to Namche Bazaar (3500m) (P<0.05). Rhythm – CXE, TE and AHS: No significant difference was observed in the incidence of atrial or
ventricular ectopics following ascent to Mt Everest Base Camp (5300m). Morphology – CXE: The sum of P wave amplitudes in II, III and aVF increased at EBC (P<0.05). The T wave amplitude in V1 decreased at EBC (P<0.05). QTc (Bazett’s and Fridericia’s) increased on arrival at EBC (P<0.05). TE: QTc (Bazett’s and Fridericia’s) increased on ascent to high altitude. QTc (Bazett’s) increased following ascent from Namche Bazaar (3500m) to Gorak
Shep (5200m) (P<0.05). AHS: QTc (Bazett’s and Fridericia’s) increased in hypoxia (P<0.05).
Conclusion: Significant changes in rate, rhythm and morphology occur in healthy lowland residents who are exposed to hypoxic conditions.