Why the study?
It was unknown whether arrhythmia-resistant adaptations observed in some high-altitude populations exist in other groups, including healthy and chronic mountain sickness-afflicted Andeans under acute apneic stress at altitude.
Does maximal volitional apnea at high altitude induce arrhythmias differently in high-altitude adapted Andeans compared to Lowlanders?
Does maximal volitional apnea at high altitude induce arrhythmias differently in high-altitude adapted Andeans compared to Lowlanders?
Andeans exhibit preserved heart rate responses and an absence of arrhythmias during volitional apnea at high altitude compared to lowlanders, suggesting cardio-resistant adaptations.
Answers are grounded in this paper and cite their sources.
Absence of arrhythmias in Andeans with or without CMS supports altitude-resistant adaptations; extends Sherpa observations but remains hypothesis-generating.
BACKGROUND: Ascent to altitude increases the prevalence of arrhythmogenesis in low-altitude dwelling populations (Lowlanders). High altitude populations (ie. Nepalese Sherpa) may have arrhythmias resistant adaptations that prevent arrhythmogenesis at altitude, though this has not been documented in other High altitude groups, including those diagnosed with chronic mountain sickness (CMS). We investigated whether healthy (CMS-) and CMS afflicted (CMS+) Andeans exhibit cardiac arrhythmias under acute apneic stress at altitude. METHODS AND RESULTS: Electrocardiograms (lead II) were collected in CMS- (N=9), CMS+ (N=8), and Lowlanders (N= 13) following several days at 4330m (Cerro de Pasco, Peru). ECG rhythm and HR were assessed at both rest and during maximal volitional apnea (End-Expiratory [EXP]). Both CMS- and CMS+ had similar basal HR (69 ± 8 beats/min vs. 62 ± 11 beats/min), while basal HR was higher in Lowlanders (77 ± 18 beats/min; P<0.05 versus CMS+). Apnea elicited significant bradycardia (nadir -32 ± 15 beats/min; P<0.01) and the development of arrhythmias in 8/13 Lowlanders (junctional rhythm, 3° atrio-venticular block, sinus pause). HR was preserved was prior to volitional breakpoint in both CMS- (nadir -6 ± 1 beat/min) and CMS+ (1 ±12 beats/min), with 2/17 Andeans developing arrhythmias ( 1 CMS+ and 1 CMS-; both Premature Atrial Contraction) prior to breakpoint. CONCLUSIONS: Andeans showed an absence of arrhythmias and preserved HR response to volitional apnea at altitude, demonstrating that potential cardio-resistant adaptations to arrhythmogenesis exist across permanent HA populations. Acclimatized Lowlanders have further demonstrated an increased prevalence of arrhythmias at altitude.
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Busch et al. (2020) studied this question.
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