Assessment of Cardiac Arrhythmias at Extreme High Altitude Using an Implantable Cardiac Monitor

Boos, Christopher J.; Holdsworth, David; Woods, David R.; O’Hara, John; Brooks, Naomi; Macconnachie, Lee; Bakker-Dyos, J; Paisey, John; Mellor, Adrian

doi:10.1161/circulationaha.116.026584

Cited by 19 publications

(15 citation statements)

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“…Previous evidence has demonstrated that chronic exposure to low-oxygen environments [i.e., high-altitude (HA)] increases the prevalence of arrhythmic events in low-altitude dwelling populations. Such events have been previously documented in acclimatized Lowlanders during periods of elevated stress (i.e., physical exertion) above 4000 m (Woods et al, 2008;Behn et al, 2014;Boos et al, 2017). Recently, we demonstrated significant brady-arrhythmic events were present during a brief bout of apneic stress in Lowlanders at 5050 m (Busch et al, 2017), but not native Nepalese Sherpa.…”

Section: Introductionsupporting

confidence: 63%

“…Previously, supplemental oxygen (FiO 2 1.00) has abolished these events during apnea at 5050 m (Busch et al, 2017), demonstrating the peripheral chemoreceptors likely play a considerable role. However, any considerable autonomic stress (Woods et al, 2008;Boos et al, 2017) appears to be capable of evoking arrhythmogenesis independent of significant chemoreflex activation, though further research is required. Although these events were benign in healthy Lowlanders, future direction should be focused on clinical populations at greater risk of adverse complications arising from arrhythmogenesis at altitude, including conditions where consistent cardiac vagal innervation may occur such as sleep disordered breathing (i.e., Cheyne-Stokes respiration) (Cummings and Lysgaard, 1981) commonly observed at altitude.…”

Section: Discussionmentioning

confidence: 99%

“…Another consideration is participant recruitment, with Lowlanders consisting of research members involved in the expedition and all Andeans being locally recruited from around Cerro de Pasco. Due to the constraints of an expedition setting Lowlanders were tested on days 3-8 postarrival at 4330 m. As of this study, the exposure duration and minimum altitude necessary to promote arrhythmogenesis is not currently known, though previous findings suggest that they are more likely during the transition from acute hypoxia exposure to longer duration travel at altitudes above 4000 m (Cummings and Lysgaard, 1981;Woods et al, 2008;Behn et al, 2014;Brooks et al, 2017;Busch et al, 2017). Though the duration of the testing period in the current study aligns with the testing periods of Lowlanders from our previous work (Busch et al, 2017), the time course for the development of conduction abnormalities will need to be addressed on future expeditions.…”

Section: Considerations and Limitationsmentioning

confidence: 99%

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Global REACH: Assessment of Brady-Arrhythmias in Andeans and Lowlanders During Apnea at 4330 m

et al. 2020

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Background: Ascent to altitude increases the prevalence of arrhythmogenesis in lowaltitude dwelling populations (Lowlanders). High altitude populations (i.e., 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 4330 m (Cerro de Pasco, Peru). ECG rhythm and HR were assessed at both rest and during maximal volitional apnea. 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-ventricular 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. Conclusion: 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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Section: Introductionsupporting

confidence: 63%

Section: Discussionmentioning

confidence: 99%

Section: Considerations and Limitationsmentioning

confidence: 99%

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Global REACH: Assessment of Brady-Arrhythmias in Andeans and Lowlanders During Apnea at 4330 m

et al. 2020

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“…We were only able to absolutely confirm the presence of normal sinus rhythm at the time of the 36 sec ECG capture. Whilst this does not fully exclude the possibility of arrhythmias at other time points visualization of the IBI data coupled with the altitude and healthy population studied would strongly suggest against the presence of an undetected significant cardiac arrhythmia (Boos et al, 2017a). …”

Section: Discussionmentioning

confidence: 93%

High Altitude Affects Nocturnal Non-linear Heart Rate Variability: PATCH-HA Study

Boos

Bye²,

Sevier

et al. 2018

Front. Physiol.

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Background: High altitude (HA) exposure can lead to changes in resting heart rate variability (HRV), which may be linked to acute mountain sickness (AMS) development. Compared with traditional HRV measures, non-linear HRV appears to offer incremental and prognostic data, yet its utility and relationship to AMS have been barely examined at HA. This study sought to examine this relationship at terrestrial HA.Methods: Sixteen healthy British military servicemen were studied at baseline (800 m, first night) and over eight consecutive nights, at a sleeping altitude of up to 3600 m. A disposable cardiac patch monitor was used, to record the nocturnal cardiac inter-beat interval data, over 1 h (0200–0300 h), for offline HRV assessment. Non-linear HRV measures included Sample entropy (SampEn), the short (α1, 4–12 beats) and long-term (α2, 13–64 beats) detrend fluctuation analysis slope and the correlation dimension (D2). The maximal rating of perceived exertion (RPE), during daily exercise, was assessed using the Borg 6–20 RPE scale.Results: All subjects completed the HA exposure. The average age of included subjects was 31.4 ± 8.1 years. HA led to a significant fall in SpO2 and increase in heart rate, LLS and RPE. There were no significant changes in the ECG-derived respiratory rate or in any of the time domain measures of HRV during sleep. The only notable changes in frequency domain measures of HRV were an increase in LF and fall in HFnu power at the highest altitude. Conversely, SampEn, SD1/SD2 and D2 all fell, whereas α1 and α2 increased (p < 0.05). RPE inversely correlated with SD1/SD2 (r = -0.31; p = 0.002), SampEn (r = -0.22; p = 0.03), HFnu (r = -0.27; p = 0.007) and positively correlated with LF (r = 0.24; p = 0.02), LF/HF (r = 0.24; p = 0.02), α1 (r = 0.32; p = 0.002) and α2 (r = 0.21; p = 0.04). AMS occurred in 7/16 subjects (43.8%) and was very mild in 85.7% of cases. HRV failed to predict AMS.Conclusion: Non-linear HRV is more sensitive to the effects of HA than time and frequency domain indices. HA leads to a compensatory decrease in nocturnal HRV and complexity, which is influenced by the RPE measured at the end of the previous day. HRV failed to predict AMS development.

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“…Both the acute adaptation and the chronic remodelling of the cardiac structure and function may be required for facilitating O 2 delivery in HA travellers and highlanders [ 5 ]. In addition, acute HA or hypoxia exposure induces alterations in electrophysiological parameters including decreases in the amplitude of the P/QRS/T waves during a hypoxia exercise test [ 6 ] and tachyarrhythmias at HA above 4100 m [ 7 ]. However, the characteristics of these cardiovascular changes in patients with acute mountain sickness (AMS) have not been thoroughly illuminated.…”

Section: Introductionmentioning

confidence: 99%

Low Stroke Volume Index in Healthy Young Men Is Associated with the Incidence of Acute Mountain Sickness after an Ascent by Airplane: A Case-Control Study

Liu

et al. 2020

BioMed Research International

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Background. The aims of this study were to explore the characteristics of left ventricular (LV) functional changes in subjects with or without acute mountain sickness (AMS) and their associations with AMS incidence. Methods. A total of 589 healthy men were enrolled and took a trip from Chengdu (500 m, above sea level (asl)) to Lhasa (3700 m, asl) by airplane. Basic characteristics, physiological data, and echocardiographic parameters were collected both at Chengdu and Lhasa, respectively. AMS was identified by the Lake Louise Questionnaire Score. Results. The oxygen saturation (SpO2), end-systolic volume index, end-diastolic volume index (EDVi), stroke volume index (SVi), E-wave velocity, and E/A ratio were decreased, whereas the heart rate (HR), ejection fraction, cardiac index (CI), and A-wave velocity were increased at the third day after arrival, as evaluated by an oximeter and echocardiography. However, AMS patients showed higher HR and lower EDVi, SVi, CI, E-wave velocity, and E/A ratio than AMS-free subjects. Among them, SVi, which is mainly correlated with the changes of EDVi and altered LV filling pattern, was the most valuable factor associated with AMS incidence following receiver-operator characteristic curves and linear and Poisson regression. Compared with subjects in the highest SVi tertile, subjects in the middle SVi tertile showed higher multivariable Incidence Rate Ratios (IRR) for AMS with higher incidences of mild headache and gastrointestinal symptoms, whereas subjects in the lowest SVi tertile showed even higher multivariable IRR with higher incidences of all the symptoms. Conclusions. This relatively large-scale case-control study revealed that the reduction of SVi correlated with the altered LV filling pattern was associated with the incidence and clinical severity of AMS.

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Assessment of Cardiac Arrhythmias at Extreme High Altitude Using an Implantable Cardiac Monitor

Cited by 19 publications

References 5 publications

Global REACH: Assessment of Brady-Arrhythmias in Andeans and Lowlanders During Apnea at 4330 m

Global REACH: Assessment of Brady-Arrhythmias in Andeans and Lowlanders During Apnea at 4330 m

High Altitude Affects Nocturnal Non-linear Heart Rate Variability: PATCH-HA Study

Low Stroke Volume Index in Healthy Young Men Is Associated with the Incidence of Acute Mountain Sickness after an Ascent by Airplane: A Case-Control Study

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