Evaluating the safety of high-altitude travel in patients with adult congenital heart disease

Cardiopulmonary exercise response at high altitude in patients with congenital heart disease: a systematic review and meta-analysis

Background

An increasing number of patients with congenital heart disease (CHD) engage in physical activities and may exercise at high altitudes (HA). The physiological adaptations required at HA and their implications on individuals with CHD, especially during exercise, remain underexplored. This systematic review aims to investigate cardiopulmonary exercise responses to short-term HA exposure in individuals with CHD.

Methods

A literature search was performed across PubMed, Cochrane Library, Scopus, Embase, and SPORTDiscus. The search focused on studies comparing patients with CHD to healthy controls, specifically assessing cardiorespiratory responses during cardiopulmonary exercise testing at HA (≥2,500 m) and low altitude (LA). A meta-analysis of the differences in the main cardiorespiratory adaptations during exercise from LA to HA was performed, comparing patients with CHD and controls.

Results

Of the initial 4,500 articles, four studies met the inclusion criteria, encompassing 150 participants (74 with CHD and 76 controls). Almost all the patients with CHD had lower cardiorespiratory fitness and efficiency both at LA and HA compared to the controls. Nevertheless, the patients with CHD showed a smaller decrease in peak workload [10.61 W (95% CI: 2.33-18.88)] and peak saturation [1.22% (95% CI: 0.14-2.30)] between LA and HA compared to the controls. No participants presented exercise-induced symptoms.

Conclusion

Short-term exposure to HA appears to be relatively well-tolerated by individuals with low-risk CHD, without a significantly different impact on cardiorespiratory response compared to healthy controls. Further research should confirm these outcomes and explore the long-term effects of higher altitude exposure as comprehensive recommendations for these patients are lacking.

Clinical recommendations for high altitude exposure of individuals with pre-existing cardiovascular conditions: A joint statement by the European Society of Cardiology, the Council on Hypertension of the European Society of Cardiology, the European Society of Hypertension, the International Society of Mountain Medicine, the Italian Society of Hypertension and the Italian Society of Mountain Medicine

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Secundum atrial septal defect in adults: a practical review and recent developments

Secundum atrial septal defect (ASDII) is a common congenital heart defect that causes shunting of blood between the systemic and pulmonary circulations. Patients with an isolated ASDII often remain asymptomatic during childhood and adolescence. If the defect remains untreated, however, the rates of exercise intolerance, supraventricular arrhythmias, right ventricular dysfunction and pulmonary arterial hypertension (PAH) increase with patient age, and life expectancy is reduced. Transcatheter and surgical techniques both provide valid options for ASDII closure, the former being the preferred method. With the exception of those with severe and irreversible PAH, closure is beneficial to, and thus indicated in all patients with significant shunts, regardless of age and symptoms. The symptomatic and survival benefits conferred by defect closure are inversely related to patient age and the presence of PAH, supporting timely closure after diagnosis. In this paper we review the management of adult patients with an isolated ASDII, with a focus on aspects of importance to the decision regarding defect closure and medical follow-up.

Anti-hypotensive treatment and endothelin blockade synergistically antagonize exercise fatigue in rats under simulated high altitude

Rapid ascent to high altitude causes illness and fatigue, and there is a demand for effective acute treatments to alleviate such effects. We hypothesized that increased oxygen delivery to the tissue using a combination of a hypertensive agent and an endothelin receptor A antagonist drugs would limit exercise-induced fatigue at simulated high altitude. Our data showed that the combination of 0.1 mg/kg ambrisentan with either 20 mg/kg ephedrine or 10 mg/kg methylphenidate significantly improved exercise duration in rats at simulated altitude of 4,267 m, whereas the individual compounds did not. In normoxic, anesthetized rats, ephedrine alone and in combination with ambrisentan increased heart rate, peripheral blood flow, carotid and pulmonary arterial pressures, breathing rate, and vastus lateralis muscle oxygenation, but under inspired hypoxia, only the combination treatment significantly enhanced muscle oxygenation. Our results suggest that sympathomimetic agents combined with endothelin-A receptor blockers offset altitude-induced fatigue in rats by synergistically increasing the delivery rate of oxygen to hypoxic muscle by concomitantly augmenting perfusion pressure and improving capillary conductance in the skeletal muscle. Our findings might therefore serve as a basis to develop an effective treatment to prevent high-altitude illness and fatigue in humans.

Cardiovascular medicine at high altitude

Altitude physiology began with Paul Bert in 1878. Chronic mountain sickness (CMS) was defined by Carlos Monge in the 1940s in the Peruvian Andes as consisting of excess polycythemia. Hurtado et al performed studies in the Peruvian Andes in the 1950s to 1960s which defined acclimatization in healthy altitude natives, including polycythemia, moderate pulmonary hypertension, and low systemic blood pressure (BP). Electrocardiographic changes of right ventricular hypertrophy (RVH) were noted. Acclimatization of newcomers to altitude involves hyperventilation stimulated by hypoxia and is usually benign. Acute mountain sickness (AMS) in travelers to altitude is characterized by hypoxia-induced anorexia, dyspnea, headache, insomnia, and nausea. The extremes of AMS are high-altitude cerebral edema and high-altitude pulmonary edema. The susceptible high-altitude resident can lose their tolerance to altitude and develop CMS, also referred to as Monge disease. The CMS includes extreme polycythemia, severe RVH, excess pulmonary hypertension, low systemic BP, arterial oxygen desaturation, and hypoventilation.

Pulse oximetry at high altitude

Pulse oximetry is a valuable, noninvasive, diagnostic tool for the evaluation of ill individuals at high altitude and is also being increasingly used to monitor the well-being of individuals traveling on high altitude expeditions. Although the devices are simple to use, data output may be inaccurate or hard to interpret in certain situations, which could lead to inappropriate clinical decisions. The purpose of this review is to consider such issues in greater detail. After examining the operating principles of pulse oximetry, we describe the available devices and the potential uses of oximetry at high altitude. We then consider the pitfalls of pulse oximetry in this environment and provide recommendations about how to deal with these issues. Device users should recognize that oxygen saturation changes rapidly in response to small changes in oxygen tensions at high altitude and that device accuracy declines with arterial oxygen saturations of less than 80%. The normal oxygen saturation at a given elevation may not be known with certainty and should be viewed as a range of values, rather than a specific number. For these reasons, clinical decisions should not be based on small differences in saturation over time or among individuals. Effort should also be made to minimize factors that cause measurement errors, including cold extremities, excess ambient light, and ill-fitting oximeter probes. Attention to these and other issues will help the users of these devices to apply them in appropriate situations and to minimize erroneous clinical decisions.