Work at High Altitude After Coronary Stenting: Safe?

To the Editor:

We report the case of a 49-year-old male engineer with a history of coronary heart disease (CHD) treated with 2 drug-eluting stents (Cypher Select, DES, Cordis Co, USA) in the right and left coronary arteries, and with aspirin (300 mg) and clopidogrel (75 mg) once daily. Six months post-stenting he was free of angina and coronary angiography showed no re-strictures. Despite strong advice not to travel to high altitude he decided to work again as an engineer on the Qinghai-Tibet railway at the site of the Fenghuoshan tunnel construction (4905 m, PB 417 Torr) 2 years after the stenting procedure. On May 1, 2001, he gradually ascended from Beijing (76 m) to Golmud (2808 m) by train for about 34 hours and then from Golmud to Fenghuoshan by car for 6 hours. He then worked at 4905 m and slept at 4600 m for 10 days, declaring that he felt better than pre-stenting at sea level. Subsequently, from 2002 through 2005, he spent 10 periods of 10 to 15 days of working and living at these altitudes without significant symptoms or signs of illness. Each time after arrival at 4905 m he developed mild weakness, some anorexia, and slightly disturbed sleep but no headache. The Lake Louise acute mountain sickness (AMS) scores on the first day at 4905 m varied between 1 and 2, less than the minimum AMS criterion score of ≥3. Daily 12-lead resting electrocardiograms showed no evidence for myocardial ischemia or arrhythmia. Two-dimensional echocardiography indicated normal left ventricular function. Resting arterial oxygen saturation (Sao₂) varied between 78% and 89%. Double product (heart rate x systolic pressure) was elevated by 12% at rest 12 hours after arrival at altitude and progressively fell to reach sea level values after 1 week. Sleep monitoring at 4600 m showed frequent arousals, periodic breathing, and a longer stage I non–rapid eye movement (NREM) sleep pattern accompanied by average overnight Sao₂ levels lower than when awake (67% vs 88%). Since the tunnel was completed on June 30, 2006, the patient has lived and worked in Beijing (76 m) without any obvious health problems to date.

To the best of our knowledge, this is the first report of a patient postcoronary stenting who intermittently ascended to and worked at an altitude near 5000 m. The question on how well patients tolerate high altitude after coronary bypass surgery remains debated.^1,2 Several authors suggest that for asymptomatic patients with good exercise tolerance, high altitude exposure represents acceptable risk.^2,3 The same consideration would apply to patients postcoronary angioplasty. ⁴ Others disagree arguing that residual disease is likely and represents a contraindication for altitude exposure. ⁵ Our case of a symptom-free CHD patient, post-stenting, without re-strictures at 6 months and with an uneventful follow-up for 2 years, would indicate that the risk can be low. The patient travelled repeatedly to almost 5000 m, feeling well and remaining free of angina. There was no evidence of myocardial ischemia or arrhythmia in spite of decreased saturation levels. Increased cardiac work during the first week after arrival at altitude was probably due to a temporary increase in sympathetic nervous system activity. ⁶ Sleep disturbance and nocturnal desaturation are common. ³ Recently, Marticorena et al studied the impact of the simulated hypoxia technique–hypobaric chamber to rehabilitate CHD by-passed with or without myocardial infarction. ⁷ They exposed 6 lowland male CHD patients to 14 sessions of intermittent hypobaric hypoxia exposure at a simulated altitude of 4200 m, and found that myocardial perfusion was significantly improved, thus suggesting that this could be an alternative for the management of patients with chronic CHD. ⁸

Since the prevalence of CHD patients treated with coronary stents is increasing, readiness for travel to altitude traveling merits attention. Our case would favor a relaxed position for those patients who are free of symptoms. By contrast, unstable CHD, even post-stenting, should remain a contraindication for travel to high altitude.