Effects of Altitude Exposure on Heart Disease Patients
ABSTRACT & COMMENTARY
Synopsis: Patients with ischemic heart disease and moderately impaired left ventricular function tolerate exercise at high altitude well.
Source: Erdmann J, et al. Am J Cardiol 1998;81:266-270.
Millions of patients travel to altitudes above 6000 ft. every year, yet we have few data about the safety of altitude exposure in patients with ischemic heart disease. Thus, Erdmann et al from Switzerland studied 23 coronary artery disease patients with impaired left ventricular function (ejection fraction £ 45%) and 23 normal controls between the ages of 35 and 65 years. Patients with overt heart failure, symptomatic ischemia, or significant arrhythmias during exercise testing and resting severe hypertension (> 200/110) were excluded. The subjects underwent symptom-limited bicycle exercise testing at 2500 ft; two days later, the subjects repeated the exercise testing at 6250 ft. Endurance decreased significantly at the higher altitude in both groups but only by 3-6%. Fatigue halted exercise commonly at 2500 ft., whereas dyspnea and leg pains were more common at 6250 ft. No exercise test was terminated for ischemic events, and there was no observed increase in arrhythmias. Comparing the two groups, the only impressive difference was the greater workload achieved in the normal group. Erdmann et al conclude that patients with ischemic heart disease and moderately impaired left ventricular function tolerate exercise at high altitude well.
COMMENT BY MICHAEL H. CRAWFORD, MD
Physicians are frequently asked if it is safe for cardiac patients to vacation at high altitudes, yet there are few data on this issue. The first concern is air travel, since airplane cabins are pressurized to about 7000 ft. (equivalent to Santa Fe, NM). In an airplane, one is mostly at rest, so it is interesting that, in this study, the decrease in oxygen saturation at rest at 6250 ft. (i.e., Lake Tahoe, CA) was insignificantly reduced compared to 2500 ft. (Tucson, AZ). This may explain why most patients are asymptomatic in an airplane. Exercise at altitude is another matter. This study showed that oxygen saturation decreased with exercise in both groups but was more profound in the normals-perhaps because they performed more exercise work. Thus, exercise symptoms would be expected. Interestingly, there were no symptoms of angina, nor was there an increase in ischemic changes or arrhythmias with exercise at the higher altitude.
One explanation for the negative study may have been patient selection. These were fairly fit middle-aged men, despite having moderately reduced left ventricular function due to ischemic heart disease. Perhaps a less fit, more symptomatic group would not have done as well. Thus, it appears that stable patients with ischemic heart disease, even with moderately reduced left ventricular function (class I-II) can be expected to do well at moderately high altitudes. More symptomatic patients (class III-IV) or those with worse left ventricular function may not do as well at higher altitudes, and even the class I-II patients may decompensate. This has generally been my experience dealing with tourists and new retirees in Albuquerque (5000 ft.) and Santa Fe (7200 ft). However, after 6-8 weeks, most cardiac patients adjust to the altitude and can resume their normal activities. On the other hand, pulmonary disease patients rarely adjust and should be advised not to visit or live in higher altitudes without supplemental oxygen. (Dr. Crawford is Robert S. Flinn Professor, Chief of Cardiology, University of New Mexico, Albuquerque.)