Travel Reference
In-Depth Information
Data are inadequate to draw firm conclusions about the risk of myocardial infarction
and sudden death at altitude in those with coronary artery disease. The limited available
evidence does not identify an increased risk, particularly in individuals who have been ex-
ercising regularly at low altitude.
Does Altitude Provoke Abnormal Cardiac Rhythms?
In older individuals who ascend to altitude, a number of investigators have noted an
increased number of extrasystoles (premature beats, paroxysmal ventricular contractions,
or PVCs) (
Chapter 17: Heart and Blood Vessel Disorders
). However, the PVCs appeared
benign and did not suggest a propensity to life-threatening abnormal rhythms. Biochemic-
al studies indicated that increased secretion of adrenaline and related compounds was the
most likely cause. Most persons returned to normal after a few days, and no dire events
have been reported.
Persons with troublesome or severe rhythm disorders have not been evaluated system-
atically at high altitude. No anecdotal reports of exacerbations of supraventricular tachy-
cardia or other common rhythm abnormalities have been published, and no information
aboutwhetherortowhatextentascenttohighaltitudeincreasesriskforthosewithspecific
rhythm disorders at sea level is available.
Cold, Altitude, and Ischemia
Whether cold provokes myocardial ischemia at altitude has not been studied but seems
likely. At sea level, breathing cold air and/or exercising in a cold environment by individu-
als who already had exercise-induced angina limited their exercise tolerance even more.
The cold-induced increase in heart rate and blood pressure was similar to that reported at
moderate altitude in temperate conditions. Therefore, cold and altitude might interact to
inciteeffort-inducedangina.Becausehigh-altitudelocationsarecommonlycold,thisques-
tion of interaction deserves pursuit.
The Risk of Acute Ischemic Events in Those Without Coronary Artery Disease
Inadditiontoarteriosclerosis,coronaryarteryspasmhasalsobeeninvokedasapossible
mechanismforcardiacischemiaataltitude.Spasmwouldnotbesurprisingataltitudesince
the sympathetic stimulation and respiratory alkalosis that typically occur are known coron-
ary vasoconstrictors. However, only one individual with altitude-induced coronary artery
spasm has been identified.
Advice for Persons with Coronary Artery Disease Regarding Altitude
The stress of high altitude on the coronary circulation appears to be minimal at rest but
significant inconjunctionwithexercise.Personsexercisingataltitude aremoreatriskthan
those merely sitting in a car or an airplane. European studies imply that an exercise pro-
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