HEART AND BLOOD VESSEL DISORDERS - Medicine for Mountaineering and Other Wilderness Activities - page 227

Partial syncope may occur as a result of postural (orthostatic) hypotension (a fall in
bloodpressureuponassuminganerectposture).Theindividualexperiencesfaintnessupon
standingafteraprolongedperiodoflyingdownorsitting,suchasuponarisinginthemorn-
ing or after a large meal, particularly when alcoholic beverages have been consumed. Pos-
turalhypotensionisacommonprobleminpersonswhoarereceiving drugtherapyforhigh
bloodpressureorcoronaryarterydisease,particularly ifthepersonisdehydrated.Reassur-
ance and a decrease in the medication dose are usually the only necessary measures.
Individuals more than sixty years old have a higher incidence of true syncope resulting
from cardiac disease and are less likely to have benign, vasodepressor syncopal attacks.
Such persons also are more susceptible to postural hypotension, particularly if medications
for hypertension are being taken.
Cardiac Syncope
Cardiac syncope, usually a form of true syncope, is loss of consciousness caused by
heart disease. Two forms are recognized: exertional and arrhythmic. Exertional syncope
occurs during a burst ofheavy effort such as walking fast uphill. Unconsciousness may oc-
cur suddenly or may be preceded by a “graying out” sensation, severe dizziness, or weak-
ness. Convulsive movements may occur. Exertional syncope most frequently occurs in in-
dividualswithaorticstenosis(narrowingoftheoutletvalvefromtheleftventricle),implies
severe aortic valvular disease, and should prompt evacuation. Most affected individuals
have a history of similar episodes.
Arrhythmic syncope occurs as the result of an abnormal cardiac rhythm, either a sudden
increaseinheartrate(tachycardia)oramarkedslowingortemporarycessationoftheheart-
beat (heart block). The episode may occur suddenly, without warning, and the person may
fall and be injured.
The blood pressure should be measured, the heart rate should be determined, and the
rhythm should be evaluated. The individual should rest, with sedation if needed, for six to
twelve hours and then be evacuated to a physician's care. Cardiac syncope may be an early
warning of heart disease that can cause sudden death.
MINOR DISTURBANCES OF CARDIAC RHYTHM
Sinus Tachycardia
Anxious individuals, after heavy exertion or at high altitude, may become aware of a
rapid, forceful heartbeat pounding in the chest and fear they have heart disease. If the heart
rate does not exceed
120 beats per minute and gradually slows with rest, a diagnosis of harmless sinus ta-
chycardia may be made. No specific treatment except rest, hydration, and reassurance is
necessary.