Download Prevention and Management of Cardiovascular Events during Travel

REVIEW ARTICLES
Prevention and Management of Cardiovascular Events during
Travel
Miltiadis N Leon, Mujahed Luted and Francisco Fuentes
acclimated to high altitudes.This develops over 2 weeks,
but its benefits may also be lost in a couple ofweeks. Exercise capacity of individuals also decreases with high altitudes, and further reduced arterial oxygen content may
cause episodes of ischemia in patients with existing comnary artery disease.
High altitude illness is another potential problem that
may occur when the rate of ascent to high altitude areas
exceeds the body's rate to acclimatize to the sudden
decrease of arterial oxygen content. The most dramatic
manifestation of acute mountain sickness from the cardiovascular standpoint is high altitude pulmonary edema
(HAPE),which occurs in otherwise healthy individuals
who ascend to more than 8000 feet in less than 1 day.
T h e clinically apparent incidence of this syndrome,
which presents as shortness of breath, cyanosis, tachycardia,
and tachypnea,is estimated to be 6.4% cases per 100 exposures in subjects less than 21 years old and .4% in older
people.' T h e mechanism for HAPE is not exactly
Individuals who had previously developed
HAPE are particularly more susceptible to recurrent
episodes.'Reversal of the symptoms is usually rapid (less
than 48 hours) upon returning to lower altitudes and/or
by administration of oxygen. When descent cannot be
done immediately, medications such as acetazolamide,
steroids, diuretics (i.e., furosemide, spironolactone, mannitol) and nifedipine have been used effectively as temporizing measure^.^ Individuals who plan to travel to high
altitude areas need to keep in mind that gradual ascent,
which allows time for acclimatization and limited physical exertion, is the best way to prevent high altitude illness. For people who have been identified as being
previously susceptible to HAPE and for those who must
ascend rapidly, such as rescue workers, pharmacologic prophylaxis is recommended. Acetazolamide 250 mg every
8-12 hours starting 24 hours before ascent and continued for 72 hours at altitude has been shown to be effective and has been approved by the FDA for this
p u r p o ~ e . ~ Dexamethasone
~'~~"
4 mg every 6 hours, beginning 48 hours before ascent, has also been recommended
for prophylaxis, either being given alone or in combination with acetazolamide.'O~''
Traveling has been associated with an increased
incidence of carhovascular events among adult travelers
who have existing cardiopulmonary diseases.'" Assessment of the patient's cardiovascular status and risk prior
to travel represents the first step in the evaluation process
and was discussed thoroughly in a paper by the same
authors published in the previous issue ofjournal ofrravel
Medicine.Therefore, prevention and management of cardiovascular events during travel are very important for
the physicians who are involved in treating patients with
heart disease who intend to travel. The current data
regarding this crucial issue are limited. After careful
assessment, the physician specializing in travel medicine
needs to provide patients with existing cardiopulmonary
disease with specific instructions to prevent adverse cardiovascular events during travel, as well as measures that
they should undertake if such an event occurs.
Risk of High Altitude Travel
Traveling at high altitudes has been associated with
significant physiologic changes of the cardiovascular system. The reduction in partial pressure of oxygen at altitudes above 8000 feet above sea level causes an increase
in myocardial oxygen consumption as heart rate and,
therefore, cardlac output are both increased to compensate for the reduction in arterial oxygen saturation. Stroke
volume usually remains unchanged. Polycythemia is
another compensatory mechanism developed in people
Miltiadis N. Leon, MD: Cardiology Fellow, Department of
Internal Medicine, Division of Cardiology; Mujahed Lateef:
Medical Student 111; Francisco Fuenfes, MD, FACC: Professor
of Medicine, Department of Internal Medicine, Division of
Cardiology, University of Texas-Houston Medical School.
Reprint requests: Francisco Fuenfes, MD, Professor of
Medicine, University of Texas-Houston Medical School,
Division of Cardiology, 6431 Fannin St., MSB 1.246, Houston,
Texas 77030, USA
J Travel Med 1996;4:227-230.
227
228
Prevention and Management of Cardiovascular
Events in Patients with Cardiovascular Disease
during Travel
Certain aspects of traveling can contribute to cardiac events in patients with heart diseases. Physical stress
due to lifting luggage and the potential need to cover significant distances in a short period of time can both precipitate angina or cause significant dyspnea in patients
with coronary artery disease (CAD) or congestive heart
failure (CHF),respectivelyTherefore, patients must plan
carefully and avoid physical activities that exceed their
individual exercise capacity.
Every patient also needs to be aware that any worsening of symptoms from existing cardiovascular problems
needs to be evaluated by a physician and that travel must
be postponed until the medical evaluation is completed.
It is also important that all patients with heart disease carry
a copy of their most recent electrocardiogram during
travel.This becomes extremely u s e l l for comparison with
a tracing obtained during an acute event.
Deep venous thrombosis and pulmonary emboli
after prolonged flight can be another potential source for
cardiopulmonary complications. Patients with existing
C H F belong to this high risk gr0up.A pulmonary embolus may not become evident until several days after a flight,
when vigorous exercise can dislodge a clot. Ensuring adequate hydration and avoidance of prolonged posture
position for long hours are preventive measures for the
patient with existing cardiovascular disease.12 Low dose
aspirin can also be considered in high risk groups (i.e.,
patients with dilated cardiomyopathy and low ejection
fraction) who are not on anticoagulation therapy with
Coumadin.
The uninterrupted use of cardiac medications is
also very important, since omission of few dosages can
create exacerbation of the symptoms of underlying disease. Cardiac patients are advised to take all their medications in carry-on luggage and a sufficient quantity to
last for the entire trip. Patients with CAD should also have
sublingual nitroglycerin available for immediate use.A prolonged episode of chest pain suggestive of angina should
prompt the patient to seek medical attention and to
immediately take the sublingual nitroglycerin and chew
an aspirin. This should be done even if the patient had
taken an aspirin earlier in the same day, since the
antiplatelet effect of aspirin cannot be predicted in each
patient and prolongation of the bleeding time can vary
between patients (as it is dependent upon chronic or intermittent aspirin usage). l 3 * I 4 Cardiac patients must also
keep in mind that their medications may not be available in some foreign countries.They should try to refill
these with ones with the same generic name since variations in potency in some preparations-particularly
J our nal of Travel Medicine, Volume 3, Number 4
digitalis-do exist. Patients who are on anticoagulation
medication with Coumadin need to continue checking
their prothrombin time (PT) using the international
normalized ratio (INR) according to the recommendations of their primary physician. The level of the anticoagulant should be based on the determination of the
I N R , which provides a common basis for the communication of P T results among physicians; the sensitivity
of the thromboplastin reagent used by some laboratories
in different countries may vary.
Cardiac patients with permanently implanted cardiac devices (i.e., pacemakers and defibrillators) constitute a group that requires specific instructions before
traveling. Patients with pacemakers need to travel with
a copy of their electrocardiogram with and without the
pacemaker functioning. Transtelephonic pacemaker
recordings can be made via international satellite communications between many countries and the United
States.They can also be provided with the telephone number of the manufacturer of their device at the country
to which they plan to travel. In this way, information
regarding specialized medical services can be provided,
if needed.AU patients with implanted devices need to follow the recommended schedules for check-ups, and
such appointments should not be missed because of
traveling. Magnets that are used in the airports for personal search and security reasons have n o adverse longterm effects on the function of these devices in most of
the currently used models.Application of the magnet over
the generator of the defibrillator may cause the device
to temporarily become nonfunctional, which means that
therapy may not be delivered for that short period of time.
Removal of the magnet will allow the device to function normally again. However, some defibrillators made
by CPI (i.e., CPI model 1600, 1555, 1550, 1625) can
remain nonoperational even after the magnet is removed
from exposure. Patients that carry such devices need to
be provided with a specific card from their physician
warning airline security to avoid using magnets for personal search.
Environment changes can also adversely affect
patients with cardiovascular diseases. I n warm climates,
unceasing fluid losses combined with continued use of
diuretics and antihypertensive medication may create a
state of hypovolemia and postural hypotension. The
opposite is true in cold climates, where many patients with
stable angina have noticed worsening of their symptoms when exposed to cold weather. It has been postulated that this is due to a cold-induced increase in
peripheral vascular resistance, thereby resulting in an
increased myocardial oxygen demand that allows the
ischemic threshold to be reached earlier in a cold environment but remains unchanged compared with the
ischemic threshold at normal temperatures.” However,
Leon e t a l
Prevention a n d Management o f Cardiovascular Events d u r i n g T r a v e l
Table 1 Recommendations for the Prevention and
Management of Adverse Cardiovascular Events during
Travel
229
3. Uninterrupted use of all cardiac medications during
travel, with particular attention to replacing them with
the same generic name.
response t o exercise may be playing a role, since it has
been demonstrated that a cold-pressure test induced
vasoconstriction in atherosclerotic coronary arteries.
Cold can also promote coronary spasm i n patients with
variant angina.I7
Another issue of particular interest is the managem e n t of cardiovascular events during air travel and particularly that of sudden cardiac death. In an analysis by
Cummins e t a1 of 577 in-flight deaths over a n %year
period, more than half of these deaths were due to sudd e n cardiac events, as best as could be determined.4
Since most of these cardiac arrests will be witnessed, and
ventricular fibrillation has been denionstrated i n 60-70%
of these individuals, we can assume that the availability
of external defibrillators during flight could be life saving."' Therefore, we recommend that basic and advanced
cardiac life support training b e provided to all flight
attendants, and defibrillators, as well as all the medications required by t h e advanced cardiac life support
(ACLS) protocol, should be available during flight.
4. Follow the level of anticoagulation using the
International Normalized Ratio.
Summary
1. Risk of high altitude pulmonary edema
a) Prevention
i) gradual ascent and limited physical exertion at
high altitude
ii) acetazolamide 250 mg p.0. q. 8-12 hours, starting
24 hours before ascent or dexamethasone 4 mg
p.0. q. 6 hours starting 48 hours before ascent
and continued for 72 hours at high altitude
b) Treatment
i) return to lower altitudes, administration of
oxygen, steroids, acetazolamide,diuretics, and/or
nifedipine
2. Immediate administration of aspirin, preferably chewed,
and sublingual nitroglycerin with any episode of chest
pain suggestive of angina. Seek medical attention
immediately.
5 Carry a copy of most recent electrocardiogram.
6 Avoid maintaining the same position for long hours,
ensuring adequate hydration, and consider administration
of aspirin to prevent deep venous thrombosis of the lower
extremities and pulmonary emboli, particularly in patients
with CHF who are considered to be at high risk.
7 Be aware of potential adverse cardiovascular responses in
hot climates (dehydration-induced hypovolernia and
postural hypotension) and possible exacerbation of angina
in cold weather.
8. Patients with implanted electronic devices (ix.,
pacemakers, defibrillators) must
I) be able to contact personnel for specific medlcal
services, if needed
ii) have regular check-ups of the device during travel
iii) be aware of potential effects on the device during
personal search with magnets from airport
security (search should be avoided in subjects
with CPI defibrillator models #1600,1550,
1555, and 1625).
9. Fully equipped medical kits with all medications required
by the ACLS protocol and external defibrillators should
be available during flight. Basic and advanced cardiac life
support training to at least one crew member should be
mandated by all airlines.
in a minority of patients, it has been found that ischemia
develops at a lower rate-pressure product at cold temperatures, implying that t h e ischemic threshold was
reduced." T h e exact mechanism for this phenomenon
remains unclear; however, cold-induced coronary vasoconstriction or absence of normal coronary vasodilatory
Cardiovascular-related events can b e prevented in
healthy subjects and in patients with existing heart disease while traveling. Physicians who evaluate patients prior
to their travel should be aware of specific recomniendations that can reduce the incidence of cardiovascular
events during travel (Table 1).Sometimes, simple preventive measures can be followed by the patients on
their own. Enhancement of t h e equipment available for
managing medical emergencies during travel is also very
important, as this has been taken i n t o consideration
already by some travel companies.As previous investigators
have suggested,18we strongly believe that such a systematic
approach will have a significant impact on reducing the
cardiovascular risk during travel a m o n g healthy people
and in patients with heart diseases.
Acknowledgment
The authors wish t o thank Ms. Magda Cedillo for
her assistance in preparation of this manuscript.
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