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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. References Hargarten SW, Baker TI>, Guptill K. Overseas fatalities of United States citizen travelers: an analysis of deaths rrlatrd to international travel. Ann Emerg Med 1991;20:622-626. Cummins RO, Schubach JA. Frequency and types of medical emergencies among commercial air travelers. JAMA 1989;261:1295-1299. Speizer C, Rennie CJ 111, Breton H. Prevalence of in-flight medical emergencies on commercial airlines. Ann Emerg Med 1989;18:26-29. J o u r n a l of Travel Medicine, Volume 3 , Number 4 230 4. Cunimins RO, Chapman PJC, Chamberlain DA, et al. In flight deaths during commercial air travel: how big is the problem? JAMA 1988;259:1983-1988. 5. Cottrell JJ, Callaghan JT, Kohn GM, et al. In-flight medical emergencies: one year of experience with the enhanced medical kit. JAMA 1989;262:1653-1656. 6. Bia FJ, Barry M. Special health considerations for travelers. Med Clin North Am 1992;76:1295-1312. 7. Tso E. High altitude illnesc. Emerg Med Clin North Am 1992;10(2):231-247. a. Naeije R, Melot C, Lejeune P. Hypoxic pulmonary vasoconstriction and high altitude pulmonary edema. Am Rev Resp Dis 1986;134:332-333. 9. Kawashima A, Kubo K, Kobayashi T, et al. Hemodynamic responses to acute hypoxia, hypobaria and exercise in subjects susceptible to high altitude pulmonary edema. J Appl Physiol 1989;67:1982-1989. 10. Ellsworth AJ, Larson EB, Strickland D.A randomized trial of dexamethasone and acetazolamide for acute mountain sickness prophylaxis.Am J Med 1987;83:1024-1030. 11. Zell SC, Goodman PH. Acetazolamide and dexamethasone in the prevention of acute mountain sickness. West J Med 1988;148:541-545. 12 Cruickshank JM, Gorlin R,Jennett B.Air travel and thrombotic episodes: the economy class syndrome. Lancet 1988;2:497-498. 13 Fiore L, Brophy M, Lopez A, et al.The bleeding time response to aspirin. Am J Clin Path 1990;94:292-296. 14 Amrein P, Ellman L, HarrisW.Aspiriti-induced prolongation of bleeding time and perioperative blood loss. JAMA 1981;245:1825-1 828. 15 Epstein SE, Stampfer M, Beiser GD, et al. Effect of a reduction in environmental temperature on the circulatory response to exercise in man. Implications concerning angina pectoris. N Engl J Med 1969;280:7-11. 16 Juneau M, Johnstone M, Dempsey DD. Exercise-induced myocardial ischemia in cold environment. Effect of antianginal medication. Circulation 1989;79:1015-1020. 17 Raizner AE, Chahine RA, Ishimori T, et al. Provocation of coronary artery spasm by the cold pressure test. Circulation 1980;67:309-3 15. 18. Gong H Jr, Lee Mark JA, Cowan MN. Pre-flight medical screenings of patients: analysis of health and flight characteristics. Chest 1993;104:788-794. Cerebral cysticercosis in a Mexican farm worker. Submitted by J.S. Keystone, M.D.