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352 Abstracts

Comments: As this was a single-center study at a Universityospital in France, the results may not reflect the experiencesf a general American population. However, the results of thistudy strongly suggest malignancy (and undiagnosed malig-ancy) as the leading cause of emergent pericardial effusion.mergency physicians must include neoplastic effusion in theifferential diagnosis of all known cancer patients who presento the Emergency Department with chest pain, shortness ofreath, or a related complaint. Similarly, undiagnosed malig-ancy should surface very high on the list of causes of newlyiagnosed pericardial tamponade.

HIGH ALTITUDE DYSRHYTHMIAS. Woods DR,llen S, Betts TR, et al. Cardiology 2008;111:239–46.

This study aimed to investigate the nature and cause ofalpitations occurring at high altitude. Implantable loop record-rs (ILR) were inserted into 9 healthy male volunteers. Theean age of the subjects was 29.8 years. They all had a normal

ardiovascular examination including 12-lead electrocardio-ram and 2D cardiac echocardiogram, and they all achieved ateast stage 5 of the Bruce protocol without abnormality beforeeginning the study. The subjects flew to Kathmandu (1250 m),hen to Lukla (2800 m), where they began an identical ascentnd descent profile to high altitude. The ILR was activated withny episode of palpitations during rest, activity, or sleep. Ar-erial oxygen saturation was also assessed. The activations ofhe ILR were examined by three independent electrophysiolo-ists. The authors found that, above 5000 m, all subjectseported palpitations with exercise, and two had symptomaticpisodes at rest. During strenuous exercise, atrial flutter with:1 conduction was observed in 1 subject. In another, sinusachycardia and sinus dysrhythmia was observed during exer-ise. In a third, repolarization changes were seen with dramaticT-segment depression. Another subject had non-conducted-waves. All of these episodes were during times of relativeypoxemia. The authors conclude that significant dysrhythmiasccur at high altitude and they suggest that this study may helpxplain the increased risk of sudden cardiac death at highltitude, especially in elderly patients and those with underlyingardiac disease.

[Cameron D. Klug, MD,

Denver Health Medical Center, Denver, CO]

Comment: This study provides interesting insight into the

lectrocardiographic changes that can occur in healthy individ- a

als undergoing physical exertion at high altitude. However, its difficult to correlate the results of this study, which foundtrial dysrhythmias in young, healthy subjects, with the suddenardiac death from ventricular dysrhythmias seen in olderndividuals at high altitude. Further research into dysrhythmiast high altitude is warranted, especially in older patients withre-existing cardiac disease.

HOME USE OF AUTOMATED EXTERNAL DEFI-RILLATORS FOR SUDDEN CARDIAC ARREST.ardy GH, Lee KL, Mark DB, et al. N Engl J Med 2008;358:793–804.

This multi-center international study evaluated the homese of automated external defibrillators (AEDs) in patients atigh risk for sudden cardiac arrest. A total of 7001 patientsere used in this study. Patients studied had a documentedrevious anterior-wall myocardial infarction but were not can-idates for implantable cardioverter-defibrillator therapy, basedn published guidelines. The patients were divided into tworoups of actions after sudden cardiac arrest in the home: a) theontrol group of calling Emergency Medical Services (EMS)nd beginning cardiopulmonary resuscitation (CPR) or b) thetudy group of using an AED, followed by calling EMS andnitiating CPR. The primary outcome studied was death by anyause during a median follow-up time of 37.3 months. In total,50 patients died during this study: 228 of 3506 (6.5%) patientsn the control group and 222 of 3495 (6.4%) patients in thetudy group. Of the 450 deaths, 160 (35.6%) were secondary toardiac arrest from tachydysrhythmia. Only 32 patients re-eived the used of an AED, with 14 patients receiving anppropriate shock and 4 surviving to hospital discharge. Theuthors concluded that the home use of AEDs in patients atigh risk for future cardiac arrest does not significantly im-rove survival when compared to traditional resuscitativeeasures.

[Elijah Edwards, MD,

Denver Health Medical Center, Denver, CO]

Comment: Although this study showed no significant sur-ival rate with the home use of AEDs, it demonstrated thatEDs can be used safely within the home. With proper training

nd public education, there may be a future role for moreidespread use of AEDs as the technology becomes cheaper

nd more readily available.