Di Rocco et al. Journal of Medical Case Reports 2011, 5:18 http://www.jmedicalcasereports.com/content/5/1/18 resolved when he discontinued his excessive caffeine consumption [7]. Caffeine is a natural stimulant found in tea leaves, cof- fee beans, and cacao, and is one of the most popular psychoactive substances used today. Caffeine causes cen- tral and peripheral nervous system stimulation through antagonism of adenosine receptors and also has dopami- nergic properties, which lend to its addictive potential [8]. The half-life of caffeine in a normal healthy adult is estimated to be from 2.5 to 10 hours, depending on the individual. Long-term consumption of caffeine or con- sumption of large amounts of caffeine will prolong its half-life [9,10]. The US Food and Drug Administration deems, “caffeine is generally recognized as safe when used in cola-type beverages up to a level of 0.02 per- cent” [11]. The population as a whole has variable sensi- tivity to the stimulant effects of caffeine; one’s tolerance and dependence on caffeine seem to be somewhat heri- table and may be linked to genetic polymorphisms [8]. The physiologic and psychological effects of caffeine have been studied in adults but have not been systema- tically analyzed in children [8]. Energy drinks and highly caffeinated drinks comprise some of the fastest-growing products of the beverage industry, often targeting teenagers and young adults [8,12]. This case series describes the possible association between the consumption of highly caffeinated drinks and the development of cardiac arrhythmias, specifically Page 2 of 6 atrial fibrillation, in the adolescent population. We report two cases of atrial fibrillation in healthy adoles- cent boys after the consumption of energy drinks. Case presentation Case 1 A 14-year-old Caucasian boy with no significant past medical history presented with persistent “heart flutter- ing” two hours after a running race. He denied recent illness and denied drug ingestion, but reported drinking an unknown quantity of a highly caffeinated drink the day before. He also reported drinking a Red Bull™ energy drink five days before admission and feeling the same fluttering sensation. His physical examination revealed an irregularly irregular heart rate at approxi- mately 130 beats per minute with a 1/6 vibratory systo- lic ejection murmur at the left lower sternal border. Thyroid-function tests and serum calcium were normal. His electrocardiogram (ECG) showed narrow-complex tachycardia with atrial fibrillation and occasional atrial flutter (Figure 1). Cardiac ECG revealed a structurally normal heart without thrombus. He was treated with one dose of digoxin as a partial load at 7.5 μg/kg and quickly converted to normal sinus rhythm with a heart rate of 70 to 80 beats per minute (Figure 2). On follow- up examination in cardiology clinic one month later, the patient had a normal cardiac examination, a normal ECG, and no further symptoms of arrhythmia. Figure 1 Electrocardiogram showing narrow-complex tachycardia with atrial fibrillation and occasional atrial flutter with irregularly irregular ventricular response. Heart rate, 122 beats per minute; QRS, 88 ms; QTc, 433 ms.