CORRESPONDENCE: LETTER TO THE EDITOR
"One" Cup of Coffee and Nuclear SPECT to Go
Sripal Bangalore, MD, MHA,
Sanobar Parkar, MD, MPH and
Franz H. Messerli, MD*
* Hypertension Program, Division of Cardiology, Columbia University College of Physicians and Surgeons, St. Luke’s–Roosevelt Hospital Center, 1000 Tenth Avenue, Suite 3B-30, New York, New York 10025 (Email: fmesserli{at}chpnet.org).
In the provocative study published in JACC, Zoghbi et al. (1) discuss the effect of caffeine on ischemia detection by adenosine single-photon emission computed tomography (SPECT) and conclude: "One cup of coffee should not be a reason to cancel a scheduled adenosine study or to change to dobutamine, and the current guidelines need to be revised to improve laboratory throughput and patient comfort." One has to be very careful when interpreting these conclusions. The caffeine content of 1 cup of coffee can vary from 3 to 564.4 mg (Table 1) (2). Variations are not unusual even with the same brand: a study found that in a 16-oz Starbucks Breakfast Blend coffee, the caffeine content sampled from the same store varied almost 2-fold when measured for 6 consecutive days (range 299.5 to 564.4 mg) (3). The study by Zoghbi et al. (1) evaluated the effects of one 8-oz coffee 1 h prior to SPECT, and 60% of patients had caffeine levels <3 mg/dl. The caffeine plasma concentration reaches a peak in 45 min to 2 h (4). Zoghbi et al. (1) thus evaluated the effects of a fixed dose of caffeine at a fixed point of time after the dose on SPECT outcomes. Given the wide variation in the caffeine content of coffee that people consume, the varying time to peak, and the lack of data to demonstrate efficacy of adenosine SPECT at varying doses of caffeine, the study probably should be described as hypothesis generating and should be interpreted with caution.
Caffeine is the world’s most consumed drug, with over 50% of the population of America consuming it on a day-to-day basis (4). Studies have shown that caffeine induces an increase in mean arterial pressure of 6.1 ± 0.5 mm Hg (5). Nevertheless, the investigators do not comment on the hemodynamic effects of caffeine per se. Did the blood pressure increase 1 h after caffeine consumption? Was there an increase in heart rate 1 h after caffeine consumption compared with baseline? If there were none of the aforementioned hemodynamic changes, it is possible that the dose of caffeine for this group of patients might not have been sufficient enough to cause any hemodynamic changes and hence to interfere with the SPECT results?
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1. Zoghbi GJ, Htay T, Aqel R, Blackmon L, Heo J, Iskandrian AE. Effect of caffeine on ischemia detection by adenosine single-photon emission computed tomography perfusion imaging J Am Coll Cardiol 2006;47:2296-2302.[Abstract/Free Full Text]2. Barone JJ, Roberts HR. Caffeine consumption Food Chem Toxicol 1996;34:119-129.[CrossRef][Web of Science][Medline] 3. McCusker RR, Goldberger BA, Cone EJ. Caffeine content of specialty coffees J Anal Toxicol 2003;27:520-522.[Web of Science][Medline] 4. Ellenhorn MJ, Barceloux DG. Medical Toxicology, Diagnosis and Treatment of Human Poisoning. New York, NY: Elsevier; 1988. pp. 508-514. 5. Smits P, Straatman C, Pijpers E, Thien T. Dose-dependent inhibition of the hemodynamic response to dipyridamole by caffeine Clin Pharmacol Ther 1991;50:529-537.[Web of Science][Medline]
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