title: A Rapid Method to Evaluate Cardiac Repolarization Changes: The Effect of Two Coffee Strengths on the QT Interval.
abstract: OBJECTIVE
  To assess the effect of coffee on ventricular repolarization as measured by an electrocardiogram.
  
  
  METHODS
  Fifty-four healthy volunteers (34 males and 20 females, age 23 ± 5 years) received 1 cup of coffee (caffeine content 120 mg) and 11 participants received 2 cups. Blood pressure and heart rate were measured prior to coffee and every hour thereafter for 5 h. A 12-lead digital Holter recorded continuously, and RR, QT, and QTc intervals were obtained every 30 min.
  
  
  RESULTS
  Following coffee, RR increased from 802 ± 102 to 873 ± 126 ms (p = 0.001), QT increased from 359 ± 26 to 367 ± 27 ms at 1.5 h (p = 0.047), and QTc decreased from 387 ± 21 to 381 ± 23 ms at 30 min (p = 0.001), with no changes noted at other time points. Caffeine users and caffeine-naive subjects did not differ in QTc effects (p = 0.971). Females had longer QTc at each time point than males (p = 0.037), but neither had QTc prolongation following coffee. The heart rate decreased from 73 ± 9 to 69 ± 11 bpm at 1 h (p = 0.018), and no significant changes in blood pressure were noted. The effects of 1 or 2 cups of coffee did not differ in terms of QTc (p = 0.663), heart rate (p = 0.161), diastolic (p = 0.250), or systolic blood pressure (p = 0.168).
  
  
  CONCLUSIONS
  Neither 1 nor 2 cups of coffee increased ventricular repolarization.
authors.affiliation: American Institute of Therapeutics, Lake Bluff, Ill., USA.
authors.forename: Janos
authors.initials: J
authors.lastname: Molnar
authors.forename: John C
authors.initials: JC
authors.lastname: Somberg
mesh_terms: D000293:Adolescent; D000328:Adult; D001794:Blood Pressure / Q000187:drug effects*; D002110:Caffeine / Q000493:pharmacokinetics*; D004562:Electrocardiography / Q000706:statistics & numerical data*; D015716:Electrocardiography, Ambulatory; D005260:Female; D064368:Healthy Volunteers; D006339:Heart Rate / Q000187:drug effects*; D006801:Humans; D008297:Male; D012727:Sex Characteristics; D055815:Young Adult
chemical_list: D002110:Caffeine