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document
Acute effects of caffeine ingestion on signal-averaged electrocardiograms . BACKGROUND Although moderate caffeine ingestion has not been shown to be arrhythmogenic , caffeine toxicity can cause severe cardiac arrhythmias , including atrial fibrillation and ventricular tachycardia . Atrial fibrillation and ventricular tachycardia have been associated with prolongation of P-wave and QRS complex durations on signal-averaged electrocardiograms . This study investigated acute effects of caffeine ingestion on signal-averaged P-wave and QRS complexes . METHODS AND RESULTS Signal-averaged electrocardiograms were obtained from 12 normal subjects ( 6 men , 6 women ; ages 21 to 26 years ) before and after ingestion of caffeine ( 5 mg/kg body weight ) or placebo in a randomized , double-blind , crossover fashion . Electrocardiograms for signal averaging were recorded from electrodes left in a constant location . After bandpass filtering ( 30 to 300 Hz ) and amplification , signals were sampled over 7.2 minutes at 2000 Hz . Signal-averaged P-wave and QRS complex durations did not significantly change after placebo ingestion . After caffeine ingestion QRS duration prolonged in 9 of 11 subjects at 90 minutes ( mean +/- SEM = 0.8+/-0.3 ms , P < .02 ) and in 8 of 9 after 3 hours ( 1.1+/-0.2 ms , P < .001 ) . No significant change in P-wave duration or heart rate was found after caffeine ingestion at any test interval . Average caffeine level in saliva 90 minutes after ingestion was 6.6+/-1.6 ( SD ) microg/dL . CONCLUSIONS Although probably not arrhythmogenic in normal subjects , moderate caffeine ingestion does produce a small but statistically significant prolongation of signal-averaged QRS complexes . Further prolongation caused by excessive caffeine intake may be a factor in the genesis of arrhythmias associated with caffeine toxicity .
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Intervention_Pharmacological
caffeine ingestion
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Intervention_Pharmacological
caffeine
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Intervention_Control
placebo
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Outcome_Physical
signal-averaged electrocardiograms .
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Outcome_Physical
prolongation of P-wave and QRS complex durations on signal-averaged electrocardiograms .
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Outcome_Physical
signal-averaged P-wave
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Outcome_Physical
Signal-averaged P-wave and QRS complex durations
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Outcome_Physical
P-wave duration or heart rate
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Outcome_Physical
Average caffeine level in saliva