ted heart rate among subjects undergoing pharmacological stress testing with regadenoson is not clear. We hypothesized that chronic caffeine intake with only 1224 hours cessation prior to regadenoson stress testing according to drug labeling recommendation, affects maximal heart rate and blood pressure response as compared to non-caffeine consumption or more prolonged interruption. The aim of the current study is to assess the effect of habitual caffeine consumption on blood pressure, heart rate, percentage of predicted heart rate and percentage change in heart rate among subjects undergoing vasodilator stress testing with regadenoson. Methods Patients The study protocol was approved by the Indiana University institutional review board for research. Written informed consent was obtained from all subjects. Subjects referred for regadenoson stress testing were enrolled. Patients with combined exercise and regadenoson stress testing were excluded from analysis. As per the protocol of our institution, all patients were asked to not consume caffeinated beverages or xanthine containing foods for at least 12 PubMed ID:http://www.ncbi.nlm.nih.gov/pubmed/19736355 hours prior to study. Moreover, all patients were asked to take their routine daily medications. Baseline demographic data and medical comorbidities were collected on all subjects. Information on amount, frequency, and last exposure to caffeine, chocolate, and caffeinated soft drinks 2/9 Caffeine and Regadenoson Response were collected prospectively prior to performance of cardiac stress test. Caffeine exposure was classified according to none recently, last exposure of at least one cup of coffee 1224 hours prior to regadenoson stress test, and >24 hours prior to stress test. Consumption of one cup of black or green tea was considered equal to one cup of coffee, and subjects who consumed tea were included in the coffee consumption group for analysis. Subjects’ heart rate, and blood pressure were recorded at baseline instantaneously before administration of regadenoson. Subjects remained in a supine position throughout the test. Change in heart rate during the stress test was calculated by subtracting resting from peak heart rate recorded within 5 minutes after administration of regadenoson. Change in Chebulinic acid systolic blood pressure was calculated by subtracting resting from peak systolic blood pressure recorded within 5 minutes after administration of regadenoson. Maximal predicted heart rate was calculated using 220-age and percent maximal predicted heart rate was calculated by peakHR over MHR and multiplying by 100 100). Percent change in heart rate was calculated by changeHR over restingHR and multiplying by 100. Incidence of patient reported side effects were prospectively recorded. Non-coffee drinkers were compared to subjects who had consumed coffee within 12 to PubMed ID:http://www.ncbi.nlm.nih.gov/pubmed/19736794 24 hours or more than 24 hours prior to regadenoson administration. Statistical Analysis Baseline demographic and clinical variables are descriptively summarized. Continuous variables are expressed as mean SD. Categorical data are presented as percent frequency. Unpaired two-sided Student’s t-test was used to compare normally distributed continuous data between two groups. One-way analysis of variance test and post hoc Tukey comparisons were used to determine difference between different groups based on coffee consumption. Categorical variables were compared using the 2 test and continuous variables were computed using student t test. Statistical significance was defined as p-value <