Study Preview
Study Title and Description
Black tea increases coronary flow velocity reserve in healthy male subjects.
Key Questions Addressed
| 1 | For [population], is caffeine intake above [exposure dose], compared to intakes [exposure dose] or less, associated with adverse effects on cardiovascular outcomes? |
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Primary Publication Information
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| Title | Black tea increases coronary flow velocity reserve in healthy male subjects. |
| Author | K Hirata,K Shimada,H Watanabe,R Otsuka,K Tokai,M Yoshiyama,S Homma,J Yoshikawa, |
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| Year | 2004 |
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Secondary Publication Information
There are currently no secondary publications defined for this study.
Extraction Form: Cardiovascular Design
| Question... Follow Up | Answer | Follow-up Answer | |
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| What outcome is being evaluated in this paper? | Cardiovascular |
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| What is the objective of the study (as reported by the authors)? | The purpose of this study was to evaluate the effects of black tea on coronary flow velocity reserve (CFVR) using transthoracic Doppler echocardiography (TTDE). |
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| Provide a general description of the methods as reported by the authors. Information should be extracted based on relevance to the SR (i.e., caffeine related methods) | Study Population Ten male volunteers were enrolled in this study. Subjects were healthy medical students and physicians (mean age 26 +/- 3 years). All subjects were asymptomatic, normotensive, nondiabetic, and nonsmokers. They had no significant medical histories and no habits of increased tea, caffeine, red wine, or purple grape juice consumption. No subjects had taken any cholesterol-reducing agents or antioxidant vitamin supplements for the preceding 2 months. Study Design The study used a double-blind crossover design that compared the effect of black tea (group T) and a caffeine-containing control (group C) on coronary circulation. Volunteers were studied on 2 separate occasions 1 week apart after overnight fasting and abstinence from red wine, purple grape juice, tea, and other known sources of significant amounts of flavonoids for 24 hours before each test session. After baseline CFVR measurements were obtained, volunteers consumed 450 ml of a test beverage in random order (black tea or caffeine-containing control). Two hours after beverage consumption, a second set of measurements were taken. Black tea and caffeine drinks were formulated to have exactly the same color, taste, and flavor (provided by Unilever Bestfoods North America, Englewood Cliffs, New Jersey). The caffeine control contained 120 mg of caffeine (the same amount as delivered by the tea beverages). Coronary flow studies: Echocardiography was performed with the Acuson Sequoia 512 (Siemens AG Medical Solutions, Erlangen, Germany) with a frequency of 7.0 MHz. The ultrasound beam was transmitted toward the heart to visualize coronary blood flow in the left anterior descending coronary artery (LAD) by color Doppler echocardiography. We first recorded baseline spectral Doppler signals in the distal portion of the LAD over 5 cardiac cycles at end-expiration by TTDE. Intravenous adenosine triphosphate (ATP) was administered (140 ug/kg-min intravenously) for 2 minutes to record spectral Doppler signals during hyperemic conditions. All subjects had continuous heart rate and electrocardiographic monitoring. Blood pressure was recorded at baseline and every minute during ATP infusion. Each study was analyzed by 2 experienced investigators who were blinded to the other subject data. Measurements were performed off line by tracing the contour of the spectral Doppler signal using the computer incorporated in the ultrasound system. Mean diastolic velocities were measured at baseline and peak hyperemic conditions from the Doppler signal recordings. CFVR was defined as the ratio of hyperemic to basal mean diastolic velocity. CFVR measurement was performed before and 2 hours after tea consumption. The CFVR ratio was derived by dividing baseline CFVR by CFVR after beverage consumption. Statistical Analysis Data are presented as mean values +/- SDs. To compare the effects of ATP administration and treatment, we used 2-way, repeated-measures analysis of variance (ANOVA) for hemodynamic parameters, coronary flow velocity, and CFVR over ATP administration before and after treatment with post hoc Scheffe comparison. Paired t tests were used for directed comparisons of beverage intake effects in each group. We used 1-way ANOVA for CFVR ratio to compare the effects of beverage types. Statistical significance was accepted at p <0.05. |
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| How many outcome-specific endpoints are evaluated? | 3 |
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| What is the (or one of the) endpoint(s) evaluated? (Each endpoint listed separately) | Blood pressure (SBP and DBP) |
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| List additional health endpoints (separately). 2 | Heart rate |
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| List additional health endpoints (separately).3 | Coronary Flow Velocity Reserve (CFVR) as estimated from mean diastolic velocity |
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| List additional health endpoints (separately).4 |
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| List additional health endpoints (separately).5 |
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| List additional health endpoints (separately).6 |
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| Clinical, physiological, other | Physiological |
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| What is the study design? | Controlled Trial |
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| Randomized or Non-Randomized? | RCT |
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| What were the diagnostics or methods used to measure the outcome? | Objective |
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| Optional: Name of Method or short description | Echocardiography was performed with the Acuson Sequoia 512 (Siemens AG Medical Solutions, Erlangen, Germany) with a frequency of 7.0 MHz. The ultrasound beam was transmitted toward the heart to visualize coronary blood flow in the left anterior descending coronary artery (LAD) by color Doppler echocardiography. |
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| Caffeine (general) | Caffeine (general) |
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| Coffee, Chocolate, energy drink, gum, medicine/supplement, soda, tea, other? |
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| Measured or self reported? | Measured |
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| Children, adolescents, adults, or pregnant included? | Adults |
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| What was the reference, comparison, or control group(s)? (e.g. high vs low consumption, number of cups, etc.) | Subjects served as their own controls |
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| What were the listed confounders or modifying factors as stated by the authors? (e.g. multi-variable components of models. Copy from methods) | None |
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| What conflicts of interest were reported? | No information provided |
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| Refid | 15165919 |
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| What were the sources of funding? | No information provided |
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Results & Comparisons
No Results found.
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