Journal of the American College of Nutrition, Vol. 25, No. 6, 472-479 (2006)
Published by the American College of Nutrition
Tea Consumption and Infarct-Related Ventricular Arrhythmias: The Determinants of Myocardial Infarction Onset Study
Kenneth J. Mukamal, MD, MPH, MA,
Marissa Alert,
Malcolm Maclure, ScD,
James E. Muller, MD and
Murray A. Mittleman, MD, DrPH
Divisions of General Medicine and Primary Care (K.J.M., M.A.)
Cardiology (M.A.M.)
Beth Israel Deaconess Medical Center, Department of Epidemiology (M.M., M.A.M.)
Harvard School of Public Health, Division of Cardiology (J.E.M.), Massachusetts General Hospital, Boston, Massachusetts
Address reprint requests to: Kenneth J. Mukamal, MD, MPH, MA, Beth Israel Deaconess Medical Center, Division of General Medicine and Primary Care Research Program, 1309 Beacon Street, 2nd Floor, Brookline, MA 02446. E-mail: kmukamal{at}bidmc.harvard.edu
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ABSTRACT
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Background: Tea consumption is associated with lower post-infarct mortality among patients with acute myocardial infarction. We previously found preliminary evidence that tea consumption may also be associated with lower risk of infarct-related ventricular arrhythmias.
Methods: Between 1989 and 1996, 3882 subjects with AMI were enrolled in the two phases of the Determinants of Myocardial Infarction Onset Study a median of four days after admission. Trained interviewers assessed self-reported usual tea and coffee consumption during the year prior to infarction with a standardized questionnaire. We examined the prevalence of ventricular arrhythmias in the two phases of the study separately and together.
Results: Among the 1912 patients with complete information in the first phase, the prevalence of ventricular arrhythmias was 16% among abstainers from tea, 11% among moderate tea drinkers (<14 cups per week), and 14% among heavier tea drinkers (
14 cups per week) (p homogeneity = 0.03). Among the 1791 patients with comparable information in the second phase, the corresponding prevalence rates were 11%, 8%, and 8%, respectively (p = 0.06). When the phases were combined, the adjusted odds ratios for VA were 0.7 (95% confidence interval, 0.6–0.9) among moderate tea drinkers and 0.9 (95% confidence interval, 0.7–1.2) among heavier tea drinkers. The findings were of similar direction for both ventricular tachycardia and fibrillation. In contrast, there was higher risk of VA with increasing coffee intake (odds ratio for >14 cups per week 1.3; 95% confidence interval, 1.0–1.7; p trend 0.02).
Conclusions: Moderate tea intake is associated with a lower prevalence, and higher coffee intake with a slightly higher prevalence, of ventricular arrhythmias among patients hospitalized with acute myocardial infarction. If the association with tea intake is confirmed, it may suggest new approaches to prevention of ischemia-related arrhythmias.
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INTRODUCTION
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The effects of tea on health have been widely studied, in part because tea contains flavonoids and other antioxidant components. Epidemiological evidence linking tea or flavonoid consumption with coronary or total mortality is conflicting [1–5] although these studies were generally done in patients free of heart disease at baseline. Few data exist regarding the effect of tea consumption on patients with acute myocardial infarction (AMI). Among men with prevalent cardiovascular disease in the Health Professionals Follow-up Study, flavonoid intake was associated with lower coronary mortality [6], but this finding was not statistically significant. In an analysis of the first phase of the Determinants of Myocardial Infarction Onset Study (The Onset Study), we previously found that tea intake was associated with lower subsequent mortality among patients hospitalized with AMI [7], while coffee intake had no such association [8].
In unadjusted analyses of the first phase of the Onset Study, we found a statistically significant but unexpected relationship between usual tea consumption and risk of ventricular arrhythmias (VA), with a lower prevalence among moderate tea drinkers [7]. Because VA were not the focus of our previous analyses, no adjusted analyses were performed. We know of no previous data regarding tea consumption and risk of VA related to AMI.
To explore the hypothesis that tea consumption, but not coffee consumption, is inversely associated with VA that complicate AMI, we studied patients enrolled in the two phases of the Onset Study. The Onset Study is a prospective, multicenter study that included chart reviews and face-to-face interviews with hospitalized patients with confirmed AMI. First, we assessed whether the univariate relationship seen in the first phase of the Onset Study persisted following adjustment for potentially confounding factors. Second, we independently assessed this association among patients enrolled in the second phase of the study to validate this finding. Finally, we conducted a pooled analysis of both phases.
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MATERIALS AND METHODS
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Patient Population and Data Collection
The first phase of the Onset Study was conducted in 45 community hospitals and tertiary care medical centers in the United States between August 1989 and September 1994. In the second phase that lasted through September 1996, the Onset Study was expanded to 64 medical centers. Of the 3882 enrolled participants, we excluded 116 with missing information on tea or coffee and 63 missing other information, leaving 1912 eligible participants from the first phase and 1791 participants from the second phase.
Trained research interviewers identified eligible patients by reviewing coronary care unit admission logs and patient charts. For inclusion, patients were required to have a creatine kinase level above the upper limit of normal for the clinical laboratory at each center, positive MB isoenzymes, an identifiable onset of pain or other symptoms typical of AMI, and the ability to complete a structured interview. The institutional review board of each center approved the protocol, and informed consent was obtained from each patient.
Interviewers used a structured data abstraction and questionnaire form. Participants were asked their usual frequency of consumption of caffeinated tea and coffee over the last year individually. As in previous analyses, we categorized usual tea consumption as none, <14/week (moderate use), or 14/week (heavier use) [7] and usual coffee consumption as none, 
7/week, >7 to 14/week, or >14/week [8]. We did not determine the consumption of decaffeinated tea or coffee.
Other information collected from each interview and chart review included patient age, gender, medical history, and medication use (both prescription and non-prescription).
For all patients, interviewers recorded arrhythmic complications of AMI, including ventricular tachycardia (VT) and ventricular fibrillation (VF), based upon diagnoses recorded by the treating clinicians in the medical record. In validation analyses, prevalence of VA during hospitalization was strongly associated with receipt of thrombolytic therapy, white race, congestive heart failure during hospitalization, and previous myocardial infarction, as expected from previous studies [9,10].
Assessment of Covariates
Patients were asked their usual frequency of heavy physical exertion (leisure-time and work-related), using a validated instrument [11]. Consistent with previous Onset Study analyses [11], we categorized the usual frequency of exertion as exertion 6 MET in the following frequencies: <1 time/week, 1–4 times/week, or >4 times/week. We defined current aspirin use as the reported use of any aspirin or aspirin-containing product in the four days prior to the index myocardial infarction, based on previous Onset Study analyses and the duration of its physiologic effect [12]. We derived body-mass index based upon self-reported height and weight.
Statistical Analysis
We performed univariate comparisons of continuous and binary variables using ANOVA and 
2 or Fisher exact tests, respectively. We used logistic regression to adjust for differences among participants in different categories of tea intake. These included age and body-mass index (as linear and quadratic variables), sex, current smoking, former smoking, usual physical exertion (in three categories), educational attainment (in three categories), usual coffee intake (in four categories), use of cardiac medications (digoxin, diuretics, aspirin, ß-adrenergic antagonists, calcium-channel blockers, and angiotensin-converting-enzyme inhibitors), thrombolytic therapy, and previous history of AMI, hypertension, and diabetes. In sensitivity analyses, we added the complication of congestive heart failure occurring during hospitalization as a covariate. We present odds ratios from contingency analyses and logistic regression models with their 95% confidence intervals (CI). Because we anticipated a non-linear relationship with tea from previous analyses, we tested results of regression models for homogeneity with likelihood ratio tests. For coffee, we performed tests of trend by treating the midpoints of coffee consumption categories as a continuous variable. To explore non-linear relationships further, we tested fractional polynomials with linear, squared, cubic, and square-root terms for tea consumption [13]. We tested for a global interaction between coffee and tea intake using nested models with and without all interaction terms.
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RESULTS
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The characteristics of the patients in the first phase of the Onset Study in relationship to tea [7] and coffee [8] consumption have been previously reported. Characteristics from the second phase according to tea consumption are summarized in Table 1. Patients who drank more tea were more likely to be older and female in both phases, but no other demographic characteristics differed notably with tea intake. Coffee and tea consumption were inversely correlated in both the first (Spearman r –0.08; p < 0.001) and second (r –0.10; p < 0.001) phases.
A total of 445 patients developed VA during hospitalization, including 370 with VT and 87 with VF. The prevalence of VT and VA was higher in the first phase than in the second (p < 0.001 for both), but the prevalence of VF was identical in both phases.
Tea Intake and VA
Table 2 shows odds ratios for VA according to tea intake in both phases of the Onset Study. As previously described, the unadjusted prevalence of VA was lower among moderate drinkers than nondrinkers in the first phase [7]. This finding was confirmed in multivariate analyses, with approximately 30% lower odds of VA even after adjusting for clinical and sociodemographic features; the prevalence among heavier tea drinkers was intermediate.
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Table 2. Odds Ratios and 95% Confidence Intervals for Prevalence of Ventricular Arrhythmias during Hospitalization according to Tea Intake among 3703 Onset Study Patients
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We next attempted to replicate this finding independently in the second phase of the Onset Study. Although the prevalence of VT was lower than in the first phase, the pattern of lower prevalence among moderate tea drinkers was similar. In this case, the age- and sex-adjusted prevalence of VA among both moderate and heavy tea drinkers was approximately 30% lower than among nondrinkers, with some attenuation of the effect among heavy tea drinkers after multivariate adjustment.
Because the association of tea intake with prevalence of VA was similar in both phases, we performed pooled analyses on the combined dataset for additional power (Table 3). The pattern of a lower prevalence of VA among moderate tea drinkers tended to be similar among men and women, among patients who did and did not receive thrombolytic therapy, at coffee intake above and below the median, and for both VT and VF. Results for heavier tea drinkers were more variable and not statistically significant. In a comparison of abstainers from tea with all tea drinkers together, the odds ratio among tea drinkers was 0.8 (95% confidence interval, 0.6–0.9).
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Table 3. Multivariate-Adjusted Odds Ratios and 95% Confidence Intervals for Prevalence of Ventricular Arrhythmias during Hospitalization according to Tea Intake among 3703 Patients Enrolled in both Phases of the Onset Study
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We performed additional sensitivity analyses on the combined dataset to ensure the robustness of our findings. These results were unchanged by further adjustment for congestive heart failure occurring during hospitalization. Smaller stepwise models (with entry and stay criteria of 0.20) also yielded identical results. In exploratory models using fractional polynomials that did not rely on our prespecified categories of tea intake, the prevalence of VA was lowest with intake of 4–5 cups of tea per week and reached that of nondrinkers at 28–29 drinks per week (Fig. 1). Compared with a simple linear model, addition of squared and square-root terms tended to improve model fit (p = 0.08), providing further evidence for a non-linear relationship between tea intake and prevalence of VA.
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Fig. 1. Adjusted odds ratios and 95% confidence intervals for ventricular arrhythmias according to usual tea intake among Onset Study participants. Tea intake modeled with linear, squared, and square-root terms. Odds ratios adjusted for age, sex, body-mass index, smoking, physical exertion, thrombolytic therapy, cardiac medications, previous history of myocardial infarction, hypertension, and diabetes, and coffee intake.
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Coffee Intake and VA
In contrast to the association with tea consumption, there was a modest, positive relationship between coffee consumption and prevalence of VA. The odds ratios for VA in the combined dataset relative to abstainers from coffee were 0.9 (95% confidence interval, 0.7–1.2) for 7 cups per week, 1.1 (95% confidence interval, 0.8–1.6) for >7 to 14 cups per week, and 1.3 (95% confidence interval, 1.0–1.7) for >14 cups per week (p trend 0.02). These results did not change with exclusion of tea consumption from our models, nor with adjustment for age and sex alone. The trend toward higher risk among the heaviest coffee drinkers was similar in the first (odds ratio 1.2; 95% confidence interval, 0.8–1.7) and second (odds ratio 1.3; 95% confidence interval, 0.8–2.1) phases of the Onset Study. When categorized further, the odds ratios were 1.3 (95% confidence interval, 0.9–1.8) for consumers of >14 to 21 cups of coffee per week, 1.4 (95% confidence interval, 1.0–2.0) for >21 to 42 cups per week, and 1.0 (95% confidence interval, 0.6–1.5) for >42 cups per week.
Fig. 2 shows the joint associations of coffee and tea intake with risk of VA, with a single reference category of abstainers from tea who drank >7 cups of coffee per week. For all levels of tea intake, the risk of VA was lower among consumers of smaller amounts of coffee. Likewise, for both levels of coffee intake, there was a U-shaped relationship of tea intake with risk of VA (p interaction 0.65).
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Fig. 2. Adjusted odds ratios and 95% confidence intervals for ventricular arrhythmias according to usual coffee and tea intake among Onset Study participants. The reference category was participants who abstained from tea and drank >7 cups of coffee per week. Odds ratios adjusted for age, sex, body-mass index, smoking, physical exertion, thrombolytic therapy, cardiac medications, and previous history of myocardial infarction, hypertension, and diabetes.
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DISCUSSION
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In analyses of early survivors of AMI, moderate tea consumption was inversely associated with prevalence of VA complicating AMI. This relationship was robust in both men and women and changed little by adjustment for demographic and clinical characteristics. In contrast, coffee consumption was associated with a modestly higher prevalence of VA.
We know of no previous studies to have specifically assessed tea or coffee intake and the risk of VA during the course of AMI. One review of short-term studies concluded that caffeine intake poses no substantial risk to patients with coronary heart disease [14], although it does appear to increase aortic stiffness in both experimental [15,16] and observational [17] studies. The American Heart Association currently suggests that patients hospitalized with AMI who routinely drink caffeinated beverages be allowed to consume up to 4 to 5 cups of caffeinated coffee per day [18].
There are plausible mechanisms to explain a lower prevalence of VA with greater tea intake. In epithelial cells cultured in vitro, prolonged but not acute incubation with (–)-epicatechin, a flavonoid present in tea, improves gap junctional intercellular communication, perhaps by promoting localization of connexin43 to the cell membrane [19]. Interestingly, prolonged incubation of rat hearts with catechins appears to minimize ischemia-reperfusion injury [20], an effect similar to that seen with other polyphenolic antioxidants that also suppress post-ischemic arrhythmia [21]. On the other hand, catechins inhibit catechol O-methyltransferase and can raise urinary norepinephrine levels, activities that might be expected to be proarrhythmic [22]. Indeed, limited epidemiological evidence suggests that tea intake may be associated with a greater prevalence of premature ventricular contractions on routine electrocardiography [23]. It is possible that the non-linear relationship suggested by our findings may reflect the balance of these antiarrhythmic and proarrhythmic activities.
Although most studies have not found proarrhythmic effects of caffeine [24–26] one crossover trial found that ingestion of 5 mg/kg of caffeine prolonged QRS duration [27] and men who consume 9 or more cups of coffee per day may have a modestly greater prevalence of premature ventricular contractions [23]. Our findings on coffee are roughly consistent with the latter findings, but less than 4% of Onset Study participants consumed more than 42 cups per week and hence we were unable to clarify possible proarrhythmic effects of very heavy coffee consumption in this study.
The lack of a direct dose-response relationship between tea consumption and infarct-related VA differs from most dietary factors, which typically have linear or threshold relationships with clinical outcomes [28], although alcohol intake may be one exception to this general rule [29]. Although we found limited evidence that the relationship of tea consumption with prevalence of VA was non-linear, determination of the true dose-response relationship is difficult. Relatively few participants consumed large amounts of tea, and the confidence intervals around the estimated effects in those patients were wide, leaving open the possibility of lower risk among heavier tea drinkers. A truly graded inverse relationship could also be misclassified as non-linear if participants report abstention from tea more accurately than their consumption of a specific, non-zero amount. In such a scenario, abstainers would be accurately classified, tending to produce an initial gradient in risk with increasing intake, but any dose-response relationship among tea drinkers would tend to be misclassified and blurred. Finally, tea may truly have a variety of effects that alter risk of VA in different directions; for example, among light tea drinkers, the benefit of catechins on intercellular communication might predominate, but this benefit might be attenuated by proarrhythmic effects of caffeine among heavier tea drinkers.
Our findings are subject to additional caveats. We may have over- or under-estimated the prevalence of VA by relying upon clinician-documented diagnoses, although any error in these estimates is unlikely to be related to the tea or coffee consumption of participants (and therefore unlikely to have biased our results). As in any observational study, unmeasured factors may have confounded our results, and dietary information was particularly limited in the Onset Study (although we previously found no association of alcohol intake with VA in this study [30]). Although we relied on self-reported tea and coffee consumption in this study, both of these foods generally appear to be reliably reported in epidemiological studies [31].
We asked participants only about caffeinated beverages, based upon prior hypotheses about cardiac effects of caffeine, and we did not determine the type of caffeinated tea that participants typically drank (although black, green, and oolong teas are all made from leaves of a single plant species). Thus, while caffeinated black tea represents the bulk of tea consumed in the United States and is likely to be the tea consumed by Onset Study participants, we cannot assess what effects decaffeinated tea may have, nor whether the type of tea alters its relationship with infarct-related VA. However, even black tea consumption has been shown to improve vascular endothelial function in randomized trials [32,33]. Likewise, we cannot determine whether caffeinated and decaffeinated coffees are equally associated with a higher prevalence of VA.
We did not have information on the specific timing of VA during hospitalization, nor any information on the specific diets provided to patients at each hospital. As a result, we cannot evaluate the possibility that the higher VA prevalence associated with heavy coffee intake reflects withdrawal from [34], rather than a direct effect of, caffeine consumption.
The Onset Study was conducted prior to the widespread use of primary angioplasty and coronary stenting, although progress in therapy to prevent VA has not paralleled improvements in revascularization and antithrombotic therapy [18]. Although our results were consistent in different time periods and among patients who did and did not receive thrombolytic agents, confirmation of our findings among patients who receive current AMI care is clearly needed.
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CONCLUSION
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In summary, moderate tea consumption was associated with a lower prevalence of VA during hospitalization among patients with AMI enrolled in the Onset Study, while coffee consumption was modestly associated with higher risk. This study provides a different dimension to the proposed cardioprotective effects of tea consumption, which include a lower risk of incident AMI in the general population [5] and a lower risk of mortality following AMI [7]. If confirmed, our results suggest that catechins and perhaps other polyphenolic antioxidants could play a role in preventing arrhythmic complications of AMI.
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ACKNOWLEDGMENTS
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This work was supported by grants HL41016 from the National Heart, Lung, and Blood Institute, Bethesda, MD, AT001899 from the National Center on Alternative and Complementary Medicine, Bethesda, MD, and 9630115N from the American Heart Association, Dallas, TX for the Onset Study. We thank Kristen MacDermott and Cindy Aiello for outstanding administrative assistance and oversight and Professor Roger Davis for statistical advice.
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FOOTNOTES
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Grant Support: HL41016 from the NHLBI, AT001899 from the NCCAM, and 9630115N from the American Heart Association.
Received August 16, 2005.
Accepted December 27, 2005.
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REFERENCES
|
|---|
- Hertog MG, Feskens EJ, Hollman PC, Katan MB, Kromhout D: Dietary antioxidant flavonoids and risk of coronary heart disease: The Zutphen Elderly Study.Lancet342
:1007
–1011,1993
.[Medline]
- Klatsky AL, Armstrong MA, Friedman GD: Coffee, tea, and mortality.Ann Epidemiol3
:375
–381,1993
.[Medline]
- Sesso HD, Gaziano JM, Buring JE, Hennekens CH: Coffee and tea intake and the risk of myocardial infarction.Am J Epidemiol149
:162
–167,1999
.[Abstract/Free Full Text]
- Geleijnse JM, Launer LJ,Van der Kuip DA, Hofman A, Witteman JC: Inverse association of tea and flavonoid intakes with incident myocardial infarction: the Rotterdam Study.Am J Clin Nutr75
:880
–886,2002
.[Abstract/Free Full Text]
- Peters U, Poole C, Arab L: Does tea affect cardiovascular disease? A meta-analysis.Am J Epidemiol154
:495
–503,2001
.[Abstract/Free Full Text]
- Rimm EB, Katan MB, Ascherio A, Stampfer MJ, Willett WC: Relation between intake of flavonoids and risk for coronary heart disease in male health professionals.Ann Intern Med125
:384
–389,1996
.[Abstract/Free Full Text]
- Mukamal KJ, Maclure M, Muller JE, Sherwood JB, Mittleman MA: Tea consumption and mortality after acute myocardial infarction.Circulation105
:2476
–2481,2002
.
- Mukamal KJ, Maclure M, Muller JE, Sherwood JB, Mittleman MA: Caffeinated coffee consumption and mortality after acute myocardial infarction.Am Heart J147
:999
–1004,2004
.[Medline]
- Russo AM, Hafley GE, Lee KL, Stamato NJ, Lehmann MH, Page RL, Kus T, Buxton AE: Racial differences in outcome in the Multicenter UnSustained Tachycardia Trial (MUSTT): a comparison of whites versus blacks.Circulation108
:67
–72,2003
.
- Wilcox RG, Eastgate J, Harrison E, Skene AM: Ventricular arrhythmias during treatment with alteplase (recombinant tissue plasminogen activator) in suspected acute myocardial infarction.Br Heart J65
:4
–8,1991
.[Abstract/Free Full Text]
- Mittleman MA, Maclure M, Tofler GH, Sherwood JB, Goldberg RJ, Muller JE: Triggering of acute myocardial infarction by heavy physical exertion. Protection against triggering by regular exertion. Determinants of Myocardial Infarction Onset Study Investigators.N Engl J Med329
:1677
–1683,1993
.[Abstract/Free Full Text]
- Mukamal KJ, Mittleman MA, Maclure M, Sherwood JB, Goldberg RJ, Muller JE: Recent aspirin use is associated with smaller myocardial infarct size and lower likelihood of Q-wave infarction.Am Heart J137
:1120
–1128,1999
.[Medline]
- Greenland S: Dose-response and trend analysis in epidemiology: alternatives to categorical analysis.Epidemiology6
:356
–365,1995
.[Medline]
- Lynn LA, Kissinger JF: Coronary precautions: should caffeine be restricted in patients after myocardial infarction?Heart Lung21
:365
–371,1992
.[Medline]
- Karatzis E, Papaioannou TG, Aznaouridis K, Karatzi K, Stamatelopoulos K, Zampelas A, Papamichael C, Lekakis J, Mavrikakis M: Acute effects of caffeine on blood pressure and wave reflections in healthy subjects: should we consider monitoring central blood pressure?Int J Cardiol98
:425
–430,2005
.[Medline]
- Mahmud A, Feely J: Acute effect of caffeine on arterial stiffness and aortic pressure waveform.Hypertension38
:227
–231,2001
.[Abstract/Free Full Text]
- Vlachopoulos C, Panagiotakos D, Ioakeimidis N, Dima I, Stefanadis C: Chronic coffee consumption has a detrimental effect on aortic stiffness and wave reflections.Am J Clin Nutr81
:1307
–1312,2005
.[Abstract/Free Full Text]
- Antman EM, Anbe DT, Armstrong PW, Bates ER, Green LA, Hand M, Hochman JS, Krumholz HM, Kushner FG, Lamas GA, Mullany CJ, Ornato JP, Pearle DL, Sloan MA,Smith SC, Jr., Alpert JS, Anderson JL, Faxon DP, Fuster V, Gibbons RJ, Gregoratos G, Halperin JL, Hiratzka LF, Hunt SA, Jacobs AK: ACC/AHA guidelines for the management of patients with ST-elevation myocardial infarction: a report of the American College of Cardiology/American Heart Association Task Force on Practice Guidelines (Committee to Revise the 1999 Guidelines for the Management of Patients with Acute Myocardial Infarction).Circulation110
:E82
–E292,2004
.
- Ale-Agha N, Stahl W, Sies H: (–)-Epicatechin effects in rat liver epithelial cells: stimulation of gap junctional communication and counteraction of its loss due to the tumor promoter 12-O-tetradecanoylphorbol-13-acetate.Biochem Pharmacol63
:2145
–2149,2002
.[Medline]
- Modun D, Music I, Katalinic V, Salamunic I, Boban M: Comparison of protective effects of catechin applied in vitro and in vivo on ischemia-reperfusion injury in the isolated rat hearts.Croat Med J44
:690
–696,2003
.[Medline]
- Maffei Facino R, Carini M, Aldini G, Berti F, Rossoni G, Bombardelli E, Morazzoni P: Procyanidines from Vitis vinifera seeds protect rabbit heart from ischemia/reperfusion injury: antioxidant intervention and/or iron and copper sequestering ability.Planta Med62
:495
–502,1996
.[Medline]
- Dulloo AG, Duret C, Rohrer D, Girardier L, Mensi N, Fathi M, Chantre P, Vandermander J: Efficacy of a green tea extract rich in catechin polyphenols and caffeine in increasing 24-h energy expenditure and fat oxidation in humans.Am J Clin Nutr70
:1040
–1045,1999
.[Abstract/Free Full Text]
- Prineas RJ, Jacobs DR, Crow RS, Blackburn H: Coffee, tea and VPB.J Chronic Dis33
:67
–72,1980
.[Medline]
- Graboys TB, Blatt CM, Lown B: The effect of caffeine on ventricular ectopic activity in patients with malignant ventricular arrhythmia.Arch Intern Med149
:637
–639,1989
.[Abstract/Free Full Text]
- Chelsky LB, Cutler JE, Griffith K, Kron J, McClelland JH, McAnulty JH: Caffeine and ventricular arrhythmias. An electrophysiological approach.JAMA264
:2236
–2240,1990
.[Abstract/Free Full Text]
- Newby DE, Neilson JM, Jarvie DR, Boon NA: Caffeine restriction has no role in the management of patients with symptomatic idiopathic ventricular premature beats.Heart76
:355
–357,1996
.[Abstract/Free Full Text]
- Donnerstein RL, Zhu D, Samson R, Bender AM, Goldberg SJ: Acute effects of caffeine ingestion on signal-averaged electrocardiograms.Am Heart J136
:643
–646,1998
.[Medline]
- Willett WC: "Nutritional Epidemiology
." New York: Oxford University Press,1990
.
- Corrao G, Rubbiati L, Bagnardi V, Zambon A, Poikolainen K: Alcohol and coronary heart disease: a meta-analysis.Addiction95
:1505
–1523,2000
.[Medline]
- Mukamal KJ, Muller JE, Maclure M, Sherwood JB, Mittleman MA: Lack of effect of recent alcohol consumption on the course of acute myocardial infarction.Am Heart J138
:926
–933,1999
.[Medline]
- Feskanich D, Rimm EB, Giovannucci EL, Colditz GA, Stampfer MJ, Litin LB, Willett WC: Reproducibility and validity of food intake measurements from a semiquantitative food frequency questionnaire.J Am Diet Assoc93
:790
–796,1993
.[Medline]
- Duffy SJ,Keaney JF, Jr, Holbrook M, Gokce N, Swerdloff PL, Frei B, Vita JA: Short- and long-term black tea consumption reverses endothelial dysfunction in patients with coronary artery disease.Circulation104
:151
–156,2001
.
- Hodgson JM, Puddey IB, Burke V, Watts GF, Beilin LJ: Regular ingestion of black tea improves brachial artery vasodilator function.Clin Sci (Lond)102
:195
–201,2002
.[Medline]
- Juliano LM, Griffiths RR: A critical review of caffeine withdrawal: empirical validation of symptoms and signs, incidence, severity, and associated features.Psychopharmacology (Berl)176
:1
–29,2004
.[Medline]
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ABSTRACT
INTRODUCTION
