The coronary endothelial function is recognized to have an important role in the physiology of the diastolic ventricular relaxation, a phase of the heart cycle that influences the electrocardiographic QT interval. Endothelial function is investigated in vivo by flow mediated dilation (FMD) in the brachial artery and has proven to be a strong predictor of both coronary endothelial function and cardiovascular events. It has been reported that coffee acutely induces FMD changes. In particular, the brachial artery FMD seems to decrease after caffeinated coffee (CC) and to increase after decaffeinated coffee (DC) ingestion. Since the cardiovascular effects of coffee are still a debated matter, this study aimed at investigating with a randomized, double-blind crossover design, if the QT interval of adult healthy subjects (19 males and 21 females) changes in the hour following CC or DC ingestion. Both systolic and diastolic blood pressure were higher in the hour following the ingestion of CC; the heart rate significantly increased 30 minutes after CC ingestion. A significant increase of the QT duration was observed one hour after DC ingestion (398.9 ± 3.8 vs 405.3 ± 3.7 msec; P < 0.05), not after CC. The QT interval corrected for heart rate did not significantly change following CC or DC ingestion. In conclusion, despite CC and DC previously demonstrated to influence the FMD they do not seem to induce a significant unfavourable acute change of the left ventricular repolarization. Further investigations are required to elucidate the effects of coffee in subjects with cardiovascular diseases.
FindingsMany controversies exist about the cardiovascular effects of coffee in man. We recently demonstrated [1] that endothelial function in healthy subjects, measured using flow-mediated dilation (FMD) of the brachial artery, is significantly lower in the hour following the ingestion of 25 ml of espresso coffee. On the contrary, there was a dose-dependent significant increase in FMD when one (25 ml) or two (50 ml) cups of decaffeinated coffee were ingested [1,2]. We attributed these differences to the opposite effects of caffeine and anti-oxidant substances contained in coffee mixtures. The coronary endothelial function is recognized to have an important role in the physiology of the diastolic ventricular relaxation, therefore, it cannot be excluded that the effects of coffee on the FMD in the brachial artery are of some relevance also for both the coronary bed and the diastolic function. The electrocardiographic QT interval explores the repolarization that occurs during the left ventricular diastolic phase; furthermore, the QT corrected for heart rate (QTc) has been correlated with both atherosclerotic disease and cardiovascular mortality. It has been reported that caffeine ingestion unfavourably affects the QT interval during sleeping in adult healthy subjects [3], however, another study did not evidence any significant influence of caffeine ingestion on the QT interval [4]. Since no study has directly investigated the e...