Effects of intravenous caffeine on fractional flow reserve measurements in coronary artery disease

Coronary microcirculatory dysfunction can be assessed by positive dicrotic wave and amplitude index on resting distal coronary pressure waveform, a newly developed index

Aims

Some lesions have high resting distal coronary pressure/aortic pressure (Pd/Pa) despite low fractional flow reserve (FFR). This study aimed to assess microcirculatory dysfunction as a possible basal mechanism.

Methods and results

Patients were grouped into two according to coffee intake (caffeine 222 mg) before coronary angiography. Through an adenosine-induced Pd/Pa decrease, amplitude index was calculated by dividing the difference between the highest pressure after the inflection point and the minimal diastolic pressure by the pulse pressure on the Pd waveform. In 130 coronary lesions (caffeine group, n = 69; non-caffeine group, n = 61) from 113 patients, the amplitude index through the adenosine-induced Pd/Pa decrease in all lesions was 0.54 ± 0.11 at resting Pd/Pa and 0.44 ± 0.12 at FFR (P < 0.0001). The positive dicrotic wave distribution on a maximal hyperaemia (FFRnicr)-resting Pd/Pa graph was analysed. In lesions with FFRnicr <0.80 on the FFRnicr-resting Pd/Pa graph, the resting Pd/Pa was divided into three zones based on Pd/Pa values: high-remaining, intermediate, and low. The high-remaining zone had a higher amplitude index than the intermediate zone (0.60 ± 0.09 vs. 0.48 ± 0.12; P < 0.005); the low zone lesions had no inflection point (no amplitude index). The high-remaining zone correlated with a larger positive dicrotic wave than the intermediate zone (94 vs. 30%; P < 0.005). Most lesions in the high-remaining zone corresponded to the caffeine group.

Conclusion

In severe coronary stenosis, a high-remaining resting Pd/Pa with a high amplitude index or a positive dicrotic wave on the resting Pd waveform suggests microcirculatory dysfunction, such as insufficient arteriolar dilation reactive to myocardial ischaemia.

Registration

UMIN000046883.

Influence of caffeine intake on intravenous adenosine-induced fractional flow reserve

BACKGROUND

This study evaluated whether caffeine abstention is required before fractional flow reserve (FFR) measurement by intravenous adenosine triphosphate (ATP) administration in Japanese patients.

METHODS

This study was a subanalysis of a previously published study and a total of 208 intermediate lesions that underwent FFR measurements were enrolled for this analysis. Hyperemia was induced by continuous intravenous ATP infusion at 150 μg/kg/min (IVATP150) and 210 μg/kg/min (IVATP210), and by intracoronary administration of nicorandil 2 mg (ICNIC2mg) as a reference standard.

RESULTS

The degree of change in the FFR value after ICNIC2mg and IVATP210 was similar between the caffeine and non-caffeine groups (0.00 ± 0.02 vs. 0.01 ± 0.02). In patients who consumed caffeine before the FFR measurement, the degree of FFR change was independent of the time interval (<12 h, 12-24 h, and 24-48 h) between caffeine intake and catheterization both after IVATP150 and ICNIC2mg and after IVATP210 and ICNIC2mg.

CONCLUSION

When compared with the FFR value after ICNIC2mg, the degree of change in the FFR value after IVATP210 were similar regardless of caffeine intake. Strict caffeine abstention before intravenous ATP-induced FFR measurement may not be required in clinical practice.

Caffeine attenuates seizure and brain mitochondrial disruption induced by Tramadol: the role of adenosinergic pathway

Tramadol (TR) is an analgesic drug used to treat moderate-to-severe pain but it induces seizure even at therapeutic doses. The exact mechanism of TR-inducing seizure is not clear but inhibition of the serotonin, GABA, and nitrous oxide (NOS) pathways are the commonly proposed mechanisms. Adenosinergic system has a crucial function in the modulation of seizure. Also, oxidative damage is an unavoidable effect of the seizure. This study was conducted to evaluate the role of the adenosinergic system on the seizure and oxidative stress biomarkers induced by TR using antagonist of the adenosinergic receptors in the Albino mice. For that purpose, generated clonic seizure, as seizure threshold, was evaluated by TR. Caffeine (CAF; 8 mg/kg, i.p.), a nonselective antagonist of adenosine receptors, was administered 1 hour before the seizure induction. The seizure threshold significantly increased by CAF-treated group when compared to TR group (p < 0.001). Oxidative stress biomarkers such as reactive oxygen species, protein carbonyl content, and lipid peroxidation significantly decreased and glutathione content significantly increased by CAF in brain mitochondria compared to the TR group, whereas oxidative biomarkers significantly increased in the TR group compared to the control group. The results of the present study suggested that the adenosinergic system is involved in seizure induced by TR and meanwhile, inhibition of adenosine receptors can decrease the TR seizure threshold and also decrease the induced oxidative damage in the brain mitochondria.

Effects of Caffeine on Myocardial Blood Flow: A Systematic Review

Background. Caffeine is one of the most widely consumed stimulants worldwide. It is a well-recognized antagonist of adenosine and a potential cause of false-negative functional measurements during vasodilator myocardial perfusion. The aim of this systematic review is to summarize the evidence regarding the effects of caffeine intake on functional measurements of myocardial perfusion in patients with suspected coronary artery disease. Pubmed, Web of Science, and Embase were searched using a predefined electronic search strategy. Participants—healthy subjects or patients with known or suspected CAD. Comparisons—recent caffeine intake versus no caffeine intake. Outcomes—measurements of functional myocardial perfusion. Study design—observational. Fourteen studies were deemed eligible for this systematic review. There was a wide range of variability in study design with varying imaging modalities, vasodilator agents, serum concentrations of caffeine, and primary outcome measurements. The available data indicate a significant influence of recent caffeine intake on cardiac perfusion measurements during adenosine and dipyridamole induced hyperemia. These effects have the potential to affect the clinical decision making by re-classification to different risk-categories.

Assessment of increasing intravenous adenosine dose in fractional flow reserve

Background

Effects of increased adenosine dose in the assessment of fractional flow reserve (FFR) were studied in relation to FFR results, hemodynamic effects and patient discomfort. FFR require maximal hyperemia mediated by adenosine. Standard dose is 140 μg/kg/min administrated intravenously. Higher doses are commonly used in clinical practice, but an extensive comparison between standard intravenous dose and a high dose (220 μg/kg/min) has previously not been performed.

Methods

Seventy-five patients undergoing FFR received standard dose adenosine, followed by high dose adenosine. FFR, mean arterial pressure (MAP) and heart rate (HR) were analyzed. Patient discomfort measured by Visual Analogue Scale (VAS) was assessed.

Results

No significant difference was found between the doses in FFR value (0.85 [0.79–0.90] vs 0.85 [0.79–0.89], p = 0.24). The two doses correlated well irrespective of lesion severity (r = 0.86, slope = 0.89, p = <0.001). There were no differences in MAP or HR. Patient discomfort was more pronounced using high dose adenosine (8.0 [5.0–9.0]) versus standard dose (5.0 [2.0–7.0]), p = <0.001.

Conclusions

Increased dose adenosine does not improve hyperemia and is associated with increased patient discomfort. Our findings do not support the use of high dose adenosine.

Trial registration

Retrospective Trial registration: Current Controlled Trials ISRCTN14618196. Registered 15 December 2016.

Effects of caffeine on fractional flow reserve values measured using intravenous adenosine triphosphate

We investigated the effects of caffeine intake on fractional flow reserve (FFR) values measured using intravenous adenosine triphosphate (ATP) before cardiac catheterization. Caffeine is a competitive antagonist for adenosine receptors; however, it is unclear whether this antagonism affects FFR values. Patients were evenly randomized into 2 groups preceding the FFR study. In the caffeine group (n = 15), participants were given coffee containing 222 mg of caffeine 2 h before the catheterization. In the non-caffeine group (n = 15), participants were instructed not to take any caffeine-containing drinks or foods for at least 12 h before the catheterization. FFR was performed in patients with more than intermediate coronary stenosis using the intravenous infusion of ATP at 140 μg/kg/min (normal dose) and 170 μg/kg/min (high dose), and the intracoronary infusion of papaverine. FFR was followed for 30 s after maximal hyperemia. In the non-caffeine group, the FFR values measured with ATP infusion were not significantly different from those measured with papaverine infusion. However, in the caffeine group, the FFR values were significantly higher after ATP infusion than after papaverine infusion (P = 0.002 and P = 0.007, at normal and high dose ATP vs. papaverine, respectively). FFR values with ATP infusion were significantly increased 30 s after maximal hyperemia (P = 0.001 and P < 0.001 for normal and high dose ATP, respectively). The stability of the FFR values using papaverine showed no significant difference between the 2 groups. Caffeine intake before the FFR study affected FFR values and their stability. These effects could not be reversed by an increased ATP dose.

Caffeine reduces the sensitivity of vasodilator MPI for the detection of myocardial ischaemia: Pro

Caffeine is a non-selective antagonist at the adenosine receptors, which is expected to reverse both the intended (coronary vasodilation) and unintended (hypotension, flushing) effects of exogenously administered adenosine and adenosine-related compounds. In the past, several studies were conducted to characterize the effect of caffeine on vasodilator myocardial perfusion imaging (MPI) with conflicting results. However, new evidence supports earlier observations and shows that recent caffeine intake attenuates vasodilator-induced myocardial hyperaemia and may therefore reduce the sensitivity of radionuclide MPI for the detection of inducible perfusion abnormality in patients with coronary artery disease. Although the magnitude of this effect and hence its clinical significance are dose dependent, the acute response to equivalent doses of caffeine varies largely among individuals, and this might be explained by differences in caffeine exposure and genetically determined variations in caffeine metabolism. Abstinence from caffeinated foods and beverages for a minimum of 12 hours before vasodilator stress is therefore recommended although longer abstention might be required in order to prevent the potentially blocking effect of residual caffeine on vasodilator-mediated actions.