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

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.

Intracoronary nicorandil induced hyperemia for physiological assessments in the coronary artery lesions

OBJECTIVE

Maximal hyperemia is a key element of invasive physiological examination. The aim of this study was to investigate the efficacy and safety of intracoronary (IC) nicorandil in comparison with adenosine 5'-triphosphate (ATP) intravenous (i.v.) injection for fractional flow reserve (FFR) measurement in coronary artery lesions.

MATERIALS AND METHODS

In this study, 46 patients who had their FFR measured were enrolled, including 51 lesions. Hyperemia was induced by bolus 2 mg nicorandil and ATP (40 mg ATP + 36 ml saline, weight × 10 ml/h) for FFR measurement. The safety and efficacy of IC nicorandil were evaluated.

RESULTS

The mean FFR values measured by nicorandil and ATP were 0.810 ± 0.013 and 0.799 ± 0.099, p < 0.001, respectively. There was a strong correlation between FFR measured by nicorandil and ATP (r = 0.983, R 2 = 0.966, FFRnicorandil = 0.937 × FFRATP + 0.061). The rate of FFR ≤ 0.75 in the nicorandil and ATP groups was 31.37 vs. 35.29%, respectively (p = 0.841), the consistency rate was 96.08%; the FFR ≤ 0.8 rate was 41.18 and 43.14%, respectively (p = 0.674), and the consistency rate was 90.20%. In five lesions, the FFR value measured by nicorandil ranged between 0.79 and 0.82, indicating inconsistency according to FFR ≤ 0.8. The blood pressure changes caused by nicorandil and ATP were 12.96 ± 6.83 and 22.22 ± 11.44 mmHg (p < 0.001); the heart rate changes were 2.43 ± 1.31 and 6.52 ± 2.87 beats/min, respectively (p < 0.001); and the PR interval changes were 6.0 (1.0-11.0) and 9.0 (2.0-19.0) ms, respectively (p < 0.001). Visual analog scale (VAS) scores in the nicorandil group were all in the range 0-2, while in the ATP group were mostly in the range of 3-5.

CONCLUSION

Intracoronary bolus of nicorandil (2 mg) infusion induces stable hyperemia, and it could be considered as an alternative drug to ATP for FFR measurement with a lower side effect profile in most patients.

Mechanisms of gradual pressure drop in angiographically normal left anterior descending and right coronary artery: Insights from wave intensity analysis

BACKGROUND

This study evaluated the mechanism of decline in coronary pressure from the proximal to the distal part of the coronary arteries in the left anterior descending (LAD) versus the right coronary artery (RCA) from the insight of coronary hemodynamics using wave intensity analysis (WIA).

METHODS

Twelve patients with angiographically normal LAD and RCA were prospectively enrolled. Distal coronary pressure, mean aortic pressure, and average peak velocity were measured at 4 different positions: 9, 6, 3, and 0 cm distal from each coronary ostium.

RESULTS

The distal-to-proximal coronary pressure ratio during maximum hyperemia gradually decreased in proportion to the distance from the ostium (0.92±0.03 and 0.98±0.03 at 9 cm distal to the LAD and RCA ostium). WIA showed the dominant forward-traveling compression wave gradually decreased and the backward-traveling suction wave gradually decreased in proportion to the decrease in coronary pressure through the length of the non-diseased LAD but not the RCA.

CONCLUSIONS

The pushing wave and suction wave intensities on WIA were diminished in proportion to the distance from the ostium of the LAD despite the wave intensity not changing across the length of the RCA, which may lead to gradual intracoronary pressure drop in the angiographically normal LAD.