Circulation Journal Official Journal of the Japanese Circulation Society http://www. j-circ.or.jp Methods Study PopulationWe retrospectively enrolled 51 consecutive de novo native coronary artery lesions from 44 angina patients who were treated using a single 2nd-generation DES (Xience Prime, Promus Element, or Nobori) under OCT guidance. Exclusion criteria were as follows: coronary artery bypass graft, post-stent dilatation using 2 balloons (kissing balloon inflation and hugging balloon inflation), in-stent restenosis, uninterpretable OCT image, and inability to cross the lesion with the OCT catheter. This study was approved by the Kawasaki Medical School Internal Review Board. Because of the retrospective study design, written informed consent for the interventional procedures, including OCT imaging, was obtained from the patients. Study ProtocolsCardiac Catheterization and OCT After intravenous heparin (100U/kg) and intracoronary nitroglycerin (200 μg) were urrently, 2nd-generation drug-eluting stents (DES) offer good clinical results, 1-4 yet stent underexpansion is still a concern as a cause of DES failure 5-10 or stent thrombosis. 11 Although the extent of coronary calcification is considered to be a contributing factor in stent underexpansion, previous intravascular ultrasound (IVUS) studies have failed to demonstrate a relationship between stent expansion and coronary calcification. 12-14 We previously reported that optical coherence tomography (OCT) offers better quantitative assessment of coronary calcification than IVUS, because OCT can delineate calcified plaque without artifacts. 15 Therefore, we hypothesized that quantitative assessment of coronary calcification using OCT had the potential to predict stent expansion. Accordingly, the purpose of this study was to investigate whether stent expansion could be predicted by the extent of coronary calcification as assessed by OCT. Impact of Target Lesion CoronaryCalcification on Stent Expansion Background: Stent underexpansion remains a concern as a cause of drug-eluting stent (DES) failure. Although coronary calcification is considered to be a contributing factor in stent underexpansion, previous intravascular ultrasound studies have failed to demonstrate this relationship. We investigated whether stent expansion could be predicted by coronary calcification as assessed by optical coherence tomography (OCT).

Traditionally, invasive coronary physiological assessment has focused on the epicardial coronary artery. More recently, appreciation of the importance of the coronary microvasculature in determining patient outcomes has grown. Several invasive modalities for interrogating microvascular function have been proposed. Angiographic techniques have been limited by their qualitative and subjective nature. Doppler wire-derived coronary flow reserve has been applied in research studies, but its clinical role has been limited by its lack of reproducibility, its lack of a clear normal value, and the fact that it is not specific for the microvasculature but interrogates the entire coronary circulation. The index of microcirculatory resistance-a thermodilution-derived measure of the minimum achievable microvascular resistance-is relatively easy to measure, more reproducible, has a clearer normal value, and is independent of epicardial coronary artery stenosis. The index of microcirculatory resistance has been shown to have prognostic value in patients with ST-segment-elevation myocardial infarction and cardiac allograft vasculopathy after heart transplantation. Emerging data demonstrate its role in evaluating patients with chest pain and nonobstructive coronary artery disease. Increasingly, the index of microcirculatory resistance is used as a reference standard for invasively assessing the microvasculature in clinical trials.

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OBJECTIVES This study investigated sex differences in coronary flow reserve (CFR) and the index of microcirculatory resistance (IMR) in patients with angina in the absence of obstructive coronary artery disease. BACKGROUND Coronary microvascular dysfunction is associated with worse long-term outcomes, especially in women. Coronary flow reserve (CFR) and the index of microcirculatory resistance (IMR) are 2 methods of assessing the coronary microcirculation. METHODS We prospectively enrolled 117 women and 40 men with angina in the absence of obstructive coronary artery disease. We performed CFR, IMR, fractional flow reserve, and quantitative coronary angiography in the left anterior descending artery. Coronary flow was assessed with a thermodilution method by obtaining mean transit time (Tmn) (an inverse correlate to absolute flow) at rest and hyperemia. RESULTS All patients had minimal atherosclerosis by quantitative coronary angiography (% diameter stenosis: 23.2 ± 12.3%), and epicardial disease was milder in women (fractional flow reserve: 0.88 ± 0.04 vs. 0.87 ± 0.04; p = 0.04). IMR was similar between the sexes (20.7 ± 9.8 vs. 19.1 ± 8.0; p = 0.45), but CFR was lower in women (3.8 ± 1.6 vs. 4.8 ± 1.9; p = 0.004). This was primarily due to a shorter resting Tmn in women (p = 0.005), suggesting increased resting coronary flow, whereas hyperemic Tmn was identical (p = 0.79). In multivariable analysis, female sex was an independent predictor of lower CFR and shorter resting Tmn. CONCLUSIONS Despite similar microvascular function in women and men by IMR, CFR is lower in women. This discrepancy appears to be due to differences in resting coronary flow between the sexes. The effect of sex differences should be considered in interpretation of physiological indexes using resting coronary flow.

The cFFR, iFR, and Pd/Pa are less accurate in LM/pLAD compared with other lesion locations, likely related to the larger amount of myocardium supplied by LM/pLAD. Nevertheless, cFFR provides the best diagnostic accuracy among the adenosine-free indices, regardless of lesion location.