Usefulness of intravascular ultrasound assessment after development of the slow flow phenomenon during percutaneous coronary intervention.

The slow flow phenomenon is a critical complication during percutaneous coronary intervention (PCI) that leads to poor outcomes. We aimed to evaluate the mechanisms underlying the slow flow phenomenon using intravascular ultrasound (IVUS). We retrospectively analyzed IVUS data from 62 lesions in 58 consecutive patients who experienced the slow flow phenomenon during PCI. IVUS was performed immediately after the development of the slow flow phenomenon to assess its cause. No IVUS-based evidence of mechanical obstruction was categorized as distal embolization. Distal embolization was observed in 46 lesions (74%). The slow flow phenomenon occurred in all these lesions after stent implantation. In addition to distal embolization, three different mechanisms underlying the induction of the slow flow phenomenon due to mechanical obstructions (16 lesions, 26%) were detected on IVUS, namely, medial dissection/hematoma (6 lesions), intimal flap (6 lesions), and thrombus obstruction (4 lesions). Most mechanical obstructions (13 lesions, 81%) could not be identified by angiography alone. In 15/16 lesions (94%) with mechanical obstruction, deteriorated flow improved immediately after balloon dilatation or bail-out stent implantation, although intracoronary vasodilator administration could not reestablish coronary flow. The frequency of mechanical obstruction as the cause of the slow flow phenomenon was relatively high. Given the difficulty in angiographical differentiation, IVUS-guided management of slow flow may be a useful strategy.

Intravascular Ultrasound-Derived Virtual Fractional Flow Reserve for the Assessment of Myocardial Ischemia.

BACKGROUND: Fractional flow reserve (FFR) is widely used for the assessment of myocardial ischemia. Intravascular ultrasound (IVUS) is an intracoronary imaging method that provides information about lumen and vessel morphology. Previous studies on the expanded use of IVUS to identify functional ischemia have noted an association between anatomy and physiology, but IVUS-derived minimum lumen area (MLA) has a weak-moderate correlation with myocardial ischemia compared with FFR. We developed a method to calculate FFR using IVUS-derived anatomical information for the assessment of myocardial ischemia. The aims of this study were to investigate the relationship between wire-based FFR and IVUS-derived FFR (IVUS-FFR) and to compare the usefulness of IVUS-FFR and IVUS-derived MLA for functional assessment.Methods and Results:We retrospectively analyzed 50 lesions in 48 patients with coronary stenosis who underwent IVUS and FFR simultaneously. IVUS-FFR was calculated using our original algorithm and fluid dynamics. Mean percent diameter stenosis determined on quantitative coronary angiography and on FFR was 56.4±10.7 and 0.69±0.08, respectively. IVUS-FFR had a stronger linear correlation with FFR (R=0.78, P<0.001; root mean square error, 0.057 FFR units) than with IVUS-derived MLA (R=0.43, P=0.002). CONCLUSIONS: IVUS-FFR may be a more valuable method to identify myocardial ischemia, compared with IVUS-derived MLA.

Intracoronary Optical Coherence Tomography-Derived Virtual Fractional Flow Reserve for the Assessment of Coronary Artery Disease.

Fractional flow reserve (FFR) is widely used for the assessment of myocardial ischemia. Optical coherence tomography (OCT) provides accurate visualization of coronary artery morphology. The aim of this study was to investigate the relation between FFR and OCT-derived FFR. We retrospectively analyzed 31 lesions (25 left anterior descending arteries, 2 left circumflex arteries, and 4 right coronary arteries) in 31 patients with moderate-to-severe coronary stenosis, who underwent OCT and FFR measurements simultaneously. OCT-derived FFR was calculated by the original algorithm, which was calculated using the following equation based on fluid dynamics: ΔP = FV + SV2, where V is the flow velocity, F is the coefficient of pressure loss because of viscous friction (Poiseuille resistance), and S is the coefficient of local pressure loss because of abrupt enhancement (flow separation). Mean values of % diameter stenosis by quantitative coronary angiography and FFR were 55.2 ± 14.0% and 0.70 ± 0.14, respectively. OCT-derived FFR showed a stronger linear correlation with FFR measurements (r = 0.89, p <0.001; root mean square error = 0.062 FFR units) than quantitative coronary angiography % diameter stenosis (r = -0.65, p <0.001), OCT measurements of minimum lumen area (r = 0.68, p <0.001), and % area stenosis (r = -0.70, p <0.001). OCT-derived FFR has the potential to become an alternative method for the assessment of functional myocardial ischemia, and may elucidate the relation between coronary morphology and FFR.

Assessment of reperfused acute myocardial infarction with two-phase contrast-enhanced helical CT: prediction of left ventricular function and wall thickness.

PURPOSE: To investigate whether two-phase contrast material-enhanced computed tomographic (CT) findings serve as predictors of changes in left ventricular (LV) function and wall thickness (WT) after acute myocardial infarction (MI) and successful angioplasty. MATERIALS AND METHODS: Ethics committee approval and informed consent were obtained. In 58 patients (51 men and seven women; mean age, 62 years +/- 12 [standard deviation]) who had experienced an acute MI and undergone successful angioplasty, two-phase (acquisitions at 45 seconds and 7 minutes) contrast-enhanced CT was performed in the acute (mean interval between treatment and CT, 37 hours +/- 4) and intermediate (mean interval, 28 days +/- 4) periods and for long-term (mean interval, 12 months +/- 4) follow-up. CT images were reviewed for an early perfusion defect (ED) at 45 seconds and for late enhancement (LE) and a residual perfusion defect (RD) at 7 minutes. Myocardial enhancement patterns and WT were assessed, and LV ejection fraction (LVEF) and percentage decrease in WT were calculated. The patient group was subdivided into three groups according to enhancement pattern: Group 1 included patients with LE but no ED or RD; group 2, patients with ED and LE but no RD; and group 3, patients with ED, LE, and RD. Fisher exact testing was used to measure categorical response. Paired and unpaired t tests were used for comparison between two groups (points); Tukey-Kramer multiple comparison and repeated-measures analysis of variance were used for comparisons between the three groups. P < .05 was considered to indicate a significant difference. RESULTS: In group 3 (n = 36), WT in infarcted area was significantly reduced at the intermediate and long-term CT examinations (P < .001). At the intermediate and long-term examinations, percentage decrease in WT was greater in group 2 (n = 10) than in group 1 (n = 12) (P < .05 for intermediate and P < .001 for long-term examination) and was greatest in group 3 (P < .001 for both examinations). LVEF was poorest in group 3 and best in group 1. CONCLUSION: Two-phase contrast-enhanced CT proved useful in predicting LV functional recovery and WT in patients who had experienced acute MI and undergone successful angioplasty.