Small Strictures Research Articles

The Differences of Quantitative Flow Ratio in Coronary Artery Stenosis with or without Atrial Fibrillation.

Quantitative flow ratio (QFR) is a new method for the assessment of the extent of coronary artery stenosis. But it may be obscured by the cardiac remodeling and abnormal blood flow of the coronary artery when encountering atrial fibrillation (AF). The present study aimed to examine the impact of these changed structures and blood flow of coronary arteries on QFR results in AF patients. Methods and Results. We evaluated QFR in 223 patients (112 patients with AF; 111 non-AF patients served as controls) who had undergone percutaneous coronary intervention (PCI) due to severe stenoses in coronary arteries. QFR of the target coronary was determined according to the flow rate of the contrast agent. Results showed that AF patients had significantly higher QFR values than control (0.792 ± 0.118 vs. 0.685 ± 0.167, p < 0.001). We further analyzed local QFR around the stenoses (0.858 ± 0.304 vs. 0.756 ± 0.146, p=0.002), residual QFR (0.958 ± 0.055 vs. 0.929 ± 0.093, p=0.005), and index QFR (0.807 ± 0.108 vs. 0.713 ± 0.152, p < 0.001) in these two groups of patients with and without AF. Further analysis revealed that QFR in AF patients was negatively correlated with coronary flow velocity (R = -0.22, p=0.02) and area of stenosis (R = -0.70, p < 0.001) but positively correlated with the minimum lumen area (MLA) (R = 0.47, p < 0.001). Conclusion. AF patients with coronary artery stenosis have higher QFR values, which are associated with decreased blood flow velocity, smaller stenosis, and larger MLA in AF patients upon cardiac remodeling.

The speed, reflection and intensity of waves propagating in flexible tubes with aneurysm and stenosis: Experimental investigation.

A localized stenosis or aneurysm is a discontinuity that presents the pulse wave produced by the contracting heart with a reflection site. However, neither wave speed (c) in these discontinuities nor the size of reflection in relation to the size of the discontinuity has been adequately studied before. Therefore, the aim of this work is to study the propagation of waves traversing flexible tubes in the presence of aneurysm and stenosis in vitro. We manufactured different sized four stenosis and four aneurysm silicone sections, connected one at a time to a flexible ‘mother’ tube, at the inlet of which a single semi-sinusoidal wave was generated. Pressure and velocity were measured simultaneously 25 cm downstream the inlet of the respective mother tube. The wave speed was measured using the PU-loop method in the mother tube and within each discontinuity using the foot-to-foot technique. The stenosis and aneurysm dimensions and c were used to determine the reflection coefficient (R) at each discontinuity. Wave intensity analysis was used to determine the size of the reflected wave. The reflection coefficient increased with the increase and decrease in the size of the aneurysm and stenosis, respectively. c increased and decreased within stenosis and aneurysms, respectively, compared to that of the mother tube. Stenosis and aneurysm induced backward compression and expansion waves, respectively; the size of which was related to the size of the reflection coefficient at each discontinuity, increases with smaller stenosis and larger aneurysms. Wave speed is inversely proportional to the size of the discontinuity, exponentially increases with smaller stenosis and aneurysms and always higher in the stenosis. The size of the compression and expansion reflected wave depends on the size of R, increases with larger aneurysms and smaller stenosis.

Ureteral Stenosis After Renal Transplantation—A Single-Center 10-Year Experience

BackgroundKidney transplantation (KT) is the definitive treatment for ESRD. Ureteral stenosis (US) is one of the most common urologic complications and has been reported in 2.6%–15% of KTs. MethodsWe reviewed data for 973 consecutive KT procedures performed at our center from January 2004 to September 2014, with evaluation of US management and recurrence rate. ResultsThe 973 KTs were performed with the use of the direct ureterovesical (UV) implantation Paquin technique, and the mean follow-up time was 44.3 ± 30.2 [range, 3–111] months. During this period, 33 cases of US (3.39%) were reported. The interval from KT to US diagnosis was 10.6 ± 23.0 (range, 0.5–98.0) months. The majority of the US cases were located in the distal ureter and UV junction (83.9%), with only 2 cases of middle ureter stenosis and 2 cases of ureteropelvic junction. Mean US length was 2.5 ± 1.9 (range, 1.0–10.0) cm. Surgical management and global and treatment-specific recurrence rates were reviewed. Primary surgical treatment recurrence rate was higher for the endoscopic approach, with a mean global time from treatment to US recurrence of 6.9 ± 16.3 (range, 0–65) months and a median of 2.0 months. Open surgical approach was the main recurrence treatment option (74%). There were 2 cases of graft loss. Success rate evaluation of overall and treatment-specific primary surgical management did not reveal significant differences (P > .05) according to stenosis length (<1.5, 1.5–3.0, or >3.0 cm), time between transplant and stenosis (≤3, 3–12, or >12 mo), or stenosis location (distal, middle, or upper ureter). However, there was clearly a trend to higher success rate in smaller stenosis (<1.5 cm) and early management (≤3 mo), particularly with the use of balloon dilation. ConclusionsUS management should be decided on a case-by-case basis according to clinical characteristics, treatment-specific recurrence rate, and previous surgical options.

Wave speed and reflections proximal to aneurism and stenosis of flexible tubes.

Arterial aneurism and stenosis are disorders that lead to circulation malfunction. Stenosis often leads to hypoxia of the organ depending on the affected artery, whilst aneurism can lead to dissection with known lethal consequences. On both cases, the pulse wave produced by the contracting heart is reflected at these discontinuities, and estimating the size of these reflected waves using wave intensity analysis (WIA) is the main aim of this work. We also aim to measure wave speed, or pulse wave velocity (PWV) as more commonly known within the discontinuities. We manufactured 4 stenosis and 4 aneurism silicon sections, connected one at a time to a mother tube, and tested in vitro. Pressure and flow were measured proximal to the discontinuity and were used to calculate WIA. PWV was calculated using the foot to foot technique and also the classical Moens-Korteweg and Bramwell-Hill equations. Wave speed in an aneurism decreases, whereas it increases in a stenosis, all compared to the values determined in a standard mother tube. Presence of aneurisms resulted in a backward expansion whilst the presence of stenosis resulted in a backward compression wave, which related linearly to the size of the discontinuity. Larger aneurisms and smaller stenosis cause an increase in wave reflection.

Hemodynamics at stenoses formed by growing platelet thrombi in mesenteric microvasculature of rat

Quantitative analyses of the dynamics of stenosis development were expressed in terms of the time course for changes in blood flow velocity in a stenosed region and thrombus configuration in the microvasculature of rat mesentery. The platelet thrombus was induced in microvessels by irradiation of filtered light in combination with intravascular administration of fluorescent dye. The blood flow velocity began to increase soon after the initiation of thrombus formation and continued to increase progressively with the growth of the thrombus in the radial direction. After the velocity reached an almost constant level, the velocity fluctuation became significant due to the frequent detachment of platelet aggregates. Meanwhile, the blood flow velocity precipitously dropped. Two different definitions of a critical stenosis were proposed. The first definition was the condition that the blood flow velocity reached a maximum. The critical area stenosis based on this definition had almost a constant value, i.e., 75–95% of the lumen area. The second definition of critical stenosis was given as the condition that the blood flow rate decreased by more than 15%. In the higher velocity range the values of critical stenosis based on the second definition were almost constant, i.e., 70–90% of the lumen area. However, in the lower velocity range, the critical condition seemed to occur in smaller stenosis.