Influence of Variable Native Arterial Diameter and Vasculature Status on Coronary Diagnostic Parameters

ABSTRACT Fractional flow reserve (FFR), the ratio of the pressures distal (P d ) and proximal (P a ) to a stenosis, and coronary flow reserve (CFR), the ratio of flows at maximal vasodilation to the resting condition, are widely used for determining the functional severity of a coronary artery stenosis. However, the diameter of the native artery might influence the FFR values. Therefore, using an in-vitro experimental study, we tested the variation of FFR for two arterial diameters, 2.5 mm (N1) and 3 mm (N2). We hypothesize that FFR is not influenced by native arterial diameter. For both N1 and N2, vasodilation-distal perfusion pressure (CFR-P rh ) curves were obtained using a 0.35 mm guidewire by simulating physiologic flows under different blockage conditions: mild (64% area stenosis (AS)), intermediate (80% AS) and severe (90% AS). The FFR values for the two arterial models differed insignificantly, within 3%, for mild and intermediate stenoses but differed appreciably for severe stenosis (~25%). This significant difference in FFR values for severe stenosis can be attributed to relatively larger difference in guidewire obstruction effect at the stenotic throat region of the two native arterial models. These findings confirm that FFR will not differ for the clinically relevant cases of mild and intermediate stenosis for different arterial diameters

Endothelial Cell Injury Under High Frequency Vibration in the Rat-Tail Model

ABSTRACT Hand-Arm Vibration Syndrome (HAVS) consists of vascular, sensorineural and musculoskeletal disorders and affects around 1.7-5.8% of industrial workers. In this study, a rat-tail vibration injury model is used to assess early vascular damage due to HAVS, manifested in the form of endothelial cell vacuolation and oxidative injury. Tails were vibrated at two frequencies 125Hz and 250Hz for 4hr/day for 1 and 5 days (49m/s 2 ). Hematoxylin and Eosin (H&E) staining was done to assess gross changes in artery sections and toluidine blue stain was done for vacuole counting. Immunohistochemical (IHC) methods were used to detect Nitrotyrosine, a potent biomarker of cell inflammation and oxidative stress. The vacuole count in Endothelial Cells (ECs) was not statistically significant after 1 and 5 days for any frequency. However IHC images showed significant oxidative damage in Endothelial Cells (ECs) with considerable oxidative damage being induced as early as 1 day for both 125Hz and 250Hz frequencies, with more EC damage induced by 250Hz frequency after 5 days. These findings indicate that higher frequency vibrations can cause severe oxidative damage to EC

Role of Pulse Pressure and Geometry of Primary Entry Tear in Acute Type B Dissection Propagation

The hemodynamic and geometric factors leading to propagation of acute Type B dissections are poorly understood. The objective is to elucidate whether geometric and hemodynamic parameters increase the predilection for aortic dissection propagation. A pulse duplicator set-up was used on porcine aorta with a single entry tear. Mean pressures of 100 and 180 mmHg were used, with pulse pressures ranging from 40 to 200 mmHg. The propagation for varying geometric conditions (%circumference of the entry tear: 15–65%, axial length: 0.5–3.2 cm) were tested for two flap thicknesses (1/3rd and 2/3rd of the thickness of vessel wall, respectively). To assess the effect of pulse and mean pressure on flap dynamics, the %true lumen (TL) cross-sectional area of the entry tear were compared. The % circumference for propagation of thin flap (47 ± 1%) was not significantly different (p = 0.14) from thick flap (44 ± 2%). On the contrary, the axial length of propagation for thin flap (2.57 ± 0.15 cm) was significantly different (p < 0.05) from the thick flap (1.56 ± 0.10 cm). TL compression was observed during systolic phase. For a fixed geometry of entry tear (%circumference = 39 ± 2%; axial length = 1.43 ± 0.13 cm), mean pressure did not have significant (p = 0.84) effect on flap movement. Increase in pulse pressure resulted in a significant change (p = 0.02) in %TL area (52 ± 4%). The energy acting on the false lumen immediately before propagation was calculated as 75 ± 9 J/m(2) and was fairly uniform across different specimens. Pulse pressure had a significant effect on the flap movement in contrast to mean pressure. Hence, mitigation of pulse pressure and restriction of flap movement may be beneficial in patients with type B acute dissections

Original Article Dependence of Vascular Damage on Higher Frequency Components in the Rat-tail Model

Abstract: Hand-Arm Vibration Syndrome (HAVS) is caused by hand-transmitted vibration in industrial workers. Current ISO guidelines (ISO 5349) might underestimate vascular injury associated with range of vibration frequencies near resonance. A rat-tail model was used to investigate the effects of higher frequencies&gt;100 Hz on early vascular damage. 13 Male Sprague-Dawley rats (250 ± 15 gm) were used. Rat-tails were vibrated at 125 Hz and 250 Hz (49 m/s 2) for 1D, 5D and 10D; D=days (4 h/day). Structural damage of the ventral artery was quantified by vacuole count using Toluidine blue staining whereas biochemical changes were assessed by nitrotyrosine (NT) staining. The results were analyzed using one-way repeated measures mixed-model ANOVA at p&lt;0.05 level of significance. The structural damage increased at 125 Hz causing significant number of vacuoles (40.62 ± 9.8) compared to control group (8.36 ± 2.49) and reduced at 250 Hz (12.33 ± 2.98) compared to control group (8.36 ± 2.49). However, the biochemical alterations (NT-signal) increased significantly for 125 Hz (143.35 ± 5.8 gray scale value, GSV) and for 250 Hz (155.8 ± 7.35 GSV) compared to the control group (101.7 ± 4.18 GSV). Our results demonstrate that vascular damage in the form of structural and bio chemical disruption is significant at 125 Hz and 250 Hz. Hence the current ISO guidelines might underestimate vascular damage at frequencies&gt;100 Hz

Role of Pulse Pressure and Geometry of Primary Entry Tear in Acute Type B Dissection Propagation.

The hemodynamic and geometric factors leading to propagation of acute Type B dissections are poorly understood. The objective is to elucidate whether geometric and hemodynamic parameters increase the predilection for aortic dissection propagation. A pulse duplicator set-up was used on porcine aorta with a single entry tear. Mean pressures of 100 and 180 mmHg were used, with pulse pressures ranging from 40 to 200 mmHg. The propagation for varying geometric conditions (%circumference of the entry tear: 15-65%, axial length: 0.5-3.2 cm) were tested for two flap thicknesses (1/3rd and 2/3rd of the thickness of vessel wall, respectively). To assess the effect of pulse and mean pressure on flap dynamics, the %true lumen (TL) cross-sectional area of the entry tear were compared. The % circumference for propagation of thin flap (47 ± 1%) was not significantly different (p = 0.14) from thick flap (44 ± 2%). On the contrary, the axial length of propagation for thin flap (2.57 ± 0.15 cm) was significantly different (p &lt; 0.05) from the thick flap (1.56 ± 0.10 cm). TL compression was observed during systolic phase. For a fixed geometry of entry tear (%circumference = 39 ± 2%; axial length = 1.43 ± 0.13 cm), mean pressure did not have significant (p = 0.84) effect on flap movement. Increase in pulse pressure resulted in a significant change (p = 0.02) in %TL area (52 ± 4%). The energy acting on the false lumen immediately before propagation was calculated as 75 ± 9 J/m2 and was fairly uniform across different specimens. Pulse pressure had a significant effect on the flap movement in contrast to mean pressure. Hence, mitigation of pulse pressure and restriction of flap movement may be beneficial in patients with type B acute dissections

INFLUENCE OF HEART RATE AND EPICARDIAL STENOSIS SEVERITY ON CARDIAC CONTRACTILITY UNDER CONCOMITANT MICROVASCULAR DISEASE IN A PORCINE MODEL SBC2011-53512

ABSTRACT Invasive guide wire methods to assess functional severity of coronary stenosis are affected by dynamic variables like heart rate (HR), contractility, epicardial stenosis (AS) and blood pressure. The interdependence of these factors is also influenced by the presence of concomitant microvascular disease (CMVD). The purpose of this study is to assess the variation in contractility under varying HR and AS in the presence of CMVD. In vivo experiments were performed on seven Yorkshire pigs. It was found that, in the presence of concomitant microvascular disease (CMVD), for lower AS (&lt;50%) contractility increases for HR&lt;120 bpm while it marginally decreases for HR&gt;120 bpm. However, for higher AS (&gt;50%), contractility decreases for both HR&lt;120 bpm and HR&gt;120 bpm. INTRODUCTON Quantification of the functional significance of epicardial coronary stenosis is important to diagnose heart diseases. In addition, in most clinical cases an obstruction in the coronary microvasculature might also be present under concomitant microvasculature disease, (CMVD) and can affect the clinical diagnostic measurements. Thus, quantification of the combined effect of epicardial and microvascular dysfunction is very much needed. The recent development of Dopplertipped guide wires and pressure monitoring guide wires has facilitated the invasive measurements of coronary flow velocity and distal pressure, thus reviving interest in the invasive physiological assessment of coronary artery disease. However, invasive measurements take place in a dynamic environment involving fluctuating hemodynamic variables like the blood pressure, contractility (CY) of the heart, epicardial stenosis (AS) and the heart rate (HR). To avoid any ambiguity in the evaluation of coronary circulation, the interdependence of these variables need to be clearly delineated. Accordingly, the goal of the present study was to evaluate the influence of changes in HR and AS on the left ventricular CY, measured as the maximum value of the derivative of left ventricular pressure (dp/dt) max METHODS The animal protocol for this study was approved by the University of Cincinnati IACUC and the Cincinnati Children&apos;s Hospital Medical Center. Seven Yorkshire swine (mean wt. 50 ± 3 kg) were premedicated with intramuscular xylazine (2 mg/kg), telazol (7 mg/kg), and atropine (0.05 mg/kg) and anesthesia was maintained with 2% isoflurane and supplemental oxygen. Three surgical accesses were made: 1) the jugular vein access was used to vary the HR by inserting pacing leads (Medtronics Inc., MN) into the right atrium; 2) second access through the carotid artery was used to advance a Millar © solid-tip catheter into the left ventricle, to measure the left ventricular pressure (recorded using Sonometrics system, Ontario, CN); 3) the third access, through the femoral artery, was used to engage a 7-F guiding catheter at the coronary ostium. Access to the left anterior descending (LAD) was achieved using a 0.014&quot; guidewire under fluoroscopy guidance. The lumen crosssectional area was measured using an intravascular ultrasound (IVUS, 2.5-F, 40-MHz) catheter. A 0.014&quot; Combo wire (Volcano Corp., CA) was inserted distal to the balloon to measure pressure and velocity distal to lesion. Based on the artery size, an appropriate Voyager angioplasty balloon of rapid exchange type (Guidant Inc., IN) was introduced over the Doppler flow wire. The balloon was inflated to different diameters to create intraluminal epicardial stenosis of varying severity. Polystyrene microspheres of 90µm (Polysciences Inc., NY) were injected to creat