Angiographic Features and Clinical Outcomes of Balloon Uncrossable Lesions during Chronic Total Occlusion Percutaneous Coronary Intervention

Background: Balloon uncrossable lesions are defined as lesions that cannot be crossed with a balloon after successful guidewire crossing. Methods: We analyzed the association between balloon uncrossable lesions and procedural outcomes of 8671 chronic total occlusions (CTOs) percutaneous coronary interventions (PCIs) performed between 2012 and 2022 at 41 centers. Results: The prevalence of balloon uncrossable lesions was 9.2%. The mean patient age was 64.2 ± 10 years and 80% were men. Patients with balloon uncrossable lesions were older (67.3 ± 9 vs. 63.9 ± 10, p \u3c 0.001) and more likely to have prior coronary artery bypass graft surgery (40% vs. 25%, p \u3c 0.001) and diabetes mellitus (50% vs. 42%, p \u3c 0.001) compared with patients who had balloon crossable lesions. In-stent restenosis (23% vs. 16%. p \u3c 0.001), moderate/severe calcification (68% vs. 40%, p \u3c 0.001), and moderate/severe proximal vessel tortuosity (36% vs. 25%, p \u3c 0.001) were more common in balloon uncrossable lesions. Procedure time (132 (90, 197) vs. 109 (71, 160) min, p \u3c 0.001) was longer and the air kerma radiation dose (2.55 (1.41, 4.23) vs. 1.97 (1.10, 3.40) min, p \u3c 0.001) was higher in balloon uncrossable lesions, while these lesions displayed lower technical (91% vs. 99%, p \u3c 0.001) and procedural (88% vs. 96%, p \u3c 0.001) success rates and higher major adverse cardiac event (MACE) rates (3.14% vs. 1.49%, p \u3c 0.001). Several techniques were required for balloon uncrossable lesions. Conclusion: In a contemporary, multicenter registry, 9.2% of the successfully crossed CTOs were initially balloon uncrossable. Balloon uncrossable lesions exhibited lower technical and procedural success rates and a higher risk of complications compared with balloon crossable lesions

Increased Inlet Blood Flow Velocity Predicts Low Wall Shear Stress in the Cephalic Arch of Patients with Brachiocephalic Fistula Access

Background: An autogenous arteriovenous fistula is the optimal vascular access for hemodialysis. In the case of brachiocephalic fistula, cephalic arch stenosis commonly develops leading to access failure. We have hypothesized that a contribution to fistula failure is low wall shear stress resulting from post-fistula creation hemodynamic changes that occur in the cephalic arch. Methods: Twenty-two subjects with advanced renal failure had brachiocephalic fistulae placed. The following procedures were performed at mapping (pre-operative) and at fistula maturation (8–32 weeks post-operative): venogram, Doppler to measure venous blood flow velocity, and whole blood viscosity. Geometric and computational modeling was performed to determine wall shear stress and other geometric parameters. The relationship between hemodynamic parameters and clinical findings was examined using univariate analysis and linear regression. Results: The percent low wall shear stress was linearly related to the increase in blood flow velocity (p Conclusions: The curvature and hemodynamic changes during fistula maturation increase the percentage of low wall shear stress regions within the cephalic arch. Low wall shear stress may contribute to subsequent neointimal hyperplasia and resultant cephalic arch stenosis. If this hypothesis remains tenable with further studies, ways of protecting the arch through control of blood flow velocity may need to be developed.</p

Increased Inlet Blood Flow Velocity Predicts Low Wall Shear Stress in the Cephalic Arch of Patients with Brachiocephalic Fistula Access

<div><p>Background</p><p>An autogenous arteriovenous fistula is the optimal vascular access for hemodialysis. In the case of brachiocephalic fistula, cephalic arch stenosis commonly develops leading to access failure. We have hypothesized that a contribution to fistula failure is low wall shear stress resulting from post-fistula creation hemodynamic changes that occur in the cephalic arch.</p><p>Methods</p><p>Twenty-two subjects with advanced renal failure had brachiocephalic fistulae placed. The following procedures were performed at mapping (pre-operative) and at fistula maturation (8–32 weeks post-operative): venogram, Doppler to measure venous blood flow velocity, and whole blood viscosity. Geometric and computational modeling was performed to determine wall shear stress and other geometric parameters. The relationship between hemodynamic parameters and clinical findings was examined using univariate analysis and linear regression.</p><p>Results</p><p>The percent low wall shear stress was linearly related to the increase in blood flow velocity (<i>p</i> < 0.01). This relationship was more significant in non-diabetic patients (<i>p</i> < 0.01) than diabetic patients. The change in global measures of arch curvature and asymmetry also evolve with time to maturation (<i>p</i> < 0.05).</p><p>Conclusions</p><p>The curvature and hemodynamic changes during fistula maturation increase the percentage of low wall shear stress regions within the cephalic arch. Low wall shear stress may contribute to subsequent neointimal hyperplasia and resultant cephalic arch stenosis. If this hypothesis remains tenable with further studies, ways of protecting the arch through control of blood flow velocity may need to be developed.</p></div

Scatterplots depicting the relationship between weeks since access placement and Global Curvature or Global Asymmetry.

<p>Time since access placement (weeks) is shown on the <i>x</i>-axis and change in Global Curvature and Global Asymmetry are shown on the <i>y</i>-axis. Changes in Global Curvature (left panel) and Global Asymmetry (right panel) increase with time since the fistula was placed (<i>p</i> < 0.05). The relationship did not differ significantly in patients with diabetes (closed circles) compared to those without diabetes (open circles) (<i>p</i> < 0.05).</p

Scatterplot depicting the relationship of blood flow velocity and WSS at maturation.

<p>Maximum blood flow velocity (cm/sec) is shown on the <i>x</i>-axis and percent low wall shear stress is shown on the <i>y</i>-axis. Blood flow velocity is correlated with changes in low wall shear stress (solid line) (<i>p</i> < 0.05). The patients with diabetes are represented by closed circles, the patients without diabetes by open circles with significant correlation in non-diabetics (<i>p</i> < 0.05).</p

Computational flow plot of cephalic arch.

<p>Terminal cephalic arch with inflow from right to left. Critical wall shear regions (< 0.076 Pa) are denoted with bold, red lines and are superimposed on streamlines. Computational flow plot for subject 7 at baseline (Panel A) and 30 weeks (Panel B). Computational flow plot for subject 2 at baseline (Panel C) and 8 weeks (Panel D). Black arrow on Panel D shows tiny area of low wall shear stress.</p

Subject Characteristics.

<p>Subject Characteristics.</p

Schematic of hypothesis.

<p>Arteriovenous fistula (AVF) creation leads to high blood flow velocity (BFV) diverted into the curved cephalic arch (Panel A black arrow shows normal curved cephalic arch). Low wall shear stress (WSS) (bold red on upper and lower wall) causes recirculation areas represented in Panel B (red arrow). Low WSS will eventually cause excessive neointimal hyperplasia (NH) and resultant cephalic arch stenosis (CAS) (Panel B black arrow).</p

Wall shear stress at mapping in 12 subjects.

<p>WSS (log <i>Pa</i>) at mapping for 12 subjects. Within-patient log-transformed wall shear stress values in the upper (dark grey) and lower wall (light grey). Red reference lines show the normal range on the original scale log scale [log(0.076)-log(0.76)].</p