Lesion Eccentricity Plays a Key Role in Determining the Pressure Gradient of Serial Stenotic Lesions: Results from a Computational Hemodynamics Study

PURPOSE

In arterial disease, the presence of two or more serial stenotic lesions is common. For mild lesions, it is difficult to predict whether their combined effect is hemodynamically significant. This study assessed the hemodynamic significance of idealized serial stenotic lesions by simulating their hemodynamic interaction in a computational flow model.

MATERIALS AND METHODS

Flow was simulated with SimVascular software in 34 serial lesions, using moderate (15 mL/s) and high (30 mL/s) flow rates. Combinations of one concentric and two eccentric lesions, all 50% area reduction, were designed with variations in interstenotic distance and in relative direction of eccentricity. Fluid and fluid-structure simulations were performed to quantify the combined pressure gradient.

RESULTS

At a moderate flow rate, the combined pressure gradient of two lesions ranged from 3.8 to 7.7 mmHg, which increased to a range of 12.5-24.3 mmHg for a high flow rate. Eccentricity caused an up to two-fold increase in pressure gradient relative to concentric lesions. At a high flow rate, the combined pressure gradient for serial eccentric lesions often exceeded the sum of the individual lesions. The relative direction of eccentricity altered the pressure gradient by 15-25%. The impact of flow pulsatility and wall deformability was minor.

CONCLUSION

This flow simulation study revealed that lesion eccentricity is an adverse factor in the hemodynamic significance of isolated stenotic lesions and in serial stenotic lesions. Two 50% lesions that are individually non-significant can combine more often than thought to hemodynamic significance in hyperemic conditions.

Intra-arterial Fractional Flow Reserve Measurements Provide an Objective Assessment of the Functional Significance of Peripheral Arterial Stenoses

OBJECTIVE

Peripheral arterial stenoses (PAS) are commonly investigated with duplex ultrasound (DUS) and angiography, but these are not functional tests. Fractional flow reserve (FFR), a pressure based index, functionally assesses the ischaemic potential of coronary stenoses, but its utility in PAS is unknown. FFR in the peripheral vasculature in patients with limb ischaemia was investigated.

METHODS

Patients scheduled for angioplasty and or stenting of isolated iliac and superficial femoral artery stenoses were recruited. Resting trans-lesional pressure gradient (Pd/Pa) and FFR were measured after adenosine provoked hyperaemia using an intra-arterial 0.014 inch flow and pressure sensing wire (ComboWire XT, Philips). Prior to revascularisation, exercise ABPI (eABPI) and DUS derived peak systolic velocity ratio (PSVR) of the index lesion were determined. Calf muscle oxygenation was measured using blood oxygenation level dependent cardiovascular magnetic resonance prior to and after revascularisation.

RESULTS

Forty-one patients (32, 78%, male, mean age 65 ± 11 years) with 61 stenoses (iliac 32; femoral 29) were studied. For lesions < 80% stenosis, resting Pd/Pa was not influenced by the degree of stenosis (p = .074); however, FFR was discriminatory, decreasing as the severity of stenosis increased (p = .019). An FFR of < 0.60 was associated with critical limb threatening ischaemia (area under the curve [AUC] 0.87; 95% CI 0.75 - 0.95), in this study performing better than angiographic % stenosis (0.79; 0.63 - 0.89), eABPI (0.72; 0.57 - 0.83), and PSVR (0.65; 0.51 - 0.78). FFR correlated strongly with calf oxygenation (rho, 0.76; p < .001). A greater increase in FFR signalled resolution of symptoms and signs (ΔFFR 0.25 ± 0.15 vs. 0.13 ± 0.09; p = .009) and a post-angioplasty and stenting FFR of > 0.74 predicted successful revascularisation (combined sensitivity and specificity of 95%; AUC 0.98; 0.91 - 1.00).

CONCLUSION

This pilot study demonstrates that FFR can objectively measure the functional significance of PAS that compares favourably with visual and DUS based assessments. Its role as a quality control adjunct that confirms optimal vessel patency after angioplasty and or stenting also merits further investigation.

Peripheral Arterial Disease: A Narrative Review

Peripheral arterial disease (PAD) describes the partial or complete occlusion of blood flow in the distal arteries of the body. A decreased arterial patency may occur due to a reduction in the elasticity or diameter of the vessel. The goal of interventions is to decrease incidence and reduce complications by identifying and minimizing the primary causes. This paper discusses PAD affecting the aortoiliac, common femoral, and femoropopliteal arteries. In a significant portion of the population, PAD may lack usual symptoms such as limb pain, claudication, and diminished pulses. Imaging techniques become crucial to ensuring timely diagnosis, monitoring treatment effectiveness, and preventing recurrence. Duplex ultrasound (DUS) is a cheap and non-invasive preliminary technique to detect atherosclerotic plaques and grade arterial stenosis. Magnetic resonance angiography (MRA) provides the added advantage of minimizing artifacts. Digital subtraction angiography (DSA) remains the gold standard for grading the degree of stenosis but is only employed second-line to DUS or MRA due to the high dose of nephrotoxic contrast. Computed tomography angiography (CTA) is able to overcome the anatomical limitations of DUS and MRA and proves to be a suitable alternative to DSA in patients with renal disease. Preventative measures involve monitoring blood pressure, cholesterol levels, and tobacco usage. First-line treatment options include endovascular procedures as well as surgical interventions in cases of significant arterial involvement. Endovascular treatments involve the use of balloon angioplasty, drug-coated balloons, and drug-coated stents, to name a few, that serve as minimally invasive techniques to manage PAD. Surgical procedures, although more complex, are considered gold-standard treatment options for long and intricate lesions. Endovascular methods are generally preferred over surgical options as the complication risk is severely reduced and the rates of reintervention are comparable to surgical options.

Quantitative Techniques of Ultrasonography in the Assessment of Femoropopliteal Atherosclerotic Lesions Using Peak Systolic Velocity Ratio: Results From the TURN-UP Study

PURPOSE

Duplex ultrasound (DUS)-measured peak systolic velocity ratios (PSVRs) are commonly used to evaluate arterial stenosis in lower extremity artery disease (LEAD). However, these measurement methods have not yet been standardized. This study aimed to reveal the influence of measuring methods on PSVR values.

METHODS

A 132 femoropopliteal lesions with PSVR ranging from 1.5 to 3.5 evaluated using method A (angle correction 60°, the direction of blood flow, the no or few atherosclerotic changes closest to the lesion proximal side was defined as the nonstenotic area) were included. The following 4 different methods were then compared with method A: method B, angle correction 45°; method C, angle correction 60° measured along the vessel wall; D, angle correction 60°, with the nonstenotic area the lowest peak systolic velocity area; and E, angle correction 60°, with the reference point fixed at 2 cm proximal to the target lesion area. The difference in PSVR values was analyzed using the Bland-Altman method.

RESULTS

The mean PSVR value measured by method A was 2.27±0.51, those measured by methods B, C, D, and E were 2.21±0.55, 2.31±0.66, 2.34±0.63, and 2.11±0.63, respectively. The 95% prediction intervals of the differences in PSVR measurements versus A were -0.64 to +0.53 for method B, -0.59 to +0.68 for method C, -0.77 to +0.91 for method D, and -1.12 to +0.79 for method E.

CONCLUSION

PSVR values considerably differed between measuring methods. PSVR values by DUS are largely dependent on the measurement methods, which could considerably affect the judgment of LEAD.

CLINICAL IMPACT

Due to differences in several DUS measurement methods, the PSVR results could be changed. Therefore, to need further investigations and unification of measurement method.

Impact of Peak Systolic Velocity Ratio after Drug-Coated Balloon for Femoropopliteal Disease: Three-Month Serial Observation Vessel Echo Study

AIM

No flow-limiting dissection after drug-coated balloon (DCB) treatment for femoropopliteal (FP) lesions is considered as one of the endpoints, but it has not investigated the difference between each vessel dissection. This study aimed to clarify whether there is a difference between no dissection and type C dissection without flow-limiting dissection for 3 months by peak systolic velocity ratio (PSVR) based on duplex ultrasonography.

METHODS

Between February 2020 and April 2021, 44 consecutive de novo FP diseases that underwent endovascular therapy (EVT) with DCB were enrolled in this study. 65.9% of the patients had intermittent claudication, and mean lesion lengths were 194±107 mm. The chronic total occlusion was 38.6%. After DCB treatment, vessel dissection pattern was categorized by angiography. The minimum lumen area (MLA) identified by intravascular ultrasound was serially evaluated with PSVRs at 1 day, 1 month, and 3 months after EVT.

RESULT

All lesions were treated with DCB without provisional stents. The vessel dissection pattern after DCB treatment showed that types D, E, and F were not observed, 9% were no dissection, 27% were type A, 32% were type B, and 32% were type C. In all cases, the PSVR values of MLA site were less than 2.6 at 3 months, and there were no significant differences between no dissection and type C dissection.

CONCLUSION

Up to dissection pattern "C" is considered acceptable as one of the endpoints to determine the need for provisional stenting after DCB treatment.

Long-term results of the Japanese multicenter Viabahn trial of heparin bonded endovascular stent grafts for long and complex lesions in the superficial femoral artery

OBJECTIVE

To assess the long-term safety and efficacy of endovascular stent grafting to treat long, complex lesions in the superficial femoral artery (SFA).

METHODS

This prospective, multicenter study at 15 Japanese hospitals assessed heparin bonded stent grafts for treating long SFA lesions in patients with symptomatic peripheral arterial disease. Inclusion criteria were Rutherford category 2-5 symptoms (grade 5 without active infection), ankle-brachial index (ABI) ≤ 0.9, and SFA lesions ≥ 10 cm with ≥ 50% stenosis. The key efficacy and safety outcomes were primary-assisted patency (PAP) and adverse events through 24 months, respectively. Secondary outcomes included primary patency (PP), secondary patency, freedom from target lesion revascularization (fTLR), and VascuQOL scoring.

RESULTS

Of 103 subjects (mean age 74.2 ± 7.0 years; 82.5% male), 100 (97.1%) had intermittent claudication. Average lesion length was 21.8 ± 5.8 cm; 87 lesions (84.5%) were TASC C/D classification (65.7% chronic total occlusions). Ninety-two subjects and 61 subjects were evaluable through 24 months and 60 months, respectively. At 24 months, the Kaplan-Meier-estimated PAP rate was 85.7% (95% CI: 76.3‒91.5%), PP rate was 78.8% (95% CI: 68.8‒85.9%), and secondary patency rate was 92.0% (95% CI: 82.4-96.5%). Mean ABI was 0.64 ± 0.12 at baseline and 0.94 ± 0.19 at 24 months (P<.0001). At 24 months, fTLR was 87.2% (95% CI: 78.9-92.3%), and at 60 months, fTLR was 79.1% (95% CI: 67.9-86.8%). No device or procedure-related life- or limb-threatening critical events or acute limb ischemia cases were observed through 5 years. No stent fractures were detected in annually scheduled follow-up x-rays. Scores from the VascuQOL and Walking Impairment Questionnaire were significantly increased at 1 month through 24 months versus baseline values (P<.0001 for both). One subject was converted to open bypass through 5 years.

CONCLUSIONS

Stent grafting of long and complex SFA lesions in claudicant patients is safe and effective through long-term follow-up, with 79.1% fTLR and no study leg amputation, acute limb ischemia, or stent fractures through 5 years.

Peak systolic velocity ratio derived from quantitative vessel analysis for restenosis after femoropopliteal intervention: a multidisciplinary review from Endovascular Asia

With technological improvements in the endovascular armamentarium, there have been tremendous advances in catheter-based femoropopliteal artery intervention during the last decade. However, standardization of the methodology for assessing outcomes has been underappreciated, and unvalidated peak systolic velocity ratios (PSVRs) of 2.0, 2.4, and 2.5 on duplex ultrasonography have been arbitrarily but routinely used for assessing restenosis. Quantitative vessel analysis (QVA) is a widely accepted method to identify restenosis in a broad spectrum of cardiovascular interventions, and PSVR needs to be validated by QVA. This multidisciplinary review is intended to disseminate the importance of QVA and a validated PSVR based on QVA for binary restenosis in contemporary femoropopliteal intervention.

Edge Stenosis After Covered Stenting for Long Superficial Femoral Artery Occlusive Disease: Risk Factor Analysis and Prevention With Drug-Coated Balloon Angioplasty

Purpose: To report a retrospective analysis of risk factors for edge restenosis after Viabahn stent-graft treatment of superficial femoral artery (SFA) occlusive disease and determine any protective effect of drug-coated balloons (DCBs) used at the time of stent-graft implantation. Methods: Between October 2011 and July 2016, 110 patients (mean age 73.3±7.6 years; 78 men) were treated with the Viabahn stent-graft for long SFA occlusions. Thirty-eight (34.5%) patients had DCB reinforcement at the distal edge of the stent-graft. For analysis, the population was divided into groups of no edge stenosis patients (n=88; mean lesion length 22.4±4.2 cm) and edge stenosis patients (n=22; mean lesion length 23.5±5.7 cm). The clinical outcomes, ankle-brachial indices, computed tomography angiography findings, and patency were compared at a minimum of 12 months. Logistic regression analysis was employed to determine risk factors for edge stenosis; the results are presented as the odds ratio (OR) and 95% confidence interval. Results: No differences in clinical or procedural characteristics were identified except the higher incidence of diabetes (p=0.008) and greater need for retrograde access (p=0.033) in the edge stenosis group. DCB reinforcement reduced the incidence of edge stenosis (p=0.021) and target lesion revascularization (TLR; p=0.010) and resulted in a significantly higher 1-year primary patency rate (92.1% vs 76.4%, p=0.042). However, multivariate analysis revealed only poor distal runoff (OR 0.31, 95% CI 0.11 to 0.83, p=0.020) as a predictor of edge stenosis. Conclusion: The risk of edge stenosis after Viabahn implantation was higher in patients with poor distal runoff. DCB reinforcement over the distal edge reduced edge stenosis, decreased 1-year TLR, and improved 1-year primary patency.