Sources of error in intra-arterial pressure measurements across a stenosis

Computed Tomography-Based Assessment of Transvalvular Pressure Gradient in Aortic Stenosis

Background: In patients with aortic stenosis, computed tomography (CT) provides important information about cardiovascular anatomy for treatment planning but is limited in determining relevant hemodynamic parameters such as the transvalvular pressure gradient (TPG).

Purpose: In the present study, we aimed to validate a reduced-order model method for assessing TPG in aortic stenosis using CT data.

Methods: TPG_CT was calculated using a reduced-order model requiring the patient-specific peak-systolic aortic flow rate (Q) and the aortic valve area (AVA). AVA was determined by segmentation of the aortic valve leaflets, whereas Q was quantified based on volumetric assessment of the left ventricle. For validation, invasively measured TPG_catheter was calculated from pressure measurements in the left ventricle and the ascending aorta. Altogether, 84 data sets of patients with aortic stenosis were used to compare TPG_CT against TPG_catheter.

Results: TPG_catheter and TPG_CT were 50.6 ± 28.0 and 48.0 ± 26 mmHg, respectively (p = 0.56). A Bland–Altman analysis revealed good agreement between both methods with a mean difference in TPG of 2.6 mmHg and a standard deviation of 19.3 mmHg. Both methods showed good correlation with r = 0.72 (p < 0.001).

Conclusions: The presented CT-based method allows assessment of TPG in patients with aortic stenosis, extending the current capabilities of cardiac CT for diagnosis and treatment planning.

How to define the hemodynamic significance of an equivocal iliofemoral artery stenosis: Review of literature and outcomes of an international questionnaire

Purpose

The goal of the study was to review current literature regarding the diagnosis of equivocal (50–70%) iliofemoral artery stenosis and compare these findings with the daily practice of an international panel of endovascular experts.

Methods

The Medline Database was searched for relevant publications, and an electronic survey was sent to experts in the field covering the following topics: definition of an equivocal iliofemoral artery stenosis, angiographic visualization and investigation protocols of an equivocal stenosis, intra-arterial pressure measurements, and definition of hemodynamic significance of an equivocal iliofemoral artery stenosis using a physiologic measure.

Results

Of the 37 invited endovascular experts, 21 (53.8%) agreed to participate in the survey. Analysis of existing literature shows that the level of evidence for diagnosing equivocal iliofemoral artery stenosis is mediocre and is not being implemented by experts in the field.

Conclusion

Studies have shown that a stenosis of between 50% and 70% iliofemoral lumen diameter reduction shows a wide range of trans-stenotic pressure gradients. Equivocal iliofemoral artery stenosis can best be identified using three-dimensional quantitative vascular analysis software. Although evidence for a clear hemodynamic cutoff point is weak, performing trans-lesion intra-arterial pressure measurements at rest and during maximal hyperemia is preferred. Diagnosing iliofemoral artery stenosis solely on lumen diameter reduction is inadequate.

Femoral/Axillary Volume Flow Ratio as a New Index for the Assessment of Iliac Atherosclerosis

Objective: To measure the arterial volume flow (VF) with duplex scan, calculate femoral/axillary VF ratio, and discuss its applicability as a new index for the hemodynamic significance of an aorto-iliac occlusive lesion. Methods: Several measures of VF were obtained consecutively with duplex scan in both common femoral and axillary arteries of healthy volunteers with no signs of atherosclerosis and patients with documented evidence of occlusive aorto-iliac disease with segmental pressure measurement. Then the patient group was sent to complimentary evaluation for a second confirmatory examination. Results: There were a total of 635 measures of VF performed in 10 healthy volunteers and 8 patients with severe iliac stenoses or occlusion, 2 of then with bilateral disease. When comparing normal participants and patients with severe iliac stenoses or occlusion, there was statistical significant difference between these 2 groups (P < .01 Mann-Whitney). Similar result was found when comparing patient with diseased limbs with their own contralateral normal side (P < .05 Wilcoxon). And measuring the VF only during the systolic phase was a much more sensitive parameter for differentiating the normal from the diseased. Besides that a good correlation between proximal thigh pressure index and femoral/axillary systolic flow ratio was found in the patient group (P < .01 Spearman correlation). Conclusion: The femoral/axillary VF ratio is useful in assessing the hemodynamic significance of aorto-iliac disease, and the systolic femoral-axillary ratio may also be useful as a follow-up tool.

Estudo comparativo de eco-Doppler com arteriografia na avaliação da doença oclusiva aorto-ilíaca

Contexto: A arteriografia com contraste (AC) tem sido o exame tradicional de avaliação de pacientes com suspeita de doença oclusiva aorto-ilíaca (DOAI). Recentemente, métodos menos invasivos, como a eco-Doppler, têm sido usados com a mesma finalidade. Objetivo: Comparar prospectivamente a eco-Doppler com a AC e eventual manometria arterial direta (MAD) na avaliação pré-operatória de pacientes com suspeita de DOAI. Métodos: Foram submetidos a eco-Doppler e a AC 125 pacientes internados para tratamento de doença arterial oclusiva dos membros inferiores, avaliando comparativamente 552 segmentos da aorta infrarrenal e das artérias ilíacas comum e externa. As lesões encontradas foram classificadas em cinco categorias: 1) normal e estenose leve (0 a 19%); 2) estenose moderada (20 a 49%); 3) estenose significativa (50 a 79%); 4) estenose crítica (80 a 99%); e 5) oclusão total. A MAD foi usada em 19 segmentos de 15 pacientes para classificar lesões limítrofes entre duas categorias. Foram calculados índices de validade (sensibilidade, especificidade, valor preditivo positivo, valor preditivo negativo e acurácia) para distinguir lesões hemodinamicamente significativas de não-significativas e para distinguir estenoses críticas de oclusões. O padrão-ouro foi AC, complementado pela MAD. Foram também calculados coeficientes de correlação kappa entre arteriografias e eco-Doppler para o conjunto dos segmentos aorto-ilíacos. Resultados: Lesões clinicamente relevantes (estenoses de 50 a 99% e oclusões totais) foram observadas na eco-Doppler em 163 segmentos (29,5%) e na AC em 158 segmentos (28,6%). A eco-Doppler mostrou altos índices de validade para distinguir lesões hemodinamicamente significativas de lesões não-significativas em todos os segmentos (acurácia = 92%; kappa = 0,81) e para diferenciar estenoses críticas de oclusões (acurácia = 86%; kappa = 0,73). Os índices de correlação entre os resultados das eco-Doppler e das AC foram ótimos em todos os segmentos aorto-ilíacos. Conclusão: A eco-Doppler apresenta elevados índices de validade e ótimos coeficientes de correlação com a AC na avaliação de pacientes com suspeita de DOAI.

Guidelines for the Reporting of Renal Artery Revascularization in Clinical Trials

Although the treatment of atherosclerotic renal artery stenosis with use of percutaneous angioplasty, stent placement, and surgical revascularization has gained widespread use, there exist few prospective randomized controlled trials (RCTs) comparing these techniques to each other or against the standard of medical management alone. To facilitate this process as well as help answer many important questions regarding the appropriate application of renal revascularization, well-designed and rigorously conducted trials are needed. These trials must have clearly defined goals and must be sufficiently sized and performed so as to withstand intensive outcomes assessment. Toward this end, this document provides guidelines and definitions for the design, conduct, evaluation, and reporting of renal artery revascularization RCTs. In addition, areas of critically necessary renal artery revascularization investigation are identified. It is hoped that this information will be valuable to the investigator wishing to conduct research in this important area.

Guidelines for the reporting of renal artery revascularization in clinical trials

Although the treatment of atherosclerotic renal artery stenosis with use of percutaneous angioplasty, stent placement, and surgical revascularization has gained widespread use, there exist few prospective randomized controlled trials (RCTs) comparing these techniques to each other or against the standard of medical management alone. To facilitate this process as well as help answer many important questions regarding the appropriate application of renal revascularization, well-designed and rigorously conducted trials are needed. These trials must have clearly defined goals and must be sufficiently sized and performed so as to withstand intensive outcomes assessment. Toward this end, this document provides guidelines and definitions for the design, conduct, evaluation, and reporting of renal artery revascularization RCTs. In addition, areas of critically necessary renal artery revascularization investigation are identified. It is hoped that this information will be valuable to the investigator wishing to conduct research in this important area.

Gadolinium-enhanced magnetic resonance angiography, digital subtraction angiography and duplex of the iliac arteries compared with intra-arterial pressure gradient measurements

PURPOSE

to compare gadolinium-enhanced magnetic resonance angiography (Gd-MRA), digital subtraction angiography (DSA) and duplex of the iliac arteries with intra-arterial pressure gradient measurement as the reference method.

MATERIALS AND METHODS

Gd-MRA, DSA and duplex examinations of the iliac arteries were performed in 30 patients (60 arteries) with lower-limb arterial occlusive disease. In 29 arteries, pressure measurements were made (n=25) or the artery was found to be occluded on catheterisation (n=4). An aortofemoral peak systolic pressure gradient of 20 mmHg or more was regarded as haemodynamically significant. Stenoses with a diameter reduction of 50% or more on MRA or DSA, or an increase in peak systolic velocity greater than 150% (duplex) were considered significant. MRA examinations were evaluated by means of maximum intensity projections (MRA-MIP) and using source images and curved multiplanar reconstruction (MRA-MPR).

RESULTS

the sensitivity (specificity) for a significant iliac artery stenosis were 81% (75%) for MRA-MIP, 76% (75%) for MRA-MPR, 86% (88%) for DSA, and 72% (88%) for duplex.

CONCLUSION

with intra-arterial pressure measurements as the reference method, similar results were achieved with Gd-MRA, DSA and duplex concerning the detection of haemodynamically significant iliac artery stenoses. The use of source images and multiplanar reconstructions resulted in higher accuracy for the detection of occlusions.