Bidirectional perforators in the lower limb are not physiologically normal: A brief commentary.

The suggestion that bidirectional flow is a normal feature seen in venous perforators of the lower leg has been a longstanding debate. Newer published evidence has changed the perspective on normal perforator flow and is presented here to resolve the misunderstandings and different viewpoints previously held.

The correlation between different ultrasound planes and computed tomography measures of abdominal aortic aneurysms.

Introduction: Ultrasound measurements of the aorta are typically taken in the axial plane, with the transducer perpendicular to the aorta, and diameter measurements are obtained by placing the callipers from the anterior to the posterior wall and the transverse right to the left side of the aorta. While the 'conventional' anteroposterior walls in both sagittal and transverse plains may be suitable for aneurysms with less complicated geometry, there is controversy regarding the suitability of this approach for complicated, particularly tortuous aneurysms, as they may offer a more challenging situation. Previous work undertaken within our research group found that when training inexperienced users of ultrasound, they demonstrated more optimal calliper placement to the abdominal aorta when approached from a decubitus window to obtain a coronal image compared to the traditional ultrasound approach. Purpose: To observe the level of agreement in real-world reporting between computed tomography (CT) and ultrasound measurements in three standard planes; transverse AP, sagittal AP and coronal (left to right) infra-renal abdominal aortic aneurysm (AAA) diameter. Methodology: This is a retrospective review of the Otago Vascular Diagnostics database for AAA, where ultrasound and CT diameter data, available within 90 days of each other, were compared. In addition to patient demographics, the infrarenal aorta ultrasound diameter measurements in transverse AP and sagittal AP, along with a coronal decubitus image of the aorta was collected. No transverse measurement was performed from the left to the right of the aorta. Results: Three hundred twenty-five participants (238 males, mean age 76.4 ± 7.5) were included. Mean ultrasound outer to the outer wall, transverse AP and sagittal AP diameters were 48.7 ± 10.5 mm and 48.9 ± 9.9 mm, respectively. The coronal diameter measurement of the aorta from left to right was 53.9 ± 12.8 mm in the left decubitus window. The mean ultrasound max was 54.3 ± 12.6 mm. The mean CT diameter measurement was 55.6 ± 12.7 mm. Correlation between the CT max and ultrasound max was r 2 = 0.90, and CT with the coronal measurement r 2 = 0.90, CT and AP transverse was r2=0.80, and CT with AP sagittal measurement was r 2 = 0.77. Conclusion: The decubitus ultrasound window of the abdominal aorta, with measurement of the coronal plane, is highly correlated and in agreement with CT scanning. This window may offer an alternative approach to measuring the infrarenal abdominal aortic aneurysm and should be considered when performing surveillance of all infra-renal AAA.

Near Infrared Fluorescence Imaging to Demonstrate Reflux in the Superficial Microvenous Network of the Leg.

OBJECTIVE: Reflux within the superficial microvenous network may play a critical role in the development of skin changes which can be associated with chronic venous insufficiency. This study aimed to determine if near infrared fluorescence (NIRF) imaging could be used to accurately determine superficial venous reflux in the leg. METHODS: A total of nine limbs were examined ex vivo from patients undergoing limb amputation for peripheral arterial disease. Cannulation of the distal great saphenous vein was used to sequentially perform Xray contrast enhanced venography, NIRF imaging, and venous corrosion casts. RESULTS: Fluorescence imaging visualised a range of different microvenous reflux patterns ex vivo, which were generally not evident by Xray venography but were consistent with retrograde resin vascular casts. These included both focal and diffuse regions of fluorescence within the skin and, consistent with previous observations, the vascular casts indicated that regions of venous reflux were typically associated with incompetent valves. CONCLUSION: The findings from this study suggest a potential method for investigating early stage superficial venous disease, prior to the appearance of visible signs of advanced venous disease, such as skin changes. However, further studies are required to confirm the in vivo clinical utility of these observations.

The lower limb perforator veins in normal subjects.

OBJECTIVE: With the developments in vascular ultrasound technology, the opportunity has arisen to examine in greater detail the distribution and behavior of the perforators in normal lower limbs and the implications in understanding their normal role. METHODS: The lower limbs of 20 healthy participants free of any cardiovascular or venous disease were examined. The anatomical characteristics and distribution as well as the functional features of all ultrasound-detectable lower limb venous perforators were evaluated in these normal limbs. Perforator flow was tested at rest, supine, sitting, standing, and with exercise. Comparisons were made between standard augmentation and isometric foot plantar flexion. RESULTS: Twenty individuals (13 females, 7 males; mean age, 36.9 ± 12 years) participated in the study. On average each limb had 14.2 (range, 8-21) perforators identified by ultrasound examination, with an average size of 1.3 ± 0.56 mm (range, 0.4-3.5 mm), most in the medial calf and those in the lower third were larger. On ultrasound examination, the valves were observed only within these larger direct perforators (17%; 18/105). All maneuvers resulted in flow which was only from superficial to the deep system and no two-way flow was observed. Spontaneous flow at rest occurred in a small proportion, but treadmill walking led to the recruitment of most perforators with spontaneous pulsatile flow at greatly increased velocities. The estimated total perforator volume flow could be increased by up to five-fold and accounting for as much as 80 mL/min in a leg. Isometric foot plantar flexion stopped any spontaneous flow and, on relaxation, resulted in a reproduceable short burst of inflow in the calf perforators. Augmentation by calf or foot cuff compression produced a brief variable inward, flow but this flow did not correlate with the perforator flow, with the more physiological maneuvers of isometric foot plantar flexion and exercise. CONCLUSIONS: This study has shown that normal perforator veins in the leg are unidirectional from superficial to deep veins. Although few perforators have spontaneous flow at rest, most are recruited with exercise to substantially increase spontaneous perforator flow secondary to the increased skin blood flow. The augmentation maneuver is not comparable with more physiological activity. These normal features should be taken into account in the assessment of the abnormal perforator.

Accuracy and repeatability of the Dopplex Ability.

BACKGROUND: Ankle-brachial index (ABI) and pulse volume recordings (PVR) are non-invasive tests used in diagnosis of peripheral arterial disease (PAD). The Dopplex Ability is an automated ABI/PVR device utilising air plethysmography, offering easy and rapid PAD diagnosis. The accuracy and repeatability of the Dopplex were assessed in comparison to the Doppler/air plethysmography-based Parks Flo-Lab system. METHODS: Sixty-six patients (n = 129 lower limbs) were assessed with both Dopplex and Parks systems. For Dopplex ABI and PVR to be deemed accurate, it had to be within ±10% of the Parks ABI, and the PVR grade (1-4) had to be equal. The coefficient of variation (CV) was calculated from three repeat ABI/PVR readings to assess repeatability. RESULTS: The Dopplex and Parks devices correlated poorly for ABI (R2 = 0.17) with only 43% of ABIs and 69% of PVRs meeting the accuracy criteria compared to the Parks values. The specificity and sensitivity were 56% and 82%, respectively for ABI, and 91% and 89%, respectively for PVRs. The Dopplex showed a significantly higher CV for both ABIs and PVRs compared to the Parks. CONCLUSION: We found the Dopplex device to demonstrate suboptimal accuracy and repeatability in assessing ABI/PVR, and it was deemed unsuitable for use in our community.

Microvenous Reflux in the Skin of Limbs with Superficial Venous Incompetence.

This study investigated whether microvenous reflux can be detected in limbs with chronic venous disease using superb microvascular imaging (SMI) and colour Doppler imaging. Participants with venous disease (limbs, n = 26) and without venous disease (limbs, n = 10) were studied. The skin in the medial gaiter region was imaged using both SMI and colour Doppler to identify reflux in the small vessels in response to distal augmentation. The diameters and depths of responsive vessels were measured. In limbs with venous disease, reflux in response to provocation was visualised with SMI in a greater number of vessels (12/26 versus 4/26) and smaller vessels than with colour Doppler. Reflux in the superficial skin veins was demonstrated in one control participant (1/10) using SMI and in none using colour Doppler (0/10). Our study indicates that microvenous reflux is demonstrable in limbs with venous disease and that SMI is more sensitive than colour Doppler.

Technical recommendations for the use of carotid duplex ultrasound for the assessment of extracranial blood flow.

Duplex ultrasound is an evolving technology that allows the assessment of volumetric blood flow in the carotid and vertebral arteries during a range of interventions along the spectrum of health and chronic disease. Duplex ultrasound can provide high-resolution diameter and velocity information in real-time and is noninvasive with minimal risks or contraindications. However, this ultrasound approach is a specialized technique requiring intensive training and stringent control of multiple complex settings; results are highly operator-dependent, and analysis approaches are inconsistent. Importantly, therefore, methodological differences can invalidate comparisons between different imaging modalities and studies; such methodological errors have potential to discredit study findings completely. The task of this review is to provide the first comprehensive, user-friendly technical guideline for the application of duplex ultrasound in measuring extracranial blood flow in human research. An update on recent developments in the use of edge-detection software for offline analysis is highlighted, and suggestions for future directions in this field are provided. These recommendations are presented in an attempt to standardize measurements across research groups and, hence, ultimately to improve the accuracy and reproducibility of measuring extracranial blood flow both within subjects and between groups.

Reliability of contrast-enhanced ultrasound for the assessment of muscle perfusion in health and peripheral arterial disease.

We investigated the reliability of contrast-enhanced ultrasound (CEUS) in assessing calf muscle microvascular perfusion in health and disease. Response to a post-occlusive reactive hyperaemia test was repeated on two occasions >48 h apart in healthy young (28 ± 7 y) and elderly controls (70 ± 5 y), and in peripheral arterial disease patients (PAD, 69 ± 7 y; n = 10, 9 and 8 respectively). Overall, within-individual reliability was poor (coefficient of variation [CV] range: 15-87%); the most reliable parameter was time to peak (TTP, 15-48% CV). Nevertheless, TTP was twice as long in elderly controls and PAD compared to young (19.3 ± 10.4 and 22.0 ± 8.6 vs. 8.9 ± 6.2 s respectively; p < 0.01), and area under the curve for contrast intensity post-occlusion (a reflection of blood volume) was ∼50% lower in elderly controls (p < 0.01 versus PAD and young). Thus, CEUS assessment of muscle perfusion during reactive hyperaemia demonstrated poor reliability, yet still distinguished differences between PAD patients, elderly and young controls.