Clinical Trial Details
— Status: Not yet recruiting
Administrative data
| NCT number |
NCT06007469 |
| Other study ID # |
SP0721 |
| Secondary ID |
|
| Status |
Not yet recruiting |
| Phase |
|
| First received |
|
| Last updated |
|
| Start date |
October 4, 2023 |
| Est. completion date |
December 3, 2024 |
Study information
| Verified date |
August 2023 |
| Source |
Liverpool University Hospitals NHS Foundation Trust |
| Contact |
n/a |
| Is FDA regulated |
No |
| Health authority |
|
| Study type |
Observational [Patient Registry]
|
Clinical Trial Summary
To identify a correlation between Toe Brachial pressure Index (TBPI) and Acceleration time of
the pedal vessels. The aim would then to use this data to design a clinical study assessing
the relationship between PAT and wound healing in patients with PAD.
Description:
The use of ankle brachial pressure index (ABPI) is commonplace in the screening, diagnosis
and management of peripheral vascular disease (PAD). This technique measures and compares the
occlusion pressure of the brachial arteries for comparison with the occlusion pressure of the
tibial arteries at the level of the ankle. The index is then calculated by dividing the
highest of the tibial occlusion pressures by the highest brachial occlusion pressure. In
normal subjects the ABPI should fall between 09-1.3 (1) . A pressure less than 0.9 suggest a
compromise to the peripheral circulation (PAD), with the blood pressure at the ankle level
being lower than in the arm. ABPI results can be erroneous in the presence of medial artery
calcification (MAC) where the ankle arteries are more difficult to compress and hence give
falsely elevated readings. In some patients it can be impossible to occlude the arterial flow
as the vessel is so rigid (1). Conditions that increase the prevalence of MAC are diabetes
mellitus, chronic kidney disease as well as advancing age which also increased the stiffness
of the vessel walls having a similar effect as MAC (2).
When used in isolation as a PAD screening, ABPI can give a normal reading due to undiagnosed
pathological vessel stiffness with studies reporting up to 14-27% of patients returning
normal ABPI results at the same time as low TBPI. (3) Despite the potential pitfall of ABPI,
it is still a widely recognized as its diagnostic limits have been validated in several large
scale studies. (3) However, due to the level of arterial assessment, ABPI does not actually
assess circulation into the foot itself (4). The toe vessels are much less susceptible to
vessel stiffness (3) , and hence deemed are more reliable in such cases when the ABPI would
return a falsely elevated result.
When used alongside detailed duplex imaging of the peripheral arterial tree to give image
guided documentation of vessel calcification, TBPI is a useful indicator of perfusion into
the foot when the ABPI is known not to be indicated. Therefore TBPI measurement has become
the established method for assessing arterial perfusion to the foot, particularly in patients
with risk factors for MAC.
When investigating perfusion into the critically ischaemic limb, ABPI is not indicated and
therefore TBPI is the preferred method. However this becomes problematic when there has been
previous amputation of the forefoot/toes, the patient is in significant pain and/or there is
tissue loss which impedes accurate placement of the equipment on the affected limb.
Furthermore, in a significant number of these patients it is not possible to obtain an
adequate waveform in the toe due to poor arterial perfusion.
To overcome this predicament a novel technique has been developed which involves direct
ultrasound imaging of the pedal vasculature and use the systolic rise time calculated from
the returned waveform analysis as a surrogate for ABPI (4) This systolic rise time, known as
pedal acceleration time (PAT) in foot vessels, has been has been reported to correlate well
with ABPI in patients with compressible vessels and therefore is felt to be a predictor of
wound healing following direct and indirect revascularization. (4) There are, however, a
significant group of patients that attend the vascular department that have risk factors for
MAC which make them unsuitable for ABPI. For this group of patients and those with coexisting
with foot wounds/previous amputation, there is no ratified method for investigation perfusion
pressure.
The aim of this pilot study is to gather information from all patients who present with
significant PAD to investigate a possible link between PAT, ABPI and TBPI and if PAT is a
reliable measurement in patients who fall outside of the group normally excluded.
This would allow objective perfusion information and therefore guide treatment and management
plans.
