The accuracy and reliability of current angiographic assessment methods for identification of significant dissections during endovascular treatment of femoropopliteal arterial disease

This is an observational study to investigate the performance of different methods of assessing post-angioplasty dissection severity during endovascular intervention to treat occlusive lesions in the femoropopliteal arteries. This will include investigation of how the intra-procedural assessment methods relate to one another, the reliability of each method, and which methods are most likely to identify severe dissections, i.e. ones that develop restenosis or require re-intervention. The incidence of severe dissection post angioplasty will be measured and binary restenosis and re-intervention rates will be assessed based on regular clinical and imaging follow-up. The endovascular intervention will be performed following standard practice at the host institution by vascular surgeon or interventional radiologist with experience in endovascular therapy. Treatment decisions related to post-angioplasty dissection will be made at the treating surgeon discretion and will be based on subjective assessment of angiography and intravascular ultrasound (IVUS) imaging as these are standard imaging techniques used routinely during these procedures at the host institution. Dissection severity assessment will be based on evidence of flow limitation and/or residual stenosis at the dissection. The following intra-procedural assessment methods will be used during the endovascular procedure but not be available to the treating surgeon: quantitative vessel analysis (QVA) of pre and post-angioplasty angiography images to measure the reference vessel diameter and maximum residual stenosis; IVUS measurement of reference vessel diameter, minimum lumen area, dissection arc and maximum residual stenosis; pressure gradient (in mmHg) across the treatment zone using a pressure wire; and duplex ultrasound peak systolic velocity ratio (PSVr) across the treatment zone. This data will be collected at the time of procedure and require no input from the participant. The addition of pressure and duplex assessments will add less than 10 minutes to total procedure time (i.e. <10% of the typical total procedure time of 2 hours). Angiography imaging utilises diagnostic x-ray imaging and non-ionic contrast media. This imaging is required for normal treatment and no additional contrast or radiation will be required for this study. There are no risks to use of the IVUS catheter or the pressure wire. Pre-treatment data collected includes patient demographics, risk factors, relevant patient medical history and assessment of clinical severity (Rutherford score and ankle brachial pressure index). A quality of life assessment tool (AUSVIQOL) will be completed at this time. Total time involved will be no more than 10 minutes. Data collection will be undertaken by one the principal investigator or a research assistant with at least 5 years’ experience in the care of vascular disorders. Standard clinical assessment and imaging follow-up of patients will be performed at three, six and 12 months after the endovascular procedure. Standard clinical assessment will involve an outpatient assessment by the clinical team, by vascular medical and nursing staff, and completion of the quality of life tool by one the principal investigator or a research assistant with at least 5 years’ experience in the care of vascular disorders. Imaging assessment will involve a duplex ultrasound scan of the treated limb to assess for evidence of target lesion restenosis (defined as a PSVr greater than or equal to 2.4 in the treatment zone). The duplex scan will to take 30 minutes and is part of the standard surveillance protocol at the host institution. It will be performed by an accredited medical sonographer at a specialist imaging provider (if performed as an out-patient) or by an accredited medical sonographer at Flinders Medical Centre if performed whilst the participant is an in-patient. Treatment and clinical assessments (both pre and post-procedure) will be performed at Flinders Medical Centre. Out-patient post-treatment duplex will be performed at Flinders Medical Centre or specialist imaging providers in the community. Data collected of clinical and imaging results will be used to obtain the primary and secondary outcome described in section 4. Agreement testing to assess the reliability of subjective assessment of dissection severity will be performed. This will be based on the angiographic imaging. The treating surgeon’s subjective assessment of dissection severity will be recorded and compared to the results of three independent blinded observers. The observers will be vascular surgeons employed by Flinders Medical Centre using de-identified images. This will be performed after the procedure and will not require the involvement of participants.