Procedure time for fEVAR in GG&C
Martin Hennessy
2023-07-25
1 Procedure times for fEVAR performed in GG&C
- This document contains data about 86 fEVAR/bEVAR performed in GG&C between 17 December 2009 and 16 June 2023.
- The two important concepts addressed are ‘device time’ and ‘theatre time’.
1.1 Device time and theatre time
- It is a standard procedure to perform an angiogram prior to opening an aortic stent-graft with the un-opened device in situ and a pigatil catheter from the contralateral side.
- It is also a standard procedure to perform an angiogram after all stent-grafts have been deployed.
- We define the time between these angiograms as ‘device time’ - this is the time required to deploy all devices, cannulate all vessels, balloon overlaps etc and is a reasonable standardised measured of the efficiency of the procedure.
- The times are taken from the PACS images and therefore rely on these being available.
- In GG&C, we have device time for 81 fEVAR/bEVAR (04 February 2015 - 16 June 2023.)
- Theatre time is a measure of how long the patient spends in the operating theatre.
- It is calculcated using the anaesthetists monitoring chart and is taken as the time between the first and last set of documented observations.
- It may therefore underestimate the time the patient spends in theatre in some cases.
- In GG&C, we have theatre time for 78 fEVAR/bEVAR (10 March 2015 - 16 June 2023.)
1.2 Important considerations and change in practice over time
- It is important to note that in 2020, GG&C moved from using Vascutek Anaconda to Cook Zenith custom-made devices.
- In addition, procedure number increased since this change.
- These changes will be largely hidden in the figures and tables below and so the following table is included for reference:
| Year | |||||||||
|---|---|---|---|---|---|---|---|---|---|
| 2015 | 2016 | 2017 | 2018 | 2019 | 2020 | 2021 | 2022 | 2023 | |
| Device | |||||||||
| Anaconda | 2 | 3 | 7 | 6 | 5 | 2 | 0 | 0 | 0 |
| Zenith | 0 | 0 | 0 | 0 | 0 | 5 | 19 | 22 | 10 |
- An overall look at device time and theatre time will help decide how to report summary statistics.
- Below is a histogram of both:
- Device time looks clearly abnormally distributed and theatre time probably is too (both can be confirmed by Shapiro Wilk test).
- As such we will report medians and interquartile range, rather than means and standard deviation.
2 Device time
2.1 Number of fenestrations
- The number of fenestrations (or branches) to be cannulated may impact on device time.
- This is shown in the boxplot below:
2.2 Type of custom-made graft
- Endografts with branches exclusively or in addition to fenestrations may impact on device time.
- This is shown in the boxplot below:
2.3 Aneurysm classification
- The extent of the aneurysm being treated, whether thoraco-abdominal or juxta-renal, may impact on device time.
- This is shown in the boxplot below:
2.4 Stent-graft used
- Different stent-grafts may impact on device time.
- In addition it should be remembered that initial experience was gained using the Anaconda platform before moving to Zenith and markedly increaseing case numbers (see table above).
- This is shown in the boxplot below:
2.5 Year of procedure
- With increasing experience, device time may also decrease.
- The is shown in the boxplot below.
- In addition, due to the switch from Anaconda to Zenith in 2020, these categories are also displayed.
2.6 Anaesthetic used
- As confidence with the procedure has grown, we have increasingly used local anaesthetic where appropriate for these cases.
- Effect on device time is shown in the boxplot below:
2.7 Tabulated display of device time
- For those who prefer a numerical representation of the date to a visual one:
| Device time (minutes): Median (IQR) | |
|---|---|
| Fenestrations/branches | |
| 2 | 93 (63, 113) |
| 3 | 123 (87, 162) |
| 4 | 119 (77, 143) |
| 5 | 126 (126, 126) |
| 6 | 205 (205, 205) |
| Type of CMD | |
| Branches +/- fenestrations | 127 (113, 142) |
| Fenestrations only | 110 (73, 158) |
| Aneurysm type | |
| I | 124 (122, 126) |
| III | 107 (78, 144) |
| IV | 159 (136, 182) |
| JRA | 110 (73, 148) |
| V | 134 (130, 138) |
| Device | |
| Anaconda | 142 (122, 190) |
| Zenith | 91 (68, 127) |
| Year | |
| 2015 | 173 (141, 204) |
| 2016 | 174 (149, 202) |
| 2017 | 130 (112, 151) |
| 2018 | 219 (142, 254) |
| 2019 | 142 (129, 145) |
| 2020 | 160 (117, 215) |
| 2021 | 113 (79, 131) |
| 2022 | 77 (62, 96) |
| 2023 | 71 (63, 111) |
| Anaesthesia | |
| General anaesthetic | 126 (95, 163) |
| Local anaesthetic | 63 (52, 74) |
| Spinal anaesthetic | 118 (98, 138) |
3 Theatre time
- As device time is a subset of theatre time, we have chosen fewer visualisations of theatre time.
- The year of the procedure reflects institutional experience with the procedure which may decrease the theatre time.
- As above, we have incorporated the stent-graft used into the ‘year’ plot.
- The anaesthetic method is the main factor we believe will affect theatre time and so it is also presented.
3.1 Year of procedure
3.2 Anaesthetic used
3.3 Tabulated display of theatre time
- For those who prefer a numerical representation of the date to a visual one:
| Theatre time (minutes): Median (IQR) | |
|---|---|
| Year | |
| 2015 | 240 (240, 240) |
| 2016 | 270 (265, 295) |
| 2017 | 205 (190, 223) |
| 2018 | 290 (236, 329) |
| 2019 | 215 (205, 230) |
| 2020 | 228 (186, 265) |
| 2021 | 220 (151, 234) |
| 2022 | 148 (108, 184) |
| 2023 | 118 (91, 175) |
| Anaesthesia | |
| General anaesthetic | 215 (165, 250) |
| Local anaesthetic | 105 (88, 120) |
| Spinal anaesthetic | 190 (170, 210) |