KEY WORDS Computed tomography angiography - free flap breast reconstruction - hand-held Doppler
- internal mammary perforators - recipient vessels
INTRODUCTION
The thoracodorsal vessels (TDVs) and the internal mammary vessels (IMVs) are the most
commonly used recipient vessels for free tissue transfer in breast reconstruction
surgery.[1 ]
[2 ]
[3 ]
[4 ] Alternative recipient vessels are used, by and large as a second choice.[1 ]
[5 ] Ever since Taylor and Palmer's description of cutaneous angiosomes and perforator
concept,[6 ] the armamentarium of clinically applicable perforators has expeditiously expanded.
One such perforator, the internal mammary artery perforator vessels (IMPVs) which
form the vascular basis of the popular deltopectoral flap as proposed by Bakamjian
et al .,[7 ] was described as a recipient vessel for free tissue transfer by Blondeel[8 ] and Guzzetti and Thione.[9 ]
The objectives of our study were to determine the anatomical consistency of the IMPV
and the suitability of IMPV for use as recipients in free flap breast reconstruction.
PATIENTS AND METHODS
Radio-anatomical study
Following initial success with the use of IMPV as recipients for free tissue breast
reconstruction, we carried out a computed tomography angiographic (CTA) study to assess
the anatomical consistency of these perforators. Data from ten randomly selected female
patients who did not have any chest wall or breast pathology but had undergone a CTA
for unrelated diagnostic reasons from April 2013 to October 2013 were analysed.
Helical computed tomography evaluation of internal mammary and perforator vessels
was performed from the thoracic inlet to the xiphoid process of sternum. CTA was performed
using a Discovery STE 64-slice scanner (GE Medical System, Chicago, Illinois, US).
Patients were examined in the supine position. Non-ionic contrast was injected at
a rate of 4 ml/s, with a contrast volume of 1.5–2 ml/kg body weight (350 mg of iodine/ml).
Images were acquired during breath hold in the arterial phase using bolus tracking
method. The region of interest was placed at the arch of the aorta with a threshold
value of 100 Hounsfield units. Imaging parameters included a beam pitch of 1:1.35,
tube potential of 120 kVp and tube current of 150–320 mA. Multiplanar reconstruction
was performed from the raw data with a minimum slice thickness of 1 mm and 50% overlapping.
Image reformation was performed using a volume-rendering technique on an Advantage
Window Workstation (version 4.5, GE Medical System, Chicago, Illinois, US). For each
patient, both sides were examined. A total of twenty sides were assessed. The evaluation
parameters included the intercostal space (ICS) through which the perforators emerged;
the distance of these perforators from the sternal border and the artery diameter.
When more than one perforator was present, the assessment was done on the dominant
(largest) perforator of each side.
Clinical study
Retrospective data from November 2012 to March 2014 of 15 patients who had undergone
mastectomy for breast cancer and had been primarily reconstructed with a deep inferior
epigastric artery perforator (DIEP) free flap transfer were considered. During this
period, all the 15 patients planned for reconstruction with DIEP free flaps were subjected
to a pre-operative perforator mapping using a hand-held Doppler (HHD) (model no. MD2;
8 MHz probe; Huntleigh Diagnostics, Cardiff, UK). Those that demonstrated a strong
perforator signal in the 2nd or 3rd ICS were selected for free tissue breast reconstruction using the IMAPV as recipients.
A total of seven non-consecutive patients were identified who had undergone DIEP free
flap transfer using the IMPV as recipient vessels. Retrospective data of these patients
were studied to determine the clinical suitability of the IMPV for use as recipients
in free tissue breast reconstruction.
RESULTS
The CTA findings showed that the internal mammary perforator artery was consistently
present in all cases on both sides [Figure 1 ]. In one patient (case 4), the perforator was attenuated, being reduced in calibre
and length. In all cases, the dominant perforator arose from the upper four intercostal
spaces (ICS), with the majority (55%) arising from the 2nd ICS followed by the 1st ICS (25%). The mean distance of the perforators from the sternal border at the level
of pectoralis muscle surface on the right side was 1.86 cm (range: 0.9–2.5 cm) with
a mode value of 1.9 cm. On the left side, a mean of 1.77 cm (range: 1.5–2.1 cm) and
a mode value of 1.7 cm were observed. Mean perforator artery diameters on the right
and left sides were 2.2 mm and 2.4 mm, respectively [Table 1 ]. The accompanying perforator veins were not visualised or assessed radiologically
during the CTA study.
Figure 1: Computed tomography angiographic images showing the internal mammary artery perforator
(white arrows) with parent internal mammary artery (black arrows). Note the long,
tortuous course of the perforators
Table 1
Computed tomographic angiography data of internal mammary artery perforators
n
Intercostal space
Distance from sternal border (cm)
Diameter (mm)
Left
Right
Left
Right
Left
Right
1
First
First
2.5
1.8
2.6
2.3
2
Second upper part
Second lower part
1.5
1.9
2.0
2.8
3
Third upper
Second lower
2.2
2.1
2.7
1.7
4
First attenuated
Second lower
0.9
1.5
1.7
2.8
5
Second
Second
1.6
1.7
2.7
2.7
6
Third upper
First
2.3
1.7
2.6
2.9
7
Third upper
Second upper
1.9
1.5
2.4
2.2
8
Second upper
First lower
1.9
2.1
2.6
2.3
9
Second upper
Fourth
1.9
1.7
3.1
2.2
10
Second lower
Second
1.9
1.8
1.9
2.6
Of the 15 patients undergoing DIEP flap breast reconstruction, the IMPVs were used
as recipients in seven (47%) patients. In all the seven patients who had undergone
free flap breast reconstruction with IMPV as recipient vessels, pre-operative HHD
demonstrated strong Doppler signals in the 2nd or 3rd ICS. This corroborated with the intraoperative findings [Figure 2 ] with the mapped perforators localised by the HHD in the 2nd and 3rd ICS being successfully identified and dissected out. In all cases where the IMPV
was used as a recipient, the perforators were dissected out superficial to the pectoralis
without intramuscular dissection. Where required, the mastectomy incisions were extended
to allow for comfortable access. Apart from a single instance (5% of the cases), the
perforator arteries were >1.5 mm in diameter, as measured by the vascular clamp markings.
The accompanying perforator veins, while being thin walled, were seen to have comparable
diameters as the arteries. Though there were issues with vessel size mismatch, vessel
size discrepancy of more than 50% was not encountered for either the arterial or venous
anastomosis and this could be adjusted for using standard microsurgical techniques.
In all cases, a single venous anastomosis was performed. There was no flap loss, partial
or complete, in these patients.
Figure 2: Photograph series of a case where the internal mammary artery perforator was used
as recipient. (a) Pre-operative photograph showing the deep inferior epigastric artery
perforator flap design and the skin-sparing mastectomy. Note the pre-operative Doppler
mapping of the internal mammary artery perforator (arrow). (b) Recipient site following
mastectomy showing the dissected perforators on the surface of the pectoralis major
(arrow). (c) Harvested deep inferior epigastric artery perforator flap. (d) Six-month
post-operative photograph showing a well-settled flap and good size and contour match
DISCUSSION
The thoracodorsal and internal mammary pedicle are a common choice as recipient vessels
for free flap breast reconstruction. The TDVs are frequently exposed during the axillary
clearance and, as such, is readily available to the reconstructive surgeon. However,
the use of TDVs as a recipient has a number of disadvantages, for instance, risk of
inadvertent damage during the axillary dissection and long pedicle requirement to
place the breast mound more centrally. The anastomosis in the axilla can be uncomfortable
for the surgeon and more so for the assistant standing across the operating table.
In addition, there is a tendency on the part of the reconstructive surgeon to place
the transferred tissue more laterally on the chest to protect the pedicle and avoid
any tension across the anastomosis.[3 ] With the advent of sentinel lymph node biopsy, the routine exposure of this pedicle
is also on the wane leading to a decline in the use of TDVs as a preferred recipient.[1 ]
Conversely, the use of the IMVs offers advantages, such as being nearly always available
in delayed and secondary breast reconstruction since it is not affected by adjuvant
radiotherapy and axillary dissection. In addition, the medial location of the pedicle
on the chest means greater freedom in flap shaping.[4 ] Lateral fullness, which is a common occurrence following breast reconstruction,
can be easily revised without risk to the anastomosis. Shorter flap pedicle lengths
are required to reach the recipient. There is usually no restriction to early shoulder
and arm mobilisation, thereby reducing, to a large extent, the morbidity seen when
the TDVs are used as recipient. Furthermore, axillary drains can be placed safely
without risk to the anastomosis. Finally, the use of the IMV, thereby sparing the
TDV, provides the reconstructive surgeon a lifeboat in the form of a pedicled latissimus
dorsi myocutaneous flap or a thoracodorsal artery perforator flap in the eventuality
that the free flap transfer is unsuccessful.[10 ] The IMV, however, is far from being an ideal recipient. The access to the IMVs can
be tedious, requiring removal of costal cartilage and transection of intercostal and
pectoralis muscles. Sacrifice of the internal mammary artery eliminates the vessel
as an option for future coronary bypass and may impair outcomes.[11 ] Respiratory chest wall motion can be troublesome, mandating, at times, a change
to manual ventilation or stoppage of respiration during suture placement.[3 ] Albeit the TDVs and the IMVs provide similar flap survival rates,[1 ] the IMV has been recommended as the recipient vessel of choice by many authors based
on its numerous benefits.[2 ]
[3 ]
The IMPV offers many advantages over its parent vessel. The exposure of these vessels
is simplified since there is no need to remove the costal cartilage or transect the
overlying intercostal and pectoralis muscles. This limited dissection needed for access
in turn leads to a reduction in overall operative time. The parent vessel, the internal
mammary artery, need not be sacrificed and is available as a coronary conduit should
it be required. The anastomosis is comfortable, being performed at the surface of
the pectoralis instead of in the depths of the intercostal space. In addition, the
respiratory chest wall movements which can be quite troublesome when using the IMV
are significantly dampened when using the IMPV as recipient, thereby contributing
to the performance of a favourable anastomosis.
This study was designed to address concerns regarding anatomical consistency of these
perforators in terms of their presence, location and anatomical variations with the
use of IMPV as recipient for free flap breast reconstruction. We found the IMPV to
be anatomically dependable, being bilaterally present in all patients examined. The
majority of the dominant perforators were seen to arise from the second ICS. This
is in agreement with other authors who also report a predilection of the dominant
perforator for the second ICS.[12 ]
[13 ]
An argument can be made for the need of performing a pre-operative CTA to assess the
clinical suitability of these perforators as recipients. Although some authors have
described the use of CTA for studying the internal mammary artery perforators,[14 ] we are unaware of any study that seeks to corroborate internal mammary artery perforator
diameters between CTA and intraoperative findings. In addition, few authors specify
exact intraoperative perforator diameters.[15 ] This is because intraoperatively perforator vessels may demonstrate vasospasm or
dilatation, being affected by unavoidable factors such as tissue handling and temperature
changes. Hence, diameters measured may not be representative or agree with imaging
data. However, an intraoperative perforator diameter of >1.5 mm has been used by many
authors as a criterion for selecting the IMPV as recipient vessels.[11 ]
[15 ]
[16 ] Other issues regarding the routine employment of CTA for pre-operative perforator
assessment include the increased cost and, more significantly, the risks associated
with radiation exposure.
In all the seven patients demonstrating strong Doppler signals in the 2nd and 3rd ICS, the IMPV could be dissected out successfully and were found to be suitable for
anastomosis. Those demonstrating dominant perforator signals in the 1st ICS were not considered since this space is usually not accessed during a standard
mastectomy, and performing an anastomosis here is difficult. No increase in complication
rates were seen with regard to partial or complete flap loss and fat necrosis when
the IMPV was used as recipient as compared to DIEP free flap breast reconstructions
using TDV and IMV as recipients. The IMPVs were used as recipient vessels in 47% of
our patients. Nevertheless, we acknowledge that the limited size of our clinical series
may not be representative or consistent with other studies that describe a wide variation
in the usability rates of these perforators as recipients.[17 ]
Marking the perforator(s) helps caution the resecting oncosurgeon to limit the use
of cautery dissection in the region of the perforators, thereby protecting them from
being accidentally injured during the mastectomy. In the uncommon instance that these
perforator vessels cannot be identified or are unsuitable for use, the reconstructive
surgeon has the option to proceed to dissect out the parent IMV for use as recipient.
Multiple authors have now reported their experience with the IMPV as recipient and
what is consistent across these reports is the safety and feasibility when using these
vessels.[15 ]
[16 ]
[18 ]
[19 ]
A concern that has not been adequately addressed in previous studies and that bears
vital importance from an oncological safety point of view is the adequacy of oncological
clearance when the IMPV are preserved. These perforators pass through the breast substance
on their way to supply the skin. Preservation of these perforators for their use as
recipients may be associated with incomplete excision of breast tissue, especially
perivascularly. Hence, breast cancers involving the upper, inner quadrant preclude
the use of these perforators as recipients in free tissue breast reconstructions.
While no mention has been made regarding increased rates of cancer recurrence when
the IMPVs have been used as recipients, long-term follow-up studies are desired to
put this issue to rest.
As a consequence of intraoperative transection during mastectomy or following destruction
during adjuvant radiotherapy, these perforators are generally not available as recipient
vessels in delayed breast reconstruction. Although both Munhoz et al .[18 ] and Follmar et al .[11 ] did not find suitable IMPV in the late reconstruction group, Halim and Alwi were
able to use the IMPVs as recipient in 8% of their patients.[17 ]
CONCLUSION
The aim of our study was not to compare the IMPVs with standard recipient vessels
such as the thoracodorsal pedicle or the IMV. Rather, we attempted to determine the
anatomical consistency and reliability of using the IMPVs as a recipient in free flap
breast reconstruction. Our study was limited by a small clinical sample size. Nonetheless,
based on our CTA findings, we determine that these perforators are anatomically dependable.
While CTA can indicate dominant perforator status, we recommend the use of HHD as
a cost-effective, safe, technically simple and widely available tool to map the IMPVs
preoperatively. Finally, though these perforators may be anatomically present in a
given patient, whether they will be used as recipients for free tissue breast reconstruction
will eventually depend on their location, preservation during mastectomy by the resecting
surgeon, successful dissection of these vessels, their diameters and the comfort level
of the operating surgeon. The IMPV does, however, offer a viable alternative in the
choice of recipient vessels for free flap breast reconstruction.
Financial support and sponsorship
Nil.
