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The Arterial and Venous Anatomies of the Deep Inferior Epigastric by vcWVXrTS

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									The Arterial and Venous Anatomies of the Deep Inferior Epigastric Perforator Flap



Department of Plastic Surgery, University of Texas Southwestern Medical Center, UT
Southwestern Medical Center, 1801 Inwood Road, Dallas, TX 75390-9132




Introduction

The use of the deep inferior epigastric artery perforator (DIEP) flap is becoming

increasingly popular in autologous breast reconstruction. The flap was first described as a

pedicled flap by Koshima and Soeda in 1989 [1]. Amongst its advantages are a large

adipocutaneous vascular territory reliably perfused on a single perforator, and reduced

donor site morbidity compared with the transverse rectus abdominis musculocutaneous

(TRAM) flap [2,3]. The flap has also been described as a thinned paraumbilical flap

[4,5].

Although anatomical studies have noted that the lateral row perforators are generally

easier to dissect than medial row perforators [6], Blondeel noted in a series of 100 free

DIEP flaps that all flaps with compromised vascularisation of zone IV in the study were

nourished by lateral perforators, and therefore advised that the use of medial perforators

is imperative if zone IV is required [7]. Gill et al. have suggested that where multiple

perforators are required to perfuse the flap, there is no strong centralized blood supply

and flap survival is dependent on small-diameter vessels. Interestingly, as the number of

perforators increased, so did the incidence of complications [8].

Another theory for the unreliabilty of zone IV relates to its venous anatomy. Blondeel

noted that the incidence of diffuse venous insufficiency that threatened flap survival and




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required a microvascular anastomosis to drain the superficial inferior epigastric vein

occurred in approximately 2% of flaps in a large clinical series compared with a zero

incidence in a comparative TRAM flap group. In each of these cases, the presence of a

superficial inferior epigastric vein that was larger than usual was noted. Anatomical

studies with Microfil injections of the superficial venous system of the DIEP or TRAM

flap performed in 15 cadaver and 3 abdominoplasty specimens found that large lateral

branches crossing the midline were found in only 18 percent of cases, whereas 45 percent

had indirect connections through a deeper network of smaller veins and 36 percent had no

midline crossing branches [9]. Carramenha e Costa et al. have noted that the superficial

inferior epigastric vein is the largest vein that drains the skin paddle of the transverse

lower abdominal adipocutaneous paddle [10], suggesting that venous drainage

predominatly occurs through this vessel in the normal physiological state. Flap harvest

with ligation of the superficial vein at the cephalic and caudal aspects of the flap redirects

the venous drainage through the smaller venae comitantes of the deep inferior epigastric

artery (DIEA) perforators.

This study determines the anatomy and perfusion of the arterial and venous systems of

the DIEP flap using novel three- and four-dimensional computed tomographic

angiography and venography techniques. This may help optimize flap design where

inclusion of zone IV is desired.




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Materials and Methods



Flap harvest and preparation

Ten flaps were harvested from fresh adult cadavers acquired through the Willed Body

Program at The University of Texas Southwestern Medical Center, and two

abdominoplasty specimens were obtained following patient consent.

In the cadaveric specimens dilute methylene blue dye solution was injected into the

DIEA to highlight all of the perforators and dissection was performed under loupe

magnification. All flap perforators and their accompanying venae commitantes were

identified and preserved, and medial and lateral row perforators from each side of the flap

were cannulated using a 24-gauge butterfly catheter (0.7mm diameter; BD Insyte; Becton

Dickinson S.A., Madrid, Spain). All vascular leaks observed were coagulated using

bipolar diathermy, followed by irrigation with warmed saline (37°C) containing heparin

(10 U/ml) until the effluent was colourless. For study of the venous system, the largest

vena commitans accompanying arterial perforator was cannulated and prepared as above,

as were the superficial epigastric vein, cannulated at either the cephalic or caudal aspect

of the flap.



Dynamic CT imaging

Iodinated contrast medium (Omnipaque; iohexol; 300 mg/ml; Amersham, Princeton, NJ)

was heated to 37°C to reduce the viscosity and improve vascular filling, and placed in a

syringe loaded into a Harvard precision infusion pump (PHD 2000, Harvard Apparatus,

Inc.). Adequate filling of the vascular territory was achieved with 3ml of contrast at an




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optimal rate of injection of 0.25ml/min to gain a detailed appreciation of the development

of the microvascularity over time. Increasing the volume of contrast did not increase the

size of the vascular territory. A volume of 5ml of Omnipaque was required to provide

adequate filling of the venous system.

Helical scans were performed using a GE Lightspeed 16 slice scanner (General Electric,

Milwaukee, WI) set to perform 0.625 mm slices using the highest rotation speed

available. Scans were repeated at a 0.05 ml fill increment over the first 0.5 ml of the

contrast injection to reveal the pattern of early filling, and at 0.25 ml fill increments

thereafter.

The flaps were then irrigated with warmed saline to remove the contrast medium, and the

next perforator was injected using the same protocol.

The abdominoplasty specimens had a lateral row perforator cannulated and were injected

with an aqueous eosin solution within two hours of flap harvest. The territory was

marked and the flap was then refrigerated at 4°C for 72 hours, and the same perforator

was injected with an aqueous methylene blue solution to determine the difference in

vascular territory.

Vascular territories of the medial and lateral row perforators were confirmed using

aqueous eosin and methylene blue injections.



Static CT imaging

To obtain a static image, barium sulphate/ gelatin mixture for vascular injection was used

as described previously [11]. Following vascular injection, each flap was stored at -20C




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a freezer. A slow helical scan protocol was used to produce high quality static images

with the flap positioned parallel with the coil of the scanner to minimise scan time.



Results



Arterial system

The arterial system of the DIEP flap is arranged into distinct lateral and medial rows of

perforators. Perfusion of the flap through these perforator complexes occurred in a

pattern dependent on the perforator location within the flap. Perforators from the lateral

row were found to first perfuse the subdermal plexus, followed by recurrent fill of the

medial row perforators. The medial row perforator communicated with the contralateral

medial row perforator complexes via large diameter linking vessels across the midline.

These vessels were noted to occur at the level of the subdermal plexus as they passed

across the linea alba. Filling of the lateral row perforators was not seen to vascularise the

contralateral flap territory in any of the specimens. By contrast zone III of the flap could

be captured via injection of a medial row perforator.

Injection of inks into a lateral row perforator of the abdominoplasty specimens shortly

after harvest and then after 72 hours revealed that staining across the midline was noted

in the recently harvested flap, with approximately a 25% greater vascular territory

compared with the flap after 72 hours. This implies that the injection studies in the

cadaveric specimen are an underestimate of the vascular territory.




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Venous system

The superficial and deep venous drainage systems consist of the superficial and deep

inferior epigastric veins, connected by the venae comitantes of the perforators of the

DIEA. Injection of either the venae comitantes or the superficial epigastric veins revealed

the same venous filling pattern. Filling of the adjacent superficial epigastric vein across

the midline occurred through vessels crossing the midline at the level of the subdermal

plexus. A variety of venous morphological patterns were seen, and in one flap the

superficial epigastric veins originated from a common origin in the midline of the caudal

aspect of the flap. In one flap no venous crossover was seen, which may explain diffuse

venous congestion seen clinically.




Discussion

This study demonstrates that the medial row perforators are anatomically different to the

lateral row perforators and should be selected if perfusion of zone IV is required.

Absence of venous drainage across the midline was seen in one flap, and suggests that

this may be the cause of diffuse venous congestion of zone IV.




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References



   1. Koshima I, Soeda S. Inferior epigastric artery skin flaps without rectus abdominis

      muscle. Br J Plast Surg. 1989 Nov;42(6):645-8.



   2. Blondeel N, Vanderstraeten GG, Monstrey SJ, Van Landuyt K, Tonnard P,

      Lysens R, Boeckx WD, Matton G. The donor site morbidity of free DIEP flaps

      and free TRAM flaps for breast reconstruction. Br J Plast Surg. 1997

      Jul;50(5):322-30.



   3. Futter CM, Webster MH, Hagen S, Mitchell SL. A retrospective comparison of

      abdominal muscle strength following breast reconstruction with a free TRAM or

      DIEP flap. Br J Plast Surg. 2000 Oct;53(7):578-83.



   4. Koshima I, Moriguchi T, Fukuda H, Yoshikawa Y, Soeda S. Free, thinned,

      paraumbilical perforator-based flaps. J Reconstr Microsurg. 1991 Oct;7(4):313-6.



   5. Koshima I, Moriguchi T, Soeda S, Tanaka H, Umeda N. Free thin paraumbilical

      perforator-based flaps. Ann Plast Surg. 1992 Jul;29(1):12-7.



   6. Munhoz AM, Ishida LH, Sturtz GP, Cunha MS, Montag E, Saito FL, Gemperli R,

      Ferreira MC. Importance of lateral row perforator vessels in deep inferior




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   epigastric perforator flap harvesting. Plast Reconstr Surg. 2004 Feb;113(2):517-

   24.



7. Blondeel PN. One hundred free DIEP flap breast reconstructions: a personal

   experience.

   Br J Plast Surg. 1999 Mar;52(2):104-11.



8. Gill PS, Hunt JP, Guerra AB, Dellacroce FJ, Sullivan SK, Boraski J, Metzinger

   SE, Dupin CL, Allen RJ. A 10-year retrospective review of 758 DIEP flaps for

   breast reconstruction. Plast Reconstr Surg. 2004 Apr 1;113(4):1153-60.



9. Blondeel PN, Arnstein M, Verstraete K, Depuydt K, Van Landuyt KH, Monstrey

   SJ, Kroll SS. Venous congestion and blood flow in free transverse rectus

   abdominis myocutaneous and deep inferior epigastric perforator flaps. Plast

   Reconstr Surg. 2000 Nov;106(6):1295-9.



10. Carramenha e Costa, M. A., Carriquiry, C., Vasconez, L. O., Grotting, J. C.,

   Herrera, R. H., and Windle, B. H. An anatomic study of the venous drainage of

   the transverse rectus abdominis musculocutaneous flap. Plast. Reconstr. Surg. 79:

   208, 1987.




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11. Tan, B. K., Ng, R. T. H., Tay, N. S., et al. Tissue microangiography using a

   simplified barium sulphate cadaver injection technique. Ann. Acad. Med.

   Singapore 28: 152, 1999.




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Figures 1 and 2. Dynamic CT angiography of lateral (above) and medial (below) row

perforators of the same flap (following injection of 3ml of contrast), revealing capture of

zone III with the medial row perforator. Anteroposterior views.




Figures 3 and 4. Early dynamic CT angiography of a medial row perforator revealing

large diameter linking vessels crossing over the midline at the level of the subdermal

plexus to perfuse zone III via recurrent flow. Anteroposterior and lateral views.




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