Full History:

21 year-old woman with severe post-partum cardiomyopathy.  A left ventricular assist device has been in place for 1 year and 9 months. She now has purulent discharge at the drive line skin site and leukocyte scintigraphy is requested to evaluate for infection. 

Discussion:

LVAD drive-line exit site infection is an expected consequence and a significant limiting factor in long-term support.  It is believed that drive-line trauma is the most common initiator of drive-line exit site infections.  Trauma is usually in the form of shearing traction or torsion injury caused by common events such as dropping the controller and battery pack, hooking the drive-line on a passing object.  These stress then cause disruption of the adherent interfacce between the skin and the subcutaneous tissues and the velour covering of the drive-line.  The disruption then never heals due additional microtrauma leading to neo-epithelialization and tract formation that is ideal for development of superimposed infection.  If the body seals the exit site with proteinaceous matarial, the infection can then extend further along the drive line towards the pump pocket.

Treatment immediately after trauma is immobilization of the drive-line to allow the disruption to heal.  If a tract is already formed, treament consists of antibiotics and aggressive surgical resection of the tract back to the point of adherence.  Antiobiotics alone has not proven effective.  If the tract is to close to the pump pocket, local surgical excision of the exit site and placement of a drain is performed.  If the pump pocket is involved, a drain is placed, the surgery is terminated, and further options are assessed. 

Role of Leukocyte scintigraphy:

Leukocyte scintigraphy is perfomed during the course of antibiotic treatment and "has proven highly accurate in preoperative prediction of tract anatomy, and therfore in the extent of exit site excision that will be required." 

"An isolated hot spot at the exit site alone suggest that a very limited exicision will suffice.  A hot spot at the exit site with a small trail of activity extending up the drive-line , unfortunately suggests that a more extensive exit site incision may be required to reach a circumferentially adherent area of the drive-line.  Worse yet, a trail of activity up to and involving the implanted device itself suggests that it may be too late for surgical intervention."