Archived case 219 · March 27-April 3, 2017
71-year old man with significant cardiac history, long-standing LVAD, new holosystolic parasternal cardiac murmur and recent change in mental status.
Describe the pertinent imaging findings and the significance of such. What findings if any may explain the cardiac murmur and altered mental status.
Selected contrast-enhanced CT images (mediastinal windows) at the level of the outflow conduit anastomosis (Fig. 1 A) and through the ventricles (Fig. 1B) reveal partial thrombosis of the outflow conduit (Fig. 1A) and abnormal soft-tissue stranding about the conduit at the level of the right ventricle. Also notice the discrepant disparate enlargement of the right ventricle relative to the left ventricle. Volume rendered 3D reconstruction of the myocardium and the LVAD (Fig. 2) confirm the partial thrombosis of the outflow conduit, murmur and altered mental status result from flow-limiting stenosis and kinking of the conduit proximal to the anastomosis with the native ascending thoracic aorta. Subsequent head CT (not illustrated) revealed sequela of an embolic cerebral vascular accident (write-up and images provided by Lynn Ivey, MD, VCU Diagnostic Radiology). Answer Diagnosis: Kinking of LVAD Outflow Conduit with Partial Thrombosis and Concomitant Infection
Kinking of LVAD Outflow Conduit with Partial Thrombosis and Concomitant Infection
Differential Diagnosis
None
Discussion
Left ventricular assist devices (LVAD) are surgically implanted devices which completely replaces pumping blood in patients with severe refractory cardiac failure. It may be used as a bridge to cardiac transplantation, or as destination therapy in patients who are not transplant candidates. A commonly used LVAD is the HeartMate II®, a continuous flow device. Flow is generated by using an axial flow rotary pump made of titanium. The inflow cannula is implanted into the apex of the left ventricle and connects to the pump via bend relief. The outflow cannula is inserted into either the ascending or descending thoracic aorta, usually the former. The pump-rotor is housed within a small abdominal pre-peritoneal pocket. A percutaneous power cord-driveline connects the LVAD to its external power source and system controller. Continuous flow devices may be associated with increased potential of thrombosis due to high velocities of blood flow passing through their narrow orifices, generating shearing forces that result in hemolysis and platelet activation. The blood-contacting surfaces of the LVADs are biologically active, capable of producing a local pro-inflammatory-procoagulant environment, which activates both procoagulant and fibrinolytic mechanisms. A shift in the balance between these two cascades can lead to potential thromboembolic events. Most LVAD patients therefore require long term anticoagulation.
Infection is also not an infrequent complication. Infection may be intravascular or localized. Imaging can be helpful in demonstrating localized infections by identifying fluid collections and/or locules of gas along the power cord tract or internal hardware. The majority of LVAD infections are caused by biofilm-forming bacteria and fungi. Infections from the power cord can seed and infect other parts of the LVAD.
Management
Treatment for thrombus includes either medical therapy or LVAD device exchange. The risks and benefits of both treatment options must be weighed carefully for each individual patient depending on comorbidities as well as acuity of the thrombus. Antibiotic treatment tends to suppress the infection without eradicating it. Most infections can be effectively suppressed until transplantation has been performed; however, these infections may still cause serious morbidity and mortality.
Suggested Readings
Carr, Carrie M., MD, Jaisy Jacob, BA, Soon J. Park, MD, Barry L. Karen, MD, Eric E. Williamson, MD, and Philip A. Araor, MD. "CT of Left Ventricular Assist Devices. RadioGraphics. RadioGraphics, 1 Oct. 2009. Web. 18 Jan. 2017.
Parker, Mark S., Rosado De Christenson Melissa L., and Gerald F. Abbott. Cardiac Devices. In: Chest Imaging Case Atlas. 2012; New York: Thieme; pp.732-738Original case written by its authors at Virginia Commonwealth University and published at this address as part of a weekly teaching collection. Reproduced here as an archive.