Case
62-year-old female with history of hypertension, type 2 diabetes, atrial
fibrillation and end stage renal disease (ESRD) was admitted to the
hospital with methicillin-resistant staphylococcus aureus (MRSA)
bacteremia. The source of her bacteremia was thought to be her
arteriovenous graft, which was later excised for source control. Her
hospital course was complicated with complete heart block with narrow
junctional escape rhythm. Further workup with a transesophageal
echocardiogram demonstrated a small mobile echo density measuring 4 x 5
millimeters (mm) attached to the coumadin ridge. Cardiac computed
tomography (CT) ruled out involvement of the aortic root i.e. aortic
root abscess or pseudoaneurysm. No other reversible causes of her
complete heart block could be identified. Subsequently a transvenous
pacing (TVP) wire was successfully placed within the right ventricle.
Given her diagnosis of infective endocarditis and need for a prolonged
course of antibiotics, decision was made to proceed with implantation of
a permanent pacing system. Patient was planned to undergo Micra
transcatheter leadless pacemaker implantation, due to her recent history
of extraction of her potentially infected left upper extremity AV graft,
and previously documented right subclavian vein occlusion. Subsequently,
the patient underwent Micra implantation through the right femoral vein.
After the device was deployed, the pull and hold test was performed to
ensure adequate fixation. The post fixation electrical testing of the
device demonstrated R wave sensing of 6.5 millivolts (mV), impedance 550
Ohms, and pacing threshold 1.3 V at 0.24 ms. The latter improved to
under 1 mV at 0.24 ms before the end of the case. Hence, decision was
made to cut the tethering suture and release the Micra device.
Post-procedurally, patient remained stable and was transferred to
medical floor.
Approximately 5 hours following Micra insertion, she developed
ventricular fibrillation cardiac arrest. The telemetry strip for the
event is shown in Figure 1. She received 7 shocks, 8 ampules of
epinephrine in addition to intravenous amiodarone and lidocaine boluses.
Return of spontaneous circulation (ROSC) was subsequently achieved and
she was transferred to the cardiovascular intensive care unit (CVICU).
In the CVICU, she was started on norepinephrine and vasopressin for
hemodynamic support. Her Micra interrogation showed normal device
function with stable impedance, sensing, and slightly higher pacing
threshold values. The latter, however remained below the programmed
pacing output of the device. Electrocardiogram (EKG) post cardiac arrest
showed ventricular-paced rhythm with occasional premature ventricular
complexes which is depicted in figure 2. Transthoracic echocardiography
did not show any evidence of pericardial effusion and her chest x-ray
showed stable device position from implantation. Her serum electrolytes
and blood counts were within normal limits and unchanged from admission.
Given the lack of a clear explanation of her VF arrest and given the
temporal association with the Micra device implantation, her VF was
presumed to be secondary to myocardial irritation from the Micra device.
Unfortunately, she developed worsening shock with increasing vasopressor
requirements and was later transitioned to comfort care following family
discussion and subsequently expired within 18 hours of original
procedure.