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.