Patient Selection
The inclusion criteria for this study were the implantation of a Medtronic Micra LP with pre-procedural and post-procedural echocardiographic evaluation and a pacing percentage greater than twenty. Patients with a history of cardiac resynchronization therapy, those who did not meet pacing threshold, and lack of interval follow up data were excluded from the study. One patient was excluded due to lack of data for device implantation location, and one patient was excluded due to a myocardial infarction and subsequent sudden cardiac arrest within one week of his procedure which resulted in a decrease in LVEF that was deemed not to be secondary to PICM. This sudden cardiac arrest due to coronary thrombosis was determined not to be a procedural complication. A total of exactly 200 patients in the National Capital Region Military Health System received a Medtronic Micra LP from 2017 to 2021. Of these patients, 50 were being paced >20% of the time, which resulted in 48 patients being included in our analysis after the two exclusions discussed above. 43 of these 48 patients had an initial ejection fraction of ≥ 50% and were evaluated for PICM with both criteria while the remaining 5 patients were evaluated for PICM under the first criteria only.