Discussion:
Due to the different fixation way, cardiac perforation remains one of the severe complications of leadless pacemaker. It is recommended to implant it at the septum of the right ventricle to minimize the incidence of cardiac perforation 2,4 though it is not easy to achieve in all patients, especially in small hearts or cor pendulum (drop hearts) cases. According to the literatures2,3 [2,3], the risk factors for cardiac perforation in leadless pacemaker included female, low body mass index, history of myocardial infarction and lung diseases. Therefore, each patient should be carefully estimated before implantation, especially in cases with these risk factors. Our patient was an old female with low body mass index on dual anti-platelet therapy, which increased the peri-procedure bleeding risk, although the study by Kiani S5 et al showed continuation of therapeutic anticoagulation during MICRA implantation was feasible and safe. It is challenging to implant the leadless pacemaker in small-size heart cases since the shape of the delivery catheter is fixed. In our patient, it is not easy to perform Micra TPS across the tricuspid valve and accidently place it into coronary sinus after multiple attempts. Left anterior oblique view and angiography were useful to distinguish Micra TPS locating at coronary sinus or right ventricle. Other than cardiac injury by the fixation apparatus after deployment of Micra, cardiac perforation resulting from the delivery catheter against the ventricular wall has also been illustrated. Togashi I 6et al reported a case of subclinical cardiac perforation caused by the edge of the device cup penetrating into the ventricular wall prior to the deployment of the leadless pacemaker. Another 91-year-old female case reported by Hai JJ4 et al developed cardiac perforation due to contrast injection against the RV anterior wall before verification of sheath location. The cause of pericardial effusion in the present case was probably the coronary vein injury by the edge of the device cup, since pericardial effusion was detected by angiography when the catheter was placed into coronary sinus (Figure 1 ). The pericardial effusion aggravated and pericardial tamponade occurred probably due to dual anti-platelet therapy together with anti-coagulation of heparin. In terms of short half-life period, bivalirudin might be more suitable than heparin for peri-implantation anti-coagulation in patients on dual anti-platelet therapy to reduce the bleeding risk.