3 | DISCUSSION
To our knowledge this is the first report of CPAF detection in an ESUS patient with situs inversus totalis. The detection rate of CPAF in ESUS patients using ICM is 30%.3 However, because the incidence of SIT is very low in the general population4 and because the heart and the conduction system are located on the right side of the body, the safety and efficacy of ICM in these patients remains unclear. In our experience, ICM insertion into the right margin of the sternum along the heart shadow using fluoroscopy is safe and effective for detecting CPAF.
There are three types of ICM devices used in Japan. In the present case we used the BIOMONITOR III, a novel ICM device that combines a long sensing vector with a miniaturized profile. Previous studies have described visible P-waves in >80% of cases.2 In our case there was no P-wave in the subcutaneous ECG during AF compared with that during sinus rhythm (Figure 2A, B). In the subcutaneous ECG recorded by the sudden drop rate alarm, the P-wave was not visible during AF, but appeared when the system returned to sinus rhythm. These findings provided a clear diagnosis of AF rather than sinus tachycardia, and the patient’s medicine was changed from aspirin to edoxaban. There are several case reports on the feasibility and safety of catheter ablation for AF with SIT.5 Thus, if our patient shows drug-refractory AF, we will consider catheter ablation.