3. RESULTS 
3.1 Patient characteristics and interventional outcome 
Seventy-two consecutive patients underwent MI catheter ablation either as part of a specific AF ablation strategy (n=35), or to treat clinical reentrant AT (n=32), or to treat AT occurred during ablation for AF (n=5). Patient baseline characteristics are shown in Table 1 . According to the predefined pacing maneuvers (Figure 1 ), the MI block was successfully achieved in 69 out of 72 (95.8%) patients (in 68 after the first procedure and in 1 patient after the second procedure). Of the four patients in whom complete MI block was unsuccessful during the first procedure, one had hypertrophic cardiomyopathy (MI block was achieved during the second ablation procedure), one suffered from cardiac amyloidosis (diagnosed later), while in the other two, the access to CS was not achieved due to a CRT-D left ventricular lead, and a particular anatomical configuration, respectively. Of the three patients whose MI block was not finally achieved, only one had PMF treated with an anterior linear lesion at the same procedure, and since then the patient remains in SR. The mean MI ablation time of was 10.73±6.16 min which was consisted of 10.12±5.87 min for endocardial ablation and 1±0.54 min for epicardial ablation through the CS.