Scar-related atrial tachycardias (ATs) are very challenging. Thus far, no comparative studies have been conducted between the up-to-date systems, namely the new confidense HD colouring mapping module (Carto 3 v. 4, Biosense Webster) (HD) and the new rhythmia (Boston Scientific) (RM) mapping system.

Our study sought to compare both strategies in terms of:

– diagnosis and immediate treatment success;

– procedure parameters in AT presenting patients.

Overall, 38 patients (68±9 years old) with complete mapping and ablation were randomised (HD=20, RM=18). The HD and RM groups displayed similar characteristics and etiologies. The AT mechanisms did not differ between the groups: macro/small loop re-entrant mechanisms were more common in both groups (12/20 [60%] versus 10/18 [56%], P=0.9), with the remaining diagnosed as multi-loop (5/20 [25%] versus 4/18 [22%]; P=0.9); focal (1/20 [5%] versus 2/18 [11%], P=0.9), and localised re-entrant (2/20 [10%] versus 2/18 [11%]). The procedure parameters were as follows: tachycardia cycle length (275±30 vs. 280±50; P=0.7); number of activation maps per patient (2±1 vs. 2±1; P=0.9); procedure time (138±90 vs. 139±90min; P=0.98); X-ray time exposure (20±11 vs. 24±18min; P=0.42); RF application time (39±36 vs. 25±28min; P=0.21); and mean number of circuits per patient (1.8±1 vs. 1.6±0.9; 0.6). Acute success was obtained in 15/20 pts (75%) of the HD group and 14/18 (78%) of the RM group (P=0.9). Two patients who failed to achieve the primary endpoint with the HD colouring were secondly converted to the RM group without success. No crossover was carried out in the RM group.

The preliminary results of this prospective monocentre randomised study demonstrate that HD colouring and rhythmia systems exhibit a similar efficacy in achieving acute AT termination.