Voltage and activation mapping - How the recording technique affects the outcome of catheter ablation procedures in patients with congenital heart disease

Background - Endocardial mapping is mandatory before radiofrequency catheter ablation (RFCA). Mapping can be performed with either unipolar or bipolar recordings. Impact of the recording technique used was studied in patients with and without structural heart disease using the 3D electroanatomic CARTO mapping system. Methods and Results - Patients (n = 44; 16 males; age 43 +/- 16 years) referred for RFCA of atrial flutter (AFL, n = 18), focal atrial tachycardia (FAT, n = 4), AV nodal reentrant tachycardia (AVNRT, n = 5), or scar-related atrial reentrant tachycardia (IART, n = 17) were studied. Voltage and activation maps were constructed. Unipolar and bipolar voltage distribution in the different groups was studied to establish a cutoff voltage value to facilitate delineation of scar tissue. Electrograms were recorded during tachycardia (FAT: n = 246, cycle length [ CL] = 449 +/- 35 ms; AVNRT: n = 182, CL = 359 +/- 47 ms; AFL: n = 1164, CL = 255 +/- 56 ms; IART: n = 2431, CL = 280 +/- 74 ms). Unipolar voltages were greater than bipolar voltages (P < 0.001). Unipolar voltages ≤1.0 mV were equally distributed in both AFL and IART patients. Bipolar voltages ≤0.1 mV were only found in patients with IART, and subsequently 0.1 mV was used as the cutoff value to delineate scar tissue. No unipolar cutoff value could be established. Timing of unipolar and bipolar local activation was correlated in all patient groups. Conclusions - The recording technique used has considerable impact on reconstruction of reentrant pathways and on the outcome of RFCA. In general, unipolar and bipolar recordings provide complementary information; however, only bipolar recordings allow voltage-based scar tissue delineation in patients with congenital heart disease.