Enlargement of catheter ablation lesions in infant hearts with cryothermal versus radiofrequency energy: an animal study.
BACKGROUND
Radiofrequency catheter ablation in immature hearts has been associated with marked enlargement of lesions over time, with potential for related late adverse events. It remains unknown whether cryothermal ablation lesions display a similar pattern of growth.


RESULTS
Ablation lesions (n=384) were performed in 32 infant miniature swine in right and left atria, ventricles, and atrioventricular (AV) grooves preselected by a randomized factorial design devised to compare radiofrequency and cryothermal lesions produced by 7F 4-mm electrode-tip catheters. Animals were euthanized acutely or at 1, 6, or 12 months, according to the randomization scheme. The miniature swine weighed 8.8±1.2 kg and were 63±13 days of age at time of ablation. The minimum temperature during cryoablation was -79.8±3.4°C and the average temperature during radiofrequency ablation was 54.4±5.5°C. On morphometric analyses, no differences in the rate of growth of ablation lesions were noted between the 2 energy modalities in atria (P=0.44), ventricles (P=0.57), or AV grooves (P=0.69). Lesion volumes increased 3.3-fold in atria (95% confidence interval [CI], 2.3 to 4.3; P=0.001) and 2.2-fold in ventricles (95% CI, 1.4 to 3.0; P<0.0001), with the difference between chambers being nonsignificant (P=0.22). Whereas the depth of AV groove lesions increased over time (1.9-fold; 95% CI, 1.5 to 2.3; P<0.0001), lesion volumes did not enlarge significantly (1.5-fold; 95% CI, 0.4 to 2.6; P=0.45).


CONCLUSIONS
Ablation lesions produced by cryothermal energy in immature atrial and ventricular myocardium enlarge to a similar extent to radiofrequency ablation. In contrast, AV groove lesion volumes do not increase significantly with either energy modality.
Electrophysiology Service and Research Center, Montreal Heart Institute, Université de Montréal, Canada. paul.khairy@umontreal.ca
Paul
P
Khairy
Peter G
PG
Guerra
Lena
L
Rivard
Jean-François
JF
Tanguay
Evelyn
E
Landry
Marie-Claude
MC
Guertin
Laurent
L
Macle
Bernard
B
Thibault
Jean-Claude
JC
Tardif
Mario
M
Talajic
Denis
D
Roy
Marc
M
Dubuc
D000818:Animals; D000831:Animals, Newborn; D006348:Cardiac Surgical Procedures / Q000009:adverse effects; D017115:Catheter Ablation / Q000009:adverse effects / Q000379:methods*; D003452:Cryosurgery / Q000009:adverse effects; D006325:Heart Atria / Q000254:growth & development / Q000473:pathology / Q000601:surgery*; D006352:Heart Ventricles / Q000254:growth & development / Q000473:pathology / Q000601:surgery*; D009206:Myocardium / Q000473:pathology*; D018579:Patient Selection; D011897:Random Allocation; D018570:Risk Assessment; D013552:Swine; D013556:Swine, Miniature; D013997:Time Factors