Characterization of radiofrequency ablation lesions with gadolinium-enhanced cardiovascular magnetic resonance imaging.
OBJECTIVE
This study was designed to evaluate the characteristics of gadolinium-enhanced imaging of radiofrequency ablations.


BACKGROUND
Gadolinium-enhanced magnetic resonance imaging (MRI) has been used successfully to evaluate tissue necrosis after myocardial infarction. In electrophysiology, radiofrequency energy is used to create a targeted myocardial necrosis for the treatment of various arrhythmias.


METHODS
Using a power-controlled, cooled-tip 7-F catheter system, radiofrequency lesions (10 to 40 W for 30 s) were created on the epicardium of the right ventricle in eight mongrel dogs. After injection of 0.225 mmol/kg gadolinium, T1-weighted fast gradient echo images were obtained during a follow-up of 10 h using an intrathoracic high-resolution coil. Radiofrequency ablations were analyzed on the MR images and compared with gross anatomy and histopathology.


RESULTS
Four distinct phases of signal enhancement were observed. After gadolinium injection, radiofrequency lesions were delineated clearly as contrast-free areas of low signal intensity (contrast-to-noise ratio [CNR] = -21.1 +/- 19.8). Signal enhancement in the lesion periphery started 4.0 +/- 1.8 min after injection and progressively extended toward the lesion center at a rate of 0.02 mm/min. Full delayed enhancement was observed after 98 +/- 21 min (CNR = +17.8 +/- 9.0). During the follow-up period, CNR started to decrease, but the lesions were detectable for as long as 10 h of follow-up. During the first three phases of enhancement, MRI correlated well with the pathological findings (r = 0.88, r = 0.88, and r = 0.86 [p < 0.001], respectively).


CONCLUSIONS
Radiofrequency ablation can be evaluated accurately by using gadolinium-enhanced MRI, which may allow the noninvasive assessment of procedural success. The dissimilar wash-in and wash-out kinetics compared with myocardial infarction suggest a different pathophysiological process with complete loss of microvasculature.
Dickfeld
Timm
T
Division of Cardiology, Department of Radiology, Johns Hopkins School of Medicine, Baltimore, Maryland, USA. tdickfel@medicine.umaryland.edu
Kato
Ritsushi
R
Zviman
Menekhem
M
Lai
Shenghan
S
Meininger
Glenn
G
Lardo
Albert C
AC
Roguin
Ariel
A
Blumke
David
D
Berger
Ronald
R
Calkins
Hugh
H
Halperin
Henry
H
D000818:Animals; D017115:Catheter Ablation; D004285:Dogs; D022062:Electrophysiologic Techniques, Cardiac; D005682:Gadolinium; D007089:Image Enhancement; D008279:Magnetic Resonance Imaging / Q000379:methods*; D009206:Myocardium / Q000473:pathology*; D009336:Necrosis; D010496:Pericardium
D005682:Gadolinium