Abstract 2619: Characterization of Cardiac Radiofrequency Ablation Lesions Using Contrast-Enhanced Multidetector Computed Tomography Imaging
Background - Catheter based treatment of scar mediated ventricular tachycardia (VT) requires energy delivery at the margins of the scar to eliminate electrically active viable cell islets. We recently demonstrated the ability to image myocardial infarction scar by multidetector computed tomography (MDCT). The ability to characterize myocardial radiofrequency ablation (RFA) lesions may allow for assessment of VT therapy and aid MDCT guided intervention. The purpose of this study was to characterize endocardial RFA lesions using MDCT.
Methods - RFA (60 °C) was performed in normal canine (n = 6). Contrast enhanced (190 ml) MDCT imaging (64 x 0.5 mm slices) was then performed every 5 minutes over 40 minutes to track the kinetics of contrast agent uptake. Following MDCT the animal was sacrificed and the heart excised for myocardial staining (TTC) to delineate tissue necrosis. MDCT lesion signal density was recorded in Hounsfield Units (HU) and lesion area was measured by hand planimetry over multiple slices.
Results - RFA lesions by MDCT appeared as regions with a core of hypointensity and an outer rim of hyperintensity (a). MDCT derived lesion area (normalized for myocardial area) compared well with those measured by postmortem exam (2.16%±1.09% vs. 2.24%±1.64%, respectively – p=NS). The average signal density of the lesion core and remote myocardium was 106.7±25.9 and 171.2±15.5 HU, respectively (p<05). Over time, signal density of the lesion core progressively increased (b).
Conclusions - MDCT accurately characterizes endocardial RFA lesions. This feature may be combined with electroanatomic mapping and MDCT myocardial scar imaging to aid delivery of therapy for scar induced VT.