Characterization of edema after cryo and radiofrequency ablations based on serial magnetic resonance imaging

Abstract

Introduction: Radiofrequency (RF) and cryoablation are routinely used to treat arrhythmias, but the extent and time course of edema associated with the two different modalities is unknown. Our goal was to follow the lesion maturation and edema formation after RF and cryoablation using serial magnetic resonance imaging (MRI).Methods and Results: Ventricular ablation was performed in a canine model (n = 11) using a cryo or an irrigated RF catheter. T2-weighted (T2w) edema imaging and late gadolinium enhancement (LGE)-MRI were done immediately (0 day: acute), 1 to 2 weeks (subacute), and 8 to 12 weeks (chronic) after ablation. After the final MRI, excised hearts underwent pathological evaluation. As a result, 45 ventricular lesions (cryo group: 20; RF group: 25) were evaluated. Acute LGE volume was not significantly different but acute edema volume in cryo group was significantly smaller (1225.0 ± 263.5 vs 1855.2 ± 520.5 mm 3 ; P = 0.01). One week after ablation, edema still existed in both group but was similar in size. Two weeks after ablation there was no edema in either of the groups. In the chronic phase, the lesion volume for cryo and RF in LGE-MRI (296.7 ± 156.4 vs 281.6 ± 140.8 mm 3 ; P = 0.73); and pathology (243.3 ± 125.9 vs 214.5 ± 148.6 mm 3 ; P = 0.49), as well as depth, was comparable.Conclusions: When comparing cryo and RF lesions of similar chronic size, acute edema is larger for RF lesions. Edema resolves in both cryo and RF lesions in 1 to 2 weeks. K E Y W O R D S catheter ablation, cryoablation, late gadolinium enhancement, magnetic resonance imaging, radiofrequency 1 | INTRODUCTION Cryo and radiofrequency (RF) ablations are routinely used to treat cardiac arrhythmias. 1 Ablation success depends on creating durable lesions. Despite best efforts, arrhythmia recurrence following catheter ablation is commonly observed. 2,3 Prior studies have shown that there can be a significant edema formation during ablation 4 and some of the recurrences has been attributed to the creation of this edema and as a J Cardiovasc Electrophysiol. 2019;30:255-262. wileyonlinelibrary.com/journal/jce © 2018 Wiley Periodicals, Inc. | 255 O R I G I N A L A R T I C L Eresult, reversible block. 5 Deeper and bigger lesions can be made by using higher contact force, but higher contact force is also associated with more complications like steam pops as well as edema. 6,7 We have also recently reported the large extent of edema that is associated with RF ablation and that it resolves over the span of few weeks. 8 However, the differences between the creation and timeline of edema associated with cryo vs RF are still unknown.Late gadolinium enhancement magnetic resonance imaging (LGE-MRI) has been used to estimate myocardial scar after catheter ablation and T2-weighted (T2w) MRI has been used to estimate edema. [9][10][11] Our goal in this study was to study the timeline and differences between edema and lesion maturation between cryo and RF ablation by using serial MRI for acute and chronic ablation lesions of similar size.

The Effective Contact Force to Minimize Edema Relative to Chronic Lesion Formation During Radiofrequency Ablation in Ventricular Wall

“…The use of MRI for evaluating myocardial substrate as well as lesion quality assessment is becoming more routine. [6][7][8][9]11,[16][17][18] In this study, we confirmed that that acute LGE-MRI overestimates chronic lesion size by almost a factor of three and that the chronic LGE-MRI is an excellent predictor of pathology-determined lesion size both in terms of depth and volume.…”

“…In that study, no CF data was shown for Cryo ablation as CF has little relevance for Cryo lesions. 9) On the other hand, higher CF is related to larger lesion size in RF ablation but there have been no data to date on how to make a durable scar while minimizing the acute edema relative to the lesion size. 10) The main results obtained from this study are as follows: The primary predictor of ventricular lesions with relatively larger edema was the relatively smaller CF and FTI.…”

“…10) Edema has always been known to be associated with RF ablation but only in recent studies has the creation of extensive edema as seen in acute MRI been quantified. [7][8][9]12) In this study, we looked at the various ablation parameters and compared their relationship to creating chronic lesions minimizing the associated acute edema relative to the chronic lesion size. We found that for powers ranging from 25 W to 40 W the biggest predictor of creating durable lesions without overwhelming edema was the greater CF and FTI.…”

“…Ablated lesions were defined using a pixel intensity threshold algorithm as described in previous reports. 9) Normal and ablated tissues were distinguished based on a bimodal distribution of pixel intensities and ablated lesions were defined at three standard deviations above the normal mean tissue pixel in-tensity in LGE-MR imaging. The acute lesion in LGE-MRI is characterized with a hypo-intense region in the middle, encircled with a ring of enhancement.…”

Evidence of Acute Tissue Edema after Cryoballoon Ablation for Atrial Fibrillation

“…In their paper, they showed that acute edema by cryoablation was significantly smaller than that by RFA. 11) The relationship between the atrial edema and AF recurrence might be less in CBA compared with RFA. Further evidence is needed to clarify this point.…”